Power transmission device

Abstract

A power transmission device K comprises a centrifugal clutch means 9 having: a weight member 10 configured to be movable to an outer diameter-side position from an inner diameter-side position by centrifugal force associated with rotation of a clutch housing 2; and a pressure contact member 12 that moves in a direction for bringing a driving-side clutch plate 6 and a driven-side clutch plate 7 into pressure contact with each other when the weight member 10 moves to the outer diameter-side position from the inner diameter-side position. The weight member 10 is configured to bring the driving-side clutch plate 6 and the driven-side clutch plate 7 into pressure contact with each other via the pressure contact member 12 in the process where the weight member 10 moves to the outer diameter-side position from the inner diameter-side position. The centrifugal clutch means 9 has, on a portion where the weight member 10 and the pressure contact member 12 contact each other, first gradient surfaces 10a, 12a, and second gradient surfaces 10b, 12b having a greater gradient angle with respect to the axial direction of an output shaft 3 than the first gradient surfaces 10a, 12a.

Description

power transmission device

[0001] The present invention relates to a power transmission device that can arbitrarily transmit or block the rotational force of an input member to an output member.

[0002] As a conventional power transmission device, for example, Patent Document 1 discloses a centrifugal clutch means having a weight member that can move from an inner diameter side position to an outer diameter side position by centrifugal force accompanying rotation of the clutch housing, thereby pressing the driving side clutch plates and the driven side clutch plates into contact with each other via a pressing member. In this conventional power transmission device, when the clutch housing rotates in conjunction with the driving of a drive source such as an engine, centrifugal force can be applied to the weight member, and the driving side clutch plates and the driven side clutch plates can be pressed into contact with each other via the pressing member, thereby transmitting the driving force of the engine to the wheels.

[0003] International Publication No. 2013 / 183588

[0004] However, when the conventional power transmission device is applied to a small vehicle, for example, with a small engine displacement and a low clutch housing rotation speed (i.e., a large primary ratio), it is relatively difficult to set a large centrifugal force on the weight member. This requires, for example, a large gradient angle of the cam surface that converts the thrust of the weight member into a pressing force between the driving clutch plate and the driven clutch plate. However, setting a large gradient angle of the cam surface reduces the amount of axial movement of the pressing member. In other words, the amount of movement of the pressing member between the driving clutch plate and the driven clutch plate in the pressing direction (i.e., the axial direction of the output member) is reduced. This can make it difficult to press the driving clutch plate and the driven clutch plate together and sufficiently transmit driving force.

[0005] The present invention has been made in consideration of the above points, and its object is to provide a power transmission device equipped with a centrifugal clutch means that can ensure the axial movement of the output member of the pressing member and the thrust force from the weight member that are necessary to press the driving side clutch plate and the driven side clutch plate together and sufficiently transmit the driving force.

[0006] The power transmission device according to the present invention comprises a clutch member that rotates together with an input member that rotates by the driving force of a drive source, that is housed in a clutch housing that holds a plurality of drive-side clutch plates, and that is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be able to approach or move away from the clutch member, and that is able to press against a plurality of driven-side clutch plates and the plurality of drive-side clutch plates that are arranged alternately with the drive-side clutch plates; a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force that accompanies rotation of the clutch housing; and a pressing member that is provided so as to be able to come into contact with the weight member, and that moves in a direction that presses against the drive-side clutch plates and the driven-side clutch plates as the weight member moves from the inner diameter side position to the outer diameter side position, and and a centrifugal clutch means that presses the driving side clutch plate and the driven side clutch plate together when the weight member is in the inner diameter side position, thereby enabling the driving force of the driving source to be transmitted to the wheels, and that releases the pressing force between the driving side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby interrupting the transmission of the driving force of the driving source to the wheels, wherein the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member when the weight member moves from the inner diameter side position to the outer diameter side position, and the centrifugal clutch means has a first inclined surface and a second inclined surface that has a larger inclination angle with respect to the axial direction of the output member than the first inclined surface at a portion where the weight member and the pressing member contact each other of at least one of the weight member and the pressing member.

[0007] In the power transmission device according to the present invention, the centrifugal clutch means has a first inclined surface and a second inclined surface at a portion of at least one of the weight member and the pressure contact member where the weight member and the pressure contact member contact each other, the second inclined surface having a larger inclination angle with respect to the axial direction of the output member than the first inclined surface. According to the above aspect, the required amount of axial movement of the pressure contact member in the output member and the thrust force of the weight member can be ensured depending on the operating state.

[0008] Another power transmission device according to the present invention includes a clutch member that rotates together with an input member that rotates by the driving force of a drive source, and is housed in a clutch housing that holds a plurality of driving side clutch plates, and is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be able to approach or move away from the clutch member, and is able to press a plurality of driven side clutch plates and the driving side clutch plates that are arranged alternately with the driving side clutch plates; a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force that accompanies rotation of the clutch housing; and a pressing member that is provided so as to be able to come into contact with the weight member, and that moves in a direction that presses the driving side clutch plates and the driven side clutch plates into contact with each other as the weight member moves from the inner diameter side position to the outer diameter side position, and and centrifugal clutch means that at a certain time presses the driving side clutch plate and the driven side clutch plate together to enable transmission of the driving force of the driving source to the wheel, and that, when the weight member is in the inner diameter side position, releases the pressing force between the driving side clutch plate and the driven side clutch plate to interrupt transmission of the driving force of the driving source to the wheel, wherein the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member as the weight member moves from the inner diameter side position to the outer diameter side position, and the centrifugal clutch means has, at a portion where the weight member and the pressing member of at least one of the weight member and the pressing member contact, a first region and a second region in which the amount of movement of the pressing member in the axial direction of the output member is smaller than in the first region.

[0009] In another power transmission device according to the present invention, the centrifugal clutch means has a first region at a portion where at least one of the weight member and the pressing member contacts the pressing member, and a second region in which the amount of axial movement of the pressing member of the output member is smaller than that of the first region. According to the above aspect, the necessary amount of axial movement of the pressing member of the output member and the thrust force of the weight member can be ensured depending on the operating state.

[0010] Another power transmission device according to the present invention includes a clutch member that rotates together with an input member that rotates by the driving force of a drive source, and is housed in a clutch housing that holds a plurality of driving-side clutch plates, and is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be able to approach or move away from the clutch member, and is able to press a plurality of driven-side clutch plates and a plurality of the driving-side clutch plates that are arranged alternately with the driving-side clutch plates; a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force that accompanies rotation of the clutch housing; and a pressing member that is provided so as to be able to come into contact with the weight member, and that moves in a direction that presses the driving-side clutch plates and the driven-side clutch plates together as the weight member moves from the inner diameter side position to the outer diameter side position, and and a centrifugal clutch means for pressing the driving side clutch plate and the driven side clutch plate together when the weight member is in the inner diameter side position, thereby enabling the driving force of the driving source to be transmitted to the wheels, and for releasing the pressing force between the driving side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby interrupting the transmission of the driving force of the driving source to the wheels, wherein the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member as the weight member moves from the inner diameter side position to the outer diameter side position, and the centrifugal clutch means has a first region and a second region in which the thrust from the weight member is greater than that in the first region at a portion where the weight member and the pressing member contact each other of at least one of the weight member and the pressing member.

[0011] In another power transmission device according to the present invention, the centrifugal clutch means has a first region and a second region in which the thrust force from the weight member is greater than that from the first region at a portion of contact between at least one of the weight member and the pressing member. According to the above aspect, the required amount of axial movement of the pressing member in the output member and the required thrust force from the weight member can be ensured depending on the operating state.

[0012] According to the present invention, it is possible to provide a power transmission device equipped with a centrifugal clutch means that can ensure the axial movement of the output member of the pressing member and the thrust force from the weight member that are necessary to press the driving side clutch plate and the driven side clutch plate together and sufficiently transmit the driving force.

[0013] FIG. 1 is an external view showing a power transmission device according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is an exploded perspective view of the power transmission device according to the first embodiment. FIG. 5 is an exploded perspective view of the power transmission device according to the first embodiment. FIG. 6 is an exploded perspective view of the centrifugal clutch means according to the first embodiment. FIG. 7 is a perspective view of a weight member according to the first embodiment. FIG. 8 is a plan view and a rear view of the weight member according to the first embodiment. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. FIG. 10 is a perspective view of a pressing member according to the first embodiment. FIG. 11 is a plan view and a side view of the pressing member according to the first embodiment. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11. FIG. 13 is a perspective view of a holding member according to the first embodiment. FIG. 14 is a cross-sectional view showing the operation of the centrifugal clutch means according to the first embodiment (weight member in the inner diameter position). FIG. 15 is a cross-sectional view showing the operation of the centrifugal clutch means according to the first embodiment (when the weight member is in a position between the inner diameter side position and the outer diameter side position). FIG. 16 is a cross-sectional view showing the operation of the centrifugal clutch means according to the first embodiment (when the weight member is in an outer diameter side position). FIG. 17 is a schematic diagram showing a vehicle to which the power transmission device according to the first embodiment is applied. FIG. 18 is a perspective view showing a weight member according to a second embodiment. FIG. 19 is a plan view and a rear view showing a weight member according to the second embodiment. FIG. 20 is a cross-sectional view taken along line XX-XX in FIG. 19. FIG. 21 is a cross-sectional view showing the operation of the centrifugal clutch means according to the second embodiment (when the weight member is in an inner diameter side position). FIG. 22 is a cross-sectional view showing the operation of the centrifugal clutch means according to the second embodiment (when the weight member is in a position between the inner diameter side position and the outer diameter side position). FIG. 23 is a cross-sectional view showing the operation of the centrifugal clutch means according to the second embodiment (when the weight member is in an outer diameter side position). FIG. 24 is a perspective view showing a weight member according to a third embodiment. FIG. 25 is a plan view and a rear view showing a weight member according to the third embodiment. Fig. 26 is a cross-sectional view taken along the line XXVI-XXVI in Fig. 25. Fig. 27 is a cross-sectional view showing the operation of the centrifugal clutch means according to the third embodiment (weight member in the inner diameter position).FIG. 28 is a cross-sectional view showing the operation of the centrifugal clutch means according to the third embodiment (weight member in a position between the inner diameter side position and the outer diameter side position). FIG. 29 is a cross-sectional view showing the operation of the centrifugal clutch means according to the third embodiment (weight member in an outer diameter side position). FIG. 30 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fourth embodiment (weight member in an inner diameter side position). FIG. 31 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fourth embodiment (weight member in a position between the inner diameter side position and the outer diameter side position). FIG. 32 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fourth embodiment (weight member in an outer diameter side position). FIG. 33 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fifth embodiment (weight member in an inner diameter side position). FIG. 34 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fifth embodiment (weight member in a position between the inner diameter side position and the outer diameter side position). FIG. 35 is a cross-sectional view showing the operation of the centrifugal clutch means according to the fifth embodiment (weight member in an outer diameter side position). Fig. 36 is a cross-sectional view showing the operation of the centrifugal clutch means according to the sixth embodiment (weight member in the inner diameter side position). Fig. 37 is a cross-sectional view showing the operation of the centrifugal clutch means according to the sixth embodiment (weight member in a position between the inner diameter side position and the radial side position). Fig. 38 is a cross-sectional view showing the operation of the centrifugal clutch means according to the sixth embodiment (weight member in the outer diameter side position). Fig. 39 is a graph showing the relationship between the engine rotation speed and the amount of movement of the pressing member. Fig. 40 is a graph showing the relationship between the engine rotation speed and the thrust force exerted by the weight member.

[0014] First Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 17 , a power transmission device K is disposed in a vehicle and is used to selectively transmit or interrupt the driving force of an engine E to driving wheels T via a transmission M. The engine E is an example of a driving source. The driving wheels T are an example of wheels. As shown in FIGS. 1 to 16 , the power transmission device K includes a clutch housing 2 having an input gear 1 formed thereon that rotates with the driving force of the vehicle's engine E, an output shaft 3 connected to the transmission M, a clutch member 4, a pressure member 5, a plurality of driving-side clutch plates 6 and a plurality of driven-side clutch plates 7, and a centrifugal clutch means 9 having a weight member 10. In the drawings, reference numeral 8 denotes a fixed member, reference numeral S denotes a clutch spring, reference numeral f denotes a return spring, and reference numeral B denotes a bolt. The input gear 1 is an example of an input member. The output shaft 3 is an example of an output member.

[0015] The input gear 1 is configured to be rotatable about the output shaft 3 when a driving force (rotational force) transmitted from the engine E is input. The input gear 1 is connected to a clutch housing 2 by rivets or the like. As shown in Figures 4 and 5, the clutch housing 2 is formed in a cylindrical shape with one end open. The clutch housing 2 rotates together with the input gear 1 due to the driving force of the engine E.

[0016] 4 and 5, the clutch housing 2 has a plurality of notches 2a formed around the circumference. A plurality of drive-side clutch plates 6 are fitted into the notches 2a and attached. That is, the clutch housing 2 holds a plurality of drive-side clutch plates 6. The drive-side clutch plates 6 are made of a plate material having a substantially annular shape. The drive-side clutch plates 6 are configured to be movable along the axial direction of the clutch housing 2 (i.e., the axial direction of the output shaft 3) and to be rotatable integrally with the clutch housing 2.

[0017] As shown in Fig. 2, the clutch member 4 is housed in a clutch housing 2. The clutch member 4 holds a plurality of driven-side clutch plates 7 arranged alternately with driving-side clutch plates 6. The clutch member 4 is connected to an output shaft 3 that can rotate driving wheels T via a transmission M of the vehicle. As shown in Figs. 4 and 5, the clutch member 4 includes a first clutch member 4a and a second clutch member 4b. The first clutch member 4a is engaged with the second clutch member 4b.

[0018] As shown in Figures 4 and 5, the first clutch member 4a has a through-hole 4ac formed in its center. The output shaft 3 is inserted into the through-hole 4ac, and the splines formed therein mesh with each other to couple the first clutch member 4a in the rotational direction. That is, the first clutch member 4a is coupled to the output shaft 3. The second clutch member 4b has an outer peripheral wall 4bc formed in an annular shape and a flange portion 4bb extending radially outward from the outer peripheral wall 4bc. A spline fitting portion 4ba is formed on the outer peripheral wall 4bc. The spline fitting portion 4ba has a concave-convex shape integrally formed over substantially the entire circumference of the outer peripheral wall 4bc. The driven-side clutch plates 7 are attached by spline fitting into the recessed grooves of the spline fitting portion 4ba. That is, the second clutch member 4b holds the driven-side clutch plates 7. The driven-side clutch plate 7 is configured to be movable along the axial direction of the clutch member 4 (e.g., the second clutch member 4b) (i.e., the axial direction of the output shaft 3) and to be rotatable integrally with the clutch member 4 (e.g., the first clutch member 4a and the second clutch member 4b). The second clutch member 4b is configured to be movable in the axial direction of the output shaft 3.

[0019] As shown in Figure 4, the pressure member 5 is made up of a disk-shaped member with a flange portion 5a formed on its periphery. The pressure member 5 is attached to the clutch member 4. The pressure member 5 is provided so as to be able to move towards or away from the clutch member 4. The pressure member 5 is configured so as to be able to press the drive-side clutch plates 6 and the driven-side clutch plates 7 together. The pressure member 5 is configured so as to be able to press the drive-side clutch plates 6 and the driven-side clutch plates 7 together with the clutch member 4. The pressure member 5 presses the drive-side clutch plates 6 and the driven-side clutch plates 7 together, thereby transmitting the driving force of the engine E to the drive wheels W. That is, the driving-side clutch plates 6 and the driven-side clutch plates 7 are stacked between the flange portion 5a of the pressure member 5 and the flange portion 4bb of the second clutch member 4b, and when the second clutch member 4b moves toward the pressure member 5 (in the direction of arrow DR2 in FIG. 2 ), the driving-side clutch plates 6 and the driven-side clutch plates 7 are pressed together, and the rotational force of the clutch housing 2 is transmitted to the output shaft 3 via the second clutch member 4b and the first clutch member 4a. On the other hand, when the second clutch member 4b moves away from the pressure member 5 (in the direction of arrow DR1 in FIG. 2 ), the pressing force of the driving-side clutch plates 6 and the driven-side clutch plates 7 is released, and the first clutch member 4a and the second clutch member 4b no longer rotate with the rotation of the clutch housing 2, and the rotational force of the clutch housing 2 is no longer transmitted to the output shaft 3. The driving-side clutch plates 6 and the driven-side clutch plates 7 are provided so as to be movable in the axial direction of the output shaft 3 relative to the second clutch member 4b.

[0020] In this manner, when the drive-side clutch plates 6 and the driven-side clutch plates 7 are in pressure contact, the rotational force input to the clutch housing 2 (i.e., the driving force of the engine E) is transmitted to the drive wheels T (i.e., the transmission M) via the output shaft 3. Furthermore, when the drive-side clutch plates 6 and the driven-side clutch plates 7 are released from pressure contact, the rotational force input to the clutch housing 2 is not transmitted to the output shaft 3.

[0021] As shown in FIG. 2 , the centrifugal clutch means 9 has a weight member 10 that is movable from an inner diameter side position (see FIG. 14 ) to an outer diameter side position (see FIG. 16 ) by centrifugal force generated by rotation of the clutch housing 2. The centrifugal clutch means 9 is disposed on the opening side (right side in FIG. 2 ) of the clutch housing 2. The centrifugal clutch means 9 is disposed on the opposite side of the pressure member 5 across the drive side clutch plates 6 and the driven side clutch plates 7. In this example, the centrifugal clutch means 9 is disposed on the side of the pressure member 5 indicated by arrow DR1 in FIG. 2 . When the weight member 10 is in the outer diameter side position, the centrifugal clutch means 9 presses the drive side clutch plates 6 and the driven side clutch plates 7 together, enabling transmission of the driving force of the engine E to the drive wheels T. The centrifugal clutch means 9 is configured to apply a pressing force to the drive side clutch plates 6 and the driven side clutch plates 7 as the weight member 10 moves from the inner diameter side position to the outer diameter side position. The centrifugal clutch means 9 is configured so that, when the weight member 10 is in the inner diameter side position, the pressing force between the drive side clutch plate 6 and the driven side clutch plate 7 is released, thereby cutting off the transmission of the driving force of the engine E to the drive wheels T. In other words, the centrifugal clutch means 9 is configured so that, when the weight member 10 is in the inner diameter side position, the pressing force applied to the drive side clutch plate 6 and the driven side clutch plate 7 is released, thereby cutting off the transmission of the driving force of the engine E to the drive wheels T.

[0022] As shown in FIG. 6, the centrifugal clutch means 9 includes a plurality of weight members 10, a holding member 11 that holds the weight members 10 movably between an inner diameter side position and an outer diameter side position, a pressure contact member 12, and a plurality of biasing springs 13.

[0023] As shown in FIGS. 7 to 9 , the weight member 10 includes a main body 10h, a weight-member-side cam surface K1 formed on the main body 10h, a groove 10c formed on the main body 10h for holding the biasing spring 13 (see FIG. 6 ), and a sliding surface 10d formed on the main body 10h that is slidable against the sliding surface 11b (see FIG. 13 ) of the retaining member 11. The weight member 10 is housed in the retaining member 11. When no centrifugal force is applied, the weight member 10 is held in an inner diameter side position (see FIG. 14 ). When centrifugal force is applied, the weight member 10 moves radially outward against the biasing force of the biasing spring 13 and reaches an outer diameter side position (see FIG. 16 ). During the movement from the inner diameter side position to the outer diameter side position, the weight member 10 moves the clutch member 4 (here, the second clutch member 4b) toward the pressure member 5 (in the direction of arrow DR2 in FIG. 2 ). The weight member 10 is configured to press the driving side clutch plates 6 and the driven side clutch plates 7 together via the pressing member 12 as the weight member 10 moves from the inner diameter side position to the outer diameter side position. Note that the weight member 10 does not need to press the driving side clutch plates 6 and the driven side clutch plates 7 together via the pressing member 12 at the same time as it starts to move from the inner diameter side position to the outer diameter side position; the driving side clutch plates 6 and the driven side clutch plates 7 may be pressed together via the pressing member 12 after the weight member 10 has moved a predetermined distance from the inner diameter side position to the outer diameter side position.

[0024] As shown in FIG. 14 , the weight-member-side cam surface K1 is arranged to be able to contact the pressure-contact-member-side cam surface K2, which will be described later. The weight-member-side cam surface K1 is the portion that contacts the pressure-contact member 12. As shown in FIG. 9 , the weight member 10 has, on the weight-member-side cam surface K1, a first inclined surface 10a and a second inclined surface 10b, which has a larger inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 10a. The first inclined surface 10a is located radially outward of the second inclined surface 10b. The first inclined surface 10a is a flat surface. The second inclined surface 10b is a flat surface. The inclination angle α of the first inclined surface 10a with respect to the axial direction of the output shaft 3 is smaller than the inclination angle β of the second inclined surface 10b with respect to the axial direction of the output shaft 3. In this embodiment, the first inclined surface 10a and the second inclined surface 10b are continuous, but they may also be connected via a curved surface. As described above, the centrifugal clutch means 9 has a first inclined surface 10a and a second inclined surface 10b at a portion of the weight member 10 where the weight member 10 and the pressing member 12 contact each other (here, the weight member-side cam surface K1). When the engine speed increases by a predetermined number of revolutions and the weight member 10 moves a predetermined distance in the radial direction, the amount of axial movement of the pressing member 12 in the second inclined surface 10b is smaller than the amount of axial movement of the pressing member 12 in the first inclined surface 10a. The thrust of the weight member 10 generated at the second inclined surface 10b is greater than the thrust of the weight member 10 generated at the first inclined surface 10a. The first inclined surface 10a is an example of a first region. The second inclined surface 10b is an example of a second region.

[0025] As shown in Fig. 2, the holding member 11 holds the weight member 10 so that it can move between an inner diameter side position and an outer diameter side position. As shown in Fig. 13, the holding member 11 has an annular main body portion 11c, a wall portion 11a extending from the outer periphery of the main body portion 11c, and a sliding surface 11b on which the weight member 10 slides. The wall portion 11a comes into contact with one end of the biasing spring 13.

[0026] The pressing member 12 is provided so as to be able to come into contact with the weight member 10. The pressing member 12 is configured to move in a direction (the direction of arrow DR2 in FIG. 14 ) in which the driving-side clutch plate 6 and the driven-side clutch plate 7 are pressed together when the weight member 10 moves from an inner diameter side position (see FIG. 14 ) to an outer diameter side position (see FIG. 16 ). The pressing member 12 is configured so as to be able to press the driving-side clutch plate 6 and the driven-side clutch plate 7 together. As shown in FIGS. 10 to 12 , the pressing member 12 has an annular main body 12d, a plurality of pressing-member-side cam surfaces K2 formed around the circumferential direction of the main body 12d, a pressing surface 12c formed on the surface of the main body 12d opposite the surface on which the pressing-member-side cam surface K2 is formed, and a plurality of protrusions 12e formed around the circumferential direction of the main body 12d. The pressing member 12 is attached to the clutch housing 2 by fitting the protrusion 12e into the notch 2a (see FIG. 4) of the clutch housing 2. The pressing member 12 is provided so as to be movable in the axial direction of the clutch housing 2 (i.e., the axial direction of the output shaft 3). The pressing member 12 engages with the clutch housing 2 in the rotational direction and is provided so as to be rotatable together with the clutch housing 2.

[0027] As shown in FIG. 14 , the pressure-contact-member-side cam surface K2 is arranged to be able to come into contact with the weight-member-side cam surface K1. The pressure-contact-member-side cam surface K2 is the portion that comes into contact with the weight member 10. As shown in FIG. 12 , the pressure-contact-member 12 has, on the pressure-contact-member-side cam surface K2, a first inclined surface 12a and a second inclined surface 12b that has a larger inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 12a. The first inclined surface 12a is located radially inward of the second inclined surface 12b. The first inclined surface 12a is a flat surface. The second inclined surface 12b is a flat surface. The inclination angle α of the first inclined surface 12a with respect to the axial direction of the output shaft 3 is smaller than the inclination angle β of the second inclined surface 12b with respect to the axial direction of the output shaft 3. The first inclined surface 12a is arranged to be able to come into contact with the first inclined surface 10a of the weight-member-side cam surface K1. The second inclined surface 12b is arranged to be able to contact the second inclined surface 10b of the weight-member-side cam surface K1. In this embodiment, the first inclined surface 12a and the second inclined surface 12b are continuous, but they may be connected via a curved surface. Thus, the centrifugal clutch means 9 has the first inclined surface 12a and the second inclined surface 12b at a portion of the pressing member 12 where the weight member 10 and the pressing member 12 contact each other (here, the pressing member-side cam surface K2). When the engine speed increases by a predetermined number of revolutions and the weight member 10 moves a predetermined distance in the radial direction, the amount of axial movement of the pressing member 12 in the second inclined surface 12b is smaller than the amount of axial movement of the pressing member 12 in the output shaft 3 in the first inclined surface 12a. The thrust of the weight member 10 generated at the second inclined surface 12b is greater than the thrust of the weight member 10 generated at the first inclined surface 12a. The first inclined surface 12a is an example of a first region. The second inclined surface 12b is an example of a second region.

[0028] The thrust of the weight member 10 generated in the process of moving the weight member 10 from the inner diameter side position (see FIG. 14) to the outer diameter side position (see FIG. 16) is transmitted to the pressing member 12 via the weight member-side cam surface K1 and the pressing member-side cam surface K2. As a result, the pressing member 12 moves in a direction (the direction of arrow DR2 in FIG. 14) that presses the driving-side clutch plate 6 and the driven-side clutch plate 7 into contact with each other. As shown in FIGS. 14 to 16, the weight member-side cam surface K1 and the pressing member-side cam surface K2 are configured so that the inclined surface acting as a cam surface transitions from the first inclined surface 10a and the first inclined surface 12a to the second inclined surface 10b and the second inclined surface 12b in the process of moving the weight member 10 from the inner diameter side position (see FIG. 14) to the outer diameter side position (see FIG. 16). In the process of the weight member 10 moving from the inner diameter side position to the outer diameter side position, before the driving side clutch plate 6 and the driven side clutch plate 7 start to be pressed together, the first inclined surface 10a and the first inclined surface 12a act as cam surfaces, and after the driving side clutch plate 6 and the driven side clutch plate 7 start to be pressed together, the second inclined surface 10b and the second inclined surface 12b act as cam surfaces.

[0029] As shown in Figure 14, during the process of the weight member 10 moving from the inner diameter side position to the outer diameter side position, before the driving-side clutch plate 6 and the driven-side clutch plate 7 begin to press together, the first inclined surfaces 10a and 12a of the weight member-side cam surface K1 and the pressing member-side cam surface K2 contact and slide against each other. As a result, the thrust generated when the weight member 10 moves from the inner diameter side position to the outer diameter side position is transmitted to the pressing member 12 via the first inclined surfaces 10a and 12a. The pressing member 12 then moves in a direction that presses the driving-side clutch plate 6 and the driven-side clutch plate 7 together (the direction of arrow DR2 in Figure 14). At this time, the thrust of the weight member 10 transmitted to the pressing member 12 is relatively small, but the amount of axial movement of the pressing member 12 in the output shaft 3 is relatively large.

[0030] Then, as shown in Figure 15, when the weight member 10 moves further from the inner diameter side position to the outer diameter side position and the driving side clutch plate 6 and the driven side clutch plate 7 begin to be pressed together, the boundary between the first sloped surface 10a and the second sloped surface 10b of the weight member side cam surface K1 and the boundary between the first sloped surface 12a and the second sloped surface 12b of the pressing member side cam surface K2 come into contact with each other.

[0031] As shown in FIG. 16 , when the weight member 10 moves further from the inner diameter side position to the outer diameter side position, the second inclined surfaces 10b and 12b come into contact with each other and slide against each other after the weight member-side cam surface K1 and the pressure contact member-side cam surface K2 start to press the driving-side clutch plate 6 and the driven-side clutch plate 7 together. As a result, the thrust generated when the weight member 10 moves from the inner diameter side position to the outer diameter side position is transmitted to the pressure contact member 12 via the second inclined surfaces 10b and 12b. The pressure contact member 12 then moves further in the direction of pressing the driving-side clutch plate 6 and the driven-side clutch plate 7 together (the direction of arrow DR2 in FIG. 16 ). At this time, the amount of axial movement of the pressure contact member 12 in the output shaft 3 becomes relatively small, but the thrust of the weight member 10 transmitted to the pressure contact member 12 becomes relatively large.

[0032] It is also possible to configure the weight member 10 and the pressing member 12 to come into contact with each other at the first inclined surfaces 10a and 12a (i.e., come into contact with each other in a first region) and then come into contact with each other at the second inclined surfaces 10b and 12b (i.e., come into contact with each other in a second region) as the rotation speed of the engine E increases. Also, it is also possible to configure the weight member 10 and the pressing member 12 to come into contact with each other at the first inclined surfaces 10a and 12a (i.e., come into contact with each other in a first region) and then come into contact with each other at the second inclined surfaces 10b and 12b (i.e., come into contact with each other in a second region) when the rotation speed of the engine E is lower than the rotation speed at which the driving-side clutch plate 6 and the driven-side clutch plate 7 start to press together. The weight member 10 and the pressing member 12 may be configured to come into contact with each other at the first inclined surfaces 10a and 12a (i.e., come into contact with each other in a first region) and then come into contact with each other at the second inclined surfaces 10b and 12b (i.e., come into contact with each other in a second region) when the rotation speed of the engine E is lower than the rotation speed of the engine E when the pressing contact between the driving side clutch plates 6 and the driven side clutch plates 7 is completed. Note that the pressing contact between the driving side clutch plates 6 and the driven side clutch plates 7 is maintained in a region where the rotation speed of the engine E is higher than the rotation speed of the engine E when the pressing contact between the driving side clutch plates 6 and the driven side clutch plates 7 is completed.

[0033] Figure 39 is a graph showing the relationship between the rotation speed of the engine E and the amount of axial movement of the output shaft 3 of the pressing member 12. In Figure 39, the horizontal axis represents the rotation speed of the engine E, and the vertical axis represents the amount of axial movement of the output shaft 3 of the pressing member 12. Figure 40 is a graph showing the relationship between the rotation speed of the engine E and the thrust force produced by the weight member 10. In Figure 40, the horizontal axis represents the rotation speed of the engine E, and the vertical axis represents the thrust force produced by the weight member 10. In Figures 39 and 40, the rotation speed EID indicates the rotation speed of the engine E when it is idling, the rotation speed EC indicates the rotation speed of the engine E when the driving side clutch plates 6 and the driven side clutch plates 7 start to be pressed together (in this case, when the inclined surfaces acting as cam surfaces transition from the first inclined surfaces 10a and 12a to the second inclined surfaces 10b and 12b), the rotation speed EIN indicates the rotation speed of the engine E when the driving force of the engine E begins to be transmitted to the driving wheels T, the rotation speed EST indicates the rotation speed of the engine E when the driving side clutch plates 6 and the driven side clutch plates 7 are completely pressed together (when the pressing of the driving side clutch plates 6 and the driven side clutch plates 7 is completed), and the rotation speed EE indicates the rotation speed of the engine E when the weight member 10 reaches the outer diameter position. 39 and 40, when the rotation speed of the engine E is between rotation speed EID and rotation speed EC, the amount of movement LM1 of the output shaft 3 of the pressing member 12 in the axial direction is relatively large, and the thrust FM1 by the weight member 10 is relatively small. On the other hand, when the rotation speed of the engine E is between rotation speed EC and rotation speed EE, the amount of movement LM2 of the output shaft 3 of the pressing member 12 in the axial direction is relatively small (movement amount LM2<movement amount LM1), and the thrust FM2 by the weight member 10 is relatively large (thrust force FM2>thrust force FM1).

[0034] As described above, in the power transmission device K of this embodiment, the centrifugal clutch means 9 has, on the weight member side cam surface K1, the first inclined surfaces 10a, 12a and the second inclined surfaces 10b, 12b whose inclination angles relative to the axial direction of the output shaft 3 are larger than those of the first inclined surfaces 10a, 12a. According to the above aspect, the required amount of movement of the pressing member 12 in the axial direction of the output shaft 3 and the thrust force of the weight member 10 can be ensured depending on the operating state.

[0035] In the power transmission device K of this embodiment, the weight member 10 and the pressing member 12 may come into contact with each other at the first inclined surfaces 10 a, 12 a and then at the second inclined surfaces 10 b, 12 b as the rotation speed of the engine E increases. According to the above aspect, the amount of axial movement of the pressing member 12 is first increased, and then the thrust force by the weight member 10 can be increased.

[0036] In the power transmission device K of this embodiment, the first inclined surface 10a and the second inclined surface 10b may be connected via a curved surface, and the first inclined surface 12a and the second inclined surface 12b may be connected via a curved surface. According to the above aspect, the first inclined surface 10a and the second inclined surface 10b are connected via a curved surface, and the first inclined surface 12a and the second inclined surface 12b are connected via a curved surface, so that the contact portion between the weight member 10 and the pressure contact member 12 can be smoothly shifted from the first inclined surfaces 10a, 12a to the second inclined surfaces 10b, 12b.

[0037] In the power transmission device K of this embodiment, when the rotation speed of the engine E is lower than the rotation speed at which the driving-side clutch plate 6 and the driven-side clutch plate 7 start to be pressed together, the weight member 10 and the pressing member 12 may come into contact with each other at the first inclined surfaces 10 a, 12 a and then come into contact with each other at the second inclined surfaces 10 b, 12 b. According to the above aspect, when the rotation speed is lower than the rotation speed at which the driving-side clutch plate 6 and the driven-side clutch plate 7 start to be pressed together, the contact portion between the weight member 10 and the pressing member 12 is shifted from the first inclined surfaces 10 a, 12 a to the second inclined surfaces 10 b, 12 b. This makes it possible to ensure the necessary amount of axial movement of the pressing member 12 in the output shaft 3 before the driving-side clutch plate 6 and the driven-side clutch plate 7 start to be pressed together, and also ensures the necessary thrust by the weight member 10 after the driving-side clutch plate 6 and the driven-side clutch plate 7 start to be pressed together.

[0038] In the power transmission device K of this embodiment, when the rotation speed of the engine E is lower than the rotation speed at which the pressing contact between the driving-side clutch plate 6 and the driven-side clutch plate 7 is completed, the weight member 10 and the pressing member 12 may come into contact with each other at the first inclined surfaces 10a, 12a and then may come into contact with each other at the second inclined surfaces 10b, 12b. According to the above aspect, when the rotation speed is lower than the rotation speed at which the pressing contact between the driving-side clutch plate 6 and the driven-side clutch plate 7 is completed, the contact portion between the weight member 10 and the pressing member 12 is shifted from the first inclined surfaces 10a, 12a to the second inclined surfaces 10b, 12b. This makes it possible to ensure the necessary amount of axial movement of the pressing member 12 in the output shaft 3 until the pressing contact between the driving-side clutch plate 6 and the driven-side clutch plate 7 is completed, and also ensures the necessary thrust by the weight member 10 after the pressing contact between the driving-side clutch plate 6 and the driven-side clutch plate 7 is completed.

[0039] In the power transmission device K of this embodiment, the weight member 10 has a sliding surface 10d that is slidable relative to the holding member 11, and the weight member 10 may have a first inclined surface 10a and a second inclined surface 10b at a portion where the weight member 10 and the pressing member 12 contact each other (e.g., weight-member-side cam surface K1), and the pressing member 12 may have a first inclined surface 12a and a second inclined surface 12b at a portion where the weight member 10 and the pressing member 12 contact each other (e.g., pressing-member-side cam surface K2). According to the above aspect, the weight member 10 having the sliding surface 10d that is slidable relative to the holding member 11 can be effectively used.

[0040] Furthermore, in the power transmission device K of this embodiment, the centrifugal clutch means 9 has first inclined surfaces 10a, 12a as first regions, and second inclined surfaces 10b, 12b as second regions in which the amount of axial movement of the pressing member 12 in the output shaft 3 is smaller than in the first region. According to the above aspect, the necessary amount of axial movement of the pressing member 12 in the output shaft 3 and the thrust force of the weight member 10 can be ensured depending on the operating state. Note that the thrust force of the weight member 10 is greater in the second region than in the first region.

[0041] In the power transmission device K of this embodiment, the weight member 10 and the pressing member 12 may come into contact with each other at the first inclined surfaces 10 a, 12 a as the first region, and then come into contact with each other at the second inclined surfaces 10 b, 12 b as the second region, as the rotation speed of the engine E increases. According to the above aspect, the amount of axial movement of the pressing member 12 is first increased, and then the thrust force by the weight member 10 can be increased.

[0042] In the power transmission device K of this embodiment, the first region may be the first inclined surfaces 10a, 12a formed by flat surfaces, and the second region may be the second inclined surfaces 10b, 12b formed by flat surfaces, and the weight member 10 and the pressing member 12 may be configured to be able to come into contact with each other at the first inclined surfaces 10a, 12a and the second inclined surfaces 10b, 12b. According to the above aspect, the amount of movement of the pressing member 12 and the thrust force by the weight member 10 can be smoothly changed in the first region and the second region.

[0043] 21 to 23, a power transmission device 200K according to a second embodiment has a centrifugal clutch means 209 having a weight member 14. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0044] As shown in Figure 21, the centrifugal clutch means 209 has a plurality of weight members 14, a holding member 11 that holds the weight members 14 movably between an inner diameter side position and an outer diameter side position, a pressure contact member 15, and a plurality of biasing springs 13.

[0045] 18 to 20, weight member 14 is configured to be movable from an inner diameter side position (see FIG. 21) to an outer diameter side position (see FIG. 23) by centrifugal force accompanying rotation of clutch housing 2. Weight member 14 has a main body portion 14h, a spherical member 14a that is in point contact with or can move while rolling on retaining member 11, a retaining hole 14f formed in main body portion 14h and that retains spherical member 14a, and a groove portion 14b formed in main body portion 14h and that retains biasing spring 13. Spherical member 14a is an example of a contact portion.

[0046] The pressing member 15 is provided so as to be able to come into contact with the weight member 14. The pressing member 15 is configured to move in a direction (the direction of arrow DR2 in FIG. 21) in which the driving-side clutch plate 6 and the driven-side clutch plate 7 are pressed together when the weight member 14 moves from the inner diameter side position (see FIG. 21) to the outer diameter side position (see FIG. 23). The pressing member 15 is configured so as to be able to press the driving-side clutch plate 6 and the driven-side clutch plate 7 together. As shown in FIG. 21, the pressing member 15 has a pressing-member-side cam surface 200K2 formed around the circumferential direction of the main body portion 12d.

[0047] As shown in FIG. 21 , the pressure-contact member-side cam surface 200K2 is provided so as to be able to come into contact with the spherical member 14a. The pressure-contact member-side cam surface 200K2 is the portion that comes into contact with the weight member 14. The pressure-contact member 15 has a first sloped surface 15a and a second sloped surface 15b on the pressure-contact member-side cam surface 200K2, the second sloped surface 15b having a larger slope angle with respect to the axial direction of the output shaft 3 than the first sloped surface 15a. The first sloped surface 15a is located radially inward of the second sloped surface 15b. The first sloped surface 15a is a flat surface. The second sloped surface 15b is a curved surface. The first sloped surface 15a and the second sloped surface 15b are provided so as to be able to come into contact with the spherical member 14a. In this embodiment, the first sloped surface 15a and the second sloped surface 15b are continuous, but they may also be connected via a curved surface. When the engine speed increases by a predetermined number of revolutions and the weight member 10 moves a predetermined distance in the radial direction, the amount of axial movement of the pressing member 15 in the output shaft 3 at the second inclined surface 15b is smaller than the amount of axial movement of the pressing member 15 in the output shaft 3 at the first inclined surface 15a. Also, when the engine speed increases by a predetermined number of revolutions and the weight member 10 moves a predetermined distance in the radial direction, the thrust of the weight member 14 generated at the second inclined surface 15b is greater than the thrust of the weight member 14 generated at the first inclined surface 15a. The first inclined surface 15a is an example of a first region. The second inclined surface 15b is an example of a second region.

[0048] The thrust of the weight member 14, which is generated when the weight member 14 moves from the inner diameter side position (see FIG. 21) to the outer diameter side position (see FIG. 23), is transmitted to the pressing member 15 via the spherical member 14a and the pressing member side cam surface 200K2. As a result, the pressing member 15 moves in a direction (the direction of arrow DR2 in FIG. 21) that presses the driving side clutch plate 6 and the driven side clutch plate 7 into contact with each other. As shown in FIGS. 21 to 23, the spherical member 14a and the pressing member side cam surface 200K2 are configured so that the inclined surface that acts as a cam surface for the spherical member 14a transitions from the first inclined surface 15a to the second inclined surface 15b when the weight member 14 moves from the inner diameter side position (see FIG. 21) to the outer diameter side position (see FIG. 23). In the process of the weight member 14 moving from the inner diameter side position to the outer diameter side position, the first inclined surface 15a acts as a cam surface before the driving side clutch plate 6 and the driven side clutch plate 7 start to be pressed together, and after the driving side clutch plate 6 and the driven side clutch plate 7 start to be pressed together, the second inclined surface 15b acts as a cam surface.

[0049] As shown in Figure 21 , during the process of the weight member 14 moving from the inner diameter side position to the outer diameter side position, before the driving-side clutch plates 6 and the driven-side clutch plates 7 begin to press together, the spherical member 14a and the first inclined surface 15a of the pressing member-side cam surface K2 contact and slide against each other. As a result, the thrust generated when the weight member 14 moves from the inner diameter side position to the outer diameter side position is transmitted to the pressing member 15 via the spherical member 14a and the first inclined surface 15a. The pressing member 15 then moves in a direction that presses the driving-side clutch plates 6 and the driven-side clutch plates 7 together (the direction of arrow DR2 in Figure 21 ). At this time, the thrust of the weight member 14 transmitted to the pressing member 15 is relatively small, but the amount of axial movement of the pressing member 15 in the output shaft 3 is relatively large.

[0050] Then, as shown in Figure 22, when the weight member 14 moves further from the inner diameter side position to the outer diameter side position and the driving side clutch plate 6 and the driven side clutch plate 7 begin to be pressed together, the spherical member 14a and the boundary between the first inclined surface 15a and the second inclined surface 15b of the pressing member side cam surface 200K2 come into contact with each other.

[0051] 23 , when the weight member 14 moves further from the inner diameter side position to the outer diameter side position, the spherical member 14a and the second inclined surface 15b come into contact with each other and slide against each other after the spherical member 14a and the pressing member-side cam surface 200K2 start to press the driving-side clutch plate 6 and the driven-side clutch plate 7 together. As a result, the thrust generated when the weight member 14 moves from the inner diameter side position to the outer diameter side position is transmitted to the pressing member 15 via the spherical member 14a and the second inclined surface 15b. The pressing member 15 then moves further in the direction of pressing the driving-side clutch plate 6 and the driven-side clutch plate 7 together (the direction of arrow DR2 in FIG. 23 ). At this time, the amount of axial movement of the pressing member 15 in the output shaft 3 becomes relatively small, but the thrust of the weight member 14 transmitted to the pressing member 15 becomes relatively large.

[0052] In the power transmission device 200K of this embodiment, the weight member 14 has a spherical member 14a that is movable while making point contact with the holding member 11, and the pressure contact member 15 has a first inclined surface 15a and a second inclined surface 15b on the pressure contact member side cam surface 200K2. According to the above aspect, the weight member 14 having the spherical member 14a that is movable while making point contact with the holding member 11 can be effectively used.

[0053] 27 to 29, a power transmission device 300K according to a third embodiment has a centrifugal clutch means 309 having a weight member 16. Note that the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0054] As shown in Figures 24 to 26, the weight member 16 is configured to be movable from an inner diameter side position (see Figure 27) to an outer diameter side position (see Figure 29) due to centrifugal force generated by rotation of the clutch housing 2. The weight member 16 has a main body portion 16h, a pair of rolling members 16a, 16b that are movable while making point contact or rolling with respect to the holding member 11, a retaining hole 16f formed in the main body portion 16h and holding the rolling members 16a, 16b, and a groove portion 16c formed in the main body portion 16h and holding the biasing spring 13. The rolling member 16a is arranged to be able to come into contact with the pressure contact member side cam surface 200K2. The rolling member 16b is arranged to be able to come into contact with the holding member 11. The rolling members 16a, 16b are held in the retaining hole 16f so as to be in contact with each other. The rolling members 16a, 16b are an example of a contact portion.

[0055] The thrust of the weight member 16, which is generated in the process of the weight member 16 moving from the inner diameter side position (see FIG. 27) to the outer diameter side position (see FIG. 29), is transmitted to the pressing member 15 via the rolling members 16a, 16b and the pressing member side cam surface 200K2. As a result, the pressing member 15 moves in a direction (the direction of arrow DR2 in FIG. 27) that presses the driving side clutch plate 6 and the driven side clutch plate 7 into contact with each other. As shown in FIGS. 27 to 29, the rolling member 16a and the pressing member side cam surface 200K2 are configured so that the inclined surface that acts as a cam surface with respect to the rolling member 16a transitions from the first inclined surface 15a to the second inclined surface 15b in the process of the weight member 16 moving from the inner diameter side position (see FIG. 27) to the outer diameter side position (see FIG. 29). In the process of the weight member 16 moving from the inner diameter side position to the outer diameter side position, the first inclined surface 15a acts as a cam surface before the driving side clutch plates 6 and the driven side clutch plates 7 start to be pressed together, and the second inclined surface 15b acts as a cam surface after the driving side clutch plates 6 and the driven side clutch plates 7 start to be pressed together. The functions and effects of the third embodiment are similar to those of the second embodiment.

[0056] Although the preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples, and the present invention can be embodied in various other forms.

[0057] <Fourth Embodiment> In the first embodiment described above, the centrifugal clutch means 9 is disposed on the opening side of the clutch housing 2 (right side in FIG. 2 ), but this is not limited thereto. For example, in a power transmission device 400K according to a fourth embodiment, as shown in FIGS. 30 to 32 , the centrifugal clutch means 9 may be disposed on the bottom side of the clutch housing 2 (left side in FIG. 30 ). The centrifugal clutch means 9 is disposed on the opposite side of the pressure member 5 with the driving-side clutch plate 6 and the driven-side clutch plate 7 interposed therebetween. In this embodiment, the centrifugal clutch means 9 is disposed on the side of the clutch member 4 (more specifically, the second clutch member 4b) in the direction of arrow DR2 in FIG.

[0058] Fifth Embodiment In the second embodiment described above, the centrifugal clutch means 209 is disposed on the opening side of the clutch housing 2 (the right side in FIG. 21 ), but this is not limiting. For example, in a power transmission device 500K according to a fifth embodiment, as shown in FIGS. 33 to 35 , the centrifugal clutch means 209 may be disposed on the bottom side of the clutch housing 2 (the left side in FIG. 33 ). The centrifugal clutch means 209 is disposed on the opposite side of the pressure member 5 across the driving-side clutch plate 6 and the driven-side clutch plate 7. In this embodiment, the centrifugal clutch means 209 is disposed on the side of the clutch member 4 (more specifically, the second clutch member 4b) in the direction of arrow DR2 in FIG. 33 .

[0059] Sixth Embodiment In the third embodiment described above, the centrifugal clutch means 309 was disposed on the opening side of the clutch housing 2 (right side in FIG. 27 ), but this is not limited thereto. For example, in a power transmission device 600K according to a sixth embodiment, as shown in FIGS. 36 to 38 , the centrifugal clutch means 309 may be disposed on the bottom side of the clutch housing 2 (left side in FIG. 36 ). The centrifugal clutch means 309 is disposed on the opposite side of the pressure member 5 across the driving-side clutch plate 6 and the driven-side clutch plate 7. In this embodiment, the centrifugal clutch means 309 is disposed on the side of the clutch member 4 (more specifically, the second clutch member 4b) in the direction of arrow DR2 in FIG.

[0060] In the above-described embodiment, the centrifugal clutch means 9 has the first inclined surface 10a and the second inclined surface 10b on the weight-member-side cam surface K1 and the first inclined surface 12a and the second inclined surface 12b on the pressure-contact-member-side cam surface K2, but is not limited to this. The centrifugal clutch means 9 may have the first inclined surface 10a and the second inclined surface 10b on the weight-member-side cam surface K1, but may not have the first inclined surface 12a and the second inclined surface 12b on the pressure-contact-member-side cam surface K2. Furthermore, the centrifugal clutch means 9 may not have the first inclined surface 10a and the second inclined surface 10b on the weight-member-side cam surface K1, but may have the first inclined surface 12a and the second inclined surface 12b on the pressure-contact-member-side cam surface K2.

[0061] In the above-described embodiment, the first inclined surface 10a, the second inclined surface 10b, the first inclined surface 12a, and the second inclined surface 12b are each flat, but they may also be curved. Furthermore, if at least one of the first inclined surface 10a and the second inclined surface 10b is curved, it is preferable that it has a convex shape facing outward (e.g., toward the direction of arrow DR2 in FIG. 14 ). If at least one of the first inclined surface 12a and the second inclined surface 12b is curved, it is preferable that it has a convex shape facing outward (e.g., toward the direction of arrow DR1 in FIG. 14 ).

[0062] In the above-described embodiment, the weight member 10 has, on the weight-member-side cam surface K1, the first inclined surface 10a and the second inclined surface 10b, which has a larger inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 10a. However, this is not limited to this. The weight member 10 may also have a third inclined surface, which is located radially outward of the first inclined surface 10a and has a smaller inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 10a. Furthermore, the weight member 10 may also have a fourth inclined surface, which is located radially inward of the second inclined surface 10b and has a larger inclination angle with respect to the axial direction of the output shaft 3 than the second inclined surface 10b.

[0063] In the above-described embodiment, the pressing member 12 has, on the pressing member-side cam surface K2, the first inclined surface 12a and the second inclined surface 12b, which has a larger inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 12a. However, this is not limited to this. The pressing member 12 may also have a third inclined surface, which is located radially inward of the first inclined surface 12a and has a smaller inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 12a. The pressing member 12 may also have a fourth inclined surface, which is located radially outward of the second inclined surface 12b and has a larger inclination angle with respect to the axial direction of the output shaft 3 than the second inclined surface 12b.

[0064] In the above-described embodiment, the pressing member 15 has, on the pressing member-side cam surface 200K2, the first inclined surface 15a and the second inclined surface 15b, which has a larger inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 15a. However, this is not limited to this. The pressing member 15 may also have a third inclined surface, which is located radially inward of the first inclined surface 15a and has a smaller inclination angle with respect to the axial direction of the output shaft 3 than the first inclined surface 15a. The pressing member 15 may also have a fourth inclined surface, which is located radially outward of the second inclined surface 15b and has a larger inclination angle with respect to the axial direction of the output shaft 3 than the second inclined surface 15b.

[0065] In the above-described embodiment, all of the driven clutch plates 7 are held by the clutch member 4 (e.g., the second clutch member 4b), but this is not limiting. For example, some of the driven clutch plates 7 may be held by the clutch member 4 (e.g., the second clutch member 4b), and other parts of the driven clutch plates 7 may be held by the pressure member 5. In this case, the other parts of the driven clutch plates 7 are configured to be movable along the axial direction of the pressure member 5 (i.e., the axial direction of the output shaft 3) and to be rotatable integrally with the pressure member 5.

[0066] In each of the above-described embodiments, the engine E is used as the drive source, but the drive source is not limited to the engine E and may be, for example, an electric motor or the like.

[0067] The power transmission devices of the above-described embodiments can be applied to various multi-plate clutch power transmission devices such as automobiles, three-wheeled or four-wheeled buggies, and general-purpose machines in addition to motorcycles.

[0068] DESCRIPTION OF SYMBOLS 1 Input gear (input member) 2 Clutch housing 3 Output shaft (output member) 4 Clutch member 4a First clutch member 4b Second clutch member 5 Pressure member 6 Driving side clutch plate 7 Driven side clutch plate 9 Centrifugal clutch means 10 Weight member 10a First inclined surface 10b Second inclined surface 11 Holding member 12 Pressing member 12a First inclined surface 12b Second inclined surface 14 Weight member 14a Spherical member (contact portion) 15 Pressing member 15a First inclined surface 15b Second inclined surface 16 Weight members 16a, 16b Rolling member (contact portion) K Power transmission device K1 Weight member side cam surface K2 Pressing member side cam surface

Claims

1. a clutch member that rotates together with an input member that rotates by a driving force of a driving source, that is housed in a clutch housing that holds a plurality of driving side clutch plates, and that is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be capable of approaching or separating from the clutch member and that is capable of pressing a plurality of driven-side clutch plates that are alternately arranged with the driving-side clutch plates and the plurality of driving-side clutch plates; a centrifugal clutch means having a weight member movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying rotation of the clutch housing, and a pressing member provided to be in contact with the weight member and moving in a direction to press the driving side clutch plate and the driven side clutch plate together as the weight member moves from the inner diameter side position to the outer diameter side position, the centrifugal clutch means pressing the driving side clutch plate and the driven side clutch plate together when the weight member is in the outer diameter side position, thereby enabling the driving force of the driving source to be transmitted to the wheels, and releasing the pressing force between the driving side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby interrupting the transmission of the driving force of the driving source to the wheels, the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member during a process in which the weight member moves from the inner diameter side position to the outer diameter side position, a centrifugal clutch means for connecting the weight member to the pressure contact member, the centrifugal clutch means including a first inclined surface and a second inclined surface having a larger inclination angle with respect to the axial direction of the output member than the first inclined surface at a portion of the weight member where the weight member and the pressure contact member contact each other.

2. 2. The power transmission device according to claim 1, wherein, in the process of increasing the rotational speed of the drive source, the weight member and the pressure contact member come into contact with each other at the first inclined surface and then come into contact with each other at the second inclined surface.

3. The power transmission device according to claim 1 , wherein the first inclined surface and the second inclined surface are connected via a curved surface.

4. 3. The power transmission device according to claim 1, wherein when the rotation speed of the driving source is lower than the rotation speed at which the driving side clutch plate and the driven side clutch plate begin to be pressed against each other, the weight member and the pressing member come into contact with each other at the first inclined surface and then come into contact with each other at the second inclined surface.

5. 3. The power transmission device according to claim 1, wherein when the rotational speed of the driving source is lower than the rotational speed at which the pressing between the driving side clutch plate and the driven side clutch plate is completed, the weight member and the pressing member come into contact with each other at the first inclined surface and then come into contact with each other at the second inclined surface.

6. the centrifugal clutch means has a holding member that holds the weight member movably between the inner diameter side position and the outer diameter side position, the weight member has a sliding surface that is slidable relative to the holding member, The weight member has the first inclined surface and the second inclined surface, 3. The power transmission device according to claim 1, wherein the pressing member has the first inclined surface and the second inclined surface at a portion where the weight member and the pressing member contact each other.

7. the centrifugal clutch means has a holding member that holds the weight member movably between the inner diameter side position and the outer diameter side position, the weight member has a contact portion that is in point contact with the holding member or that is movable while rolling, 3. The power transmission device according to claim 1, wherein the pressing member has the first inclined surface and the second inclined surface at a portion where the weight member and the pressing member contact each other.

8. a clutch member that rotates together with an input member that rotates by a driving force of a driving source, that is housed in a clutch housing that holds a plurality of driving side clutch plates, and that is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be capable of approaching or separating from the clutch member and that is capable of pressing a plurality of driven-side clutch plates that are alternately arranged with the driving-side clutch plates and the plurality of driving-side clutch plates; a centrifugal clutch means having a weight member movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying rotation of the clutch housing, and a pressing member provided to be in contact with the weight member and moving in a direction to press the driving side clutch plate and the driven side clutch plate together as the weight member moves from the inner diameter side position to the outer diameter side position, the centrifugal clutch means pressing the driving side clutch plate and the driven side clutch plate together when the weight member is in the outer diameter side position, thereby enabling the driving force of the driving source to be transmitted to the wheels, and releasing the pressing force between the driving side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby interrupting the transmission of the driving force of the driving source to the wheels, the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member during a process in which the weight member moves from the inner diameter side position to the outer diameter side position, the centrifugal clutch means having a first region at a portion of the weight member where the weight member and the pressure contact member contact each other, and a second region in which an amount of movement of the pressure contact member in the axial direction of the output member is smaller than that of the first region.

9. 9. The power transmission device according to claim 8, wherein, in the process of increasing the rotational speed of the drive source, the weight member and the pressure contact member come into contact with each other in the first region, and then come into contact with each other in the second region.

10. The first region is a first inclined surface formed of a flat surface, the second region is a second inclined surface formed of a flat surface, 10. The power transmission device according to claim 8, wherein the weight member and the pressure contact member are configured to be able to come into contact with each other at the first inclined surface and the second inclined surface.

11. a clutch member that rotates together with an input member that rotates by a driving force of a driving source, that is housed in a clutch housing that holds a plurality of driving side clutch plates, and that is connected to an output member that can rotate a wheel; a pressure member that is provided so as to be capable of approaching or separating from the clutch member and that is capable of pressing a plurality of driven-side clutch plates that are alternately arranged with the driving-side clutch plates and the plurality of driving-side clutch plates; a centrifugal clutch means having a weight member movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying rotation of the clutch housing, and a pressing member provided to be in contact with the weight member and moving in a direction to press the driving side clutch plate and the driven side clutch plate together as the weight member moves from the inner diameter side position to the outer diameter side position, the centrifugal clutch means pressing the driving side clutch plate and the driven side clutch plate together when the weight member is in the outer diameter side position, thereby enabling the driving force of the driving source to be transmitted to the wheels, and releasing the pressing force between the driving side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby interrupting the transmission of the driving force of the driving source to the wheels, the weight member is configured to press the driving side clutch plate and the driven side clutch plate together via the pressing member during a process in which the weight member moves from the inner diameter side position to the outer diameter side position, a centrifugal clutch means for connecting the weight member to the pressing member, the centrifugal clutch means including a first region and a second region in which the thrust force exerted by the weight member is greater than that exerted by the first region at a portion of the weight member where the weight member and the pressing member contact each other.

12. 12. The power transmission device according to claim 11, wherein, in a process in which the rotation speed of the drive source increases, the weight member and the pressure contact member come into contact with each other in the first region, and then come into contact with each other in the second region.

13. The first region is a first inclined surface formed of a flat surface, the second region is a second inclined surface formed of a flat surface, 13. The power transmission device according to claim 11, wherein the weight member and the pressure contact member are configured to be able to come into contact with each other at the first inclined surface and the second inclined surface.