Wet friction disc and friction engagement device

Abstract

The present invention provides a wet friction disc and a friction engagement device. The wet friction disc (1) includes a friction surface and lubrication grooves, through which lubricant supplied to the friction surface flows. The lubrication grooves have a plurality of circumferential groove portions extending in a circumferential direction and a plurality of intersecting groove portions extending in a direction intersecting the circumferential direction. At least one circumferential groove portion has a through hole extending through the wet friction disc between an opposing surface facing a mating member and a surface on the opposite side in the axial direction.

Description

Technical Field

[0001] This invention relates to wet friction discs and friction engagement devices. Background Technology

[0002] A wet friction disc, sliding on mating components in the presence of lubricant, is used in vehicles, for example in clutch and braking systems. The clutch transmits torque between rotating components of a drive system, and the braking system brakes the rotation of these components. For example, Japanese Unexamined Patent Application Publication 2016-211713 (JP2016-211713A) discloses a device comprising an inner and outer plate as a wet friction disc, capable of switching between a frictionally engaged state and a non-frictionally engaged state in the presence of lubricant. This device brakes the rotation of a shaft relative to a housing component. Lubricant is used to reduce frictional heat generated between the sliding inner and outer plates, and to reduce wear on these plates.

[0003] From the perspective of improving responsiveness, at the moment of switching between a non-frictional engagement state and a frictional engagement state, as mentioned above, the clutch and brake devices, where the inner and outer plates are lubricated, need to rapidly discharge lubricating oil from 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 from 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 from between the inner and outer plates to mitigate the decrease in responsiveness caused by the damping torque due to the viscosity of the lubricating oil between these plates.

[0004] To meet this requirement, the device disclosed in JP2016-211713A has lubrication grooves provided in the surface of the inner plate facing the outer plate, the inner plate rotating integrally with the shaft being input to rotate. The lubrication grooves are used to allow lubricating oil to leave from between the inner plate and the outer plate toward the outer periphery by the centrifugal force applied when the inner plate rotates. Here, the lubrication grooves described in JP2016-211713A are arranged in a grid pattern at an angle relative to both the radial and circumferential directions of the inner plate.

[0005] Figure 12 This is a schematic diagram showing the flow of lubricating oil when the lubrication grooves are arranged in a grid pattern similar to that described in JP2016-211713A within the inner plate. Figure 12 In the diagram, larger arrows indicate areas where lubricating oil flows at a higher flow rate. 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 rotates in an inclined direction, which is directed towards the outer periphery (i.e., the upper side of the figure) and appropriately oriented towards the opposite side of 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 with the centrifugal force exerted by the rotation of the inner plate 9 acts in the direction along the inclined direction, and the lubricating oil is subjected to this force acting in the inclined direction. However, the lubricating oil flowing towards the intersections in the lattice pattern of the lubrication grooves 91 impacts the corners 921 of the bosses 92 defined by the lubrication grooves 91 of the inner plate 9, and some of the lubricating oil branches towards 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 towards the outer periphery.

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

[0007] However, when the circumferential groove is provided along the entire circumference, the lubricating oil flowing through the circumferential groove in the circumferential direction cannot be smoothly discharged towards the outer periphery unless specific means are used. Therefore, from the perspective of effectively discharging the lubricating oil existing between the inner and outer plates towards the outer periphery, there is room for improvement. Summary of the Invention

[0008] The present invention provides a wet friction disc and a friction engagement device, which can more effectively discharge lubricant.

[0009] A wet friction disc according to a first aspect of the invention comprises: a friction surface that frictionally slides on a mating member, the mating member being configured to face the wet friction disc in an axial direction; and a lubrication groove disposed in an opposing surface facing the mating member, through which lubricant supplied to the friction surface flows. The lubrication groove has a plurality of circumferential groove portions and a plurality of intersecting groove portions, the plurality of circumferential groove portions extending in a circumferential direction, and the plurality of intersecting groove portions extending in a direction intersecting the circumferential direction. At least one of the plurality of circumferential groove portions has a through-hole extending through the wet friction disc between the opposing surface and the surface on the opposite side in the axial direction.

[0010] A friction engagement device according to a second aspect of the invention comprises: a wet friction disc according to a first aspect of the invention; a mating member disposed facing the wet friction disc in an axial direction; and a magnetic coil disposed adjacent to the wet friction disc and the mating member in the axial direction. Each of the wet friction disc and the mating member is made of a soft magnetic material and forms a magnetic circuit for generating a magnetic flux when an electric current is applied to the magnetic coil. The magnetic circuit is configured to have a pair of first magnetic circuit portions and a pair of second magnetic circuit portions, the pair of first magnetic circuit portions passing through the wet friction disc and the mating member in the axial direction, and the pair of first magnetic circuit portions being disposed at positions spaced apart from each other in a radial direction, the pair of second magnetic circuit portions connecting the pair of first magnetic circuit portions to each other at both ends. A through-hole is disposed in the region between the pair of first magnetic circuit portions in the radial direction.

[0011] The present invention, having these aspects, can provide a wet friction disc and friction engagement device that can more effectively discharge lubricant. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals refer to like elements, and wherein:

[0013] Figure 1 This is a schematic diagram of the braking device in the first embodiment;

[0014] Figure 2 This is an enlarged cross-sectional view of the braking mechanism surrounding the braking device in the first embodiment;

[0015] Figure 3 This is an enlarged cross-sectional view of the braking mechanism surrounding the braking device when the magnetic coil carries current in the first embodiment;

[0016] Figure 4 This is a front view of the armature as a wet friction disc in the first embodiment;

[0017] Figure 5 This is an enlarged front view showing a portion of the armature in the first embodiment;

[0018] Figure 6 It was observed along the direction of the arrow. Figure 5 View of section VI-VI;

[0019] 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;

[0020] Figure 8This is a front view of the outer panel in the first embodiment;

[0021] Figure 9 This is a cross-sectional view showing the overall structure of the clutch device in the second embodiment;

[0022] Figure 10 It revolves around Figure 9 An enlarged view of the pilot clutch;

[0023] Figure 11 This is a front view of the pilot outer plate, which serves as the wet friction disc, and an enlarged view of a portion of the pilot outer plate in the second embodiment; and

[0024] Figure 12 This is a schematic diagram showing the flow of lubricating oil through conventional lubrication grooves. Detailed Implementation

[0025] First Embodiment

[0026] Reference Figures 1 to 8 The embodiments of the present invention will be described below. The embodiments described below are intended to illustrate specific examples suitable for carrying out the present invention. While some parts of these embodiments specifically illustrate various technically preferred aspects, the scope of the present invention is not limited to these specific aspects.

[0027] Braking device 10

[0028] The braking device 10, which is a friction engagement device including the wet friction disc 1 in this embodiment, will be described. Hereinafter, the direction of extension of the central axis of the wet friction disc 1 (i.e., the armature 5, which will be described later) 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.

[0029] 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 (described later) surrounding the braking device 10. Figure 3 This is an enlarged cross-sectional view of the braking mechanism 4 surrounding the braking device 10 when the magnetic coil 42 carries current.

[0030] The braking device 10 is configured to brake the rotation of the shaft 3 when the braking mechanism 4 is activated. The braking mechanism 10 includes the housing member 2, the shaft 3, and the braking mechanism 4.

[0031] 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 component 21, an annular wall 22, a large-diameter tubular component 23, and a flange 24. The bottom wall 20 has a planar shape extending in a direction orthogonal to the axial direction and closes one end of the small-diameter tubular component 21 in the axial direction. The small-diameter tubular component 21 has a tubular shape extending in the axial direction. The annular wall 22 has an annular shape, extending outwards from one end of the small-diameter tubular component 21 on the side opposite to the side where the bottom wall 20 is located.

[0032] A large-diameter tubular component 23 extends from the outer periphery of the annular wall 22 toward the opposite side of the side where the small-diameter tubular component 21 is located in the axial direction, and has a tubular shape with an inner and outer diameter larger than that of the small-diameter tubular component 21. An opening is formed on the opposite side of the large-diameter tubular component 23 to the side where the annular wall 22 is located. The inner circumferential surface of the large-diameter tubular component 23 has internal splines 231, which are formed at multiple locations in the circumferential direction and extend in the axial direction. The internal splines 231 engage with the outer plate 43, which will be described later, via splines.

[0033] The flange 24 is formed to extend from one end of the large-diameter tubular component 23 on the open side 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 using bolts. This mounting cover is, for example, a gearbox housing. The shaft 3 is rotatably supported on the inner periphery of the small-diameter tubular component 21 by bearing 12.

[0034] Shaft 3 comprises, from one end in the axial direction, a small-diameter shaft portion 31, a medium-diameter shaft portion 32, and a large-diameter shaft portion 33 in sequence. Bearing 12 is mounted on the outer peripheral surface of the small-diameter shaft portion 31. The medium-diameter shaft portion 32 has a larger diameter than 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.

[0035] The large-diameter shaft portion 33 has a larger diameter than the medium-diameter shaft portion 32. On the outer periphery of the large-diameter shaft portion 33 at its end on the side 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. The armature 5 is splined into contact with the external spline teeth 331. The external spline teeth 331 are formed at locations in the radial direction facing the internal spline teeth 231 of the housing member 2.

[0036] The braking mechanism 4 is disposed on the outer periphery of the shaft 3 within the receiving space of the housing component 2. The braking mechanism 4 includes a yoke 41, a magnetic coil 42, an outer plate 43, an armature 5, and a retaining ring 44.

[0037] The yoke 41 is formed of a ring-shaped soft magnetic material. The yoke 41 is fitted inside the large-diameter tubular component 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 on the side of the yoke 41 opposite to the annular wall 22 and is recessed from this surface in the axial direction. A magnetic coil 42 is disposed within the mounting recess 411. A portion of the mounting recess 411 in the circumferential direction communicates with a yoke hole 412, which is bored in the axial direction on one side of the annular wall 22, and the wire of the magnetic coil 42 is led out through this yoke hole.

[0038] The magnetic coil 42 is formed, for example, of enameled wire, which is an enamel-coated conductor wound into a loop shape. The magnetic coil 42 is sealed within the mounting recess 41 by a sealing resin 420. The magnetic coil 42 is electrically connected to a lead 421 extending from the sealing resin 420, and an excitation current is supplied through the lead 421.

[0039] Lead 421 is guided to the outside of housing member 2 by passing through rubber cap 11, which fits into an annular wall hole 221 formed in the annular wall 22 of housing member 2. Cap 11 hermetically closes the gap between lead 421 and annular wall hole 221. On the side of yoke 41 and magnetic 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 closer to yoke 41.

[0040] Figure 8 This is a front view of the outer plate 43. The outer plate 43 is formed into a ring shape by a 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 it can move in the axial direction.

[0041] The outer plate 43 has a plurality of slots 432 formed at positions facing the mounting recess 411 of the yoke 41 in the axial direction and extending in the circumferential direction. These slots 432 are used 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 slots 432 extending in the circumferential direction are formed at regular intervals in the circumferential direction.

[0042] Although not shown, microgrooves extending in the circumferential direction are formed in the surface of the outer plate 43 facing the armature 5. The outer plate 43, including these microgrooves, is formed by pressing, and the surface of the outer plate 43 is subjected to nitriding treatment to ensure hardness. The outer plate 43 is configured to face the armature 5 in the axial direction.

[0043] Figure 4This is a front view of armature 5. Figure 5 This is a magnified front view showing a portion of armature 5. Figure 6 It was observed in the direction of the arrow. Figure 5 The view of section VI-VI.

[0044] In this embodiment, the armature 5 serves as a wet friction disc 1, which generates friction between the outer plate 43 and the armature 5. The outer plate 43 is a mating member that frictionally slides on the armature 5. The armature 5 is formed into a ring shape from a soft magnet and has internal teeth 51 on its inner periphery. 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, although the outer plate 43, together with the housing member 2, is constructed as described above to be unable to rotate relative to the vehicle body, the armature 5 is constructed to be able to rotate integrally with the shaft 3. The detailed shape of the armature 5 will be described later.

[0045] 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 in the axial direction and restricts the movement of the armature 5 toward the side away from the yoke 41.

[0046] The braking mechanism 4 brakes the rotation of shaft 3 based on the following principle: When current is applied to electromagnetic coil 42, as... Figure 3 As shown, magnetic flux is generated in a toroidal magnetic circuit 14, which passes through a yoke 41, an outer plate 43, and an armature 5 made of a soft magnetic material. Specifically, the magnetic circuit 14 has a pair of first magnetic circuit portions 141 and a pair of second magnetic circuit portions 142. The pair of first magnetic circuit portions 141 pass through the armature 5 and the outer plate 43 in the axial direction and are formed at positions spaced apart from each other in the radial direction. The pair of second magnetic circuit portions 142 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 the armature 5 are magnetically attracted to the yoke 41, such that the yoke 41, the outer plate 43, and the armature 5 are stacked on top of each other in the axial direction. As a result, the armature 5 and the outer plate 43 are frictionally engaged with each other in the circumferential direction, thereby braking the rotation of the shaft 3.

[0047] The lubricant is guided into the receiving space of the housing member 2. With the housing member 2 fastened to the fixed cover attached to the vehicle body at the flange 24, the receiving space within the housing member 2 is airtightly closed. For example, the lubricant is transmission fluid, and when the shaft 3 is in a non-rotating state, it is guided to a height near the axis of rotation of the shaft 3. The lubricant lubricates the braking mechanism 4, etc.

[0048] Detailed shape of armature 5

[0049] Next, we will use Figures 4 to 6 The armature 5 is described in detail below. The armature 5 has a lubrication groove 53 formed in the opposing surface 52 facing the outer plate 43, through which lubricant flows.

[0050] The armature 5 has a plurality of bosses 54, which are at least partially defined by lubrication grooves 53 and protrude toward the outer plate 43 in the axial direction compared with the lubrication grooves 53. Most of the bosses 54 have a quadrilateral shape, but those bosses 54 adjacent to the inner periphery of the armature 5 have a shape that extends along the inner periphery of the armature 5.

[0051] The surface of the boss 54 on one side of the outer plate 43 forms a friction surface 521 that slides frictionally on 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, wherein a lubricant is present between the friction surface 521 and the outer plate 43. 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 of forming a diamond-like carbon (DLC) film, which has 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.

[0052] The lubrication groove 53 includes: a grid groove 533 having a grid pattern and each having a plurality of first circumferential groove portions 531a and a plurality of first intersecting groove portions 532a, the plurality of first circumferential groove portions 531a having an arcuate shape and the plurality of first intersecting groove portions 532a extending in a direction intersecting the first circumferential groove portions 531a; and a second circumferential groove portion 531b and a second intersecting groove portion 532b defining the forming area of ​​each grid 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 the corresponding longitudinal direction of these cross groove portions and in 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.

[0053] The second circumferential groove portion 531b is formed along the entire circumference of the armature 5 at the central portion of the armature 5 in the radial direction between the inner and outer circumferential ends. The second circumferential groove portion 531b has a larger flow channel cross-sectional area compared to 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 and the width of the lubrication groove 53.

[0054] 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 has a larger groove width in the radial direction compared to the first circumferential groove portion 531a. The groove width of the second circumferential groove portion 531b is five times or more than the groove width of the first circumferential groove portion 531a. Therefore, the cross-sectional area of ​​the flow channel of the second circumferential groove portion 531b orthogonal to the circumferential direction is five times or more than 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 a position facing the slot 432 of the outer plate 43 in the axial direction. Figures 1 to 3 In the text, the portion of the lubrication groove 53 other than the second circumferential groove portion 531b is omitted.

[0055] The second cross groove portion 532b is formed at 12 positions at regular intervals in the circumferential direction. The second cross groove portion 532b is formed from the inner peripheral end to the outer peripheral end of the armature 5, and has a larger flow channel cross-sectional area compared with the first cross groove portion 532a. Figure 6 As shown, the second cross groove portion 532b is formed as a wider and deeper groove than the first cross groove portion 532a. In this embodiment, the depth of the second cross groove portion 532b is twice or more than the depth of the first cross groove portion 532a. The width of the second cross groove portion 532b is five or more than the width of the first cross groove portion 532a. Therefore, the cross-sectional area of ​​the flow channel of the second cross groove portion 532b is ten or more than the cross-sectional area of ​​the flow channel of the first cross groove portion 532a.

[0056] Each of the first cross groove portion 532a and the second cross groove portion 532b is formed to be inclined relative to the radial direction, such that the region of the cross groove portion further away on the outer peripheral side is positioned further away on the opposite side 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 opposite side of the rotation direction R increases toward the outer peripheral side.

[0057] Grid grooves 533 are formed in multiple regions of the opposing surface 52 surrounded by a second circumferential groove portion 531b and second intersecting groove portions 532b disposed at 12 locations. Each grid groove 533 has a first circumferential groove portion 531a and a first intersecting groove portion 532a, the first circumferential groove portion being spaced apart in the radial direction and the first intersecting groove portion being spaced apart in the circumferential direction.

[0058] like Figure 5 As shown, each first circumferential groove portion 531a has an arcuate shape in the circumferential direction, thereby connecting 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 peripheral side of the second circumferential groove portion 531b form from the second circumferential groove portion 531b toward the outer peripheral edge of the armature 5. Those first intersecting groove portions 532a included in the grid grooves 533 formed on the inner peripheral side of the second circumferential groove portion 531b form from the second circumferential groove portion 531b toward the point in front of the boss 54, which are formed along the inner peripheral edge of the armature 5 at the inner peripheral 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 continuous with one of the first intersecting groove portions 532a of the grid groove 533 formed on the outer peripheral side of the second circumferential groove portion 531b.

[0059] In the following text, each region between adjacent second intersecting groove portions 532b in the circumferential direction will be referred to as segment 55. Since the second intersecting groove portions 532b are formed at regular intervals in the circumferential direction as described above, the segment 55 defined by the second intersecting groove portions 532b is formed at 12 positions in the circumferential direction.

[0060] The 12 segments 55 include three types of segments 55, which differ from each other in their radial position within the first circumferential groove portion 531a. These three types of segments 55 will be referred to as the first segment 551, the second segment 552, and the third segment 553.

[0061] In this embodiment, the segments 55 at the 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.

[0062] Exactly, 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 groove width of the first circumferential groove portion 531a of the first segment 551 towards the inner circumferential side. The first circumferential groove portion 531a of the third segment 553 is formed at a position offset from the groove width of the first circumferential groove portion 531a of the second segment 552 towards the inner circumferential side. Furthermore, those first circumferential groove portions 531a of the first segment 551 formed on the inner circumferential side of the first circumferential groove portion 531a of the third segment 553 are formed at a position offset from the first circumferential groove portion 531a of the third segment 553 towards the inner circumferential side by a certain groove width, which is slightly larger than the groove width of the first circumferential groove portion 531a of the third segment 553.

[0063] Therefore, a pair of first circumferential groove portions 531a, located on each side of any second intersecting groove portion 532b in the circumferential direction, are positioned in a position 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 one of the bosses 54, and the groove width of the first circumferential groove portion 531a adjacent to the boss 54 is completely accommodated within the range in the radial direction spanned by the boss 54. In other words, the area defined by the circumferential extension of the first circumferential groove portion 531a formed in any segment 55, i.e. Figure 5 The shaded area in the image passes radially through the boss 54 in the segment 55 adjacent to that segment 55.

[0064] 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 531b. In this embodiment, a through-hole 56 is formed in each segment 55 and is formed to open in the second circumferential groove 531b. As described above, the second circumferential groove 531b is a portion that faces the slot 432 of the outer plate 43 and is located in the radial direction between a pair of first magnetic circuit portions 141. If these through-holes 56 are formed to open in the second circumferential groove 531b, the increase in magnetic reluctance of the magnetic circuit 14 at the portion in contact with the outer plate 43 can be mitigated even though the through-holes 56 are formed in the armature 5. Each through hole 56 is located in a second circumferential groove 531b at a position spaced apart from a pair of adjacent second intersecting groove portions 532b in the circumferential direction. In this embodiment, each through hole 56 is located at the central position in the circumferential direction between a pair of adjacent second intersecting groove portions 532b in the circumferential direction.

[0065] Lubricant flow inside lubrication groove 53

[0066] Next, we will use Figure 7 This describes 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 the armature 5.

[0067] First, when the shaft 3 and armature 5 rotate, due to the rotational force and centrifugal force of the armature 5, the lubricant extends from the second circumferential groove portion 531b and the second cross groove portion 532b, which have a relatively large flow channel cross-sectional area, to the entire opposing surface 52 of the armature 5. Therefore, mutual wear is prevented between the friction surface 521 of the armature 5 and the outer plate 53.

[0068] like Figure 7 As shown, most of the lubricant flowing through the circumferential groove 531 travels relative to the armature 5 in the opposite direction to the rotation direction R of the shaft 3 due to inertial force, which attempts to keep the lubricant stationary against the rotation of the armature 5. Most of the lubricant flowing through the cross groove 532 flows towards the outer periphery due to centrifugal force. Some of the lubricant flowing through the circumferential groove 531 is discharged towards the outer periphery of the armature 5 due to the flow of lubricant through the first cross groove 532a and centrifugal force, or reaches the second cross groove 532b and is discharged towards the outer periphery of the armature 5 through the second cross groove 532b.

[0069] Here, the grid groove 533 has a small flow channel cross-sectional area and high resistance to lubricant flow, 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. Therefore, the through hole 56 is configured to open in the second circumferential groove portion 531b, thereby allowing the lubricant in the second circumferential groove portion 531b to be discharged through the through hole 56 toward the side of the armature 5 opposite to the outer plate 43.

[0070] The function and effects of the first embodiment

[0071] In this embodiment, the lubrication groove 53 of the armature 5 includes a circumferential groove portion 531 extending in the circumferential direction and a cross groove portion 532 intersecting the circumferential direction. Therefore, compared with... Figure 12Compared to the lubrication grooves 91, which are formed as a grid pattern inclined in both the radial and circumferential directions, the lubricating oil is less likely to be guided towards the inner circumferential side when the armature 5 rotates, and the lubricating oil through the lubrication grooves 53 can be discharged more effectively towards the outer circumferential side of the armature 5. Here, the lubricant flowing through the circumferential groove portion 531 in the circumferential direction can flow into the cross groove portion 532 and be discharged towards the outer circumferential side of the armature 5 through the cross groove portion 532, but such lubricant cannot be discharged effectively towards the outer circumferential side of the armature 5 compared to the lubricant flowing through the cross groove portion 532. Therefore, in this embodiment, through holes 56 are formed, which extend through the armature 5 between the opposing surface 52 and the surface 57 on the opposite side in the axial direction, to open in at least one circumferential groove portion 531. Therefore, the lubricant flowing through the circumferential groove portion 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 holes 56. Therefore, 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, at the moment of switching between the non-frictional engagement state and the 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.

[0072] Each through-hole 56 opens at one end into a second circumferential groove 531b formed along the entire circumference of the armature 5. Each through-hole 56 opens in the second circumferential groove at a position spaced apart from a pair of adjacent second cross-grooves 532b in the circumferential direction, where the second cross-grooves 532b has a larger flow channel cross-sectional area compared to the first cross-grooves 532a. As described above, the second cross-grooves 532b have a relatively large flow channel cross-sectional area, and the lubricant flowing through the second cross-grooves 532b is smoothly discharged towards the outer periphery of the armature 5. Therefore, the lubricant flowing through the second circumferential groove 531b in the region near the second cross-grooves 532b is smoothly discharged from the second circumferential groove 531b towards the outer periphery of the armature 5, with minimal concern about a reduction in lubricant discharge efficiency. On the other hand, lubricant flowing through the area of ​​the second circumferential groove 531b separated from the second intersecting groove 532b cannot be effectively discharged toward the outer periphery of the armature 5. Therefore, one end of each through-hole 56 is formed at a position separated from a pair of adjacent second intersecting grooves 532b in the circumferential direction, thereby allowing lubricant flowing through the area of ​​the second circumferential groove 531b separated 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, 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, each through-hole 56 is formed at a central position in the circumferential direction between a pair of adjacent second intersecting grooves 532b in the circumferential direction. Therefore, lubricant can be discharged from between the armature 5 and the outer plate 43 even more effectively.

[0073] Furthermore, a through-hole 56 is formed in the radial direction region between the pair of first magnetic circuit portions 141. This can mitigate the increase in magnetic reluctance of the entire magnetic circuit 14 by forming a through-hole 56 extending axially through the armature 5. Specifically, when a 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 thus 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.

[0074] Here, if each axial groove 531 is a continuous groove along the entire circumference, then there is no boss 54 along the entire circumference in the region forming the circumferential groove 531. As a result, the outer plate 43, which frictionally slides on the friction surface 521 of the armature 5, will become irregular over time due to the portions of the outer plate 43 facing the boss 54 and facing the circumferential groove 531. These portions facing the boss wear due to frictional sliding on the friction surface 521 of the boss 54, while these portions facing the circumferential groove do not frictional slide on the friction surface 521 of the boss 54 and therefore do not wear.

[0075] 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 adjacent to one of the bosses 54 in the circumferential direction, while the groove width is fully accommodated within the range spanned by the boss 54 in the radial direction. Therefore, the areas where the bosses 54 are absent can be reduced, allowing for uniform wear on the surface of the outer plate 43 facing the armature 5. As a result, the outer plate 43 is less likely to exhibit surface irregularities as described above.

[0076] 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 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 not continuous along the entire circumferential direction. As a result, the outer plate 43 is less likely to develop surface irregularities, and simultaneously, lubricating oil can spread along the entire circumference through the second circumferential groove portion 531b, thus reducing wear on the armature 5 and the outer plate 43.

[0077] The cross-groove portion 532 includes a first cross-groove portion 532a and a second cross-groove portion 532b, the second cross-groove portion 532b having a larger flow channel cross-sectional area compared to the first cross-groove portion 532a. Therefore, grid grooves 533, each formed by the first circumferential groove portion 531a and the first cross-groove portion 532a, are respectively formed in the region surrounded by the second circumferential groove portion 531b and the second cross-groove portion 532b. A pair of first circumferential groove portions 531a formed on adjacent positions on each side of the second cross-groove portion 532b in the first circumferential groove portion 531a are positioned 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 intersecting groove portion 532a tends to have high resistance to the flow of lubricant, forming the first circumferential groove portion 531a to extend in the circumferential direction in the grid groove 533 can prevent the lubricant from flowing through the grid groove 533 with extreme difficulty.

[0078] The cross groove portion 532 is configured at an angle relative to the radial direction, such that the area of ​​the cross groove portion 532 further away on the outer peripheral side is positioned further away on one side in the circumferential direction. Therefore, when the armature 5 is positioned inside the braking device 10 such that the area of ​​the cross groove portion 532 further away on the outer peripheral side is positioned further away on the opposite side 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 (i.e., a force attempting to keep the lubricant stationary against the rotation of the armature 5) pointing outwards. As a result, the lubricant can be discharged more effectively through the cross groove portion 532.

[0079] For example, as described above, this embodiment can provide a wet friction disc 1 and a braking device 10 that serve as a friction engagement device, capable of discharging lubricant more effectively.

[0080] In this embodiment, the lubrication grooves 53 and bosses 54 formed in the armature 5 can be disposed in the surface of the outer plate 43 facing the armature 5, the outer plate 43 sliding frictionally 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 in which a wet friction disc 1 is used in a clutch device 100 as a friction engagement device. Figure 9 This is a cross-sectional view showing the overall structure of the clutch device 100 in this embodiment. Figure 10 It revolves around Figure 9 Enlarged view of the pilot clutch 8. Figure 11This is a front view of the pilot outer plate 84, which is the wet friction disc 1 in this embodiment, and an enlarged view of a part of the pilot outer plate 84.

[0083] The clutch device 100 of this embodiment is an electronically controlled 4WD coupling (a so-called intelligent torque control coupling (ITCC)(R)) type clutch, and is disposed between the drive shaft and the rear differential device in a four-wheel drive vehicle to allow or interrupt the transmission of rotational force between the drive shaft and the rear differential device. Therefore, the clutch device 100 switches between a four-wheel drive state and a two-wheel drive state. In the four-wheel drive state, the engine's driving force is transmitted to both the front and rear wheels, and in the two-wheel drive state, the engine's driving force is transmitted only to the front wheels. The clutch device 100 of this embodiment includes a housing member 16, an output shaft 15, 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 guided into the housing member 16. The output shaft 15 is rotatably held in the housing member 16 by bearing 17.

[0085] The output shaft 15 is connected to the rear differential assembly via a connector or the like, and transmits the rotational force of the housing member 16 to the rear differential assembly 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 main outer plates 61 and main inner plates 62, the main outer plates being splinedly engaged with housing member 16, and the main inner plates being splinedly engaged on the outer periphery of output shaft 15. Specifically, the main outer plates 61 are mounted on housing member 16 to be axially movable but not rotatable relative to housing member 16, and the main inner plates 62 are mounted on output shaft 15 to be axially movable but not rotatable relative to output shaft 15. The main clutch 6 switches between a frictional engagement state and a non-frictional engagement state by pressing force from cam mechanism 7.

[0087] The cam mechanism 7 has a main cam 71, a pilot cam 72 and a plurality of cam balls 73. The main cam 71 presses the main clutch 6 in the axial direction, the pilot cam 72 can rotate relative to the main cam 71, and the plurality of cam balls 73 are 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 driven axially away from the main clutch 6 by a disc spring 74. 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 flange 72 facing each other have multiple cam grooves 711, 721, wherein the depth in the axial direction decreases as the distance from the circumferential center 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 by the cam ball 73 toward the side away from the pilot cam 72, 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 the stacking direction of the main clutch 6, so that the outer main plate 61 and the inner main plate 62 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 a magnetic coil 81, a yoke 82, a pilot inner plate 83 and a pilot outer plate 84 arranged in a stacked manner, and an armature 85. The magnetic coil 81 generates magnetic flux when an electric current is applied. The yoke 82 holds the magnetic 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 82, the pilot outer plate 84, and the armature 85. The pilot inner plate 83 is splined on the outer periphery of the pilot cam 72, and the pilot outer plate 84 and the armature 85 are splined on 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 located at positions that overlap with the non-magnetic ring 86 in the axial direction to prevent the magnetic flux from short-circuiting without passing through the armature 85.

[0091] When a current is applied to the magnetic 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 and a pair of second magnetic circuit portions 182. The pair of first magnetic circuit portions 181 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. The pair of second magnetic circuit portions 181 connect the pair of first magnetic circuit portions 141 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 applies cam thrust to the main clutch 6, causing the main clutch 6 to engage. 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, the opposing surfaces 841 of each pilot outer plate 84 of the pilot clutch 8 on one side of the pilot inner plate 83 (in the case where the pilot inner plate 83 is positioned adjacent to each other on each side of the pilot outer plate 84, these are the two surfaces of the pilot outer plate) have the same surface as the armature in the first embodiment (see Figure 1). Figure 1 Opposite surfaces (see Figure 5) Figure 4 Reference numeral 52) has the same shape except for the shape of the through hole 847, which will be described later. 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 boss 846 defined by the lubrication groove 843. The surface of the boss 846 on one side of the pilot outer plate 83 forms a friction surface 842, which frictionally slides 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 spline with the housing member 16, but the lubrication groove may also be formed in the external teeth 849. Unless otherwise stated, the construction of the lubrication groove 843 and the boss 846 is the same as that 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 opens in a second circumferential groove 844b. The through hole 847 has an arcuate shape substantially along the entire length of the two adjacent segments 848 in the circumferential direction. Each through hole 847 is formed at a position slightly spaced inward from a pair of second intersecting grooves 845b, which are located on both sides of the through hole 847 in the circumferential direction and adjacent to the through hole 847. The through hole 847 serves to prevent the aforementioned short circuit in the magnetic circuit and to allow lubricating oil to flow out.

[0094] The second embodiment is otherwise identical to the first embodiment. Unless otherwise indicated, the same component names used in the second embodiment as those used in the foregoing embodiments refer to the same components as those used in the foregoing embodiments.

[0095] The function and effects of the second embodiment

[0096] In this embodiment, each through-hole 847 is formed over a wider area of ​​the second circumferential groove 844b to span a second intersecting groove 845b. Therefore, lubricant flowing through the second circumferential groove 844b can be smoothly discharged through the through-hole 847 from between the pilot outer plate 84 and the pilot inner plate 83. Furthermore, this embodiment has the same function and effect as the first embodiment.

[0097] Although in this embodiment, the lubrication groove 843 is provided in the pilot outer plate 84, 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 having 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 features described in the embodiments are necessary for the solution to the problem addressed by the invention.

[0100] Within the spirit and scope of this invention, the invention may be modified as needed by omitting some components or using additional or alternative components, and the invention may be implemented accordingly.

Claims

1. A wet friction disc (1), characterized in that... include: A friction surface that slides frictionally on a mating member, the mating member being configured to face the wet friction disc in the axial direction; as well as A lubrication groove is provided in an opposing surface facing the mating member, and lubricant supplied to the friction surface flows through the lubrication groove, wherein: The lubrication groove has a plurality of circumferential groove portions and a plurality of intersecting groove portions, the plurality of circumferential groove portions extending in the circumferential direction, and the plurality of intersecting groove portions extending in a direction intersecting the circumferential direction. At least one of the plurality of circumferential grooves has a through hole that extends through the wet friction disc between the opposing surfaces and the surfaces on opposite sides of the axial direction. The plurality of circumferential grooves include a plurality of first circumferential grooves having an arc shape and a second circumferential groove provided along the entire circumference; The cross-groove portion includes a plurality of first cross-groove portions and a plurality of second cross-groove portions, wherein the plurality of second cross-groove portions have a larger flow channel cross-sectional area than the plurality of first cross-groove portions; and The through hole is configured to open at a position between a pair of second intersecting grooves that are adjacent to each other in the circumferential direction, at a position spaced apart from the pair of second intersecting grooves, and in the second circumferential groove.

2. The wet friction disc (1) according to claim 1, characterized in that: The through hole is configured to open at the central position in the circumferential direction between a pair of second cross grooves that are adjacent to each other in the circumferential direction.

3. A friction engagement device, characterized in that... include: The wet friction disc (1) according to any one of claims 1 to 2; A matching member, the matching member being configured to face the wet friction disc (1) in the axial direction; as well as A magnetic coil is arranged in the axial direction next to the wet friction disc (1) and the mating member, wherein: Each of the wet friction disc (1) and the matching component is made of a soft magnetic material and forms a magnetic circuit for the magnetic flux, which is generated when current is applied to the magnetic coil. The magnetic circuit is configured to have a pair of first magnetic circuit portions and a pair of second magnetic circuit portions. The pair of first magnetic circuit portions pass through the wet friction disc and the mating member in the axial direction, and are positioned radially spaced apart from each other. The pair of second magnetic circuit portions connect the pair of first magnetic circuit portions to each other at both ends. The through hole is disposed in the region between the pair of first magnetic circuit portions in the radial direction.

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