Clutch device

Provided is a clutch device configured so that close contactability between a cam surface of a center clutch and a cam surface of a pressure clutch can be improved and torque transmission can be stabilized accordingly. The clutch device (100) includes a center clutch (105) and a pressure clutch (112). The center clutch (105) includes center-side cam portions (107), a pressure clutch slide portion (106), and a lifter plate slide portion (110). The pressure clutch (112) includes pressure-side cam portions (114), a lifter plate (116), and a second center clutch slide portion (113). The lifter plate (116) includes first center clutch slide portions (120). A clearance (C2) between the second center clutch slide portion (113) and the pressure clutch slide portion (106) is set greater than a clearance (C1) between the first center clutch slide portion (120) and the lifter plate slide portion (110).

TECHNICAL FIELD

The present invention relates to a clutch device configured to transmit rotary drive force of a drive shaft to be rotatably driven by a motor to a driven shaft configured to drive a drive target body or block such transmission.

BACKGROUND ART

Typically, in a vehicle such as a two-wheel motor vehicle or a four-wheel motor vehicle, a clutch device has been used to transmit rotary drive force of a motor to a drive target body or block such transmission, and is arranged between the motor such as an engine and the drive target body such as a wheel. Generally, in the clutch device, multiple friction plates to be rotated by the rotary drive force of the motor and multiple clutch plates coupled to the drive target body are arranged facing each other, and transmission or blocking of the rotary drive force can be performed as necessary by close contact or separation of the friction plates and the clutch plates.

For example, Patent Literature 1 below discloses a clutch device including cam surfaces for quickly performing transmission or blocking of rotary drive force, and these cam surfaces are provided at opposing surfaces of a clutch member (a center clutch) and a pressure member (a pressure clutch) approaching each other or separating from each other with clutch plates being held. This clutch device is configured such that the clutch member and the pressure member quickly approach each other by assist torque. Such assist torque is generated when three cam surfaces formed at the pressure member move over three cam surfaces formed at the clutch member in a state in which the pressure member has slid in each of a rotation direction and an axial direction relative to the clutch member.

CITATION LIST

Patent Literature

However, the clutch device described in Patent Literature 1 above is configured such that three pairs of cam surfaces simultaneously slide on each other in such a manner that the pressure member is fitted onto a cylindrical portion formed at a center portion of the clutch member to slide on the cylindrical portion in the axial direction. Thus, in a case where fitting accuracy between the pressure member and the clutch member is low, tilting of the opposing cam surfaces is caused, and for this reason, it is difficult to stably generate sufficient thrust force. Thus, in the typical clutch device, there is a problem that torque transmission between the motor and the drive target body is unstable.

The present invention has been made to address the above-described problem. An object of the present invention is to provide the following clutch device. The clutch device is configured so that close contactability between a cam surface of a center clutch and a cam surface of a pressure clutch can be improved and torque transmission can be stabilized accordingly.

SUMMARY OF INVENTION

In order to achieve the above object, a feature of the present invention resides in a clutch device for transmitting rotary drive force of a drive shaft to a driven shaft or blocking transmission, the clutch device including: a center clutch holding a clutch plate arranged facing a friction plate to be rotatably driven by rotary drive of the drive shaft, coupled to the driven shaft, and rotatably driven together with the driven shaft; and a pressure clutch arranged facing the center clutch in a state in which the pressure clutch is able to approach or separate from the center clutch and is rotatable relative to the center clutch and elastically pressing the friction plate or the clutch plate; a cam portion provided at each of the center clutch and the pressure clutch and having a pair of cam surfaces for causing the pressure clutch to approach or separate from the center clutch to increase or decrease pressing force of the pressure clutch on the friction plate or the clutch plate upon relative rotation of the center clutch and the pressure clutch; and a lifter plate formed integrally with the pressure clutch and configured to transmit, to the pressure clutch, force of causing the pressure clutch to approach or separate from the center clutch, wherein the center clutch has each of a pressure clutch slide portion formed in a cylindrical shape on a cam surface formation side in an axial direction of the driven shaft and configured to slide the pressure clutch along the axial direction and a lifter plate slide portion formed in a cylindrical shape on a side opposite to a pressure clutch slide portion formation side in the axial direction and configured to slide the lifter plate along the axial direction, the lifter plate has a first center clutch slide portion configured to slide on the lifter plate slide portion, the pressure clutch has a second center clutch slide portion configured to slide on the pressure clutch slide portion, and a clearance between the second center clutch slide portion and the pressure clutch slide portion is set to a greater value than a clearance between the first center clutch slide portion and the lifter plate slide portion.

In this case, the cam surfaces include an assist cam surface and a slipper cam surface. In the case of the assist cam surface, when the pressure clutch approaches the center clutch, the cam surface formed at the pressure clutch moves over the cam surface formed at the center clutch, and accordingly, the force of causing the pressure clutch to approach the center clutch is increased. In the case of the slipper cam surface, when the pressure clutch separates from the center clutch, the cam surface formed at the pressure clutch moves over the cam surface formed at the center clutch, and accordingly, the force of separating the pressure clutch is increased. Thus, the cam portion in the present invention includes at least one of a pair of assist cam surfaces or a pair of slipper cam surfaces.

According to the feature of the present invention configured as described above, in the clutch device, the clearance between the second center clutch slide portion and the pressure clutch slide portion sliding on each other in the vicinity of the cam surfaces is set to a greater value than the clearance between the first center clutch slide portion and the lifter plate slide portion sliding on each other at a position apart from the cam surfaces. Thus, in the clutch device, the first center clutch slide portion slides on the lifter plate slide portion. Consequently, the pressure clutch can be guided on the same axis as that of the center clutch, a change in tilting of the pressure clutch can be accepted by the clearance between the second center clutch slide portion and the pressure clutch slide portion, and the cam surfaces of the pressure clutch can slide in close contact with the cam surfaces of the center clutch. With this configuration, the clutch device can improve close contactability between the cam surface of the center clutch and the cam surface of the pressure clutch, and can stabilize torque transmission.

Moreover, another feature of the present invention is that in the clutch device, the lifter plate slide portion is formed at an inner surface of a plate holding portion in a radial direction, the plate holding portion being formed in a cylindrical shape at the center clutch and holding the clutch plate.

According to another feature of the present invention configured as described above, in the clutch device, the lifter plate slide portion is formed at the inner surface of the relatively-thin cylindrical clutch plate holding portion in the radial direction, the clutch plate holding portion holding the clutch plate of the center clutch. Thus, slide heat between the lifter plate slide portion and the first center clutch slide portion sliding on each other through a narrow clearance can be effectively cooled by a cooling medium such as gas (e.g., air) or liquid (e.g., clutch oil) for air-cooling or oil-cooling the clutch plate and the friction plate.

Moreover, still another feature of the present invention is that in the clutch device, the center clutch has a plate receiving portion which is formed to project outwardly in a radial direction from a tip end portion of a plate holding portion formed in a cylindrical shape at the center clutch and holding the clutch plate and which is configured to receive the friction plate or the clutch plate pressed by the pressure clutch, and the lifter plate slide portion is formed at an inner surface of the plate receiving portion in the radial direction.

According to still another feature of the present invention configured as described above, in the clutch device, the lifter plate slide portion is formed at the inner surface of the thick plate receiving portion in the radial direction, the plate receiving portion being formed at the center clutch to project in the radial direction. Thus, the center clutch can stably guide the lifter plate fitted in a narrow clearance.

In addition, still another feature of the present invention is that in the clutch device, the first center clutch slide portion is formed such that a length in the axial direction of the driven shaft is longer than that of the second center clutch slide portion.

According to still another feature of the present invention configured as described above, the clutch device is formed such that the length of the first center clutch slide portion in the axial direction of the driven shaft is longer than that of the second center clutch slide portion. Thus, the pressure clutch can reciprocatably slide, with favorable accuracy, in the axial direction of the center clutch.

Note that a longer length of the first center clutch slide portion in the axial direction of the driven shaft than that of the second center clutch slide portion means that the length of contact of the first center clutch slide portion with the lifter plate slide portion in the axial direction is longer than the length of contact of the second center clutch slide portion with the pressure clutch slide portion in the axial direction. Moreover, the clutch device may be formed such that the length of the first center clutch slide portion in the axial direction of the driven shaft is shorter than that of the second center clutch slide portion. With this configuration, the acceptable amount of tilting of the pressure clutch can be increased.

Moreover, still another feature of the present invention is that in the clutch device, the second center clutch slide portion is formed at a position overlapping with the cam portion in the axial direction of the driven shaft.

According to still another feature of the present invention configured as described above, in the clutch device, the second center clutch slide portion is formed at the position overlapping with the cam portion in the axial direction of the driven shaft. Thus, the amount of tilting of the pressure clutch can be easily defined by the clearance between the second center clutch slide portion and the pressure clutch slide portion.

Note that in the clutch device, the second center clutch slide portion may be also formed at a position not overlapping with the cam portion on the side opposite to a first center clutch slide portion side in the axial direction of the driven shaft. According to such a configuration, in the clutch device, a distance between the first center clutch slide portion and the second center clutch slide portion is further increased. Thus, the amount of tilting of the pressure clutch can be more finely defined, and therefore, can be easily defined with high accuracy.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one embodiment of a clutch device according to the present invention will be described with reference to the drawings.FIG. 1is a sectional view illustrating the outline of an entire configuration of a clutch device100according to the present invention. Note that for the sake of easy understanding of the present invention, each figure referred to in the present specification is schematically illustrated. For example, some components are exaggeratingly illustrated. For this reason, dimensions and ratios among the components might vary. The clutch device100is a mechanical device for transmitting drive force of an engine (not shown) as a motor in a two-wheel motor vehicle (a motorcycle) to a wheel (not shown) as a drive target body or blocking such transmission, and is arranged between such an engine and a transmission (not shown).

Configuration of Clutch Device100

The clutch device100includes a clutch housing101. The clutch housing101is a component for holding friction plates103and transmitting the drive force from the engine to the friction plates103. The clutch housing101is formed in such a manner that an aluminum alloy material is shaped into a bottomed cylindrical shape. More specifically, an internal-gear-shaped spline is formed at a tubular portion of the clutch housing101. The multiple (nine in the present embodiment) friction plates103are spline-fitted in and held on the spline in a state in which the friction plates103are displaceable along an axis line direction of the clutch housing101and are rotatable integrally with the clutch housing101.

In the clutch housing101, a left side surface thereof as viewed in the figure is attached to an input gear102with a rivet101bthrough a torque damper101a. The input gear102is a gear component to be rotatably driven with the input gear102engaging with a drive gear coupled to a not-shown drive shaft to be rotatably driven by drive of the engine. The input gear102is rotatably supported on a later-described shaft111through a bearing (not shown). That is, the clutch housing101is, at a position concentric with the shaft111, integrally rotatably driven with the input gear102independently of the shaft111.

The friction plate103is a flat plate annular component to be pressed against a clutch plate104. The friction plate103is formed in such a manner that a thin plate member made of an aluminum material is shaped into an annular shape. In this case, external teeth configured to engage with the internal-tooth-shaped spline of the clutch housing101are formed at an outer peripheral portion of each friction plate103. Not-shown friction members including multiple pieces of paper are each bonded to both side surfaces (front and back surfaces) of each friction plate103, and a not-shown oil groove is formed between these friction members. Moreover, the friction plates103are formed to have the same size and shape for a center clutch105and a pressure clutch112provided inside the clutch housing101.

In the clutch housing101, the multiple (eight in the present embodiment) clutch plates104are held on the center clutch105and the pressure clutch112with each clutch plate104being sandwiched by corresponding ones of the friction plates103. The clutch plate104is a flat plate annular component to be pressed against the friction plate103. The clutch plate104is shaped in such a manner that a thin plate member made of a SPCC (cold rolled steel plate) material is punched into an annular shape. Not-shown oil grooves formed for holding clutch oil and having a depth of several μm to several tens of μm are each formed at both side surfaces (front and back surfaces) of each clutch plate104, and surface hardening treatment is performed for each of these surfaces for the purpose of improving abrasion resistance.

Moreover, at an inner peripheral portion of each clutch plate104, an internal-gear-shaped spline is formed. Such an internal-gear-shaped spline is spline-fitted in a plate holding portion105cformed at the center clutch105and a plate housing sub-portion112bformed at the pressure clutch112. The clutch plates104are formed to have the same size and shape for the center clutch105and the pressure clutch112. Note that needless to say, the above-described friction member may be provided at the clutch plate104instead of the friction plate103.

As illustrated in each ofFIGS. 2 and 3, the center clutch105is a component for housing each of the clutch plates104and the pressure clutch112together with the clutch housing101and transmitting the drive force of the engine to a transmission side. The center clutch105is formed in such a manner that an aluminum alloy material is shaped into a substantially cylindrical shape. More specifically, the center clutch105is formed in such a manner that a shaft coupling portion105a, a ring-shaped intermediate portion105b, and the plate holding portion105care mainly integrally formed.

The shaft coupling portion105ais a portion to be fitted in the pressure clutch112and to be coupled to the shaft111. The shaft coupling portion105ais formed in a cylindrical shape extending in an axial direction at a center portion of the center clutch105. At an inner peripheral surface of the shaft coupling portion105a, an internal-gear-shaped spline is formed along an axis line direction of the center clutch105. The shaft111is spline-fitted in such a spline. That is, the center clutch105rotates integrally with the shaft111at a position concentric with the clutch housing101and the shaft111.

Moreover, a pressure clutch slide portion106is formed at a center portion in the axial direction on an outer peripheral surface of the shaft coupling portion105a. The pressure clutch slide portion106is a portion onto which a second center clutch slide portion113of the pressure clutch112is fitted and on which the second center clutch slide portion113slides in the axial direction. The pressure clutch slide portion106is formed in a cylindrical shape. The pressure clutch slide portion106is formed at the same position in the axial direction as that of a later-described center-side cam portion107, i.e., at a position inside the center-side cam portion107in a radial direction. Moreover, the length of the pressure clutch slide portion106in the axial direction is slightly longer than the stroke of the pressure clutch112in the axial direction.

The ring-shaped intermediate portion105bis a portion formed between the shaft coupling portion105aand the plate holding portion105c. The ring-shaped intermediate portion105bis configured such that each of three support rod through-holes108is formed between adjacent ones of three center-side cam portions107arranged in a circumferential direction. Three center-side cam portions107are raised portions forming center-side assist cam surfaces107aand center-side slipper cam surfaces107b. Three center-side cam portions107are formed to extend along the circumferential direction of the center clutch105.

In this case, three center-side cam portions107are equally formed along the circumferential direction of the center clutch105. Moreover, each center-side cam portion107is formed such that an inner peripheral portion thereof is connected integrally with the shaft coupling portion105a. Further, the center-side assist cam surface107aand the center-side slipper cam surface107bare each formed at both end portions of each center-side cam portion107in the circumferential direction of the center clutch105.

Each center-side assist cam surface107ais a portion for generating, in cooperation with a later-described pressure-side assist cam surface114a, assist torque as force for enhancing pressure contact force between the friction plate103and the clutch plate104. Each center-side assist cam surface107ais configured as an inclined surface gradually projecting to a pressure clutch112side along the circumferential direction of the center clutch105. In this case, each center-side assist cam surface107ais formed in a direction facing the support rod through-hole108.

Each center-side slipper cam surface107bis a portion for generating, in cooperation with a later-described pressure-side slipper cam surface114b, slipper torque as force for promptly separating the friction plate103and the clutch plate104to bring these plates into a half-clutch state. Each center-side slipper cam surface107bis, on the side opposite to the center-side assist cam surface107ain the circumferential direction, configured as an inclined surface inclined in the same direction as that of the center-side assist cam surface107a.

In this case, each center-side slipper cam surface107bis formed in a direction facing the pressure clutch112side on the side opposite to the center-side assist cam surface107a. Moreover, each center-side slipper cam surface107bis formed to have the same length as the length of extension of the center-side assist cam surface107ain the radial direction. That is, each center-side slipper cam surface107bis formed to have the same area as the area of the center-side assist cam surface107aat the same position in the radial direction as the formation position of the center-side assist cam surface107a.

Note that each center-side slipper cam surface107bmay be formed to have an area different from the area of the center-side assist cam surface107aat a position (a position shifted in the radial direction) different from the formation position of the center-side assist cam surface107ain the radial direction. Moreover, the above-described half-clutch state of the clutch device100means an incomplete transmission state, and in this state, part of the drive force of the engine is transmitted to a drive wheel side in a state before the friction plates103and the clutch plates104in the clutch device100are fully in close contact with each other.

Three support rod through-holes108are through-holes for penetration of later-described three tubular support rods115. These three support rod through-holes108are equally formed at positions among three center-side cam portions107along the circumferential direction of the center clutch105.

The plate holding portion105cis a portion configured to hold part of the multiple clutch plates104together with the friction plates103. The plate holding portion105cis formed to have a cylindrical shape extending in the axial direction at an outer edge portion of the center clutch105. The outer peripheral portion of the plate holding portion105cincludes an external-gear-shaped spline. The plate holding portion105cholds the clutch plates104and the friction plates103in a state in which these plates are alternately arranged, are displaceable along the axis line direction of the center clutch105, and are rotatable integrally with the center clutch105. At the plate holding portion105c, oil holes105das through-holes for guiding the clutch oil from the inside to the outside of the plate holding portion105cin the radial direction are intermittently formed along the axial direction.

Moreover, a plate receiving portion105eis formed at a tip end portion of the plate holding portion105c. The plate receiving portion105eis a portion configured to receive the clutch plates104and the friction plates103pressed by the pressure clutch112such that these plates are sandwiched between the plate receiving portion105eand the pressure clutch112. The plate receiving portion105eis formed such that the tip end portion of the plate holding portion105cformed in the cylindrical shape projects outwardly in the radial direction in a flange shape. Moreover, a lifter plate slide portion110is formed at an inner peripheral surface of the plate holding portion105c, which is formed in the cylindrical shape, in the radial direction.

The lifter plate slide portion110is a portion on which a lifter plate116reciprocatably slides in the axial direction. The lifter plate slide portion110is formed by the inner peripheral surface of the plate holding portion105cformed in the cylindrical shape. The lifter plate slide portion110is, at an end portion of the plate holding portion105con a plate receiving portion105eside, formed to have a slightly longer length than the stroke of the lifter plate116in the axial direction.

The shaft111is a shaft body formed in a hollow shape. Of the shaft111, one end side (the right side as viewed in the figure) rotatably supports the input gear102and the clutch housing101through the bearing (not shown), and supports the spline-fitted center clutch105in a fixed manner through a nut (not shown). Of the shaft111, the other end portion (the outer left side as viewed in the figure) is coupled to the transmission (not shown) of the two-wheel motor vehicle. That is, the shaft111is equivalent to a driven shaft of the present invention. Note that inFIG. 1, the shaft111is indicated by a chain double-dashed line.

As illustrated inFIG. 4, the pressure clutch112is a component for pressing the friction plates103to cause the friction plates103and the clutch plates104to closely contact each other. The pressure clutch112is formed in such a manner that an aluminum alloy material is shaped into a substantially discoid shape having the substantially same outer diameter size as the outer diameter of the clutch plate104. More specifically, the pressure clutch112is, as illustrated inFIG. 4, mainly formed in such a manner that a ring-shaped intermediate portion112aand the plate housing sub-portion112bare integrally formed.

The ring-shaped intermediate portion112ais formed in a ring shape with a raised-recessed portion. The ring-shaped intermediate portion112ais configured such that intermediate portions of three pressure-side cam portions114arranged on the circumference of such a ring body each have three tubular support rods115. The ring-shaped intermediate portion112ais slidably fitted onto the outer peripheral surface of the shaft coupling portion105aof the center clutch105. More specifically, the second center clutch slide portion113formed by an inner peripheral surface of a through-hole formed at a center portion is, at the ring-shaped intermediate portion112a, slidably fitted onto the pressure clutch slide portion106formed at the outer peripheral surface of the shaft coupling portion105a.

With this configuration, the pressure clutch112is rotatably provided independently of the center clutch105and the shaft111at a position concentric with the clutch housing101, the center clutch105, and the shaft111. The second center clutch slide portion113is a portion configured to allow tilting of the pressure clutch112with respect to the axial direction while guiding the pressure clutch112in the axial direction. The length of the second center clutch slide portion113in the axial direction is shorter than the length of a later-described first center clutch slide portion120in the axial direction.

A clearance C2as a clearance between the second center clutch slide portion113and the pressure clutch slide portion106is, as illustrated inFIG. 5, is set to such an amount that tilting of the pressure clutch112with respect to the axial direction when the pressure clutch112reciprocatably slides in the axial direction is allowed. In tilting of the pressure clutch112in this case, smooth reciprocatable slide of the pressure clutch112in the axial direction is ensured. Further, in such tilting of the pressure clutch112, when the center-side cam portions107and the pressure-side cam portions114slide in contact with each other, cam surfaces of the pressure-side cam portions114and cam surfaces of the center-side cam portions107are brought into or come close to a parallel state, and therefore, are ideally brought into or come close to a surface contact state across the entire surface.

The clearance C2may be set to equal to or greater than three times and equal to or less than ten times as great as a later-described clearance C1, and may be more preferably set to equal to or greater than four times and equal to or less than seven times. In this case, the clearance C2may be set within a range of 0.1 mm to 0.5 mm. In the present embodiment, the clearance C2is set to 0.2 mm.

Three pressure-side cam portions114are raised portions forming the pressure-side assist cam surfaces114aand the pressure-side slipper cam surfaces114b. Three pressure-side cam portions114are formed to extend along the circumferential direction of the pressure clutch112. In this case, three pressure-side cam portions114are equally formed along the circumferential direction of the pressure clutch112. Moreover, each pressure-side cam portion114is formed such that an outer peripheral portion thereof is connected integrally with the plate housing sub-portion112b. Further, the pressure-side assist cam surface114aand the pressure-side slipper cam surface114bare each formed at both end portions of each pressure-side cam portion114in the circumferential direction of the pressure clutch112.

Each pressure-side assist cam surface114ais a portion configured to slide on the center-side assist cam surface107aof the center clutch105. Each pressure-side assist cam surface114ais configured as an inclined surface gradually projecting to a center clutch105side along the circumferential direction of the pressure clutch112. That is, the center-side assist cam surfaces107aand the pressure-side assist cam surfaces114aform an assist mechanism.

Each pressure-side slipper cam surface114bis a portion configured to slide on the center-side slipper cam surface107b. Each pressure-side slipper cam surface114bis configured as an inclined surface extending in the same direction as that of the pressure-side assist cam surface114aon the side opposite to the pressure-side assist cam surface114ain the circumferential direction. That is, the center-side slipper cam surfaces107band the pressure-side slipper cam surfaces114bform a slipper mechanism.

Each pressure-side slipper cam surface114bis formed to have the same length and area as the length and area of the pressure-side assist cam surface114ain the radial direction. That is, each pressure-side slipper cam surface114bis formed to have the same area as the area of the center-side slipper cam surface107bat a position facing the center-side slipper cam surface107b. Note that each pressure-side slipper cam surface114bmay be formed to have an area different from the area of the pressure-side assist cam surface114aat a position (a position shifted in the radial direction) different from the formation position of the pressure-side assist cam surface114ain the radial direction.

Three tubular support rods115are cylindrical portions extending in a columnar shape in the axial direction of the center clutch105to support the lifter plate116, and at inner peripheral portions thereof, are provided with internal threads. Three tubular support rods115are equally formed along the circumferential direction of the pressure clutch112.

The plate housing sub-portion112bis a portion configured to hold the other part of the multiple clutch plates104together with the friction plates103. The plate housing sub-portion112bis, at an outer edge portion of the pressure clutch112, formed to have a cylindrical shape extending in the axial direction. An outer peripheral portion of the plate housing sub-portion112bincludes an external-gear-shaped spline. The plate housing sub-portion112bholds the clutch plates104and the friction plates103in a state in which these plates are alternately arranged, are displaceable along an axis line direction of the pressure clutch112, and are rotatable integrally with the pressure clutch112. In this case, the plate housing sub-portion112bis formed to have a greater inner diameter than that of the plate holding portion105cof the center clutch105. The plate housing sub-portion112bis configured fittable onto the plate holding portion105cin a non-contact state. A plate pressing portion112cis formed at a tip end portion of the plate housing sub-portion112b.

The plate pressing portion112cis a portion for pressing the clutch plates104and the friction plates103held on the plate holding portion105ctoward the plate receiving portion105eside such that the clutch plates104and the friction plates103closely contact each other with high pressure. The plate pressing portion112cis formed such that a base portion of the plate housing sub-portion112bformed in the cylindrical shape projects outwardly in the radial direction in a flange shape.

As illustrated inFIG. 6, the lifter plate116is a component for reciprocatably displacing the pressure clutch112in the axial direction, and is formed in such a manner that a metal material is formed into a cylindrical shape. More specifically, the lifter plate116mainly includes each of an operation receiving portion116aand projecting portions116b. The operation receiving portion116ais a portion to be pressed by a clutch release mechanism through a release pin117. The operation receiving portion116ais formed to have a cylindrical shape housing the bearing pressed by the release pin117. Here, the clutch release mechanism is a mechanical device configured to press the release pin117to a shaft111side according to operation of a clutch operation lever (not shown) by a driver of a self-propelled vehicle on which the clutch device100is mounted. Note that inFIG. 1, the release pin117is indicated by a chain double-dashed line.

The projecting portion116bis a portion configured such that a clutch spring118is sandwiched between the projecting portion116band the ring-shaped intermediate portion105bof the center clutch105and configured to guide the lifter plate116in the axial direction. The projecting portion116bis formed in a plate shape projecting outward of an outer peripheral portion of the operation receiving portion116ain the radial direction. In this case, the projecting portions116bare formed to project from three spots of the outer peripheral portion of the operation receiving portion116aat equal intervals in the circumferential direction.

These projecting portions116bare each attached to tip end portions of three tubular support rods115through attachment bolts in a state in which the ring-shaped intermediate portion105band the projecting portions116bsandwich the clutch springs118on the opposite side of the center clutch105from the pressure clutch112. That is, the lifter plate116displaces and rotates relative to the center clutch105integrally with the pressure clutch112.

The clutch spring118is an elastic body for pressing the pressure clutch112to the center clutch105side to press the plate pressing portion112cof the pressure clutch112against the friction plates103. The clutch spring118includes a coil spring formed in such a manner that spring steel is wound in a spiral shape. The clutch spring118is arranged between adjacent ones of three tubular support rods115. Moreover, the first center clutch slide portion120is formed at a tip end portion of each projecting portion116b.

The first center clutch slide portion120is a portion for guiding the lifter plate116in the axial direction. The first center clutch slide portions120are formed to have a circumferential surface at outer peripheral surfaces of three projecting portions116b. In this case, each first center clutch slide portion120is formed to have a greater thickness than that of an inner portion for pressing the clutch spring118. Moreover, the length of the first center clutch slide portion120in the axial direction is longer than the length of the second center clutch slide portion113in the axial direction.

Here, as illustrated inFIG. 7, the clearance C1as a clearance between the first center clutch slide portion120and the lifter plate slide portion110is set to such an amount that when the lifter plate116reciprocatably slides in the axial direction, a change in the posture of the lifter plate116is suppressed while the lifter plate116is smoothly reciprocatably sliding. Specifically, the clearance C1is set within a range of 0.01 mm to 0.08 mm. In the present embodiment, the clearance C1is set to 0.02 mm.

The clutch device100is filled with a predetermined amount of clutch oil (not shown). The clutch oil is mainly supplied to among the friction plates103and the clutch plates104to absorb friction heat generated thereamong and prevent abrasion of the friction members. That is, the clutch device100is a so-called wet multiplate friction clutch device.

Actuation of Clutch Device100

Next, actuation of the clutch device100configured as described above will be described. As described above, the clutch device100is arranged between the engine and the transmission in the vehicle. The clutch device100performs, according to operation of the clutch operation lever by the driver of the vehicle, transmission of the drive force of the engine to the transmission and blocking of such transmission.

Specifically, as illustrated in each ofFIGS. 1 and 8(A), in the clutch device100, in a case where the driver (not shown) of the vehicle does not operate the clutch operation lever (not shown), the clutch release mechanism (not shown) does not press the release pin117, and therefore, the pressure clutch112presses the friction plates103by elastic force of the clutch springs118. Thus, the friction plates103and the clutch plates104are brought into a clutch ON state in which these plates are pressed against each other and are friction-coupled to each other, and the center clutch105is rotatably driven. That is, rotary drive force of the motor is transmitted to the center clutch105, and in this manner, the shaft111is rotatably driven.

In such a clutch ON state, the pressure clutch112displaces (a b-arrow in the figure) in the direction of approaching the center clutch105while rotating relative to the center clutch105by cam action (an a-arrow in the figure) in which the pressure-side assist cam surface114aformed at the pressure clutch112moves over the center-side assist cam surface107aformed at the center clutch105. This leads to action of the assist function of rapidly enhancing pressing force. Accordingly, the pressure clutch112is pressed against the center clutch105with strong force by the assist mechanism.

In the course of action of the assist function of causing the center-side assist cam surface107aand the pressure-side assist cam surface114ato closely contact each other with strong pressure, in a case where the center-side assist cam surface107aand the pressure-side assist cam surface114aare not parallel with each other, but the pressure-side assist cam surface114atilts with respect to the center-side assist cam surface107a, the entirety of the pressure clutch112is inclined such that the pressure-side assist cam surface114ais along the center-side assist cam surface107a.

This is because the clearance C2is provided between the pressure clutch slide portion106of the center clutch105and the second center clutch slide portion113of the pressure clutch112and a second center clutch slide portion113side of the pressure clutch112is tiltably supported. With this configuration, the center-side assist cam surface107aand the pressure-side assist cam surface114aare brought into or come close to the parallel state, and therefore, the cam surfaces thereof are brought into or come close to the surface contact state across the entire surface. Thus, efficient torque transmission is performed.

Moreover, in this clutch ON state, in a case where the number of rotations of the drive wheel side exceeds the number of rotations of an engine side due to, e.g., shift down operation for the transmission by the driver, back torque might act on the clutch device100because the number of rotations of the shaft111exceeds the number of rotations of the input gear102. In this case, in the clutch device100, the pressure clutch112displaces (a d-arrow in the figure) in the direction of separating from the center clutch105while rotating relative to the center clutch105by cam action (a c-arrow in the figure) in which the pressure-side slipper cam surface114bformed at the pressure clutch112moves over the center-side slipper cam surface107bformed at the center clutch105, as illustrated inFIG. 8(B). This leads to action of the slipper function of rapidly weakening the pressing force. Thus, in the clutch device100, the friction plates103and the clutch plates104start separating from each other. Accordingly, a state in which these plates are pressed against each other is weakened, and a state in which friction coupling is weakened is brought.

In the course of action of the slipper function of causing the center-side slipper cam surface107band the pressure-side slipper cam surface114bto closely contact each other with strong pressure, in a case where the center-side slipper cam surface107band the pressure-side slipper cam surface114bare not parallel with each other, but the pressure-side slipper cam surface114btilts with respect to the center-side slipper cam surface107b, the entirety of the pressure clutch112is, as in a case where the assist function acts, inclined such that the pressure-side slipper cam surface114bis along the center-side slipper cam surface107b. With this configuration, the center-side slipper cam surface107band the pressure-side slipper cam surface114bare brought into or come close to the parallel state, and therefore, the cam surfaces thereof are brought into or come close to the surface contact state across the entire surface. Thus, efficient torque transmission is performed.

On the other hand, in the clutch device100, in a case where the driver of the vehicle has operated the clutch operation lever in the clutch ON state, the clutch release mechanism (not shown) presses the release pin117as illustrated inFIG. 9. Thus, the pressure clutch112displaces in the direction of separating from the center clutch105against the elastic force of the clutch springs118. In this case, the first center clutch slide portions120of the lifter plate116slide on the lifter plate slide portion110of the center clutch105through the clearance C1, and therefore, the pressure clutch112is smoothly and stably guided along the axial direction of the center clutch105.

Accordingly, the center clutch105is brought into a clutch OFF state in which friction coupling among the friction plates103and the clutch plates104is cancelled. Thus, a state in which rotary drive is attenuated or stopped is brought. That is, the rotary drive force of the motor is blocked from the center clutch105. In this case, the center-side assist cam surface107aand the pressure-side assist cam surface114aare in a separate state, and the center-side slipper cam surface107band the pressure-side slipper cam surface114bare in a separate state. Thus, each of the assist torque and the slipper torque is not generated.

In a case where the driver releases the clutch operation lever in the clutch OFF state, pressing of the lifter plate116by the clutch release mechanism (not shown) through the release pin117is cancelled. Thus, the pressure clutch112displaces in the direction of approaching the center clutch105by the elastic force of the clutch springs118. In this case, the first center clutch slide portions120of the lifter plate116slide on the lifter plate slide portion110of the center clutch105through the clearance C1, and therefore, the pressure clutch112is smoothly and stably guided along the axial direction of the center clutch105.

In the course of transition from the clutch OFF state to the clutch ON state, in a case where relative rotation between the center clutch105and the pressure clutch112is caused, the assist function acts. In this case, if the pressure-side assist cam surface114atilts with respect to the center-side assist cam surface107awhen the pressure-side assist cam surface114acontacts the center-side assist cam surface107a, the entirety of the pressure clutch112is, as in action of the assist function, inclined such that the pressure-side assist cam surface114ais along the center-side assist cam surface107a. Thus, the center-side assist cam surface107aand the pressure-side assist cam surface114aare brought into or come close to the parallel state, and therefore, the cam surfaces thereof are brought into or come close to the surface contact state across the entire surface. Thus, efficient torque transmission is performed.

As can be understood from actuation description above, according to the above-described embodiment, in the clutch device100, the clearance C2between the second center clutch slide portion113and the pressure clutch slide portion106sliding on each other in the vicinity of the center-side cam portions107and the pressure-side cam portions114is set to a greater value than the clearance C1between each first center clutch slide portion120and the lifter plate slide portion110sliding on each other at a position apart from each of these cam portions. Thus, in the clutch device100, the first center clutch slide portions120slide on the lifter plate slide portion110. Consequently, the pressure clutch112can be guided on the same axis as that of the center clutch105, a change in tilting of the pressure clutch112can be accepted by the clearance C2between the second center clutch slide portion113and the pressure clutch slide portion106, and the pressure-side cam portions114of the pressure clutch112can slide in close contact with the center-side cam portions107of the center clutch105. With this configuration, the clutch device100can improve close contactability between the center-side cam portion107of the center clutch105and the pressure-side cam portion114of the pressure clutch112, and can stabilize torque transmission.

Further, implementation of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the object of the present invention. Note that in each variation described below, the same reference numerals as or corresponding reference numerals to those assigned to the clutch device100are used to represent components similar to those of the clutch device100in the above-described embodiment, and description thereof will be omitted as necessary.

For example, in the above-described embodiment, the clutch device100is configured such that the center-side cam portion107includes the center-side assist cam surface107aand the center-side slipper cam surface107band the pressure-side cam portion114includes the pressure-side assist cam surface114aand the pressure-side slipper cam surface114b. That is, the center-side cam portion107and the pressure-side cam portion114are equivalent to a cam portion according to the present invention. However, each of the center-side cam portion107and the pressure-side cam portion114may include at least one of the assist-side cam surface and the slipper-side cam surface.

Moreover, in the above-described embodiment, the lifter plate slide portion110is formed at an inner surface of the plate holding portion105cin the radial direction. Thus, the lifter plate116slides at a position facing the inside of the plate holding portion105cin the radial direction. With this configuration, slidability is improved by the clutch oil supplied to the friction plates103and the clutch plates104through the oil holes105dto cool these plates. However, the lifter plate slide portion110may be formed at an inner surface of the plate receiving portion105ein the radial direction, and may be configured such that the lifter plate116slides on such a portion. In this case, the plate receiving portion105emay be formed to have a thickness (a length in the axial direction) of equal to or greater than the stroke of the lifter plate116. According to such a configuration, the lifter plate116can stably slide by the thick plate receiving portion105e.

Further, in the above-described embodiment, the first center clutch slide portion120is formed such that the length of the shaft111in the axial direction is longer than that of the second center clutch slide portion113. Thus, the clutch device100can reciprocatably slide, with favorable accuracy, the pressure clutch112in the axial direction of the center clutch105. However, in the clutch device100, the length of the shaft111in the axial direction at the first center clutch slide portion120may be shorter than that of the second center clutch slide portion113so that the acceptable amount of tilting of the pressure clutch112can be increased. Note that needless to say, the length of the shaft111in the axial direction may be, at the first center clutch slide portion120, the same as the length of the second center clutch slide portion113.

In addition, in the above-described embodiment, the second center clutch slide portion113is formed at the position overlapping with the pressure-side cam portions114in the axial direction of the shaft111, i.e., formed inside the pressure-side cam portions114in the radial direction. Thus, in the clutch device100, the amount of tilting of the pressure clutch112can be easily defined by the clearance C2between the second center clutch slide portion113and the pressure clutch slide portion106.

However, as illustrated inFIG. 10, the second center clutch slide portion113may be also formed at a position not overlapping with the pressure-side cam portions114on the side opposite to a first center clutch slide portion120side in the axial direction of the shaft111. According to such a configuration, in the clutch device100, a distance between the first center clutch slide portion120and the second center clutch slide portion113is further increased. Thus, the amount of tilting of the pressure clutch112can be more finely defined, and therefore, can be easily defined with high accuracy.

Moreover, in the above-described embodiment, the first center clutch slide portions120are each formed at three projecting portions116bof the lifter plate116. However, four or more projecting portions116bmay be provided, and the first center clutch slide portions120may be formed on the outer peripheral surfaces of these projecting portions116b. Alternatively, the projecting portion116bmay be formed in a discoid shape connected as one, and the first center clutch slide portion120may be formed at an outer peripheral surface of such a discoid body.

Further, in the above-described embodiment, the second center clutch slide portion113is formed as the circumferential surface continuous to an inner peripheral surface of the ring-shaped intermediate portion112a. However, one or more projecting portions projecting inwardly in the radial direction may be provided on the inner peripheral surface of the ring-shaped intermediate portion112a, and the second center clutch slide portion113may be formed in an arc shape at inner peripheral surfaces of such projecting portions.

LIST OF REFERENCE SIGNS