Power transmission device

Abstract

To provide a power transmission device that makes it possible to press drive-side clutch plates and driven-side clutch plates against each other to transmit a rotational force on the wheel side to the engine side to apply an engine brake, and that makes it possible to stably perform power transmission when a weight member moves to a radially outer position and a pressure member moves to an active position.SOLUTION: A clutch member includes a first clutch member 4a, a second clutch member 4b, a back-torque transmitting cam, and a torque transmission unit that may transmit a rotational force transmitted to the second clutch member 4b to the first clutch member 4a not via the back-torque transmitting cam, where the torque transmission unit is located radially inside drive-side clutch plates 6 and driven-side clutch plates 7.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power transmission device capable of arbitrarily transmitting or blocking the rotational force of an input member to an output member.

Background Art

[0002] Generally, a power transmission device provided in a motorcycle is for arbitrarily transmitting or blocking the driving force of an engine to a transmission and a driving wheel. It has an input member connected to the engine side, an output member connected to the transmission and driving wheel sides, a clutch member connected to the output member, and a pressure member that can approach or separate from the clutch member. By bringing the pressure member close to the clutch member, the driving-side clutch plate and the driven-side clutch plate are pressed together to transmit power, and by separating the pressure member from the clutch member, the pressing force between the driving-side clutch plate and the driven-side clutch plate is released to block the transmission of the power.

[0003] As a conventional power transmission device, for example, as disclosed in Patent Document 1, there has been proposed a device provided with a weight member that can press the driving-side clutch plate and the driven-side clutch plate together by moving from the inner diameter side position to the outer diameter side position of the groove portion by centrifugal force associated with the rotation of the clutch housing. According to such a conventional power transmission device, when the clutch housing rotates as the engine drives, centrifugal force can be applied to the weight member, and the driving-side clutch plate and the driven-side clutch plate can be pressed together to transmit the driving force of the engine to the wheels.

[0004] Furthermore, in the conventional power transmission device, as the interlocking member moves and the pressure member moves from the non-operating position toward the operating position, it is compressed, and an urging force can be applied while allowing the movement of the interlocking member and the pressure member until it reaches the fastening state before the driving-side clutch plate and the driven-side clutch plate are pressed against each other. There is a release spring, and after the driving-side clutch plate and the driven-side clutch plate reach the fastened state, it is compressed during the process of the interlocking member moving, and a clutch spring that can apply a pressing force between the driving-side clutch plate and the driven-side clutch plate while allowing the movement of the interlocking member.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0006] The invention according to claim 1 is a clutch member accommodated in a clutch housing that rotates together with an input member rotated by the driving force of an engine of a vehicle, and to which a plurality of driving-side clutch plates are attached. A plurality of driven-side clutch plates formed alternately with the driving-side clutch plates of the clutch housing are attached, and the clutch member is connected to an output member capable of rotating the wheels of the vehicle. A pressure member movable between an operating position in which the driving force of the engine can be transmitted to the wheels by pressing the driving-side clutch plate and the driven-side clutch plate against each other, and a non-operating position in which the pressing force between the driving-side clutch plate and the driven-side clutch plate is released to block the transmission of the driving force of the engine to the wheels; a weight member movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying the rotation of the clutch housing; and a holding member for holding the weight member. In the power transmission device having the holding member, the holding member includes a ring-shaped main body portion, an extending portion extending in the axial direction of the output member from an outer end portion in the radial direction of the main body portion, a plurality of first wall portions formed on the main body portion, extending in the radial direction, and arranged in the circumferential direction, a plurality of first groove portions formed on the main body portion, extending in the radial direction, and formed between adjacent first wall portions, a plurality of second wall portions formed on the extending portion, extending in the axial direction, and continuous with the first wall portions, and a plurality of second groove portions formed on the extending portion, extending in the axial direction, formed between adjacent second wall portions, and continuous with the first groove portions. The surface on the open end side of the extending portion is a flat surface continuous over the entire circumferential direction.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The power transmission device according to the present embodiment is for a vehicle such as a motorcycle, etc., and is disposed on the vehicle to arbitrarily transmit or cut off the driving force of the engine to the transmission or the drive wheel side. As shown in FIGS. 1 to 12, a clutch housing 2 formed with an input gear 1 (input member) that rotates by the driving force of the vehicle engine, clutch members (first clutch member 4a and second clutch member 4b), a pressure member 5 attached to the right side in FIG. 2 of the clutch members (first clutch member 4a and second clutch member 4b), a plurality of drive side clutch plates 6 and a plurality of driven side clutch plates 7, a weight member 8 composed of steel ball members that can move (roll) in the radial direction within the clutch housing 2, an interlocking member 9, and an operating member 10 that can be operated manually or by an actuator (not shown). In the figure, reference symbol S indicates a spring damper, reference symbol B1 indicates a roller bearing, and reference symbols B2 and B3 indicate thrust bearings, respectively.

[0009] The input gear 1 is rotatable about the output shaft 3 when the driving force (rotational force) transmitted from the engine is input, and is connected to the clutch housing 2 by a rivet R or the like. The clutch housing 2 is composed of a cylindrical member with an open right end side in FIG. 2, and includes a housing portion 2a connected to the input gear 1 and a cover portion 2b attached to close the opening of the housing portion 2a, and is configured to be rotatable with the rotation of the input gear 1 by the driving force of the engine.

[0010] Also, as shown in FIG. 4, the housing portion 2a of the clutch housing 2 has a plurality of notches 2aa formed in the circumferential direction, and a plurality of driving-side clutch plates 6 are attached by fitting into these notches 2aa. Each of the driving-side clutch plates 6 is composed of a plate material formed in a substantially annular shape, rotates with the rotation of the clutch housing 2, and is configured to be slidable in the axial direction (the left-right direction in FIG. 2).

[0011] Furthermore, as shown in FIG. 5, the cover portion 2b of the clutch housing 2 has a plurality of groove portions 2ba formed on its bottom surface and extending in the radial direction of the cover portion 2b. Weight members 8 are respectively disposed in the groove portions 2ba. In a state where the clutch housing 2 is stopped (engine stopped or idling state) and a state of rotating at a low speed, the weight members 8 are set to be at the inner diameter side position (the position shown in FIG. 2), and in a state where the clutch housing 2 rotates at a high speed, the weight members 8 are set to be at the outer diameter side position.

[0012] The clutch members (the first clutch member 4a and the second clutch member 4b) are provided with a plurality of driven-side clutch plates 7 formed alternately with the driving-side clutch plates 6 of the clutch housing 2, and are connected to an output shaft 3 (output member) capable of rotating the vehicle wheels. The clutch members are configured by assembling two members, namely the first clutch member 4a and the second clutch member 4b.

[0013] As shown in Fig. 6, the first clutch member 4a is composed of a disc-shaped member having a flange surface 4ac formed over its peripheral edge. The output shaft 3 is inserted through an insertion hole 4ad (see Figs. 2 and 6) formed at its center, and gears formed thereon are engaged with each other to be connected in the rotational direction. As shown in Figs. 6, 9, and 10, a gradient surface 4aa constituting a cam for pressing assist and a gradient surface 4ab constituting a cam for back torque limiter are formed on such a first clutch member 4a.

[0014] As shown in Fig. 7, the second clutch member 4b is composed of an annular member, and a driven-side clutch plate 7 is configured to be attached by spline fitting to a spline fitting portion 4ba (see Figs. 2 and 7) formed on its outer peripheral surface. Then, as shown in Figs. 9 to 11, a pressure member 5 is assembled to the clutch members (the first clutch member 4a and the second clutch member 4b), and a plurality of drive-side clutch plates 6 and driven-side clutch plates 7 are alternately stacked between the flange surface 5c (see Figs. 2 and 8) of the pressure member 5 and the flange surface 4ac (see Figs. 2 and 6) of the first clutch member 4a.

[0015] As shown in Fig. 8, the pressure member 5 is composed of a disc-shaped member having a flange surface 5c formed over its peripheral edge, and is movable between an operating position where the drive-side clutch plate 6 and the driven-side clutch plate 7 are pressed against each other to enable the driving force of the engine to be transmitted to the wheels, and a non-operating position (see Fig. 2) where the pressing force between the drive-side clutch plate 6 and the driven-side clutch plate 7 is released to block the transmission of the driving force of the engine to the wheels.

[0016] More specifically, as shown in FIGS. 7, 9, and 10, the spline fitting portion 4ba formed on the second clutch member 4b is configured by an uneven shape integrally formed over substantially the entire circumference of the outer peripheral side surface of the second clutch member 4b. When the driven-side clutch plate 7 is fitted into the concave groove constituting the spline fitting portion 4ba, the axial movement of the driven-side clutch plate 7 with respect to the second clutch member 4b is allowed while the rotational movement is restricted, and it is configured to be able to rotate together with the second clutch member 4b.

[0017] Such a driven-side clutch plate 7 is alternately laminated with the drive-side clutch plate 6, and adjacent clutch plates 6, 7 can be brought into pressure contact or the pressure contact force can be released. That is, both clutch plates 6, 7 are allowed to slide in the axial direction of the second clutch member 4b. When the pressure member 5 moves to the left side in FIG. 2 and its flange surface 5c and the flange surface 4ac of the first clutch member 4a approach each other, both clutch plates 6, 7 are brought into pressure contact, 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. When the pressure member 5 moves to the right side in FIG. 2 and its flange surface 5c and the flange surface 4ac of the first clutch member 4a are separated from each other, the pressure contact force between both clutch plates 6, 7 is released, and the first clutch member 4a and the second clutch member 4b no longer follow the rotation of the clutch housing 2, and the transmission of the rotational force to the output shaft 3 is stopped.

[0018] Thus, in a state where the drive-side clutch plate 6 and the driven-side clutch plate 7 are in pressure contact, the rotational force (engine driving force) input to the clutch housing 2 is transmitted to the wheel side via the output shaft 3 (output member), and in a state where the pressure contact between the drive-side clutch plate 6 and the driven-side clutch plate 7 is released, the rotational force (engine driving force) input to the clutch housing 2 can be blocked from being transmitted to the output shaft 3 (output member).

[0019] Furthermore, in the present embodiment, as shown in FIGS. 6, 8, 9, and 10, gradient surfaces 4aa and 4ab are formed on the first clutch member 4a, and gradient surfaces 5a and 5b that face these gradient surfaces 4aa and 4ab are formed on the pressure member 5. That is, the gradient surface 4aa and the gradient surface 5a are in contact with each other to form a cam for pressure contact assist, and the gradient surface 4ab and the gradient surface 5b are in contact with each other to form a cam for back torque limiter.

[0020] Then, when the engine speed 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 (the weight member 8 is in the outer diameter side position), as shown in FIG. 13, a rotational force in the a direction is applied to the pressure member 5. Therefore, due to the action of the cam for pressure contact assist, a force in the c direction in the figure is generated on the pressure member 5. As a result, the pressure member 5 moves in a direction closer to the flange surface 4ac of the first clutch member 4a (the left side in FIG. 2) with its flange surface 5c, so as to increase the pressure contact force between the driving side clutch plate 6 and the driven side clutch plate 7.

[0021] On the other hand, when the vehicle is running and the rotation of the output shaft 3 exceeds the rotation speed of the input gear 1 and the clutch housing 2, and a back torque in the b direction in FIG. 14 occurs, due to the action of the cam for back torque limiter, the pressure member 5 is moved in the d direction in the figure to release the pressure contact force between the driving side clutch plate 6 and the driven side clutch plate 7. Thereby, problems with respect to the power transmission device and the power source (engine side) due to the back torque can be avoided.

[0022] The weight member 8 is disposed in a groove portion 2ba extending in the radial direction of the clutch housing 2 (cover portion 2b in this embodiment), and moves from the inner diameter side position (see FIG. 2) to the outer diameter side position of the groove portion 2ba by the centrifugal force accompanying the rotation of the clutch housing 2, so that the driving side clutch plate 6 and the driven side clutch plate 7 can be pressed against each other. That is, the rolling surface (bottom surface) of the weight member 8 in the groove portion 2ba is inclined upward from the inner diameter side position to the outer diameter side position. In a state where the clutch housing 2 is stopped, the weight member 8 is held at the inner diameter side position by the biasing force of the release spring m. When the clutch housing 2 rotates, a centrifugal force is applied to the weight member 8 and it is moved along the upward gradient, and when the clutch housing 2 reaches a predetermined rotational speed, it is moved to the outer diameter side position.

[0023] The interlocking member 9 is composed of an annular member disposed in the clutch housing 2 (cover member 2b), is fitted and connected to a groove portion formed on the inner peripheral surface of the cover member 2b, and is rotatable together with the clutch housing 2 and is movable in the left-right direction in FIG. 2. As the weight member 8 moves from the inner diameter side position to the outer diameter side position, the interlocking member 9 is configured to move to the left side in FIG. 2 against the biasing forces of the clutch spring 11 and the release spring m, and to press the pressure member 5 to move it from the non-operating position to the operating position.

[0024] The operating member 10 is composed of a member that can be operated manually or by an actuator (see FIG. 2), and can move the pressure member 5 in a direction (right side in FIG. 2) that can release the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7. During a shift operation, the operating member 10 moves to the right side in FIG. 2 by an operation on a clutch pedal, a clutch lever, etc. provided in the vehicle, or by the operation of an actuator, and abuts against the pressure member 5 via a bearing holding member C, and moves the pressure member 5 from the operating position to the non-operating position, thereby releasing the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7 to disengage the clutch (cut off the power transmission).

[0025] As shown in Fig. 2, the bearing holding member C is connected to the operating member 10 and holds the bearing B1 interposed between the operating member 10 and the pressure member 5. As shown in Fig. 12, it is composed of a cylindrical member with one end open, and has an open end Ca and a top Cb on the opposite side of the open end Ca. The bearing B1 according to the present embodiment is attached to the top Cb side inside the bearing holding member C, and a cylindrical portion extends from the enlarged diameter portion to the open end Ca. Although a ball bearing is used as the bearing B1 according to the present embodiment, other bearings such as needle bearings may be used.

[0026] Furthermore, as shown in Figs. 2 and 20, the bearing holding member C according to the present embodiment has its open end Ca fitted and attached to a recess 4d formed in the clutch member (first clutch member 4a), and is assembled by inlaying (press-fitting) with the inner peripheral wall surface 4da of the recess 4d. The recess 4d is formed as a circular depression having substantially the same dimensions (strictly speaking, slightly larger dimensions than the open end Ca) following the outer shape of the open end Ca. By fitting the bearing holding member C into the recess 4d, positioning and centering with respect to the power transmission device are achieved.

[0027] Thus, during a shift operation, for example, when the operating member 10 moves to the right side in Fig. 2 due to an operation on a clutch pedal, a clutch lever, etc. provided in the vehicle, or the operation of an actuator, the bearing holding member C moves in conjunction and contacts the pressure member 5, and by moving the pressure member 5 from the operating position to the non-operating position, the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7 is released to disengage the clutch (cut off the power transmission).

[0028] The release spring m can hold the pressure member 5 in the non-operating position, and is compressed as the interlocking member 9 moves and the pressure member 5 moves from the non-operating position toward the operating position, and before the driving-side clutch plate 6 and the driven-side clutch plate 7 are brought into pressure contact (the state where the separation distance between the driving-side clutch plate 6 and the driven-side clutch plate 7 becomes zero and immediately before power transmission by pressure contact is performed), it can apply a biasing force while allowing the movement of the interlocking member 9 and the pressure member 5.

[0029] Furthermore, as shown in FIG. 21, the release spring m according to the present embodiment is formed of an annular disc spring that can generate a biasing force by the displacement of the central portion ma and the peripheral portion mb. As shown in FIGS. 2 and 20, the central portion ma is attached to the top Cb of the bearing holding member C, and the peripheral portion mb is attached to the pressure member 5. The pressure member 5 has a protruding portion 5d protruding in an annular shape, and the peripheral portion mb of the release spring m is locked and attached to a ring-shaped member g (for example, a circlip or the like) attached to the protruding portion 5d. Thereby, the release spring m according to the present embodiment is attached across both the bearing holding member C and the pressure member 5, applies a biasing force (biasing force in the direction indicated by reference numeral a2 in FIG. 20) to the pressure member 5, and can apply a biasing force (biasing force in the direction indicated by reference numeral a1 in the same figure) to the bearing holding member C and transmit the biasing force to the operating member 10.

[0030] The clutch spring 11 is formed of a coil spring interposed between the interlocking member 9 and the pressure member 5, and can move the pressure member 5 in a direction to press the driving-side clutch plate 6 and the driven-side clutch plate 7 into pressure contact as the interlocking member 9 moves, and can absorb the pressing force of the pressure member 5 against the interlocking member 9 when the operating member 10 operates.

[0031] Further, the clutch spring 11 according to the present embodiment is configured to be compressed in the process of the interlocking member 9 moving before the driving-side clutch plate 6 and the driven-side clutch plate 7 reach the fastening state as described above, and to apply a pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7 while allowing the movement of the interlocking member 9.

[0032] That is, as the weight member 8 moves from the inner diameter side position to the outer diameter side position with the rotation of the clutch housing 2, when the interlocking member 9 is pressed by the weight member 8, the pressing force is transmitted to the pressure member 5 via the clutch spring 11, and the pressure member 5 is moved to the left side in FIG. 2 to bring the driving-side clutch plate 6 and the driven-side clutch plate 7 into pressure contact with each other. When the operating member 10 is operated in this state, although the pressure member 5 moves to the right side in the figure by the pressing force of the operating member 10, the pressing force on the interlocking member 9 is absorbed by the clutch spring 11, and the position of the interlocking member 9 (the position of the weight member 8) is maintained.

[0033] Here, in the power transmission device according to the present embodiment, when a rotational force is input to the first clutch member 4a via the output shaft 3 (output member), a back torque transmission cam (cam surfaces K1, T1) capable of moving the second clutch member 4b to bring the driving-side clutch plate 6 and the driven-side clutch plate 7 into pressure contact with each other is provided. As shown in FIGS. 6, 7, 9, and 10, such a back torque transmission cam is constituted by cam surfaces (K1, T1) integrally formed on the mating surfaces (mating surfaces when combined) of the first clutch member 4a and the second clutch member 4b, respectively.

[0034] As shown in FIGS. 6 and 9, the cam surface K1 is composed of a plurality of gradient surfaces formed over the entire circumference on the inner diameter side (the mating surface with the second clutch member 4b) of the flange surface 4ac formed on the first clutch member 4a, and is formed on one end surface of a plurality of annularly formed groove portions K along the peripheral edge of the first clutch member 4a. That is, a plurality of groove portions K are formed in the first clutch member 4a over its circumferential direction, and one end surface of each groove portion K serves as a gradient surface to constitute the cam surface K1 of the back torque transmission cam. Note that the other end surface of each groove portion K is a wall surface K2 extending in the axial direction of the first clutch member 4a.

[0035] As shown in FIGS. 7 and 10, the cam surface T1 is composed of a plurality of gradient surfaces formed over the entire circumference on the bottom surface (the mating surface with the first clutch member 4a) of the second clutch member 4b, and is formed on one end surface of a plurality of annularly formed protrusion portions T along the bottom surface of the second clutch member 4b. That is, a plurality of protrusion portions T are formed in the second clutch member 4b over its circumferential direction, and one end surface of each protrusion portion T serves as a gradient surface to constitute the cam surface T1 of the back torque transmission cam. Note that the other end surface of each protrusion portion T is a wall surface T2 extending in the axial direction of the second clutch member 4b.

[0036] When the protrusion portion T is fitted into the groove portion K to combine the first clutch member 4a and the second clutch member 4b, as shown in FIG. 17, the cam surface K1 and the cam surface T1 face each other to constitute the back torque transmission cam, and the wall surface K2 and the wall surface T2 face each other with a predetermined dimension therebetween. Thus, when a rotational force is input to the first clutch member 4a via the output shaft 3, the first clutch member 4a rotates relative to the second clutch member 4b. Therefore, as shown in FIG. 18, due to the action of the cam of the cam surface K1 and the cam surface T1, the second clutch member 4b is moved to the right side in FIGS. 2 and 18 with respect to the first clutch member 4a.

[0037] On the other hand, as shown in FIG. 7, a pressing portion 4bb is formed on the second clutch member 4b on the extension of the spline fitting portion 4ba. When the second clutch member 4b moves to the right side in FIG. 2, the leftmost driven clutch plate 7 among the driving clutch plate 6 and the driven clutch plate 7 attached in a laminated state in the figure is pressed in the same direction. As a result, even when the pressure member 5 is in the non-operating position, the driving clutch plate 6 and the driven clutch plate 7 can be brought into pressure contact with each other, and when a rotational force is input from the output shaft 3 (output member), the rotational force can be transmitted to the engine side to generate an engine brake.

[0038] In particular, the back torque transmission cam according to the present embodiment is configured to move the second clutch member 4b in a direction approaching the interlocking member 9 (right side in FIG. 2) so as to maintain the contact between the interlocking member 9 and the weight member 8. That is, when the back torque transmission cam operates and moves the second clutch member 4b to the right side in FIG. 2, the driving clutch plate 6 and the driven clutch plate 7 are brought into pressure contact with each other, and the pressure member 5 is pressed in the same direction. Therefore, the pressing force is transmitted to the interlocking member 9 via the clutch spring 11, and the contact between the interlocking member 9 and the weight member 8 is maintained.

[0039] However, when the interlocking member 9 and the weight member 8 are separated from each other during the operation of the back torque transmission cam, thereafter, even if the weight member 8 moves between the inner diameter side position and the outer diameter side position as the clutch housing 2 rotates, the interlocking member 9 may not be able to follow the movement. On the other hand, according to the present embodiment, even during the operation of the back torque transmission cam, the contact between the interlocking member 9 and the weight member 8 can be maintained, so that the interlocking member 9 can stably follow the movement of the weight member 8.

[0040] Furthermore, a plurality of cam surfaces K1 and T1 that constitute the back torque transmission cam according to the present embodiment are formed along the annular shape of the driven clutch plate 7 attached to the second clutch member 4b. That is, when the back torque transmission cam operates, the cam surfaces K1 and T1 are formed along the projected shape (annular shape) of the driven clutch plate 7 pressed by the pressing portion 4bb. Thereby, due to the action of the back torque transmission cam, the pressing portion 4bb can apply a substantially uniform pressing force to the driven clutch plate 7, and the driving clutch plate 6 and the driven clutch plate 7 can be pressed against each other more efficiently.

[0041] Moreover, the back torque transmission cam (the cam constituted by the cam surface K1 and the cam surface T1) according to the present embodiment is configured to be able to operate before the back torque limiter cam (the cam constituted by the gradient surface 4ab and the gradient surface 5b) operates. That is, the clearance (gap dimension) between the cam surface K1 and the cam surface T1 is set smaller than the clearance (gap dimension) between the gradient surface 4ab and the gradient surface 5b, so that the back torque transmission cam can operate before the back torque limiter cam operates.

[0042] Furthermore, in the power transmission device according to the present embodiment, there are provided a torque transmission portion that is formed on the first clutch member 4a and the second clutch member 4b respectively and can transmit the rotational force transmitted to the second clutch member 4b to the first clutch member 4a without passing through the back torque transmission cam (the cam surface K1 and the cam surface T1), and a movement amount limiting portion that is formed on the first clutch member 4a and the second clutch member 4b respectively and limits the movement amount of the second clutch member 4b by the back torque transmission cam (the cam surface K1 and the cam surface T1).

[0043] That is, as shown in FIGS. 6 and 9, a plurality (three in this embodiment) of convex portions F are integrally formed at equal intervals in the circumferential direction on the first clutch member 4a, and as shown in FIGS. 7 and 9, a protruding portion G extending inward is integrally formed on the second clutch member 4b. When the first clutch member 4a and the second clutch member 4b are assembled, as shown in FIGS. 15 and 16, one convex portion F is sandwiched between two protruding portions G, and one side surface F1 of the convex portion F and the contact surface (first contact surface G1) of one of the protruding portions G face each other, and the other side surface F2 of the convex portion F and the contact surface (second contact surface G2) of the other protruding portion G are configured to face each other.

[0044] Thus, one side surface F1 of the convex portion F formed on the first clutch member 4a and the first contact surface G1 of one of the protruding portions G formed on the second clutch member 4b constitute the torque transmission portion according to this embodiment. That is, when the pressure member 5 moves to the operating position and the drive-side clutch plate 6 and the driven-side clutch plate 7 are pressed into contact with each other and the clutch is turned on (transmits the driving force), while maintaining the separated state (see FIG. 17) between the wall surface K2 of the groove portion K and the wall surface T2 of the protruding portion T in the back torque transmission cam, as shown in FIG. 15, one side surface F1 of the convex portion and the first contact surface G1 of the protruding portion G come into contact with each other, and the rotational force of the second clutch member 4b can be received and transmitted to the first clutch member 4a.

[0045] Further, the other side surface F2 of the convex portion F formed on the first clutch member 4a and the second contact surface G2 of the other protruding portion G formed on the second clutch member 4b constitute the movement amount restricting portion according to the present embodiment. That is, when a rotational force is input to the first clutch member 4a via the output shaft 3, the first clutch member 4a and the second clutch member 4b rotate relative to each other. Therefore, the second clutch member 4b moves due to the cam action between the cam surface K1 of the groove portion K and the cam surface T1 of the protruding portion T in the back torque transmission cam (see FIG. 18). When the movement amount reaches the set value, as shown in FIG. 16, the other side surface F2 of the convex portion and the second contact surface G2 of the protruding portion G come into contact with each other, and the relative rotation of the second clutch member 4b with respect to the first clutch member 4a is restricted. Thus, the movement amount of the second clutch member 4b when the back torque transmission cam operates can be restricted.

[0046] In the present embodiment, the convex portion F is formed on the first clutch member 4a and the protruding portion G is formed on the second clutch member 4b. Alternatively, the protruding portion G may be formed on the first clutch member 4b and the convex portion F may be formed on the second clutch member 4b. In this case, one side surface F1 of the convex portion F formed on the second clutch member 4b and the first contact surface G1 of the one protruding portion G formed on the first clutch member 4a constitute the torque transmission portion according to the present embodiment, and the other side surface F2 of the convex portion F formed on the second clutch member 4b and the second contact surface G2 of the other protruding portion G formed on the first clutch member 4b constitute the movement amount restricting portion according to the present embodiment.

[0047] Next, the operation of the back torque transmission cam in the present embodiment will be described. When the engine is stopped or idling, since the driving force of the engine is not transmitted to the input gear 1 or the rotational speed of the input gear 1 is low, as shown in FIG. 2, the weight member 8 is positioned on the inner diameter side and the pressure member 5 is in the non-operating position. At this time, when a rotational force is input to the first clutch member 4a via the output shaft 3 (output member), due to the action of the back torque transmission cam, the second clutch member 4b moves to the right side in the figure, and the driving side clutch plate 6 and the driven side clutch plate 7 are pressed into contact to transmit the rotational force to the engine side.

[0048] After the vehicle stops or idles and then starts moving, since the rotational speed of the input gear 1 shifts from low rotation to high rotation (mid-rotation range), the weight member 8 is positioned between the inner diameter side position and the outer diameter side position, and the pressure member 5 is in the operating position. At this time, when, for example, the accelerator is released while going downhill and a rotational force is input to the first clutch member 4a via the output shaft 3 (output member), due to the action of the back torque transmission cam, the second clutch member 4b moves to the right side in the figure, and the driving side clutch plate 6 and the driven side clutch plate 7 are pressed into contact to transmit the rotational force to the engine side.

[0049] After the vehicle starts moving, accelerates, and runs in the high-speed range, since the rotational speed of the input gear 1 is high, the weight member 8 is positioned on the outer diameter side and the pressure member 5 is in the operating position. At this time, when downshifting or the like causes a rotational force to be input to the first clutch member 4a via the output shaft 3 (output member), due to the action of the back torque transmission cam, the second clutch member 4b moves to the right side in the figure, and the driving side clutch plate 6 and the driven side clutch plate 7 are pressed into contact to transmit the rotational force to the engine side.

[0050] Here, in the power transmission device according to the present embodiment, the set load of the clutch spring 11 is set to be smaller than the maximum load of the release spring m. As a result, when the engine speed increases and the weight member 8 moves from the inner diameter side position to the outer diameter side position, in the process where the interlocking member 9 is pressed and moved by the weight member 8, when the release spring m is compressed and exceeds the set load of the clutch spring 11, the release spring m and the clutch spring 11 start to be compressed, so that it is possible to avoid the occurrence of a dead zone.

[0051] Next, the operation of the power transmission device according to the present embodiment will be described in comparison with a conventional one in which the set load of the clutch spring is set to be larger than the maximum load of the release spring. First, the operation of the conventional power transmission device will be described with reference to the graph in FIG. 34 (a graph with the horizontal axis representing the movement amount (mm) of the interlocking member 9 and the vertical axis representing the pressing load (N) generated on the interlocking member 9). In the graph of FIG. 34, P1 is the pressing load of the interlocking member 9 when the deflection amount (compression amount) of the release spring m reaches the maximum (when the maximum load of the release spring m is reached), and P2 is the pressing load of the interlocking member 9 when the clutch spring 11 starts to deflect (when the set load of the clutch spring 11 is reached).

[0052] In the process where the engine speed increases and the weight member 8 moves from the inner diameter side position to the outer diameter side position, thereby moving the interlocking member 9, until the movement amount of the interlocking member 9 reaches α1, the release spring m deflects while the clutch spring 11 does not deflect (that is, the interlocking member 9 and the pressure member 5 move integrally). When the movement amount of the interlocking member 9 reaches α1, although the pressing load (N) increases from P1 to P2, the interlocking member 9 stops moving, resulting in a dead zone.

[0053] When the pressing load (N) reaches P2 (the set load of the clutch spring 11) from such a state, the clutch spring 11 begins to flex, and as the interlocking member 9 moves, the pressing load (N) will increase. Therefore, until the pressing load (N) reaches from P1 to P2, the interlocking member 12 and the pressure member 5 stop, and after reaching P2, the compression of the clutch spring 11 starts, and the clutch plates (the driving-side clutch plate 6 and the driven-side clutch plate 7) are pressed against each other and power is transmitted, so there is a sudden feeling during power transmission.

[0054] On the other hand, in the present embodiment, since the set load P2 of the clutch spring 11 is set to be smaller than the maximum load P1 of the release spring m, as shown in FIG. 22, in the process of the interlocking member 9 moving, the release spring m is compressed and flexed, and when the movement amount of the interlocking member 9 reaches α2, the set load P2 of the clutch spring 11 is reached and the clutch spring 11 starts to be compressed (flex). After that, when the movement amount of the interlocking member 9 reaches α1, the release spring m reaches the maximum load P1 and there is no further compression (flex), while the clutch spring 11 is compressed and flexed, and the interlocking member 9 will move continuously.

[0055] That is, according to this graph, in the process of the interlocking member 9 moving as the engine speed increases and the weight member 8 moves from the inner diameter side position to the outer diameter side position, until the movement amount of the interlocking member 9 becomes α2, the release spring m continues to be compressed (flexed), and when the movement amount of the interlocking member 9 becomes α2 and the pressing load (N) reaches the set load P2 of the clutch spring 11, the clutch spring 11 starts to flex together with the release spring m. After that, when the movement amount of the interlocking member 9 reaches α1, the release spring m reaches the maximum load P1 and the flexing stops, while the flexing (compression) of the clutch spring 11 continues, and it can be seen that the interlocking member 9 moves continuously.

[0056] Therefore, before the moving amount of the interlocking member 9 reaches α1 (before the pressing load reaches P1), until the moving amount of the interlocking member 9 reaches α2, the release spring m deflects alone, and until the moving amount of the interlocking member 9 reaches α1, both the release spring m and the clutch spring 11 deflect. Thus, the interlocking member 9 moves continuously. When the moving amount of the interlocking member 9 reaches α1 and the pressing load reaches the maximum load P1 of the release spring, the deflection of the release spring m disappears, while the clutch spring 11 continues to deflect. Therefore, continuous movement of the interlocking member 9 can be allowed. As a result, the conventional dead zone can be reduced, and the weight member 8 and the interlocking member 9 can be moved smoothly and continuously. Thus, the shock at clutch engagement can be suppressed, and the sudden feeling during power transmission can be suppressed.

[0057] Also, in the present embodiment, no spring or the like is provided between the first clutch member 4a and the second clutch member 4b. However, for example, a buffer member 12 may be disposed between the first clutch member 4a and the second clutch member 4b. In this case, the buffer member 12 is interposed between the first clutch member 4a and the second clutch member 4b, and is configured to be compressed (the spring deflects) in the process of the interlocking member 9 moving and the pressure member 5 moving from the non-operating position to the operating position, thereby allowing the movement of the interlocking member 9 and the pressure member 5 while applying a biasing force.

[0058] More specifically, such a buffer member 12 is composed of a spring set to a load at which it is compressed before the clutch spring 11 starts to be compressed. As shown in FIGS. 2, 3, and 19, it is housed and assembled in a housing recess 4c formed on the surfaces of the first clutch member 4a and the second clutch member 4b facing each other (specifically, the surface of the first clutch member 4a facing the second clutch member 4b).

[0059] This housing recess 4c is formed of an annular groove, and the buffer member 12 is formed of a disc spring formed in an annular shape following the groove shape. Further, as shown in FIG. 19, the housing recess 4c is formed of a groove having an inner diameter side wall surface 4ca and an outer diameter side wall surface 4cb, and the buffer member 12 formed of an annular spring is fitted into the groove following the groove shape.

[0060] Thus, as described above, in the cam for back torque transmission according to the present embodiment, a plurality of annular shapes are formed on the surfaces where the first clutch member 4a and the second clutch member 4b face each other, and as shown in FIG. 6, the housing recess 4c is formed concentrically at a position adjacent to the cam for back torque transmission (on the inner diameter side from the formation position of the cam for back torque transmission in the present embodiment).

[0061] Such a buffer member 12 is set to a load (P3) that is compressed before the clutch spring 11 starts to be compressed. Therefore, as shown in FIG. 23, before the movement amount of the interlocking member 9 becomes α1 (before the pressing load becomes P1), until the movement amount of the interlocking member 9 becomes α2, the release spring m bends alone. Until the movement amount of the interlocking member 9 becomes α3, the two release spring m and the clutch spring 11 bend. After that, until the movement amount of the interlocking member 9 becomes α1, the three release spring m, the clutch spring 11, and the buffer member 12 bend. Therefore, the interlocking member 9 moves continuously, and when the movement amount of the interlocking member 9 becomes α1 and the pressing load reaches the maximum load P1 of the release spring (the maximum load of the buffer member 12), the bending of the release spring m and the buffer member 12 disappears, while the clutch spring 11 continues to bend. Therefore, continuous movement of the interlocking member 9 can be allowed. Therefore, even in this case, the conventional dead zone can be reduced, and the weight member 8 and the interlocking member 9 can be moved smoothly and continuously. Therefore, the shock at the time of clutch engagement can be suppressed, and the sudden feeling at the time of power transmission can be suppressed.

[0062] In addition, when disposing the buffer member 12 as described above, the accommodation recess 4c is formed concentrically on the inner diameter side from the formation position of the back torque transmission cam, but it may be formed concentrically on the outer diameter side from the formation position of the back torque transmission cam. In this case, as shown in FIG. 24, the buffer member 12 may be configured to apply a biasing force in a direction of pressing the driving-side clutch plate 6 and the driven-side clutch plate 7 against a portion (disk pack) where the driving-side clutch plate 6 and the driven-side clutch plate 7 are laminated.

[0063] According to the present embodiment, since the set load of the clutch spring 11 is set smaller than the maximum load of the release spring m, the compression of the release spring m and the compression of the clutch spring 11 are continuously performed, and the interlocking member 9 moves continuously. Thus, it is possible to avoid the occurrence of a dead zone, suppress the sudden feeling during power transmission, and improve the operability.

[0064] Further, when the buffer member 12 is provided, which can apply a biasing force while allowing the movement of the interlocking member 9 and the pressure member 5 by compressing during the process in which the interlocking member 9 moves and the pressure member 5 moves from the non-operating position toward the operating position, the buffer member 12 or the clutch spring 11 is compressed during the compression process of the release spring m, so that the dead zone can be avoided, the sudden feeling during power transmission can be further suppressed, and the operability can be improved. Furthermore, when the buffer member 12 is disposed, the buffer member 12 is composed of a spring set to a load at which it is compressed before the clutch spring 11 starts to be compressed, so that the sudden feeling during power transmission can be more reliably suppressed.

[0065] Furthermore, when the buffer member 12 is disposed, since the buffer member 12 is accommodated in the accommodation recess 4c formed in the surface where the first clutch member 4a and the second clutch member 4b face each other, it is possible to avoid the buffer member 12 being caught and displaced when the second clutch member 4b moves relative to the first clutch member 4a. The accommodation recess 4c is formed in the surface of the first clutch member 4a that faces the second clutch member 4b, but it may also be formed in the surface of the second clutch member 4b that faces the first clutch member 4a.

[0066] Moreover, the above-described accommodation recess 4c is formed as an annular groove, and the buffer member 12 is formed as a spring that is annular following the groove shape. Therefore, the biasing force generated by the buffer member 12 can be applied to the second clutch member 4b and the like substantially uniformly, and the biasing force can be applied stably. Also, the above-described back torque transmission cam is formed in a plurality of annular shapes on the surface where the first clutch member 4a and the second clutch member 4b face each other, and the accommodation recess 4c is formed concentrically at a position adjacent to the back torque transmission cam. Thus, the movement of the second clutch member 4b by the back torque transmission cam and the application of the biasing force by the buffer member 12 can be performed reliably and stably.

[0067] In addition, the bearing holding member C according to the present embodiment is formed of a cylindrical member with one end open, and its open end Ca is fitted and attached (attached in an inlay state) to the recess 4d formed in the clutch member (the first clutch member 4a). Therefore, the assembly of the bearing holding member C can be easily performed, and the bearing holding member C can be operated stably during the shifting operation.

[0068] Further, it is configured to include a release spring m that can apply a biasing force to the pressure member 5 while allowing the movement of the interlocking member 9 and the pressure member 5 until reaching the fastening state before the driving clutch plate 6 and the driven clutch plate 7 are pressed against each other. The release spring m is attached across both the bearing holding member C and the pressure member 5, applies a biasing force to the pressure member 5, and can apply a biasing force to the bearing holding member C to transmit the biasing force to the operating member 10. Therefore, the release spring m can also be used as a spring for preventing play in the shift operation means, and the number of parts can be reduced.

[0069] Furthermore, the release spring m according to the present embodiment is formed of a circular disc spring that can generate a biasing force due to the displacement between the central portion ma and the peripheral portion mb. The central portion ma is attached to the bearing holding member C, and the peripheral portion mb is attached to the pressure member 5. Therefore, the biasing force of the release spring m can be stably applied to both the bearing holding member C and the pressure member 5.

[0070] Still further, the clutch member according to the present embodiment includes a first clutch member 4a connected to the output shaft 3 (output member), a second clutch member 4b to which the driven clutch plate 7 is attached, and a back torque transmission cam that can move the second clutch member 4b to press the driving clutch plate 6 and the driven clutch plate 7 against each other when a rotational force is input to the first clutch member 4a via the output shaft 3 (output member). Since the recess 4d is formed in the first clutch member 4a, it is possible to avoid the bearing holding member C from interfering with the movement of the second clutch member 4b by the back torque transmission cam, and the operation of the bearing holding member C and the movement of the second clutch member 4b by the back torque transmission cam can be made smooth respectively.

[0071] In addition, according to the above embodiment, since the back torque transmission cam can move the second clutch member 4b in a direction approaching the interlocking member 9 to hold the contact between the interlocking member 9 and the weight member 8, the rotational force on the wheel side can be transmitted to the engine side by pressing the driving clutch plate 6 and the driven clutch plate 7 together to generate an engine brake, and the operation by the weight member 8 when the engine brake is generated can be stably performed.

[0072] Further, the back torque transmission cam according to the present embodiment is configured by cam surfaces (K1, T1) integrally formed on each of the first clutch member 4a and the second clutch member 4b. Since the cam surfaces (K1, T1) are formed on the mating surfaces of the first clutch member 4a and the second clutch member 4b respectively, the movement of the second clutch member 2b by the back torque transmission cam can be performed reliably and smoothly.

[0073] Furthermore, a gradient surface 4aa formed on the first clutch member 4a and a gradient surface 5a formed on the pressure member 5 are opposed to each other, and since it is provided with a pressing assist cam for increasing the pressing force between the driving clutch plate 6 and the driven clutch plate 7 when the rotational force input to the input gear 1 (input member) can be transmitted to the output shaft 3 (output member), in addition to the pressing force accompanying the movement of the weight member 8 due to centrifugal force, the pressing force by the pressing assist cam can be applied, and the driving clutch plate 6 and the driven clutch plate 7 can be pressed together more smoothly and reliably.

[0074] Furthermore, the gradient surface 4ab formed on the first clutch member 4a and the gradient surface 5b formed on the pressure member 5 are opposed to each other. When the rotation of the output shaft 3 (output member) exceeds the rotation speed of the input gear 1 (input member) and the clutch member (first clutch member 4a) and the pressure member 5 rotate relative to each other, the cam for back torque limiter is provided so as to be able to release the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7. Therefore, when the weight member 8 is at the outer diameter side position, it is possible to avoid excessive power being transmitted to the engine side via the input gear 1, and since the configuration is such that the cam for back torque transmission is operated before the operation of the cam for back torque limiter, the operation by the cam for back torque transmission can be surely performed.

[0075] In addition, according to the present embodiment, when a rotational force is input to the first clutch member 4a via the output shaft 3 (output member), a cam for back torque transmission that can move the second clutch member 4b to press the driving-side clutch plate 6 and the driven-side clutch plate 7, and torque transmission parts formed on the first clutch member 4a and the second clutch member 4b respectively, which can transmit the rotational force transmitted to the second clutch member 4b to the first clutch member 4a without passing through the cam for back torque transmission (cam surface K1 and cam surface T1), are provided. Therefore, by pressing the driving-side clutch plate 6 and the driven-side clutch plate 7, the rotational force on the wheel side can be transmitted to the engine side to generate an engine brake, and the power transmission can be stably performed when the weight member 8 moves to the outer diameter side position and the pressure member 5 moves to the operating position.

[0076] Also, since movement amount limiting parts are formed on the first clutch member 4a and the second clutch member 4b respectively to limit the movement amount of the second clutch member 4b by the cam for back torque transmission, the movement of the second clutch member 4b by the cam for back torque transmission can be made within a set range.

[0077] Furthermore, a convex portion F is formed on either the first clutch member 4a or the second clutch member 4b, the torque transmission portion is composed of a first contact surface G1 that can receive a rotational force by contacting one side surface F1 of the convex portion F, and the movement amount limiting portion is composed of a second contact surface G2 that can limit the movement amount by contacting the other side surface F2 of the convex portion F. Therefore, the convex portion F can also serve as the torque transmission portion and the movement amount limiting portion.

[0078] As described above, the present embodiment has been explained, but the present invention is not limited to these. For example, as shown in FIGS. 25 and 26, it may be applied to a configuration in which a weight member 8 is disposed movably in the housing portion 2a of the clutch housing 2. Such a power transmission device has the first clutch member 4a, the second clutch member 4b, and a back torque transmission cam, and a buffer member 12 is interposed between the first clutch member 4a and the second clutch member 4b, similar to the above embodiment.

[0079] Also, FIG. 25 shows an embodiment in which a buffer member 12 is attached to the surface of the first clutch member 4a facing the second clutch member 4b, and FIG. 26 shows an embodiment in which a buffer member 12 that applies a biasing force is attached to a portion (disk pack) where the driving-side clutch plate 6 and the driven-side clutch plate 7 of the first clutch member 4a are laminated. The bearing holding member C' is made movable by the operating member 10', and the release spring m' is composed of a coil spring attached across both the bearing holding member C' and the pressure member 5.

[0080] Furthermore, instead of the buffer member 12 made of a disc spring, other elastic members may be used. For example, as shown in Fig. 27, a buffer member 12' made of a wave spring may be disposed in the accommodation recess 4c. Such a wave spring is composed of a C-shaped member having a notch 12'a in a part of an annular shape, and is formed in a waveform (wave shape) in the thickness direction t so as to generate elasticity. It is interposed between the first clutch member 4a and the second clutch member 4b, and is configured to allow the movement of the interlocking member 9 and the pressing member 5 while applying a biasing force by being compressed in the process of the interlocking member 9 moving and the pressing member 5 moving from the non-operating position to the operating position.

[0081] In the power transmission device shown in the same figure, a plurality (three in this embodiment) of communication holes Cc are formed in the side wall of the bearing holding member C, and the oil supplied into the bearing holding member C through the oil flow path r can flow out to the outside. Further, the operating member 10'' is locked to the roller bearing B1 of the bearing holding member C, and is movable in the left-right direction in the figure by the operation of the driver or the operation of the actuator, so that the pressing member 5 can be moved between the operating position and the non-operating position.

[0082] On the other hand, the operating member 10'' according to this embodiment is of a tension type as shown in Fig. 27. When operated manually or by an actuator, it moves to the right side in the figure and pulls the bearing B1 in the same direction, so that the pressing force between the driving-side clutch plate 6 and the driven-side clutch plate 7 can be released. Instead of the buffer member 12 of the power transmission device shown in Fig. 27, as shown in Fig. 30, it may be provided with a buffer member 12' made of a disc spring.

[0083] Furthermore, as shown in FIG. 31, a back torque transmission cam (cam surfaces K1 and T1) may be disposed on the outer peripheral edge portions of the first clutch member 4a and the second clutch member 4b. According to such a power transmission device, since the back torque transmission cam is disposed on the outer peripheral edge portions of the first clutch member 4a and the second clutch member 4b, the action of the cam can be increased, and the moving force (thrust force) of the second clutch member 4b can be set to be large.

[0084] In FIG. 31, a power transmission device in which the buffer members 12 and 12' are not disposed is shown. However, a buffer member 12 formed of a disc spring may be disposed on the inner diameter side of the back torque transmission cam (cam surfaces K1 and T1) (see FIG. 32), or a buffer member 12' formed of a wave spring may be disposed on the inner diameter side of the back torque transmission cam (cam surfaces K1 and T1) (see FIG. 33).

[0085] In the present embodiment, the bearing holding member C is formed of a cylindrical member having one end opened, and the opened end portion Ca thereof is fitted and attached to a recess 4d formed in the clutch member (the first clutch member 4a). However, other shaped bearing holding members may be used, and an attachment structure different from the form of fitting into a recess formed in the clutch member (so-called inlay) may be used. 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, or general-purpose machines, in addition to motorcycles.

Industrial Applicability

[0086] As long as it is a power transmission device having the same gist as the present invention, it can be applied to those having different external shapes or those to which other functions are added.

Explanation of Reference Numerals

[0087] 1 Input gear (input member) 2 Clutch housing 2a Housing portion 2b Cover portion 3 Output shaft (output member) 4a First clutch member 4aa Gradient surface (cam for pressure contact assist) 4ab Gradient surface (cam for back torque limiter) 4ac Flange surface 4ad Insertion hole 4b Second clutch member 4ba Spline fitting portion 4bb Pressing portion 4c Accommodating recess 4d Recess 4da Inner peripheral wall surface 5 Pressure member 5a Gradient surface (cam for pressure contact assist) 5b Gradient surface (cam for back torque limiter) 5c Flange surface 6 Driving side clutch plate 7 Driven side clutch plate 8 Weight member 9 Interlocking member 10 Actuating member 11 Clutch spring 12 Buffer member (disk spring) 12’ Buffer member (wave spring) 12’a Notch portion C Bearing holding member Ca Open end portion Cb Top portion Cc Communication hole K Groove portion K1 Cam surface K2 Wall surface T Protrusion T1 Cam surface T2 Wall surface F Protrusion G Protrusion G1 First contact surface G2 Second contact surface m Release spring r Oil flow path

Claims

1. A clutch member housed in a clutch housing that rotates together with an input member rotated by the driving force of an engine of a vehicle and to which a plurality of driving-side clutch plates are attached, the clutch member having a plurality of driven-side clutch plates alternately formed with the driving-side clutch plates of the clutch housing attached thereto and being connected to an output member capable of rotating a wheel of the vehicle, a pressure member movable between an operating position in which the driving-side clutch plate and the driven-side clutch plate are pressed against each other to transmit the driving force of the engine to the wheel and a non-operating position in which the pressing force between the driving-side clutch plate and the driven-side clutch plate is released to block the transmission of the driving force of the engine to the wheel, a weight member movable from an inner diameter side position to an outer diameter side position by a centrifugal force accompanying the rotation of the clutch housing, a holding member for holding the weight member, a linking member that contacts the weight member and presses the pressure member as the weight member moves from the inner diameter side position to the outer diameter side position, in a power transmission device having the above, the linking member extends in a direction perpendicular to the axis of the output member over the entire length from the inner diameter side end portion to the outer diameter side end portion in a cross section along the axis of the output member, the holding member, has a ring-shaped main body portion, an extending portion extending in the axial direction of the output member from an end portion on the outer side in the radial direction of the main body portion, a plurality of first wall portions formed in the main body portion, extending in the radial direction, and arranged in the circumferential direction, a plurality of first groove portions formed in the main body portion, extending in the radial direction, and formed between adjacent ones of the first wall portions, a plurality of second wall portions formed in the extending portion, extending in the axial direction, and continuous with the first wall portions, a plurality of second groove portions formed in the extending portion, extending in the axial direction, formed between adjacent ones of the second wall portions, and continuous with the first groove portions, and having, a surface on the open end side of the extending portion is a continuous plane over the entire circumferential direction, the outer diameter side end portion of the linking member faces the extending portion, a power transmission device.

2. The power transmission device according to claim 1, wherein a portion of the second groove portion on the open end side is formed in an arc shape when viewed from the axial direction.

3. The power transmission device according to claim 1, wherein a portion of the second groove portion on the open end side is formed in a U shape when viewed from the axial direction.

4. The second groove portion is a plurality of arc-shaped second groove portions in which a portion on the open end side is formed in an arc shape when viewed from the axial direction, and a plurality of U-shaped second groove portions formed between adjacent arc-shaped second groove portions and having a portion on the open end side formed in a U shape when viewed from the axial direction, the power transmission device according to claim 1.

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