Wet friction disc

Abstract

A wet-type friction disc (1) includes lubrication grooves and a plurality of land portions defined by the lubrication grooves. The lubrication grooves have a plurality of circumferential groove portions extending in a circumferential direction and having a predetermined groove width in a radial direction, and a plurality of intersecting groove portions extending in a direction intersecting the circumferential direction. At least some of the circumferential groove portions have a circular arc shape such that an end portion in the circumferential direction is positioned adjacent to one of the land portions in the circumferential direction, and such that the groove width is entirely contained within a range in the radial direction spanned by the one land portion.

Description

Technical Field

[0001] This invention relates to a wet friction disc. Background Technology

[0002] A wet friction disc that slides on a mating component in the presence of lubricant is used in vehicles, for example, in clutch devices for transmitting torque between rotating components of a drive system and in braking devices for braking the rotation of rotating components. For example, Japanese Unexamined Patent Application Publication No. 2016-211713 (JP2016-211713A) discloses a device comprising an inner plate and an outer plate as a wet friction disc, and in the presence of lubricant, the inner and outer plates can switch between a state of frictional engagement and a state of non-frictional engagement. The lubricant is used to reduce frictional heat generated between the inner and outer plates as they slide against each other, and to reduce wear on these plates.

[0003] From the perspective of improving responsiveness, when switching between a non-frictional engagement state and a frictional engagement state, the clutch and brake devices that lubricate the inner and outer plates, as described above, need to rapidly discharge lubricating oil between the inner and outer plates. Specifically, when the inner and outer plates switch from a non-frictional engagement state to a frictional engagement state, lubricating oil needs to be rapidly discharged between the inner and outer plates to quickly establish frictional engagement between these plates. When the inner and outer plates switch from a frictional engagement state to a non-frictional engagement state, lubricating oil needs to be rapidly discharged between the inner and outer plates to mitigate the decrease in responsiveness caused by the resistance torque generated by the viscosity of the lubricating oil present between these plates.

[0004] To meet this requirement, the device described in JP 2016-211713 A has lubrication grooves provided in the surface of an inner plate facing the outer plate, which rotates integrally with the shaft being input to rotate. The lubrication grooves are used to discharge lubricating oil from between the inner and outer plates toward the outer periphery by the centrifugal force exerted by the inner plate during rotation. Here, the lubrication grooves described in JP 2016-211713 A are arranged in a grid pattern that is inclined relative to both the radial and circumferential directions of the inner plate. Summary of the Invention

[0005] Figure 12 This is a schematic diagram using arrows to illustrate the flow of lubricating oil when lubrication grooves are arranged in a grid pattern in the inner plate as described in JP 2016-211713 A. Figure 12 In the diagram, areas where lubricating oil flows in with a larger volume are indicated by larger arrows. For example... Figure 12As shown, in the inner plate 9, most of the lubricating oil flowing through the lubrication grooves 91 as the inner plate 9 rotates flows in an inclined direction, which is oriented towards the outer periphery (i.e., the upper side of the drawing) and proportionally towards the side opposite to the rotation direction R of the inner plate 9. This is because the force combining the inertial force of the lubricating oil attempting to remain stationary against the rotation of the inner plate 9 and the centrifugal force exerted by the inner plate 9 during rotation acts along the inclined direction, and the lubricating oil is subjected to this force acting in the inclined direction. However, the lubricating oil flowing to the intersection of the grid pattern lubrication grooves 91 collides with the corner 921 of the platform portion 92 of the inner plate 9 defined by the lubrication grooves 91, and a portion of the lubricating oil is diverted to the inner periphery in the radial direction. Therefore, it may hinder the effective discharge of the lubricating oil present between the inner plate 9 and the outer plate to the outer periphery.

[0006] Here, the lubrication grooves can be easily constructed into a grid pattern using annular circumferential grooves extending in the circumferential direction and intersecting grooves that intersect with these circumferential grooves. This structure can reduce the possibility that lubricating oil may flow towards the inner circumference due to the corners of the collision platform when the inner plate rotates.

[0007] However, when circumferential grooves are provided along the entire circumference, the surface of the outer plate facing the inner plate will develop unevenness over time. This is because the plateau portion of this surface facing the inner plate wears due to frictional sliding on the plateau portion, while the portions of the circumferential groove portion facing the inner plate do not slide on the plateau portion and therefore do not wear. When this surface unevenness occurs, the lubricating oil discharge efficiency may decrease during the transition from a frictional engagement state to a non-frictional engagement state and vice versa, resulting in decreased responsiveness.

[0008] The present invention provides a wet friction disc that can more effectively discharge lubricant toward the outer peripheral side and reduce uneven wear of mating components.

[0009] A wet friction disc according to an aspect of the invention comprises: a lubrication groove disposed in a surface facing a mating member, the mating member being configured to face the wet friction disc in an axial direction, and a lubricant flowing through the lubrication groove and supplied to a friction surface that slides on the mating member; and a plurality of platform portions defined by the lubrication groove, wherein surfaces on one side of the plurality of platform portions in the axial direction constitute the friction surface. The lubrication groove has: a plurality of circumferential groove portions extending in a circumferential direction and having a predetermined groove width in a radial direction; and a plurality of intersecting groove portions extending in a direction intersecting the circumferential direction. At least some of the circumferential groove portions have an arcuate shape such that their ends in the circumferential direction are positioned adjacent to one of the platform portions in the circumferential direction, and such that the groove width is completely contained within the radial range spanned by said one platform portion.

[0010] According to this aspect, the present invention can provide a wet friction disc that can more effectively discharge lubricant toward the outer peripheral side and reduce uneven wear of mating components. Attached Figure Description

[0011] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0012] Figure 1 This is a cross-sectional view of the braking device of the first embodiment;

[0013] Figure 2 This is an enlarged cross-sectional view of the braking mechanism surrounding the braking device in the first embodiment;

[0014] Figure 3 This is an enlarged cross-sectional view of the braking mechanism of the braking device in the first embodiment when the electromagnetic coil carries current.

[0015] Figure 4 This is a front view of the armature serving as the wet friction disc in the first embodiment;

[0016] Figure 5 This is a front view showing a portion of the armature in the first embodiment at close range;

[0017] Figure 6 Seen in the direction of the arrow Figure 5 View of section VI-VI;

[0018] Figure 7 This is a partially enlarged front view of the armature, showing the flow of lubricant in the lubrication groove in the first embodiment;

[0019] Figure 8 This is a front view of the outer panel in the first embodiment;

[0020] Figure 9 This is a cross-sectional view showing the overall structure of the clutch device in the second embodiment;

[0021] Figure 10 yes Figure 9 Enlarged view of the area around the pilot clutch;

[0022] Figure 11 This is a front view of the pilot outer plate, which serves as the wet friction disc in the second embodiment, and an enlarged view of a portion of the pilot outer plate; and

[0023] Figure 12 This is a schematic diagram illustrating the flow of lubricating oil through conventional lubrication grooves. Detailed Implementation

[0024] First Embodiment

[0025] Reference Figures 1 to 8 Embodiments of the present invention are described below. The embodiments described below will be shown as specific examples suitable for carrying out the invention. Although certain parts of the embodiments specifically illustrate various technically preferred items, the scope of the invention is not limited to these specific aspects.

[0026] Braking device 10

[0027] The braking device 10, which is a friction engagement device, will be described below. This braking device 10 includes a wet friction disc 1 according to this embodiment. In the following text, the direction in which the central axis of the wet friction disc 1 (i.e., the armature 5), which will be described later, extends will be referred to as the axial direction. The radial direction of the wet friction disc 1 will be simply referred to as the radial direction, and the circumferential direction of the wet friction disc 1 will be simply referred to as the circumferential direction.

[0028] Figure 1 This is a cross-sectional view of the braking device 10 in this embodiment. Figure 2 This is an enlarged cross-sectional view of the braking mechanism 4 around the braking device 10, which will be described later. Figure 3 This is an enlarged cross-sectional view of the braking mechanism 4 of the braking device 10 when the electromagnetic coil 42 carries current.

[0029] The braking device 10 is configured to brake the rotation of the shaft 3 when the braking mechanism 4 is activated. The braking device 10 includes a housing member 2, a shaft 3, and a braking mechanism 4.

[0030] The housing component 2 is made of a non-magnetic material and is fixed to the vehicle body so as not to rotate relative to the vehicle body. The housing component 2 includes a bottom wall 20, a small-diameter tubular portion 21, an annular wall 22, a large-diameter tubular portion 23, and a flange 24. The bottom wall 20 has a planar shape that expands in a direction orthogonal to the axial direction, and the bottom wall 20 closes one end of the small-diameter tubular portion 21 in the axial direction. The small-diameter tubular portion 21 has a tubular shape that extends in the axial direction. The annular wall 22 has an annular shape and expands outward from the end of the small-diameter tubular portion 21 located on the opposite side of the bottom wall 20.

[0031] A large-diameter tubular portion 23 extends from the outer peripheral edge of the annular wall 22 toward the opposite side in the axial direction to the side where the small-diameter tubular portion 21 is located, and has a tubular shape with inner and outer diameters larger than those of the small-diameter tubular portion 21. An opening is formed on the side of the large-diameter tubular portion 23 opposite to the side where the annular wall 22 is located. The inner peripheral surface of the large-diameter tubular portion 23 has internal spline teeth 231, which are formed at multiple locations in the circumferential direction and extend in the axial direction. The internal spline teeth 231 engage with the outer plate 43, which will be described later, via splines.

[0032] The flange 24 is formed to extend from the open end of the large-diameter tubular portion 23 toward the outer periphery. The flange 24 has a bolt insertion hole 241 for fastening the flange 24 to a mounting cover (not shown) fixed to the vehicle body by bolts. The mounting cover is, for example, a gearbox. The shaft 3 is rotatably supported on the inner periphery of the small-diameter tubular portion 21 by bearing 12.

[0033] Shaft 3 comprises, from its axial end, a small-diameter shaft portion 31, a medium-diameter shaft portion 32, and a large-diameter shaft portion 33. Bearing 12 is mounted on the outer circumferential surface of the small-diameter shaft portion 31. The diameter of the medium-diameter shaft portion 32 is larger than the diameter of the small-diameter shaft portion 31. The medium-diameter shaft portion 32 faces the bearing 12 in the axial direction and is used to position the bearing 12 in the axial direction.

[0034] The diameter of the large-diameter shaft portion 33 is larger than that of the medium-diameter shaft portion 32. At the end of the medium-diameter shaft portion 32, external spline teeth 331 extending in the axial direction are formed at multiple locations in the circumferential direction on the outer periphery of the large-diameter shaft portion 33. The armature 5 is splinedly engaged with the external spline teeth 331. The external spline teeth 331 are formed at locations where the internal spline teeth 231 face the housing member 2 in the radial direction.

[0035] The braking mechanism 4 is disposed in the housing space inside the housing member 2 and on the outer periphery of the shaft 3. The braking mechanism 4 includes a yoke 41, an electromagnetic coil 42, an outer plate 43, an armature 5, and a retaining ring 44.

[0036] The yoke 41 is formed of a ring-shaped soft magnetic material. The yoke 41 is fitted inside the large-diameter tubular portion 23 of the housing member 2 and fastened to the annular wall 22 of the housing member 2 by bolts 13. The yoke 41 has an annular mounting recess 411, which opens in a surface of the yoke 41 on the side opposite to the annular wall 22 and is recessed axially from that surface. An electromagnetic coil 42 is disposed inside the mounting recess 411. A circumferential portion of the mounting recess 411 communicates with a yoke hole 412, which is drilled axially on the side of the annular wall 22, through which the wire of the electromagnetic coil 42 is led out.

[0037] The electromagnetic coil 42 is formed, for example, of enameled wire, which is a wire coated with enamel and wound into a loop shape. The electromagnetic coil 42 is sealed inside the mounting recess 411 by a sealing resin 420. The electromagnetic coil 42 is electrically connected to a lead 421 extending from the sealing resin 420, and is supplied with excitation current through the lead 421.

[0038] Lead wire 421 is led to the outside of housing member 2 by passing through rubber cap 11, which is fitted into an annular wall hole 221 formed in the annular wall 22 of housing member 2. Cap 11 hermetically seals the gap between lead wire 421 and annular wall hole 221. On the side of yoke 41 and electromagnetic coil 42 opposite to annular wall 22 in the axial direction, outer plate 43, armature 5 and retaining ring 44 are arranged sequentially from the side closest to yoke 41.

[0039] Figure 8 This is a front view of the outer plate 43. The outer plate 43 is formed of a ring-shaped soft magnet and has external teeth 431 on its outer periphery. The external teeth 431 spline into contact with the internal spline teeth 231 of the housing member 2. Therefore, the outer plate 43 cannot rotate relative to the housing member 2 but can move in the axial direction.

[0040] The outer plate 43 has a plurality of slits 432 formed at positions facing the mounting recess 411 of the yoke 41 in the axial direction and extending in the circumferential direction. The slits 432 serve to prevent the magnetic flux generated when current is applied to the electromagnetic coil 42 from short-circuiting without passing through the armature 5. In this embodiment, six slits 432 are formed at regular intervals in the circumferential direction and are elongated in the circumferential direction.

[0041] Although not shown, microgrooves extending in the circumferential direction are formed on the surface of the outer plate 43 facing the armature 5. The outer plate 43, including these microgrooves, is formed by pressing, and this surface of the outer plate 43 undergoes nitriding treatment to ensure hardness. The outer plate 43 is positioned to face the armature 5 in the axial direction.

[0042] Figure 4This is the front view of armature 5. Figure 5 This is a front view showing a portion of armature 5 at close range. Figure 6 Seen in the direction of the arrow Figure 5 The view of section VI-VI.

[0043] In this embodiment, the armature 5 serves as a wet friction disc 1 that generates frictional force between the outer plate 43 and the armature 5. The outer plate 43 is a mating member that slides frictionally on the armature 5. The armature 5 is formed of a ring-shaped soft magnet and has internal teeth 51 on its inner circumference. The internal teeth 51 spline-engage with the external spline teeth 331 of the shaft 3. Therefore, the armature 5 cannot rotate relative to the shaft 3 but can move in the axial direction. That is, as described above, although the outer plate 43 together with the housing member 2 is configured not to rotate relative to the vehicle body, the armature 5 is configured to rotate integrally with the shaft 3. The detailed shape of the armature 5 will be described later.

[0044] like Figures 1 to 3 As shown, an annular retaining ring 44 is disposed on the side of the armature 5 opposite to the outer plate 43. The retaining ring 44 is fitted and fixed in a recess formed in the outer spline teeth 331 of the housing member 2. The retaining ring 44 faces the armature 5 axially and inhibits the armature 5 from moving away from the yoke 41.

[0045] The braking mechanism 4 brakes the rotation of shaft 3 based on the following principle: When current is applied to the electromagnetic coil 42, such as... Figure 3 As shown, magnetic flux is generated in the annular magnetic circuit 14 passing through the yoke 41, outer plate 43, and armature 5, all made of soft magnetic material. Specifically, the magnetic circuit 14 has: a pair of first magnetic circuit portions 141 that pass through the armature 5 and outer plate 43 in the axial direction and are formed at positions spaced apart from each other in the radial direction; and a pair of second magnetic circuit portions 142 that connect the first magnetic circuit portions 141 to each other at both ends. Due to the attempt to reduce the magnetic reluctance of the magnetic circuit 14, the outer plate 43 and armature 5 are magnetically attracted to the yoke 41, causing the yoke 41, outer plate 43, and armature 5 to overlap each other in the axial direction. As a result, the armature 5 and outer plate 43 rub against each other in the circumferential direction, thereby braking the rotation of the shaft 3.

[0046] Lubricant is introduced into the receiving space of housing member 2. With housing member 2 fastened to a fixed cover at flange 24 and fixed to the vehicle body, the housing space inside housing member 2 is airtightly sealed. For example, the lubricant is transmission oil, and when shaft 3 is not rotating, the lubricant is introduced horizontally near the axis of rotation of shaft 3. The lubricant lubricates braking mechanism 4, etc.

[0047] Detailed shape of armature 5

[0048] Next, we will use Figures 4 to 6 The armature 5 is described in detail. The armature 5 has a lubrication groove 53 formed in the opposing surface 52 facing the outer plate 43, and lubricant flows through the lubrication groove 53.

[0049] The armature 5 has a plurality of platform portions 54, which are at least partially defined by lubrication grooves 53 and bulge toward the outer plate 43 in the axial direction compared to the lubrication grooves 53. Most of the platform portions 54 have a quadrilateral shape, but those platform portions 54 adjacent to the inner peripheral edge of the armature 5 have a shape that extends along the inner peripheral edge of the armature 5.

[0050] The surface of the platform portion 54 on the side of the outer plate 43 forms a friction surface 521 for frictional sliding on the outer plate 43. With lubricant present between the friction surface 521 and the outer plate 43, the friction surface 521 slides frictionally on the outer plate 43, which is configured to face the friction surface 521 in the axial direction. The friction surface 521 has microgrooves extending in the circumferential direction. The armature 5, including these microgrooves, is formed by pressing, and to ensure hardness, the surface of the armature 5 undergoes a process to form a diamond-like carbon (DLC) film with high hardness. Therefore, at least the hardness of the friction surface 521 is higher than the hardness of the surface of the outer plate 43.

[0051] The lubrication groove 53 includes: a grid pattern of grooves 533, each groove 533 having a plurality of first circumferential groove portions 531a in an arc shape and a plurality of first intersecting groove portions 532a extending in a direction intersecting the first circumferential groove portions 531a; and second circumferential groove portions 531b and second intersecting groove portions 532b, which define the forming area of ​​each groove 533. Both the first circumferential groove portions 531a and the second circumferential groove portions 531b extend in the circumferential direction and have a predetermined groove width in the radial direction. Hereinafter, the first circumferential groove portions 531a and the second circumferential groove portions 531b will be collectively referred to as circumferential groove portions 531. Both the first cross groove portion 532a and the second cross groove portion 532b are formed to extend in a direction intersecting the circumferential direction, and have a predetermined groove width in a direction perpendicular to their respective longitudinal directions and in a direction along the circumferential direction. Hereinafter, the first cross groove portion 532a and the second cross groove portion 532b will be collectively referred to as cross groove portion 532.

[0052] The second circumferential groove portion 531b is formed along the entire circumference of the armature 5 at the central portion in the radial direction between the inner and outer circumferential ends of the armature 5. The flow channel cross-sectional area of ​​the second circumferential groove portion 531b is larger than that of the first circumferential groove portion 531a. Here, the flow channel cross-sectional area of ​​each portion of the lubrication groove 53 is the product of the depth of the lubrication groove 53 and the groove width.

[0053] like Figure 4 As shown, the second circumferential groove portion 531b is formed to have the same depth as the first circumferential groove portion 531a and a larger radial groove width than the first circumferential groove portion 531a. The groove width of the second circumferential groove portion 531b is more than five times the groove width of the first circumferential groove portion 531a. Therefore, the cross-sectional area of ​​the flow channel orthogonal to the circumferential direction of the second circumferential groove portion 531b is more than five times the cross-sectional area of ​​the flow channel of the first circumferential groove portion 531a. Figures 1 to 3 As shown, the second circumferential groove 531b is formed at the position of the slit 432 facing the outer plate 43 in the axial direction. Figures 1 to 3 In the original text, the portion of the lubrication groove 53 other than the second circumferential groove portion 531b is omitted.

[0054] The second cross groove portion 532b is formed at 12 locations at regular intervals in the circumferential direction. The second cross groove portion 532b extends from the inner circumferential end of the armature 5 to the outer circumferential end and has a larger flow channel cross-sectional area than the first cross groove portion 532a. For example... Figure 6 As shown, the second cross groove portion 532b is formed as a groove that is both wider and deeper than the first cross groove portion 532a. In this embodiment, the depth of the second cross groove portion 532b is more than twice the depth of the first cross groove portion 532a. The groove width of the second cross groove portion 532b is more than five times the groove width of the first cross groove portion 532a. Therefore, the flow channel cross-sectional area of ​​the second cross groove portion 532b is more than ten times the flow channel cross-sectional area of ​​the first cross groove portion 532a.

[0055] Both the first cross groove portion 532a and the second cross groove portion 532b are formed to be inclined relative to the radial direction, such that the region of the cross groove portion farther on the outer peripheral side is positioned farther on the side opposite to the rotation direction R of the shaft 3. In this embodiment, the first cross groove portion 532a and the second cross groove portion 532b are curved, such that the amount of movement toward the side opposite to the rotation direction R is greater toward the outer peripheral side.

[0056] The grid grooves 533 are formed in multiple regions of the opposing surface 52, which are surrounded by the second circumferential groove portion 531b and the second cross groove portions 532b provided at 12 locations. Each grid groove 533 has a first circumferential groove portion 531a arranged at intervals in the radial direction and a first cross groove portion 532a arranged at intervals in the circumferential direction.

[0057] like Figure 5 As shown, each first circumferential groove portion 531a has an arcuate shape in the circumferential direction to connect a pair of second intersecting groove portions 532b that are adjacent to each other in the circumferential direction. Those first intersecting groove portions 532a included in the grid grooves 533 formed on the outer circumferential side of the second circumferential groove portion 531b extend from the second circumferential groove portion 531b to the outer circumferential edge of the armature 5. Those first intersecting groove portions 532a included in the grid grooves 533 formed on the inner circumferential side of the second circumferential groove portion 531b extend from the second circumferential groove portion 531b to points other than the platform portion 54, which is formed along the inner circumferential edge of the armature 5 at the inner circumferential end of the armature 5. In this embodiment, any first intersecting groove portion 532a of the grid groove 533 formed on the inner peripheral side of the second circumferential groove portion 531b is smoothly connected to a first intersecting groove portion 532a of the grid groove 533 formed on the outer peripheral side of the second circumferential groove portion 531b.

[0058] In the following text, each region between adjacent second intersecting groove portions 532b in the circumferential direction will be referred to as segment 55. As described above, the second intersecting groove portions 532b are formed at 12 positions at regular intervals in the circumferential direction, so the segment 55 defined by the second intersecting groove portions 532b is formed at 12 positions in the circumferential direction.

[0059] The segments 55 at the 12 locations include three types of patterned segments 55, the first circumferential groove portions 531a of the three types of patterned segments 55 being positioned differently in the radial direction. These three types of patterned segments 55 will be referred to as first segment 551, second segment 552, and third segment 553.

[0060] In this embodiment, the segments 55 at 12 locations are formed by arranging four groups of segments 55 in the circumferential direction. Each group of segments 55 consists of a first segment 551, a second segment 552, and a third segment 553 arranged sequentially in the circumferential direction. Therefore, the first segment 551, the second segment 552, and the third segment 553 are positioned adjacent to each other in the circumferential direction, while the first circumferential groove portion 531a of the first segment 551, the first circumferential groove portion 531a of the second segment 552, and the first circumferential groove portion 531a of the third segment 553 are formed at positions offset from each other in the radial direction.

[0061] Specifically, such as Figure 5 As shown, the first circumferential groove portion 531a of the second segment 552 is formed at a position offset from the first circumferential groove portion 531a of the first segment 551 toward the inner circumferential side by the groove width of the first circumferential groove portion 531a of the first segment 551. The first circumferential groove portion 531a of the third segment 553 is formed at a position offset from the first circumferential groove portion 531a of the second segment 552 toward the inner circumferential side by the groove width of the first circumferential groove portion 531a of the second segment 552. Furthermore, those first circumferential groove portions 531a formed on the inner circumferential side of the first circumferential groove portion 531a of the first segment 551 inside the third segment 553 are formed at positions offset from the first circumferential groove portion 531a of the third segment 553 toward the inner circumferential side by a groove width slightly larger than the groove width of the first circumferential groove portion 531a of the third segment 553.

[0062] Therefore, a pair of first circumferential groove portions 531a provided in a pair of adjacent segments 55 on each side of any second intersecting groove portion 532b in the circumferential direction are positioned at locations completely offset from each other in the radial direction. As a result, the end of any first circumferential groove portion 531a in the circumferential direction is positioned adjacent to a platform portion 54, and the groove width of the first circumferential groove portion 531a adjacent to the platform portion 54 is completely contained within the range in the radial direction spanned by the platform portion 54. In other words, the area defined by extending the first circumferential groove portion 531a formed in any segment 55 in the circumferential direction (i.e., Figure 5 The shaded area in the section 55 passes radially through the platform section 54 in the section 55 adjacent to this section 55.

[0063] The armature 5 has a through hole 56 that extends through the armature 5 between the opposing surface 52 and the surface 57 on the opposite side in the axial direction and opens in the second circumferential groove portion 531b. In this embodiment, a through hole 56 is formed in each segment 55 and is formed to open in the second circumferential groove portion 531b. As described above, the second circumferential groove portion 531b is the portion facing the slit 432 of the outer plate 43 and located in the radial direction between a pair of first magnetic circuit portions 141. Even when the through hole 56 is formed in the armature 5, if these through holes 56 are formed to open in the second circumferential groove portion 531b, the increase in magnetic resistance of the magnetic circuit 14 at the portion contacting the outer plate 43 can be mitigated. The through hole 56 opens in the second circumferential groove portion 531b. Each through hole 56 is located between a pair of second intersecting groove portions 532b that are adjacent to each other in the circumferential direction, and at a position spaced apart from the pair of second intersecting groove portions 532b. In this embodiment, the through holes 56 all open at the central position in the circumferential direction between a pair of second intersecting groove portions 532b that are adjacent to each other in the circumferential direction.

[0064] Flow of lubricating oil inside lubrication groove 53

[0065] Next, we will use Figure 7 Describe how the lubricant flows through the lubrication groove 53 as the shaft 3 rotates. Figure 7 This is a partially enlarged front view of armature 5, showing the flow F of lubricant in lubrication groove 53. Figure 7 The upper side of the paper corresponds to the outer periphery of armature 5.

[0066] First, when the shaft 3 and armature 5 rotate, due to the rotational force and centrifugal force of the armature 5, the lubricant diffuses from the second circumferential groove portion 531b and the second cross groove portion 532b, which have a larger cross-sectional area, to the entire opposing surface 52 of the armature 5. Therefore, wear between the friction surface 521 of the armature 5 and the outer plate 43 is prevented.

[0067] like Figure 7 As shown, due to the inertial force attempting to overcome the rotation of the armature 5 and keep the lubricant stationary, most of the lubricant flowing through the circumferential groove 531 advances relative to the side opposite to the rotation direction R of the armature 5 toward the shaft 3. Most of the lubricant flowing through the cross groove 532 flows toward the outer periphery due to centrifugal force. A portion of the lubricant flowing through the circumferential groove 531 is discharged toward the outer periphery of the armature 5 due to the flow of lubricant flowing through the first cross groove 532a and centrifugal force, or reaches the second cross groove 532b and is discharged toward the outer periphery of the armature 5 through the second cross groove 532b.

[0068] Here, the grid groove 533 has a small flow channel cross-sectional area and a large resistance to the flow of lubricant, while the second circumferential groove portion 531b has a large flow channel cross-sectional area, and the lubricant flows more smoothly through the second circumferential groove portion 531b. Therefore, the through hole 56 is configured to open in the second circumferential groove portion 531b, so that the lubricant in the second circumferential groove portion 531b is discharged towards the side of the armature 5 opposite to the outer plate 43 through the through hole 56.

[0069] The function and effects of the first embodiment

[0070] In this embodiment, the lubrication groove 53 includes: a circumferential groove portion 531, which extends in the circumferential direction and has a predetermined groove width in the radial direction; and a cross groove portion 532, which extends in a direction intersecting the circumferential direction. Therefore, when... Figure 12 Compared to the lattice pattern that forms the lubrication groove 91 at an angle to both the radial and circumferential directions, when the armature 5 rotates, the lubricating oil is less likely to be guided toward the inner circumferential side, and the lubricating oil passing through the lubrication groove 53 can be discharged more effectively toward the outer circumferential side of the armature 5.

[0071] Here, if each circumferential groove 531 is a continuous groove along the entire circumference, then there is no platform portion 54 in the region where the circumferential groove portion 531 is formed. As a result, the outer plate 43, which rubs and slides on the friction surface 521 of the armature 5, develops unevenness over time. This is because the portions of the outer plate 43 facing the platform portion 54 are worn due to rubbing and sliding on the friction surface 521 of the platform portion 54, while the portions facing the circumferential groove portion 531 do not rub and slide on the friction surface 521 of the platform portion 54 and are therefore not worn.

[0072] To avoid this situation, in this embodiment, at least some of the circumferential groove portions 531 have an arcuate shape, such that the ends in the circumferential direction are positioned adjacent to a platform portion 54 in the circumferential direction, and the groove width is completely contained within the range in the radial direction spanned by the platform portion 54. Therefore, the area where the platform portion 54 is absent along the entire circumference can be reduced, allowing for uniform wear of the surface of the outer plate 43 facing the armature 5. As a result, the outer plate 43 is less likely to develop surface irregularities as described above.

[0073] The circumferential groove portion 531 includes a first circumferential groove portion 531a with an arcuate shape and a second circumferential groove portion 531b disposed along the entire circumference. A pair of first circumferential groove portions 531a formed at adjacent positions within the first circumferential groove portion 531a (one of the first circumferential groove portions 531a is on each side of the intersecting groove portion 532 in the circumferential direction) are disposed at positions completely offset from each other in the radial direction. Therefore, the lubrication groove 53 can be formed such that the first circumferential groove portions 531a in the corresponding segment 55 are discontinuous along the entire circumferential direction. As a result, the outer plate 43 is less likely to develop surface irregularities, while lubricating oil can diffuse along the entire circumference through the second circumferential groove portion 531b, thus reducing wear on the armature 5 and the outer plate 43.

[0074] The cross-groove portion 532 includes a first cross-groove portion 532a and a second cross-groove portion 532b, the cross-sectional area of ​​the flow channel of the second cross-groove portion 532b being larger than that of the first cross-groove portion 532a. Therefore, grid grooves 533, each composed of a first circumferential groove portion 531a and a first cross-groove portion 532a, are formed in the regions surrounded by the second circumferential groove portion 531b and the second cross-groove portion 532b, respectively. A pair of first circumferential groove portions 531a formed at adjacent positions within the first circumferential groove portion 531a (one of the first circumferential groove portions 531a is on each side of the second cross-groove portion 532b in the circumferential direction) are positioned at locations completely offset from each other in the radial direction. Therefore, although the grid groove 533 formed by the first circumferential groove portion 531a and the first cross groove portion 532a tends to have a large resistance to the flow of lubricant, the formation of the first circumferential groove portion 531a extending in the circumferential direction in the grid groove 533 can prevent the lubricant from having great difficulty flowing through the grid groove 533.

[0075] The cross groove portion 532 is configured to be inclined relative to the radial direction, such that the region of the cross groove portion 532 that is farther on the outer peripheral side is positioned farther on one side in the circumferential direction. Therefore, when the armature 5 is positioned inside the braking device 10 in an orientation in which the region of the cross groove portion 532 that is farther on the outer peripheral side is positioned farther on one side opposite to the rotation direction R, the lubricant flowing through the cross groove portion 532 is squeezed in the direction along the cross groove portion 532 by a combination of centrifugal force and inertial force toward the outer peripheral side, the inertial force being the force that attempts to overcome the rotation of the armature 5 and keep the lubricant stationary. As a result, the lubricant can be discharged more efficiently through the cross groove portion 532.

[0076] Here, the lubricant flowing through the circumferential groove 531 in the circumferential direction can flow into the cross groove 532 and be discharged towards the outer peripheral side of the armature 5 through the cross groove 532. However, compared with the lubricant flowing through the cross groove 532, this lubricant cannot be effectively discharged towards the outer peripheral side of the armature 5. Therefore, in this embodiment, a through hole 56 extending through the armature 5 between the opposing surface 52 and the surface 57 on the opposite side in the axial direction is formed to open in at least one circumferential groove 531. Therefore, the lubricant flowing through the circumferential groove 531 of the armature 5 in the circumferential direction is discharged towards the side of the armature 5 opposite to the outer plate 43 through the through hole 56. Accordingly, the lubricant flowing through the circumferential groove 531 can be discharged more effectively between the armature 5 and the outer plate 43. As a result, when switching between a non-frictional engagement state and a frictional engagement state, the lubricant between the armature 5 and the outer plate 43 can be discharged quickly, which improves the responsiveness of the braking device 10.

[0077] Through-holes 56 open into a second circumferential groove 531b formed along the entire circumference of the armature 5. Each through-hole 56 is formed to open into the second circumferential groove, and is located between a pair of adjacent second cross-grooves 532b in the circumferential direction, and at a location spaced apart from the pair of second cross-grooves 532b, where the flow channel cross-sectional area is larger than that of the first cross-grooves 532a. Here, as described above, the second cross-grooves 532b have a larger flow channel cross-sectional area, and the lubricant flowing through the second cross-grooves 532b is smoothly discharged toward the outer periphery of the armature 5. Therefore, the lubricant flowing through the region of the second circumferential groove 531b near the second cross-grooves 532b is smoothly discharged from the second circumferential groove 531b toward the outer periphery of the armature 5, with little concern about a decrease in lubricant discharge efficiency. On the other hand, in contrast, the lubricant flowing through the region of the second circumferential groove 531b spaced apart from the second intersecting groove 532b is not effectively discharged toward the outer periphery of the armature 5. Therefore, one end of each through hole 56 is formed at a position spaced apart from a pair of adjacent second intersecting grooves 532b in the circumferential direction, thereby allowing the lubricant flowing through the region of the second circumferential groove 531b spaced apart from the second intersecting groove 532b to be discharged toward the side of the armature 5 opposite to the outer plate 43 through the through hole 56. As a result, the lubricant flowing through the second circumferential groove 531b can be discharged more effectively between the armature 5 and the outer plate 43. In particular, in this embodiment, the through holes 56 are all formed at the central position in the circumferential direction between a pair of adjacent second intersecting grooves 532b in the circumferential direction. Therefore, the lubricant can be discharged even more effectively between the armature 5 and the outer plate 43.

[0078] Furthermore, the through-hole 56 is formed radially in the region between a pair of first magnetic circuit portions 141. This mitigates the increase in magnetic reluctance of the entire magnetic circuit 14 caused by the formation of the through-hole 56 extending axially through the armature 5. Specifically, when the through-hole 56 extending along the first magnetic circuit portion 141 is formed at a portion of the armature 5 that constitutes a part of the first magnetic circuit portion 141, the magnetic reluctance of the first magnetic circuit portion 141 increases, and therefore the magnetic reluctance of the entire magnetic circuit 14 increases. This embodiment avoids this situation. As a result, the decrease in the responsiveness of the braking device 10 caused by the formation of the through-hole 56 can be mitigated.

[0079] As described above, this embodiment can provide a wet friction disc 1 that can more effectively discharge lubricant toward the outer peripheral side and reduce uneven wear of mating components.

[0080] In this embodiment, the lubrication grooves 53 and platform portions 54 formed in the armature 5 can be provided in the surface of the outer plate 43 facing the armature 5, which slides rubbed on the armature 5. In this case, the outer plate 43 serves as a wet friction disc 1.

[0081] Second Embodiment

[0082] This embodiment is an example of a wet friction disc 1 being used as a friction engagement device in a clutch assembly 100. Figure 9 This is a cross-sectional view showing the overall structure of the clutch device 100 in this embodiment. Figure 10 yes Figure 9 Enlarged view of the area around the pilot clutch 8. Figure 11 This is a front view and an enlarged view of the pilot outer plate 84, which is the wet friction disc 1 in this embodiment.

[0083] The clutch device 100 of this embodiment is an electronically controlled four-wheel drive (4WD) coupling (so-called intelligent torque control coupling (ITCC)(R)) type clutch, and is disposed between the drive shaft and the rear differential in a four-wheel drive vehicle to allow or interrupt the transmission of rotational force between the drive shaft and the rear differential. Therefore, the clutch device 100 switches between a four-wheel drive state, in which the engine's drive power is transmitted to both the front and rear wheels, and a two-wheel drive state, in which the engine's drive power is transmitted only to the front wheels. The clutch device 100 of this embodiment includes a housing member 16, an output shaft 15, a main clutch 6, a cam mechanism 7, and a pilot clutch 8.

[0084] The housing member 16 is connected to the drive shaft via a joint or the like, and the rotational force of the drive shaft is input into the housing member 16. The housing member 16 has an opening on one side in the axial direction. Lubricant for lubricating the main clutch 6, cam mechanism 7, pilot clutch 8, etc., is introduced into the housing member 16. The output shaft 15 is rotatably held in the housing member 16 by a bearing 17.

[0085] The output shaft 15 is connected to the rear differential via a connector or the like, and the rotational force of the housing member 16 is transmitted to the rear differential via the main clutch 6. The main clutch 6 is located between the output shaft 15 and the housing member 16.

[0086] The main clutch 6 is formed by alternately stacking a main outer plate 61 splinedly engaged with the housing member 16 and a main inner plate 62 splinedly engaged with the outer periphery of the output shaft 15. Specifically, the main outer plate 61 is mounted on the housing member 16 to be axially movable but not rotatable relative to the housing member 16, and the main inner plate 62 is mounted on the output shaft 15 to be axially movable but not rotatable relative to the output shaft 15. The main clutch 6 switches between a frictional engagement state and a non-frictional engagement state by a pressing force from the cam mechanism 7.

[0087] The cam mechanism 7 includes: a main cam 71 that compresses the main clutch 6 in the axial direction; a pilot cam 72 that is rotatable relative to the main cam 71; and a plurality of cam balls 73 disposed between the main cam 71 and the pilot cam 72.

[0088] The main cam 71 is splinedly engaged with the output shaft 15 and is pushed by the disc spring 74 in a direction away from the main clutch 6 in the axial direction. The pilot cam 72 is splinedly engaged with the pilot inner plate 83, and when the pilot clutch 8 is engaged, the rotational force of the housing member 16 is transmitted to the pilot cam 72 through the pilot clutch 8.

[0089] The surfaces of the main cam 71 and the pilot cam 72 facing each other have a plurality of cam grooves 711, 721, the depth of which in the axial direction decreases from the center in the circumferential direction as the distance from the center in the circumferential direction increases. A cam ball 73 is disposed between the cam groove 721 of the pilot cam 72 and the cam groove 711 of the main cam 71. When the pilot cam 72 rotates relative to the main cam 71, the main cam 71 is pressed toward the side away from the pilot cam 72 by the cam ball 73, and a cam thrust is applied to the main clutch 6 by the main cam 71. This cam thrust compresses the main clutch 6 in its stacking direction, causing the main outer plate 61 and the main inner plate 62 to engage with each other, and the rotational force of the housing member 16 is transmitted to the output shaft 15.

[0090] like Figure 10 As shown, the pilot clutch 8 includes an electromagnetic coil 81, a yoke 82, a pilot inner plate 83 and a pilot outer plate 84 arranged in a stacked configuration, and an armature 85. When current is applied to the electromagnetic coil 81, the electromagnetic coil 81 generates magnetic flux. The yoke 82 holds the electromagnetic coil 81. The yoke 82 is made of a soft magnetic material and forms a magnetic circuit 18 through which the magnetic flux passes. The yoke 82 is provided with a non-magnetic ring 86 made of a non-magnetic material to prevent the magnetic flux from short-circuiting without passing through the pilot inner plate 83, the pilot outer plate 84, and the armature 85. The pilot inner plate 83 is splined to the outer periphery of the pilot cam 72, and the pilot outer plate 84 and the armature 85 are splined to the inner periphery of the housing member 16. The pilot inner plate 83, the pilot outer plate 84, and the armature 85 are made of a soft magnetic material and form the magnetic circuit 18. The inner pilot plate 83 and the outer pilot plate 84 have through holes 831 and 847, which are arranged at positions that overlap with the non-magnetic ring 86 in the axial direction to prevent short circuits of magnetic flux without passing through the armature 85.

[0091] When a current is applied to the electromagnetic coil 81, magnetic flux is generated in the annular magnetic circuit 18 passing through the yoke 82, the inner pilot plate 83, the outer pilot plate 84, and the armature 85, all made of soft magnetic material. Specifically, the magnetic circuit 18 has: a pair of first magnetic circuit portions 181 that pass through the inner pilot plate 83 and the outer pilot plate 84 in the axial direction and are formed at positions spaced apart from each other in the radial direction; and a pair of second magnetic circuit portions 182 that connect the pair of first magnetic circuit portions 181 to each other and are formed in the armature 85 and the yoke 82. Due to the attempt to reduce the magnetic reluctance of the magnetic circuit 18, the inner pilot plate 83, the outer pilot plate 84, and the armature 85 are magnetically attracted toward the yoke 82, such that the yoke 82, the inner pilot plate 83, and the outer pilot plate 84 are stacked on top of each other in the axial direction. Then, the inner pilot plate 83 and the outer pilot plate 84 engage with each other circumferentially, and the rotation of the outer pilot plate 84, which rotates together with the housing member 16, is transmitted to the inner pilot plate 83. When the inner pilot plate 83 rotates, the cam mechanism 7 is activated, and a cam thrust is applied to the main clutch 6, thereby engaging the main clutch 6. Therefore, the rotation of the housing member 16 is transmitted to the output shaft 15.

[0092] In this embodiment, such as Figure 11 As shown, except for the shape of the through hole 847, which will be described later, the opposing surfaces 841 of each pilot outer plate 84 of the pilot clutch 8 on the side of the pilot inner plate 83 (which are the two surfaces of the pilot outer plate 84 when the pilot inner plate 83 is adjacent to each side of the pilot outer plate 84) have the same shape as the armature in the first embodiment (see [reference]). Figure 1 Opposing surfaces (see Figure 5) Figure 4The shape is the same as that of reference numeral 52 in the figure. Specifically, the opposing surface 841 of the pilot outer plate 84 has a lubrication groove 843, which includes a circumferential groove portion 844 and a cross groove portion 845. As in the first embodiment, the lubrication groove 843 includes: a circumferential groove portion 844, which includes a plurality of first circumferential groove portions 844a and a second circumferential groove portion 844b formed along the entire circumference; and a cross groove portion 845, which includes a plurality of first cross groove portions 845a and a plurality of second cross groove portions 845b. The pilot outer plate 84 has a platform portion 846 defined by the lubrication groove 843. The surface of the platform portion 846 on the pilot inner plate 83 side constitutes a friction surface 842 for frictional sliding on the pilot inner plate 83. In this embodiment, the lubrication groove 843 is not formed in the external teeth 849 of the pilot outer plate 84 that splines with the housing member 16, but it may be formed in the external teeth 849. Unless otherwise stated, the construction of the lubrication groove 843 and the platform portion 846 is the same as in the first embodiment.

[0093] The pilot outer plate 84 has a through hole 847 that extends through the pilot outer plate 84 between the opposing surface 841 and the surface 84a on the opposite side in the axial direction, and the through hole 847 opens in a second circumferential groove 844b. The through hole 847 has an arcuate shape along approximately the entire length of two adjacent segments 848 in the circumferential direction. The through holes 847 are formed at positions that are slightly inwardly spaced from a pair of second intersecting grooves 845b located on both sides of the through hole 847 and adjacent to the through hole 847 in the circumferential direction. The through holes 847 serve to prevent short circuits in the magnetic circuit as described above and to allow lubricating oil to flow out.

[0094] The second embodiment is otherwise identical to the first embodiment. Unless otherwise stated, the names of the same constituent elements used in the second embodiment as those used in the foregoing embodiments refer to the same constituent elements as in the previous embodiments.

[0095] The function and effects of the second embodiment

[0096] In this embodiment, the through holes 847 are all formed over a large area of ​​the second circumferential groove portion 844b, thereby spanning the second intersecting groove portion 845b. Therefore, lubricant flowing through the second circumferential groove portion 844b can be smoothly discharged from between the pilot outer plate 84 and the pilot inner plate 83 through the through holes 847. Furthermore, this embodiment has the same function and effect as the first embodiment.

[0097] Although the lubrication groove 843 is provided in the pilot outer plate 84 in this embodiment, the lubrication groove 843 may alternatively be provided in at least one of the pilot inner plate 83, the main inner plate 62, and the main outer plate 61. In this case, the pilot inner plate 83, the main inner plate 62, and the main outer plate 61 with the lubrication groove 843 serve as the wet friction disc 1.

[0098] Remark

[0099] Although the invention has been described above based on embodiments, these embodiments do not limit the invention according to the claims. It should be noted that not all combinations of the features described in the embodiments are necessary for the solution to the problem to be solved by the invention.

[0100] The present invention may be implemented as needed within the scope of its spirit by omitting some components or by using additional or alternative components.

Claims

1. A wet friction disc (1) comprising: a lubrication groove provided in a surface facing a mating member provided to face the wet friction disc in an axial direction and through which a lubricant supplied to a friction surface that frictionally slides on the mating member flows; and a plurality of land portions defined by the lubrication groove and a surface on one side of the plurality of land portions in the axial direction constituting the friction surface, wherein: the lubrication groove has a plurality of circumferential groove portions extending in a circumferential direction and having a predetermined groove width in a radial direction, and a plurality of intersecting groove portions extending in a direction intersecting the circumferential direction; and at least some of the circumferential groove portions have a circular arc shape such that an end portion in the circumferential direction is positioned adjacent to one of the land portions in the circumferential direction and such that the groove width is entirely contained within a range in the radial direction spanned by the one land portion, characterized in that: the circumferential groove portions include a plurality of first circumferential groove portions having a circular arc shape and a second circumferential groove portion extending along an entire circumference; and a pair of the first circumferential groove portions provided at adjacent positions each on one side of the intersecting groove portions in the circumferential direction are provided at a plurality of positions to be entirely offset from each other in the radial direction.

2. The wet friction disc (1) according to claim 1, characterized in that: the intersecting groove portions include a plurality of first intersecting groove portions and second intersecting groove portions having a larger flow passage cross-sectional area than the first intersecting groove portions; and a pair of the first circumferential groove portions provided at adjacent positions each on one side of the second intersecting groove portions in the circumferential direction are provided at a plurality of positions to be entirely offset from each other in the radial direction. the intersecting groove portions are provided to be inclined with respect to the radial direction such that a region farther on an outer circumferential side of the intersecting groove portions is positioned farther on one side in the circumferential direction.

3. Wet friction disc (1) according to any one of claims 1 to 2, characterized in that ​

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