Driving force transmission device

Abstract

This driving force transmission device 11 comprises a clutch 20 and a ball cam mechanism 3 that presses the clutch 20. The ball cam mechanism 3 includes: a fixed cam plate 31 and a rotary cam plate 32 that are rotated relative to each other by an electric motor 4; a plurality of cam balls 33; and a retainer 34 that retains the plurality of cam balls 33. The retainer 34 has: a plurality of holding parts 341 in which holding holes 340 that respectively accommodate the plurality of cam balls 33 are formed; and a plurality of arc parts 342 between the plurality of holding parts 341. Outside concave parts 342a recessed from an end part on the outer diameter side of the retainer 34 toward the inner diameter side are formed in the arc parts 342, and the outside concave parts 342a are in communication with rolling grooves 310, 320 of the fixed cam plate 31 and the rotary cam plate 32.

Description

Power transmission device

[0001] This invention relates to a power transmission device.

[0002] Conventionally, power transmission devices that transmit the driving force from a vehicle's power source to the wheels include a clutch that can intermittently transmit the driving force and a ball cam mechanism that presses the clutch.

[0003] The power transmission device described in Patent Document 1 comprises a multi-plate clutch having a plurality of clutch plates arranged in the axial direction, a ball cam mechanism that presses the multi-plate clutch in the axial direction via a pressing member, and a servo motor that operates the ball cam mechanism. The ball cam mechanism comprises a fixed cam plate and a rotating cam plate, and a plurality of cam balls held by a retainer are arranged between the fixed cam plate and the rotating cam plate. A portion of each cam ball in the circumferential direction is housed in a rolling groove formed in the fixed cam plate, and the other portion in the circumferential direction is housed in a rolling groove formed in the rotating cam plate.

[0004] When the rotational force generated by the servo motor rotates the cam plate, the cam balls roll in the rolling grooves, pressing against the multiple clutch plates of the multi-plate clutch and generating friction. This friction transmits driving force between the input shaft to which the clutch hub is fixed and the bevel gear to which the clutch drum is fixed. The driving force transmitted from the input shaft to the bevel gear is then transmitted to the propeller shaft via the rear wheel output shaft, which has an output pinion meshed with the bevel gear. An oil passage is formed along the axial direction of the input shaft, and lubricating oil is supplied to the multi-plate clutch and ball cam mechanism through this oil passage.

[0005] Japanese Patent Publication No. 2009-220593

[0006] For example, when forming an oil passage in a rotating shaft, such as the input shaft described in Patent Document 1, it is necessary to form a narrow, long hole along the axial direction, which increases processing costs. Furthermore, a rotary joint is required to supply lubricating oil to the oil passage, which also increases component costs.

[0007] Furthermore, for ball cam mechanisms, it is conceivable to supply lubricating oil to the rolling grooves by, for example, dripping lubricating oil between the fixed cam plate and the rotating cam plate from above. However, if the gap between the retainer and the fixed cam plate and the rotating cam plate is narrow, it is difficult to supply a sufficient amount of lubricating oil.

[0008] Therefore, the present invention aims to provide a drive force transmission device having a ball cam mechanism that facilitates the supply of lubricating oil to the rolling grooves of a pair of cam plates that sandwich a plurality of cam balls held in a retainer in the axial direction. Furthermore, the present invention aims to provide a drive force transmission device that can supply lubricating oil to a clutch via a ball cam mechanism.

[0009] To achieve the above objective, the present invention provides a drive force transmission device comprising: a clutch whose intermittent state of driving force changes when pressed in the axial direction; a ball cam mechanism that presses the clutch in the axial direction; and a rotary actuator that actsuates the ball cam mechanism, wherein the ball cam mechanism has a pair of cam plates facing each other, a plurality of cam balls disposed between the pair of cam plates, and an annular retainer that holds the plurality of cam balls, wherein the rotational force of the rotary actuator causes the pair of cam plates to rotate relative to each other, causing the plurality of cam balls to roll in a plurality of rolling grooves formed in each of the pair of cam plates, thereby pressing the clutch, wherein the retainer has a plurality of holding portions, each having a holding hole for accommodating the plurality of cam balls, and a plurality of arc portions between the plurality of holding portions, wherein an outer recess extending inward from the outer diameter end of the retainer is formed in at least one of the plurality of arc portions, and the outer recess communicates with at least one of the plurality of rolling grooves of the pair of cam plates.

[0010] Furthermore, in order to achieve the above objective, the present invention provides a drive force transmission device in which an inner recess is formed in at least one of the plurality of arc portions, extending from the inner diameter end of the retainer toward the outer diameter, and the inner recess communicates with at least one of the plurality of rolling grooves of the pair of cam plates together with the outer recess.

[0011] The drive force transmission device according to the present invention facilitates the supply of lubricating oil to the rolling grooves of the pair of cam plates of the ball cam mechanism. Furthermore, lubricating oil can be circulated inside and outside the retainer via the outer and inner recesses of the retainer and the rolling grooves of the pair of cam plates, and the lubricating oil that has circulated inside and outside the retainer can be supplied to various parts of the drive force transmission device, including the clutch.

[0012] Figure 1 is a schematic diagram illustrating the general configuration of a vehicle equipped with a power transmission device according to an embodiment of the present invention. Figure 2 is a cross-sectional view of the power transmission device and differential along the vertical direction. Figure 3 is a configuration diagram showing a cam plate fixed to the first case member by a plurality of bolts. Figure 4 is a cross-sectional view showing a reduction mechanism, a ball cam mechanism, and a clutch mechanism. Figure 5 is an exploded perspective view of the ball cam mechanism. Figure 6A is a plan view showing the side of the fixed cam plate facing the rotating cam plate. Figure 6B is a cross-sectional view showing one rolling groove formed in the fixed cam plate in a cross section along the circumferential direction of the fixed cam plate. Figure 7A is a plan view showing the side of the rotating cam plate facing the fixed cam plate. Figure 7B is a cross-sectional view showing one rolling groove formed in the rotating cam plate in a cross section along the circumferential direction of the rotating cam plate. Figure 8A is a configuration diagram of the retainer viewed from the axial direction. Figure 8B is a configuration diagram of the retainer viewed from a direction perpendicular to the axial direction. Figure 9A is a configuration diagram of the fixed cam plate and retainer viewed from the rotating cam plate side. Figure 9B is a configuration diagram showing the rotating cam plate and retainer as viewed from the fixed cam plate 31 side. Figure 10 is a configuration diagram showing a retainer according to a modified example.

[0013] [Embodiments] Embodiments of the present invention will be described with reference to the drawings. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some parts specifically illustrate various technically preferable technical matters, but the technical scope of the present invention is not limited to these specific embodiments.

[0014] Figure 1 is a schematic diagram illustrating the general configuration of a vehicle 1 equipped with a drive force transmission device 11 according to an embodiment of the present invention. In the following description, "left side" and "right side" refer to the left and right sides of the vehicle 1 in the vehicle width direction.

[0015] Vehicle 1 includes a power transmission device 11, a differential 12, a drive source 13 that generates driving force, a transmission 14 that changes the output rotation of the drive source 13, a drive shaft 15 that transmits the driving force from the drive source 13 via the transmission 14 to the differential 12, left and right wheels 16 and 17, left and right hub units 161 and 171 provided corresponding to the left and right wheels 16 and 17 respectively, a left drive shaft 18 positioned between the left hub unit 161 and the differential 12, a right drive shaft 19 positioned between the right hub unit 171 and the differential 12, and a case 7 that houses the power transmission device 11 and the differential 12.

[0016] The drive source 13 is, for example, an internal combustion engine or an electric motor, which generates the driving force for the vehicle 1 to move. The drive force transmission device 11 and the differential device 12 constitute a drive force distribution device 10 that distributes the driving force of the drive source 13 to the drive shafts 18 and 19. The left drive shaft 18 has an intermediate shaft 180, an outboard constant velocity joint 181 connected to the hub unit 161, and an inboard constant velocity joint 8 connected to the differential device 12. The right drive shaft 19 has an intermediate shaft 190, an outboard constant velocity joint 191 connected to the hub unit 171, and an inboard constant velocity joint 9 connected to the differential device 12. The outboard constant velocity joints 181 and 191 are fixed constant velocity universal joints, such as ball-type constant velocity joints. The inboard constant velocity joints 8 and 9 are sliding constant velocity universal joints, such as tripod-type constant velocity joints.

[0017] The differential gear 12 includes a ring gear 121 meshed with the drive shaft 15, a differential case 122 that rotates integrally with the ring gear 121, a pinion shaft 123 fixed to the differential case 122, a pair of pinion gears 124 pivotally supported on the pinion shaft 123, and left and right side gears 125 and 126 meshed with the pair of pinion gears 124. The outer coupling member 81 of the constant velocity joint 8 is attached to the left side gear 125 so as not to rotate relative to it. The outer coupling member 91 of the constant velocity joint 9 is attached to the right side gear 126 so as not to rotate relative to it.

[0018] The drive force transmission device 11 comprises, as its main components, a clutch mechanism 2 having a clutch 20, a ball cam mechanism 3 that presses the clutch 20, an electric motor 4 as a rotary actuator, a control device 40 that controls the electric motor 4, and a reduction mechanism 5 that reduces the rotation of the output rotating shaft 41 of the electric motor 4.

[0019] The ball cam mechanism 3 includes a pair of cam plates 31 and 32 facing each other along the axial direction, a plurality of cam balls 33 positioned between the pair of cam plates 31 and 32, and an annular retainer 34 that holds the plurality of cam balls 33. When the output rotating shaft 41 of the electric motor 4 rotates, its rotational force is amplified by the reduction mechanism 5, causing the pair of cam plates 31 and 32 to rotate relative to each other and pressing the clutch 20.

[0020] Case 7 has a first case member 71 and a second case member 72, and the first case member 71 and the second case member 72 are fastened together by a plurality of bolts 73 at the outer circumference of the differential gear 12. The clutch mechanism 2, ball cam mechanism 3, and reduction mechanism 5 of the drive force transmission device 11 are housed in the first case member 71 together with a part of the outer joint member 81 of the constant velocity joint 8.

[0021] The drive force transmission device 11 can switch between a state in which drive force is transmitted between the differential case 122 and the outer joint member 81 of the constant velocity joint 8 by the clutch mechanism 2, and a state in which drive force is not transmitted between them. When the clutch mechanism 2 is activated and drive force is transmitted between the differential case 122 and the outer joint member 81 of the constant velocity joint 8 by the clutch mechanism 2, the relative rotation between the differential case 122 and the left side gear 125 is restricted, and this also restricts the relative rotation between the differential case 122 and the right side gear 126. On the other hand, when the clutch mechanism 2 is not activated, the left side gear 125 and the right side gear 126 can rotate relative to each other by the rotation of the pair of pinion gears 124.

[0022] In other words, in this embodiment, the drive force transmission device 11 functions as a differential limiting device that restricts the relative rotation between the left side gear 125 and the right side gear 126. In this embodiment, the case in which the drive force transmission device 11 is positioned to the left of the differential gear 12 in the vehicle width direction is described, but the drive force transmission device 11 may also be positioned to the right of the differential gear 12.

[0023] Figure 2 is a cross-sectional view of the drive force transmission device 11, differential 12, case 7, and constant velocity joints 8 and 9 in a cross-section along the vertical direction. Figure 3 is a configuration diagram showing a cam plate 31 fixed to the first case member 71 by a plurality of bolts 74. Figure 4 is a cross-sectional view showing the reduction mechanism 5, ball cam mechanism 3, and clutch mechanism 2. Figure 2 shows a cross-section along line A-A in Figure 3, and Figure 4 shows a cross-section along line B-B in Figure 3.

[0024] In Figures 2 and 4, the rotation axis O of the differential case 122 is shown by a dashed line. The left and right side gears 125, 126 and the outer joint members 81, 91 of the constant velocity joints 8, 9 are rotatable relative to the differential case 122 about the rotation axis O. Hereinafter, the direction parallel to the rotation axis O will be referred to as the axial direction.

[0025] Each constant velocity joint 8, 9 comprises outer joint members 81, 91, tripod members 82, 92 to which intermediate shafts 180, 190 are connected so as not to rotate relative to each other, and a plurality of rollers 83, 93 assembled to the tripod members 82, 92. Each outer joint member 81, 91 integrally comprises a bottomed cylindrical portion 811, 911 that houses the tripod members 82, 92 and the plurality of rollers 83, 93, and a stem portion 812, 912 provided so as to protrude axially from the end of the cylindrical portion 811, 911 on the differential gear 12 side.

[0026] The differential case 122 has a cylindrical portion 122a that supports both ends of the pinion shaft 123, a left wall portion 122b and a right wall portion 122c, a left cylindrical portion 122d extending axially from the inner diameter end of the left wall portion 122b, and a right cylindrical portion 122e extending axially from the inner diameter end of the right wall portion 122c. A bearing 61 is positioned between the right cylindrical portion 122e and the second case member 72.

[0027] The left side gear 125 has a gear portion 125a that meshes with a pair of pinion gears 124 and a cylindrical portion 125b that is inserted inside the left cylindrical portion 122d of the differential case 122. The stem portion 812 of the outer coupling member 81 is fitted inside the cylindrical portion 125b in a manner that prevents relative rotation. Similarly, the right side gear 126 has a gear portion 126a that meshes with a pair of pinion gears 124 and a cylindrical portion 126b that is inserted inside the right cylindrical portion 122e of the differential case 122. The stem portion 912 of the outer coupling member 91 is fitted inside the cylindrical portion 126b in a manner that prevents relative rotation.

[0028] The clutch mechanism 2 allows the intermittent state of the driving force to continuously change in accordance with the rotational torque of the electric motor 4 as the clutch 20 is pressed in the axial direction. In this embodiment, as shown in Figure 4, the clutch 20 is a multi-plate clutch having a plurality of outer clutch plates 201 and a plurality of inner clutch plates 202. The ball cam mechanism 3 is operated by the electric motor 4 and presses the clutch 20 in the axial direction. When the clutch 20 is pressed in the axial direction, the driving force is transmitted by the frictional force generated by the frictional contact between the plurality of outer clutch plates 201 and the plurality of inner clutch plates 202. Although not shown in the figures, the outer clutch plates 201 and the inner clutch plates 202 have axial through holes formed as oil holes to allow lubricating oil to flow in the axial direction.

[0029] The clutch mechanism 2 includes a clutch drum 21 that rotates integrally with a plurality of outer clutch plates 201, and a clutch hub 22 that rotates integrally with a plurality of inner clutch plates 202. The clutch drum 21 integrally includes an outer cylindrical portion 211 having a spline engagement portion 210 on its inner circumference that engages with the plurality of outer clutch plates 201 so as to be axially movable, an annular wall portion 212 aligned axially with the clutch 20, a connecting portion 213 that is non-rotatably connected to the cylindrical portion 125b of the left side gear 125, and a connecting portion 214 that connects the wall portion 212 and the connecting portion 213. A bearing 62 is positioned between the wall portion 212 of the clutch drum 21 and the first case member 71.

[0030] The clutch hub 22 integrally comprises an inner cylindrical portion 221 having a spline engagement portion 220 on its outer circumference into which a plurality of inner clutch plates 202 engage in an axially movable manner, a connecting portion 222 connected to the left cylindrical portion 122d of the differential case 122 in a manner that prevents relative rotation, and a connecting portion 223 connecting the inner cylindrical portion 221 and the connecting portion 222. A washer 63 is positioned between the connecting portion 214 of the clutch drum 21 and the connecting portion 223 of the clutch hub 22.

[0031] One of the pair of cam plates 31 and 32, cam plate 31, is fixed to the first case member 71, dividing the space inside the case 7 into a first housing space 701 and a second housing space 702. The clutch mechanism 2, the ball cam mechanism 3, and the reduction mechanism 5 are housed in the first housing space 701. The differential gear 12 is housed in the second housing space 702. The other cam plate 32 rotates relative to the first cam plate 31 by the output rotation of the electric motor 4, which is reduced in speed by the reduction mechanism 5.

[0032] Hereinafter, one cam plate 31 will be referred to as the fixed cam plate 31, and the other cam plate 32 will be referred to as the rotating cam plate 32. A bearing 64 that rotatably supports the differential case 122 is positioned between the fixed cam plate 31 and the left cylindrical portion 122d of the differential case 122. The fixed cam plate 31 integrally comprises a disc-shaped disc portion 311, an outer projection 312 (see Figure 3) provided to project radially from the outer diameter end of the disc portion 311, and a cylindrical inner projection 313 provided to project axially toward the clutch mechanism 2 from the inner diameter end of the disc portion 311. The outer projection 312 is fitted into a recess 710 formed in the first case member 71. The rotating cam plate 32 is positioned on the outer circumference of the inner projection 313 of the fixed cam plate 31.

[0033] The ball cam mechanism 3 is configured such that the rotational force of the electric motor 4 causes the fixed cam plate 31 and the rotating cam plate 32 to rotate relative to each other, and the multiple cam balls 33 roll in the multiple rolling grooves 310 and 320 formed in the fixed cam plate 31 and the rotating cam plate 32, respectively, thereby pressing the clutch 20. A more detailed configuration of the ball cam mechanism 3 will be described later.

[0034] A thrust bearing 65 and a pressing member 66 are arranged axially between the rotating cam plate 32 and the clutch 20. The ball cam mechanism 3 presses the clutch 20 via the thrust bearing 65 and the pressing member 66. The pressing member 66 has an annular projection 661 at its inner circumference end, and a return spring 67 is positioned between this annular projection 661 and the connection portion 223 of the clutch hub 22. The return spring 67 is a disc spring and biases the pressing member 66 toward the ball cam mechanism 3. The return spring 67 has oil holes 670 formed at multiple locations in the circumferential direction. The oil holes 670 penetrate the return spring 67 axially.

[0035] The electric motor 4 generates rotational torque corresponding to the current supplied from the control device 40, and rotates the rotating cam plate 32 relative to the fixed cam plate 31 via the reduction mechanism 5. The rotation of the output rotating shaft 41 of the electric motor 4 is reduced by the reduction mechanism 5 and transmitted to the rotating cam plate 32. The ball cam mechanism 3 presses the clutch 20 toward the wall portion 212 of the clutch drum 21 with a pressing force corresponding to the torque generated by the electric motor 4.

[0036] The reduction mechanism 5 includes a reduction gear 51 having a large-diameter gear portion 511 and a small-diameter gear portion 512, and a counter gear 52 having a gear portion 521 that meshes with the small-diameter gear portion 512 of the reduction gear 51 and the rotating cam plate 32 of the ball cam mechanism 3. The large-diameter gear portion 511 of the reduction gear 51 meshes with the output rotating shaft 41 of the electric motor 4. The reduction gear 51 is supported by a support pin 75 attached to the first case member 71. The counter gear 52 has a shaft portion 522 in its center, which is inserted into a support hole 312a formed in the outer projection 312 of the fixed cam plate 31 and is prevented from coming out by a retaining ring 53.

[0037] The multiple outer clutch plates 201 and inner clutch plates 202 of the clutch 20 are lubricated by frictional sliding with lubricating oil 100 (see Figure 2). In this embodiment, the lubricating oil 100 is sealed in the case 7. Leakage of the lubricating oil 100 from the case 7 is prevented by an oil seal 68 positioned between the first case member 71 and the outer joint member 81 of the constant velocity joint 8, and by an oil seal 69 positioned between the second case member 72 and the outer joint member 91 of the constant velocity joint 9. The lubricating oil 100 is mainly contained in the second storage space 702 of the first storage space 701 and second storage space 702, which are partitioned by the fixed cam plate 31.

[0038] As the ring gear 121 rotates together with the differential case 122, the ring gear 121 scrapes up the lubricating oil 100 in the second housing space 702. A portion of the scraped and scattered lubricating oil 100 enters the oil passage 711 (see Figure 2) formed in the first case member 71 and is supplied from the oil passage 711 to the first housing space 701. The opening 711a of the oil passage 711 on the first housing space 701 side is formed near the disc portion 311 of the fixed cam plate 31. As a result, the lubricating oil 100 that flows out from the opening 711a of the oil passage 711 is first supplied between the fixed cam plate 31 and the rotating cam plate 32.

[0039] In this embodiment, due to the characteristic configuration of the retainer 34, which will be described later, lubricating oil 100 can easily flow from between the fixed cam plate 31 and the rotating cam plate 32 to the inner projection 313 side of the fixed cam plate 31. A portion of the lubricating oil 100 that has flowed to the inner projection 313 side of the fixed cam plate 31 flows to the outer circumference of the connecting portion 222 of the clutch hub 22, and flows down the outer surface 222a (see Figure 4) of the connecting portion 222 below the axis of rotation O. Furthermore, it flows from the oil hole 670 of the return spring 67 between the outer cylindrical portion 211 of the clutch drum 21 and the inner cylindrical portion 221 of the clutch hub 22, lubricating the clutch 20. The lubricating oil 100 that has lubricated the clutch 20, and the lubricating oil 100 that has flowed below the first housing space 701 without lubricating the clutch 20, are returned to the second housing space 702 from the discharge hole 311a formed at the lower end of the disc portion 311 of the fixed cam plate 31.

[0040] FIG. 5 is an exploded perspective view of the ball cam mechanism 3. FIG. 6A is a plan view showing the surface on the rotating cam plate 32 side of the fixed cam plate 31. FIG. 6B is a cross-sectional view showing one of the plurality of rolling grooves 310 formed in the fixed cam plate 31 in a cross-section along the circumferential direction of the fixed cam plate 31. FIG. 7A is a plan view showing the surface on the fixed cam plate 31 side of the rotating cam plate 32. FIG. 7B is a cross-sectional view showing one of the plurality of rolling grooves 320 formed in the rotating cam plate 32 in a cross-section along the circumferential direction of the rotating cam plate 32.

[0041] In FIG. 5, the central axis C of the fixed cam plate 31 ３１ , the central axis C of the rotating cam plate 32 ３２ , and the central axis C of the retainer 34 ３４ are indicated by a dashed line. The fixed cam plate 31, the rotating cam plate 32, and the retainer 34 are arranged axially in line such that the central axes C ３１ , C ３２ , C ３４ coincide with the rotation axis O.

[0042] In the disk portion 311 of the fixed cam plate 31, a plurality of rolling grooves 310, discharge holes 311a, and a plurality of bolt holes 311b through which a plurality of bolts 74 (see FIG. 3) are inserted are formed. The plurality of rolling grooves 310 are each formed in an arc shape centered on the central axis C ３１ and are arranged in the circumferential direction of the disk portion 311. Each rolling groove 310 is recessed axially from the opposing surface 311c of the disk portion 311 with respect to the rotating cam plate 32, and is formed such that the depth from the opposing surface 311c gradually increases from the shallowest end 310a, which is one end, to the deepest end 310b, which is the other end.

[0043] On the rotating cam plate 32, a plurality of rolling grooves 320 and an outer peripheral gear portion 321 that meshes with the gear portion 521 of the counter gear 52 are formed. The plurality of rolling grooves 320 are each centered on the central axis C ３２They are formed in an arc shape centered on [the relevant point], and are arranged in the circumferential direction of the rotary cam plate 32. Each rolling groove 320 is recessed axially from the facing surface 32a of the rotary cam plate 32 with respect to the fixed cam plate 31, and is formed such that the depth from the facing surface 32a gradually increases from the shallowest end 320a, which is one end, toward the deepest end 320b, which is the other end.

[0044] The outer peripheral gear portion 321 is composed of a plurality of teeth 321a provided to project in the radial direction of the rotary cam plate 32, and the plurality of teeth 321a are formed at the outer peripheral end of the rotary cam plate 32. The rotary cam plate 32 receives the rotational force of the electric motor 4 when the plurality of teeth 321a mesh with the gear portion 521 of the counter gear 52. Also, because the plurality of teeth 321a are formed on the rotary cam plate 32, it becomes difficult for the lubricating oil 100 to flow circumferentially along the outer peripheral surface of the rotary cam plate 32, and more lubricating oil 100 can be made to easily flow between the fixed cam plate 31 and the rotary cam plate 32.

[0045] In the present embodiment, six rolling grooves 310 and 320 are formed at equal intervals in the circumferential direction on the fixed cam plate 31 and the rotary cam plate 32, respectively. In FIGS. 6A and 7A, the cam balls 33 located at the shallowest ends 310a and 320a of the rolling grooves 310 and 320 are indicated by one-dot chain lines, and the cam balls 33 located at the deepest ends 310b and 320b are indicated by two-dot chain lines.

[0046] The axial interval between the disk portion 311 of the fixed cam plate 31 and the rotary cam plate 32 is widest when the plurality of cam balls 33 are located at the shallowest ends 310a and 320a of the respective rolling grooves 310 and 320, and is narrowest when the plurality of cam balls 33 are located at the deepest ends 310b and 320b of the respective rolling grooves 310 and 320. The cam thrust for axially pressing the clutch 20 is generated when the plurality of cam balls 33 roll from the deepest ends 310b and 320b toward the shallowest ends 310a and 320a.

[0047] Figure 8A is a configuration diagram of the retainer 34 viewed from the axial direction. Figure 8B is a configuration diagram of the retainer 34 viewed from a direction perpendicular to the axial direction. Figure 9A is a configuration diagram of the fixed cam plate 31 and retainer 34 viewed from the rotating cam plate 32 side. Figure 9B is a configuration diagram of the rotating cam plate 32 and retainer 34 viewed from the fixed cam plate 31 side. In Figures 9A and 9B, the rolling grooves 310 and 320 hidden by the retainer 34 are shown with dashed lines.

[0048] The retainer 34 integrally comprises a plurality of retaining portions 341, each having a retaining hole 340 for accommodating a plurality of cam balls 33; a plurality of arc portions 342 between the plurality of retaining portions 341; and a plurality of retaining protrusions 343 provided adjacent to each of the plurality of retaining holes 340. The number of retaining portions 341 and arc portions 342 in the retainer 34 is the same as the number of rolling grooves 310 and 320 in the fixed cam plate 31 and the rotating cam plate 32.

[0049] The retainer 34 is formed in a flat plate shape, except for the portion on which the retaining projections 343 are formed. The multiple retaining projections 343 are provided projecting axially from the fixed cam plate 31 side and the rotating cam plate 32 side of each of the multiple retaining parts 341. A portion of each of the multiple retaining projections 343 is housed in the rolling groove 310 of the fixed cam plate 31 or the rolling groove 320 of the rotating cam plate 32. The retaining projections 343 contribute to the rolling of the cam ball 33 in the rolling grooves 310 and 320 while it is stably held in the retaining hole 340. When the cam ball 33 rolls in the rolling grooves 310 and 320, the surface of the cam ball 33 slides against the retaining projections 343.

[0050] In each of the arc portions 342, an outer concave portion 342a that recesses from the outer diameter side end to the inner diameter side of the cage 34 and an inner concave portion 342b that recesses from the inner diameter side end to the outer diameter side of the cage 34 are formed. These outer concave portion 342a and inner concave portion 342b communicate with the plurality of rolling grooves 310, 320 respectively. That is, as shown in Fig. 9A, when the cage 34 and the fixed cam plate 31 are viewed in the axial direction, a part of the outer concave portion 342a is formed radially inward of the outer diameter side edge portion 310c in the rolling groove 310, and a part of the inner concave portion 342b is formed radially outward of the inner diameter side edge portion 310d in the rolling groove 310. Also, as shown in Fig. 9B, when the cage 34 and the rotating cam plate 32 are viewed in the axial direction, a part of the outer concave portion 342a is formed radially inward of the outer diameter side edge portion 320c in the rolling groove 320, and a part of the inner concave portion 342b is formed radially outward of the inner diameter side edge portion 320d in the rolling groove 320.

[0051] In Fig. 8A, a circumscribed circle Co that circumscribes the outer peripheral ends of the plurality of holding portions 341 around the central axis C ３４ and an inscribed circle Ci that circumscribes the inner peripheral ends of the plurality of holding portions 341 around the central axis C ３４ are shown by a two-dot chain line. Hereinafter, in the radial direction of the cage 34, the portion where the depth of the outer concave portion 342a, that is, the radial distance from the circumscribed circle Co is the largest is referred to as the deepest portion 342c of the outer concave portion 342a. Also, in the radial direction of the cage 34, the portion where the depth of the inner concave portion 342b, that is, the radial distance from the inscribed circle Ci is the largest is referred to as the deepest portion 342d of the inner concave portion 342b.

[0052] The position of the deepest portion 342c of the outer concave portion 342a and the position of the deepest portion 342d of the inner concave portion 342b in each arc portion 342 of the cage 34 are offset in the circumferential direction of the cage 34. That is, the outer concave portion 342a and the inner concave portion 342b are formed so that the deepest portion 342c of the outer concave portion 342a and the deepest portion 342d of the inner concave portion 342b do not line up in the radial direction. Thereby, the strength of the cage 34 is prevented from greatly decreasing in a part of the circumferential direction.

[0053] Because the retainer 34 has an outer recess 342a, the lubricating oil 100 supplied from the oil passage 711 shown in Figure 2 to the first containment space 701 flows from the outer recess 342a into the rolling grooves 310 and 320. Furthermore, because the retainer 34 has an inner recess 342b, the lubricating oil 100 that has flowed into the rolling grooves 310 and 320 is discharged from the inner recess 342b towards the inner projection 313 of the fixed cam plate 31 to the inside of the retainer 34. As a result, the rolling of the cam ball 33 is lubricated by the lubricating oil 100, and the lubricating oil 100 discharged to the inside of the retainer 34 is supplied to the clutch 20 through the above-described path.

[0054] Here, if the outer recess 342a and inner recess 342b were not formed in the retainer 34, the lubricating oil 100 supplied from the oil passage 711 to the first containment space 701 would flow downward along the outer circumferential surface of the retainer 34 between the fixed cam plate 31 and the rotating cam plate 32, and would not be supplied to the rolling grooves 310, 320 or the clutch 20. In other words, in this embodiment, because the outer recess 342a and inner recess 342b are formed in the retainer 34, the lubricating oil 100 is supplied to each part of the drive force transmission device 11, including the clutch 20, via the ball cam mechanism 3.

[0055] In this embodiment, as described above, an outer recess 342a and an inner recess 342b are formed in each of the multiple arc portions 342. However, the embodiment is not limited to this, and it is sufficient if an outer recess 342a and an inner recess 342b are formed in at least one arc portion 342 in the area to which the lubricating oil 100 is supplied. In this case, it is sufficient if the outer recess 342a and the inner recess 342b formed in the at least one arc portion 342 are in communication with at least one of the multiple rolling grooves 310 and 320.

[0056] However, if outer recesses 342a and inner recesses 342b are formed in all arc portions 342, there is no need to pay attention to the angle of the retainer 34 relative to the fixed cam plate 31 and the rotating cam plate 32 when assembling the drive force transmission device 11, thus making the assembly of the drive force transmission device 11 easier and allowing the retainer 34 to be made lighter.

[0057] (Effects of the Embodiment) According to the embodiment described above, it becomes easier to supply lubricating oil 100 to the rolling grooves 310 and 320 of the fixed cam plate 31 and the rotating cam plate 32. In addition, lubricating oil can be circulated radially inside and outside the retainer 34 via the outer recess 342a and inner recess 342b of the retainer 34 and the rolling grooves 310 and 320 of the fixed cam plate 31 and the rotating cam plate 32, and the lubricating oil 100 that has circulated inside and outside the retainer 34 can be supplied to the clutch 20.

[0058] (Modified Example) Figure 10 is a configuration diagram showing a modified example of a retainer 34A. In addition to the components of the retainer 34 described above with reference to Figure 8A, etc., the retainer 34A is provided with a projection 344 at a position adjacent to the outer recess 342a in the circumferential direction of the retainer 34A, which restricts the flow of lubricating oil 100 along the outer peripheral surface 34a of the retainer 34A and facilitates the flow of lubricating oil 100 into the outer recess 342a. The projection 344 protrudes radially outward from the circumscribed circle Co that circumscribes the outer peripheral ends of the plurality of retaining portions 341.

[0059] In the example shown in Figure 10, protrusions 344 are provided on both sides of each of the multiple outer recesses 342a. However, this is not limited to this arrangement; protrusions 344 may be provided only on one side of the outer recesses 342a in the circumferential direction of the retainer 34A. Furthermore, it is not necessary for protrusions 344 to be provided corresponding to all outer recesses 342a; it is sufficient for protrusions 344 to be provided corresponding to at least one outer recess 342a in the area where the lubricating oil 100 is supplied.

[0060] When the retainer 34A according to this modified example is used, the projection 344 dams up the lubricating oil 100, making it easier for the lubricating oil 100 to flow from the outer recess 342a into the rolling grooves 310 and 320.

[0061] (Note) The present invention has been described above based on embodiments and modifications, but these embodiments and modifications do not limit the invention as claimed. It should also be noted that not all combinations of features described in the embodiments are essential for solving the problem of the invention.

[0062] Furthermore, the present invention can be implemented by omitting some components, or by adding or substituting components, without departing from its spirit, and can be modified as appropriate. For example, in the above embodiment, the case in which the lubricating oil 100 in the second housing space 702, which has been scraped up by the ring gear 121, flows into the oil passage 711 of the first case member 71 was described, but the invention is not limited to this, and lubricating oil sucked up from the bottom of the case 7 by an oil pump may be supplied between the fixed cam plate 31 and the rotating cam plate 32. Also, in the above embodiment, the case in which the discharge hole 311a is formed at the lower end of the disc portion 311 of the fixed cam plate 31 was described, but the invention is not limited to this, and for example, the discharge hole 311a may be formed at a position higher than the static oil level, so that the lubricating oil scraped up by the rotation of the clutch drum 21 and the clutch hub 22 is discharged from the discharge hole 311a.

[0063] 100... Lubricating oil 11... Drive force transmission device 20... Clutch 3... Ball cam mechanism 31... Fixed cam plate 310... Rolling groove 32... Rotating cam plate 320... Rolling groove 321a... Tooth 33... Cam ball 34, 34A... Retainer 340... Retaining hole 341... Retaining part 342... Arc part 342a... Outer recess 342b... Inner recess 342c... Deepest part 342d... Deepest part 344... Projection 4... Electric motor (rotary actuator)

Claims

1. A drive force transmission device comprising: a clutch whose intermittent state of driving force changes when pressed in the axial direction; a ball cam mechanism that presses the clutch in the axial direction; and a rotary actuator that operates the ball cam mechanism, wherein the ball cam mechanism has a pair of cam plates facing each other, a plurality of cam balls disposed between the pair of cam plates, and an annular retainer that holds the plurality of cam balls, and the rotational force of the rotary actuator causes the pair of cam plates to rotate relative to each other, thereby pressing the clutch by the plurality of cam balls rolling in a plurality of rolling grooves formed in each of the pair of cam plates, wherein the retainer has a plurality of retaining parts, each having a retaining hole for accommodating the plurality of cam balls, and a plurality of arc parts between the plurality of retaining parts, wherein an outer recess that recesses inward from the outer diameter end of the retainer is formed in at least one of the plurality of arc parts, and the outer recess communicates with at least one of the plurality of rolling grooves of the pair of cam plates.

2. The drive force transmission device according to claim 1, wherein at least one of the plurality of arc portions has an inner recess formed therein that recesses from the inner diameter end of the retainer toward the outer diameter, and the inner recess communicates with at least one of the plurality of rolling grooves of the pair of cam plates together with the outer recess.

3. The drive force transmission device according to claim 2, wherein the position of the deepest part of the outer recess and the position of the deepest part of the inner recess are offset in the circumferential direction of the retainer.

4. The drive force transmission device according to claim 2 or 3, wherein lubricating oil that has flowed into the inside of the retainer through the outer recess and the inner recess is supplied to the clutch.

5. The drive force transmission device according to claim 1, wherein the rotary actuator is an electric motor that rotates the pair of cam plates relative to each other, and a plurality of teeth that receive the rotational force of the electric motor are formed radially protruding from at least one of the outer peripheral ends of the pair of cam plates.

6. The drive force transmission device according to claim 1, wherein a projection is provided in the circumferential direction of the retainer at a position adjacent to the outer recess, which restricts the flow of lubricating oil along the outer surface of the retainer and facilitates the flow of lubricating oil into the outer recess.

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