Power transmission device

Abstract

To provide a power transmission device capable of suppressing unintentional power transmission when a rotation speed of a power source is below or equal to a predetermined value.SOLUTION: A power transmission device comprises a clutch member 4 which holds a plurality of driven-side clutch plates arranged alternately with a drive-side clutch plate. The clutch member 4 has: a through hole 4ac connected to an output shaft; an outer peripheral wall which is positioned radially outward of the through hole 4ac and extends in a circumferential direction and a shaft direction of the output shaft; and a boss section 4ad which extends in the shaft direction and has an insertion hole for a bolt to be inserted. A radial outer end of the boss section 4ad is connected to the outer peripheral wall, while a radial inner end of the boss section 4ad is positioned radially inward relative to the outer peripheral wall.SELECTED DRAWING: Figure 5B

Description

[Technical Field]

[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. [Background technology]

[0002] As a conventional power transmission device, for example, Patent Document 1 discloses a centrifugal clutch means provided with a weight member that can press the driving clutch plates and the driven clutch plates together by moving from an inner diameter side position to an outer diameter side position due to centrifugal force caused by rotation of the clutch housing. 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, causing the driving clutch plates and the driven clutch plates to press together, thereby transmitting the driving force of the engine to the wheels.

[0003] Furthermore, the conventional power transmission device described above is provided with a pressure contact force amplification mechanism that generates a cam thrust that amplifies the pressure contact force between the drive-side clutch plate and the driven-side clutch plate when the rotational force input to the input member is ready to be transmitted to the output member. As a result, when the driver operates the clutch to press the drive-side clutch plate and the driven-side clutch plate into pressure contact, the operating force can be reduced, ensuring smooth power transmission. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 183588 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional power transmission device, when the engine speed of the vehicle is below a predetermined speed (for example, when the vehicle is stopped with the engine running), there is a risk that the pressure contact force amplification mechanism will inadvertently operate due to drag torque between the drive side clutch plate and the driven side clutch plate, causing the drive side clutch plate and the driven side clutch plate to come into pressure contact, resulting in unintended power transmission.

[0006] In particular, when applied to a small vehicle with a large primary ratio, the centrifugal force that can be generated by the weight member of the centrifugal clutch means is relatively small compared to when applied to a large vehicle, and there is a risk that a sufficient pressure contact force between the drive-side clutch plate and the driven-side clutch plate cannot be secured, resulting in insufficient power transmission. Therefore, it is necessary to use a pressure contact force amplification mechanism to amplify the pressure contact force, but in that case, as mentioned above, there is a risk that the pressure contact force amplification mechanism will be activated inadvertently, causing the drive-side clutch plate and the driven-side clutch plate to come into pressure contact, resulting in unintended power transmission.

[0007] The present invention has been made in consideration of these points, and its purpose is to provide a power transmission device that can prevent unintended power transmission when the rotation speed of the drive source is below a predetermined rotation speed. [Means for solving the problem]

[0008] The 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 driving source and is housed in a clutch housing that holds a plurality of driving-side clutch plates, is connected to an output member that can rotate a wheel, and holds a plurality of driven-side clutch plates that are arranged alternately with the driving-side clutch plates, and a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force that accompanies the rotation of the clutch housing, and when the weight member is in the outer diameter side position, presses the driving-side clutch plates and the driven-side clutch plates together to transmit the driving force of the driving source. a centrifugal clutch means for releasing the pressure contact force between the drive side clutch plate and the driven side clutch plate when the weight member is in the inner diameter side position, thereby cutting off the transmission of the driving force of the drive source to the wheel; a pressure contact force amplifying mechanism for generating a cam thrust that amplifies the pressure contact force between the drive side clutch plate and the driven side clutch plate when the rotational force input to the input member is in a state where it can be transmitted to the output member; and a suppression member for suppressing the generation of the cam thrust when the rotational speed of the drive source is equal to or lower than a predetermined rotational speed.

[0009] The power transmission device according to the present invention includes a suppression member that suppresses the generation of cam thrust when the rotation speed of the drive source is equal to or lower than a predetermined rotation speed. According to the above aspect, when the rotation speed of the drive source is equal to or lower than the predetermined rotation speed, the suppression member suppresses the generation of cam thrust by the contact pressure force amplification mechanism, thereby preventing the contact pressure force amplification mechanism from accidentally operating and causing unintended power transmission.

[0010] Another 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 and is housed in a clutch housing that holds a plurality of driving side clutch plates; the clutch member is connected to an output member that can rotate a wheel and holds a plurality of driven side clutch plates arranged alternately with the driving side clutch plates; a centrifugal clutch means that has a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying the rotation of the clutch housing, and when the weight member is in the outer diameter side position, presses the driving side clutch plates and the driven side clutch plates together to enable the driving force of the drive source to be transmitted to the wheel, and when the weight member is in the inner diameter side position, releases the pressing force between the driving side clutch plates and the driven side clutch plates to interrupt the transmission of the driving force of the drive source to the wheel; and a suppression member that presses the driving side clutch plates and the driven side clutch plates together to suppress the transmission of the driving force of the drive source to the wheel when the rotation speed of the drive source is below a predetermined rotation speed.

[0011] Another power transmission device according to the present invention includes a suppression member that suppresses the transmission of the driving force of the drive source to the wheels by bringing the drive-side clutch plate and the driven-side clutch plate into pressure contact when the rotation speed of the drive source is equal to or lower than a predetermined rotation speed. According to the above aspect, when the rotation speed of the drive source is equal to or lower than the predetermined rotation speed, the suppression member suppresses the transmission of the driving force of the drive source to the wheels, thereby suppressing unintended power transmission. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a power transmission device that can prevent unintended power transmission when the rotation speed of a drive source is equal to or lower than a predetermined rotation speed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an external view showing a power transmission device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view showing the clutch housing according to the first embodiment. [Figure 5A] FIG. 5A is a plan view of the clutch member according to the first embodiment. [Figure 5B] FIG. 5B is an exploded perspective view of the clutch member according to the first embodiment. [Figure 6] FIG. 6 is a three-view diagram showing the first clutch member according to the first embodiment. [Figure 7] FIG. 7 is a perspective view showing the first clutch member according to the first embodiment. [Figure 8] FIG. 8 is a three-view diagram showing the second clutch member according to the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a three-view diagram showing the pressure member according to the first embodiment. [Figure 11] FIG. 11 is a three-view diagram showing the centrifugal clutch means according to the first embodiment. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13] FIG. 13 is a perspective view showing the centrifugal clutch means according to the first embodiment. [Figure 14] FIG. 14 is a schematic view showing a vehicle to which the power transmission device according to the first embodiment is applied. [Figure 15] FIG. 15 is a cross-sectional view showing a state in which the weight member of the centrifugal clutch means according to the first embodiment has started to move from the inner diameter side position toward the outer diameter side position (a state in which the suppression by the suppression means has been released). [Figure 16] FIG. 16 is a cross-sectional view showing a process in which the weight member of the centrifugal clutch means according to the first embodiment moves from the inner diameter side position to the outer diameter side position (the amplifying cam operates). [Figure 17]FIG. 17 is a cross-sectional view showing a state in which the weight member of the centrifugal clutch means according to the first embodiment has reached the outer diameter side position. [Figure 18] FIG. 18 is a schematic diagram showing a state in which the operation of the amplifying cam according to the first embodiment is suppressed. [Figure 19] FIG. 19 is a schematic diagram showing a state in which the suppression of the operation of the amplifying cam according to the first embodiment is released. [Figure 20] FIG. 20 is a schematic diagram showing a state in which the amplifying cam according to the first embodiment is operating. [Figure 21] FIG. 21 is a schematic diagram showing a state in which the operation of the amplifying cam according to the first embodiment is completed. [Figure 22] FIG. 22 is a schematic diagram showing a state in which the back torque limiter cam according to the first embodiment is in operation. [Figure 23] FIG. 23 is an external view showing a power transmission device according to the second embodiment. [Figure 24] FIG. 24 is a cross-sectional view taken along line XXIV-XXIV in FIG. [Figure 25] FIG. 25 is an exploded perspective view showing the first clutch member and the second clutch member according to the second embodiment. [Figure 26] FIG. 26 is an exploded perspective view showing the first clutch member and the second clutch member according to the second embodiment. [Figure 27] FIG. 27 is a three-view diagram showing the first clutch member according to the second embodiment. [Figure 28] FIG. 28 is a cross-sectional view showing a state in which the weight member of the centrifugal clutch means according to the second embodiment has started to move from the inner diameter side position toward the outer diameter side position (a state in which the suppression by the suppression means has been released). [Figure 29] FIG. 29 is a cross-sectional view showing the process in which the weight member of the centrifugal clutch means according to the second embodiment moves from the inner diameter side position to the outer diameter side position (the amplifying cam operates). [Figure 30] FIG. 30 is a cross-sectional view showing a state in which the weight member of the centrifugal clutch means according to the second embodiment has reached the outer diameter side position. [Figure 31]FIG. 31 is a graph showing the relationship between the engine speed and each member. [Figure 32] FIG. 32 is a plan view of a clutch member according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] First Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 14, a power transmission device K is disposed in a vehicle and is used to transmit or interrupt the driving force of an engine E to driving wheels W via a transmission M. The engine E is an example of a driving source. The driving wheels W are an example of wheels. As shown in FIGS. 1 to 13, 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 assembled in a stacked state, and a centrifugal clutch means 9 having a weight member 10. Note that the symbol S in the drawings indicates a clutch spring. The clutch spring S biases the pressure member 5 in a direction approaching the clutch member 4 (the direction of arrow DR1 in FIG. 2). 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 the clutch housing 2 by rivets or the like. The clutch housing 2 is formed in a cylindrical shape with an opening on the right end side in Figures 2 and 3. The clutch housing 2 rotates together with the input gear 1 due to the driving force of the engine E.

[0016] As shown in Figure 4, 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 rotate together with the rotation of the clutch housing 2 and are configured to be movable in the axial direction of the output shaft 3 (i.e., the left-right direction in Figures 2 and 3).

[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 W via a transmission M of the vehicle. As shown in FIGS. 5A and 5B, 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 FIGS. 5A to 7, the first clutch member 4a has an insertion hole 4ac formed in the center. The output shaft 3 is inserted into the insertion hole 4ac, and the gears formed therein mesh with each other to couple in the direction of rotation. That is, the first clutch member 4a is coupled to the output shaft 3. The first clutch member 4a has a plurality of recesses A arranged in the circumferential direction. The recesses A are formed on the outer peripheral surface of the first clutch member 4a. The recesses A include a first inclined surface 4aa constituting a pressure-contact assist cam and a third inclined surface 4ab constituting a back torque limiter cam. The first clutch member 4a has a boss portion 4ad. The boss portion 4ad has an insertion hole through which a bolt B for coupling the first clutch member 4a and the fixed member 8 is inserted. The first clutch member 4a has a plurality of through holes 4ag arranged in the circumferential direction, which penetrate in the axial direction of the output shaft 3. The through holes 4ag are located radially outward of the insertion hole 4ac. The through holes 4ag are arranged between adjacent boss portions 4ad.

[0019] As shown in FIG. 8, the second clutch member 4b has an outer peripheral wall 4be formed in an annular shape and a flange portion 4bd extending radially outward from the outer peripheral wall 4be. A splined engagement portion 4bc is formed on the outer peripheral wall 4be. The driven-side clutch plates 7 are attached to the splined engagement portion 4bc by spline engagement. That is, the second clutch member 4b holds the driven-side clutch plates 7. The second clutch member 4b is configured to be movable in the axial direction of the output shaft 3. As will be described later, the second clutch member 4b is configured to be movable in a direction approaching the pressure member 5 (the direction of arrow DR2 in FIG. 2) by the biasing force of the weight member 10 when a suppression member D (described later) suppresses the generation of the second pressing force. The second clutch member 4b has a plurality of protrusions T arranged circumferentially and capable of being fitted into the recesses A. As shown in FIG. 9, the protrusions T are formed with a second inclined surface 4ba constituting a pressing-assist cam and a fourth inclined surface 4bb constituting a back torque limiter cam.

[0020] As shown in FIG. 10 , the pressure member 5 is a disk-shaped member with a flange portion 5a formed on its periphery. The pressure member 5 is configured 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 drive-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 4bd of the second clutch member 4b. When the second clutch member 4b moves in a direction approaching the pressure member 5 (the direction of arrow DR2 in FIG. 2 ), the drive-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 in a direction away from the pressure member 5 (the direction of arrow DR1 in Figure 2), the pressure contact force between the driving side clutch plate 6 and the driven side clutch plate 7 is released, the first clutch member 4a and the second clutch member 4b no longer follow 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.

[0021] In this way, when the driving 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 driving wheels (i.e., the transmission M) via the output shaft 3. On the other hand, when the pressure contact between the driving side clutch plates 6 and the driven side clutch plates 7 is released, the rotational force input to the clutch housing 2 is not transmitted to the output shaft 3.

[0022] When the first clutch member 4a and the second clutch member 4b are engaged with each other, the protrusion T fits into the recess A. When the first clutch member 4a and the second clutch member 4b are engaged with each other, the first inclined surface 4aa and the second inclined surface 4ba face each other to form a pressure-contact assist cam, and the third inclined surface 4ab and the fourth inclined surface 4bb face each other to form a back torque limiter cam. As shown in Figure 8, the protrusion T is formed with an accommodating recess Ta that accommodates a coil spring D2 (see Figure 3), which will be described later.

[0023] The power transmission device K is equipped with a contact pressure amplification mechanism 20 (see FIG. 18). The contact pressure amplification mechanism 20 generates a second contact pressure that amplifies the contact pressure between the drive-side clutch plate 6 and the driven-side clutch plate 7 as the rotation speed of the engine E increases. The second contact pressure is an example of a cam thrust. The contact pressure amplification mechanism 20 generates the second contact pressure that amplifies the contact pressure between the drive-side clutch plate 6 and the driven-side clutch plate 7 when the rotational force input to the input gear 1 can be transmitted to the output shaft 3. The contact pressure amplification mechanism 20 is configured to generate the second contact pressure by moving a part of the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 (in the direction of arrow DR2 in FIG. 2). The pressing force amplification mechanism 20 is configured to generate a second pressing force by causing a part of the clutch member 4 (here, the second clutch member 4b) to move toward the pressure member 5 while rotating in a first circumferential direction S1 (see FIG. 5A) around the axis 3C (see FIG. 5A) of the output shaft 3. The pressing force amplification mechanism 20 applies the second pressing force to the driving-side clutch plate 6 and the driven-side clutch plate 7 in the direction of arrow DR2 in FIG. 2 (leftward in FIG. 2). The pressing force amplification mechanism 20 has a plurality of amplifier cams 22. The amplifier cams 22 generate the second pressing force. The amplifier cams 22 are provided at portions where the first clutch member 4a and the second clutch member 4b can come into contact with each other. The amplifier cams 22 are formed on the recess A of the first clutch member 4a and the protrusion T of the second clutch member 4b. The amplifying cam 22 includes a first inclined surface 4aa formed in the recess A and a second inclined surface 4ba formed in the protruding portion T and sliding on the first inclined surface 4aa. The second pressing force is generated by the operation of the amplifying cam 22 (i.e., by the sliding of the first inclined surface 4aa and the second inclined surface 4ba). In this embodiment, the pressing force amplifying mechanism 20 has six amplifying cams 22. Note that the number of amplifying cams 22 is not limited to six. The amplifying cams 22 are an example of a first cam.

[0024] 20, when the rotation speed of the engine E increases and the rotational force input to the input gear 1 and the clutch housing 2 can be transmitted to the output shaft 3 via the first clutch member 4a and the second clutch member 4b (i.e., when the weight member 10 is located at the outer diameter side position), a rotational force in the direction of arrow a in FIG. 20 is applied to the second clutch member 4b. As a result, the first inclined surface 4aa and the second inclined surface 4ba slide against each other, the amplifying cam 22 is actuated, and a force in the direction of arrow c in FIG. 20 is generated in the second clutch member 4b. Then, the second clutch member 4b moves in a direction approaching the pressure member 5 (i.e., a direction in which the flange portion 4bd of the second clutch member 4b approaches the flange portion 5a of the pressure member 5; the direction of arrow DR2 in FIGS. 2 and 3), generating a second pressing force that amplifies the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7.

[0025] On the other hand, as shown in Figure 22, when the rotation of the output shaft 3 exceeds the rotation speed of the input gear 1 and the clutch housing 2 and back torque is generated, a rotational force in the direction of arrow b in Figure 22 is applied to the second clutch member 4b. As a result, the third inclined surface 4ab and the fourth inclined surface 4bb slide against each other, the back torque limiter cam is activated, and the second clutch member 4b moves in a direction away from the pressure member 5 (i.e., in the direction of arrow d in Figure 22), thereby releasing the pressure contact force (here, the second pressure contact force) between the driving-side clutch plate 6 and the driven-side clutch plate 7. This makes it possible to prevent malfunctions in the power transmission device K and the power source (engine E side) due to back torque.

[0026] As shown in FIGS. 11 to 13, the centrifugal clutch means 9 has a weight member 10 that is movable from an inner diameter side position (see FIG. 2) to an outer diameter side position (see FIG. 17) 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 FIGS. 2 and 3) of the clutch housing 2. The centrifugal clutch means 9 is disposed on the opposite side of the pressure member 5, with the driving side clutch plates 6 and the driven side clutch plates 7 sandwiched between them. In this example, the centrifugal clutch means 9 is disposed on the direction of arrow DR1 in FIG. 2 relative to the pressure member 5. When the weight member 10 is in the outer diameter side position, the centrifugal clutch means 9 presses the driving 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 W. The centrifugal clutch means 9 is configured to apply a first pressing force to the driving 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. As the weight member 10 moves from the inner diameter side position to the outer diameter side position, it biases the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 (the direction of arrow DR2 in FIG. 2). The centrifugal clutch means 9 is configured to release the pressure contact force between the drive side clutch plates 6 and the driven side clutch plates 7 when the weight member 10 is in the inner diameter side position, thereby cutting off the transmission of the driving force of the engine E to the drive wheels W. In other words, the centrifugal clutch means 9 is configured to release the first pressure contact force applied to the drive side clutch plates 6 and the driven side clutch plates 7 when the weight member 10 is in the inner diameter side position, thereby cutting off the transmission of the driving force of the engine E to the wheels.

[0027] As shown in FIG. 12, the centrifugal clutch means 9 includes a plurality of weight members 10, a spring 11, a retainer 12, and a pressed member 13. The plurality of weight members 10 are arranged in the circumferential direction. The weight members 10 are housed in an annular retainer 12. The weight members 10 are made of metal. The weight members 10 are held at an inner diameter side position (see FIG. 2) when no centrifugal force is applied. For example, when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed, the weight members 10 are positioned at the inner diameter side position. When centrifugal force is applied (i.e., when the rotation speed of the engine E exceeds the predetermined rotation speed), the weight members 10 move radially outward against the biasing force of the spring 11 and reach the outer diameter side position (see FIG. 17). The predetermined rotation speed is higher than the idling rotation speed.

[0028] As shown in FIG. 12, the centrifugal clutch means 9 has a plurality of pressure cams 18 that move the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 (the direction of arrow DR2 in FIG. 2). The pressure cams 18 are an example of a second cam. The pressure cams 18 generate a first pressure contact force. The pressure cams 18 are provided in portions where the weight member 10 and the pressed member 13 can come into contact with each other. The pressure cams 18 are formed on the weight member 10 and the pressed member 13. The pressure cams 18 include an inclined surface 10a formed on the tip (the radially outer tip) of the weight member 10 and an inclined surface 13a formed on the pressed member 13. The inclined surfaces 10a and 13a are provided to be slidable against each other. The inclination angle θ1 (see FIG. 15) of the inclined surfaces 10a and 13a of the pressure cam 18 relative to the radial direction, which is a direction perpendicular to the axial direction of the output shaft 3, is different from the inclination angle θ2 (see FIG. 18) of the first inclined surface 4aa relative to the radial direction and the inclination angle θ2 (see FIG. 18) of the second inclined surface 4ba relative to the radial direction. The inclination angle θ1 is the angle between a straight line L1 extending in the radial direction and the inclined surfaces 10a and 13a. The inclination angle θ2 is the angle between a straight line L2 extending in the radial direction and the first inclined surface 4aa and the second inclined surface 4ba. The inclined surfaces 10a and 13a are examples of cam surfaces. The inclination angle θ2 of the first inclined surface 4aa relative to the radial direction and the inclination angle θ2 of the second inclined surface 4ba relative to the radial direction are greater than the inclination angle θ1 of the inclined surfaces 10a and 13a relative to the radial direction.

[0029] When the weight member 10 moves from the inner diameter side position toward the outer diameter side position due to centrifugal force, the pressed member 13 moves in the direction of arrow DR2 in FIG. 2 and presses the flange portion 4bd of the second clutch member 4b via the pressed ring 14. This causes the driving side clutch plate 6 and the driven side clutch plate 7 to be pressed together. In other words, a first pressing force is applied to the driving side clutch plate 6 and the driven side clutch plate 7. The driving force of the engine E is transmitted to the output shaft 3 by the driving side clutch plate 6 and the driven side clutch plate 7 being pressed together.

[0030] On the other hand, when the centrifugal force decreases, the biasing force of the spring 11 moves the weight member 10 from the outer diameter side position toward the inner diameter side position, and the biasing force of the coil spring D2 (see FIG. 3) moves the second clutch member 4b in the direction of the arrow DR1 in FIG. 3, thereby releasing the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7. By releasing the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7, the transmission of the driving force of the engine E to the output shaft 3 is blocked.

[0031] The power transmission device K includes a suppression member D (see FIGS. 3 and 6 ) that suppresses the transmission of the driving force of the engine E (e.g., a portion of the driving force of the engine E) to the drive wheels W when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed (e.g., when the weight member 10 is in the inner diameter position) by the driving-side clutch plate 6 and the driven-side clutch plate 7 being pressed against each other. The suppression member D suppresses the generation of the second pressing force by the pressing force amplifying mechanism 20 when the rotation speed of the engine E is equal to or lower than the predetermined rotation speed. The suppression member D suppresses the generation of the second pressing force by suppressing the operation of the amplifying cam 22 when the rotation speed of the engine E is equal to or lower than the predetermined rotation speed. The suppression member D suppresses the generation of the second pressing force in at least a part of the range of rotation speeds of the engine E that are lower than the idling rotation speed. In this embodiment, the suppression member D suppresses the generation of the second pressing force in the entire range of rotation speeds of the engine E that are lower than the idling rotation speed. The suppression member D allows the second pressing force to be generated by the pressing force amplification mechanism 20 when the rotation speed of the engine E is higher than a predetermined rotation speed. The suppression member D allows the operation of the amplification cam 22 when the rotation speed of the engine E is higher than the predetermined rotation speed, thereby allowing the second pressing force to be generated. The suppression member D includes a stepped portion D1 (see FIG. 6) that engages with the protrusion T of the second clutch member 4b, and a coil spring D2 (see FIG. 3). The suppression member D is provided in a portion where the first clutch member 4a and the second clutch member 4b can come into contact with each other.

[0032] As shown in Figures 6 and 7, the step D1 is provided at a portion where the first clutch member 4a and the second clutch member 4b can come into contact with each other. The step D1 is formed at a predetermined portion of the recess A of the first clutch member 4a. When the protrusion T of the second clutch member 4b engages with the step D1, sliding between the first inclined surface 4aa and the second inclined surface 4ba is suppressed. When the engagement between the protrusion T and the step D1 is released, the suppression of sliding between the first inclined surface 4aa and the second inclined surface 4ba is released.

[0033] As shown in FIG. 3, the coil spring D2 is accommodated in an accommodating recess Ta formed in the protrusion T of the second clutch member 4b. One end of the coil spring D2 is assembled in contact with a support ring 15 fixed to the first clutch member 4a, and biases the second clutch member 4b in the direction of arrow DR1 in FIG. 3 via the protrusion T. That is, the coil spring 16 biases the second clutch member 4b, which is part of the clutch member 4, in a direction away from the pressure member 5. The direction in which the coil spring D2 biases the second clutch member 4b (the direction of arrow DR1 in FIG. 3) is opposite to the direction of the first pressure force applied by the weight member 10 to the drive-side clutch plate 6 and the driven-side clutch plate 7 (the direction of arrow DR2 in FIG. 3). The axis of the coil spring D2 is parallel to the axis of the output shaft 3. As shown in Fig. 5A, the coil spring D2 is disposed between the output shaft 3 and the outer peripheral wall 4be of the second clutch member 4b in the radial direction, which is a direction perpendicular to the axial direction of the output shaft 3. The coil spring D2 is disposed between adjacent through holes 4ag in the circumferential direction. When the first pressing force is equal to or less than the biasing force of the coil spring D2, sliding between the first inclined surface 4aa and the second inclined surface 4ba is suppressed. When the first pressing force becomes greater than the biasing force of the coil spring D2, the suppression of sliding between the first inclined surface 4aa and the second inclined surface 4ba is released.

[0034] As shown in FIG. 18 , when the weight member 10 is in the inner diameter position (i.e., when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed), the suppression member D suppresses (e.g., restricts) the operation of the amplifying cam 22. When the weight member 10 is in the inner diameter position, the suppression member D engages (abuts) with a predetermined portion F of the protrusion T to suppress (e.g., restrict) sliding of the first inclined surface 4aa and the second inclined surface 4ba. That is, the suppression member D suppresses the generation of the second pressing force. Note that, when the suppression member D suppresses the generation of the second pressing force, a part of the clutch member (here, the second clutch member 4b) is configured to be movable in a direction toward the pressure member 5 (the direction of arrow DR2 in FIG. 2 ) by the biasing force of the weight member 10. Therefore, as shown in FIG. 19 , as the weight member 10 moves from the inner diameter position to the outer diameter position, the engagement between the suppression member D and the predetermined portion F of the protrusion T is released (that is, the predetermined portion F of the protrusion T moves away from the suppression member D). As shown in FIG. 20 , when the suppression member D is disengaged from the predetermined portion F of the protrusion T, the suppression member D allows the first inclined surface 4aa and the second inclined surface 4ba to slide. The suppression member D can release the suppression of the operation of the amplifier cam 22 and operate the amplifier cam 22 by moving the weight member 10 from the inner diameter side position to the outer diameter side position. That is, the suppression member D releases the suppression of the generation of the second pressing force while the weight member 10 moves from the inner diameter side position to the outer diameter side position. At this time, for example, the suppression member D releases the suppression of the generation of the second pressing force at a specific rotational speed excluding the rotational speed at which the driving-side clutch plate 6 and the driven-side clutch plate 7 are pressed together and the driving force of the engine E begins to be transmitted to the driving wheels W. The suppression member D may release the suppression of the generation of the second pressing force at a rotational speed lower than the specific rotational speed, or may release the suppression of the generation of the second pressing force at a rotational speed higher than the specific rotational speed.

[0035] 18, when the weight member 10 is in the inner diameter side position (i.e., when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed), even if drag torque occurs between the driving-side clutch plate 6 and the driven-side clutch plate 7, the stepped portion D1 is engaged with (abuts against) the predetermined portion F of the protrusion T, so that the amplifying cam 22 can be prevented from unintentionally operating. Furthermore, when the weight member 10 is in the inner diameter side position (i.e., when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed), even if drag torque occurs between the driving-side clutch plate 6 and the driven-side clutch plate 7, the coil spring D2 biases the second clutch member 4b in a direction away from the pressure member 5, so that the amplifying cam 22 can be prevented from unintentionally operating. Furthermore, as shown in Fig. 15, when the rotation speed of the engine E increases, the weight member 10 starts to move from the inner diameter side position toward the outer diameter side position, and when the first pressing force exceeds the set load of the coil spring D2, the second clutch member 4b moves in the direction of arrow DR2 in Fig. 15 (a direction in which the flange portion 4bd of the second clutch member 4b approaches the flange portion 5a of the pressure member 5). At this time, as shown in Fig. 19, the convex portion T moves in the direction of arrow DR2 in Fig. 19, so that the engagement between the step portion D1 and the predetermined portion F of the convex portion T is released (i.e., the predetermined portion F of the convex portion T moves away from the step portion D1), and the amplifying cam 22 can be operated.

[0036] 16, in the process of weight member 10 moving from the inner diameter side position to the outer diameter side position, as shown in Fig. 20, when the first inclined surface 4aa and the second inclined surface 4ba slide against each other and amplifying cam 22 operates, a second pressing force that amplifies the pressing force between driving-side clutch plate 6 and driven-side clutch plate 7 is generated in addition to the first pressing force by centrifugal clutch means 9. Furthermore, when weight member 10 reaches the outer diameter side position as shown in Fig. 17, predetermined portion F of convex portion T comes into contact with the inner peripheral edge of concave portion A, and operation of amplifying cam 22 stops as shown in Fig. 21.

[0037] As described above, the power transmission device K of this embodiment is provided with the suppression member D that suppresses the driving force of the engine E from being transmitted to the drive wheels W by the driving-side clutch plates 6 and the driven-side clutch plates 7 coming into pressure contact with each other when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed. Here, the suppression member D suppresses the generation of the second pressing force. According to the above aspect, when the rotation speed of the engine E is equal to or lower than a predetermined rotation speed, the suppression member D suppresses the generation of the second pressing force by the pressing force amplifying mechanism 20, thereby preventing the pressing force amplifying mechanism 20 from accidentally operating and causing unintended power transmission.

[0038] In the power transmission device K of this embodiment, the suppression member D suppresses the generation of the second pressing force in at least a part of the range of rotational speeds of the engine E that are lower than the idling rotational speed. According to the above aspect, it is possible to suppress the unintended transmission of power due to the inadvertent operation of the pressing force amplifying mechanism 20 in at least a part of the range of rotational speeds of the engine E that are lower than the idling rotational speed.

[0039] In the power transmission device K of this embodiment, when the suppression member D suppresses the generation of the second pressing force, the second clutch member 4b is configured to be movable in a direction approaching the pressure member 5 by the biasing force of the weight member 10. According to the above aspect, even when the generation of the second pressing force is suppressed, the driving force of the engine E can be transmitted to the drive wheels W.

[0040] In the power transmission device K of this embodiment, the suppression member D may suppress the generation of the second pressing force over the entire range of rotational speeds lower than the idling speed of the engine E. According to the above aspect, it is possible to suppress the unintended transmission of power due to the inadvertent operation of the pressing force amplifying mechanism 20 over the entire range of rotational speeds lower than the idling speed of the engine E.

[0041] In the power transmission device K of this embodiment, the suppression member D releases the suppression of the generation of the second pressing force when the weight member 10 moves from the inner diameter side position to the outer diameter side position. According to the above aspect, the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7 can be effectively amplified at an appropriate timing.

[0042] In the power transmission device K of this embodiment, the suppression member D releases the suppression of the generation of the second pressing force at a specific rotation speed excluding the rotation speed at which the drive-side clutch plate 6 and the driven-side clutch plate 7 are pressed together and the driving force of the engine E begins to be transmitted to the drive wheels W. According to the above aspect, the suppression of the generation of the second pressing force can be released smoothly.

[0043] In the power transmission device K of this embodiment, the suppression member D is provided in a portion where the first clutch member 4a and the second clutch member 4b can come into contact with each other. According to the above aspect, the suppression member D can be disposed by effectively utilizing space, so that the power transmission device K can be made compact even while including the suppression member D.

[0044] In the power transmission device K of this embodiment, the suppression member D suppresses the generation of the second pressing force by suppressing the operation of the amplifying cam 22 when the rotation speed of the engine E is equal to or lower than the predetermined rotation speed, and allows the generation of the second pressing force by allowing the operation of the amplifying cam 22 when the rotation speed of the engine E is higher than the predetermined rotation speed. According to the above aspect, it is possible to suppress the unintended operation of the pressing force amplifying mechanism 20 and the power transmission from being performed unintentionally until the rotation speed of the engine E reaches the predetermined rotation speed, and when the rotation speed of the engine E is higher than the predetermined rotation speed, the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7 can be effectively amplified at an appropriate timing by the operation of the amplifying cam 22.

[0045] In the power transmission device K of this embodiment, the predetermined rotation speed is higher than the idling rotation speed. According to the above aspect, it is possible to prevent the contact pressure force amplifying mechanism 20 from accidentally operating and causing unintended power transmission until the rotation speed of the engine E becomes higher than the idling rotation speed.

[0046] In the power transmission device K of this embodiment, the amplifying cam 22 is provided in a portion where the first clutch member 4a and the second clutch member 4b can come into contact with each other. According to the above aspect, the amplifying cam 22 can be disposed by effectively utilizing space, so that the power transmission device K can be made compact even while including the amplifying cam 22.

[0047] In the power transmission device K of this embodiment, the amplifying cam 22 is formed on the recessed portion A and the protruding portion T. According to the above-described embodiment, the operation of the contact pressure force amplifying mechanism 20 can be reliably suppressed and released.

[0048] In the power transmission device K of this embodiment, the amplifying cam 22 includes a first inclined surface 4aa formed in the recessed portion A and a second inclined surface 4ba formed in the protruding portion T and sliding on the first inclined surface 4aa. According to the above aspect, the contact pressure force amplifying mechanism 20 can be smoothly operated between the first inclined surface 4aa and the second inclined surface 4ba.

[0049] In the power transmission device K of this embodiment, the suppression member D is a step portion D1 formed in the recess A and engaging with the protrusion T, and when the protrusion T engages with the step portion D1, sliding between the first inclined surface 4aa and the second inclined surface 4ba is suppressed. According to the above aspect, the operation of the contact pressure force amplification mechanism 20 can be suppressed more reliably.

[0050] In the power transmission device K of this embodiment, the engagement between the protrusion T and the step D1 is released, thereby releasing the inhibition of sliding between the first inclined surface 4aa and the second inclined surface 4ba. According to the above aspect, the inhibition of operation of the contact pressure force amplifying mechanism 20 can be released more reliably.

[0051] In the power transmission device K of this embodiment, the inclination angle θ1 of the inclined surfaces 10a and 13a of the pressing cam 18 relative to the radial direction, which is a direction perpendicular to the axial direction of the output shaft 3, is different from the inclination angle θ2 of the first inclined surface 4aa and the inclination angle θ2 of the second inclined surface 4ba relative to the radial direction. According to the above aspect, the first pressing force and the second pressing force can each be set to an optimum value.

[0052] In the power transmission device K of this embodiment, the inclination angle θ2 of the first inclined surface 4aa with respect to the radial direction and the inclination angle θ2 of the second inclined surface 4ba with respect to the radial direction are larger than the inclination angle θ1 of the inclined surfaces 10a and 13a with respect to the radial direction. According to the above aspect, the second pressing force generated by the pressing force amplifying mechanism 20 can be made larger.

[0053] In the power transmission device K of this embodiment, the suppression member D biases the second clutch member 4b in a direction away from the pressure member 5. According to the above aspect, it is possible to suppress, with a simple configuration, the unintended operation of the contact pressure force amplification mechanism 20 and the like.

[0054] In the power transmission device K of this embodiment, the suppression member D is a coil spring D2. According to the above aspect, it is possible to suppress, with a simpler configuration, unintended power transmission due to inadvertent operation of the contact pressure force amplification mechanism 20.

[0055] In the power transmission device K of this embodiment, the axis of the coil spring D2 is parallel to the axis of the output shaft 3. According to the above aspect, the coil spring D2 can reliably bias the second clutch member 4b in a direction away from the pressure member 5.

[0056] In the power transmission device K of this embodiment, the coil spring D2 is disposed between the output shaft 3 and the outer peripheral wall 4be in the radial direction, which is a direction perpendicular to the axial direction of the output shaft 3. According to the above aspect, the coil spring D2 can be disposed by effectively utilizing space, and therefore the power transmission device K can be made compact even while including the coil spring D2.

[0057] In the power transmission device K of this embodiment, the coil spring D2 is disposed between adjacent through holes 4ag. According to the above aspect, the coil spring D2 can be disposed by effectively utilizing space, and therefore the power transmission device K can be made compact even while including the coil spring D2.

[0058] The power transmission device K of this embodiment includes a step portion D1 and a coil spring D2. According to the above aspect, it is possible to more reliably prevent the contact pressure force amplifying mechanism 20 from accidentally operating and causing unintended power transmission.

[0059] Second Embodiment 23 to 30, the power transmission device K2 includes a clutch housing 2, an output shaft 3, a clutch member 204, a pressure member 205, a plurality of driving-side clutch plates 6 and a plurality of driven-side clutch plates 7 assembled in a stacked state, and a centrifugal clutch means 9 having a weight member 10. Note that the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0060] The power transmission device K2 includes a clutch spring S. The clutch spring S biases the pressure member 205 in a direction approaching the clutch member 204 (the direction of the arrow DR2 in FIG. 24).

[0061] As shown in FIG. 26 , the pressure member 5 is formed with a sixth inclined surface 5b and an eighth inclined surface 5c. The pressure member 5 has a plurality of engaging teeth 5e that hold the driven-side clutch plate 7. The plurality of engaging teeth 5e are arranged in the circumferential direction. The engaging teeth 5e are located radially inward of the flange portion 5a. The engaging teeth 5e are located radially outward of the sixth inclined surface 5b and the eighth inclined surface 5c. The pressure member 5 is arranged so that it can move toward or away from the clutch member 4. The pressure member 5 is configured so that it can press the driving-side clutch plate 6 and the driven-side clutch plate 7.

[0062] As shown in FIG. 27, the first clutch member 204a is formed with a fifth inclined surface 4ae and a seventh inclined surface 4af. When the first clutch member 204a and the pressure member 205 are assembled, the fifth inclined surface 4ae and the sixth inclined surface 5b face each other to form a back torque limiter cam, and the seventh inclined surface 4af and the eighth inclined surface 5c face each other to form a pressure-assist cam. When the engine E's rotation speed reaches a predetermined rotation speed or higher, the seventh inclined surface 4af and the eighth inclined surface 5c slide against each other. As a result, the pressure member 205 moves in the direction of arrow DR1 in FIG. 24, and the drive-side clutch plate 6 and the driven-side clutch plate 7 are pressed against each other. In other words, a third pressure force is generated between the drive-side clutch plate 6 and the driven-side clutch plate 7. Meanwhile, the fifth inclined surface 4ae and the sixth inclined surface 5b slide against each other, causing the pressure member 5 to move in the direction of arrow DR2 in FIG. 24. As a result, the pressure contact force (here, the third pressure contact force) between the driving side clutch plates 6 and the driven side clutch plates 7 is released.

[0063] As shown in Figure 24, the centrifugal clutch means 9 is disposed on the opposite side of the pressure member 205 with the driving side clutch plates 6 and the driven side clutch plates 7 sandwiched therebetween. Here, the centrifugal clutch means 9 is disposed on the direction of arrow DR2 in Figure 24 relative to the pressure member 205. The weight member 10 of the centrifugal clutch means 9 is configured to be movable from an inner diameter side position (see Figure 24) to an outer diameter side position (see Figure 30) by centrifugal force accompanying rotation of the clutch housing 2. As the weight member 10 moves from the inner diameter side position to the outer diameter side position, it biases the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 (the direction of arrow DR1 in Figure 24).

[0064] The pressing force amplifying mechanism 20 applies a second pressing force to the driving side clutch plate 6 and the driven side clutch plate 7 in the direction of the arrow DR1 in FIG.

[0065] The power transmission device K2 includes an assist cam mechanism 30. When the first clutch member 204a rotates relative to the pressure member 205, the assist cam mechanism 30 generates a third pressure force that amplifies the pressure force between the drive-side clutch plate 6 and the driven-side clutch plate 7. The assist cam mechanism 30 applies the third pressure force to the drive-side clutch plate 6 and the driven-side clutch plate 7 in the direction of arrow DR2 in FIG. 24. That is, the direction in which the second pressure force is applied (the direction of arrow DR1 in FIG. 24) and the direction in which the third pressure force is applied (the direction of arrow DR2 in FIG. 24) are opposite to each other. The assist cam mechanism 30 has multiple assist cams 32. The assist cam 32 includes a seventh inclined surface 4af and an eighth inclined surface 5c. In this embodiment, the assist cam mechanism 30 has three assist cams 32. The number of assist cams 32 is not limited to three. In this embodiment, the number of amplifying cams 22 is six, which is greater than the number of assist cams 32. The number of amplifying cams 22 may be the same as the number of assist cams 32.

[0066] The pressing force amplification mechanism 20 operates when the engine E's rotational speed is in the range of R5 to R9, as indicated by arrow ER1 in FIG. 31. The pressing force amplification mechanism 20 starts to generate the second pressing force when the engine E's rotational speed is R5, and completes the generation of the second pressing force when the engine E's rotational speed is R9. The assist cam mechanism 30 operates when the engine E's rotational speed is in the range of R7 to R10, as indicated by arrow ER2 in FIG. 31. The assist cam mechanism 30 starts to generate the third pressing force when the engine E's rotational speed is R7, and completes the generation of the third pressing force when the engine E's rotational speed is R10. The weight member 10 operates when the engine E's rotational speed is in the range of R2 to R8, as indicated by arrow ER3 in FIG. 31. The weight member 10 starts to move from the inner diameter side position toward the outer diameter side position when the engine E's rotational speed is R2, and completes its movement and is located at the outer diameter side position when the engine E's rotational speed is R8. As indicated by the arrow ER4 in FIG. 31 , the suppression member D operates when the engine E's rotational speed is in the range of R1 to R3. That is, the suppression member D suppresses the generation of the second pressing force by the pressing force amplification mechanism 20 when the engine E's rotational speed is in the range of R1 to R3. The suppression member D begins to suppress the generation of the second pressing force when the engine E's rotational speed is R1, and releases the suppression of the generation of the second pressing force when the engine E's rotational speed is R3. Here, the suppression member D releases the suppression of the generation of the second pressing force at a specific rotational speed R3, excluding the rotational speed R4 at which the drive-side clutch plate 6 and the driven-side clutch plate 7 begin to engage. In FIG. 31 , the rotational speed RI of the engine E indicates the idling rotational speed, and the rotational speed RMAX of the engine E indicates the maximum rotational speed. Furthermore, the drive-side clutch plate 6 and the driven-side clutch plate 7 begin to engage when the engine E's rotational speed is R4, and the drive-side clutch plate 6 and the driven-side clutch plate 7 are completely engaged when the engine E's rotational speed is R6. When the rotation speed of the engine E is R4, the driving force of the engine E starts to be transmitted to the drive wheels W. Note that the ranges of the rotation speeds described above are not limited to the ranges indicated by the arrows ER1 to ER4.

[0067] As shown in FIG. 31 , the rotation speed (R7) of the engine E at which the assist cam mechanism 30 begins to operate is different from the rotation speed (R5) of the engine E at which the contact pressure force amplification mechanism 20 begins to operate. The rotation speed (R5) of the engine E at which the contact pressure force amplification mechanism 20 begins to operate is lower than the rotation speed (R7) of the engine E at which the assist cam mechanism 30 begins to operate. The rotation speed (R7) of the engine E at which the contact pressure force amplification mechanism 20 completes its operation is different from the rotation speed (R9) of the engine E at which the assist cam mechanism 30 begins to operate is lower than the rotation speed (R9) of the engine E at which the operation of the contact pressure force amplification mechanism 20 completes its operation. The rotation speed (R7) of the engine E at which the assist cam mechanism 30 begins to operate is lower than the rotation speed (R8) of the engine E at which the weight member 10 completes its movement to the outer diameter side position. The range of engine E rotation speeds (R7 to R10) in which the assist cam mechanism 30 operates is different from the range of engine E rotation speeds (R5 to R9) in which the contact pressure force amplification mechanism 20 operates. The range of engine E rotation speeds (R7 to R10) in which the assist cam mechanism 30 operates is wider than the range of engine E rotation speeds (R5 to R9) in which the contact pressure force amplification mechanism 20 operates.

[0068] Here, when the rotation speed of the engine E increases and the rotational force input to the input gear 1 and the clutch housing 2 can be transmitted to the output shaft 3 via the first clutch member 204a and the second clutch member 4b (i.e., when the weight member 10 is located at the outer diameter side position), a first pressing force is applied to the driving-side clutch plate 6 and the driven-side clutch plate 7, the first inclined surface 4aa and the second inclined surface 4ba slide against each other, and the seventh inclined surface 4af and the eighth inclined surface 5c slide against each other. As a result, the second clutch member 4b and the pressure member 205 move in directions approaching each other, generating a second pressing force and a third pressing force that amplify the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7. That is, when the rotation speed of the engine E reaches a predetermined rotation speed, the pressing force amplifying mechanism 20 and the assist cam mechanism 30 operate to apply the second pressing force and the third pressing force to the driving-side clutch plate 6 and the driven-side clutch plate 7. At this time, a first pressure contact force, a second pressure contact force, and a third pressure contact force are applied to the drive-side clutch plates 6 and the driven-side clutch plates 7. The first pressure contact force and the second pressure contact force are applied in a direction from the centrifugal clutch means 9 toward the pressure member 205 (the direction of arrow DR1 in FIG. 24), and the third pressure contact force is applied in a direction from the pressure member 205 toward the centrifugal clutch means 9 (the direction of arrow DR2 in FIG. 24). When the rotation speed of the engine E is such that the driving force of the engine E is not transmitted to the drive wheels W, the sum of the first pressure contact force and the second pressure contact force is greater than the third pressure contact force. This relationship in which the sum of the first pressure contact force and the second pressure contact force is greater than the third pressure contact force holds regardless of whether the drive-side clutch plates 6 and the driven-side clutch plates 7 are divided into multiple groups. For example, the above relationship holds even when the drive side clutch plates 6 and the driven side clutch plates 7 are divided into multiple groups, and in one of the groups at least a portion of the drive side clutch plates 6 and the driven side clutch plates 7 are in contact with each other, but in other groups the drive side clutch plates 6 and the driven side clutch plates are not in contact, and the driving force of the engine E is not transmitted to the drive wheels W.Furthermore, the rotation speed of the engine E at which the driving force of the engine E is not transmitted to the driving wheels W is the rotation speed at which the driving side clutch plates 6 and the driven side clutch plates 7 are not in contact with each other, or at least some of the driving side clutch plates 6 and at least some of the driven side clutch plates 7 are in contact with each other, and the driving force of the engine E is not transmitted to the driving wheels W. When the weight member 10 is in the outer diameter side position, the sum of the first pressing force and the second pressing force is the same as the sum of the third pressing force and the set load of the clutch spring S.

[0069] On the other hand, when the rotation speed of the output shaft 3 exceeds the rotation speed of the input gear 1 and the clutch housing 2 and back torque is generated, the third inclined surface 4ab and the fourth inclined surface 4bb slide against each other, and the fifth inclined surface 4ae and the sixth inclined surface 5b slide against each other. As a result, the second clutch member 4b and the pressure member 205 move in directions away from each other, and the pressure forces (i.e., the second pressure force and the third pressure force) between the driving-side clutch plate 6 and the driven-side clutch plate 7 are released. At this time, the first pressure force is applied to the driving-side clutch plate 6 and the driven-side clutch plate 7.

[0070] <Third embodiment> Fig. 32 is a plan view of a clutch member 304 according to the third embodiment. As shown in Fig. 32, the clutch member 304 includes a first clutch member 304a, a second clutch member 304b, and a torsion spring D3. The first clutch member 304a is fitted to the second clutch member 304b. The torsion spring D3 is an example of a suppressing member D. In the third embodiment, the stepped portion D1 is an example of another suppressing member.

[0071] 32, the first clutch member 304a includes an accommodation portion 305 that accommodates the torsion spring D3, and a holding portion 306 that is formed in the accommodation portion 305 and holds the torsion spring D3. The holding portion 306 is formed in a cylindrical shape and extends in the axial direction of the output shaft 3.

[0072] As shown in FIG. 32, the torsion spring D3 is accommodated in an accommodating portion 305 formed in the first clutch member 304a. One end of the torsion spring D3 is assembled to be able to abut against a side wall of the accommodating portion 305, and the other end is inserted into an insertion hole 307 formed in the second clutch member 304b and abuts against the outer peripheral wall 4be. The torsion spring D3 biases a part of the clutch member (here, the second clutch member 304b) in a second circumferential direction S2, which is the opposite direction to the first circumferential direction S1. The torsion spring D3 is disposed between the first clutch member 304a and the second clutch member 304b. In the radial direction, which is perpendicular to the axial direction of the output shaft 3, the torsion spring D3 is disposed radially outward of the output shaft 3 and radially inward of an outer peripheral edge 4bf of the outer peripheral wall 4be of the second clutch member 304b. The torsion spring D3 is disposed between adjacent through holes 4ag in the circumferential direction. When the rotational torque in the first circumferential direction S1 generated in the second clutch member 304b by the first pressing force is equal to or less than the biasing force of the torsion spring D3, sliding between the first inclined surface 4aa and the second inclined surface 4ba is suppressed. That is, the torsion spring D3 restricts the generation of the second pressing force by the pressing force amplification mechanism 20. When the rotational torque becomes larger than the biasing force of the torsion spring D3, the suppression of sliding between the first inclined surface 4aa and the second inclined surface 4ba is released. That is, the torsion spring D3 allows the generation of the second pressing force by the pressing force amplification mechanism 20.

[0073] In the power transmission device K of this embodiment, the suppression member D biases the second clutch member 4b in the second circumferential direction S2, which is the opposite direction to the first circumferential direction S1. According to the above aspect, it is possible to suppress, with a simple configuration, unintended power transmission due to inadvertent operation of the contact pressure force amplification mechanism 20.

[0074] In the power transmission device K of this embodiment, the suppression member D is a torsion spring D3. According to the above aspect, it is possible to suppress, with a simpler configuration, unintended power transmission due to inadvertent operation of the contact pressure force amplification mechanism 20.

[0075] In the power transmission device K of this embodiment, the torsion spring D3 is disposed between the first clutch member 4a and the second clutch member 4b. According to the above aspect, the torsion spring D3 can be disposed by effectively utilizing space, and therefore the power transmission device K can be made compact even while including the torsion spring D3.

[0076] In the power transmission device K of this embodiment, the torsion spring D3 is disposed radially outward of the output shaft 3 and radially inward of the outer peripheral edge 4bf of the outer peripheral wall 4be in the radial direction, which is a direction perpendicular to the axial direction of the output shaft 3. According to the above aspect, the torsion spring D3 can be disposed by effectively utilizing space, and therefore the power transmission device K can be made compact even while including the torsion spring D3.

[0077] In the power transmission device K of this embodiment, the torsion spring D3 is disposed between adjacent through holes 4ag. According to the above aspect, the torsion spring D3 can be disposed by effectively utilizing space, and therefore the power transmission device K can be made compact even while including the torsion spring D3.

[0078] The power transmission device K of this embodiment includes the step portion D1 and the torsion spring D3. According to the above aspect, it is possible to more reliably prevent the contact pressure force amplifying mechanism 20 from accidentally operating and causing unintended power transmission.

[0079] 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.

[0080] 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.

[0081] In the above-described embodiments, the first clutch member 4a has the recessed portion A and the second clutch member 4b has the protruding portion T, but this is not limiting. For example, the first clutch member 4a may have the protruding portion T and the second clutch member 4b may have the recessed portion A.

[0082] In each of the above-described embodiments, the clutch member 4 is disposed between the centrifugal clutch means 9 having the weight member 10 and the pressure member 5 in the axial direction of the output shaft 3, and the weight member 10 urges the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 (for example, the direction of arrow DR2 in FIG. 2) as it moves from the inner diameter side position to the outer diameter side position, but this is not limited to this. For example, the pressure member 5 may be disposed between the centrifugal clutch means 9 having the weight member 10 and the clutch member 4 in the axial direction of the output shaft 3, and the weight member 10 urges the pressure member 5 in a direction approaching the clutch member 4 as it moves from the inner diameter side position to the outer diameter side position.

[0083] In the first embodiment described above, the suppression member D includes the step portion D1 and the coil spring D2, but if it includes only one of them, the generation of the second pressure contact force by the pressure contact force amplification mechanism 20 can be suppressed.

[0084] In the third embodiment described above, the suppression member D includes the step portion D1 and the torsion spring D3, but if it includes only one of them, the generation of the second pressure contact force by the pressure contact force amplification mechanism 20 can be suppressed.

[0085] The power transmission device of the present invention can be applied to various multi-plate clutch type power transmission devices such as motorcycles, automobiles, three- or four-wheeled buggies, and general-purpose machines. [Explanation of symbols]

[0086] 1 Input gear (input member) 2 Clutch housing 3 Output shaft (output member) 4 Clutch parts 4a First clutch member 4aa First slope 4ab 3rd slope 4ae 5th slope 4af 7th slope 4ag through hole 4b Second clutch member 4ba 2nd slope 4bb 4th slope 4bc spline fitting 4bd flange 4be outer wall 5 Pressure member 5a Flange 5b 6th slope 5c 8th slope 5e Interdigitating teeth 6 Drive side clutch plate 7 Driven side clutch plate 9. Centrifugal clutch means 10 Weight member 10a Slope 13 Pressurized member 13a Slope 18 Pressure cam (second cam) 20. Pressure contact force amplification mechanism 22 Amplifying Cam (1st Cam) 30 Assist cam mechanism 32 Assist Cam A recess D. Restraining member D1 Step (restraining member) D2 coil spring (restraining member) D3 Torsion spring (restraint member) E-Engine K power transmission device S clutch spring T convex part Ta Recess W drive wheels

Claims

1. 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, is connected to an output member that can rotate a wheel, and holds a plurality of driven-side clutch plates that are arranged alternately with the driving-side clutch plates; a pressure member capable of pressing the driving side clutch plate and the driven side clutch plate together with the clutch member, The clutch member is an insertion hole to which the output member is connected; an outer circumferential wall located radially outward of the insertion hole and extending circumferentially and in the axial direction of the output member; a boss portion extending in the axial direction and having an insertion hole through which a bolt is inserted, an outer end of the boss portion in the radial direction is connected to the outer peripheral wall; a radially inner end portion of the boss portion located radially inward of the outer peripheral wall;

2. The clutch member is a first clutch member connected to the output member; a second clutch member that is engaged with the first clutch member and that holds the driven-side clutch plate, the first clutch member includes the insertion hole, the outer peripheral wall, and the boss portion, 2. The power transmission device according to claim 1, wherein an outer peripheral surface of the outer peripheral wall faces an inner peripheral surface of the second clutch member.

3. The power transmission device according to claim 2 , wherein a tip of the boss portion protrudes from the outer peripheral wall in the axial direction.

4. 3. The power transmission device according to claim 2, wherein the driving-side clutch plate and the driven-side clutch plate are located radially outward of a portion of the boss portion that is connected to the outer peripheral wall.

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