JP2023067526A - wet friction material - Google Patents

Abstract

To provide a wet friction material capable of reducing drag torque.SOLUTION: A wet friction material 10 includes a core plate 11 which is formed in a tabular ring shape, and a friction part 12 which is disposed in a ring shape on a principal surface of the core plate 11. The friction part 12 includes a plurality of segment pieces 13, and a plurality of oil grooves 14 formed between the segment pieces 13. A first piece 131 in which an upper left corner and an upper right corner of a substantially rectangular piece are notched substantially triangular and a lower left corner and a lower right corner are notched substantially rectangular is provided as the segment piece 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to wet friction materials. More particularly, it relates to a wet friction material that is used in the presence of lubricating oil and that can be incorporated into wet clutches, wet brakes, and the like.

Conventionally, wet clutches and wet brakes using wet friction materials have been used for torque transmission, braking, and the like. For example, in automatic transmissions of automobiles, etc., a wet friction material is used in a wet hydraulic clutch.
Inside the wet clutch, multiple sheets of wet friction material and multiple sheets of separator plates are alternately arranged with a small clearance between them. It has a structure that does not transmit. In addition, lubricating oil is supplied into the clutch for the purpose of reducing the friction of the wet friction material during this pressure contact/separation and absorbing the frictional heat associated with the friction.
Inside the clutch during idling, the wet friction material and the separator plate are separated and rotate relative to each other. It is known to produce a torque called drag torque. Since this drag torque consumes unnecessary energy when the clutch is idling, it is desired to reduce it as a measure to reduce fuel consumption, which has been rapidly progressing in recent years. As techniques for reducing the drag torque, techniques disclosed in Patent Documents 1 and 2 below are known.

JP 2005-282648 A Japanese Patent Application Laid-Open No. 2001-295859

In Patent Document 1, regarding the oil groove formed by the gap between the segment pieces, the oil groove in which the inner peripheral opening or the intermediate portion spreads in a bilaterally symmetrical shape and the width from the inner peripheral opening to the outer peripheral opening are disclosed. A wet friction material is disclosed in which substantially uniform oil grooves are mixed in a predetermined ratio. It is disclosed that the adoption of this wet friction material can provide a sufficient drag torque reduction effect even in areas where the amount of lubricating oil is large and where lubricating oil is difficult to escape.
In Patent Document 2, at least one of the opposing end faces of two adjacent segment pieces has a cut portion that is cut inward at the inner peripheral side end and/or the intermediate portion of the opposing end face. , a wet friction material in which an oil groove defined by two opposing end surfaces has a wide portion with a wide groove width formed by a cut portion at an inner peripheral side opening and/or an intermediate portion. It is disclosed that the adoption of this wet friction material makes it possible to obtain a wet friction material having a segment piece shape that is excellent in cooling performance and capable of reducing drag torque.
As disclosed in the above Patent Documents 1 and 2, there are various approaches to reducing drag torque, and drag torque reduction is achieved by selecting the optimum form according to various product requirements. there is For this reason, as measures for reducing fuel consumption, which have been strongly demanded in recent years, more forms of drag torque reduction are required so as to meet various product requirements.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wet friction material that achieves a reduction in drag torque with a form different from the conventional one.

The present invention is as follows.
The invention according to claim 1 is a wet friction material comprising a flat ring-shaped core plate and a friction portion arranged in a ring shape on a main surface of the core plate,
The friction portion includes a plurality of segment pieces and a plurality of oil grooves formed between the segment pieces,
The segment piece includes a first piece having a shape in which the upper left corner and upper right corner of a substantially rectangular piece are cut off into a substantially triangular shape, and the lower left corner and lower right corner of the piece are cut into a substantially rectangular shape. and
The invention according to claim 2 is based on the invention according to claim 1, wherein the segment piece is a substantially quadrilateral piece whose upper left corner and upper right corner are cut off into a substantially triangular shape, and whose lower left corner and lower right corner are substantially triangular. The gist of the invention is that it further comprises a second piece having a triangular cut-out shape.
The invention according to claim 3 is the invention according to claim 2, wherein in the friction portion, the first pieces and the second pieces in the same or different number as the first pieces are arranged on the core plate. The gist is that they are arranged alternately in the circumferential direction.
The invention according to claim 4 is the invention according to claim 3, wherein the first piece and the second piece are arranged alternately one by one in the circumferential direction of the core plate. This is the gist.
The invention according to claim 5 is the invention according to claim 3, wherein a plurality of the first pieces that are continuous in the circumferential direction of the core plate form a first piece group,
A plurality of the second pieces that are continuous in the circumferential direction of the core plate form a second piece group,
The gist is that the first piece group and the second piece group are alternately arranged in the circumferential direction of the core plate.
The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the number of the first pieces is 10% or more and 90% or less of the total number of the segment pieces. is the gist.
The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the wet friction material is rotated in the presence of lubricating oil with the center of the ring shape of the core plate as the center of rotation. When rotated in the circumferential direction,
A gist of the shape of the first piece is that a dam portion is formed in a portion where the lower left corner and the lower right corner are cut off into a substantially rectangular shape so that the lubricating oil runs up onto the surface of the friction portion.
The invention according to claim 8 is the invention according to claim 7, wherein the maximum length of the first piece in the left-right direction is W _P1 , and the left-right direction of the portion cut into a substantially rectangular shape is The gist is that 0.08≦W _D1 /W _P1 ≦0.34, where W _D1 is the length of .
The invention according to claim 9 is the invention according to claim 7 or 8, wherein the first piece has a maximum vertical length H _P1 of the first piece, and is cut into a substantially rectangular shape. The gist is that 0.07≦H _D1 /H _P1 ≦0.4, where H _D1 is the length in the vertical direction.

According to the wet friction material of the present invention, it is possible to reduce the drag torque by using a configuration different from the conventional one.

1 is an overall plan view and a partially enlarged perspective view showing a wet friction material of an embodiment; FIG. It is a top view which shows the 1st piece of embodiment. (a) to (d) are plan views showing another form of the first piece. It is a top view which shows the 2nd piece of embodiment. (a) to (d) are plan views showing another form of the second piece. 1 is a partially enlarged plan view showing a wet friction material of an embodiment (Example 1); FIG. FIG. 11 is a partially enlarged plan view showing a combination of segment pieces in another form (Example 2). FIG. 11 is a partially enlarged plan view showing another combination of segment pieces. FIG. 11 is a partially enlarged plan view showing another combination of segment pieces. FIG. 11 is a partially enlarged plan view showing another combination of segment pieces. FIG. 10 is a partially enlarged plan view showing a combination of segment pieces of a comparative product (comparative example 1); 4 is a graph showing the correlation between the drag torque and the number of revolutions obtained using the wet friction materials of Examples 1 and 2 and Comparative Example 1. FIG.

The present invention will now be described with reference to the drawings.
The remarks herein are intended to be illustrative and illustrative of the embodiments of the invention and are believed to be the most effective and readily comprehensible explanations of the principles and conceptual features of the invention. It is described for the purpose of providing what is available. In this regard, it is not intended to show structural details of the invention beyond a certain degree, which are necessary for a fundamental understanding of the invention, but rather to illustrate some aspects of the invention through the description in conjunction with the drawings. is made clear to those skilled in the art how is actually embodied.

In addition, when describing the planar shape of each part in this specification, it is assumed that it is arranged at the 12 o'clock position on the dial of the watch. That is, for example, when describing a segment piece, it is assumed that the segment piece is placed at the 12 o'clock position on the dial.
Therefore, in a given segment piece, "right" means the direction from the 9 o'clock position to the 3 o'clock position on the watch face, and "left" means the direction from the 3 o'clock position to the 9 o'clock position on the watch face. means Furthermore, "up" means the direction from the 6 o'clock position to the 12 o'clock position on the clock face, and "down" means the direction from the 12 o'clock position to the 6 o'clock position on the clock face. .

A wet friction material 10 of the present invention includes a flat ring-shaped core plate 11 and a friction portion 12 arranged in a ring shape on a main surface 111 of the core plate 11 .
The friction portion 12 includes a plurality of segment pieces 13 and a plurality of oil grooves 14 formed between the segment pieces.
In the wet friction material 10 of the present invention, the segment piece 13 has a shape in which the upper left corner and the upper right corner of the segment piece 13 are cut into a substantially triangular shape, and the lower left corner and the lower right corner are cut into a substantially rectangular shape. (see FIGS. 1 and 6 to 10).

In the wet friction material 10 of the present invention, the segment piece 13 has a shape in which the upper left corner and the upper right corner of the segment piece 13 are cut into a substantially triangular shape, and the lower left corner and the lower right corner are cut out into a substantially triangular shape. (See FIGS. 1, 6, and 8 to 10).
Further, in the wet friction material 10 of the present invention, in the friction portion 12, the first pieces 131 and the second pieces 132 in the same number as or different from the first pieces 131 are alternately arranged in the circumferential direction of the core plate 11. (See FIGS. 1, 6, and 8 to 10).

[1] Core Plate As shown in FIG. 1, the core plate 11 has a flat ring shape. That is, it has a ring shape with a hole in the center of the plate.
The core plate 11 has a rotation center P that is the center of the ring shape. A main surface 111 of the core plate 11 is a surface on which the segment piece 13 is joined to form the friction portion 12 .
The main surface 111 may be provided on only one surface of the core plate 11 or may be provided on both surfaces. That is, the friction portion 12 may be formed only on one surface of the core plate 11 or may be formed on both surfaces of the core plate 11 .

The core plate 11 can be appropriately provided with other necessary configurations in addition to the main surface 111 . Other configurations include, for example, engaging teeth. The engaging teeth can be provided so as to protrude from the inner peripheral surface or the outer peripheral surface of the core plate 11 .
Specifically, as shown in FIG. 1, it can have engagement teeth 113 projecting from the outer peripheral surface 112 . The engaging teeth 113 are arranged so as to be able to mesh with splines arranged to surround the wet friction material 10 from the outside.

The size of the core plate 11 is not limited, nor is the correlation between the outer _diameter and the inner diameter. If the outer diameter with respect to the surface 112) and the inner diameter are R ₂ (inner diameter), the ratio R ₁ /R ₂ between them can be 1 ≤ R ₁ /R ₂ ≤ 10, 1.05≦R ₁ /R ₂ ≦5 and 1.1≦R ₁ /R ₂ ≦3.
When the thickness of the core plate 11 is D (mm), the thickness D is not limited, but can be, for example, 0.1 ≤ D (mm) ≤ 10 mm, and 0.3 ≤ D (mm) ≤ 7, and 0.5≦D (mm)≦5.
The core plate 11 may be made of any material, and examples thereof include various carbon steels (S35C, S55C, etc.), cold-rolled steel plates (SPCC, SPCCT, etc.), low-carbon high-tensile steels (NCH780, etc.), and the like. can be used.

[2] Friction Portion The friction portion 12 includes a segment piece 13 and an oil groove 14, as shown in FIG. Specifically, the friction portion 12 is formed by arranging a plurality of segment pieces 13 in a ring shape with oil grooves 14 interposed therebetween.
The friction portion 12 has the function of adjusting the degree of interlocking between the wet friction material 10 and the mating material (separator plate, etc.) depending on the degree of contact between the wet friction material 10 and the mating material (separator plate, etc.).
That is, the wet friction material 10 has a braking function (braking function) and a torque transmission function with respect to the mating material.
The friction portion 12 may have the same shape or different shapes on the main surface 111 on the front side and the main surface 111 on the back side of the core plate 11 .

(1) Segment Piece The segment piece 13 constitutes the friction portion 12, and its surface is a friction surface.
The segment piece 13 defines an oil groove 14 between adjacent segment pieces 13 . That is, the shape of the oil groove 14 is determined by the outer shape of the segment pieces 13 and the arrangement of the segment pieces 13 .
The number of segment pieces 13 arranged on one main surface 111 of the core plate 11 is not limited, but can be, for example, 10 or more and 100 or less. This number is preferably 15 or more and 90 or less, more preferably 20 or more and 80 or less, and particularly preferably 25 or more and 60 or less.

The configuration of the segment piece 13 is not limited, and for example, a paper body containing base fibers and a filler solidified with a curable resin can be used.
Various synthetic fibers, regenerated fibers, inorganic fibers, natural fibers and the like can be used as base fibers. Specifically, cellulose fibers (pulp), acrylic fibers, aramid fibers and the like are preferable.
Further, as the filler, cashew dust as a friction modifier, graphite and/or molybdenum disulfide as a solid lubricant, diatomaceous earth as an extender pigment, and the like can be used. These may use only 1 type and may use 2 or more types together. Furthermore, a phenolic resin and/or a modified resin thereof can be used as the thermosetting resin.
In addition, the segment piece 13 is usually bonded and fixed to the main surface 111 of the core plate 11, but the method of bonding to the core plate 11 is not limited, and the segment piece 13 is bonded to the core plate 11 via heat sealing, an adhesive, or the like. A method such as sticking (adhesion) can be used.

The wet friction material 10 has a first piece 131 as the segment piece 13 .
Moreover, as shown in FIG. 1, the wet friction material 10 may further include a second piece 132 as the segment piece 13 .
The first piece 131 and the second piece 132 will be described below.

(1-1) First Piece As shown in FIG. 2, the first piece 131 is a substantially rectangular piece whose upper left and upper right corners are cut off into substantially triangular shapes and whose lower left and lower right corners are substantially rectangular. It is a segment piece of cut-out shape.
That is, the first piece 131 has a first upper resection portion 131A as a portion in which the upper left corner and the upper right corner are cut into a substantially triangular shape, and a first lower resection portion as a portion in which the lower left corner and the lower right corner are cut into a substantially rectangular shape. It is a segment piece having a shape having a portion 131B.
The first piece 131 can also be said to be a substantially T-shaped segment piece having first upper cut-off portions 131A on the upper left and upper right, and first lower cut-off portions 131B on the lower left and lower right.

The detailed shape of the first piece 131 is not particularly limited as long as it has a first upper cut-out portion 131A and a first lower cut-out portion 131B.
In the first piece 131, for example, the upper side 131C and the lower side 131D can be curved, more specifically, curved upward so that the curvature corresponds to the distance from the rotation center P.
In order to make the groove width of the oil groove 14 formed between the adjacent segment pieces substantially constant, the first piece 131 has, for example, the left and right sides 131E, and the rotation center P is positioned on the extension line thereof. can be slanted as follows.
The first piece 131 can have a shape with chamfered corners.

In FIG. 2, the left and right first upper resection portions 131A have the same size, and the left and right first lower resection portions 131B have the same size.
The first upper cut portion 131A is not limited to having the same size on the left and right sides, and may have different sizes on the left and right sides.
The first lower resection portion 131B is not limited to having the same size on the left and right sides, and may have different sizes on the left and right sides.

Also, the first piece 131 can be shaped as shown in FIGS. 3(a) to 3(d), for example.
The first piece 131 shown in FIG. 3A has a shape wider in the horizontal direction than the shape shown in FIG.
The first piece 131 shown in FIG. 3(b) has a shape in which the first lower cut portion 131B is enlarged as compared with the shape shown in FIG.
The first piece 131 shown in FIG. 3C has a left-right asymmetrical shape by changing the size of the left and right first lower resection portions 131B compared to the shape shown in FIG.
The first piece 131 shown in FIG. 3D has a shape in which left and right first upper cut portions 131A are enlarged compared to the shape shown in FIG.

In the first piece 131, the size of the first lower cut portion 131B is not limited, but the maximum length of the first piece in the left-right direction is W _P1 and the length of the first lower cut portion 131B in the left-right direction is W _D1. , 0.08≦W _D1 /W _P1 ≦0.34. Within this range, an excellent drag torque reduction effect can be obtained.
W _D1 /W _P1 may further be 0.1≦W _D1 /W _P1 ≦0.3, and may further be 0.15≦W _D1 /W _P1 ≦0.25.

Specifically, the lower limit of the length W _D1 in the horizontal direction of the first lower resection portion 131B can be 1 mm or more. The lower limit of W _D1 may be 1.7 mm or more, and may be 2.5 mm or more.
For _WD1 , the upper limit can be 3.5 mm or less. The upper limit of W _D1 can be further set to 3.2 mm or less, and furthermore can be set to 3 mm or less.

In the first piece 131, the size of the first lower cutout portion 131B is not limited, but the maximum vertical length of the first piece is H _P1 and the vertical length of the first lower cutout portion 131B _{is HD1.} , 0.07≦H _D1 /H _P1 ≦0.4. Within this range, an excellent drag torque reduction effect can be obtained.
H _D1 /H _P1 can further be 0.1≦H _D1 /H _P1 ≦0.35, and further can be 0.15≦H _D1 /H _P1 ≦0.3.

Specifically, the lower limit of the vertical length _HD1 of the first lower cut portion 131B can be 1 mm or more. The lower limit of _HD1 can be 2 mm or more, and can be 3 mm or more.
For _HD1 , the upper limit can be 5 mm or less. The upper limit of W _D1 can be further 4.5 mm or less, and furthermore 4 mm or less.

In the first piece 131, the size of the first upper _cut portion _131A is not limited. Within this range, an excellent drag torque reduction effect can be obtained.
θ ₁ can further be 30 degrees ≤ θ ₁ ≤ 55 degrees, and further can be 40 degrees ≤ θ ₁ ≤ 50 degrees.

In the first piece 131, the size of the first upper cut portion 131A _is not limited _. , 0.07≦H _U1 /H _P1 ≦0.4. Within this range, an excellent drag torque reduction effect can be obtained.
H _U1 /H _P1 can further be 0.1≦W _U1 /W _P1 ≦0.35, and further can be 0.2≦H _U1 /H _P1 ≦0.3.

Specifically, the lower limit of the vertical length _HU1 of the first upper resection portion 131A can be 1 mm or more. The lower limit of _HU1 can be 1.5 mm or more, and can be 2 mm or more.
For _HU1 , the upper limit can be 5 mm or less. The upper limit of _HU1 can further be 4.5 mm or less, and furthermore can be 4 mm or less.

(1-2) Second Piece The second piece 132 is, as shown in FIG. 4, a substantially rectangular piece whose upper left and upper right corners are cut off into substantially triangular shapes, and its lower left and lower right corners are substantially triangular. It is a segment piece of cut-out shape.
That is, the second piece 132 has a second upper resection portion 132A as a portion in which the upper left corner and the upper right corner are cut out in a substantially triangular shape, and a second lower resection portion as a portion in which the lower left corner and the lower right corner are cut out in a substantially triangular shape. It is a segment piece having a shape having a portion 132B.
The second piece 132 can also be said to be a substantially octagonal segment piece having second upper cut-off portions 132A on the upper left and upper right, and second lower cut-off portions 131B on the lower left and lower right.

The detailed shape of the second piece 132 is not particularly limited as long as it has a shape having a second upper cut portion 132A and a second lower cut portion 132B.
The second piece 132 can have, for example, an upper side 132</b>C and a lower side 132</b>D in a curved shape, more specifically, a curved line that bulges upward so that the curvature corresponds to the distance from the rotation center P.
In order to make the groove width of the oil groove 14 formed between the adjacent segment pieces substantially constant, the second piece 132 has, for example, the left and right sides 132E, and the rotation center P is positioned on the extension line thereof. can be slanted as follows.
The second piece 132 can have a shape with chamfered corners.

In FIG. 4, the left and right second upper cutout portions 132A have the same size, and the left and right second lower cutout portions 132B have the same size.
The second upper cut portion 132A is not limited to having the same size on the left and right sides, and may have different sizes on the left and right sides.
The second lower resection portion 132B is not limited to having the same size on the left and right sides, and may have different sizes on the left and right sides.

Also, the second piece 132 can be shaped as shown in FIGS. 5(a) to 5(d), for example.
The second piece 132 shown in FIG. 5A has a shape wider in the horizontal direction than the shape shown in FIG.
The second piece 132 shown in FIG. 5(b) has a shape in which the second lower cut portion 132B is enlarged compared to the shape shown in FIG.
The second piece 132 shown in FIG. 5(c) has a left-right asymmetrical shape by changing the size of the left and right second lower resection portions 132B compared to the shape shown in FIG.
The second piece 132 shown in FIG. 5(d) has a shape in which the left and right second upper cut portions 132A are enlarged compared to the shape shown in FIG.

In the second piece 132, the size of the second lower cutout portion 132B is not limited, but the maximum length in the left-right direction of the second piece is W _P2 , and the length in the left-right direction of the second lower cutout portion 132B is W _D2. , 0.08≦W _D2 /W _P2 ≦0.45. Within this range, a favorable drag torque reduction effect can be obtained.
W _D2 /W _P2 may further be 0.1≦W _D2 /W _P2 ≦0.4, and may further be 0.15≦W _D2 /W _P2 ≦0.3.

Specifically, the lower limit of the length W _D2 of the second lower resection portion 132B in the left-right direction can be 1 mm or more. The lower limit of W _D2 can be 1.7 mm or more, and can be 2.5 mm or more.
For _WD2 , the upper limit can be 5 mm or less. The upper limit of W _D2 may be 4 mm or less, and may be 3.5 mm or less.

In the second piece 132, the size of the second lower cutout portion 132B is not limited, but the maximum vertical length of the second piece is H _P2 and the vertical length of the second lower cutout portion 132B is H _D2. , 0.07≦H _D2 /H _P2 ≦0.4. Within this range, a favorable drag torque reduction effect can be obtained.
H _D2 /H _P2 can further be 0.1≦H _D2 /H _P2 ≦0.35, and further can be 0.15≦H _D2 /H _P2 ≦0.3.

Specifically, the lower limit of the vertical length H _D2 of the second lower resection portion 132B can be 1 mm or more. The lower limit of _HD2 can be 2 mm or more, and can be 3 mm or more.
For _HD2 , the upper limit can be 5 mm or less. The upper limit of W _D2 can be further set to 4.5 mm or less, and can be set to 4 mm or less.

In the second piece 132, the size of the second upper cut portion 132A is not limited, but when the cutting angle with respect to the side edge 132E is _θ2 , 20 degrees ≤ _θ2 ≤ 60 degrees can be satisfied. Within this range, a favorable drag torque reduction effect can be obtained.
θ ₂ can further be 30 degrees ≤ θ ₁ ≤ 55 degrees, and further can be 40 degrees ≤ θ ₂ ≤ 50 degrees.

In the second piece 132, the size of the second upper cut-off portion 132A is not limited, but the maximum vertical length of the second piece is _HP2 , and the vertical length of the second upper cut-off portion 132A _{is HU2.} , 0.07≦H _U2 /H _P2 ≦0.4. Within this range, a favorable drag torque reduction effect can be obtained.
H _U2 /H _P2 can further be 0.1≦W _U2 /W _P2 ≦0.35, and further can be 0.2≦H _U2 /H _P2 ≦0.3.

Specifically, the lower limit of the vertical length _HU2 of the second upper cut portion 132A can be 1 mm or more. The lower limit of _HU2 can be 1.5 mm or more, and can be 2 mm or more.
For _HU2 , the upper limit can be 5 mm or less. The upper limit of _HU2 may further be 4.5 mm or less, and may be 4 mm or less.

(1-3) First Piece and Second Piece The maximum width W _p1 of the first piece 131 and the maximum width W _p2 of the second piece 132 may be different, but are preferably the same.
If they are the same, the shape of the oil grooves 14 formed between the segment pieces can be made uniform, and variation in shape can be suppressed, so that the drag torque can be reduced satisfactorily.

Regarding the first lower cutout portion 131B of the first piece 131 and the second lower cutout portion 132B of the second piece 132, the lengths W _D1 and W _D2 in the horizontal direction and the lengths H _D1 and H _D2 in the vertical direction are They may be different, but are preferably the same.
If they are the same, the shape of the oil grooves 14 formed between the segment pieces can be made uniform, and variation in shape can be suppressed, so that the drag torque can be reduced satisfactorily.

Regarding the first upper resection portion 131A of the first piece 131 and the second upper resection portion 132A of the second piece 132, the cutting angles θ ₁ and θ ₂ and the vertical lengths _HU1 and _HU2 may be different. Good, but preferably the same.
If they are the same, the shape of the oil grooves 14 formed between the segment pieces can be made uniform, and variation in shape can be suppressed, so that the drag torque can be reduced satisfactorily.

(2) Oil Groove The oil groove 14 is a groove that serves as a lubricating oil flow path that is formed as a gap between the two segment pieces 13 by arranging them apart.
In the wet friction material 10, as shown in FIG. 6, each segment piece 13 is arranged apart from each other and has an oil groove 14 as a gap between them.
That is, the oil groove 14 is a through groove that penetrates the wet friction material 10 from the inner peripheral side to the outer peripheral side.

The oil groove 14 can function as a guide for discharging lubricating oil supplied from the inner peripheral side of the wet friction material 10 toward the outer peripheral side.
A plurality of oil grooves 14 corresponding to the number of segment pieces 13 are arranged on the main surface 111 of the core plate 11 .
When all the segment pieces 13 are spaced apart, the number of oil grooves 14 is the same as the number of segment pieces 13 .

When only the first piece 131 or the first piece 131 and the second piece 132 are used as the segment piece 13 , the oil groove 14 is formed at the end of the wet friction material 10 on the inner peripheral side. (see FIG. 6).
That is, the oil groove 14 formed between the adjacent first pieces 131 is widened at the portion between the first lower cut portions 131B, and this portion becomes the oil reservoir groove 141 .
In addition, since the second piece 132 is provided with the second lower cut portion 132B, the oil groove 14 formed between the adjacent second pieces 132 and the adjacent first piece 131 and the second piece The oil groove 14 formed between 132 is also shaped to have an oil reservoir groove 141 .

Since the oil groove 14 having the oil reservoir groove 141 has a shape in which the narrow oil groove 14 continues to the widened oil reservoir groove 141 , the lubricating oil flowing from the oil reservoir groove 141 to the outer peripheral side of the core plate 11 flows. By suppressing the flow, the lubricating oil can be accumulated in the oil reservoir groove 141 .
The lubricating oil stored in the oil reservoir groove 141 rides over the segment piece 13 and onto the surface of the friction portion 12 due to the centrifugal force or the like caused by the rotation of the wet friction material 10 .
Therefore, the oil groove 14 having the oil reservoir groove 141 has the effect of promoting the running of the lubricating oil onto the surface of the friction portion 12 .

When only the first piece 131 or the first piece 131 and the second piece 132 are used as the segment piece 13 , the oil groove 14 is provided with an oil drain groove 142 at the outer peripheral end of the wet friction material 10 . It becomes a shape having (see FIG. 6).
That is, the oil groove 14 formed between the adjacent first pieces 131 is widened at the portion between the first upper cut portions 131A, and this portion becomes the oil drain groove 142. As shown in FIG.
In addition, since the second piece 132 is provided with the second upper cut portion 132A, the oil groove 14 formed between the adjacent second pieces 132 and the adjacent first piece 131 and the second piece The oil groove 14 formed between 132 is also shaped to have an oil drain groove 142 .

Since the oil groove 14 having the oil drain groove 142 has a shape in which the widened oil groove 142 continues to the narrow oil groove 14, the oil drain groove is wide open toward the outer peripheral side of the core plate 11. By promoting the discharge of the lubricating oil from 142, the lubricating oil can be actively discharged.
Therefore, the oil groove 14 having the oil drain groove 142 has the effect of suppressing the stagnation of lubricating oil on the surface of the friction portion 12 and promoting the discharge of the lubricating oil to the outer peripheral side of the core plate 11 .

Although the size of the oil groove 14 is not limited, for example, the width _D1 of the oil groove 14 other than the oil reservoir groove 141 and the oil drain groove 142 is preferably 0.1 mm or more and 10 mm or less, and 0.2 mm or more and 7 mm or less. is more preferable, and 0.5 mm or more and 5 mm or less is particularly preferable.
The maximum width _D2 of the oil reservoir groove 141 is, for example, preferably 2.5 mm or more and 13 mm or less, more preferably 4 mm or more and 12 mm or less, and particularly preferably 5 mm or more and 10 mm or less.
The maximum width _D3 of the oil drain groove 142 is, for example, preferably 2.5 mm or more and 23 mm or less, more preferably 4 mm or more and 17 mm or less, and particularly preferably 5 mm or more and 10 mm or less.

(3) Combination of Segment Pieces As shown in FIG. 7, the segment piece 13 may use only one type of the first piece 131 (see FIG. 7). It is preferred to use a combination of species (see Figures 1, 8, 9 and 10). When the first piece 131 and the second piece 132 are used in combination, an excellent drag torque reduction effect can be obtained.
Note that the segment piece 13 may be a piece having a shape other than the first piece 131 and the second piece 132 .

When using a combination of two types of segment pieces 13, the first pieces 131 and the second pieces 132, a predetermined number of the first pieces 131 and the same number or different number of the second pieces 132 as the first pieces form a core plate. 11 are preferably arranged alternately in the circumferential direction.
As a combination of such segment pieces 13, for example, as shown in FIG. A combination in which one is alternately arranged in each direction can be mentioned.
In addition, as shown in FIG. 9, five first pieces 131 and one second piece 132, which is different from the first pieces 131, are alternately arranged in the circumferential direction of the core plate 11. can be any combination of

When a plurality of first pieces 131 and a plurality of second pieces 132 are combined, a plurality of first pieces 131 continuous in the circumferential direction of the core plate 11 form a first piece group 13A, A plurality of pieces 132 continuous in the circumferential direction of the core plate 11 form a second piece group 13B, and the first piece group 13A and the second piece group 13B are alternately arranged in the circumferential direction of the core plate 11. is preferably provided.
For example, as shown in FIG. 1, three pieces of the first piece 131 that are continuous in the circumferential direction of the core plate 11 form the first piece group 13A, and the second pieces 132 are two pieces different from the first pieces. The pieces are continuous in the circumferential direction of the core plate 11 to form the second piece group 13B. The first piece group 13A and the second piece group 13B are alternately arranged in the circumferential direction of the core plate 11 .
Further, as shown in FIG. 10 , two first pieces 131 that are continuous in the circumferential direction of the core plate 11 form a first piece group 13A, and second pieces 132 are the same number of two pieces as the first pieces 131 . The pieces are continuous in the circumferential direction of the core plate 11 to form the second piece group 13B. The first piece group 13A and the second piece group 13B are alternately arranged in the circumferential direction of the core plate 11 .

When the segment piece 13 is used in combination with the first piece 131 and pieces other than the first piece 131 such as the second piece 132, the number of the first pieces 131 is 10% or more of the total number of the segment pieces 13. It is preferably 90% or less.
Also, when using a combination of the first piece 131 and the second piece 132 as the segment pieces 13, the number of the first pieces 131 should be 50% or more and 90% or less of the total number of the segment pieces 13. is preferred. That is, when the first piece 131 and the second piece 132 are combined, the first piece 131 and the second piece 132 may have the same number of pieces, but the first piece 131 may have the same number of pieces as the second piece 132 . By increasing , it is possible to satisfactorily reduce the drag torque.

[3] Drag Torque Reduction (1) Riding Effect The wet friction material 10 is rotated counterclockwise as shown in FIG. This will be described on the assumption that the
The lubricating oil is supplied to the wet friction material 10 from the inner peripheral side of the core plate 11, receives centrifugal force from the wet friction material 10, and is discharged to the outer peripheral side of the core plate 11 through the oil groove 14. .
More specifically, the lubricating oil flows from the inner peripheral side of the core plate 11 into the oil reservoir groove 141 at the inner peripheral end of the oil groove 14, passes through the oil groove 14, and flows into the outer peripheral end of the oil groove 14. The oil is discharged to the outer peripheral side of the core plate 11 from the oil drain groove 142 at the end.

The oil reservoir groove 141 is defined by a substantially rectangular portion of the first piece 131 cut at the lower left corner and the lower right corner, that is, the first lower cut portion 131B. After passing through 141 , the flow path to the oil drain groove 142 is narrower than the flow path of the oil reservoir groove 141 .
For this reason, the lubricating oil that has flowed into the oil reservoir groove 141 is temporarily prevented from flowing from the inner peripheral side to the outer peripheral side of the core plate 11 by the inner surface of the first lower cut portion 131B forming a dam portion 131F. The oil is dammed up and accumulated in the oil reservoir groove 141 .
When the amount of lubricating oil stored in the oil reservoir groove 141 eventually reaches a level that allows it to ride over the weir portion 131F, it overflows the oil reservoir groove 141 and rides on the surface of the friction portion 12 (as indicated by the thick arrow in FIG. 1). reference).

That is, it can be said that the shape of the first piece 131 is a shape in which a dam portion 131F is formed in the first lower cut portion 131B so that the lubricating oil rides up on the surface of the friction portion 12 .
The lubricating oil that has been run onto the surface of the friction portion 12 by the weir portion 131F is subjected to centrifugal force, so that it moves along the first piece 131 toward the outer periphery in the direction opposite to the rotational direction of the wet friction material 10 (clockwise direction). Move toward (see thick arrows in FIG. 1).
The lubricating oil moving on the first piece 131 reaches the oil drain groove 142 defined by the first upper cut portion 131A, flows into the oil drain groove 142, and flows from the oil drain groove 142 into the wet friction material 10. It is discharged to the outer peripheral side.

Lubricating oil forms an oil film on the surface of the first piece 131 when moving on the first piece 131 .
This oil film has a necessary and sufficient amount to maintain lubrication between the wet friction material 10 and the mating material (e.g., a separator plate) by rapidly spreading the lubricating oil from the oil reservoir groove 141 to the oil drain groove 142 . Formed by lubricating oil.
That is, the first piece 131 has a dam portion 131F formed in the first lower cut portion 131B and a first upper cut portion 131A. It has a run-up effect.
Due to this run-on effect, the lubricating oil present between the wet friction material 10 and the mating material (for example, a separator plate) is kept to a necessary and sufficient amount to maintain lubrication. Co-rotation with the material is suppressed, and drag torque reduction can be achieved.

(2) Effect of Combining First Piece 131 and Second Piece 132 The wet friction material 10 using a combination of the first piece 131 and the second piece 132 will be described.
The second piece 132 has a shape having a second lower cutout portion 132B and a second upper cutout portion 132A. (See the thin arrows in FIG. 1).

Comparing the first lower cutout portion 131B of the first piece 131 and the second lower cutout portion 132B of the second piece 132, the lengths in the horizontal direction W _D1 and W _D2 and the lengths in the vertical direction H _D1 and When H _D2 is substantially the same, the area of the first lower cutout portion 131B is larger than the area of the second lower cutout portion 132B in plan view. , a larger amount of lubricating oil can be stored and a larger amount of lubricating oil can run on the surface of the friction portion 12 as compared with the second lower cut portion 132B.
In other words, both the first piece 131 and the second piece 132 have a run-on effect, but the run-on effect of the first piece 131 causes a larger amount of lubricating oil to rub off than the run-on effect of the second piece 132. It becomes stronger because it can run on the surface of the portion 12 (see the thick arrow in FIG. 1).
Also, the riding effect of the second piece 132 is weaker than that of the first piece 131 (see thin arrows in FIG. 1).

In the wet friction material 10, when the first pieces 131 (first piece group 13A) and the second pieces 132 (second piece group 13B) are alternately arranged in the circumferential direction of the core plate 11, the It is possible to provide both a portion where the first piece 131 has a strong riding effect and a portion where the second piece 132 has a weak riding effect.
In other words, when both the first piece 131 and the second piece 132 are used as the segment pieces 13 of the wet friction material 10, the run-on effect can be uneven.

The drag torque is generated when the wet friction material and the mating material (e.g., separator plate), which are spaced apart and relatively rotated, are linked with each other using the lubricating oil existing around them as an intermediary, and rotate together.
Therefore, in order to reduce the drag torque, the rotation difference between the wet friction material and the mating material, which are relatively rotated, can be used to separate the mating material from the wet friction material, and the force around them, especially the co-rotating force, can be generated. It is preferable to suppress co-rotation of both by shearing the lubricating oil existing in the outer peripheral portion which becomes large.

As described above, the wet friction material 10 using both the first piece 131 and the second piece 132 can form uneven running-up effects. In the wet friction material 10, the amount of lubricating oil that rides on the surface of the friction portion 12 from the oil reservoir groove 141 has many areas where the running effect is strong, and there are few areas where the running effect is weak.
At the portion where the run-on effect is weak, the amount of lubricating oil that rides on the surface of the friction portion 12 is small, and the amount of lubricating oil that mediates the connection with the mating material is small, so a weak force (rotation torque) due to the difference in relative rotation. However, the mating material can be easily peeled off from the wet friction material. When the mating material is torn off from the wet friction material at the portion where the run-on effect is weak, the mating material is likely to be pulled off from the wet friction material at the portion where the run-on effect is strong.
Therefore, in the wet friction material 10 using both the first piece 131 and the second piece 132, when compared with the wet friction material in which the ride-on effect is uniform throughout, unevenness in strength of the run-on effect is intentionally formed. As a result, it is possible to obtain a so-called peeling effect in which the mating material is easily peeled off from the wet friction material by utilizing the difference in relative rotation.

Furthermore, in the wet friction material 10 in which strength and weakness of the run-on effect are formed unevenly, the amount of lubricating oil that moves from the surface of the friction portion 12 to the oil drain groove 142 has many parts with a strong run-on effect, and there are many parts with a weak run-on effect. few.
Since the amount of lubricating oil discharged from the oil drain groove 142 to the outer peripheral side is small at the portion where the run-on effect is weak, the resistance required for shearing the lubricating oil at the outer peripheral portion of the wet friction material 10 is small, and the rotation of the relative rotation is reduced. Even a weak force (rotational torque) due to the difference can shear the lubricating oil.
Therefore, in the wet friction material 10 using both the first piece 131 and the second piece 132, when compared with the wet friction material in which the ride-on effect is uniform as a whole, unevenness in strength of the run-on effect is formed. Therefore, the shear resistance of the lubricating oil in the outer peripheral portion can be suppressed.

As described above, the wet friction material 10 using both the first piece 131 and the second piece 132 can intentionally form unevenness in the strength and weakness of the riding effect.
The wet friction material 10, which is intentionally formed with uneven strength of the riding effect, can obtain a peeling effect from the mating material and can suppress the shearing resistance of the lubricating oil in the outer peripheral portion.
In addition, the wet friction material 10, which is intentionally formed with uneven strength of the riding effect by suppressing the peeling effect and the shear resistance of the lubricating oil, can achieve excellent drag torque reduction.

In the following, the invention is illustrated by examples. Description common to each embodiment will be omitted.
[1] Preparation of wet friction material [Example 1]
The wet friction material 10 (see FIG. 1) of Example 1 includes a core plate 11 and friction portions 12 arranged on the main surface 111 of the core plate 11 (both sides of the main surface 111 on the front side and the main surface 111 on the back side). , provided.
The friction portion 12 includes a plurality of segment pieces 13 and oil grooves 14 formed between the segment pieces 13 .
The wet friction material 10 includes a plurality of first pieces 131 and a plurality of second pieces 132 as segment pieces 13 . The total number of segment pieces 13 is 45 pieces. Of these segment pieces 13 , 27 are first pieces 131 and 18 are second pieces 132 .
Three first pieces 131 continuous in the circumferential direction of the core plate 11 form a first piece group 13A, and two second pieces 132 continuous in the circumferential direction of the core plate 11 form a second piece group. forming group 13B.
The first piece group 13A and the second piece group 13B are arranged alternately in the circumferential direction of the core plate 11 .

Regarding the first piece 131, when the maximum length in the left-right direction is W _P1 and the length in the left-right direction of the first lower resection portion 131B is W _D1 , W _D1 /W _P1 =0.18, and W _D1 = 2 mm. Further, when the maximum length in the vertical direction is H _P1 and the length in the vertical direction of the first lower cut portion 131B is H _D1 , H _D1 /H _P1 =0.36, and H _D1 =4. 5 mm.
Regarding the second piece 132, when the length of the second lower resection portion 132B in the left-right direction is W _D2 , W _D2 =W _D1 =2 mm, and the length in the up-down direction of the second lower resection portion 132B is H When _D2 , H _D2 =H _D1 =4.5 mm.

The segment piece 13 is a paper body obtained by papermaking a fiber base material such as pulp and aramid fiber, a friction modifier such as cashew dust, and a filler such as diatomaceous earth, and a thermosetting resin (resin binder) and heat-cured. The segment pieces 13 are joined to both the front and back main surfaces of the core plate 11 by pressurization and heating.
The core plate 11 is made of NCH780 and has gear-shaped engaging teeth 113 on its outer periphery. The outer diameter of core plate 11 (the diameter defined by the outer periphery of core plate 11 excluding engaging teeth 113) is 176 mm, and the inner diameter of core plate 11 is 148.4 mm.

[Example 2]
The wet friction material 10 (see FIG. 7) of Example 2 includes only the first pieces 131 as the segment pieces 13, and the total number is 45 pieces. Except for this difference, it is the same as the wet friction material 1 of the first embodiment.

[Comparative Example 1]
The wet friction material 10 (see FIG. 11) of Comparative Example 1 includes only the second pieces 132 as the segment pieces 13, and the total number is 45 pieces. Except for this difference, it is the same as the wet friction material 1 of the first embodiment.

[2] Correlation between drag torque and rotational speed Using four wet friction materials of each of Examples 1 and 2 and Comparative Example 1 in [1] above, the following results were obtained using an SAE friction tester under the following test conditions: , and the drag torque was measured between 500 and 3000 rpm. The results obtained are shown graphically in FIG.
Note that FIG. 12 shows that the higher the vertical axis, the greater the drag torque.

(1) Test conditions Automatic Transmission Fluid ("ATF" is a registered trademark of Idemitsu Kosan Co., Ltd., but hereafter abbreviated as "ATF" regardless of the registered trademark). : 80 ° C, ATF oil amount: 0.5 L / min (axial lubrication), and about the interval of the wet friction material Pack clearance: 0.20 mm / piece Set four wet friction materials as test specimens , and the rotational speed was changed from 500 to 3000 rpm, and drag torque (Nm) was measured at six points of 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm and 3000 rpm. The measurement time was 15 seconds/each rotation, and the number of repetitions was 5 times.

(2) Effect of Test Example From the results of FIG. 12, it can be seen that the drag torque is reduced in all of the wet friction materials of the Examples as compared with the Comparative Example.
That is, in comparison with Comparative Example 1 in which only the second piece 132 is provided as the segment piece 13, in Examples 1 and 2, a significant drag torque reduction was observed in the entire range of 500 to 3000 rpm.
In addition, as compared with Example 2, which includes only the first piece 131 as the segment piece 13, Example 1, which includes both the first piece 131 and the second piece 132, is more superior in the entire range of 500 to 3000 rpm. A drag torque reduction was achieved.
In particular, in Example 1, excellent drag torque reduction was achieved in the range of 500 to 1000 rpm, and drag torque reduction by the combined use of the first piece 131 and the second piece 132 was achieved in a range where the relative rotation speed was smaller. It is considered to work preferentially.

It should be noted that the present invention is not limited to the specific examples described above, and various modifications can be made within the scope of the present invention according to the purpose and application.

Applications of the wet friction material of the present invention are not particularly limited, and are widely applied to, for example, automobiles (four-wheeled vehicles, two-wheeled vehicles, etc.), railroad vehicles, ships, airplanes, and the like. Among these, as automotive products, it is suitably used for automatic transmissions (AT). Only one wet friction material may be used in the transmission, or a plurality of wet friction materials may be used, but it is preferable to use a plurality of wet friction materials. The more the wet friction material is used in one transmission, the greater the cumulative effect can be obtained. That is, the drag torque can be more effectively reduced in a wet multi-plate clutch in which a large number of wet friction materials are used.

10; wet friction material, 11; core plate, P; rotation center, 111; main surface, 112; outer peripheral surface, 113;
12; friction portion, 13; segment piece, 13A; first piece group, 13B; second piece group,
131; first piece, 131A; first upper resection portion, 131B; first lower resection portion, 131C; upper side, 131D; lower side, 131E;
132; second piece, 132A; second upper resection, 132B; second lower resection, 132C; upper edge, 132D; lower edge, 132E;
14; oil groove, 141; oil reservoir groove, 142; oil drainage groove.

Claims (9)

A wet friction material comprising a flat ring-shaped core plate and a friction portion arranged in a ring shape on a main surface of the core plate,
The friction portion includes a plurality of segment pieces and a plurality of oil grooves formed between the segment pieces,
As the segment piece, a first piece having a substantially quadrilateral shape with the upper left corner and the upper right corner cut off in a substantially triangular shape and the lower left corner and the lower right corner with a substantially quadrangular shape is provided. wet friction material. 3. The segment piece further comprises a second piece having a substantially rectangular shape with the upper left corner and the upper right corner cut off into a substantially triangular shape and the lower left corner and the lower right corner of the piece with a substantially triangular shape. 2. The wet friction material according to 1. 3. The wet friction according to claim 2, wherein in the friction portion, the first pieces and the second pieces that are the same or different in number from the first pieces are alternately arranged in the circumferential direction of the core plate. material. 4. The wet friction material according to claim 3, wherein the first pieces and the second pieces are alternately arranged one by one in the circumferential direction of the core plate. A plurality of the first pieces that are continuous in the circumferential direction of the core plate form a first piece group,
A plurality of the second pieces that are continuous in the circumferential direction of the core plate form a second piece group,
4. The wet friction material according to claim 3, wherein the first piece group and the second piece group are alternately arranged in the circumferential direction of the core plate. The wet friction material according to any one of claims 1 to 5, wherein the number of said first pieces is 10% or more and 90% or less of the total number of said segment pieces. When the wet friction material is rotated in the circumferential direction around the center of the ring shape of the core plate in the presence of lubricating oil,
7. The shape of the first piece is such that the lower left corner and the lower right corner of the first piece are cut off in a substantially rectangular shape, and a dam portion is formed to allow the lubricating oil to run up onto the surface of the friction portion. Wet friction material according to any one of the above. In the first piece, 0.08≦W _D1 / where W _P1 is the maximum length in the left-right direction of the first piece, and W _D1 is the length in the left-right direction of the portion cut into a substantially rectangular shape. The wet friction material according to claim 7, wherein W _P1 ≤ 0.34. In the first piece, 0.07≦H _D1 / where H _P1 is the maximum length in the vertical direction of the first piece, and H _D1 is the length in the vertical direction of the portion cut into a substantially rectangular shape. The wet friction material according to claim 7 or 8, wherein H _P1 ≤ 0.4.

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