power transmission device

Abstract

To provide a power transmission device capable of increasing a clutch capacity while avoiding an increase in the axial size of the device.SOLUTION: An auxiliary clutch plate 17 having a diameter different from that of each of a driving side clutch plate 6 and a driven side clutch plate 7 is arranged on a clutch housing 2. When the driving side clutch plate 6 and the driven side clutch plate 7 have pressure contact with each other, the auxiliary clutch plate 17 has pressure contact with them to put the driving force of an engine E in the state of being transmitted to driving wheels T, and when the driving side clutch plate 6 and the driven side clutch plate 7 are released from pressure contact force, the pressure contact force of the auxiliary clutch plate 17 is released to cut off the driving force of the engine E from being transmitted to the driving wheels T.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Generally, a power transmission device equipped on a motorcycle is used to freely transmit or cut off the driving force of the engine to the transmission and drive wheels, and has an input member connected to the engine, an output member connected to the transmission and drive wheels, a clutch member connected to the output member, and a pressure member that can be moved toward or away from the clutch member.By bringing the pressure member toward the clutch member, the drive side clutch plate and the driven side clutch plate are pressed together to transmit power, and by moving the pressure member away from the clutch member, the pressure force between the drive side clutch plate and the driven side clutch plate is released, thereby cutting off the transmission of power.

[0003] As a conventional power transmission device, for example, Patent Document 1 discloses a centrifugal clutch means provided with a weight member that can press the driving clutch plate and the driven clutch plate together by moving from an inner diameter side position to an outer diameter side position of the groove due to centrifugal force caused by rotation of the clutch housing. In this conventional power transmission device, when the engine is driven, the clutch housing rotates, which applies centrifugal force to the weight member, causing the driving clutch plate and the driven clutch plate to press together, thereby transmitting the driving force of the engine to the wheels. [Prior art documents] [Patent documents]

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

[0005] However, in the above-described conventional power transmission device, it may be necessary to increase the number of drive-side clutch plates and driven-side clutch plates to achieve the clutch capacity required for the multi-plate clutch. In such a case, simply increasing the number of drive-side clutch plates and driven-side clutch plates in the stacking direction of the multi-plate clutch would result in the device becoming larger in the axial direction, which could exceed the available installation space for the vehicle. Note that this problem is not limited to devices equipped with weight members, but may occur in all multi-plate clutch-type power transmission devices that have drive-side clutch plates and driven-side clutch plates.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a power transmission device that can increase the clutch capacity while avoiding an increase in the axial size of the device. [Means for solving the problem]

[0007] The invention of claim 1 is a clutch member that rotates together with an input member that rotates by the driving force of a vehicle engine, and is housed in a clutch housing to which a plurality of driving-side clutch plates are attached, and has a spline fitting portion formed on its outer surface that fits with inner peripheral edges of a plurality of driven-side clutch plates that are formed alternately with the driving-side clutch plates, and is connected to an output member that can rotate wheels of the vehicle, and has an operating position in which the driving-side clutch plates and the driven-side clutch plates are brought into pressure contact with each other to make it possible to transmit the driving force of the engine to the wheels, and an operating position in which the pressure contact force between the driving-side clutch plates and the driven-side clutch plates is released to make it possible to transmit the driving force of the engine to the wheels. A power transmission device comprising a pressure member movable between a non-operating position and a non-operating position where the transmission of engine driving force to the wheels can be blocked, wherein an auxiliary clutch plate having a diameter smaller than the diameter of the inner peripheral edge of the driven-side clutch plate is disposed on the output member, and when the driving-side clutch plate and the driven-side clutch plate are pressed together, the auxiliary clutch plate is pressed together to enable the transmission of engine driving force to the wheels, and when the pressure between the driving-side clutch plate and the driven-side clutch plate is released, the pressure of the auxiliary clutch plate is released to block the transmission of engine driving force to the wheels.

[0008] The invention of claim 2 is characterized in that, in the power transmission device of claim 1, it includes a weight member that is movable from an inner diameter side position to an outer diameter side position by centrifugal force accompanying rotation of the clutch housing, and when the weight member is in the outer diameter side position, it presses the driving side clutch plate and the driven side clutch plate together and also presses the auxiliary clutch plate so that the driving force of the engine can be transmitted to the wheels, and when the weight member is in the inner diameter side position, it releases the pressing force between the driving side clutch plate and the driven side clutch plate and also releases the pressing force of the auxiliary clutch plate so that the driving force of the engine is cut off from being transmitted to the wheels.

[0009] The invention described in claim 3 is characterized in that, in the power transmission device described in claim 2, at least a portion of the centrifugal clutch means is positioned between the auxiliary clutch plate and the driving side clutch plate and the driven side clutch plate. The invention of claim 4 is characterized in that, in the power transmission device of claim 2 or 3, the centrifugal clutch means is configured to include a retaining member that retains the weight member so that it can move between the inner diameter side position and the outer diameter side position, a pressing member that moves in the stacking direction of the driving side clutch plates and the driven side clutch plates as the weight member moves from the inner diameter side position to the outer diameter side position, thereby pressing the driving side clutch plates and the driven side clutch plates together, and a biasing member that biases the weight member from the outer diameter side position toward the inner diameter side position, and when the weight member is in the outer diameter side position, one of the pressing member and the retaining member presses the driving side clutch plates and the driven side clutch plates together, and the other of the pressing member and the retaining member presses the auxiliary clutch plates together.

[0010] The invention described in claim 5 is characterized in that, in the power transmission device described in any one of claims 1 to 4, the stacked portions of the driving side clutch plate and the driven side clutch plate and the auxiliary clutch plate are arranged offset from each other in the axial direction of the clutch housing.

[0011] The invention of claim 6 is characterized in that in the power transmission device of any one of claims 1 to 5, the auxiliary clutch plate is made up of a plurality of clutch plates. The invention of claim 7 relates to a clutch member that rotates together with an input member that is rotated by the driving force of a vehicle engine and is housed in a clutch housing to which a plurality of driving-side clutch plates are attached, the clutch member having a plurality of driven-side clutch plates that are arranged alternately with the driving-side clutch plates and connected to an output member that can rotate wheels of the vehicle; a pressure member that is movable between an operating position that presses the driving-side clutch plates and the driven-side clutch plates together to make it possible to transmit the driving force of the engine to the wheels, and a non-operating position that releases the pressing force between the driving-side clutch plates and the driven-side clutch plates to cut off the transmission of the driving force of the engine to the wheels; an auxiliary clutch plate disposed on the output member; and a pressure member that is movable between an operating position that presses the driving-side clutch plates and the driven-side clutch plates together to make it possible to transmit the driving force of the engine to the wheels. A power transmission device having a weight member that can be moved from an inner diameter side position to an outer diameter side position by the centrifugal force accompanying the rotation of a housing, and centrifugal clutch means provided between the driving side clutch plate, the driven side clutch plate, and the auxiliary clutch plate, wherein when the weight member is in the outer diameter side position, it presses the driving side clutch plate and the driven side clutch plate together and presses the auxiliary clutch plate so that the driving force of the engine can be transmitted to the wheels, and when the weight member is in the inner diameter side position, it releases the pressing force between the driving side clutch plate and the driven side clutch plate and releases the pressing force of the auxiliary clutch plate so that the transmission of the driving force of the engine to the wheels can be interrupted. The invention described in claim 8 is characterized in that, in the power transmission device described in claim 7, a spline fitting portion is formed on the outer surface of the clutch member into which the inner peripheral edge of the driven side clutch plate fits, and the diameter of the auxiliary clutch plate is smaller than the diameter of the inner peripheral edge of the driven side clutch plate. The invention of claim 9 is characterized in that, in the power transmission device of claim 7 or 8, the auxiliary clutch plate overlaps with at least a portion of the centrifugal clutch means when viewed from the radial direction of the output member. [Effects of the Invention]

[0012] According to the invention of claim 1, auxiliary clutch plates having a different diameter from the drive side clutch plates and driven side clutch plates are arranged in the clutch housing, and when the drive side clutch plates and driven side clutch plates are pressed together, the auxiliary clutch plates are pressed together so that the engine's driving force can be transmitted to the wheels, and when the pressing force between the drive side clutch plates and driven side clutch plates is released, the pressing force of the auxiliary clutch plates is released so that the engine's driving force is not transmitted to the wheels, thereby increasing the clutch capacity while avoiding an increase in the axial size of the device.

[0013] According to the invention of claim 2, there is provided a centrifugal clutch means which, when the weight member is in the outer diameter side position, presses the drive side clutch plate and the driven side clutch plate together, and at the same time presses the auxiliary clutch plate, making it possible to transmit the driving force of the engine to the wheels, and when the weight member is in the inner diameter side position, releases the pressing force between the drive side clutch plate and the driven side clutch plate, and at the same time releases the pressing force of the auxiliary clutch plate, thereby cutting off the transmission of the driving force of the engine to the wheels.Therefore, the centrifugal clutch means can press the drive side clutch plate and the driven side clutch plate together or release the pressing force, as well as press the auxiliary clutch plate together or release the pressing force.

[0014] According to the invention of claim 4, when the weight member is in the outer diameter side position, one of the pressing member and the retaining member presses the drive side clutch plate and the driven side clutch plate together, and the other of the pressing member and the retaining member presses the auxiliary clutch plate.Therefore, the pressing member and the retaining member that constitute the centrifugal clutch means can press the drive side clutch plate and the driven side clutch plate together or release the pressing force, as well as press the auxiliary clutch plate together or release the pressing force.

[0015] According to the invention of claim 5, the stacked portions of the drive side clutch plate and the driven side clutch plate and the auxiliary clutch plate are arranged offset from each other in the axial direction of the clutch housing, thereby reliably avoiding the device from becoming too large in the axial direction.

[0016] According to the invention of claim 6, the auxiliary clutch plate is made up of a plurality of clutch plates, so that the clutch capacity of the auxiliary clutch plate can be increased arbitrarily. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an external view showing a power transmission device according to an embodiment of the present invention; [Figure 2] Cross section of line II-II in Figure 1 [Figure 3] Cross section of line III-III in Figure 1 [Figure 4] FIG. 4 is a perspective view showing a clutch housing in the power transmission device; [Figure 5] FIG. 3 is a three-view diagram showing a first clutch member in the power transmission device. [Figure 6] FIG. 3 is a perspective view showing the first clutch member of the same [Figure 7] FIG. 3 is a three-view diagram showing a second clutch member in the power transmission device. [Figure 8] FIG. 4 is a perspective view showing the second clutch member of the same [Figure 9] Three-view diagram showing a pressure member in the power transmission device [Figure 10] FIG. [Figure 11] FIG. 4 is a vertical cross-sectional view showing a centrifugal clutch means in the power transmission device. [Figure 12] FIG. 10 is a partially cutaway perspective view showing the centrifugal clutch means. [Figure 13] 3A and 3B are three-view diagrams showing a holding member constituting the centrifugal clutch means; [Figure 14] 3A and 3B are three-view diagrams showing a support member constituting the centrifugal clutch means; [Figure 15] 3A and 3B are three-view diagrams showing pressure contact members constituting the centrifugal clutch means; [Figure 16] 4A and 4B are four views showing a weight member constituting the centrifugal clutch means; [Figure 17] Cross section of line XVII-XVII in Figure 16 [Figure 18] FIG. 10 is a plan view showing a state in which the weight member of the centrifugal clutch means is at an inner diameter side position. [Figure 19] FIG. 10 is a plan view showing a state in which the weight member of the centrifugal clutch means is at an outer diameter side position. [Figure 20] 1A and 1B are schematic diagrams illustrating the function of a pressure-contact assist cam and the function of a back torque limiter cam in the power transmission device. [Figure 21] FIG. 1 is a schematic diagram showing a vehicle to which the power transmission device is applied. [Figure 22] FIG. 4 is a cross-sectional view showing a state in which the weight member in the power transmission device is at an inner diameter side position. [Figure 23] FIG. 10 is a cross-sectional view showing a state in which the weight member in the power transmission device is in an intermediate position between an inner diameter side position and an outer diameter side position. [Figure 24] FIG. 4 is a cross-sectional view showing a state in which the weight member in the power transmission device is at an outer diameter side position. [Figure 25] FIG. 10 is a cross-sectional view showing the power transmission device in a state where the weight member is in an outer diameter position and the pressure member is in a non-operating position. [Figure 26] FIG. 10 is a longitudinal cross-sectional view showing a power transmission device according to another embodiment of the present invention (wherein the auxiliary clutch plate is made up of a plurality of clutch plates). [Figure 27] FIG. 10 is a longitudinal cross-sectional view showing a power transmission device according to another embodiment of the present invention (wherein the auxiliary clutch plate is made up of a plurality of clutch plates and overlaps with the stacked portions of the driving-side clutch plate and the driven-side clutch plate). [Figure 28] FIG. 10 is a longitudinal cross-sectional view showing a power transmission device according to another embodiment of the present invention (wherein the auxiliary clutch plate is made up of a plurality of clutch plates and does not have a centrifugal clutch means); [Figure 29] FIG. 1 is a longitudinal cross-sectional view showing a power transmission device according to another embodiment of the present invention (in which the auxiliary clutch plates are made up of a plurality of clutch plates and overlap with the stacked portions of the driving-side clutch plates and the driven-side clutch plates, and no centrifugal clutch means is provided). [Figure 30] FIG. 1 is a longitudinal cross-sectional view showing a power transmission device according to another embodiment of the present invention (in which the auxiliary clutch plate is made up of a plurality of clutch plates, does not have a centrifugal clutch means, and has a pressure-contact assist cam and a back torque limiter cam). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in Figure 21, the power transmission device K of this embodiment is arranged in a vehicle to transmit or block the driving force of the engine E to the driving wheels T via the transmission M. As shown in Figures 1 to 17, it is configured to include a clutch housing 2 having an input gear 1 (input member) formed therein that rotates with the driving force of the vehicle's engine E, an output shaft 3 (output member) connected to the transmission M, clutch members (first clutch member 4a and second clutch member 4b), a pressure member 5, a plurality of driving side clutch plates 6 and a plurality of driven side clutch plates 7, a centrifugal clutch means 9 equipped with a weight member 10, and an auxiliary clutch plate 17.

[0019] The input gear 1 is rotatable around the output shaft 3 when the driving force (rotational force) transmitted from the engine E is input, and is connected to the clutch housing 2 by rivets or the like. The clutch housing 2 is made of a cylindrical member that is open on the right end side in Figures 2 and 3, and is configured to be connected to the input gear 1, so that it can rotate together with the rotation of the input gear 1 due to the driving force of the engine E.

[0020] 4, the clutch housing 2 has a plurality of notches 2a formed around the circumference, and a plurality of drive-side clutch plates 6 are fitted into these notches 2a and attached. Each of these drive-side clutch plates 6 is made of a plate material formed in a substantially annular shape, and is configured to rotate together with the rotation of the clutch housing 2 and to be able to slide in the axial direction (left and right direction in FIGS. 2 and 3).

[0021] The clutch members (first clutch member 4a and second clutch member 4b) are attached 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) that can rotate the driving wheels T via the vehicle's transmission M, and are composed of two members, the first clutch member 4a and the second clutch member 4b, assembled together.

[0022] The first clutch member 4a is configured so that the output shaft 3 is inserted into an insertion hole (see Figures 5 and 6) formed in the center thereof, and the gears formed therein mesh with each other to couple in the direction of rotation. As shown in Figures 5 and 6, the first clutch member 4a is formed with an inclined surface 4aa that constitutes a pressure-contact assist cam and an inclined surface 4ab that constitutes a back torque limiter cam. In the figures, reference numeral 4ac denotes a boss portion in which an insertion hole for a bolt B that couples the first clutch member 4a to the fixed member 8 is formed.

[0023] As shown in Figures 7 and 8, the second clutch member 4b is made of an annular member formed with a flange portion 4bb, and is configured so that driven-side clutch plates 7 are attached by spline fitting to spline fitting portions 4ba formed on the outer circumferential surface. Then, as shown in Figures 2 and 3, a pressure member 5 is assembled to the clutch members (first clutch member 4a and second clutch member 4b), and a plurality of driving-side clutch plates 6 and driven-side clutch plates 7 are attached in an alternately stacked state between the flange portion 5c of the pressure member 5 and the flange portion 4bb of the second clutch member 4b.

[0024] As shown in Figures 9 and 10, the pressure member 5 is a disk-shaped member with a flange portion 5c formed around its periphery, and is movable between an operating position where the driving side clutch plate 6 and the driven side clutch plate 7 are pressed together to enable the transmission of the driving force of the engine E to the wheels, and a non-operating position where the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7 is released to interrupt the transmission of the driving force of the engine E to the wheels.

[0025] More specifically, as shown in Figures 7 and 8, the spline fitting portion 4ba formed on the second clutch member 4b is configured as an uneven shape formed integrally over almost the entire circumference of the outer circumferential side surface of the second clutch member 4b, and the driven-side clutch plate 7 fits into the groove that forms the spline fitting portion 4ba, thereby allowing axial movement of the driven-side clutch plate 7 relative to the second clutch member 4b while restricting movement in the rotational direction, and allowing it to rotate together with the second clutch member 4b.

[0026] The driven-side clutch plates 7 are stacked alternately with the driving-side clutch plates 6, so that adjacent clutch plates 6, 7 can be pressed or released from pressure. That is, both clutch plates 6, 7 are allowed to slide in the axial direction of the second clutch member 4b, and when the clutch plates (6a, 6b, 7a, 7b) are pressed together and the clutch is turned on, 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, and when the pressure of the clutch plates (6a, 6b, 7a, 7b) is released and the clutch is turned off, 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 is no longer transmitted to the output shaft 3.

[0027] When the drive side clutch plate 6 and the driven side clutch plate 7 are pressed together, the rotational force (driving force of the engine E) input to the clutch housing 2 is transmitted to the drive wheel side (transmission M) via the output shaft 3 (output member), and when the pressure contact between the drive side clutch plate 6 and the driven side clutch plate 7 is released, the rotational force (driving force of the engine E) input to the clutch housing 2 is blocked from being transmitted to the output shaft 3 (output member).

[0028] 9 and 10, the pressure member 5 has a plurality of fitting holes 5d (three in this embodiment) formed in the circumferential direction, and a clutch spring S is fitted into each fitting hole 5d. As shown in Fig. 2, the clutch spring S is housed in the fitting hole 5d and one end thereof abuts against the fixed member 8, and is biased in a direction to press the driving-side clutch plates 6 and the driven-side clutch plates 7 together. By operating a clutch operating means (not shown), the driving-side clutch plates 6 and the driven-side clutch plates 7 can be pressed together or released from the pressed contact.

[0029] 5, 6, 9, and 10, the first clutch member 4a is formed with inclined surfaces 4aa and 4ab, and the pressure member 5 is formed with inclined surfaces 5a and 5b facing the inclined surfaces 4aa and 4ab. That is, the inclined surfaces 4aa and 5a come into contact with each other to form a pressure-assist cam, and the inclined surfaces 4ab and 5b come into contact with each other to form a back torque limiter cam.

[0030] Then, when the rotation speed of the engine E increases and the rotational force input to the input gear 1 and the clutch housing 2 can be transmitted to the output shaft 3 via the first clutch member 4a and the second clutch member 4b (the weight member 10 is in the outer diameter side position), as shown in Figure 20(a), a rotational force in the direction a is applied to the pressure member 5, and a force in the direction c in the figure is generated on the pressure member 5 by the action of the pressure contact assist cam. As a result, the pressure member 5 moves in a direction (left side in Figures 2 and 3) where its flange portion 5c comes closer to the flange portion 4bb of the second clutch member 4b, thereby increasing the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7.

[0031] On the other hand, when the rotation of the output shaft 3 exceeds the rotation speed of the input gear 1 and the clutch housing 2 and back torque is generated, as shown in Figure 20(b), a rotational force in the direction b is applied to the clutch member 4, and the back torque limiter cam acts to move the pressure member 5 in the direction d in the figure, thereby releasing the pressure contact force between the drive-side clutch plate 6 and the driven-side clutch plate 7. This makes it possible to avoid problems with the power transmission device K and the power source (engine E side) due to back torque.

[0032] As shown in Figures 11 to 19, the centrifugal clutch means 9 is equipped with a weight member 10 that can be moved from an inner diameter side position (see Figure 18) to an outer diameter side position (see Figure 19) by the centrifugal force associated with the rotation of the clutch housing 2.When the weight member 10 is in the outer diameter side position, it presses the drive side clutch plate 6 and the driven side clutch plate 7 together, making it possible to transmit the driving force of the engine E to the wheels (drive wheels T), and when the weight member 10 is in the inner diameter side position, it releases the pressing force between the drive side clutch plate 6 and the driven side clutch plate 7, thereby cutting off the transmission of the driving force of the engine E to the wheels (drive wheels T).

[0033] Specifically, the centrifugal clutch means 9 is configured to include a weight member 10 formed from a bridge-shaped member, a retaining member 11 to which a support member 13 is attached, a pressure contact member 12, a first spherical member 14, a second spherical member 15, and an urging member 16 formed from a coil spring. The retaining member 11 and the pressure contact member 12 have a plurality of protrusions formed around the circumference, and are fitted into the notches 2a of the clutch housing 2 in the same manner as the drive-side clutch plate 6. This allows the retaining member 11 and the pressure contact member 12 to move in the axial direction of the clutch housing 2 and to rotate together with the clutch housing 2 by engaging with them in the rotational direction.

[0034] 16, the weight member 10 is made up of a piece-shaped member having one surface X and the other surface Y, and as shown in the same figure and in Figure 17, is configured with a through-hole 10a formed penetrating from the one surface X to the other surface Y, an insertion portion 10b formed in the other surface Y, and a groove 10c formed in the one surface X. As shown in Figures 18 and 19, the weight member 10 is accommodated in the accommodation portion 11a of the holding member 11, and is held at an inner diameter side position (see Figure 18) when no centrifugal force is applied, and when centrifugal force is applied, it moves outward against the biasing force of the biasing member 16 to reach an outer diameter side position (see Figure 19).

[0035] The holding member 11 holds the weight member 10 movably between an inner diameter side position and an outer diameter side position, and is made of an annular member, as shown in Fig. 13, and is configured with a plurality of accommodating portions 11a formed in the circumferential direction and accommodating the weight member 10, groove shapes 11b formed in the accommodating portions 11a, and a pressing surface 11c. Each accommodating portion 11a has a concave shape that matches the shape and range of movement of the weight member 10, and is configured so that one end of the biasing member 16 can abut against its inner circumferential wall surface 11aa.

[0036] Furthermore, a support member 13 is fixed to the surface of the holding member 11 on which the accommodation portion 11a is formed. As shown in Fig. 14, the support member 13 has a holding portion 13a formed in the radial direction, and the holding portion 13a fits into a groove 10c of the weight member 10, thereby holding the weight member 10 to the holding member 11. That is, the weight member 10 has a groove 10c formed in the center of one surface X thereof in the direction from an inner diameter side position to an outer diameter side position, and by fitting the holding portion 13a into the groove 10c, the weight member 10 is held so as to be movable in the radial direction (from the inner diameter side position to the outer diameter side position).

[0037] As the weight member 10 moves from the inner diameter side position to the outer diameter side position, the pressing member 12 moves in the stacking direction of the driving side clutch plates 6 and the driven side clutch plates 7 (to the right in Figs. 2 and 3), thereby pressing the driving side clutch plates 6 and the driven side clutch plates 7 together. Specifically, as shown in Fig. 15, the pressing member 12 is made of an annular member and is configured to have a plurality of gradient grooves 12a formed in the circumferential direction, groove shapes 12b formed at the positions where the gradient grooves 12a are formed, and a pressing surface 12c.

[0038] The gradient grooves 12a are formed at positions corresponding to the weight members 10, and are sloped upward from the inside to the outside. As a result, when the clutch housing 2 is stationary, the weight members 10 are held in their inner diameter position by the biasing force of the biasing member 16, and when the clutch housing 2 rotates, centrifugal force is applied to the weight members 10, causing them to move along the upward gradient grooves 12a, and the pressing members 12 move in a direction away from the holding member 11 (i.e., in a direction to press the driving-side clutch plate 6 and the driven-side clutch plate 7 into contact with each other).

[0039] Thus, when the retaining member 11 and the pressure contact member 12 are assembled with the weight member 10 interposed therebetween, as shown in Figures 11 and 12, the sloped grooves 12a are positioned corresponding to each weight member 10, and the centrifugal force causes the weight member 10 to move from the inner diameter side position to the outer diameter side position along the sloped grooves 12a, causing the pressure contact member 12 to move in the direction of the arrow in Figure 11 (to the right in the figure), and the pressing surface 12c formed on the pressure contact member 12 presses against the driving side clutch plate 6 and the driven side clutch plate 7 to bring them into a pressed state, and the retaining member 11 moves in the opposite direction of the arrow in Figure 11 (to the left in the figure) due to the reaction force, and the pressing surface 11c formed on the retaining member 11 presses against the auxiliary clutch plate 17.

[0040] 18 and 19, the weight members 10 according to this embodiment are accommodated in a plurality of accommodation sections 11a formed around the circumference of the holding member 11 and are movable in the radial direction, and a plurality of biasing members 16 (two for each in this embodiment) are arranged around the circumference between the weight members 10 and inner circumferential wall surfaces 11aa (see FIG. 13) of the accommodation sections 11a to bias the weight members 10 from an outer diameter side position toward an inner diameter side position. Here, the inner circumferential wall surface 11aa of the accommodation sections 11a is a flat surface that abuts against one end of the biasing members 16, allowing the biasing members 16 to be attached in a stable state.

[0041] Furthermore, the weight member 10 according to this embodiment has a tunnel-shaped insertion portion 10b formed therein, with the surface facing the holding member 11 (the other surface Y in FIG. 17) open, through which the biasing member 16 can be inserted and attached. By accommodating the weight member 10 with the biasing member 16 inserted into the insertion portion 10b in the accommodation portion 11a of the holding member 11, the biasing member 16 is attached between the weight member 10 and an inner circumferential wall surface 11aa of the accommodation portion 11a. The biasing member 16 is disposed such that one end abuts against the inner circumferential wall surface 11aa and the other end abuts against an end wall surface 10ba of the insertion portion 10b, and is capable of biasing the weight member 10 from an outer diameter side position toward an inner diameter side position.

[0042] The first spherical member 14 consists of a steel ball attached to the weight member 10, and as shown in Figures 16 and 17, a portion of it protrudes from one opening 10aa (a small-diameter opening on one surface X) of a through hole 10a formed in the weight member 10, allowing it to roll in contact with the rolling surface of the pressure contact member 12. The second spherical member 15 consists of a steel ball attached to the weight member 10, and as shown in Figures 16 and 17, a portion of it protrudes from the other opening 10ab (a large-diameter opening on the other surface Y) of a through hole 10a formed in the weight member 10, allowing it to roll in contact with the rolling surface of the holding member 11.

[0043] 17, through hole 10a according to this embodiment is tapered so that the diameter continuously increases from one opening 10aa (a small-diameter opening on one surface X side) to the other opening 10ab (a large-diameter opening on the other surface Y side), and first spherical member 14 is retained by the outer circumferential edge of the smaller-diameter opening of openings 10aa and 10ab (in this embodiment, opening 10aa on one surface X side). That is, first spherical member 14 and second spherical member 15 according to this embodiment are spherical members of different diameters (second spherical member 15 is a member with a larger diameter than first spherical member 14) that correspond to the inner diameter of through hole 10a, and first spherical member 14, which has a smaller diameter, is retained by the opening edge on the small-diameter side of through hole 10a and is able to roll in contact with the inner circumferential surface of through hole 10a.

[0044] 11 and 12, the second spherical member 15 is prevented from coming off by the rolling surface of the retaining member 11. As a result, the small-diameter first spherical member 14 is prevented from coming off by the opening edge on the small-diameter side of the through hole 10a, and the large-diameter second spherical member 15 is prevented from coming off by the rolling surface of the retaining member 11, with a portion of the large-diameter second spherical member 15 protruding from the opening on the large-diameter side of the through hole 10a. In this embodiment, the large-diameter second spherical member 15 is assembled facing the rolling surface of the retaining member 11, but the second spherical member 15 may also be assembled facing the rolling surface of the press contact member 12. In this case, the small-diameter first spherical member 14 is prevented from coming off by the opening edge on the small-diameter side of the through hole 10a, and the large-diameter second spherical member 15 is prevented from coming off by the rolling surface of the press contact member 12, with a portion of the large-diameter second spherical member 15 protruding from the opening on the large-diameter side of the through hole 10a.

[0045] However, the rolling surface of the retaining member 11 (the rolling surface of the second spherical member 15 in this embodiment) is formed with a groove shape 11b along the movement direction of the weight member 10 (the direction connecting the inner diameter side position and the outer diameter side position) as shown in Figure 13, and the rolling surface of the pressure-contact member 12 (the rolling surface of the first spherical member 14 in this embodiment) is formed with a groove shape 12b along the movement direction of the weight member 10 (the direction connecting the inner diameter side position and the outer diameter side position) as shown in Figure 15.

[0046] Furthermore, as shown in Figures 16, 18, and 19, the first spherical members 14 and second spherical members 15 in this embodiment are each formed in multiple numbers (two first spherical members 14 and two second spherical members 15 in this embodiment) along the circumferential direction of the retaining member 11 (width direction of the weight member 10), so that as the weight member 10 moves, the first spherical members 14 and second spherical members 15 can each roll within the through hole 10a and move along the groove shapes 11b and 12b.

[0047] The auxiliary clutch plates 17 are arranged inside the clutch housing 2 and are made of an annular member having a different diameter from the drive-side clutch plates 6 and the driven-side clutch plates 7 (in this embodiment, smaller diameter than the drive-side clutch plates 6 and the driven-side clutch plates 7). As shown in Figures 2 and 3, the output shaft 3 (output member) is inserted into the central opening 17a to be fitted, and the auxiliary clutch plates 17 have a pressed surface 17b facing the pressing surface 11c of the holding member 11.

[0048] When the weight member 10 is in the outer diameter side position (i.e., when the driving side clutch plate 6 and the driven side clutch plate 7 are in a pressed contact state), the auxiliary clutch plate 17 is pressed by the pressing surface 11c formed on the holding member 11 and is in pressed contact, so that it can transmit the driving force of the engine E to the output shaft 3. Also, when the weight member 10 is in the inner diameter side position (i.e., when the pressing force of the driving side clutch plate 6 and the driven side clutch plate 7 is released), the pressing force by the pressing surface 11c formed on the holding member 11 decreases and the pressing force is released, so that it can block the transmission of the driving force of the engine E to the output shaft 3.

[0049] That is, when the weight member 10 moves to the outer diameter side position, the inclined groove 12a functions as a cam, and the holding member 11 and the pressing member 12 move in directions away from each other. As a result, the pressing surface 12c of the pressing member 12 presses against the driving-side clutch plate 6 and the driven-side clutch plate 7, and the pressing surface 11c of the holding member 11 presses against the pressed surface 17b of the auxiliary clutch plate 17, so that the driving force of the engine E is transmitted to the drive wheels T.

[0050] Furthermore, as shown in Figures 5 and 6, the first clutch member 4a in this embodiment has an abutment surface 4ad formed on a part of the surface facing the pressure member 5, and as shown in Figures 9 and 10, the pressure member 5 has an abutment surface 5e formed on a part of the surface facing the first clutch member 4a.When the first clutch member 4a, the second clutch member 4b, and the pressure member 5 are assembled (a state in which no torque is transmitted from the input gear 1 (input member) to the output shaft 3 (output member)), the abutment surface 4ad and the abutment surface 5e are in abutment with each other, as shown in Figures 2 and 3.

[0051] In this manner, when the contact surface 4ad and the contact surface 5e are in contact with each other, relative movement between the first clutch member 4a and the pressure member 5 is not permitted during the process in which the weight member 10 of the centrifugal clutch means 9 moves from the inner diameter side position (see Figure 22) to the intermediate position (see Figure 23) and the torque transmitted from the input gear 1 (input member) to the output shaft 3 (output member) increases, and therefore the operation of the pressure-assist cam is restricted.

[0052] Thereafter, the weight member 10 of the centrifugal clutch means 9 moves further from the intermediate position (see FIG. 23) toward the outer diameter side position (see FIG. 24) and is pressed against the flange portion 4bb of the second clutch member 4b, thereby pressing the driving side clutch plate 6 and the driven side clutch plate 7 together, and when the pressing force of the flange portion 4bb exceeds the biasing force of the clutch spring S, the second clutch member 4b and the pressure member 5 are moved in the axial direction (to the right in FIGS. 2 and 3) relative to the first clutch member 4a, causing the contact surface 4ad of the first clutch member 4a and the contact surface 5e of the pressure member 5 to separate. Note that FIG. 25 shows a state in which the weight member 10 is in the outer diameter side position and the pressure member 5 is in the inoperative position (clutch-off state).

[0053] In this manner, when the contact surface 4ad and the contact surface 5e are separated, relative movement between the first clutch member 4a and the pressure member 5 is permitted during the process in which the weight member 10 of the centrifugal clutch means 9 moves from the inner diameter side position to the outer diameter side position and the torque transmitted from the input gear 1 (input member) to the output shaft 3 (output member) increases, and therefore operation of the pressure-assist cam is permitted.

[0054] In other words, according to this embodiment, when the driving side clutch plate 6 and the driven side clutch plate 7 are pressed together, the auxiliary clutch plate 17 is pressed together, making it possible to transmit the driving force of the engine E to the wheels (driving wheels T), and when the pressing force between the driving side clutch plate 6 and the driven side clutch plate 7 is released, the pressing force of the auxiliary clutch plate 17 is released, thereby blocking the transmission of the driving force of the engine E to the wheels (driving wheels T).

[0055] More specifically, in this embodiment, a centrifugal clutch means 9 equipped with a weight member 10 is provided, and when the weight member 10 is in the outer diameter position, it presses the drive side clutch plate 6 and the driven side clutch plate 7 together, and at the same time presses the auxiliary clutch plate 17 together, making it possible to transmit the driving force of the engine E to the wheels (drive wheels T), and when the weight member 10 is in the inner diameter position, it releases the pressure between the drive side clutch plate 6 and the driven side clutch plate 7, and at the same time releases the pressure of the auxiliary clutch plate 17, making it possible to block the transmission of the driving force of the engine E to the wheels (drive wheels T).

[0056] In particular, in this embodiment, when the weight member 10 is in the outer diameter side position, the pressing member 12 and the holding member 11 move in directions away from each other, the pressing member 12 presses the driving side clutch plate 6 and the driven side clutch plate 7 together, and the holding member 11 presses the auxiliary clutch plate 17. Note that the centrifugal clutch means 9 may be arranged so that when the weight member 10 is in the outer diameter side position, the pressing member 12 and the holding member 11 move in directions away from each other, the holding member 11 presses the driving side clutch plate 6 and the driven side clutch plate 7 together, and the pressing member 12 presses the auxiliary clutch plate 17 together.

[0057] According to this embodiment, auxiliary clutch plates 17 having a different diameter from the drive side clutch plates 6 and the driven side clutch plates 7 are arranged in the clutch housing 2, and when the drive side clutch plates 6 and the driven side clutch plates 7 are pressed together, the auxiliary clutch plates 17 are pressed together so that the driving force of the engine E can be transmitted to the wheels (drive wheels T), and when the pressing force between the drive side clutch plates 6 and the driven side clutch plates 7 is released, the pressing force of the auxiliary clutch plates 17 is released, blocking the transmission of the driving force of the engine E to the wheels (drive wheels T).This allows the clutch capacity to be increased while avoiding an increase in the axial size of the device.

[0058] In particular, the auxiliary clutch plates 17 in this embodiment are arranged inside the clutch housing 2 on the inner diameter side of the stacked portion (multi-plate clutch portion) of the drive side clutch plates 6 and the driven side clutch plates 7, so that it is possible to increase the clutch capacity while avoiding an increase in size not only in the axial direction of the device but also in the direction perpendicular to the axial direction of the device, and it is possible to effectively utilize the space on the inner diameter side inside the clutch housing 2.

[0059] Furthermore, according to this embodiment, when the weight member 10 is in the outer diameter side position, the centrifugal clutch means 9 presses the drive side clutch plate 6 and the driven side clutch plate 7 together, and at the same time presses the auxiliary clutch plate 17 together, making it possible to transmit the driving force of the engine E to the wheels (drive wheels T), and when the weight member 10 is in the inner diameter side position, the centrifugal clutch means 9 releases the pressing force between the drive side clutch plate 6 and the driven side clutch plate 7, and at the same time releases the pressing force of the auxiliary clutch plate 17, thereby cutting off the transmission of the driving force of the engine E to the wheels (drive wheels T).Therefore, the centrifugal clutch means 9 can press the drive side clutch plate 6 and the driven side clutch plate 7 together or release the pressing force, as well as press the auxiliary clutch plate 17 together or release the pressing force.

[0060] Furthermore, when the weight member 10 is in the outer diameter side position, one of the pressing member 12 and the holding member 11 presses the driving side clutch plate 7 and the driven side clutch plate 12 together, and the other of the pressing member 12 and the holding member 11 presses the auxiliary clutch plate 17 together. Therefore, the pressing member 12 and the holding member 11 that constitute the centrifugal clutch means 9 can press the driving side clutch plate 6 and the driven side clutch plate 7 together or release the pressing force, as well as press the auxiliary clutch plate 17 together or release the pressing force.

[0061] However, according to the power transmission device K of this embodiment, the through hole 10a of the weight member 10 in the centrifugal clutch means 9 is formed in a tapered shape from one opening 10aa to the other opening 10ab, and the first spherical member 14 is prevented from coming off at the outer peripheral edge of the smaller-diameter opening of the one opening 10aa and the other opening 10ab. Therefore, the first spherical member 14 can be easily and accurately attached to the weight member 10, thereby reducing manufacturing costs.

[0062] Furthermore, the first spherical member 14 and the second spherical member 15 are made of spherical members of different diameters corresponding to the inner diameter of the through hole 10a, and are capable of rolling while in contact with the inner circumferential surface of the through hole 10a, so that the first spherical member 14 and the second spherical member 15 can roll stably and smoothly when the weight member 10 moves. Furthermore, the second spherical member 15 according to this embodiment is prevented from coming off by the rolling surface of the retaining member 11 or the pressing member 12, so that the first spherical member 14 and the second spherical member 15 can be easily prevented from coming off by assembling the retaining member 11 and the pressing member 12.

[0063] Furthermore, the rolling surface of the retaining member 11 or the pressing member 12 is formed with a groove shape (11b, 12b) that follows the movement direction of the weight member 10, thereby ensuring smoother movement of the weight member 10 while reliably preventing the second spherical member 15 from coming off on the large-diameter opening side and the first spherical member 14 from coming off on the small-diameter opening side.

[0064] In addition, the weight members 10 according to this embodiment are accommodated in a plurality of accommodation sections 11a formed around the circumferential direction of the holding member 11, and are movable in the radial direction, and multiple biasing members 16 are arranged around the circumferential direction between the inner wall surface 11aa of the accommodation section 11a and the weight members 10, biasing the weight members 10 from the outer diameter side position toward the inner diameter side position. This allows the weight members 10 to be biased from the outer diameter side position toward the inner diameter side position with high precision, and allows the weight members 10 to be moved stably in accordance with centrifugal force.

[0065] Furthermore, weight member 10 according to this embodiment is formed with insertion portion 10b through which biasing member 16 can be inserted and attached while leaving the surface facing holding member 11 open, which facilitates assembly of biasing member 16 to weight member 10. Furthermore, weight member 10 according to this embodiment is formed with groove 10c in the direction from the inner diameter side position to the outer diameter side position, and holding member 11 (specifically, support member 13 fixed to and integrated with holding member 11) is formed with holding portion 13a that fits into groove 10c and holds weight member 10, which enables stable movement of weight member 10.

[0066] Furthermore, the centrifugal clutch means 9 of this embodiment is configured to include a first spherical member 14, part of which protrudes from one opening 10aa of the through hole 10a formed in the weight member 10 and is capable of rolling by contacting the rolling surface (groove shape 11b) of the holding member 11, and a second spherical member 15, part of which protrudes from the other opening 10ab of the through hole 10a formed in the weight member 10 and is capable of rolling by contacting the rolling surface (groove shape 12b) of the pressure-contacting member 12, thereby allowing the weight member 10 to move more stably.

[0067] In particular, the retaining member 11 or the pressing member 12 has a groove shape (11b, 12b) that follows the movement direction of the weight member 10, and the groove shape (11b, 12b) serves as the rolling surface of the first spherical member 14 or the second spherical member 15, allowing the weight member 10 to move more smoothly. Furthermore, in this embodiment, multiple first spherical members 14 and multiple second spherical members 15 are formed around the circumferential direction of the retaining member 11 (the width direction of the weight member 10), allowing the weight member 10 to move more stably.

[0068] Although the present embodiment has been described above, the present invention is not limited thereto. For example, as shown in FIG. 26, the auxiliary clutch plates 17 may be composed of a plurality of clutch plates. In this case, a multi-plate clutch is formed by including first auxiliary clutch plates 17c and second auxiliary clutch plates 17d in addition to the auxiliary clutch plates 17 connected to the output shaft 3, and when the weight member 10 of the centrifugal clutch means 9 moves to its outer diameter position and the retaining member 11 moves, the pressing surface 11c of the retaining member 11 presses the second clutch plates 17d, thereby pressing the auxiliary clutch plates 17, the first auxiliary clutch plates 17c, and the second auxiliary clutch plates 17d together, enabling the driving force of the engine E to be transmitted to the wheels (drive wheels T). In this way, if the auxiliary clutch plates 17 are composed of a plurality of clutch plates, the clutch capacity of the auxiliary clutch plates 17 (a multi-plate clutch including the first auxiliary clutch plates 17c and the second auxiliary clutch plates 17d) can be increased as desired.

[0069] 27, the auxiliary clutch plates 17 may be made up of a plurality of clutch plates (a multi-plate clutch including first auxiliary clutch plates 17c and second auxiliary clutch plates 17d) and may overlap with the stacked portions of the driving-side clutch plates 6 and the driven-side clutch plates 7 in the axial direction X of the clutch housing 2. In this way, by arranging the stacked portions of the driving-side clutch plates 6 and the driven-side clutch plates 7 and the auxiliary clutch plates 17 so as to overlap with each other in the axial direction X of the clutch housing 2, it is possible to reliably prevent the device from becoming large in size in the axial direction X.

[0070] Furthermore, as shown in Fig. 28, the auxiliary clutch plates 17 may be made up of a plurality of clutch plates and have an interlocking member 18 instead of centrifugal clutch means, as shown in Fig. 29, the auxiliary clutch plates 17 may be made up of a plurality of clutch plates that overlap the stacked portions of the driving-side clutch plates 6 and the driven-side clutch plates 7 and have an interlocking member 18 instead of centrifugal clutch means, and as shown in Fig. 30, the auxiliary clutch plates 17 may be made up of a plurality of clutch plates and have an interlocking member 18 instead of the centrifugal clutch means, and also have a pressure-assist cam and a back torque limiter cam. When the pressure member 5 operates to press the driving-side clutch plates 6 and the driven-side clutch plates 7 together, the interlocking member 18 moves toward the auxiliary clutch plates 17 by the pressure force and presses the auxiliary clutch plates 17 into contact.

[0071] In this embodiment, the second spherical member 15 is retained by the rolling surface (groove shape 11a) of the retaining member 11 (or the pressure contact member 12), but may be retained by other retaining means and methods, such as crimping. Furthermore, in this embodiment, when the first clutch member 4a, the second clutch member 4b, and the pressure member 5 are assembled (when no torque is transmitted from the input gear 1 (input member) to the output shaft 3 (output member)), the contact surface 4ad and the contact surface 5e are in contact with each other, but the contact surface 4ad and the contact surface 5e may not be present and may be spaced apart. The power transmission device of the present invention can be applied to various multi-plate clutch power transmission devices, such as those for automobiles, three- or four-wheeled buggies, and general-purpose machines, in addition to motorcycles. [Industrial Applicability]

[0072] As long as the power transmission device has auxiliary clutch plates of a different diameter than the drive side clutch plates and driven side clutch plates arranged in a clutch housing, and when the drive side clutch plates and driven side clutch plates are pressed together, the auxiliary clutch plates are pressed together to enable the engine's driving force to be transmitted to the wheels, and when the pressing force between the drive side clutch plates and driven side clutch plates is released, the pressing force of the auxiliary clutch plates is released to block the engine's driving force from being transmitted to the wheels, the device can be applied to devices with different external shapes or with added functions. [Explanation of symbols]

[0073] 1 Input gear (input member) 2 Clutch housing 2a notch 3 Output shaft (output member) 4a First clutch member 4aa Inclined surface (pressure-assist cam) 4ab slope surface (back torque limiter cam) 4ac boss part 4ad Contact surface 4b Second clutch member 4ba spline fitting 4bb flange 5 Pressure member 5a Inclined surface (pressure-assist cam) 5b Inclined surface (back torque limiter cam) 5c Flange 5d inset hole 5e Contact surface 6 Drive side clutch plate 7 Driven side clutch plate 8 Fixing member 9. Centrifugal clutch means 10 Weight member 10a through hole 10b Insertion part 10aa One opening 10ab other opening 10ba end wall 10c groove 11 Retaining member 11a Storage section 11aa Inner wall surface 11b Groove shape 11c Pressing surface 12 Pressure welding member 12a Gradient groove 12b Groove shape 12c Pressing surface 13 Support member 13a Holding part 14 First spherical member 15 Second spherical member 16. Pressurizing member 17 Auxiliary clutch plate 17a central opening 17b Pressed surface 17c First auxiliary clutch plate 17d Second auxiliary clutch plate 18 Interlocking members S clutch spring

Claims

1. a clutch member that rotates together with an input member that rotates by the driving force of the engine of the vehicle and is housed in a clutch housing to which a plurality of drive-side clutch plates are attached, the clutch member being connected to an output member that can rotate the wheels of the vehicle; a pressure member that is movable between an operating position where the driving side clutch plates are pressed against the driven side clutch plates that are alternately arranged with the driving side clutch plates to enable transmission of the driving force of the engine to the wheels, and a non-operating position where the pressing force between the driving side clutch plates and the driven side clutch plates is released to interrupt 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 rotation of the clutch housing; and a pressing member provided so as to be able to come into contact with the weight member and which moves in a direction to press the driving side clutch plates and the driven side clutch plates together as the weight member moves from the inner diameter side position to the outer diameter side position, the centrifugal clutch means being configured to press the driving side clutch plates and the driven side clutch plates together when the weight member is at the outer diameter side position, thereby enabling transmission of the driving force of the engine to the wheels, and to release the pressing force between the driving side clutch plates and the driven side clutch plates when the weight member is at the inner diameter side position, thereby interrupting transmission of the driving force of the engine to the wheels, The pressure contact member is a circular main body portion; a plurality of protrusions that protrude from the main body in the axial direction of the output member so as to approach the weight member from the inner diameter side to the outer diameter side, that come into contact with the weight member, and that are aligned in the circumferential direction of the main body; a plurality of protrusions that protrude radially outward from the outer circumferential edge of the main body and are attached to the clutch housing; the pressing member is configured to move in the axial direction and press the driving side clutch plate and the driven side clutch plate into pressure contact as the weight member moves from the inner diameter side position to the outer diameter side position along the convex portion, a power transmission device in which, when viewed in the axial direction of the output member, some of a plurality of straight lines passing through the center of the main body portion and the circumferential center of the protrusion overlap with the convex portion, and other parts of the plurality of straight lines do not overlap with the convex portion.

2. the main body portion includes a plurality of flat surfaces formed between adjacent convex portions and on the radially outer side of which the protrusions are located, 2. The power transmission device according to claim 1, wherein, in some of the plurality of planes, when viewed in the axial direction of the output member, the circumferential length of a radially outer portion of the plane is longer than the circumferential length of a radially inner portion of the plane.

3. The power transmission device according to claim 2 , wherein the circumferential length of the plane gradually increases from the radially inner side toward the radially outer side.

4. the main body portion has a flat surface formed between adjacent protrusions, the planes include a first plane and a second plane, The power transmission device according to claim 1 , wherein a length in the circumferential direction of the radially outer portion of the second plane is longer than a length in the circumferential direction of the radially outer portion of the first plane.

5. The power transmission device according to claim 4 , wherein a length in the circumferential direction of the radially inner portion of the first plane is longer than a length in the circumferential direction of the radially inner portion of the second plane.

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