Engine and saddle-type vehicle including the engine

Abstract

The invention includes an engine and a saddle-type vehicle including the engine, in which a power unit (6) includes an engine (6A). The engine (6A) includes a crankshaft (61). Further, the engine (6A) includes a crankcase (62) that houses the crankshaft (61). A dynamic damper (200) is provided in the crankcase (62). The dynamic damper (200) includes a damper block (210) and a support member (220). The support member (220) includes an elastomer and supports the damper block (210) at the crankcase (61). During operation of the engine (6A), bending vibration is generated in the crankshaft (61). At this time, the damper block (210) vibrates in a straight line that is orthogonal to a central axis of the crankshaft (61) and parallel to a direction in which the bending vibration is generated in the crankshaft (61).

Description

Technical Field

[0001] This invention relates to engines and saddle-type vehicles including engines. Background Technology

[0002] During engine operation, vibrations generated in the crankshaft are transmitted to the crankcase, causing noise in the power unit and other components, including the crankcase. To reduce this noise, JP 2002-005235 A proposes a structure for preventing crankshaft vibration. In this vibration-damping structure, a dynamic damper is installed at the end of the crankshaft.

[0003] More specifically, in the engine described in JP 2002-005235 A, a centrifugal oil filter is attached to one end of the crankshaft extending in one direction. A dynamic damper is attached to the oil filter via a cup-shaped attachment plate. The dynamic damper consists of an annular elastomer and an annular damping weight, and is configured to be integrated with the attachment plate by baking the elastomer onto the attachment plate.

[0004] Furthermore, in the aforementioned dynamic damper, the vibration resistance of the damping weight is set considering the fact that the crankcase stiffness varies with direction. Setting the vibration resistance of the damping weight requires consideration not only of the ratio of the damping weight's mass to the crankshaft mass and the composition of the elastic body, but also of the arrangement of the surrounding components of the damping weight and the allowable dimensions of the damping weight. Therefore, it is not easy to install a dynamic damper at a high-speed rotating crankshaft and appropriately set its vibration resistance. Consequently, it is not easy to manufacture the aforementioned engine.

[0005] Furthermore, in the engine described in JP 2002-005235 A, vibrations reduced by a dynamic damper are transmitted from the crankshaft to the crankcase. The stiffness of the crankcase is defined based on its shape and dimensions. That is, the stiffness of various crankcases installed in different engines may not necessarily have a common directional characteristic. Therefore, depending on the crankcase construction, vibrations reduced by the dynamic damper may be transmitted to the crankcase, and thus excessive noise may be generated from the power unit, including the crankcase, etc. Summary of the Invention

[0006] One object of the present invention is to provide an engine that can be easily manufactured and whose noise generation can be reduced, as well as a saddle-type vehicle including the engine. According to the invention, this object is achieved by the engine described later.

[0007] (1) An engine according to one aspect includes: a crankshaft; a crankcase housing the crankshaft; and a dynamic damper disposed at the crankcase, wherein the dynamic damper includes a damping block and a support member including an elastomer, and the damping block is vibratoryly supported at the crankcase such that the damping block can vibrate along a straight line via the elastomer, the straight line being orthogonal to the central axis of the crankshaft and parallel to the direction of bending vibration generated in the crankshaft.

[0008] In the engine, a dynamic damper is disposed in the crankcase. In this case, since it is not necessary to place the dynamic damper at the high-speed rotating crankshaft, the design and attachment freedom of the dynamic damper is increased, and the engine can be easily manufactured. Furthermore, using the above-described structure, the damping block of the dynamic damper vibrates in a straight line parallel to the direction of the crankshaft's bending vibration. Therefore, the vibration transmitted to the peripheral components of the crankshaft due to the crankshaft's bending vibration is effectively absorbed by the dynamic damper. Consequently, at least a portion of the vibrations that cause noise generated from the power unit, including the crankcase and its peripheral components, is effectively absorbed by the dynamic damper. As a result, an engine that is easy to manufacture and generates less noise is achieved.

[0009] (2) The support can vibrately support the damping block at the crankcase, so that the elastic force of the elastic body is applied to the damping block in a straight line. At the same time, the support restricts the vibration direction of the damping block, so that the damping block cannot vibrate on another straight line intersecting the straight line.

[0010] Based on the above construction, the damping block of the dynamic damper vibrates only along a straight line parallel to the direction of the crankshaft's bending vibration. Therefore, vibrations that cause noise are absorbed more effectively.

[0011] (3) The support may include a first leaf spring portion and a second leaf spring portion as elastic bodies, the first leaf spring portion and the second leaf spring portion being disposed at the crankcase and arranged at intervals from each other in a direction parallel to a straight line, and each of the first leaf spring portion and the second leaf spring portion being configured to connect the crankcase and the damping block to each other.

[0012] Leaf springs have a thickness smaller than other elastic components such as coil springs and rubber components. Therefore, with the above-described construction, the vibration direction of the damping block relative to the crankcase can be limited without requiring additional installation space.

[0013] (4) Each of the first leaf spring and the second leaf spring can be formed as a flat plate having one surface and another surface facing opposite directions to each other, and can be disposed on the crankcase such that one surface and the other surface are orthogonal to a straight line. In this case, each of the first leaf spring and the second leaf spring is bent in a plane orthogonal to the central axis of the crankshaft, such that the damping block vibrates in a straight line with a simple construction.

[0014] (5) The crankcase may have an attachment surface orthogonal to the central axis of the crankshaft, the support may include a first part and a second part attached to the attachment surface, and when viewed in a direction extending along the central axis of the crankshaft, the crankshaft may be located in the region between the portion of the first part of the support attached to the attachment surface and the portion of the second part of the support attached to the attachment surface.

[0015] In this configuration, when viewed along the direction extending from the crankshaft's central axis, the damping block can be positioned near the crankshaft. For example, the damping block can be arranged to overlap with the crankshaft. Therefore, compared to a position where the damping block is positioned significantly off-center from the crankshaft, instability in the engine's center of gravity caused by the damping block's vibration is suppressed.

[0016] (6) The dynamic damper may also include a rubber member disposed between the attachment surface of the crankcase and the damping block. In this case, the rubber member absorbs the vibration of the damping block caused by the elastic force of the first leaf spring and the second leaf spring. Therefore, noise generated by the strong vibration of the damping block is suppressed.

[0017] (7) The engine may also include a bearing that supports the crankshaft in a crankcase, wherein the crankcase may include a mounting portion for securing the bearing, and a dynamic damper may be attached to the mounting portion.

[0018] The crankcase is fixed and supports the crankshaft via bearings. Therefore, vibrations are easily transmitted from the crankshaft to the fixed portion. According to this configuration, since the dynamic damper is attached to the fixed portion, most of the vibrations transmitted from the crankshaft to the crankcase are effectively absorbed by the dynamic damper.

[0019] (8) According to another aspect, the saddle-type vehicle includes: a body that includes drive wheels; and the aforementioned engine configured to generate power to rotate the drive wheels.

[0020] The saddle-type vehicle includes the aforementioned engine. This facilitates the manufacture of saddle-type vehicles. Furthermore, at least a portion of the vibrations that cause noise from the power unit, including the crankcase and its surrounding components, is effectively absorbed by the dynamic damper. As a result, a saddle-type vehicle that is easy to manufacture and generates reduced noise is achieved.

[0021] Other features, elements, characteristics, and advantages of the invention will become more apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a right view of an autonomous two-wheeled vehicle according to a preferred embodiment; Figure 2 When viewed from the right side of the autonomous two-wheeled vehicle Figure 1 Side view of the power unit; Figure 3 It is used for explanation Figure 2 A view of the bending vibrations generated in the crankshaft; Figure 4 It is used for explanation Figure 2 An exploded three-dimensional view of the structure of the crankcase and dynamic damper; Figure 5 yes Figure 4 A partially enlarged side view of the right box-shaped component; Figure 6 This is a view showing the inner surface of the damping block; Figure 7 yes Figure 4 Front view of the supporting components; Figure 8 When viewed from the first direction Figure 7 Side view of the supporting components; Figure 9 When viewed from the second direction Figure 7 Side view of the supporting components; Figure 10 It is the section AA along the line. Figure 2 A cross-sectional view of the power unit; Figure 11 It was taken from BB along the line. Figure 2 A cross-sectional view of the power unit; Figure 12 This is a schematic diagram illustrating the operation of a dynamic damper when vibrations transmitted from the crankshaft to the crankcase are absorbed; and Figure 13 This is a schematic diagram illustrating the operation of a dynamic damper when vibrations transmitted from the crankshaft to the crankcase are absorbed. Detailed Implementation

[0023] The engine and a saddle-riding vehicle including the engine, according to a preferred embodiment, will now be described with reference to the accompanying drawings. An autonomous two-wheeled vehicle will be described as an example of a saddle-riding vehicle.

[0024] <1> A rough outline of the structure of an autonomous two-wheeled vehicle Figure 1 This is a right-side view of an autonomous two-wheeled vehicle according to a preferred embodiment. Figure 1 The image shows an autonomous two-wheeled vehicle 100 standing upright perpendicular to the road surface. Figure 1 The autonomous two-wheeled vehicle 100 includes a metal frame 1. The frame 1 includes a head tube 11 and multiple frame components. Figure 1 The image shows two frame members 12 and 13, among a plurality of frame members. The head tube 11 is located at the front of the vehicle. Frame members 12 and 13 are arranged to extend from the head tube 11 toward the rear of the vehicle.

[0025] The front fork 2 is located at the head tube 11 and is able to rotate about the central axis of the head tube 11. The front wheel 3 is rotatably supported on the lower end of the front fork 2. The handlebar 4 is located on the upper end of the front fork 2.

[0026] The vehicle frame 1 supports multiple components of the automatic two-wheeled vehicle 100, including a seat 5, a power unit 6, and a rear arm 7. The seat 5 is positioned approximately at the upper center of the automatic two-wheeled vehicle 100 in the longitudinal direction. The power unit 6 includes an engine 6A and is positioned approximately at the lower center of the automatic two-wheeled vehicle 100 in the longitudinal direction. Resin side covers are configured to clamp the front half of the power unit 6 (the portion of the engine 6A) in the lateral direction of the automatic two-wheeled vehicle 100.

[0027] The rear arm 7 is configured to extend rearward from a position near the rear end of the power unit 6. The rear arm 7 is supported on the vehicle frame 1 by a pivot (not shown). The rear wheel 8 is rotatably supported on the rear end of the rear arm 7. The rear wheel 8 rotates as a drive wheel by power generated by the engine 6A of the power unit 6.

[0028] During operation of the engine 6A, the automatic two-wheeled vehicle 100 generates noise as the crankshaft 61 included in the engine 6A rotates. Therefore, in the power unit 6 according to this embodiment, the dynamic damper 200 is configured to reduce the noise generated during engine operation. The noise-generating mechanism and the specific construction and function of the dynamic damper 200 will be described.

[0029] <2> Basic structure of power unit 6 and bending vibration of crankshaft Figure 2 When viewed from the right side of the autonomous two-wheeled vehicle Figure 1 A side view of the power unit 6. As described above, the power unit 6 includes an engine 6A. The engine 6A includes a cylinder head 63. The cylinder head 63 has a configuration in which two cylinders are arranged in the left-right direction along the automatic two-wheeled vehicle 100. Figure 2 In the diagram, the outline of the cylinder head 63 is schematically shown by a single-dotted line.

[0030] The power unit 6 includes a crankcase 62. According to this embodiment, the crankcase 62 houses a crankshaft 61. The crankshaft 61 extends within the crankcase 62 in the left-right direction of the automatic two-wheeled vehicle 100.

[0031] Two pistons 64 are connected to the crankshaft 61 via two connecting rods 65. The two pistons 64 on the crankshaft 61 are configured to reciprocate within two cylinders of the cylinder head 63. Figure 2 In the cylinder head 63, the right piston 64 and right connecting rod 65 are indicated by solid lines. Further, in... Figure 2In the middle, the imaginary straight line passing through the central axis of the right cylinder of the cylinder head 63 is indicated by a double-dotted line as the cylinder axis AS.

[0032] During the operation of engine 6A, bending vibrations occur in crankshaft 61. Figure 3 It is used to explain in Figure 2 A view of the bending vibrations generated in crankshaft 61. Figure 3 In the middle, it is shown that when along Figure 2 The hollow arrow VP1 indicates the shape of the power unit 6 when viewed from above. Furthermore, in... Figure 3 In the diagram, the crankshaft 61, two pistons 64, and two connecting rods 65, all located in the power unit 6, are indicated by solid lines. Further, in... Figure 3 In the middle, the imaginary straight line passing through the central axis of crankshaft 61 is indicated by a double-dotted line as crankshaft axis 61c. Figure 2 The direction of the hollow arrow VP1 is the direction that is orthogonal to the cylinder axis AS when the power unit 6 is viewed from the direction extending along the central axis (crankshaft axis 61c) of the crankshaft 61.

[0033] When the crankshaft 61 rotates during the operation of the engine 6A, the two pistons 64 connected to the crankshaft 61 reciprocate along the cylinder axis AS. In this situation, the pressure and inertial force of the fuel-air mixture applied to each piston 64 generate a bending moment in the crankshaft 61 within a predetermined cycle. Therefore, as... Figure 3 As indicated by the thick dashed line, in the crankshaft 61, its central portion bends repeatedly in the direction toward the cylinder head 63 and then in the direction away from the cylinder head 63.

[0034] As a result, in this example, such as Figure 2 and Figure 3 As indicated by the thick solid arrow, crankshaft 61 vibrates relative to cylinder head 63 in a plane parallel to the two cylinder axes AS of cylinder head 63 and the left-right direction of the automatic two-wheeled vehicle 100. This vibration is a bending vibration of crankshaft 61. Here, the direction of the bending vibration of crankshaft 61 is the direction in which crankshaft 61 vibrates due to the bending moment generated by crankshaft 61 during engine 6A operation. In this example, the direction of the bending vibration of crankshaft 61 is parallel to the cylinder axis AS in the side view and orthogonal to the central axis (crankshaft axis 61c) of crankshaft 61 in the top view.

[0035] When bending vibrations of the crankshaft 61, having a specific frequency (e.g., within a specific range of 800 Hz), are transmitted to a portion of the crankcase 62, noise may be generated due to the vibration of that portion of the crankcase 62. For example, when a portion of the outer surface of the crankcase 62 is repeatedly deformed into concave and convex shapes due to the bending vibrations of the crankshaft 61, significant noise is likely to be generated. Alternatively, when bending vibrations of the crankshaft 61, having a specific frequency, are transmitted through the crankcase 62 to a portion of the frame members 12, 13, noise may be generated due to the vibration of that portion of the frame members 12, 13. Furthermore, noise may be generated due to the vibration of side covers, etc., attached to the frame members 12, 13. Therefore, in the automatic two-wheeled vehicle 100 according to this embodiment, a dynamic damper 200 is provided in the crankcase 62 to effectively reduce vibrations transmitted from the crankshaft 61 to other components such as the crankcase 62.

[0036] <3> Crankcase 62 and dynamic damper 200 (1) A summary of the construction of the crankcase 62 and the dynamic damper 200 Figure 4 It is used for explanation Figure 2 An exploded perspective view of the structure of the crankcase 62 and the dynamic damper 200. Figure 2 The crankcase 62 is composed of multiple housing components. The dynamic damper 200 is attached to the housing component facing the right of the automatic two-wheeler 100 (hereinafter referred to as the right housing component 62R) among the multiple housing components of the crankcase 62.

[0037] (2) Right housing component 62R of crankcase 62 Figure 5 yes Figure 4 A partially enlarged side view of the right box component 62R. (See attached image.) Figure 5 As shown, a bearing fixing part 66 is provided at the right housing member 62R. A bearing opening 67 is formed in the center of the bearing fixing part 66. The bearing opening 67 is a circular opening that allows the right end of the crankshaft 61 to be inserted.

[0038] The bearing retaining portion 66 includes an annular bearing fitting portion 69 on the inner edge and periphery of the bearing opening 67. The bearing fitting portion 69 is formed such that the bearing BR (described later) Figure 10 It can be fitted from the inside of the crankcase 62 into the bearing fitting portion 69. Furthermore, the bearing fixing portion 66 has a generally annular flat attachment surface 66s that surrounds the bearing opening 67 and the bearing fitting portion 69 and faces to the right of the automatic two-wheeled vehicle 100.

[0039] Four threaded holes h31, opening to the right side of the automatic two-wheeled vehicle 100, are formed in the bearing fixing part 66. The four threaded holes h31 are arranged at equal angular intervals around the center of the bearing opening 67, so as to surround the bearing opening 67 and the bearing fitting part 69.

[0040] When the dynamic damper 200 is attached to the right housing member 62R, as described later... Figure 4 The rubber component 230 is provided in the bearing mating part 69 as shown. Figure 5 The surface facing right is indicated by the thick dashed line. Further, as... Figure 5 As indicated by the thick dashed line, a feature described later is provided near the outer periphery of the attachment surface 66s. Figure 4 Rubber component 240. Further, as described later. Figure 4 The four screws sc2 are attached to the four threaded holes h31.

[0041] (3) Construction of each component of the dynamic damper 200 like Figure 4 As shown, the dynamic damper 200 includes a damping block 210, a support member (support element) 220, and rubber members 230 and 240. (First) Rubber member 230 is an annular member such as an O-ring, and has an inner diameter and an outer diameter corresponding to the bearing fitting portion 69 of the right housing member 62R. (Second) Rubber member 240 is an annular member made of rubber such as an O-ring, and has an inner diameter larger than the inner diameter of rubber member 230 and an outer diameter slightly smaller than the outer diameter of the attachment surface 66s of the right housing member 62R. The functions of rubber members 230 and 240 will be described below.

[0042] The damping block 210 is a generally disc-shaped component made of a metal such as aluminum or stainless steel. The outer diameter of the damping block 210 is equal to or slightly larger than the outer diameter of the rubber component 240. One surface of the damping block 210 facing opposite directions is referred to as the outer surface 211 and the inner surface 212 of the damping block 210, respectively.

[0043] When the dynamic damper 200 is attached to the right housing member 62R, the outer surface 211 of the damping block 210 faces the direction opposite to the right housing member 62R (to the right). Furthermore, the outer surface 211 of the damping block 210 is formed to gradually expand from the outer peripheral end to the center of the damping block 210. On the other hand, when the dynamic damper 200 is attached to the right housing member 62R, the inner surface 212 of the damping block 210 faces the attachment surface 66s of the right housing member 62R.

[0044] Figure 6 This is a view showing the inner surface 212 of the damping block 210. (See image.) Figure 6As shown, a circular recess 212a is formed at the center of the inner surface 212 of the damping block 210. Further, an annular closure portion r1 is formed surrounding the recess 212a. The recess 212a has a... Figure 5 The bearing opening 67 of the right housing component 62R has the same or approximately the same inner diameter.

[0045] The recess 212a is formed to accommodate the right end of the crankshaft 61 protruding to the right from the right housing member 62R when the dynamic damper 200 is attached to the right housing member 62R, as described below. The annular closure r1 includes a fitting... Figure 4 A portion of the rubber component 230 has an annular groove, and has a... Figure 5 The inner and outer diameters of the bearing fitting portion 69 of the right housing component 62R. When the dynamic damper 200 is attached to the right housing component 62R. Figure 4 The rubber component 230 is configured to overlap with the annular groove of the annular closure portion r1.

[0046] Two recesses 212b are formed in the inner surface 212 of the damping block 210 to sandwich the recess 212a and the annular closure r1 therebetween. Each of the two recesses 212b extends in a straight line and is configured to accommodate... Figure 4 The supporting member 220, the leaf spring part (elastic body) 223 (described later) Figure 7 Part of ).

[0047] An annular closure portion r2 is formed in the inner surface 212 of the damping block 210, in a region having a certain width and including the outer peripheral end of the damping block 210. The annular closure portion r2 includes features that allow... Figure 4 A portion of the rubber component 240 is fitted into the annular groove thereon. When the dynamic damper 200 is attached to the right housing component 62R... Figure 4 The rubber component 240 is configured to overlap with the annular groove of the annular closure portion r2.

[0048] In the inner surface 212 of the damping block 210, two supported surfaces 212c are formed in the area other than the region between the two recessed portions 212b and the annular closure portion r2. Figure 6 In the diagram, two supported surfaces 212c are indicated by a single-dotted line. One supported surface 212c is formed outside the recess 212a and at a position between a recessed portion 212b and a portion (arc-shaped portion) of the annular closure r2. The other supported surface 212c is formed outside the recess 212a and at a position between another recessed portion 212b and another portion (arc-shaped portion) of the annular closure r2. Both supported surfaces 212c are formed flat. When the dynamic damper 200 is attached to the right housing member 62R, Figure 4The connecting part 222 of the two damping blocks of the support member 220 described later. Figure 7 They respectively abut against the two supported surfaces 212c. In Figure 6 In this process, a dot pattern is applied to the connection portion 222 between the two supported surfaces 212c and the two damping blocks described later. Figure 7 The parts that are adjacent to each other.

[0049] The damping block 210 has eight through holes extending from the outer surface 211 to the inner surface 212. Four of the eight through holes h22 are arranged at equal angular intervals around the center of the recess 212a, surrounding the recess 212a and the annular closure r1 in the region between the two recessed portions 212b. These four through holes h22 correspond to the four threaded holes h31 of the right housing member 62R. Figure 5 ), and have a common inner diameter, the four screws sc2 (described later) Figure 4 Each integral screw sc2 (including the head) in the ) can be inserted into the common inner diameter.

[0050] The remaining four of the eight through holes are four threaded holes h21. The four threaded holes h21 have a common inner diameter and a common inner circumferential surface shape. Two threaded holes h21 are formed in each of the two supported surfaces 212c. The four threaded holes h21 are used to... Figure 4 The support member 220 is screwed onto the inner surface 212 of the damping block 210. The four threaded holes h21 do not need to penetrate the outer surface 211 and the inner surface 212 of the damping block 210. The four threaded holes h21 can be opened only on the inner surface 212.

[0051] As described above, in the dynamic damper 200, the support member 220 is attached to the inner surface 212 of the damping block 210. In this example, in Figure 4 In the support member 220, the surface facing the inner surface 212 of the damping block 210 is the front surface of the support member 220.

[0052] Figure 7 yes Figure 4 The front view of the support member 220. Here, regarding the support member 220, in the front view of the support member 220, Figure 7 The direction indicated by arrow D1 is defined as the first direction D1, and... Figure 7 The direction indicated by arrow D2 is defined as the second direction D2. The first direction D1 and the second direction D2 are orthogonal to each other. Further, Figure 7 The direction indicated by arrow D3, which is orthogonal to the first direction D1 and the second direction D2, is defined as the third direction D3. Figure 8 When observing along the first direction D1 Figure 7 A side view of the support member 220, and Figure 9 When observing along the second direction D2 Figure 7 Side view of the support member 220.

[0053] The support member 220 is composed of a single metal component, manufactured through bending, heat treatment, and other processes involving metal plates cut to a predetermined shape. For example... Figure 7 As shown, the support member 220 is roughly ring-shaped in the front view and is mainly composed of two box-shaped connecting parts 221, two damping block connecting parts 222, and two leaf spring parts 223.

[0054] In the front view of the support member 220, two housing connection portions 221 are arranged spaced apart from each other in a first direction D1 and extend in a second direction D2. Each housing connection portion 221 has one surface and another surface orthogonal to a third direction D3. Further, two through holes h12 are formed in each housing connection portion 221. The four through holes h12 of the two housing connection portions 221 correspond to the four threaded holes h31 of the right housing member 62R. Figure 5 The inner diameter of each through hole h12 is larger than the outer diameter of the shaft portion of the screw sc2 attached to each threaded hole h31 and smaller than the outer diameter of the head of the screw sc2. Figure 4 ).

[0055] In the front view of the support member 220, two damping block connection portions 222 are arranged spaced apart from each other in the second direction D2 and extend in the first direction D1. Each damping block connection portion 222 has one surface and another surface orthogonal to the third direction D3. Further, two through holes h11 are formed in each damping block connection portion 222. The four through holes h11 of the two damping block connection portions 222 correspond to the four threaded holes h21 of the damping block 210, respectively. Figure 6 The inner diameter of each through hole h11 is greater than the outer diameter of the shaft portion of the screw sc1 attached to each threaded hole h21 and smaller than the outer diameter of the head of the screw sc1.

[0056] In the front view of the support member 220, two leaf spring portions 223 are formed to connect the two ends of the two housing connecting portions 221, respectively. Further, the two leaf spring portions 223 are configured to hold the two damping block connecting portions 222 in a position between the two housing connecting portions 221 in a first direction D1. The two damping block connecting portions 222 are held in a position slightly offset from the two housing connecting portions 221 in a third direction D3.

[0057] like Figure 8 As shown, each leaf spring portion 223 is configured to be bent at 90° relative to the housing connection portion 221 and the damping block connection portion 222. Therefore, each leaf spring portion 223 has one surface and another surface orthogonal to the second direction D2.

[0058] like Figure 9 As shown, the leaf spring portion 223 includes a first portion 223a, a second portion 223b, and a third portion 223c arranged along a first direction D1. The first portion 223a and the third portion 223c of the leaf spring portion 223 are directly connected to the two housing connecting portions 221, respectively. Further, the second portion 223b of the leaf spring portion 223 is directly connected to a damping block connecting portion 222 at a position between the first portion 223a and the third portion 223c along the first direction D1. With this configuration, for example, when the two housing connecting portions 221 are fixed, and a force is applied to the damping block connecting portion 222 in the second direction D2, the second portion 223b of the leaf spring portion 223 partially bends due to elasticity. Therefore, the damping block connecting portion 222 moves relative to the two housing connecting portions 221 in the second direction D2.

[0059] (4) Attachment of dynamic damper 200 to crankcase 62 Figure 10 It is along Figure 2 A cross-sectional view taken along line AA of the power unit 6, and Figure 11 It is along Figure 2 A cross-sectional view taken along line BB of the power unit 6. As described below, the dynamic damper 200 is attached to the crankcase 62. Figure 10 and Figure 11 As shown, at the point at which the dynamic damper 200 is initially attached to the crankcase 62, the bearing BR engages with the bearing engagement portion 69 of the right housing member 62R. Furthermore, a portion near the right end of the crankshaft 61 is rotatably held at the right housing member 62R. Further, the right end of the crankshaft 61 protrudes slightly outward (to the right) from the bearing fixing portion 66 through the bearing opening 67.

[0060] First, the support member 220 is positioned on the inner surface 212 of the damping block 210, so that... Figure 7 The two leaf spring sections 223 are housed in Figure 6 In the two recessed portions 212b and Figure 7 The four through holes h21 and Figure 6 The four threaded holes h21 overlap. In this state, as... Figure 4 As indicated by the dashed arrows, four screws sc1 are attached to the four threaded holes h21 of the damping block 210 through the four through holes h11 of the support member 220. Therefore, as... Figure 10 As shown, the two damping block connection parts 222 of the support member 220 ( Figure 7 ) connected to the two supported surfaces 212c of the damping block 210 Figure 6 In this case, the two box-shaped connecting parts 221 of the support member 220 ( Figure 7 The four through holes h12 are positioned such that they are opposite to the four through holes h22 of the damping block 210, while the two box-shaped connecting parts 221 of the support member 220 are spaced apart from the inner surface 212 of the damping block 210.

[0061] Next, the rubber component 230 is positioned on the right-facing surface of the bearing fitting portion 69 of the right housing component 62R. Further, the rubber component 240 is positioned near the outer peripheral end of the attachment surface 66s of the right housing component 62R. In this state, the damping block 210 is positioned on the attachment surface 66s of the right housing component 62R such that the rubber component 230 overlaps with the annular closure portion r1, and the rubber component 240 overlaps with the annular closure portion r2. Further, the damping block 210 is positioned on the attachment surface 66s of the right housing component 62R such that the four through holes h22 ( Figure 6 ) and the four threaded holes h31 of the right box component 62R ( Figure 5 )overlapping.

[0062] After that, as Figure 4 As indicated by the thick dashed arrow, four screws sc2 are attached to the four threaded holes h31 of the right housing member 62R by passing through the four through holes h22 of the damping block 210 and the four through holes h12 of the support member 220, respectively. Therefore, as Figure 11 As shown, the two box-shaped connecting parts 221 of the support member 220 ( Figure 7 ) is attached to the attachment surface 66s of the right housing member 62R. Figure 5 In this manner, the dynamic damper 200 is attached to the bearing mounting portion 66 of the right housing component 62R.

[0063] With the dynamic damper 200 attached to the crankcase 62, the right end of the crankshaft 61, protruding from the bearing opening 67 of the bearing fixing portion 66, is accommodated in the recess 212a of the damping block 210. A rubber member 230 is disposed between the annular closing portion r1 of the damping block 210 and the bearing fitting portion 69 of the right housing member 62R. Therefore, the space around the right end of the crankshaft 61, surrounded by the damping block 210 and the right housing member 62R, is enclosed by the rubber member 230 relative to the space outside the power unit 6. Furthermore, a rubber member 240 is further disposed between the attachment surfaces 66s of the damping block 210 and the right housing member 62R to surround the rubber member 230. With this configuration, in the power unit 6 of this example, oil supplied to the right end of the crankshaft 61 is prevented from leaking from inside the crankcase 62 through the attachment portion of the dynamic damper 200.

[0064] (5) Operation of dynamic damper 200 The aforementioned dynamic damper 200 is attached to the crankcase 62 to absorb at least a portion of the vibrations transmitted from the crankshaft 61 to the crankcase 62. The operation of the dynamic damper 200 at this time will be described.

[0065] Figure 12 and Figure 13 This is a schematic diagram illustrating the operation of the dynamic damper 200 when it absorbs vibrations transmitted from the crankshaft 61 to the crankcase 62. Figure 12 This is a schematic diagram of the dynamic damper 200 as viewed from a position opposite to the outer surface 211 of the damping block 210. Figure 13 It was through Figure 12 The center of the dynamic damper 200 Figure 12 A cross-sectional view of the dynamic damper 200. Figure 12 and Figure 13 To facilitate understanding of the operation of the dynamic damper 200, some of its constituent elements are not shown. Furthermore, the dimensions of the various components in the dynamic damper 200 are different.

[0066] like Figure 12 and Figure 13 The dashed line in the diagram indicates the definition of an imaginary straight line VL1 that is parallel to the direction of the bending vibration of the crankshaft 61 and orthogonal to the crankshaft axis (central axis of the crankshaft) 61c. In this case, the two leaf spring portions 223 of the support member 220 are configured such that one and the other surfaces are orthogonal to the imaginary straight line VL1. Therefore, the direction in which the leaf spring portions 223 can deform is limited to a plane that is substantially parallel to the crankshaft axis 61c and the imaginary straight line VL1. Further, as... Figure 12 As shown, the support member 220 is attached to the attachment surface 66c such that when viewed in a direction extending along the crankshaft axis 61c, the two damping block connections 222 are spaced apart from each other on an imaginary straight line VL1.

[0067] In these cases, the direction in which the damping block 210 can move is limited by the two damping block connecting portions 222 and the two leaf spring portions 223 to the direction extending along the imaginary straight line VL1. Therefore, as... Figure 12 and Figure 13 As indicated by the thick solid arrow, when the crankshaft 61 produces bending vibration, the damping block 210 vibrates along the imaginary straight line VL1 and does not vibrate in a direction deviating from the imaginary straight line VL1. Therefore, at least a portion of the bending vibration generated in the crankshaft 61 is effectively absorbed by the vibration of the damping block 210.

[0068] Furthermore, the support member 220 is attached to the attachment surface 66s such that, when viewed in the direction extending along the crankshaft axis 61c, the crankshaft 61 is located between the two damping block connections 222. Furthermore, the support member 220 is attached to the attachment surface 66s such that, when viewed in the direction extending along the crankshaft axis 61c, the crankshaft 61 is located between the two housing connections 221.

[0069] With this configuration, when viewed in the direction extending along the crankshaft axis 61c, the damping block 210 overlaps at least with the crankshaft 61 on the imaginary straight line VL. Therefore, compared to a situation where the damping block 210 is positioned significantly off from the crankshaft 61 when viewed in the direction extending along the crankshaft axis 61c, the instability of the engine 6A's center of gravity caused by the vibration of the damping block 210 is suppressed.

[0070] The vibration frequency that the dynamic damper 200 can attenuate is a characteristic value, and this characteristic value is primarily defined based on the weight of the damping block 210 and the elasticity of the leaf spring 223. Therefore, preferably, the weight of the damping block 210 and the elasticity of the leaf spring 223 are limited such that the vibration frequency that the dynamic damper 200 can attenuate is pre-matched to a specific frequency band. This specific frequency band is the band that contributes significantly to the higher levels of noise generated from the automatic two-wheeler 100 during engine 6A operation. Preferably, the weight of the damping block 210 and the elasticity of the leaf spring 223 are set, for example, through experimentation or simulation, and the specific frequency band is selected.

[0071] <4> Effect (1) In the power unit 6 according to this embodiment, the dynamic damper 200 is disposed in the crankcase 62. In this case, since it is not necessary to directly dispose of the dynamic damper 200 on the high-speed rotating crankshaft 61, the design and attachment freedom of the dynamic damper 200 is increased, and the power unit 6 is easier to manufacture. Furthermore, with the above configuration, the damping block 210 of the dynamic damper 200 vibrates on an imaginary straight line VL1 parallel to the direction of the bending vibration of the crankshaft 61. Therefore, the vibration transmitted to the peripheral components of the crankshaft 61 due to the bending vibration of the crankshaft 61 is effectively absorbed by the dynamic damper 200. Thus, the vibration of the crankcase 62 and its peripheral components due to the bending vibration of the crankshaft 61 is effectively reduced. Alternatively, the vibration of at least a portion of the frame components 12 and 13 due to the bending vibration of the crankshaft 61 is effectively reduced. As a result, a power unit 6 that is easy to manufacture and reduces the generation of noise due to the bending vibration of the crankshaft 61 can be realized.

[0072] (2) The dynamic damper 200 according to the above embodiment includes rubber members 230 and 240 disposed between the attachment surface 66s of the right housing member 62R and the damping block 210. In this case, as described above, each rubber member 230 and 240 serves as a sealing member to prevent oil in the crankcase 62 from leaking from the attachment portion of the dynamic damper 200. Furthermore, when the rubber members 230 and 240 generate bending vibrations in the crankshaft 61, they absorb part of the vibration of the damping block 210. Therefore, noise generated due to excessive vibration of the damping block 210 is suppressed.

[0073] <5> Example As a preferred example, the power unit is manufactured having the same structure as the power unit 6 according to the above embodiment. Further, as a comparative example, the power unit is manufactured having the same structure as the power unit 6 according to the above embodiment, except that it does not include the dynamic damper 200 described above.

[0074] Furthermore, regarding the power unit of the preferred example and the power unit of the comparative example, the engine was operated under predetermined common conditions, and the magnitude of the noise generated during this operation, having wavelengths within a specific range, was measured. As a result, it was confirmed that the noise level generated from the power unit of the preferred example was lower than the noise level generated from the power unit of the comparative example.

[0075] <6> Other embodiments (1) In the power unit 6 of the above embodiment, a dynamic damper 200 is provided in the portion of the right housing member 62R that covers the right end of the crankshaft 61, but this teaching is not limited thereto. The dynamic damper 200 may be provided in the portion of the right housing member 62R that is spaced apart from the crankshaft 61. For example, the dynamic damper 200 may be provided in any one of the front end, upper end, lower end, and rear end of the crankcase 62. Similarly, in these cases, since the vibration direction of the damping block 210 is restricted to the direction of the bending vibration of the crankshaft 61, an effect similar to that of the above embodiment can be obtained.

[0076] (2) Although a dynamic damper 200 is provided at the engine 6A in the power unit 6 according to the above embodiment, the teachings are not limited thereto. In the power unit 6, not only one dynamic damper 200 can be provided, but also two or three dynamic dampers 200 can be provided. For example, in the power unit 6 described above, a new dynamic damper 200 can be provided on the left side of the crankcase 62.

[0077] (3) In the dynamic damper 200 according to the above embodiment, in the side view of the automatic two-wheeled vehicle 100, the two leaf spring portions 223 of the support member 220 are arranged in the direction of the bending vibration of the crankshaft 61. Therefore, the vibration direction of the damping block 210 is restricted to a direction extending along an imaginary straight line VL1 parallel to the direction of the bending vibration of the crankshaft 61. However, according to this teaching, the vibration direction of the damping block 210 is not limited to the above example. The dynamic damper 200 may have the following configuration instead of the support member 220.

[0078] For example, in the aforementioned right housing member 62R, a guide shaft extending along an imaginary straight line VL1 is provided. Furthermore, a damping block 210 is provided on the guide shaft so that it can move in the direction extending along the guide shaft. Further, the damping block 210 is allowed to move along the guide shaft within a certain range, and an elastic body (e.g., a coil spring) is provided to support the damping block 210 at a portion of the guide shaft or a portion of the right housing member 62R. Even with this configuration in the crankcase 62, the vibration direction of the damping block 210 can be limited to the direction of the bending vibration of the crankshaft 61. Therefore, effects similar to those of the above embodiment can be obtained.

[0079] (4) Although the dynamic damper 200 according to the above embodiment includes two rubber members 230, 240, the teachings are not limited thereto. For example, in cases where oil leakage from the crankcase 62 to the outside of the power unit 6 is prevented by a construction other than the dynamic damper 200, the dynamic damper 200 need not include at least one of the two rubber members 230, 240.

[0080] (5) For example, there are also power units for saddle-type vehicles with a configuration in which the crankshaft and a plurality of power transmission components attached to the crankshaft are respectively housed in a plurality of housings integrally connected to each other. For example, there is a configuration in which the housing housing the crankshaft and the housing housing the belt-driven continuously variable transmission (CVT) attached to the crankshaft are integrally connected to each other. Alternatively, there is a configuration in which the housing housing the crankshaft and the housing housing the drive shaft attached to the crankshaft are integrally connected to each other. Alternatively, there is a configuration in which the housing housing the crankshaft and the housing housing the clutch attached to the crankshaft are integrally connected to each other. In such a configuration, the plurality of integrally connected housings can be regarded as crankcases according to the present teaching, and the dynamic damper according to the above embodiment can be provided in at least one of the plurality of housings. Similarly, in this case, since the plurality of housings constituting the power unit are integrally connected to each other, effects similar to those of the above embodiment can be obtained.

[0081] (6) Although in the dynamic damper 200 according to the above embodiment, the support member 220 supporting the damping block 210 at the right housing member 62R is composed of a single member including two leaf spring portions 223, the teachings are not limited thereto. As a construction for supporting the damping block 210 at the right housing member 62R, the support member 220 may be divided into two members such that the two leaf spring portions 223 are spaced apart from each other.

[0082] That is, the dynamic damper 200 may include two support members, which include two leaf spring members in place of the aforementioned support member 220. In this case, for example, a portion of the damping block 210 is supported by one leaf spring member at a portion of the right housing member 62R. Further, another portion of the damping block 210 is supported by another leaf spring member at another portion of the right housing member 62R. Further, the arrangement and orientation of the two leaf spring members are adjusted such that the vibration direction of the damping block 210 is parallel to the bending vibration direction of the crankshaft 61. Therefore, effects similar to those of the above embodiment can be obtained.

[0083] (7) In the dynamic damper 200 according to the above embodiment, a weight adjustment member for adjusting the weight of the damping block 210 can be attached to the damping block 210. In this case, for example, threaded holes for various weight members for screwing in the weight members can be formed in the damping block 210. Therefore, a weight member with the desired weight can be easily attached to or removed from the damping block 210.

[0084] (8) Although the engine 6A according to the above embodiment includes a cylinder head 63 and two cylinders arranged in the left-right direction of the automatic two-wheeled vehicle 100, the teachings are not limited thereto. The engine 6A may be configured to include only one cylinder or may be configured to include three, four or more cylinders. Further, the configuration of the engine 6A is not limited to the above examples, and the engine 6A may be configured such that one cylinder or three or more cylinders are arranged in the left-right direction of the automatic two-wheeled vehicle 100. Alternatively, the engine 6A may be configured such that one or more cylinders are arranged in the front-rear direction of the automatic two-wheeled vehicle 100. Further, the engine 6A may be configured such that four cylinders are arranged in a matrix in a top view, or may be configured such that multiple cylinders are arranged in a V-shape in a side view.

[0085] Although the direction of the bending vibration generated in the crankshaft 61 varies depending on the construction of the engine 6A, it can be derived based on the predetermined dimensions of each component. Thus, even if the number and arrangement of cylinders in the engine 6A differ from those in the examples of the above embodiments, the dynamic damper 200 can be attached to the crankcase 62 such that the damping block 210 vibrates in the direction of the bending vibration.

[0086] (9) Although the above embodiments are examples of applying the teachings to autonomous two-wheeled vehicles, the teachings are not limited thereto. The teachings can be applied to other saddle-mounted vehicles such as four-wheeled cars, motorized tricycles or ATVs (all-terrain vehicles).

[0087] In the above embodiments, crankshaft 61 is an example of a crankshaft, crankcase 62 is an example of a crankcase, dynamic damper 200 is an example of a dynamic damper, damping block 210 is an example of a damping block, imaginary straight line VL1 is an example of a straight line, support member 220 is an example of a support member, and power unit 6 and engine 6A are examples of engines.

[0088] Furthermore, the crankshaft axis 61c is an example of the central axis of the crankshaft, the attachment surface 66s of the right housing member 62R is an example of an attachment surface, one of the two leaf spring portions 223 is an example of a first leaf spring portion, the other leaf spring portion 223 of the two leaf spring portions 220 is an example of a second leaf spring portion, one of the two housing connection portions 221 of the support member 220 is an example of a first part, and the other housing connection portion 221 of the two housing connection portions 220 of the support member 220 is an example of a second part.

[0089] Furthermore, one surface and the other surface of each leaf spring portion 223 of the support member 220 are examples of one surface and the other surface of each of the first leaf spring portion and the second leaf spring portion facing opposite directions to each other; rubber members 230 and 240 are examples of rubber members; bearing BR is an example of a bearing; bearing fixing portion 66 of the right housing member 62R is an example of a fixing portion; rear wheel 8 is an example of a drive wheel; the entire automatic two-wheeled vehicle 100 except for the power unit 6 is an example of a main body; and the automatic two-wheeled vehicle 100 is an example of a saddle-mounted vehicle.

Claims

1. An engine comprising: Crankshaft; A crankcase that houses the crankshaft; and A dynamic damper, which is located at the crankcase, wherein The dynamic damper includes Damping block, and A support member includes at least one elastic body and vibratoryly supports the damping block at the crankcase, such that the damping block can vibrate along a straight line via the elastic body, the straight line being orthogonal to the central axis of the crankshaft and parallel to the direction of bending vibrations generated in the crankshaft. The support member vibratoryly supports the damping block at the crankcase, so that the elastic force of the elastic body is applied to the damping block along a straight line, while the support member restricts the vibration direction of the damping block, so that the damping block cannot vibrate on another straight line intersecting the first straight line.

2. The engine according to claim 1, wherein, The support member includes a first leaf spring portion and a second leaf spring portion, which serve as the elastic body. The first leaf spring portion and the second leaf spring portion are disposed at the crankcase and are arranged spaced apart from each other in a direction parallel to the straight line. Each of the first leaf spring and the second leaf spring is configured to connect the crankcase and the damping block to each other.

3. The engine of claim 2, wherein, Each of the first leaf spring portion and the second leaf spring portion is formed as a flat plate having one surface and another surface facing opposite directions to each other, and is disposed on the crankcase such that the one surface and the other surface are orthogonal to the straight line.

4. The engine of any one of claims 1 to 3, wherein, The crankcase has an attachment surface orthogonal to the central axis of the crankshaft.

5. The engine according to claim 4, wherein, The support includes a first portion and a second portion attached to the attachment surface, and When viewed along the direction extending along the central axis of the crankshaft, the crankshaft is located in the region between the portion of the first part of the support attached to the attachment surface and the portion of the second part of the support attached to the attachment surface.

6. The engine of claim 5, wherein, The dynamic damper further includes at least one rubber component disposed between the attachment surface of the crankcase and the damping block.

7. The engine of claim 6, wherein, The at least one rubber component includes a first rubber component and a second rubber component, wherein the first rubber component is a ring-shaped component and the second rubber component is a ring-shaped component made of rubber.

8. The engine of claim 7, wherein, The first rubber component is an O-ring, and the second rubber component is an O-ring.

9. The engine according to any one of claims 1 to 3 and 5 to 8, further comprising a bearing that supports the crankshaft within the crankcase, wherein... The crankcase includes a fixing part for securing the bearing, and The dynamic damper is attached to the fixed part.

10. The engine of claim 6, wherein, The at least one rubber component includes a first rubber component and a second rubber component. The first rubber component is a ring-shaped component. The second rubber component is a ring-shaped component made of rubber. The engine also includes bearings that support the crankshaft within the crankcase, the crankcase including a fixing portion for securing the bearings. The dynamic damper is attached to the fixed part. The first rubber component has an inner diameter and an outer diameter corresponding to the bearing fitting portion of the fixed part of the crankcase, and the second rubber component has an inner diameter larger than the inner diameter of the first rubber component and an outer diameter slightly smaller than the outer diameter of the attachment surface of the crankcase.

11. The engine of claim 10, wherein, The first rubber component is an O-ring, and the second rubber component is an O-ring.

12. A saddle-type vehicle, comprising: The main body includes drive wheels; and The engine according to any one of claims 1 to 11 is configured to generate power to rotate the drive wheel.

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