Clutch device

Abstract

To reduce the weight of a clutch device.SOLUTION: A clutch device 7 includes: a clutch outer 30 which is rotatably journalled to a driving force transmission shaft 20, and has an outer bottom 31 annularly formed coaxially with the driving force transmission shaft 20, and an outer cylinder 32 extending in an axial direction of the driving force transmission shaft 20 from an outer peripheral edge of the outer bottom 31; and a primary driven gear 50 which is annularly formed coaxially with the driving force transmission shaft 20 and is attached to the clutch outer 30 so that power from a power source can be input thereto. The outer bottom 31 has a gear attachment portion 37 which is inserted into the inside of the primary driven gear 50 and is fitted to the primary driven gear 50 in a relatively non-rotatable manner. The primary driven gear 50 is made of a first material. At least one of the outer bottom 31 and the outer cylinder 32 is made of a second material. The first material has strength higher than that of the second material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, research and development has been conducted into lightweighting, which contributes to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] A clutch device may be provided in the torque transmission path between a power source such as an engine and wheels. An example of such a clutch device is a multi-plate friction clutch. A multi-plate friction clutch includes a cylindrical clutch outer rotatably supported on an output shaft, a primary driven gear assembled to the clutch outer and receiving power from the power source, a clutch center supported on the inside of the clutch outer so as not to rotate relative to the output shaft, and friction members supported by the clutch outer and the clutch center so as to be displaceable relative to each other in the axial direction of the output shaft, and which exert frictional force when in contact with each other to transmit rotational force from the clutch outer to the clutch center.

[0004] Patent Document 1 discloses a configuration in which a primary driven gear is formed directly on the outer periphery of a clutch outer. This configuration allows the clutch device to be made smaller in the axial direction compared to a configuration in which the primary driven gear is arranged so as to overlap the clutch outer in the axial direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2020 / 0248755 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in this technology for weight reduction, the clutch device has the following problem. If the primary driven gear is integrally provided with the clutch outer, the clutch outer must also be made of a high-strength material such as iron to ensure the strength of the gear. This means that the weight of the clutch device may increase compared to when the clutch outer is made of aluminum.

[0007] The present invention aims to achieve a weight reduction of the clutch device in order to solve the above-mentioned problems, and in turn contribute to energy efficiency. [Means for solving the problem]

[0008] A clutch device according to a first aspect of the present invention includes a clutch outer (30) rotatably supported on an output shaft (20), the clutch outer having an outer bottom portion (31) formed in an annular shape coaxial with the output shaft (20) and an outer cylindrical portion (32) extending from the outer peripheral edge of the outer bottom portion (31) in the axial direction of the output shaft (20), a primary driven gear (50) formed in an annular shape coaxial with the output shaft (20), assembled to the clutch outer (30), and receiving power from a power source, a clutch center (60) supported on the output shaft (20) inside the clutch outer (30) so as not to rotate relative to the output shaft (20), and a clutch outer cylindrical portion (32) movable relative to the output shaft (20) in the axial direction. and a friction member (70) supported by the outer (30) and the clutch center (60), respectively, which exerts a frictional force when they come into contact with each other and transmits a rotational force from the clutch outer (30) to the clutch center (60), wherein the outer bottom (31) has a gear mounting portion (37) inserted inside the primary driven gear (50) and fitted to the primary driven gear (50) so as not to rotate relative to it, the primary driven gear (50) being formed from a first material, and at least one of the outer bottom (31) and the outer cylindrical portion (32) being formed from a second material, and the first material having a strength greater than that of the second material.

[0009] According to the first aspect, the primary driven gear, which receives power from the power source, is made of a material stronger than at least one of the outer bottom portion and the outer cylindrical portion, making it possible to select a material with a relatively low specific gravity as the material for forming the clutch outer. Therefore, while ensuring the strength of the primary driven gear, the weight of the clutch outer can be reduced compared to when the outer bottom portion and the outer cylindrical portion are made of the same first material as the primary driven gear. This allows for a reduction in the weight of the clutch device.

[0010] A clutch device according to a second aspect of the present invention is the clutch device according to the first aspect, wherein the second material may have a lower specific gravity than the first material.

[0011] According to the second aspect, the weight of the clutch outer can be reduced, and in turn the weight of the clutch device, compared to when the outer bottom portion and the outer cylindrical portion are formed from the same first material as the primary driven gear.

[0012] A clutch device according to a third aspect of the present invention is the clutch device according to the first or second aspect, wherein the clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and supported by the output shaft (20), and the outer shaft portion (33) may be formed from the first material.

[0013] According to the third aspect, the outer shaft portion of the clutch outer, which requires particular strength, is formed from the first material, so that the strength of the outer shaft portion can be ensured without increasing the size of the outer shaft portion.

[0014] A clutch device according to a fourth aspect of the present invention is a clutch device according to any one of the first to third aspects, wherein the clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and supported by the output shaft (20), and the outer bottom portion (31) has an outer peripheral connecting portion (35) that engages with the primary driven gear (50) and connects to the outer cylindrical portion (32), and a hub portion (36) that connects the outer peripheral connecting portion (35) and the outer shaft portion (33), and the hub portion (36) may be arranged between both ends of the primary driven gear (50) in the axial direction.

[0015] According to the fourth aspect, the hub portion can bear the load transmitted from the primary driven gear to the outer shaft portion when the primary driven gear receives power. This allows the thickness of the hub portion and its surrounding area to be thinner than in a configuration in which the hub portion is offset from the primary driven gear in the axial direction. This prevents an increase in the weight of the clutch outer.

[0016] A clutch device according to a fifth aspect of the present invention is the clutch device according to the fourth aspect, wherein the inner peripheral portion (53) of the primary driven gear (50) and the gear mounting portion (37) are spigot-fitted to each other, and the hub portion (36) may radially overlap the spigot-fitted portion (90) of the inner peripheral portion (53) of the primary driven gear (50) and the gear mounting portion (37).

[0017] According to the fifth aspect, when the primary driven gear receives power, the load transmitted from the primary driven gear to the radially inward direction through the spigot fitting portion can be borne by the hub portion. This allows the thickness of the hub portion and its surrounding area to be thinner than in a configuration in which the hub portion is not positioned radially overlapping the spigot fitting portion. This makes it possible to more effectively suppress an increase in the weight of the clutch outer.

[0018] A clutch device according to a sixth aspect of the present invention is a clutch device according to any one of the first to fifth aspects, wherein the clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and extrapolated onto the output shaft (20), the outer bottom portion (31) has an outer peripheral connecting portion (35) that engages with the primary driven gear (50) and connects to the outer cylindrical portion (32), and a hub portion (36) that connects the outer peripheral connecting portion (35) and the outer shaft portion (33), and the connecting portion of the hub portion (36) and the outer shaft portion (33) may be arranged between both ends of the primary driven gear (50) in the axial direction.

[0019] According to the sixth aspect, when the primary driven gear receives power, the load that is transmitted radially inward from the primary driven gear toward the outer shaft can be efficiently released from the hub to the outer shaft, thereby preventing excessive load from being applied to the connection between the hub and the outer shaft.

[0020] A clutch device according to a seventh aspect of the present invention is the clutch device according to the sixth aspect, wherein the inner peripheral portion (53) of the primary driven gear (50) and the gear mounting portion (37) are spigot-fitted to each other, and the connection portion of the hub portion (36) and the outer shaft portion (33) may radially overlap the spigot-fitting portion (90) of the inner peripheral portion (53) of the primary driven gear (50) and the gear mounting portion (37).

[0021] According to the seventh aspect, when the primary driven gear receives power, the load transmitted from the primary driven gear to the radially inward direction through the spigot fitting portion can be efficiently released from the connection portion between the hub portion and the outer shaft portion to the outer shaft portion, thereby more effectively preventing excessive load from being applied to the connection portion between the hub portion and the outer shaft portion.

[0022] A clutch device according to an eighth aspect of the present invention is a clutch device according to any one of the first to seventh aspects, wherein the outer peripheral portion (37o) of the gear mounting portion (37) has a tooth portion (38) that meshes with the inner peripheral portion (53) of the primary driven gear (50), and a lightening portion (43) is formed in the outer bottom portion (31) along the tooth portion (38).

[0023] According to the eighth aspect, the hub portion is more likely to flex around the hollowed-out portion. This allows the load transmitted from the primary driven gear to the hub portion when the primary driven gear receives power to be dispersed by the flexing of the hub portion. This prevents the load from concentrating in a specific location, allowing the thickness of the hub portion and its surrounding area to be reduced.

[0024] A clutch device according to a ninth aspect of the present invention is a clutch device according to any one of the first to eighth aspects, further comprising a fastening member (85) that fixes the primary driven gear (50) and the clutch outer (30) to each other, and the outer peripheral portion (37o) of the gear mounting portion (37) has a tooth portion (38) that meshes with the inner peripheral portion (53) of the primary driven gear (50), and the fastening member (85) may be arranged radially inward of the outer peripheral end of the tooth portion (38).

[0025] According to the ninth aspect, the fastening member can be provided so as not to overlap with the outer circumferential teeth of the primary driven gear in the axial direction, thereby preventing the outer diameter of the primary driven gear from becoming large. [Effects of the Invention]

[0026] According to the present invention, it is possible to achieve a reduction in the weight of the clutch device. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 2 is a cross-sectional view showing a part of the power unit according to the embodiment. [Figure 2]FIG. 2 is a cross-sectional view of a clutch outer and a primary driven gear according to the embodiment. [Figure 3] 1 is a side view of the clutch device of the embodiment as viewed from the inside in the axial direction, showing a state in which a pressing plate has been removed. FIG. [Figure 4] 1 is a perspective view of a clutch device according to an embodiment, as viewed from the inside in the axial direction. [Figure 5] 3 is an enlarged perspective view showing the periphery of a gear mounting portion of the clutch outer according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of these components may be omitted. In addition, directions such as front, rear, up, down, left, and right in the following description are the same as directions in the vehicle described below. In other words, the left and right directions coincide with the vehicle width direction. In addition, in the drawings used in the following description, the arrow LH indicates the left.

[0029] FIG. 1 is a cross-sectional view showing a part of a power unit according to an embodiment. As shown in Fig. 1, the clutch device 7 of this embodiment is provided integrally with an engine 3 and a transmission 5 as part of a power unit 1 mounted on a saddle-ride vehicle such as a motorcycle. The engine 3 includes a crankshaft 10 extending in the vehicle width direction and a crankcase 11 that houses the crankshaft 10. The crankshaft 10 rotates by converting the reciprocating motion of a piston into rotational motion. The crankcase 11 is made of metal and is formed by fastening together a left crankcase 11L and a right crankcase 11R that are split into left and right halves.

[0030] The transmission 5 is housed in the rear portion of the crankcase 11. The rear portion of the crankcase 11 also serves as a transmission case 11a that houses the transmission 5. The transmission 5 is a stepped transmission having a main shaft 12 and a countershaft 13 rotatably supported by the transmission case 11a, and a gear set 14 spanning the main shaft 12 and the countershaft 13. The main shaft 12 and the countershaft 13 each extend in the vehicle width direction. The gear set 14 switches between gear pairs used to transmit power between the main shaft 12 and the countershaft 13 in the gear set 14 by moving a shift fork of a change mechanism (not shown). A clutch device 7 is coupled to the right end of the main shaft 12. Rotational power of the crankshaft 10 is transmitted to the main shaft 12 via the clutch device 7, and then transmitted from the main shaft 12 to the countershaft 13 via any gear pair of the gear set 14. The countershaft 13 constitutes the output shaft of the power unit 1. The countershaft 13 protrudes to the left of the transmission case 11a and is coupled to a drive sprocket 15. The rotation of the countershaft 13 is transmitted from the left side of the transmission case 11a to the rear wheel via a chain drive type power transmission mechanism.

[0031] A clutch cover 16 is connected to the transmission case 11a. The clutch cover 16 is located to the right of the transmission case 11a and connected to the right crankcase 11R. The clutch cover 16 is located on an extension of the main shaft 12. A clutch chamber is defined between the clutch cover 16 and the right crankcase 11R.

[0032] The clutch device 7 is a multi-plate friction clutch that connects and disconnects the power transmission between the crankshaft 10 of the engine 3 and the main shaft 12 of the transmission 5. The clutch device 7 is connected and disconnected by the driver operating a clutch operator or by driving an actuator.

[0033] The clutch device 7 is disposed between the transmission case 11a and the clutch cover 16. The clutch device 7 is provided as an output shaft of the clutch device 7 and includes a driving force transmission shaft 20 rotatably supported by the crankcase 11, a clutch outer 30 journaled to the driving force transmission shaft 20 so as to be relatively rotatable, a primary driven gear 50 assembled to the clutch outer 30 and receiving power from the engine 3 as a power source, and a clutch center 60 supported on the driving force transmission shaft 20 inside the clutch outer 30 so as not to be relatively rotatable.

[0034] The clutch outer 30, the primary driven gear 50, and the clutch center 60 are rotatable about the rotation axis of the driving force transmission shaft 20. In the following description, the rotation axis of the driving force transmission shaft 20 will be referred to as the common axis O. The direction along the common axis O will be referred to as the axial direction, the direction perpendicular to the common axis O and extending radially from the common axis O will be referred to as the radial direction, and the direction going around the common axis O will be referred to as the circumferential direction. In this embodiment, the axial direction coincides with the vehicle width direction, the axially inner side is the direction toward the center of the vehicle along the vehicle width direction, and the axially outer side is the direction away from the center of the vehicle along the vehicle width direction.

[0035] The driving force transmission shaft 20 is the main shaft 12 of the transmission 5. The driving force transmission shaft 20 is rotatably supported by the right crankcase 11R via a ball bearing 17A, and is rotatably supported by the left crankcase 11L via a ball bearing 17B. The driving force transmission shaft 20 extends outward in the axial direction from the right crankcase 11R.

[0036] The primary driven gear 50 rotates synchronously with the crankshaft 10 by meshing with the primary drive gear 19, which rotates integrally with the crankshaft 10 of the engine 3. The primary driven gear 50 is formed in an annular shape (see FIG. 4). The primary driven gear 50 is arranged so as to overlap the clutch outer 30 from the inside in the axial direction. The entire primary driven gear 50 is arranged inside the outline of the clutch outer 30 when viewed in the axial direction (see FIG. 3). The primary driven gear 50 is made of a first material. The first material will be described later.

[0037] Fig. 2 is a cross-sectional view of the clutch outer and primary driven gear of the embodiment, Fig. 3 is a side view of the clutch device of the embodiment as seen from the axial inside, showing a state in which a pressing plate and a disc spring have been removed. As shown in FIGS. 2 and 3 , the primary driven gear 50 has an outer gear portion 51 having external teeth formed thereon that mesh with the teeth of the primary drive gear 19, and an inner gear portion 53 that engages with the clutch outer 30 so as not to rotate relative to the clutch outer 30. The inner gear portion 53 has an inner flange 54 that protrudes radially inward from the inner peripheral surface of the outer gear portion 51 and extends around the entire circumference, and engagement teeth 55 that protrude radially inward from the inner peripheral edge of the inner flange 54. The inner flange 54 is connected to the outer gear portion 51 with a gap in the axial direction from both axial ends of the inner peripheral surface of the outer gear portion 51. The engagement teeth 55 have protrusions 55a that protrude axially from their tips toward the clutch outer 30. The engagement teeth 55 are provided around the entire circumference. The engagement teeth 55 are equally spaced circumferentially except for positions where rivets 85 (described later) are arranged.

[0038] FIG. 4 is a perspective view of the clutch device of the embodiment as seen from the axially inner side. As shown in FIGS. 2 and 4, the clutch outer 30 is formed as a whole in the shape of a cylinder with a bottom. The clutch outer 30 includes an annular outer bottom portion 31, an outer cylindrical portion 32 extending axially outward from the outer peripheral edge of the outer bottom portion 31, and an outer shaft portion 33 connected to the inner peripheral edge of the outer bottom portion 31. The outer bottom portion 31 and the outer cylindrical portion 32 are integrally formed. The outer bottom portion 31 and the outer cylindrical portion 32 are formed of a second material. The second material has a lower strength than the first material. In this embodiment, the strengths compared between the first and second materials are tensile strengths. The second material has a lower specific gravity than the first material. In this embodiment, the first material is aluminum, and the second material is iron. The outer cylindrical portion 32 has a fitting groove 32a opening on its inner peripheral surface. A plurality of fitting grooves 32a are formed at equal intervals in the circumferential direction.

[0039] As shown in Figures 2 and 3, the outer bottom portion 31 overlaps the primary driven gear 50 from the outside in the axial direction. The outer bottom portion 31 includes an outer peripheral connection portion 35 that engages with the primary driven gear 50 and connects to the outer cylindrical portion 32, and an outer hub portion 36 that connects the outer peripheral connection portion 35 and the outer shaft portion 33. The outer peripheral connection portion 35 is formed in an annular shape. The outer peripheral connection portion 35 includes a gear mounting portion 37. The gear mounting portion 37 is provided on the inner peripheral portion of the outer peripheral connection portion 35 and is formed in an annular shape. The gear mounting portion 37 protrudes axially inward beyond the outer periphery of the outer peripheral connection portion 35 and extends around the entire periphery of the outer shaft portion 33. The gear mounting portion 37 is inserted inside the primary driven gear 50. The gear mounting portion 37 is inserted into the inner circumferential gear portion 53 of the primary driven gear 50 and fitted to the primary driven gear 50 so as not to rotate relative to the primary driven gear 50 .

[0040] The gear mounting portion 37 has an outer peripheral portion 37o and an inner peripheral portion 37i. The outer peripheral portion 37o overlaps the inner flange 54 of the primary driven gear 50 from the outside in the axial direction and is fitted inside the gear outer peripheral portion 51 of the primary driven gear 50. As a result, the outer peripheral portion 37o of the gear mounting portion 37 and the primary driven gear 50 are spigot-fitted to each other. Hereinafter, the location where the gear mounting portion 37 and the primary driven gear 50 are spigot-fitted to each other will be referred to as a spigot-fit portion 90. The inner peripheral portion 37i protrudes axially inward beyond the outer peripheral portion 37o. The inner peripheral portion 37i is disposed inside the gear inner peripheral portion 53 of the primary driven gear 50.

[0041] FIG. 5 is an enlarged perspective view showing the periphery of a gear mounting portion in the clutch outer of the embodiment. As shown in FIGS. 3 and 5 , the inner circumferential portion 37i has engaged teeth 38 that mesh with the engaging teeth 55 of the primary driven gear 50. The engaged teeth 38 and the engaging teeth 55 are fitted together by radial concaves and convexes. As a result, the inner circumferential portion 37i of the gear mounting portion 37 and the primary driven gear 50 are engaged with each other so that they cannot rotate relative to each other. A plurality of engaged teeth 38 are provided around the entire circumference corresponding to the engaging teeth 55. The tooth grooves of the engaged teeth 38 open on the axially inner end face of the inner circumferential portion 37i. A recess 39 into which the protrusion 55a of the engaging tooth 55 is inserted is formed on the axially inner end face of the gear mounting portion 37. The recess 39 includes the tooth groove of the engaged tooth 38 when viewed from the axial direction. In the illustrated example, the recess 39 is provided from the inner circumferential portion 37i to the outer circumferential portion 37o of the gear mounting portion 37. However, the recess may be provided only on the inner peripheral portion 37i of the gear mounting portion 37.

[0042] As shown in FIGS. 2 and 3 , the outer bottom portion 31 is provided with fastening seats 41, to which rivets 85 (fastening members) are attached, protruding axially inward. The fastening seats 41 are provided in the gear mounting portion 37. A plurality of fastening seats 41 are provided at equal intervals in the circumferential direction. In the illustrated example, five fastening seats 41 are provided. The fastening seats 41 are disposed inside the primary driven gear 50 as viewed in the axial direction. The fastening seats 41 are located radially at a position corresponding to the inner peripheral portion 37i of the gear mounting portion 37. The fastening seats 41 have a through-hole that penetrates the outer bottom portion 31 in the axial direction and into which the rivet 85 is inserted from the axially inner side. The rivet 85 has a head 85a located axially inward of the fastening seat 41. The head 85a of the rivet 85 is located radially inward of the outer peripheral end of the engaged tooth 38. A presser plate 86 is sandwiched between the head 85a and the fastening seat 41. The presser plate 86 is formed in the shape of an annular plate coaxial with the primary driven gear 50. When viewed from the axial direction, the presser plate 86 overlaps with the engaging teeth 55 of the primary driven gear 50. The presser plate 86 presses the primary driven gear 50 toward the outer bottom portion 31 (outward in the axial direction) via the disc springs 87, thereby preventing the primary driven gear 50 from falling off. Note that, because power from the engine 3 does not directly act on the rivets 85, the number and load of the rivets 85 need only be set so that the rivets 85 can press the disc springs 87 evenly.

[0043] As shown in FIGS. 2 and 4 , the outer hub portion 36 is formed in an annular shape. The outer hub portion 36 is formed in a flat plate shape extending perpendicular to the axial direction. The outer peripheral edge of the outer hub portion 36 is connected to the inner peripheral portion 37i of the gear mounting portion 37. The outer hub portion 36 is located between both ends of the gear mounting portion 37 in the axial direction. The outer hub portion 36 radially overlaps the spigot fitting portion 90 between the gear mounting portion 37 and the primary driven gear 50. Furthermore, the outer hub portion 36 radially overlaps the meshing portion between the engaging teeth 55 of the primary driven gear 50 and the engaged teeth 38 of the gear mounting portion 37. The outer hub portion 36 is formed with a lightening portion 43. The lightening portion 43 penetrates the outer hub portion 36 in the axial direction. A plurality of lightening portions 43 are formed at equal intervals in the circumferential direction. In this embodiment, five lightening portions 43 are formed. The recessed portion 43 is formed in the circumferential direction so as to avoid the fastening seat 41. The recessed portion 43 is formed on the outer periphery of the outer hub portion so as to follow the engaged teeth .

[0044] The outer shaft portion 33 is formed in a cylindrical shape. The outer shaft portion 33 is fitted onto the driving force transmission shaft 20 and rotatably supported on the driving force transmission shaft 20. The outer shaft portion 33 is connected to the inner peripheral edge of the outer hub portion 36. This makes the clutch outer 30 a single member. The outer shaft portion 33 is formed from a first material. The outer shaft portion 33 is connected to the outer hub portion 36 by welding. For example, the outer shaft portion 33 is connected to the outer hub portion 36 by ring mash welding. The connection portion between the outer shaft portion 33 and the outer hub portion 36 is disposed axially between both ends of the primary driven gear 50. The connection portion between the outer shaft portion 33 and the outer hub portion 36 radially overlaps a spigot fitting portion 90 between the gear mounting portion 37 and the primary driven gear 50. Furthermore, the outer hub portion 36 overlaps in the radial direction with the meshing portion between the engaging teeth 55 of the primary driven gear 50 and the engaged teeth 38 of the gear mounting portion 37 .

[0045] In this embodiment, no buffer mechanism is provided between the clutch outer 30 and the primary driven gear 50 to absorb torque fluctuations transmitted from one to the other, and the clutch outer 30 and the primary driven gear 50 always rotate together. Furthermore, in this embodiment, the clutch outer 30 and the primary driven gear 50 are able to rotate together by the meshing of the engaging teeth 55 and the engaged teeth 38, and the primary driven gear 50 does not have a through hole into which a boss formed on the clutch outer is inserted, as in a conventional coupling structure between a primary driven gear and a clutch outer.

[0046] As shown in FIG. 1 , the clutch center 60 is disposed inside the outer cylindrical portion 32. The clutch center 60 is formed in an annular shape when viewed in the axial direction. The clutch center 60 includes a center hub portion 61 provided on the inner periphery of the clutch center 60 and spline-fitted to the outer periphery of the driving force transmission shaft 20, an annular pressure-receiving wall portion 62 provided on the outer periphery of the clutch center 60, and a center cylindrical portion 63 extending axially outward from the inner periphery of the pressure-receiving wall portion 62. Note that in this embodiment, the center hub portion 61, the pressure-receiving wall portion 62, and the center cylindrical portion 63 are formed as separate members, but it is sufficient that the center hub portion 61, the pressure-receiving wall portion 62, and the center cylindrical portion 63 are rotatable together. The center hub portion 61 is fastened to the driving force transmission shaft 20 by a nut threaded onto the right end of the driving force transmission shaft 20.

[0047] The pressure-receiving wall portion 62 is adjacent to and faces the outer bottom portion 31 of the clutch outer 30 in the axial direction. The pressure-receiving wall portion 62 has a pressure-receiving surface 62a facing outward in the axial direction. The pressure-receiving surface 62a is an annular flat surface extending in a direction perpendicular to the axial direction.

[0048] The center cylindrical portion 63 is disposed inside the outer cylindrical portion 32. The center cylindrical portion 63 is disposed so as to face the outer cylindrical portion 32 in the radial direction. An engaged protrusion 64 is formed on the center cylindrical portion 63. The engaged protrusion 64 protrudes radially outward. The engaged protrusion 64 extends in the axial direction. A plurality of engaged protrusions 64 are provided at equal intervals in the circumferential direction.

[0049] The clutch device 7 further comprises a friction plate set 70 (friction member) that is supported by the clutch outer 30 and the clutch center 60 so as to be relatively displaceable in the axial direction, and that exerts a frictional force when in contact with each other, thereby transmitting a rotational force from the clutch outer 30 to the clutch center 60, and a pressure member 75 that is disposed so as to be displaceable relative to the clutch center 60 between a first position that restricts mutual contact of the friction plate sets 70 and a second position that releases the friction plate sets 70 from mutual contact.

[0050] The friction plate set 70 is arranged axially outward from the pressure-receiving wall portion 62. The friction plate set 70 is formed in a cylindrical shape as a whole, and is arranged coaxially with the common axis O. The friction plate set 70 is arranged between the outer cylindrical portion 32 of the clutch outer 30 and the center cylindrical portion 63 of the clutch center 60. The friction plate set 70 is in contact with the pressure-receiving surface 62a of the pressure-receiving wall portion 62. The friction plate set 70 is formed by stacking friction plates 71 and clutch plates 72 so that they overlap alternately in the axial direction. The friction plates 71 and the clutch plates 72 are each formed in an annular shape, and are arranged coaxially with the common axis O.

[0051] The friction plates 71 are provided on their outer peripheries with engaging outer protrusions 71a that protrude radially outward. The engaging outer protrusions 71a protrude radially outward beyond the outer periphery of the clutch plates 72. The engaging outer protrusions 71a fit into the fitting grooves 32a of the outer cylindrical portion 32. As a result, the friction plates 71 are fitted into the inner periphery of the outer cylindrical portion 32 so as to be axially slidable, and rotate integrally with the clutch outer 30.

[0052] The clutch plates 72 are provided on their inner peripheral portions with engaging inner protrusions 72a that protrude radially inward. The engaging inner protrusions 72a protrude radially inward beyond the inner peripheral edges of the friction plates 71. The engaging inner protrusions 72a fit into grooves between engaged protrusions 64 provided on the center cylindrical portion 63. As a result, the clutch plates 72 are spline-fitted to the outer peripheral surface of the center cylindrical portion 63 so as to be axially slidable, and rotate integrally with the clutch center 60.

[0053] When the friction plates 71 and the clutch plates 72 are brought into contact with each other and the friction plate set 70 is frictionally engaged as a unit, a rotational force is transmitted from the clutch outer 30 to the clutch center 60 via the friction plate set 70. When the friction plates 71 and the clutch plates 72 are released from contact with each other, slippage occurs between the friction plates 71 and the clutch plates 72, and the transmission of the rotational force is cut off.

[0054] The pressure member 75 is disposed axially outward from the clutch center 60. The pressure member 75 axially sandwiches the friction plate set 70 between itself and the pressure-receiving wall portion 62 from the opposite side of the clutch center 60 in the axial direction (axially outer side). When the pressure member 75 is located at a first axial position, the pressure member 75 sandwiches the friction plate set 70 between itself and the clutch center 60, generating a friction force between the friction plates 71 and the clutch plates 72 to frictionally engage the friction plate set 70 as a unit. By displacing axially outward from the first position to the second position, the pressure member 75 reduces the friction force generated between the friction plates 71 and the clutch plates 72 and releases the frictional engagement of the friction plate set 70.

[0055] The pressure member 75 is formed in an annular shape when viewed axially and is disposed coaxially with the common axis O. The pressure member 75 includes a pressure wall portion 76 disposed on its outer periphery. The pressure wall portion 76 faces the friction plate set 70 from the axially opposite side of the pressure-receiving wall portion 62 of the pressure member 75. The pressure wall portion 76 has a pressure surface 76a facing inward in the axial direction. The pressure surface 76a is an annular flat surface extending in a direction perpendicular to the axial direction. The pressure surface 76a contacts the friction plate set 70 from the side opposite the pressure-receiving surface 62a of the clutch center 60. The pressure member 75 is biased toward the first position by a spring member (not shown). The pressure member 75 is supported at its center by a lifter member 81 (described later). The pressure member 75 is pressed axially outward via the lifter member 81 by a push rod (not shown) disposed inside the driving force transmission shaft 20.

[0056] As described above, the clutch device 7 of this embodiment includes the clutch outer 30 having the outer bottom portion 31 and the outer cylindrical portion 32 extending axially from the outer peripheral edge of the outer bottom portion 31, and the primary driven gear 50 assembled to the clutch outer 30 and receiving power from a power source. The outer bottom portion 31 has a gear mounting portion 37 inserted inside the primary driven gear 50 and fitted to the primary driven gear 50 so as not to rotate relative to the primary driven gear 50. The primary driven gear 50 is made of a first material. The outer bottom portion 31 and the outer cylindrical portion 32 are made of a second material. The first material has a higher strength than the second material. With this configuration, the primary driven gear 50, which receives power from the power source, is made of a material stronger than the outer bottom portion 31 and the outer cylindrical portion 32, making it possible to select a material with a relatively low specific gravity for forming the clutch outer 30. Therefore, while ensuring the strength of the primary driven gear 50, the weight of the clutch outer 30 can be reduced compared to when the outer bottom portion and the outer cylindrical portion are formed from the same first material as the primary driven gear 50. In this embodiment, the strength of the primary driven gear 50 is ensured by making the tensile strength of the material of the primary driven gear 50 higher than the tensile strength of the material of the outer bottom portion 31 and the outer cylindrical portion 32, thereby ensuring durability against stress generated at the tooth base of the primary driven gear 50. Therefore, it is possible to reduce the weight of the clutch device 7.

[0057] The second material has a smaller specific gravity than the first material. With this configuration, the weight of the clutch outer 30 can be reduced, and in turn the weight of the clutch device 7, compared to when the outer bottom portion and the outer cylindrical portion are made of the same first material as the primary driven gear 50.

[0058] The clutch outer 30 has an outer shaft portion 33 connected to the inner peripheral edge of the outer bottom portion 31 and supported by the output shaft. The outer shaft portion 33 is made of a first material. With this configuration, the outer shaft portion 33, which is particularly required to be strong among the parts of the clutch outer 30, is made of the first material, so the strength of the outer shaft portion 33 can be ensured without increasing the size of the outer shaft portion 33.

[0059] The clutch outer 30 has an outer shaft portion 33 connected to the inner peripheral edge of the outer bottom portion 31 and supported by the output shaft. The outer bottom portion 31 has an outer peripheral connection portion 35 that engages with the primary driven gear 50 and connects to the outer cylindrical portion 32, and an outer hub portion 36 that connects the outer peripheral connection portion 35 and the outer shaft portion 33. The outer hub portion 36 is disposed axially between both ends of the primary driven gear 50. With this configuration, the outer hub portion 36 can bear the load transmitted from the primary driven gear 50 to the outer shaft portion 33 when the primary driven gear 50 receives power. This allows the thickness of the outer hub portion 36 and its surrounding areas to be thinner than in a configuration in which the outer hub portion is offset axially from the primary driven gear 50. This prevents an increase in the weight of the clutch outer 30.

[0060] The outer hub portion 36 overlaps radially with the inner circumferential portion 37i of the primary driven gear 50 and the spigot fitting portion 90 of the gear mounting portion 37. With this configuration, when the primary driven gear 50 receives power, the load that is transmitted radially inward from the primary driven gear 50 through the spigot fitting portion 90 can be borne by the outer hub portion 36. This allows the thickness of the outer hub portion 36 and its surrounding areas to be thinner than in a configuration in which the outer hub portion is not positioned radially overlapping the spigot fitting portion 90. Therefore, an increase in the weight of the clutch outer 30 can be more effectively suppressed.

[0061] The connection portion of the outer hub portion 36 and the outer shaft portion 33 is located axially between both ends of the primary driven gear 50. With this configuration, when the primary driven gear 50 receives power, the load that is transmitted radially inward from the primary driven gear 50 toward the outer shaft portion 33 can be efficiently released from the outer hub portion 36 to the outer shaft portion 33. Therefore, it is possible to prevent excessive load from being applied to the connection portion of the outer hub portion 36 and the outer shaft portion 33.

[0062] The connection portion of the outer hub portion 36 and the outer shaft portion 33 radially overlaps the inner circumferential portion 37i of the primary driven gear 50 and the spigot fitting portion 90 of the gear mounting portion 37. With this configuration, when the primary driven gear 50 receives power, the load is transmitted radially inward from the primary driven gear 50 through the spigot fitting portion 90, and the connection portion of the outer hub portion 36 and the outer shaft portion 33 can efficiently release the load from the outer hub portion 36 to the outer shaft portion 33. This more effectively prevents excessive load from being applied to the connection portion of the outer hub portion 36 and the outer shaft portion 33.

[0063] The outer circumferential portion 37o of the gear mounting portion 37 has engaged teeth 38 that mesh with engaging teeth 55 on the inner circumferential portion 37i of the primary driven gear 50. A lightening portion 43 is formed in the outer bottom portion 31 along the engaged teeth 38. With this configuration, the outer hub portion 36 is more likely to flex around the lightening portion 43. As a result, the load transmitted from the primary driven gear 50 to the outer hub portion 36 when the primary driven gear 50 receives power can be dispersed by the flexure of the outer hub portion 36. This prevents the load from concentrating at a specific location, and allows the thickness of the outer hub portion 36 and its surrounding areas to be reduced.

[0064] The clutch device 7 further includes a rivet 85 that secures the primary driven gear 50 and the clutch outer 30 to each other. The rivet 85 is disposed radially inward of the outer circumferential end of the engaged teeth 38. With this configuration, the rivet 85 can be provided so as not to overlap the outer circumferential teeth of the primary driven gear 50 in the axial direction. This prevents the outer diameter of the primary driven gear 50 from becoming larger. However, the clutch device may include a screw instead of the rivet 85 as a fastening member. When the primary driven gear and the clutch outer are secured to each other with a screw, replacement of the primary driven gear becomes easy, and the primary driven gear can be replaced with a different one as needed, such as to change the number of teeth.

[0065] The present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope of the present invention. For example, in the above embodiment, the present invention is applied to a power unit having an engine as a power source, but the present invention may also be applied to a power unit having a motor as a power source.

[0066] In the above embodiment, both the outer bottom portion 31 and the outer cylindrical portion 32 of the clutch outer 30 are formed from the second material, but this configuration is not limited thereto. That is, it is sufficient that at least one of the outer bottom portion and the outer cylindrical portion is formed from the second material. Also, in the above embodiment, the outer shaft portion 33 is formed from the same first material as the primary driven gear 50, but the material forming the outer shaft portion is not particularly limited, and it may be formed from, for example, the second material.

[0067] In the above embodiment, the engagement teeth 55 of the primary driven gear 50 are arranged in the circumferential direction, but this configuration is not limited to this. The primary driven gear and the gear mounting portion of the clutch outer may be engaged with each other at least at one point in the circumferential direction by a radial concavo-convex portion so as to prevent relative rotation.

[0068] In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0069] 7...Clutch device 20...Driving force transmission shaft (output shaft) 30...Clutch outer 31...Outer bottom 32...Outer cylindrical portion 33...Outer shaft portion 35...Outer peripheral connection portion 36...Outer hub portion (hub portion) 37...Gear mounting portion 38...Engaged teeth (tooth portion) 43...Lightening portion 50...Primary driven gear 60...Clutch center 70...Friction plate set (friction member) 85...Rivet (fastening member) 90...Spigot fitting portion

Claims

1. a clutch outer (30) that is rotatably supported on an output shaft (20) and has an outer bottom portion (31) formed in an annular shape coaxial with the output shaft (20), and an outer cylindrical portion (32) that extends from the outer peripheral edge of the outer bottom portion (31) in the axial direction of the output shaft (20); a primary driven gear (50) formed in an annular shape coaxial with the output shaft (20), assembled to the clutch outer (30), and receiving power from a power source; a clutch center (60) supported on the output shaft (20) inside the clutch outer (30) so as not to be rotatable relative to the output shaft (20); a friction member (70) supported by the clutch outer (30) and the clutch center (60), respectively, so as to be relatively displaceable in the axial direction of the output shaft (20), and which exerts a frictional force when in contact with each other, thereby transmitting a rotational force from the clutch outer (30) to the clutch center (60); Equipped with The outer bottom portion (31) has a gear mounting portion (37) inserted inside the primary driven gear (50) and fitted to the primary driven gear (50) so as not to rotate relative to the primary driven gear (50), the primary driven gear (50) is made of a first material; At least one of the outer bottom portion (31) and the outer cylindrical portion (32) is formed from a second material; The first material has a higher strength than the second material. Clutch device.

2. The second material has a lower specific gravity than the first material.

2. The clutch device according to claim 1.

3. The clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and supported by the output shaft (20), The outer shaft portion (33) is formed from the first material.

3. The clutch device according to claim 1 or 2.

4. The clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and supported by the output shaft (20), The outer bottom (31) an outer peripheral connection portion (35) that engages with the primary driven gear (50) and is connected to the outer cylindrical portion (32); a hub portion (36) connecting the outer peripheral connection portion (35) and the outer shaft portion (33); and The hub portion (36) is disposed between both ends of the primary driven gear (50) in the axial direction.

3. The clutch device according to claim 1 or 2.

5. an inner circumferential portion (53) of the primary driven gear (50) and the gear mounting portion (37) are spigot-fitted to each other; The hub portion (36) radially overlaps the inner peripheral portion (53) of the primary driven gear (50) and the spigot fitting portion (90) of the gear mounting portion (37).

5. The clutch device according to claim 4.

6. The clutch outer (30) has an outer shaft portion (33) connected to the inner peripheral edge of the outer bottom portion (31) and fitted onto the output shaft (20), The outer bottom (31) an outer peripheral connection portion (35) that engages with the primary driven gear (50) and is connected to the outer cylindrical portion (32); a hub portion (36) connecting the outer peripheral connection portion (35) and the outer shaft portion (33); and a connecting portion between the hub portion (36) and the outer shaft portion (33) is disposed between both ends of the primary driven gear (50) in the axial direction; 3. The clutch device according to claim 1 or 2.

7. an inner circumferential portion (53) of the primary driven gear (50) and the gear mounting portion (37) are spigot-fitted to each other; A connection portion between the hub portion (36) and the outer shaft portion (33) radially overlaps the inner peripheral portion (53) of the primary driven gear (50) and a spigot fitting portion (90) of the gear mounting portion (37).

7. The clutch device according to claim 6.

8. The outer circumferential portion (37o) of the gear mounting portion (37) has a tooth portion (38) that meshes with the inner circumferential portion (53) of the primary driven gear (50), The outer bottom portion (31) has a lightening portion (43) formed along the tooth portion (38).

3. The clutch device according to claim 1 or 2.

9. The clutch mechanism further includes a fastening member (85) that fastens the primary driven gear (50) and the clutch outer (30) to each other, The outer circumferential portion (37o) of the gear mounting portion (37) has a tooth portion (38) that meshes with the inner circumferential portion (53) of the primary driven gear (50), The fastening member (85) is disposed radially inward of the outer circumferential end of the tooth portion (38).

3. The clutch device according to claim 1 or 2.

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