Power transmission device

Abstract

A power transmission device K comprises: a clutch member 4 that retains a plurality of driven-side clutch plates 7 which are disposed alternatingly with driving-side clutch plates 6; a centrifugal clutch means 9 that can press the driving-side clutch plates 6 and the driven-side clutch plates 7 to each other, when a weight member 10 is at an outer diameter-side position, to create a state in which a driving power of an engine E can be transmitted to a drive wheel W, and that can release the pressing force between the driving-side clutch plates 6 and the driven-side clutch plates 7, when the weight member 10 is at an inner diameter-side position, to interrupt the transmission of the driving power of the engine E to the drive wheel W; a pressing force amplification mechanism 20 that generates a second pressing force which amplifies the pressing force between the driving-side clutch plates 6 and the driven-side clutch plates 7 in a state in which a rotation force input to an input gear 1 can be transmitted to an output shaft 3; and a suppression member D that suppresses the generation of the second pressing force when a rotation number of the engine E is no more than a prescribed rotation number.

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] As a conventional power transmission device, for example, as disclosed in Patent Document 1, there has been proposed a centrifugal clutch means including a weight member that can move from an inner diameter side position to an outer diameter side position by centrifugal force accompanying the rotation of a clutch housing, thereby bringing a driving side clutch plate and a driven side clutch plate into pressure contact with each other. According to such a conventional power transmission device, when the clutch housing rotates with the driving of a driving source such as an engine, centrifugal force can be applied to the weight member, and the driving side clutch plate and the driven side clutch plate can be brought into pressure contact with each other to transmit the driving force of the engine to the wheels.

[0003] Further, according to the above-described conventional power transmission device, a pressure contact force amplification mechanism is provided that generates a cam thrust for amplifying the pressure contact force between the driving side clutch plate and the driven side clutch plate when the rotational force input to the input member can be transmitted to the output member. Therefore, when the driver performs a clutch operation to bring the driving side clutch plate and the driven side clutch plate into pressure contact with each other, the operating force can be reduced to perform smooth power transmission.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the rotational speed of the engine of the vehicle is equal to or lower than a predetermined rotational speed (for example, when the vehicle is stopped while driving the engine), the pressing force amplification mechanism may inadvertently operate due to the drag torque between the driving clutch plate and the driven clutch plate, causing the driving clutch plate and the driven clutch plate to come into pressure contact and 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 it may not be possible to sufficiently ensure the pressing force between the driving clutch plate and the driven clutch plate, resulting in the inability to sufficiently transmit power. Therefore, it is necessary to amplify the pressing force using a pressing force amplification mechanism. However, in that case, as described above, there is a risk that the pressing force amplification mechanism may inadvertently operate, causing the driving clutch plate and the driven clutch plate to come into pressure contact and resulting in unintended power transmission.

[0007] The present invention has been made in view of such points, and its object is to provide a power transmission device capable of suppressing unintended power transmission when the rotational speed of the drive source is equal to or lower than a predetermined rotational speed.

Means for Solving the Problems

[0008] The power transmission device according to the present invention is housed in a clutch housing that rotates with an input member rotated by the driving force of a driving source and holds a plurality of driving-side clutch plates, and is connected to an output member capable of rotating a wheel. It has a clutch member that holds a plurality of driven-side clutch plates 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 accompanying the rotation of the clutch housing. When the weight member is in the outer diameter side position, the driving-side clutch plate and the driven-side clutch plate are pressed against each other to enable the driving force of the driving source to be transmitted to the wheel. When the weight member is in the inner diameter side position, a centrifugal clutch means that can release the pressing force between the driving-side clutch plate and the driven-side clutch plate to block the transmission of the driving force of the driving source to the wheel, a pressure contact force amplification mechanism that generates a cam thrust that amplifies the pressure contact force between the driving-side clutch plate and the driven-side clutch plate when the rotational force input to the input member can be transmitted to the output member, and a suppression member that suppresses the generation of the cam thrust when the rotational speed of the driving 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 rotational speed of the driving source is equal to or lower than a predetermined rotational speed. According to the above aspect, when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed, the suppression member suppresses the generation of cam thrust by the pressure contact force amplification mechanism, so that it is possible to prevent the pressure contact force amplification mechanism from operating inadvertently and causing power transmission unintentionally.

[0010] Another power transmission device according to the present invention is housed in a clutch housing that rotates with an input member rotated by the driving force of a driving source and holds a plurality of driving-side clutch plates, and is connected to an output member capable of rotating a wheel. A clutch member that holds a plurality of driven-side clutch plates 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 accompanying the rotation of the clutch housing. When the weight member is in the outer diameter side position, the driving-side clutch plate and the driven-side clutch plate are pressed against each other so that the driving force of the driving source can be transmitted to the wheel, and when the weight member is in the inner diameter side position, the driving-side clutch plate and the driven-side clutch plate are pressed against each other. Centrifugal clutch means capable of releasing the pressing force between the driven clutch plates and blocking the transmission of the driving force of the driving source to the wheels, and when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed, the driving-side clutch plate and the driven-side clutch plate are pressed against each other. And a suppressing member that suppresses the transmission of the driving force of the driving source to the wheels.

[0011] Another power transmission device according to the present invention includes a suppressing member that suppresses the driving-side clutch plate and the driven-side clutch plate from being pressed against each other and transmitting the driving force of the driving source to the wheels when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed. According to the above aspect, when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed, the suppressing member suppresses the transmission of the driving force of the driving source, so that it is possible to suppress the power transmission from being performed unintentionally.

Effects of the Invention

[0012] According to the present invention, it is possible to provide a power transmission device capable of suppressing the unintentional power transmission when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] <First Embodiment> Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. As shown in FIG. 14, the power transmission device K is disposed in a vehicle and is for arbitrarily transmitting or interrupting the driving force of the engine E to the driving wheel W side via the transmission M. The engine E is an example of a drive source. The driving wheel W is an example of a wheel. As shown in FIGS. 1 to 13, the power transmission device K includes a clutch housing 2 formed with an input gear 1 that rotates by the driving force of the vehicle 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 laminated state, and a centrifugal clutch means 9 having a weight member 10. In the figure, the reference symbol S 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] When the driving force (rotational force) transmitted from the engine E is input, the input gear 1 is configured to be rotatable about the output shaft 3. The input gear 1 is connected to the clutch housing 2 by a rivet or the like. The clutch housing 2 is formed in a cylindrical shape with the right end side open in FIGS. 2 and 3. The clutch housing 2 rotates together with the input gear 1 by the driving force of the engine E.

[0016] As shown in FIG. 4, the clutch housing 2 is formed with a plurality of notches 2a extending in the circumferential direction. The plurality of drive-side clutch plates 6 are fitted and attached to the notches 2a. That is, the clutch housing 2 holds the plurality of drive-side clutch plates 6. The drive-side clutch plate 6 is composed of a plate material having a substantially annular shape. The drive-side clutch plate 6 rotates with the rotation of the clutch housing 2 and is configured to be movable in the axial direction of the output shaft 3 (i.e., the left-right direction in FIGS. 2 and 3).

[0017] As shown in FIG. 2, the clutch member 4 is housed in the clutch housing 2. The clutch member 4 holds a plurality of driven-side clutch plates 7 arranged alternately with the drive-side clutch plates 6. The clutch member 4 is connected to an output shaft 3 capable of rotating a drive wheel W via a vehicle transmission M. 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 fits into the second clutch member 4b.

[0018] As shown in FIGS. 5A to 7, the first clutch member 4a has an insertion hole 4ac formed at the center. The output shaft 3 is inserted through the insertion hole 4ac, and gears formed with each other are engaged and connected in the rotational direction. That is, the first clutch member 4a is connected 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. A first gradient surface 4aa constituting a cam for pressure contact assist and a third gradient surface 4ab constituting a cam for back torque limiter are formed in the recess A. The first clutch member 4a has a boss portion 4ad. An insertion hole through which a bolt B for connecting the first clutch member 4a and the fixing member 8 is inserted is formed in the boss portion 4ad. The first clutch member 4a penetrates in the axial direction of the output shaft 3 and is provided with a plurality of through holes 4ag arranged in the circumferential direction. The through holes 4ag are located radially outside 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 includes 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 spline fitting portion 4bc is formed on the outer peripheral wall 4be. A driven-side clutch plate 7 is attached to the spline fitting portion 4bc by spline fitting. That is, the second clutch member 4b holds the driven-side clutch plate 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, when a suppression member D described later 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 (the direction of arrow DR2 in FIG. 2). The second clutch member 4b has a plurality of convex portions T arranged in the circumferential direction and capable of being fitted into the concave portion A. As shown in FIG. 9, a second gradient surface 4ba constituting a cam for pressure contact assist and a fourth gradient surface 4bb constituting a cam for back torque limiter are formed on the convex portion T.

[0020] As shown in FIG. 10, the pressure member 5 is composed of a disk-shaped member having a flange portion 5a formed at its peripheral edge. The pressure member 5 is configured to be able to press the drive-side clutch plate 6 and the driven-side clutch plate 7 together with the clutch member 4. By pressing the drive-side clutch plate 6 and the driven-side clutch plate 7 together with the pressure member 5, the driving force of the engine E can be transmitted to the drive wheel W. That is, the drive-side clutch plate 6 and the driven-side clutch plate 7 are arranged in a laminated state 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 the direction approaching the pressure member 5 (the direction of arrow DR2 in FIG. 2), the drive-side clutch plate 6 and the driven-side clutch plate 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 the direction away from the pressure member 5 (the direction of arrow DR1 in FIG. 2), the pressing force between the drive-side clutch plate 6 and the driven-side clutch plate 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 rotational force of the clutch housing 2 is no longer transmitted to the output shaft 3.

[0021] Thus, in a state where the drive-side clutch plate 6 and the driven-side clutch plate 7 are pressed together, the rotational force input to the clutch housing 2 (i.e., the driving force of the engine E) is transmitted to the drive wheel side (i.e., the transmission M) via the output shaft 3. Also, in a state where the pressing between the drive-side clutch plate 6 and the driven-side clutch plate 7 is released, the rotational force input to the clutch housing 2 is not transmitted to the output shaft 3.

[0022] In a state where the first clutch member 4a and the second clutch member 4b are fitted together, the convex portion T is fitted into the concave portion A. Further, in a state where the first clutch member 4a and the second clutch member 4b are fitted together, the first gradient surface 4aa and the second gradient surface 4ba face each other to form a cam for pressure contact assist, and the third gradient surface 4ab and the fourth gradient surface 4bb face each other to form a cam for back torque limiter. As shown in FIG. 8, a housing recess Ta in which a coil spring D2 (see FIG. 3), which will be described later, is housed is formed in the convex portion T.

[0023] The power transmission device K includes a pressure contact force amplification mechanism 20 (see FIG. 18). The pressure contact force amplification mechanism 20 generates a second pressure contact force that amplifies the pressure contact force between the drive-side clutch plate 6 and the driven-side clutch plate 7 as the rotational speed of the engine E increases. The second pressure contact force is an example of a cam thrust. The pressure contact force amplification mechanism 20 generates a second pressure contact force that amplifies the pressure contact force 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 pressure contact force amplification mechanism 20 is configured to generate the second pressure contact force by moving a part of 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 contact force amplification mechanism 20 is configured to generate the second pressure contact force by moving a part of the clutch member 4 (here, the second clutch member 4b) in a direction approaching the pressure member 5 while rotating in a first circumferential direction S1 (see FIG. 5A) about the axis 3C (see FIG. 5A) of the output shaft 3. The pressure contact force amplification mechanism 20 applies the second pressure contact force to the drive-side clutch plate 6 and the driven-side clutch plate 7 in the direction of arrow DR2 in FIG. 2 (the left direction in FIG. 2). The pressure contact force amplification mechanism 20 has a plurality of amplification cams 22. The amplification cams 22 generate the second pressure contact force. The amplification cams 22 are provided at a portion where the first clutch member 4a and the second clutch member 4b can contact each other. The amplification cams 22 are formed in the concave portion A of the first clutch member 4a and the convex portion T of the second clutch member 4b. The amplification cams 22 include a first gradient surface 4aa formed in the concave portion A and a second gradient surface 4ba formed in the convex portion T and sliding on the first gradient surface 4aa. When the amplification cams 22 operate (i.e., when the first gradient surface 4aa and the second gradient surface 4ba slide), the second pressure contact force is generated. In the present embodiment, the pressure contact force amplification mechanism 20 has six amplification cams 22. Note that the number of amplification cams 22 is not limited to six. The amplification cams 22 are an example of the first cam.

[0024] Here, as shown in FIG. 20, when the rotational 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., the state where 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 gradient surface 4aa and the second gradient surface 4ba slide relative to each other, the amplification cam 22 operates, and a force in the direction of arrow c in FIG. 20 is generated on the second clutch member 4b. Then, the second clutch member 4b moves in a direction approaching the pressure member 5 (i.e., the 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.), and a second pressure contact force that amplifies the pressure contact force between the drive-side clutch plate 6 and the driven-side clutch plate 7 is generated.

[0025] On the other hand, as shown in FIG. 22, when the rotation of the output shaft 3 exceeds the rotational speed of the input gear 1 and the clutch housing 2 and back torque occurs, a rotational force in the direction of arrow b in FIG. 22 is applied to the second clutch member 4b. As a result, the third gradient surface 4ab and the fourth gradient surface 4bb slide relative to each other, the back torque limiter cam operates, and the second clutch member 4b moves in a direction away from the pressure member 5 (i.e., the direction of arrow d in FIG. 22), and is configured to release the pressure contact force (here, the second pressure contact force) between the drive-side clutch plate 6 and the driven-side clutch plate 7. Thereby, it is possible to avoid the occurrence of problems in the power transmission device K and the power source (engine E side) due to the 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 the centrifugal force accompanying the rotation of the clutch housing 2. The centrifugal clutch means 9 is disposed on the opening side (the 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 plate 6 and the driven side clutch plate 7 interposed therebetween. Here, the centrifugal clutch means 9 is disposed on the side in the direction of arrow DR1 in FIG. 2 with respect to the pressure member 5. The centrifugal clutch means 9 is configured such that when the weight member 10 is at the outer diameter side position, the driving side clutch plate 6 and the driven side clutch plate 7 are brought into pressure contact with each other so that the driving force of the engine E can be transmitted to the driving wheel W. The centrifugal clutch means 9 is configured to apply a first pressing force to the driving side clutch plate 6 and the driven side clutch plate 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, the weight member 10 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 pressing force between the driving side clutch plate 6 and the driven side clutch plate 7 when the weight member 10 is at the inner diameter side position, thereby blocking the transmission of the driving force of the engine E to the driving wheel W. That is, the centrifugal clutch means 9 is configured to release the first pressing force applied to the driving side clutch plate 6 and the driven side clutch plate 7 when the weight member 10 is at the inner diameter side position, thereby blocking the transmission of the driving force of the engine E to the wheels.

[0027] As shown in FIG. 12, the centrifugal clutch means 9 has 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 accommodated 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) in a state where no centrifugal force is applied. For example, when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed, the weight members 10 are located at the inner diameter side position. The weight members 10 are configured to move radially outward against the biasing force of the spring 11 (i.e., when the rotational speed of the engine E becomes higher than the predetermined rotational speed) and reach an outer diameter side position (see FIG. 17). The predetermined rotational speed is higher than the idling rotational speed.

[0028] As shown in FIG. 12, the centrifugal clutch means 9 has a plurality of pressing 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 pressing cam 18 is an example of the second cam. The pressing cam 18 generates a first pressing force. The pressing cam 18 is provided at a portion where the weight member 10 and the pressed member 13 can contact each other. The pressing cam 18 is formed on the weight member 10 and the pressed member 13. The pressing cam 18 includes an inclined surface 10a formed at the tip (the radially outer tip) of the weight member 10 and an inclined surface 13a formed on the pressed member 13. The inclined surface 10a and the inclined surface 13a are slidably provided. The inclination angle θ1 (see FIG. 15) of the inclined surface 10a and the inclined surface 13a of the pressing cam 18 with respect to the radial direction, which is a direction orthogonal to the axial direction of the output shaft 3, is different from the inclination angle θ2 (see FIG. 18) of the first gradient surface 4aa and the inclination angle θ2 (see FIG. 18) of the second gradient surface 4ba with respect to the radial direction. The inclination angle θ1 is the angle formed by the straight line L1 extending in the radial direction and the inclined surface 10a and the inclined surface 13a. The inclination angle θ2 is the angle formed by the straight line L2 extending in the radial direction and the first gradient surface 4aa and the second gradient surface 4ba. The inclined surface 10a and the inclined surface 13a are an example of a cam surface. The inclination angle θ2 of the first gradient surface 4aa and the inclination angle θ2 of the second gradient surface 4ba with respect to the radial direction are larger than the inclination angle θ1 of the inclined surface 10a and the inclined surface 13a with respect to the radial direction.

[0029] When the weight member 10 moves from the inner diameter side position to 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. Thereby, the driving side clutch plate 6 and the driven side clutch plate 7 are brought into pressure contact. That is, a first pressing force is applied to the driving side clutch plate 6 and the driven side clutch plate 7. When the driving side clutch plate 6 and the driven side clutch plate 7 are brought into pressure contact, the driving force of the engine E is transmitted to the output shaft 3.

[0030] On the one hand, when the centrifugal force decreases, the weight member 10 moves from the outer diameter side position toward the inner diameter side position due to the biasing force of the spring 11, and the second clutch member 4b moves in the direction of arrow DR1 in FIG. 3 due to the biasing force of the coil spring D2 (see FIG. 3), and the pressing contact force between the driving clutch plate 6 and the driven clutch plate 7 is released. By releasing the pressing contact force between the driving clutch plate 6 and the driven 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 driving force of the engine E (for example, a part of the driving force of the engine E) from being transmitted to the drive wheel W when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed (for example, when the weight member 10 is in the inner diameter side position), and the driving clutch plate 6 and the driven clutch plate 7 are in pressing contact. The suppression member D suppresses the generation of the second pressing contact force by the pressing contact force amplification mechanism 20 when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed. The suppression member D suppresses the generation of the second pressing contact force by suppressing the operation of the amplification cam 22 when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed. The suppression member D suppresses the generation of the second pressing contact force in at least a part of the range where the rotational speed of the engine E is lower than the idling rotational speed. In the present embodiment, the suppression member D suppresses the generation of the second pressing contact force in all ranges where the rotational speed of the engine E is lower than the idling rotational speed. The suppression member D allows the generation of the second pressing contact force by the pressing contact force amplification mechanism 20 when the rotational speed of the engine E is higher than a predetermined rotational speed. The suppression member D allows the generation of the second pressing contact force by allowing the operation of the amplification cam 22 when the rotational speed of the engine E is higher than a predetermined rotational speed. The suppression member D includes a stepped portion D1 (see FIG. 6) that engages with the convex portion T of the second clutch member 4b and the coil spring D2 (see FIG. 3). The suppression member D is provided at a portion where the first clutch member 4a and the second clutch member 4b can contact each other.

[0032] As shown in FIGS. 6 and 7, the stepped portion D1 is provided at a portion where the first clutch member 4a and the second clutch member 4b can contact each other. The stepped portion D1 is formed at a predetermined portion of the concave portion A of the first clutch member 4a. When the convex portion T of the second clutch member 4b engages with the stepped portion D1, the sliding between the first gradient surface 4aa and the second gradient surface 4ba is suppressed. By releasing the engagement between the convex portion T and the stepped portion D1, the suppression of the sliding between the first gradient surface 4aa and the second gradient surface 4ba is released.

[0033] As shown in FIG. 3, the coil spring D2 is housed in a housing recess Ta formed in the convex portion T of the second clutch member 4b. One end of the coil spring D2 abuts against a support ring 15 fixed to the first clutch member 4a and is assembled, and biases the second clutch member 4b in the direction of arrow DR1 in FIG. 3 via the convex portion T. That is, the coil spring 16 biases a part of the clutch member 4, the second clutch member 4b, 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) and the direction of the first pressing force applied to the driving-side clutch plate 6 and the driven-side clutch plate 7 by the weight member 10 (the direction of arrow DR2 in FIG. 3) are opposite to each other. 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 orthogonal 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, the sliding between the first gradient surface 4aa and the second gradient surface 4ba is suppressed. When the first pressing force becomes larger than the biasing force of the coil spring D2, the suppression of the sliding between the first gradient surface 4aa and the second gradient surface 4ba is released.

[0034] As shown in FIG. 18, when the weight member 10 is at the inner diameter side position (i.e., when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed), the suppression member D suppresses (e.g., restricts) the operation of the amplification cam 22. When the weight member 10 is at the inner diameter side position, the suppression member D engages (contacts) with a predetermined portion F of the convex portion T to suppress (e.g., restrict) the sliding of the first gradient surface 4aa and the second gradient surface 4ba. That is, the suppression member D suppresses the generation of the second pressing force. 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 approaching 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 side position to the outer diameter side position, the engagement between the suppression member D and the predetermined portion F of the convex portion T is released (i.e., the predetermined portion F of the convex portion T separates from the suppression member D). As shown in FIG. 20, in a state where the engagement between the suppression member D and the predetermined portion F of the convex portion T is released, the suppression member D allows the sliding of the first gradient surface 4aa and the second gradient surface 4ba. The suppression member D can release the suppression of the operation of the amplification cam 22 and operate the amplification cam 22 by the movement of 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 in the process of the weight member 10 moving 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 starts to be transmitted to the driving wheel 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] As shown in FIG. 18, when the weight member 10 is at the inner diameter side position (i.e., when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed), even if a drag torque occurs between the driving clutch plate 6 and the driven clutch plate 7, since the stepped portion D1 is engaged (abutted) with the predetermined portion F of the convex portion T, it is possible to suppress the amplification cam 22 from operating unintentionally. Also, when the weight member 10 is at the inner diameter side position (i.e., when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed), even if a drag torque occurs between the driving clutch plate 6 and the driven clutch plate 7, since the coil spring D2 biases the second clutch member 4b in a direction away from the pressure member 5, it is possible to suppress the amplification cam 22 from operating unintentionally. Further, as shown in FIG. 15, when the rotational 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 the arrow DR2 in FIG. 15 (the 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, since the convex portion T moves in the direction of the arrow DR2 in FIG. 19, the engagement between the stepped 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 separates from the stepped portion D1), and the amplification cam 22 can be operated.

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

[0037] As described above, the power transmission device K of the present embodiment includes a suppression member D that suppresses the driving force of the engine E from being transmitted to the drive wheel W when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed. Here, the suppression member D suppresses the generation of the second pressing force. According to the above aspect, when the rotational speed of the engine E is equal to or lower than a predetermined rotational speed, the suppression member D suppresses the generation of the second pressing force by the pressing force amplification mechanism 20, so that the pressing force amplification mechanism 20 does not inadvertently operate and power transmission is not performed unintentionally. This can be suppressed.

[0038] In the power transmission device K of the present embodiment, the suppression member D suppresses the generation of the second pressing force in at least a part of the range where the rotational speed of the engine E is lower than the idling rotational speed. According to the above aspect, in at least a part of the range where the rotational speed of the engine E is lower than the idling rotational speed, it is possible to suppress the pressing force amplification mechanism 20 from inadvertently operating and power transmission from being performed unintentionally.

[0039] In the power transmission device K of the present 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 wheel W.

[0040] In the power transmission device K of the present embodiment, the suppression member D may suppress the generation of the second pressing force in all ranges where the rotational speed of the engine E is lower than the idling rotational speed. According to the above aspect, in all ranges where the rotational speed of the engine E is lower than the idling rotational speed, it is possible to suppress the pressing force amplification mechanism 20 from inadvertently operating and power transmission from being performed unintentionally.

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

[0042] In the power transmission device K of the present embodiment, 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 clutch plate 6 and the driven clutch plate 7 are pressed into contact and the driving force of the engine E starts to be transmitted to the drive wheels W. According to the above aspect, the release of the suppression of the generation of the second pressing force can be performed smoothly.

[0043] In the power transmission device K of the present embodiment, the suppression member D is provided at 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, since the suppression member D can be arranged by effectively using the space, the power transmission device K can be made compact while including the suppression member D.

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

[0045] In the power transmission device K of the present embodiment, the predetermined rotational speed is higher than the idling rotational speed. According to the above aspect, until the rotational speed of the engine E reaches a rotational speed higher than the idling rotational speed, it is possible to suppress the power transmission mechanism 20 from operating inadvertently and causing power transmission unintentionally.

[0046] In the power transmission device K of the present embodiment, the amplification cam 22 is provided at a portion where the first clutch member 4a and the second clutch member 4b can contact each other. According to the above aspect, since the amplification cam 22 can be arranged by effectively using the space, the power transmission device K can be made compact while including the amplification cam 22.

[0047] In the power transmission device K of the present embodiment, the amplification cam 22 is formed in the concave portion A and the convex portion T. According to the above aspect, the operation of the pressure contact force amplification mechanism 20 can be surely suppressed and released.

[0048] In the power transmission device K of the present embodiment, the amplification cam 22 includes a first gradient surface 4aa formed in the concave portion A, and a second gradient surface 4ba formed in the convex portion T and sliding with the first gradient surface 4aa. According to the above aspect, the pressure contact force amplification mechanism 20 can be smoothly operated between the first gradient surface 4aa and the second gradient surface 4ba.

[0049] In the power transmission device K of the present embodiment, the suppression member D is a stepped portion D1 formed in the concave portion A and engaged with the convex portion T. When the convex portion T and the stepped portion D1 are engaged, the sliding between the first gradient surface 4aa and the second gradient surface 4ba is suppressed. According to the above aspect, the operation of the pressure contact force amplification mechanism 20 can be more surely suppressed.

[0050] In the power transmission device K of the present embodiment, when the engagement between the convex portion T and the stepped portion D1 is released, the suppression of the sliding between the first gradient surface 4aa and the second gradient surface 4ba is released. According to the above aspect, the release of the operation suppression of the pressure contact force amplification mechanism 20 can be more surely performed.

[0051] In the power transmission device K of the present embodiment, the inclination angles θ1 of the inclined surfaces 10a and 13a of the pressing cam 18 with respect to the radial direction, which is the direction orthogonal to the axial direction of the output shaft 3, are different from the inclination angle θ2 of the first gradient surface 4aa and the inclination angle θ2 of the second gradient surface 4ba with respect to the radial direction. According to the above aspect, the first pressing force and the second pressing force can be set to optimal values respectively.

[0052] In the power transmission device K of the present embodiment, the inclination angle θ2 of the first gradient surface 4aa and the inclination angle θ2 of the second gradient 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 amplification mechanism 20 can be made larger.

[0053] In the power transmission device K of the present embodiment, the restraining 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 inadvertent operation of the pressing force amplification mechanism 20 and the unintentional power transmission.

[0054] In the power transmission device K of the present embodiment, the restraining member D is a coil spring D2. According to the above aspect, it is possible to suppress, with a simpler configuration, the inadvertent operation of the pressing force amplification mechanism 20 and the unintentional power transmission.

[0055] In the power transmission device K of the present 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 surely bias the second clutch member 4b in a direction away from the pressure member 5.

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

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

[0058] The power transmission device K of the present embodiment includes a stepped portion D1 and a coil spring D2. According to the above aspect, it is possible to more reliably suppress the power transmission from being performed unintentionally due to the inadvertent operation of the pressure force amplification mechanism 20.

[0059] <Second Embodiment> As shown in FIGS. 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 laminated state, and a centrifugal clutch means 9 having a weight member 10. Note that the same reference numerals are given to the components similar to those in the first embodiment, and the detailed description thereof is 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 arrow DR2 in FIG. 24).

[0061] As shown in FIG. 26, a sixth gradient surface 5b and an eighth gradient surface 5c are formed on the pressure member 5. The pressure member 5 has a plurality of fitting teeth 5e that hold the driven-side clutch plate 7. The plurality of fitting teeth 5e are arranged in the circumferential direction. The fitting teeth 5e are located radially inside the flange portion 5a. The fitting teeth 5e are located radially outside the sixth gradient surface 5b and the eighth gradient surface 5c. The pressure member 5 is provided so as to be able to approach or separate from the clutch member 4. The pressure member 5 is configured to be able to press the driving-side clutch plate 6 and the driven-side clutch plate 7.

[0062] As shown in FIG. 27, a fifth gradient surface 4ae and a seventh gradient surface 4af are formed on the first clutch member 204a. In a state where the first clutch member 204a and the pressure member 205 are assembled, the fifth gradient surface 4ae and the sixth gradient surface 5b face each other to form a cam for a back torque limiter, and the seventh gradient surface 4af and the eighth gradient surface 5c face each other to form a cam for a press contact assist. When the rotational speed of the engine E becomes equal to or higher than a predetermined rotational speed, the seventh gradient surface 4af and the eighth gradient surface 5c slide relative to each other. As a result, the pressure member 205 moves in the direction of arrow DR1 in FIG. 24, and the driving side clutch plate 6 and the driven side clutch plate 7 are pressed into contact with each other. That is, a third pressing force is generated between the driving side clutch plate 6 and the driven side clutch plate 7. On the other hand, when the fifth gradient surface 4ae and the sixth gradient surface 5b slide relative to each other, the pressure member 5 moves in the direction of arrow DR2 in FIG. 24. As a result, the pressing force (here, the third pressing force) between the driving side clutch plate 6 and the driven side clutch plate 7 is released.

[0063] As shown in FIG. 24, the centrifugal clutch means 9 is disposed on the opposite side of the pressure member 205 with the driving side clutch plate 6 and the driven side clutch plate 7 interposed therebetween. Here, the centrifugal clutch means 9 is disposed on the side in the direction of arrow DR2 in FIG. 24 with respect 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 FIG. 24) to an outer diameter side position (see FIG. 30) by a centrifugal force accompanying the rotation of the clutch housing 2. As the weight member 10 moves from the inner diameter side position to the outer diameter side position, the weight member 10 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 FIG. 24).

[0064] The pressing force amplification 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 arrow DR1 in FIG. 24.

[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 pressing force between the driving clutch plate 6 and the driven clutch plate 7. The assist cam mechanism 30 applies the third pressure force to the driving clutch plate 6 and the driven 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 a plurality of assist cams 32. The assist cam 32 includes a seventh gradient surface 4af and an eighth gradient surface 5c. In the present embodiment, the assist cam mechanism 30 has three assist cams 32. Note that the number of assist cams 32 is not limited to three. In the present embodiment, the number of amplification cams 22 is six, and the number of amplification cams 22 is larger than the number of assist cams 32. Note that the number of amplification cams 22 may be the same as the number of assist cams 32.

[0066] The pressure boost mechanism 20 operates when the engine speed range is R5 to R9 as shown by the arrow ER1 in FIG. 31. The pressure boost mechanism 20 starts generating the second pressure boost when the engine speed is R5 and completes the generation of the second pressure boost when the engine speed is R9. The assist cam mechanism 30 operates when the engine speed range is R7 to R10 as shown by the arrow ER2 in FIG. 31. The assist cam mechanism 30 starts generating the third pressure boost when the engine speed is R7 and completes the generation of the third pressure boost when the engine speed is R10. The weight member 10 operates when the engine speed range is R2 to R8 as shown by the arrow ER3 in FIG. 31. The weight member 10 starts moving from the inner diameter side position toward the outer diameter side position when the engine speed is R2 and completes the movement and is located at the outer diameter side position when the engine speed is R8. The suppression member D operates when the engine speed range is R1 to R3 as shown by the arrow ER4 in FIG. 31. That is, the suppression member D suppresses the generation of the second pressure boost by the pressure boost mechanism 20 when the engine speed range is R1 to R3. The suppression member D starts suppressing the generation of the second pressure boost when the engine speed is R1 and releases the suppression of the generation of the second pressure boost when the engine speed is R3. Here, the suppression member D releases the suppression of the generation of the second pressure boost at a specific engine speed R3 excluding the engine speed R4 at which the connection between the drive-side clutch plate 6 and the driven-side clutch plate 7 starts. In FIG. 31, the engine speed RI of the engine E indicates the idling speed, and the engine speed RMAX of the engine E indicates the maximum speed. Also, the connection between the drive-side clutch plate 6 and the driven-side clutch plate 7 starts when the engine speed is R4, and the drive-side clutch plate 6 and the driven-side clutch plate 7 are completely connected when the engine speed is R6. When the engine speed is R4, the driving force of the engine E starts being transmitted to the drive wheel W. Note that the above ranges of each engine speed are not limited to the ranges indicated by the arrows ER1 to ER4.

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

[0068] Here, when the rotational 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., the state where the weight member 10 is located at the outer diameter side position), a first pressing force is applied to the driving clutch plate 6 and the driven clutch plate 7, and the first gradient surface 4aa and the second gradient surface 4ba slide on each other and the seventh gradient surface 4af and the eighth gradient surface 5c slide on each other. As a result, the second clutch member 4b and the pressure member 205 move in the direction of approaching each other, respectively, and a second pressing force and a third pressing force for amplifying the pressing force between the driving clutch plate 6 and the driven clutch plate 7 are generated. That is, when the rotational speed of the engine E reaches a predetermined rotational speed, the pressure force amplification mechanism 20 and the assist cam mechanism 30 operate to apply the second pressing force and the third pressing force to the driving clutch plate 6 and the driven clutch plate 7. At this time, the first pressing force, the second pressing force, and the third pressing force are applied to the driving clutch plate 6 and the driven clutch plate 7. The first pressing force and the second pressing force are applied in the direction from the centrifugal clutch means 9 toward the pressure member 205 (the direction of arrow DR1 in FIG. 24), and the third pressing force is applied in the direction from the pressure member 205 toward the centrifugal clutch means 9 (the direction of arrow DR2 in FIG. 24). When the rotational speed of the engine E is the rotational speed at which the driving force of the engine E is not transmitted to the drive wheel W, the total value of the first pressing force and the second pressing force is larger than the third pressing force. The relationship that the total value of the first pressing force and the second pressing force is larger than the third pressing force holds regardless of whether the driving clutch plate 6 and the driven clutch plate 7 are divided into a plurality of groups. For example, the driving clutch plate 6 and the driven clutch plate 7 are divided into a plurality of groups, and in one of the groups, at least a part of the driving clutch plate 6 and the driven clutch plate 7 are in contact with each other, but in other groups, the driving clutch plate 6 and the driven clutch plate are not in contact with each other, and the above relationship also holds when the driving force of the engine E is not transmitted to the drive wheel W.Further, the rotational speed at which the driving force of the engine E is not transmitted to the drive wheels W means that the driving-side clutch plate 6 and the driven-side clutch plate 7 are not in contact, or that the driving force of the engine E is not transmitted to the drive wheels W in a state where at least a part of the driving-side clutch plate 6 and at least a part of the driven-side clutch plate 7 are in contact. When the weight member 10 is at the outer diameter side position, the total value of the first pressing force and the second pressing force is the same as the total value of the third pressing force and the set load of the clutch spring S.

[0069] On the other hand, when the rotation of the output shaft 3 exceeds the rotational speeds of the input gear 1 and the clutch housing 2 and back torque occurs, the third gradient surface 4ab and the fourth gradient surface 4bb slide relative to each other, and the fifth gradient surface 4ae and the sixth gradient surface 5b slide relative to each other. As a result, the second clutch member 4b and the pressure member 205 move in directions away from each other, and the pressing force (i.e., the second pressing force and the third pressing force) between the driving-side clutch plate 6 and the driven-side clutch plate 7 is released. At this time, the first pressing 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 the 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 fits into the second clutch member 304b. The torsion spring D3 is an example of a suppression member. In the third embodiment, the stepped portion D1 is an example of another suppression member.

[0071] As shown in FIG. 32, the first clutch member 304a includes a housing portion 305 that houses the torsion spring D3, and a holding portion 306 that is formed in the housing portion 305 and holds the torsion spring D3. The holding portion 306 is formed in a columnar shape and extends in the axial direction of the output shaft 3.

[0072] As shown in FIG. 32, the torsion spring D3 is housed in a housing portion 305 formed in the first clutch member 304a. One end of the torsion spring D3 is assembled so as to be able to contact the side wall of the housing portion 305, and the other end is inserted into an insertion hole 307 formed in the second clutch member 304b and contacts 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 of the first circumferential direction S1. The torsion spring D3 is disposed between the first clutch member 304a and the second clutch member 304b. The torsion spring D3 is disposed radially outside the output shaft 3 and radially inside the outer peripheral edge 4bf of the outer peripheral wall 4be of the second clutch member 304b in the radial direction, which is a direction orthogonal to the axial direction of the output shaft 3. 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, the sliding between the first gradient surface 4aa and the second gradient surface 4ba is suppressed. That is, the torsion spring D3 regulates 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 the sliding between the first gradient surface 4aa and the second gradient 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 the present embodiment, the suppressing member D biases the second clutch member 4b in a second circumferential direction S2, which is the opposite direction of the first circumferential direction S1. According to the above aspect, it is possible to suppress, with a simple configuration, the inadvertent operation of the pressing force amplification mechanism 20 and the unintentional power transmission.

[0074] In the power transmission device K of the present embodiment, the suppressing member D is the torsion spring D3. According to the above aspect, it is possible to suppress, with a simpler configuration, the inadvertent operation of the pressing force amplification mechanism 20 and the unintentional power transmission.

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

[0076] In the power transmission device K of the present embodiment, the torsion spring D3 is disposed in the radial direction, which is a direction orthogonal to the axial direction of the output shaft 3, radially outside the output shaft 3 and radially inside the outer peripheral edge 4bf of the outer peripheral wall 4be. According to the above aspect, since the torsion spring D3 can be disposed by effectively using the space, the power transmission device K can be made compact while including the torsion spring D3.

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

[0078] The power transmission device K of the present embodiment includes a stepped portion D1 and a torsion spring D3. According to the above aspect, it is possible to more reliably suppress the power transmission from being inadvertently performed due to the inadvertent operation of the pressure contact force amplification mechanism 20.

[0079] As described above, the preferred embodiments of the present invention have been described. However, the above-described embodiments are merely examples, and the present invention can be implemented in various other forms.

[0080] In each of the above-described embodiments, the engine E is used as the drive source. However, the drive source is not limited to the engine E, and may be, for example, an electric motor or the like.

[0081] In each of the above-described embodiments, the first clutch member 4a had the concave portion A and the second clutch member 4b had the convex portion T, but the present invention is not limited to this. For example, the first clutch member 4a may have the convex portion T and the second clutch member 4b may have the concave portion A.

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

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

[0084] In the third embodiment described above, the suppression member D included the stepped portion D1 and the torsion spring D3, but if only one of them is included, the generation of the second pressing force by the pressing 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-wheel buggies, or general-purpose machines.

Description of Reference Numerals

[0086] 1 Input gear (input member) 2 Clutch housing 3 Output shaft (output member) 4 Clutch member 4a First clutch member 4aa First gradient surface 4ab Third gradient surface 4ae Fifth gradient surface 4af Seventh gradient surface 4ag Through hole 4b Second clutch member 4ba Second gradient surface 4bb Fourth gradient surface 4bc Spline fitting portion 4bd Flange portion 4be Outer peripheral wall 5 Pressure member 5a Flange portion 5b Sixth gradient surface 5c Eighth gradient surface 5e Fitting teeth 6 Driving side clutch plate 7 Driven side clutch plate 9 Centrifugal clutch means 10 Weight member 10a Inclined surface 13 Pressed member 13a Inclined surface 18 Pressing cam (second cam) 20 Pressure force amplification mechanism 22 Amplifying cam (first cam) 30 Assist cam mechanism 32 Assist cam A Recess D Suppressing member D1 Step portion (suppressing member) D2 Coil spring (suppressing member) D3 Torsion spring (suppressing member) E Engine K Power transmission device S Clutch spring T Protrusion Ta Receiving recess W Driving wheel

Claims

1. A clutch member that rotates together with an input member rotated by the driving force of a driving source, is housed in a clutch housing that holds a plurality of driving-side clutch plates, is connected to an output member capable of rotating a wheel, and holds a plurality of driven-side clutch plates arranged alternately with the driving-side clutch plates; A pressure member capable of pressing the driving-side clutch plates and the driven-side clutch plates together with the clutch member; Centrifugal clutch means having 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, bringing the driving-side clutch plate and the driven-side clutch plate into pressure contact to enable transmission of the driving force of the driving source to the wheel, and when the weight member is in the inner diameter side position, releasing the pressing force between the driving-side clutch plate and the driven-side clutch plate to block transmission of the driving force of the driving source to the wheel; A pressure contact force amplification mechanism that generates a cam thrust for amplifying the pressure contact force between the driving-side clutch plate and the driven-side clutch plate in a state where the rotational force input to the input member can be transmitted to the output member; A suppression member that suppresses generation of the cam thrust when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed, and permits generation of the cam thrust when the rotational speed of the driving source is higher than the predetermined rotational speed; and The clutch member includes A first clutch member connected to the output member; and A second clutch member that fits with the first clutch member and holds the driven-side clutch plates, One of the first clutch member and the second clutch member has a recess; The other of the first clutch member and the second clutch member has a protrusion that fits into the recess; The suppression member is a stepped portion formed in the recess and engageable with the protrusion; The stepped portion engages with the protrusion when the rotational speed of the driving source is equal to or lower than the predetermined rotational speed, and the engagement with the protrusion is released when the rotational speed of the driving source is higher than the predetermined rotational speed, a power transmission device.

2. A clutch member that rotates together with an input member rotated by the driving force of a driving source, is housed in a clutch housing that holds a plurality of driving-side clutch plates, is connected to an output member capable of rotating a wheel, and holds a plurality of driven-side clutch plates arranged alternately with the driving-side clutch plates; a pressure member capable of pressing the drive-side clutch plate and the driven-side clutch plate together with the clutch member; a centrifugal clutch means including a weight member movable from a first position where, as the centrifugal force increases with the rotation of the clutch housing, the pressing force between the drive-side clutch plate and the driven-side clutch plate is released to block the transmission of the driving force of the drive source to the wheel, to a second position where the drive-side clutch plate and the driven-side clutch plate are pressed together to enable the transmission of the driving force of the drive source to the wheel; a pressing force amplification mechanism having a first cam that generates a cam thrust for amplifying the pressing force between the drive-side clutch plate and the driven-side clutch plate in a state where the rotational force input to the input member can be transmitted to the output member; a suppression member that suppresses the generation of the cam thrust by suppressing the operation of the first cam when the rotational speed of the drive source is equal to or lower than a predetermined rotational speed, and allows the generation of the cam thrust by allowing the operation of the first cam when the rotational speed of the drive source is higher than the predetermined rotational speed; the clutch member includes a first clutch member connected to the output member; a second clutch member that fits with the first clutch member and holds the driven-side clutch plate; either one of the first clutch member and the second clutch member has a recess; the other of the first clutch member and the second clutch member has a protrusion that fits into the recess; the first cam is formed in the recess and the protrusion, and includes a first gradient surface formed in the recess and a second gradient surface formed in the protrusion and sliding on the first gradient surface; the suppression member is a step portion formed in the recess and engaging with the protrusion; a power transmission device in which the sliding of the first gradient surface and the second gradient surface is suppressed when the protrusion and the step portion are engaged.

3. As the weight member moves from the first position to the second position, the protrusion moves in a direction approaching the pressure member, and the engagement between the protrusion and the step portion is released; The power transmission device according to claim 2, wherein the suppression of the sliding between the first gradient surface and the second gradient surface is released by the release of the engagement between the protrusion and the step portion.

4. A clutch member that rotates together with an input member rotated by a driving force of a driving source and is housed in a clutch housing that holds a plurality of driving-side clutch plates, and is connected to an output member capable of rotating a wheel. A pressure member capable of pressing the driving-side clutch plates and a plurality of driven-side clutch plates alternately arranged with the driving-side clutch plates together with the clutch member. Centrifugal clutch means including a weight member that is movable from a first position where 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 driving source to the wheel as the centrifugal force increases with the rotation of the clutch housing, to a second position where the driving-side clutch plate and the driven-side clutch plate are pressed against each other to enable the transmission of the driving force of the driving source to the wheel. A pressure contact force amplification mechanism that generates a cam thrust for amplifying the pressure contact force between the driving-side clutch plate and the driven-side clutch plate in a state where the rotational force input to the input member can be transmitted to the output member. A suppression member that suppresses the driving-side clutch plate and the driven-side clutch plate from being pressed against each other to transmit the driving force of the driving source to the wheel when the rotational speed of the driving source is equal to or lower than a predetermined rotational speed, and allows the driving-side clutch plate and the driven-side clutch plate to be pressed against each other to transmit the driving force of the driving source to the wheel when the rotational speed of the driving source is higher than the predetermined rotational speed. The weight member is configured to bring the clutch member and the pressure member closer to each other as it moves from the first position to the second position. The pressure contact force amplification mechanism is configured to generate the cam thrust when a part of the clutch member and the pressure member approach each other. The suppression member biases a part of the clutch member in a direction away from the pressure member, a power transmission device.

5. The suppression member is a coil spring, the power transmission device according to claim 4.

6. The axis of the coil spring is parallel to the axis of the output member, the power transmission device according to claim 5.

7. The clutch member includes an outer peripheral wall formed with a spline fitting portion for holding the driven-side clutch plate. The coil spring is disposed between the output member and the outer peripheral wall in a radial direction that is orthogonal to the axial direction of the output member, in the power transmission device according to claim 5 or 6.

8. The clutch member includes a plurality of through holes that penetrate in the axial direction of the output member and are arranged in the circumferential direction, The coil spring is disposed between adjacent ones of the through holes, in the power transmission device according to claim 5 or 6.

9. When the rotational speed of the drive source is equal to or lower than a predetermined rotational speed, the power transmission device further includes another suppression member that suppresses the generation of the cam thrust, The clutch member, a first clutch member connected to the output member, a second clutch member that fits with the first clutch member and holds the driven-side clutch plate, either one of the first clutch member and the second clutch member has a concave portion, the other of the first clutch member and the second clutch member has a convex portion that fits into the concave portion, the other suppression member is a stepped portion that is formed in the concave portion and engages with the convex portion, in the power transmission device according to claim 4.

10. The pressure force amplification mechanism is configured to generate the cam thrust by moving a part of the clutch member in a direction approaching the pressure member while rotating in a first circumferential direction about the axis of the output member, The suppression member biases a part of the clutch member in a second circumferential direction that is opposite to the first circumferential direction, in the power transmission device according to claim 4.

11. The suppression member is a torsion spring, in the power transmission device according to claim 10.

12. The clutch member, a first clutch member connected to the output member, a second clutch member that fits with the first clutch member and holds the driven-side clutch plate, the torsion spring is disposed between the first clutch member and the second clutch member, in the power transmission device according to claim 11.

13. The clutch member includes an outer peripheral wall formed with a spline fitting portion that holds the driven-side clutch plate, the torsion spring is disposed in a radial direction that is orthogonal to the axial direction of the output member, radially outside the output member and radially inside the outer peripheral edge of the outer peripheral wall, in the power transmission device according to claim 11.

14. The clutch member penetrates in the axial direction of the output member and includes a plurality of through holes arranged in the circumferential direction. The torsion spring is disposed between adjacent ones of the through holes. The power transmission device according to claim 11.

15. When the rotational speed of the drive source is equal to or lower than a predetermined rotational speed, it includes another suppression member that suppresses the generation of the cam thrust. The clutch member A first clutch member connected to the output member, A second clutch member that fits with the first clutch member and holds the driven-side clutch plate, and One of the first clutch member and the second clutch member has a concave portion, The other of the first clutch member and the second clutch member has a convex portion that fits into the concave portion, The other suppression member is a stepped portion formed in the concave portion and engaging with the convex portion. The power transmission device according to claim 10.

16. A clutch member that rotates together with an input member rotated by the driving force of a drive source, is housed in a clutch housing that holds a plurality of drive-side clutch plates, and is connected to an output member capable of rotating a wheel, A pressure member capable of pressing the drive-side clutch plates and a plurality of driven-side clutch plates alternately arranged with the drive-side clutch plates together with the clutch member, Centrifugal clutch means including a weight member movable from a first position where the pressing force between the drive-side clutch plate and the driven-side clutch plate is released to block the transmission of the driving force of the drive source to the wheel as the centrifugal force increases with the rotation of the clutch housing, to a second position where the drive-side clutch plate and the driven-side clutch plate are pressed against each other to enable the transmission of the driving force of the drive source to the wheel, A pressure force amplification mechanism that generates a cam thrust for amplifying the pressing force between the drive-side clutch plate and the driven-side clutch plate in a state where the rotational force input to the input member can be transmitted to the output member, A suppression member that suppresses the transmission of the driving force of the drive source to the wheel when the rotational speed of the drive source is equal to or lower than a predetermined rotational speed by pressing the drive-side clutch plate and the driven-side clutch plate together, and permits the transmission of the driving force of the drive source to the wheel when the rotational speed of the drive source is higher than the predetermined rotational speed. The pressure force amplification mechanism is configured to generate the cam thrust by moving a part of the clutch member in a direction approaching the pressure member. The suppression member is a power transmission device that biases a part of the clutch member in a direction away from the pressure member.

17. It is housed in a clutch housing that rotates with an input member rotated by the driving force of a driving source and holds a plurality of driving-side clutch plates, and is connected to an output member capable of rotating a wheel, and a clutch member that holds a plurality of driven-side clutch plates 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, It 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, the driving-side clutch plate and the driven-side clutch plate are brought into pressure contact to transmit the driving force of the driving source to the wheel, and when the weight member is in the inner diameter side position, the pressure contact 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 driving source to the wheel. Centrifugal clutch means, A pressure force amplification mechanism that generates a cam thrust for amplifying the pressure contact force between the driving-side clutch plate and the driven-side clutch plate in a state where the rotational force input to the input member can be transmitted to the output member, A suppression member that suppresses the generation of the cam thrust when the rotational speed of the driving source is between a second rotational speed lower than a first rotational speed at which the weight member starts to move from the inner diameter side position toward the outer diameter side position and a third rotational speed higher than the first rotational speed, and allows the generation of the cam thrust when the rotational speed of the driving source is higher than the third rotational speed. A power transmission device comprising:

18. The power transmission device according to claim 17, wherein the third rotational speed is lower than a fourth rotational speed at which connection between the driving-side clutch plate and the driven-side clutch plate is started.

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