Clutch device and motorcycle

A clutch device includes a pressure plate movable toward or away from a clutch center, rotatable relative to the clutch center, and operable to press input-side rotating plates and output-side rotating plates. The clutch center includes an oil passage, at least a portion of which is located in an inner peripheral surface of an outer peripheral wall to guide clutch oil to a center-side fitting portion. The pressure plate includes a pressure-side recess on an outer peripheral surface of a pressure-side fitting portion, recessed radially inward from the outer peripheral surface over the entire outer peripheral surface in movement directions, and continuous with the pressure-side cam hole when seen in movement directions. The pressure-side recess communicates with the oil passage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2022-141609 filed on Sep. 6, 2022. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a clutch device and a motorcycle. More particularly, the present disclosure relates to a clutch device that arbitrarily allows or interrupts transfer of a rotation driving force of an input shaft that is rotationally driven by a prime mover such as an engine to an output shaft, and also relates to a motorcycle including the clutch device.

2. Description of the Related Art

Conventional vehicles such as motorcycles include clutch devices. A clutch device is disposed between an engine and a drive wheel and allows or interrupts transfer of a rotation driving force of the engine to the drive wheel. The clutch device generally includes a plurality of input-side rotating plates that rotate by a rotation driving force of an engine and a plurality of output-side rotating plates connected to an output shaft that transfers the rotation driving force to a drive wheel. The input-side rotating plates and the output-side rotating plates are alternately arranged in a stacking direction, and the input-side rotating plates and the output-side rotating plates are brought into pressure contact with each other and are separated from each other so that transfer of a rotation driving force is allowed or interrupted.

Japanese Patent No. 5847551, for example, discloses a clutch device including a clutch center (clutch member) that holds output-side rotating plates (driven-side clutch plates), and a pressure plate (pressure member) movable toward or away from the clutch center. The pressure plate is configured to press the input-side rotating plates and the output-side rotating plates. In this manner, the clutch device employs an assembly of the clutch center and the pressure plate.

Clutch oil that has flowed from the output shaft is distributed in the clutch center. A portion of the clutch oil is distributed to the outside from the clutch center through a gap between a center-side fitting portion of the clutch center and a pressure-side fitting portion of the pressure plate slidably fitted in the center-side fitting portion, and is supplied to the input-side rotating plates and the output-side rotating plates. Thus, it is desired that clutch oil is efficiently discharged to the outside of the clutch center through a gap between the center-side fitting portion and the pressure-side fitting portion and supplied to the input-side rotating plates and the output-side rotating plates.

SUMMARY OF THE INVENTION

Preferred embodiments of the present disclosure provide clutch devices each capable of efficiently discharging clutch oil to the outside of a clutch center through a gap between a center-side fitting portion and a pressure-side fitting portion to supply clutch oil to input-side rotating plates and output-side rotating plates, and motorcycles including such clutch devices.

A clutch device according to a preferred embodiment of the present disclosure is a clutch device that allows or interrupts transfer of a rotation driving force of an input shaft, and includes a clutch center housed in a clutch housing holding a plurality of input-side rotating plates to be rotationally driven by rotational driving of the input shaft, the clutch center holding a plurality of output-side rotating plates and being operable to be rotationally driven together with the output shaft, the input-side rotating plates and the output-side rotating plates being alternately arranged, and a pressure plate movable toward or away from the clutch center and rotatable relative to the clutch center, the pressure plate being operable to press the input-side rotating plates and the output-side rotating plates. The clutch center includes an output shaft holding portion to which the output shaft is coupled, an outer peripheral wall located radially outward of the output shaft holding portion, a center-side fitting portion located on an inner peripheral surface of the outer peripheral wall, and an oil passage at least a portion of which is located in the inner peripheral surface of the outer peripheral wall to guide clutch oil to the center-side fitting portion. The pressure plate includes a plurality of pressure-side cam portions each including at least one of a pressure-side assist cam surface or a pressure-side slipper cam surface, the pressure-side assist cam surface being operable to generate a force in a direction from the pressure plate toward the clutch center in order to increase a pressing force between the input-side rotating plates and the output-side rotating plates upon rotation relative to the clutch center, the pressure-side slipper cam surface being operable to cause the pressure plate to move away from the clutch center in order to reduce the pressing force between the input-side rotating plates and the output-side rotating plates upon rotation relative to the clutch center, a pressure-side cam hole penetrating a portion between adjacent ones of the pressure-side cam portions, a pressure-side fitting portion located radially outward of the pressure-side cam portions and slidably fitting in the center-side fitting portion, and a pressure-side recess located on an outer peripheral surface of the pressure-side fitting portion, recessed radially inward from the outer peripheral surface over the entire outer peripheral surface in movement directions, and being continuous with the pressure-side cam hole when seen in the movement directions, assuming directions in which the pressure plate moves toward and away from the clutch center are the movement directions. The pressure-side recess communicates with the oil passage.

In a clutch device according to a preferred embodiment of the present disclosure, the pressure-side recess communicates with the oil passage. Accordingly, clutch oil flowing in the oil passage also flows in the pressure-side recess. The pressure-side recess is recessed radially inward from the outer peripheral surface of the pressure-side fitting portion over the entire outer peripheral surface in the movement directions. Thus, a larger amount of clutch oil is discharged to the outside of the clutch center through the pressure-side recess. That is, a larger amount of clutch oil is supplied to the input-side rotating plates and the output-side rotating plates. In addition, since the pressure-side recess is continuous with the pressure-side cam hole when seen in the movement directions, when clutch oil flows from the outside of the clutch center into the clutch center through the pressure-side cam hole, for example, the clutch oil that has flowed in the clutch center is held in the pressure-side recess. Accordingly, clutch oil can be supplied from the pressure-side recess to the input-side rotating plates and the output-side rotating plates.

Preferred embodiments of the present invention provide clutch devices each capable of efficiently discharging clutch oil to the outside of a clutch center through a gap between a center-side fitting portion and a pressure-side fitting portion to supply clutch oil to input-side rotating plates and output-side rotating plates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Clutch devices according to preferred embodiments of the present disclosure will be described hereinafter with reference to the drawings. The preferred embodiments described herein are, of course, not intended to particularly limit the present disclosure. Elements and features having the same functions are denoted by the same reference characters, and description for the same elements and features will not be repeated or will be simplified as appropriate.

First Preferred Embodiment

FIG.1is a cross-sectional view of a clutch device10according to this preferred embodiment. The clutch device10is provided in a vehicle such as a motorcycle, for example. The clutch device10allows or interrupts transfer of a rotation driving force of an input shaft (crankshaft) of an engine of the motorcycle to an output shaft15, for example. The clutch device10allows or interrupts transfer of a rotation driving force of the input shaft to a drive wheel (rear wheel) through the output shaft15. The clutch device10is disposed between the engine and a transmission.

In the following description, directions in which a pressure plate70of the clutch device10and the clutch center40are arranged will be referred to as directions D, a direction in which the pressure plate70moves toward the clutch center40will be referred to as a first direction D1, and a direction in which the pressure plate70moves away from the clutch center40will be referred to as a second direction D2. The directions D are examples of movement directions. Circumferential directions of the clutch center40and the pressure plate70will be referred to as circumferential directions S, one of the circumferential direction S from one pressure-side cam portion90to another pressure-side cam portion90will be referred to as a first circumferential direction S1(seeFIG.5), and one of the circumferential direction S from the other pressure-side cam portion90to the one pressure-side cam portion90will be referred to as a second circumferential direction S2(seeFIG.5). In this preferred embodiment, axial directions of the output shaft15, axial directions of a clutch housing30, axial directions of the clutch center40, and axial directions of the pressure plate70are the same as the directions D. The pressure plate70and the clutch center40rotate in the first circumferential direction S1. It should be noted that the directions described above are defined simply for convenience of description, and are not intended to limit the state of installation of the clutch device10and do not limit the present disclosure.

As illustrated inFIG.1, the clutch device10includes the output shaft15, input-side rotating plates20, output-side rotating plates22, the clutch housing30, the clutch center40, the pressure plate70, and a stopper plate100.

As illustrated inFIG.1, the output shaft15is a hollow shaft. One end of the output shaft15rotatably supports an input gear35described later and the clutch housing30through a needle bearing15A. The output shaft15fixedly supports a clutch center40through a nut15B. That is, the output shaft15rotates together with the clutch center40. The other end of the output shaft15is coupled to a transmission (not shown) of an automobile, for example.

As illustrated inFIG.1, the output shaft15includes, in a hollow portion15H thereof, a push rod16A and a push member16B adjacent to the push rod16A. The hollow portion15H defines and functions as a channel of clutch oil. Clutch oil flows in the output shaft15, that is, in the hollow portion15H. The push rod16A and the push member16B are slidable in the hollow portion15H of the output shaft15. The push rod16A has one end (left end in the drawing) coupled to a clutch operation lever (not shown) of the motorcycle, and slides in the hollow portion15H by operation of the clutch operation lever and presses the clutch push member16B in the second direction D2. A portion of the push member16B projects outward of the output shaft15(in the second direction D2in this preferred embodiment) and is coupled to a release bearing18provided on the pressure plate70. The push rod16A and the push member16B are thinner than the inner diameter of the hollow portion15H so that flowability of clutch oil is obtained in the hollow portion15H.

The clutch housing30is preferably made of an aluminum alloy, for example. The clutch housing30has a bottomed cylindrical shape. As illustrated inFIG.1, the clutch housing30includes a bottom wall31having a substantially circular shape, and a side wall33extending from an edge of the bottom wall31in the second direction D2. The clutch housing30holds the plurality of input-side rotating plates20.

As illustrated inFIG.1, an input gear35is disposed on the bottom wall31of the clutch housing30. The input gear35is fixed to the bottom wall31by a rivet35B through a torque damper35A. The input gear35meshes with a driving gear (not shown) that rotates by rotational driving of the input shaft of the engine. The input gear35is rotationally driven together with the clutch housing30, independently of the output shaft15.

The input-side rotating plates20is rotationally driven by rotational driving of the input shaft. As illustrated inFIG.1, the input-side rotating plates20are held on the inner peripheral surface of the side wall33of the clutch housing30. The input-side rotating plates20are held in the clutch housing30by spline fitting. The input-side rotating plates20are displaceable along the axial direction of the clutch housing30. The input-side rotating plates20are rotatable together with the clutch housing30.

The input-side rotating plates20are pushed against the output-side rotating plates22. The input-side rotating plates20are ring-shaped flat plates. Each of the input-side rotating plates20is shaped by punching a thin plate of a steel plate cold commercial (SPCC) material into a ring shape. Friction members (not shown) of a plurality of paper sheets are attached to the front and back surfaces of the input-side rotating plates20. A groove with a depth of several micrometers to several tens of micrometers is formed between the friction members to hold clutch oil.

As illustrated inFIG.1, the clutch center40is housed in the clutch housing30. The clutch center40and the clutch housing30are concentrically disposed. The clutch center40includes a cylindrical body42and a flange68extending radially outward from the outer edge of the body42. The clutch center40holds the plurality of output-side rotating plates22arranged alternately with the input-side rotating plates20in the directions D. The clutch center40is rotationally driven together with the output shaft15.

As illustrated inFIG.2, the body42includes a ring-shaped base wall43, an outer peripheral wall45located radially outward of the base wall43and extending in the second direction D2, an output shaft holding portion50disposed at the center of the base wall43, a plurality of center-side cam portions60connected to the base wall43and the outer peripheral wall45, and a center-side fitting portion58.

The output shaft holding portion50has a cylindrical shape. The output shaft holding portion50has an insertion hole51in which the output shaft15is inserted and spline-fitted. The insertion hole51penetrates the base wall43. An inner peripheral surface50A of the output shaft holding portion50defining the insertion hole51includes a plurality of spline grooves formed along the axial direction. The output shaft15is coupled to the output shaft holding portion50.

As illustrated inFIG.2, the outer peripheral wall45of the clutch center40is disposed radially outward of the output shaft holding portion50. An outer peripheral surface45A of the outer peripheral wall45includes a spline fitting portion46. The spline fitting portion46includes a plurality of center-side fitting teeth47extending in the axial directions of the clutch center40along the outer peripheral surface45A of the outer peripheral wall45, a plurality of spline grooves48each formed between adjacent ones of the center-side fitting teeth47and extending in the axial directions of the clutch center40, and oil flow holes49. The center-side fitting teeth47hold the input-side rotating plates20and the output-side rotating plates22. The plurality of center-side fitting teeth47are arranged in the circumferential directions S. The plurality of center-side fitting teeth47are arranged at regular or substantially regular intervals in the circumferential directions S. The plurality of center-side fitting teeth47have the same or substantially the same shape. The center-side fitting teeth47project radially outward from the outer peripheral surface45A of the outer peripheral wall45. The number of the center-side fitting teeth47is preferably a multiple of the number of the center-side cam portions60. In this preferred embodiment, the number of the center-side cam portions60is three, and the number of the center-side fitting teeth47is 30, which will be described later. The number of the center-side fitting teeth47may not be a multiple of the number of the center-side cam portions60. The oil flow holes49penetrate the outer peripheral wall45along the radial directions. Each of the oil flow holes49is formed between adjacent ones of the center-side fitting teeth47. That is, the oil flow holes49are formed in the spline grooves48. The oil flow holes49are formed at the sides of the center-side cam portions60. More specifically, the discharge holes49are formed at the sides of the center-side slipper cam surfaces60S of the center-side cam portions60. The oil flow holes49are formed ahead of the center-side slipper cam surface60S in the first circumferential direction S1. The oil flow holes49are formed ahead of bosses54described later in the second circumferential direction S2. The oil flow holes49are formed in an oil passage41described later. More specifically, the oil flow holes49are formed in a second center-side recess41HB of center-side recesses41H described later. In this preferred embodiment, three oil flow holes49are formed in each of three portions of the outer peripheral wall45in the circumferential directions S. The oil flow holes49are arranged at regular or substantially regular intervals in the circumferential directions S. The oil flow holes49cause the inside and outside of the clutch center40to communicate with each other. The oil flow holes49allow clutch oil that has flowed from the output shaft15into the clutch center40to be discharged to the outside of the clutch center40. In this preferred embodiment, the oil flow holes49allow clutch oil flowing at an inner peripheral surface45B of the outer peripheral wall45to be discharged to the outside of the clutch center40.

The output-side rotating plates22are held by the spline fitting portion46of the clutch center40and the pressure plate70. A portion of the output-side rotating plates22is held by the center-side fitting teeth47of the clutch center40and the spline grooves48by spline fitting. Another portion of the output-side rotating plates22is held by a pressure-side fitting teeth77(seeFIG.4) described later of the pressure plate70. The output-side rotating plates22are displaceable along the axial directions of the clutch center40. The output-side rotating plates22are rotatable together with the clutch center40.

The output-side rotating plates22are pushed against the input-side rotating plates20. The output-side rotating plates22are ring-shaped flat plates. Each of the output-side rotating plates22is shaped by punching a thin plate of an SPCC material into a ring shape. The front and back surfaces of the output-side rotating plates22have grooves with depths of several micrometers to several tens of micrometers, for example, to hold clutch oil. The front and back surfaces of the output-side rotating plates22are subjected to a surface hardening treatment to enhance abrasion resistance. The friction members provided on the input-side rotating plates20may be provided on the output-side rotating plates22instead of the input-side rotating plates20, or may be provided on both the input-side rotating plates20and the output-side rotating plates22.

Each of the center-side cam portions60has a trapezoidal shape including a cam surface including a slope defining an assist & slipper (registered trademark) mechanism that generates an assist torque as a force of increasing a pressing force (contact pressure force) between the input-side rotating plates20and the output-side rotating plates22or a slipper torque as a force of separating the input-side rotating plates20and the output-side rotating plates22from each other early and shifting these plates into a half-clutch state. The center-side cam portions60project from the base wall43in the second direction D2. As illustrated inFIG.3, the center-side cam portions60are arranged at regular or substantially regular intervals in the circumferential directions S of the clutch center40. In this preferred embodiment, the clutch center40includes three center-side cam portions60, but the number of the center-side cam portions60is not limited to three.

As illustrated inFIG.3, the center-side cam portions60are located radially outward of the output shaft holding portion50. Each of the center-side cam portions60includes the center-side assist cam surface60A and the center-side slipper cam surface60S. The center-side assist cam surface60A is configured to generate a force in a direction from the pressure plate70toward the clutch center40in order to increase a pressing force (contact pressure force) between the input-side rotating plates20and the output-side rotating plates22in relative rotation to the pressure plate70. In this preferred embodiment, when this force is generated, the position of the pressure plate70to the clutch center40does not change, and the pressure plate70does not need to approach the clutch center40physically. The pressure plate70may be physically displaced with respect to the clutch center40. The center-side slipper cam surface60S is configured to separate the pressure plate70from the clutch center40in order to reduce the pressing force (contact pressure force) between the input-side rotating plates20and the output-side rotating plates22in relative rotation to the pressure plate70. In the center-side cam portions60adjacent to each other in the circumferential directions S, the center-side assist cam surface60A of one center-side cam portion60L and the center-side slipper cam surface60S of the other center-side cam portion60M are opposed to each other in the circumferential directions S.

As illustrated inFIG.2, the clutch center40includes the plurality of (for example, three in this preferred embodiment) bosses54. The bosses54support the pressure plate70. The plurality of bosses54are arranged at regular or substantially regular intervals in the circumferential directions S. Each of the bosses54has a cylindrical shape. The bosses54are located radially outward of the output shaft holding portion50. The bosses54extend toward the pressure plate70(i.e., in the second direction D2). The bosses54are disposed on the base wall43. The bosses54have screw holes54H in which bolts28(seeFIG.1) are inserted. The screw holes54H extend in the axial directions of the clutch center40.

As illustrated inFIGS.2and3, the clutch center40includes center-side cam holes43H penetrating a portion of the base wall43. The center-side cam holes43H penetrate the base wall43in the directions D. The center-side cam holes43H extend from portions on the side of the output shaft holding portion50to the outer peripheral wall45. Each of the center-side cam holes43H is formed between the center-side assist cam surface60A of the center-side cam portion60and the boss54. When seen in the axial direction of the clutch center40, the center-side assist cam surface60A overlaps with a portion of the center-side cam hole43H.

As illustrated inFIGS.2and3, the clutch center40includes through holes43P penetrating a portion of the base wall43. The through holes43P penetrate the base wall43in the directions D. Each of the through hole43P is formed between the center-side slipper cam surface60S of the center-side cam portion60and the center-side cam hole43H. The through hole43P is located ahead of the center-side slipper cam surface60S in the first circumferential direction S1. The through hole43P is located ahead of the boss54in the second circumferential direction S2. The oil flow holes49are formed radially outward of the through holes43P. The through holes43P are smaller than the center-side cam holes43H. The through holes43P causes the inside and outside of the clutch center40to communicate with each other. The through holes43P are configured to guide clutch oil flowing outside the clutch center40to the inside of the clutch center40. More specifically, as indicated by arrow FS inFIG.1, clutch oil that has flowed out from the output shaft15toward the clutch center40flows into the clutch center40through the through holes43P.

As illustrated inFIG.2, the center-side fitting portion58is located radially outward of the output shaft holding portion50. The center-side fitting portion58is located radially outward of the center-side cam portions60. The center-side fitting portion58is disposed ahead of the center-side cam portions60in the second direction D2. The center-side fitting portion58is formed on the inner peripheral surface of the outer peripheral wall45. The center-side fitting portion58is slidably fitted onto a pressure-side fitting portion88(seeFIG.4) described later. The inner diameter of the center-side fitting portion58has a fitting tolerance allowing distribution of clutch oil flowing out of a distal end15T of the output shaft15to the pressure-side fitting portion88. That is, a gap is formed between the center-side fitting portion58and the pressure-side fitting portion88described later. In this preferred embodiment, for example, the center-side fitting portion58has an inner diameter larger than the outer diameter of the pressure-side fitting portion88by about 0.1 mm. This dimensional tolerance between the inner diameter of the center-side fitting portion58and the outer diameter of the pressure-side fitting portion88is appropriately set in accordance with the amount of clutch oil intended to be distributed, and is, for example, about 0.1 mm or more and about 0.5 mm or less.

As illustrated inFIG.2, the clutch center40includes the oil passage41that guides clutch oil to the center-side fitting portion58. At least a portion of the oil passage41is formed in the inner peripheral surface45B of the outer peripheral wall45. The oil passage41includes the center-side recesses41H recessed radially outward from the inner peripheral surface45B of the outer peripheral wall45. The center-side recesses41H include a first center-side recess41HA located at a side of the center-side assist cam surface60A in the circumferential directions S, and the second center-side recess41HB located at a side of the center-side slipper cam surface60S in the circumferential directions S.

As illustrated inFIG.2, the first center-side recess41HA guides clutch oil to the center-side fitting portion58. The first center-side recess41HA is located ahead of the center-side assist cam surface60A in the second circumferential direction S2. The first center-side recess41HA is located ahead of the boss54in the first circumferential direction S1. The first center-side recess41HA is located radially outward of the center-side cam hole43H. The first center-side recess41HA is continuous with the center-side cam hole43H. The first center-side recess41HA is formed in a portion of the inner peripheral surface45B of the outer peripheral wall45in the directions D. The second center-side recess41HB guides clutch oil to the center-side fitting portion58. The second center-side recess41HB is located ahead of the center-side slipper cam surface60S in the first circumferential direction S1.

As illustrated inFIG.2, the second center-side recess41HB is located ahead of the boss54in the second circumferential direction S2. The second center-side recess41HB is located radially outward of the through hole43P. The second center-side recess41HB is continuous with the through hole43P. The second center-side recess41HB is formed in the entire inner peripheral surface45B of the outer peripheral wall45in the directions D. A length L3of the first center-side recess41HA in the circumferential directions S (seeFIG.11) is longer than a length L4of the second center-side recess41HB in the circumferential directions S (seeFIG.12). A length of the first center-side recess41HA in the directions D is smaller than a length of the second center-side recess41HB in the directions D.

As illustrated inFIG.1, the pressure plate70is movable toward or away from the clutch center40and rotatable relative to the clutch center40. The pressure plate70is configured to press the input-side rotating plates20and the output-side rotating plates22. The pressure plate70is disposed coaxially with the clutch center40and the clutch housing30. The pressure plate70includes a body72, and a flange98connected to the outer edge of the body72on the side of the second direction D2and extending radially outward. The body72projects ahead of the flange98in the first direction D1. The pressure plate70holds the plurality of output-side rotating plates22arranged alternately with the input-side rotating plates20.

As illustrated inFIG.4, the body72includes the cylindrical portion80, the plurality of pressure-side cam portions90, the pressure-side fitting portion88, and a spring housing portion84(see alsoFIG.6).

As illustrated inFIG.4, the flange98extends radially outward from the outer edge of the pressure-side fitting portion88. The flange98includes a pressing surface98A that applies a pressing force to the input-side rotating plates20and the output-side rotating plates22and a connection surface98B located radially inward of the pressing surface98A. The connection surface98B includes pressure-side fitting teeth77described later. The connection surface98B is connected to the pressure-side fitting portion88. The pressing surface98A and the connection surface98B are disposed substantially in parallel to each other. The pressing surface98A is located ahead of the connection surface98B in the second direction D2.

The cylindrical portion80has a cylindrical shape. The cylindrical portion80is integrally formed with the pressure-side cam portions90. The cylindrical portion80houses the distal end15T of the output shaft15(seeFIG.1). The cylindrical portion80houses the release bearing18(seeFIG.1). The cylindrical portion80receives a pressing force from the push member16B. The cylindrical portion80receives clutch oil that has flowed out from the distal end15T of the output shaft15.

Each of the pressure-side cam portions90has a trapezoidal shape including a cam surface including a slope defining an assist & slipper (registered trademark) mechanism that slides on the center-side cam portions60and generates an assist torque or a slipper torque. The pressure-side cam portions90project from the flange98in the first direction D1. As illustrated inFIG.5, the pressure-side cam portions90are arranged at regular or substantially regular intervals in the circumferential directions S of the pressure plate70. In this preferred embodiment, the pressure plate70includes three pressure-side cam portions90, but the number of the pressure-side cam portions90is not limited to three.

As illustrated inFIG.5, the pressure-side cam portion90is located radially outward of the cylindrical portion80. Each of the pressure-side cam portions90includes a pressure-side assist cam surface90A (see alsoFIG.7) and a pressure-side slipper cam surface90S. The pressure-side assist cam surface90A can be brought into contact with the center-side assist cam surface60A. The pressure-side assist cam surface90A is configured to generate a force in a direction from the pressure plate70toward the clutch center40in order to increase a pressing force (contact pressure force) between the input-side rotating plates20and the output-side rotating plates22in relative rotation to the clutch center40. The pressure-side slipper cam surface90S can be brought into contact with the center-side slipper cam surface60S. The pressure-side slipper cam surface90S is configured to separate the pressure plate70from the clutch center40in order to reduce a pressing force (contact pressure force) between the input-side rotating plates20and the output-side rotating plates22in relative rotation to the clutch center40. In the pressure-side cam portions90adjacent to each other in the circumferential directions S, the pressure-side assist cam surface90A of one pressure-side cam portion90L and the pressure-side slipper cam surface90S of the other pressure-side cam portion90M are opposed to each other in the circumferential directions S.

As illustrated inFIG.8, an end of the pressure-side assist cam surface90A of each pressure-side cam portion90in the circumferential directions S includes a chamfered portion90AP that is linearly chamfered. A corner of the chamfered portion90AP (corner on the side of the first direction D1and the first circumferential direction S1) includes a right angle. More specifically, the chamfered portion90AP is formed in an end90AB of the pressure-side assist cam surface90A in the first circumferential direction S1.

Advantages of the center-side cam portions60and the pressure-side cam portions90will now be described. When the rotation speed of the engine increases so that a rotation driving force input to the input gear35and the clutch housing30is thereby allowed to be transferred to the output shaft15through the clutch center40, a rotation force in the first circumferential direction S1is applied to the pressure plate70, as illustrated inFIG.10A. Thus, with the effects of the center-side assist cam surface60A and the pressure-side assist cam surface90A, a force in first direction D1is generated in the pressure plate70. Accordingly, a contact pressure force between the input-side rotating plates20and the output-side rotating plates22increases.

On the other hand, when the rotation speed of the output shaft15exceeds the rotation speed of the input gear35and the clutch housing30and a back torque is generated, a rotation force in the first circumferential direction S1is applied to the clutch center40, as illustrated inFIG.10B. Thus, with the effects of the center-side slipper cam surface60S and the pressure-side slipper cam surface90S, the pressure plate70moves in the second direction D2and releases a contact pressure force between the input-side rotating plates20and the output-side rotating plates22. In this manner, it is possible to avoid problems in the engine and the transmission caused by the back torque.

As illustrated inFIGS.4and5, the pressure plate70has pressure-side cam holes73H penetrating the body72and a portion of the flange98. The pressure-side cam holes73H are located radially outward of the cylindrical portion80. The pressure-side cam holes73H extend from portions on the side of the cylindrical portion80to the radially outside of the pressure-side fitting portion88. Each of the pressure-side cam holes73H is formed between adjacent ones of the pressure-side cam portions90. Each of the pressure-side cam holes73H is formed between the pressure-side assist cam surface90A and the pressure-side slipper cam surface90S of adjacent ones of the pressure-side cam portions90. As illustrated inFIGS.5and7, when seen in the axial direction of the pressure plate70, the pressure-side assist cam surface90A overlaps with portions of the pressure-side cam holes73H.

As illustrated inFIGS.6and7, the spring housing portions84are formed in the pressure-side cam portions90. The spring housing portions84are recessed from the second direction D2in the first direction D1. Each of the spring housing portions84has an oval shape. The spring housing portions84house pressure springs25(seeFIG.1). The spring housing portions84include insertion holes84H which penetrate the spring housing portions84and in which the bosses54(seeFIG.2) are inserted. That is, the insertion holes84H penetrate the pressure-side cam portions90. Each of the insertion holes84H has an oval shape.

As illustrated inFIG.1, the pressure springs25are housed in the spring housing portions84. The pressure springs25are held by the bosses54inserted in the insertion holes84H of the spring housing portions84. The pressure springs25bias the pressure plate70toward the clutch center40(i.e., in the first direction D1). The pressure springs25are, for example, coil springs obtained by radially winding spring stee.

As illustrated inFIG.4, the pressure-side fitting portion88is located radially outside of the pressure-side cam portions90. The pressure-side fitting portion88is located ahead of the pressure-side cam portions90in the second direction D2. The pressure-side fitting portion88is configured to slidably fit in the center-side fitting portion58(seeFIG.2).

As illustrated inFIGS.4and5, the pressure plate70includes pressure-side recesses71. The pressure-side recesses71are formed in an outer peripheral surface88A of the pressure-side fitting portion88. The pressure-side recesses71are recessed radially inward from the outer peripheral surface88A over the entire outer peripheral surface88A in the directions D. A depth M1of each pressure-side recess71in the radial directions is deeper than a depth M2of each center-side recess41H in the radial directions (seeFIG.4). When seen in the directions D, the pressure-side recesses71are continuous with the pressure-side cam holes73H. The pressure-side recesses71include a first pressure-side recess71A and a second pressure-side recess71B.

As illustrated inFIG.5, the first pressure-side recess71A is located closer to the pressure-side assist cam surface90A than a center90C of the pressure-side cam portion90in the circumferential directions S. The first pressure-side recess71A is located ahead of the pressure-side assist cam surface90A in the second circumferential direction S2. As illustrated inFIG.11, at least a portion of the first pressure-side recess71A overlaps with the oil passage41when seen in the radial directions. In this preferred embodiment, at least a portion of the first pressure-side recess71A overlaps with the first center-side recess41HA when seen in the radial directions. The first pressure-side recess71A communicates with the oil passage41. The first pressure-side recess71A communicates with the first center-side recess41HA. At least a portion of the first pressure-side recess71A faces the first center-side recess41HA. The length L3of the first center-side recess41HA in the circumferential directions S is longer than a length L1of the first pressure-side recess71A in the circumferential directions S. A depth of the first pressure-side recess71A in the radial directions is deeper than a depth of the first center-side recess41HA in the radial directions.

As illustrated inFIG.5, the second pressure-side recess71B is located closer to the pressure-side slipper cam surface90S than the center90C of the pressure-side cam portion90in the circumferential directions S. The second pressure-side recess71B is located radially outward of the pressure-side slipper cam surface90S. A length L2of the second pressure-side recess71B in the circumferential directions S is longer than the length L1of the first pressure-side recess71A in the circumferential directions S. As illustrated inFIG.12, at least a portion of the second pressure-side recess71B overlaps with the oil passage41when seen in the radial directions. In this preferred embodiment, at least a portion of the second pressure-side recess71B overlaps with the second center-side recess41HB when seen in the radial directions. The second pressure-side recess71B communicates with the oil passage41. The second pressure-side recess71B communicates with the second center-side recess41HB. The second pressure-side recess71B overlaps with at least a portion of the oil flow holes49when seen in the radial directions. At least a portion of the second pressure-side recess71B faces the second center-side recess41HB. The length L2of the second pressure-side recess71B in the circumferential directions S is longer than the length L4of the second center-side recess41HB in the circumferential directions S. A depth of the second pressure-side recess71B in the radial directions is deeper than a depth of the second center-side recess41HB in the radial directions.

As illustrated inFIG.4, the pressure plate70includes the plurality of pressure-side fitting teeth77arranged on the flange98. The pressure-side fitting teeth77hold the input-side rotating plates20and the output-side rotating plates22. The pressure-side fitting teeth77are located radially outward of the cylindrical portion80. The pressure-side fitting teeth77are located radially outward of the pressure-side cam portions90. The pressure-side fitting teeth77are located radially outward of the pressure-side fitting portion88. The pressure-side fitting teeth77are formed on the connection surface98B of the flange98. The pressure-side fitting teeth77project in the first direction D1from the connection surface98B. The pressure-side fitting teeth77are arranged in the circumferential directions S. The pressure-side fitting teeth77are arranged at regular or substantially regular intervals in the circumferential directions S. The pressure-side fitting teeth77include oil return fitting teeth77X. The oil return fitting teeth77X have the function of returning a portion of clutch oil flowing from the pressure-side recesses71radially outward to the pressure-side recesses71. The oil return fitting teeth77X are located radially outward of the pressure-side recesses71. That is, when seen in the radial directions, the oil return fitting teeth77X overlap at least a portion of the pressure-side recesses71. As illustrated inFIG.12, when seen in the radial directions, at least a portion of the spline grooves48including the oil flow holes49overlaps with the oil return fitting teeth77X. In this preferred embodiment, since a portion of the pressure-side fitting teeth77has been removed, the interval of this portion is enlarged, but the other adjacent pressure-side fitting teeth77are arranged at regular or substantially regular intervals. That is, as illustrated inFIG.5, the flange98includes a first portion98S in which a distance between adjacent pressure-side fitting teeth77in the circumferential directions S is a first length L5and a second portion98T having a second length L6longer than the first length L5. The second portion98T is located ahead, in the second circumferential direction S2, of an end71T of the pressure-side recess71in the first circumferential direction S1. In this preferred embodiment, the second portion98T is located ahead, in the second circumferential direction S2, of an end71T of the first pressure-side recess71A in the first circumferential direction S1. The second portion98T is located ahead, in the second circumferential direction S2, of the end71T of the second pressure-side recess71B in the first circumferential direction S1.

FIG.9is a plan view illustrating a state where the clutch center40and the pressure plate70are combined. In the state illustrated inFIG.9, the pressure-side assist cam surface90A and the center-side assist cam surface60A do not contact each other, and the pressure-side slipper cam surface90S and the center-side slipper cam surface60S do not contact each other. At this time, the pressure plate70is closest to the clutch center40. In the state illustrated inFIG.9(in the state of assembly), a distance L7in the circumferential directions S between the boss54and an end84HA of the insertion holes84H toward the pressure-side assist cam surface90A (i.e., ahead in the first circumferential direction S1) in the normal state is smaller than a distance L8in the circumferential direction S between the boss54and an end84HB of the insertion holes84H toward the pressure-side slipper cam surface90S (i.e., ahead in the second circumferential direction S2) in the normal state.

As illustrated inFIG.1, the stopper plate100can contact the pressure plate70. The stopper plate100reduces or prevents separation of the pressure plate70from the clutch center40by a predetermined distance or more in the second direction D2. The stopper plate100is fixed to the bosses54of the clutch center40with the bolts28. The pressure plate70is fixed by fastening the bolts28to the bosses54through the stopper plate100with the bosses54and the pressure springs25of the clutch center40disposed in the spring housing portions84. The stopper plate100is substantially triangular in plan view.

When the pressure plate70is brought into contact with the stopper plate100, the pressure-side slipper cam surface90S and the center-side slipper cam surface60S are in contact with each other in an area of about 50% or more and about 90% or less of the area of the pressure-side slipper cam surface90S and about 50% or more and about 90% or less of the area of the center-side slipper cam surface60S, for example. When the pressure plate70is brought into contact with the stopper plate100, the pressure springs25are separated from the side walls of the spring housing portions84. That is, the pressure springs25are not sandwiched between the bosses54and the spring housing portions84, and application of excessive stress to the bosses54is reduced or prevented.

The clutch device10is filled with a predetermined amount of clutch oil. Clutch oil is distributed in the clutch center40and the pressure plate70through the hollow portion15H of the output shaft15, and then is supplied to the input-side rotating plates20and the output-side rotating plates22through the gap between the center-side fitting portion58and the pressure-side fitting portion88(e.g., the center-side recesses41H and the pressure-side recesses71) and the oil flow holes49. Clutch oil is also distributed from the outside of the clutch center40through the hollow portion15H of the output shaft15into the clutch center40through the through hole43P and the pressure-side cam hole73H. Clutch oil reduces or prevents absorption of heat and abrasion of the friction members. The clutch device10according to this preferred embodiment is a so-called multiplate wet friction clutch device.

Operation of the clutch device10according to this preferred embodiment will now be described. As described above, the clutch device10is disposed between the engine and the transmission of the motorcycle, and allows or interrupts transfer of a rotation driving force of the engine to the transmission by driver's operation of a clutch operation lever.

In the clutch device10, in a case where the driver of the motorcycle does not operate the clutch operation lever, a clutch release mechanism (not shown) does not press the push rod16A, and thus, the pressure plate70presses the input-side rotating plates20with a biasing force (elastic force) of the pressure springs25. Accordingly, the clutch center40enters a clutch-ON state in which the input-side rotating plates20and the output-side rotating plates22are pushed against each other to be friction coupled, and is rotationally driven. That is, a rotation driving force of the engine is transferred to the clutch center40, and the output shaft15is rotationally driven.

In the clutch-ON state, clutch oil distributed in the hollow portion15H of the output shaft15and having flowed out from the distal end15T of the output shaft15is dropped or spattered in the cylindrical portion80and attached to the cylindrical portion80(see arrow F inFIG.1). The clutch oil attached to the inside of the cylindrical portion80is guided into the clutch center40. Accordingly, clutch oil flows out of the clutch center40through the oil flow holes49. Clutch oil also flows out of the clutch center40through the gap between the center-side fitting portion58and the pressure-side fitting portion88(e.g., the center-side recesses41H and the pressure-side recesses71). Then, clutch oil that has flowed out of the clutch center40is supplied to the input-side rotating plates20and the output-side rotating plates22.

On the other hand, in the clutch device10, when the driver of the motorcycle operates the clutch operation lever in the clutch-ON state, the clutch release mechanism (not shown) presses the push rod16A, and thus, the pressure plate70is displaced in a direction away from the clutch center40(second direction D2) against a biasing force of the pressure springs25. Accordingly, the clutch center40enters a clutch-OFF state in which friction coupling between the input-side rotating plates20and the output-side rotating plates22is canceled, and thus, rotational driving attenuates or stops. That is, a rotation driving force of the engine is interrupted to the clutch center40.

In the clutch-OFF state, clutch oil distributed in the hollow portion15H of the output shaft15and having flowed out of the distal end15T of the output shaft15is guided into the clutch center40in the same or substantially the same manner as in the clutch-ON state. At this time, since the pressure plate70is separated from the clutch center40, the amount of fitting between the pressure plate70and each of the center-side fitting portion58and the pressure-side fitting portion88decreases. As a result, clutch oil in the cylindrical portion80actively flows out of the clutch center40, and is distributed to portions in the clutch device10. In particular, clutch oil can be actively guided to gaps between the input-side rotating plates20and the output-side rotating plates22separated from each other.

Then, when the driver cancels the clutch operation lever in the clutch-OFF state, pressing of the pressure plate70by the clutch release mechanism (not shown) through the push member16B is canceled, and thus, the pressure plate70is displaced with a biasing force of the pressure springs25to a direction (first direction D1) of approaching the clutch center40.

As described above, in the clutch device10according to this preferred embodiment, the pressure-side recesses71communicate with the oil passage41. Thus, clutch oil flowing in the oil passage41also flows in the pressure-side recesses71. The pressure-side recesses71are recessed radially inward from the outer peripheral surface88A of the pressure-side fitting portion88over the entire outer peripheral surface88A in the directions D. Thus, a larger amount of clutch oil can be discharged to the outside of the clutch center40through the pressure-side recesses71. That is, a larger amount of clutch oil can be supplied to the input-side rotating plates20and the output-side rotating plates22. In addition, since the pressure-side recesses71are continuous with the pressure-side cam holes73H when seen in the directions D, when clutch oil flows from the outside of the clutch center40into the clutch center40through the pressure-side cam holes73H, for example, the clutch oil that has flowed in the clutch center40is held in the pressure-side recesses71. Accordingly, clutch oil can be supplied from the pressure-side recesses71to the input-side rotating plates20and the output-side rotating plates22.

In the clutch device10according to this preferred embodiment, each of the pressure-side cam portions90includes the pressure-side assist cam surface90A and the pressure-side slipper cam surface90S, the pressure-side assist cam surface90A and the pressure-side slipper cam surface90S are arranged in the circumferential directions S, and the pressure-side recesses71includes the first pressure-side recess71A located closer to the pressure-side assist cam surface90A than the center90C of the pressure-side cam portion90in the circumferential directions. In this configuration, a larger amount of clutch oil can be supplied to the pressure-side assist cam surface90A through the first pressure-side recess71A.

In the clutch device10according to this preferred embodiment, the pressure-side recesses71include the second pressure-side recess71B located closer to the pressure-side slipper cam surface90S than the center90C of the pressure-side cam portion90in the circumferential directions S. In this configuration, a larger amount of clutch oil can be supplied to the pressure-side slipper cam surface90S through the second pressure-side recess71B.

In the clutch device10according to this preferred embodiment, the length L2of the second pressure-side recess71B in the circumferential directions S is longer than the length L1of the first pressure-side recess71A in the circumferential directions S. In this configuration, a larger amount of clutch oil can be supplied to the input-side rotating plates20and the output-side rotating plates22from the second pressure-side recess71B with rigidity around the pressure-side assist cam surface90A of the pressure-side cam portion90maintained.

In the clutch device10according to this preferred embodiment, the clutch center40includes the plurality of center-side cam portions60each including the center-side assist cam surface60A operable to generate a force in a direction from the pressure plate70toward the clutch center40in order to increase a pressing force between the input-side rotating plates20and the output-side rotating plates22upon rotation relative to the pressure plate70, the oil passage41includes the center-side recess41H recessed radially outward from the inner peripheral surface45B of the outer peripheral wall45, the center-side recesses41H include the first center-side recess41HA located at the side of the center-side assist cam surface60A in the circumferential directions S, and the length L3of the first center-side recess41HA in the circumferential directions S is longer than the length L1of the first pressure-side recess71A in the circumferential directions S. In this configuration, a larger amount of clutch oil can be guided to the first center-side recess41HA.

In the clutch device10according to this preferred embodiment, the clutch center40includes the plurality of center-side cam portions60each including the center-side slipper cam surface60S operable to cause the pressure plate70to move away from the clutch center40in order to reduce the pressing force between the input-side rotating plates20and the output-side rotating plates22upon rotation relative to the pressure plate70, the oil passage41includes the center-side recesses41H recessed radially outward from the inner peripheral surface45B of the outer peripheral wall45, the center-side recesses41H include the second center-side recess41HB located at the side of the center-side slipper cam surface60S in the circumferential directions S, and the length L2of the second pressure-side recess71B in the circumferential directions S is longer than the length L4of the second center-side recess41HB in the circumferential directions S. In this configuration, clutch oil can be supplied to the input-side rotating plates20and the output-side rotating plates22from a wider range of the second pressure-side recess71B in the circumferential directions S.

In the clutch device10according to this preferred embodiment, the oil passage41includes the center-side recess41H recessed radially outward from the inner peripheral surface45B of the outer peripheral wall45, and the depth M1of each pressure-side recess71in the radial directions is deeper than the depth M2of each center-side recess41H in the radial directions. In this configuration, a larger amount of clutch oil can be held in the pressure-side recesses71so that a larger amount of clutch oil can be supplied from the pressure-side recesses71to the input-side rotating plates20and the output-side rotating plates22.

In the clutch device10according to this preferred embodiment, the pressure plate70includes the flange98extending radially outward from the outer edge of the pressure-side fitting portion88, and the plurality of pressure-side fitting teeth77located on the flange98, holding the input-side rotating plates20and the output-side rotating plates22, and arranged in the circumferential directions S, the flange98includes the pressing surface98A that applies a pressing force to the input-side rotating plates20and the output-side rotating plates22and the connection surface98B including the pressure-side fitting teeth77, located radially inward of the pressing surface98A, and connected to the pressure-side fitting portion88, and the pressing surface98A and the connection surface98B are disposed substantially in parallel to each other. In this configuration, since clutch oil from the pressure-side recesses71flows on the connection surface98B and the pressing surface98A, clutch oil can be supplied to a wider range of the input-side rotating plates20and the output-side rotating plates22.

In the clutch device10according to this preferred embodiment, the pressure plate70includes the first portion98S in which a distance between adjacent ones of the pressure-side fitting teeth77in the circumferential directions S is the first length L5and the second portion98T having the second length L6longer than the first length L5, and the second portion98T is located ahead, in the second circumferential direction S2, of the end71T of the pressure-side recesses71in the first circumferential direction S1. In this configuration, clutch oil can be supplied from the first portion98S and the second portion98T to the radially outside of the clutch oil in a balanced manner.

In the clutch device10according to this preferred embodiment, the clutch center40includes the plurality of center-side fitting teeth47holding the input-side rotating plates20and the output-side rotating plates22, projecting radially outward from the outer peripheral surface45A of the outer peripheral wall45, and arranged in the circumferential directions S, the plurality of spline grooves48each located between adjacent ones of the center-side fitting teeth47, and the oil flow holes49located in the spline grooves48to penetrate the outer peripheral wall45and operable to discharge clutch oil flowing on the inner peripheral surface45B of the outer peripheral wall45to the outside of the clutch center40, the pressure-side fitting teeth77include the oil return fitting teeth77X located radially outward of the pressure-side recesses71, and the pressure-side recesses71overlap with at least a portion of the oil flow holes49when seen in the radial directions. In this configuration, a portion of clutch oil flowing radially outward from the pressure-side recesses71is caused to return to the pressure-side recesses71by the oil return fitting teeth77X. At least a portion of the clutch oil that has returned is discharged from the oil flow holes49to the outside of the clutch center40. Thus, clutch oil can be effectively supplied to the input-side rotating plates20and the output-side rotating plates22held by the center-side fitting teeth47.

In the clutch device10according to this preferred embodiment, when seen in the radial directions, at least a portion of the spline grooves48including the oil flow holes49overlaps with the oil return fitting teeth77X. In this configuration, clutch oil caused to return to the pressure-side recesses71by the oil return fitting teeth77X more easily flows to the oil flow holes49.

Second Preferred Embodiment

FIG.13is a disassembled perspective view of a clutch center240and a pressure plate270of a clutch device210according to a second preferred embodiment.

The clutch center240is housed in a clutch housing30(seeFIG.1). The clutch center240and the clutch housing30are concentrically disposed. As illustrated inFIG.13, the clutch center240includes a body242, and a flange268connected to an outer edge of the body242on the side of a first direction D1and extending radially outward. The body242projects from the flange268in a second direction D2. The clutch center240does not hold output-side rotating plates22. The clutch center240is rotationally driven together with an output shaft15(seeFIG.1).

As illustrated inFIG.13, the body242includes an output shaft holding portion250, a plurality of center-side cam portions60, and a center-side fitting portion258. The center-side cam portions60project from the flange268in the second direction D2. The center-side cam portions60are located radially outward of the output shaft holding portion250.

The output shaft holding portion250has a cylindrical shape. The output shaft holding portion250has an insertion hole251in which the output shaft15(seeFIG.1) is inserted and spline-fitted. The insertion hole251penetrates the body242. An inner peripheral surface250A of the output shaft holding portion250defining the insertion hole251has a plurality of spline grooves along the axial direction. The output shaft15is coupled to the output shaft holding portion250.

As illustrated inFIG.13, the clutch center240includes a plurality of (for example, three in this preferred embodiment) bosses54. The bosses54are located radially outward of the output shaft holding portion250. The bosses54are disposed on the body242.

As illustrated inFIG.13, the clutch center240includes center-side cam holes243H penetrating the body242and a portion of the flange268. The center-side cam holes243H penetrate the body242and the flange268in directions D. The center-side cam holes243H extend from portions on the side of the output shaft holding portion250to the flange268. The center-side cam holes243H are formed between the center-side assist cam surfaces60A of the center-side cam portions60and the bosses54. When seen in the axial direction of the clutch center240, the center-side assist cam surfaces60A overlap with a portion of the center-side cam holes243H.

As illustrated inFIG.13, the center-side fitting portion258is disposed on the body242. The center-side fitting portion258is located radially outward of the center-side cam portions60. The center-side fitting portion258is located ahead of the center-side cam portions60in the first direction D1. The center-side fitting portion258is configured to slidably fit in the pressure-side fitting portion288(seeFIG.14).

As illustrated inFIG.13, the clutch center240includes a center-side recess241. The center-side recess241is formed on an outer peripheral surface258A of the center-side fitting portion258. The center-side recess241is recessed radially inward from the outer peripheral surface258A over the entire outer peripheral surface258A in the directions D. A depth of the center-side recess241in the radial directions is deeper than a depth of an oil passage271in the radial directions. The center-side recess241is continuous with the center-side cam hole243H when seen in the directions D. The center-side recess241is located closer to the center-side assist cam surface60A than a center of the center-side cam portions60in the circumferential directions S. The center-side recess241is located ahead of the center-side assist cam surface60A in the first circumferential direction S1. At least a portion of the center-side recess241overlaps with the oil passage271when seen in the radial directions. The center-side recess241communicates with the oil passage271.

The pressure plate270is movable toward or away from the clutch center240and rotatable relative to the clutch center240. The pressure plate270is configured to press the input-side rotating plates20and the output-side rotating plates22. The pressure plate270is disposed coaxially with the clutch center240and the clutch housing30. The pressure plate270includes a cylindrical body272, and a flange298extending radially outward from the outer edge of the body272. The pressure plate270holds the plurality of output-side rotating plates22alternately arranged with the input-side rotating plates20in the directions D.

As illustrated inFIG.14, the body272includes a ring-shaped base wall273, an outer peripheral wall275located radially outward of the base wall273and extending in the first direction D1, a cylindrical portion280disposed at the center of the base wall273, a plurality of pressure-side cam portions90connected to the base wall273and the outer peripheral wall275, a pressure-side fitting portion288, and spring housing portions84(seeFIG.13). The pressure-side cam portions90project from the body272in the first direction D1. The pressure-side cam portions90are located radially outward of the cylindrical portion280. The pressure-side cam portions90are located radially inward of the outer peripheral wall275.

The cylindrical portion280has a cylindrical shape. The cylindrical portion280is formed integrally with the pressure-side cam portions90. The cylindrical portion280houses a distal end15T of the output shaft15(seeFIG.1). The cylindrical portion280houses a release bearing18(seeFIG.1). The cylindrical portion280receives a pressing force from a push member16B. The cylindrical portion280receives clutch oil that has flowed out from the distal end15T of the output shaft15.

As illustrated inFIG.14, the outer peripheral wall275of the pressure plate270is located radially outward of the cylindrical portion280. The outer peripheral wall275has a ring shape extending in the directions D. An outer peripheral surface275A of the outer peripheral wall275has a spline fitting portion276. The spline fitting portion276includes a plurality of pressure-side fitting teeth277extending in the axial direction of the pressure plate270along the outer peripheral surface275A of the outer peripheral wall275, a plurality of spline grooves278each formed between adjacent ones of the pressure-side fitting teeth277and extending in the axial direction of the pressure plate270, and oil flow holes279. The pressure-side fitting teeth277hold the output-side rotating plates22. The plurality of pressure-side fitting teeth277are arranged in the circumferential directions S. The plurality of pressure-side fitting teeth277are arranged at regular or substantially regular intervals in the circumferential directions S. The plurality of pressure-side fitting teeth277have the same or substantially the same shape. The pressure-side fitting teeth277project radially outward from the outer peripheral surface275A of the outer peripheral wall275. The oil flow holes279penetrate the outer peripheral wall275in the radial directions. Each of the oil flow holes279is formed between adjacent ones of the pressure-side fitting teeth277. That is, the oil flow holes279are formed in the spline grooves278. The oil flow holes279are formed at the sides of the pressure-side cam portions90. The oil flow holes279are formed at the sides of pressure-side assist cam surfaces90A of the pressure-side cam portions90. The oil flow holes279are located ahead of the pressure-side assist cam surfaces90A in the first circumferential direction S1. The oil flow holes279are located ahead of pressure-side slipper cam surfaces90S in the second circumferential direction S2. The oil flow holes279are formed in an oil passage271described later. In this preferred embodiment, three oil flow holes279are formed in each of three portions of the peripheral wall275in the circumferential directions S. The oil flow holes279are arranged at regular or substantially intervals in the circumferential directions S. The oil flow holes279cause the inside and outside of the pressure plate270to communicate with each other. The oil flow holes279allow clutch oil that has flowed out of the output shaft15into the pressure plate270to be discharged to the outside of the pressure plate270. In this preferred embodiment, the oil flow holes279allow clutch oil flowing at an inner peripheral surface275B of the peripheral wall275to be discharged to the outside of the pressure plate270. At least a portion of the oil flow holes279is located at a position facing the center-side fitting portion258(seeFIG.13).

The output-side rotating plates22are held by the spline fitting portion276of the pressure plate270. The output-side rotating plates22are held by the pressure-side fitting teeth277and the spline grooves278by spline-fitting. The output-side rotating plates22are displaceable along the axial direction of the pressure plate270. The output-side rotating plates22are rotatable together with the pressure plate270.

As illustrated inFIGS.13and14, the pressure plate270includes pressure-side cam holes273H penetrating a portion of the base wall273. The pressure-side cam holes273H penetrate the base wall273in the directions D. The pressure-side cam holes273H are located radially outward of the cylindrical portion80. The pressure-side cam holes273H extend from the sides of the cylindrical portion80to the outer peripheral wall275. Each of the pressure-side cam holes273H penetrates a portion between adjacent ones of the pressure-side cam portions90. Each of the pressure-side cam holes273H penetrates a portion between the pressure-side assist cam surface90A and the pressure-side slipper cam surface90S of adjacent ones of the pressure-side cam portions90. When seen in the axial direction of the pressure plate270, the pressure-side assist cam surfaces90A overlap with a portion of the pressure-side cam holes273H. Clutch oil flows into the pressure-side cam holes273H from the outside of the pressure plate270.

As illustrated inFIG.14, the pressure-side fitting portion288is located radially outward of the cylindrical portion280. The pressure-side fitting portion288is located radially outward of the pressure-side cam portions90. The pressure-side fitting portion288is located ahead of the pressure-side cam portions90in the first direction D1. The pressure-side fitting portion288is formed on the inner peripheral surface275B of the peripheral wall275. The pressure-side fitting portion288is configured to slidably fit onto the center-side fitting portion258(seeFIG.13). A gap is formed between the pressure-side fitting portion288and the center-side fitting portion258.

As illustrated inFIG.14, the pressure plate270includes the oil passage271that guides clutch oil to the pressure-side fitting portion288. At least a portion of the oil passage271is formed in the inner peripheral surface275B of the outer peripheral wall275. The oil passage271is recessed radially outward from the inner peripheral surface275B. The oil passage271is formed in a portion of the inner peripheral surface275B in the directions D. The oil passage271is located radially outward of the pressure-side cam holes273H. The oil passage271is continuous with the pressure-side cam holes273H. The oil passage271is located ahead of the pressure-side assist cam surface90A in the first circumferential direction S1. The oil passage271is located ahead of the pressure-side slipper cam surface90S in the second circumferential direction S2.

In the clutch device210according to this preferred embodiment, the center-side recess241communicates with the oil passage271. Thus, clutch oil flowing in the oil passage271also flows in the center-side recess241. The center-side recess241is recessed radially inward from the outer peripheral surface258A of the center-side fitting portion258over the entire outer peripheral surface258A in the directions D. Thus, a larger amount of clutch oil can be discharged to the outside of the pressure plate270through the center-side recess241. That is, a larger amount of clutch oil can be supplied to the input-side rotating plates20and the output-side rotating plates22. In addition, since the center-side recess241is continuous with center-side cam hole243H when seen in the directions D, when clutch oil flows from the outside of the pressure plate270into the pressure plate270through the center-side cam hole243H, the clutch oil that has flowed in the pressure plate270is held in the center-side recess241. Accordingly, clutch oil can be supplied from the center-side recess241to the input-side rotating plates20and the output-side rotating plates22.

The following paragraphs describe other specific aspects of the techniques disclosed herein.

A clutch device to allow or interrupt transfer of a rotation driving force of an input shaft to an output shaft includes a clutch center housed in a clutch housing holding a plurality of input-side rotating plates to be rotationally driven by rotational driving of the input shaft, the clutch center being operable to be rotationally driven together with the output shaft; and a pressure plate movable toward or away from the clutch center and rotatable relative to the clutch center, the pressure plate holding at least one of the input-side rotating plates or output-side rotating plates and being operable to press the input-side rotating plates and the output-side rotating plates, the input-side rotating plates and the output-side rotating plates being alternately arranged. The pressure plate includes an outer peripheral wall including pressure-side fitting teeth holding the output-side rotating plates, a pressure-side fitting portion located on an inner peripheral surface of the outer peripheral wall, and an oil passage at least a portion of which is located in the inner peripheral surface of the outer peripheral wall and which guides clutch oil to the pressure-side fitting portion. The clutch center includes a plurality of center-side cam portions each including at least one of a center-side assist cam surface or a center-side slipper cam surface, the center-side assist cam surface being operable to generate a force in a direction from the pressure plate toward the clutch center in order to increase a pressing force between the input-side rotating plates and the output-side rotating plates upon rotation relative to the pressure plate, the center-side slipper cam surface being operable to cause the pressure plate to move away from the clutch center in order to reduce the pressing force between the input-side rotating plates and the output-side rotating plates upon rotation relative to the clutch center, a center-side cam hole penetrating a portion between adjacent ones of the center-side cam portions, a center-side fitting portion located radially outward of the center-side cam portions and slidably fitting in the center-side fitting portion, and a center-side recess located on an outer peripheral surface of the center-side fitting portion, recessed radially inward from the outer peripheral surface over the entire outer peripheral surface in movement directions, and being continuous with the center-side cam hole when seen in the movement directions, assuming directions in which the pressure plate moves toward and away from the clutch center are the movement directions. The center-side recess communicates with the oil passage.

The foregoing description is directed to the preferred embodiments of the present disclosure. The preferred embodiments described above, however, are merely examples, and the present disclosure can be performed in various modes and through various preferred embodiments.

In the first preferred embodiment described above, the oil flow hole49is formed in the second center-side recess41HB of the center-side recess41H, but the present disclosure is not limited to this example. The oil flow hole49may be formed in the first center-side recess41HA of the center-side recess41H.

In the first and second preferred embodiments described above, each of the center-side cam portions60includes the center-side assist cam surface60A and the center-side slipper cam surface60S, but only needs to include at least one of the center-side assist cam surface60A or the center-side slipper cam surface60S.

In the first and second preferred embodiments described above, each of the pressure-side cam portions90includes the pressure-side assist cam surface90A and the pressure-side slipper cam surface90S, but only needs to include at least one of the pressure-side assist cam surface90A or the pressure-side slipper cam surface90S.

In the second preferred embodiment described above, the clutch center240is configured not to hold the output-side rotating plates22, but the present disclosure is not limited to this example. The clutch center240may include center-side fitting teeth having a configuration similar to that of the pressure-side fitting teeth77of the first preferred embodiment capable of holding the output-side rotating plates22.

In the second preferred embodiment described above, the center-side recess241is located closer to the center-side assist cam surface60A than the center of the center-side cam portions60in the circumferential directions S, but may be located closer to the center-side slipper cam surface60S. In this case, the oil passage271is located ahead of the pressure-side slipper cam surface90S in the second circumferential direction S2.