JP2020020364A - Core plate, manufacturing method thereof and wet friction material - Google Patents

Abstract

To provide a core plate capable of suppressing reduction in friction characteristic of a wet friction material over time, especially reduction of a μ value, a manufacturing method thereof, and a wet friction material using the core plate.SOLUTION: A core plate 1 has an annular shape, becomes a wet friction material by arranging a friction base material on a main surface 1c, and includes two or more plate layers 13 in a thickness direction. A wet friction material has a friction base material arranged on the main surface 1c of the core plate. A method comprises: punching a sheet material obtained by unwinding a wound state, to obtain two annular plate layers 13; and arranging an inside surface in the wound state of each of the two plate layers toward a center side in the thickness direction.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a core plate, a method for manufacturing the same, and a wet friction material. More specifically, the present invention relates to a wet friction material used in the presence of a lubricating oil, a core plate used for the wet friction material, and a method of manufacturing the same.

Conventionally, a wet clutch or a wet brake using a wet friction material has been used for torque transmission, braking, and the like. For example, in an automatic transmission such as an automobile, a wet friction material is used in a wet hydraulic clutch.
The wet hydraulic clutch has a structure in which a plurality of wet friction materials and a plurality of separator plates are alternately arranged with a small clearance therebetween, and torque transmission / non-transmission is performed by pressing and separating the two. Further, lubricating oil is supplied into the clutch for the purpose of reducing the friction of the wet friction material during the press-contact / separation and absorbing the frictional heat accompanying the friction. The following Patent Documents 1 and 2 are known as a core plate and a wet friction material used for such a purpose.

JP-T-2009-527696 JP 2017-223289 A

  It is known that the friction characteristics of a wet friction material decrease as its use time increases. For example, the μ value decreases as the usage time increases. It is known that the reason for the decrease in the μ value is due to the decrease in the characteristics of the friction base material (friction material segment). The present inventor has discovered a conventionally unknown factor other than the deterioration of the friction base material as a factor of the time-dependent decrease in the friction characteristics of the wet friction material, and reducing the factor to reduce the time-dependent μ value. The present inventors have found that significant reduction can be suppressed, and completed the present invention.

  Patent Document 1 discloses that, when a core plate is obtained from a raw steel material, in order to reduce unnecessary parts that are inevitably generated, the parts are cut out as segmented parts, and parts are engaged and integrated using tabs and slots. By doing so, an annular core plate is disclosed. On the other hand, Patent Literature 2 discloses a method of forming an oil hole penetrating the inner peripheral side and the outer peripheral side of a core plate. However, in any case, neither attention nor examination has been made on the deformation of the core plate and its suppression.

  The present invention has been made in view of the above problems, and a core plate and a method of manufacturing the core plate capable of suppressing a decrease in frictional properties of a wet friction material over time, particularly a decrease in μ value, and wet friction using the core plate. The purpose is to provide materials.

2. Description of the Related Art In recent years, there has been a strong demand for low fuel consumption of wet transmission mechanisms for vehicles. As a countermeasure against this, it is known that reduction of drag torque during idling of the wet friction material is effective. Further, in a device having a plurality of wet friction members in a transmission mechanism, such as a wet multi-plate clutch, reducing the number of constituent members is considered to be an effective drag torque reduction method.
However, when the number of components is reduced, it is necessary to enhance the functions performed by the individual wet friction materials. For example, it is necessary to increase the μ value that can be exhibited by each wet friction material. In this regard, it is considered that if the decrease in the μ value over time as described above can be suppressed and the initial μ value can be maintained, this can be an effective means for reducing the number of components.

The present inventor has studied the suppression of the deterioration over time of the friction characteristics of the wet friction material due to such circumstances, and found that the core plate itself deformed with time, and that the μ value was reduced by suppressing this deformation. It has been found that the reduction of the temperature can be suppressed, and the present invention has been completed.
That is, the core plate is manufactured by using a prototype cut out of a strip-shaped steel material. And this steel material is supplied in the shape of a strip, and inherently has a “winding”. For this reason, before and after the cutting of the prototype serving as the core plate, a work of correcting the curl may be performed on the steel material or the prototype. However, when used as a wet friction material, a strong thermal cycle was imposed during its use, and it was thought that "warping" was gradually caused by stress release considered to be caused by winding (FIG. 12). reference). When this warpage occurs, the contact area of the wet friction material such as the separator plate with the counterpart material, which is the contact partner, decreases (see FIG. 11), and the μ value may decrease over time. Furthermore, it was considered that when the contact area between the friction base material and the mating material was reduced (see FIG. 11), frictional heat was concentrated at the contact portion, and the material constituting the friction base material was thermally degraded. For this reason, it is considered that if the above-mentioned warpage can be suppressed, a decrease in the contact area between the friction base material and the mating material can be suppressed, and the thermal deterioration of the material constituting the friction base material can be suppressed at the same time. Therefore, the present invention was completed by dividing the core plate in the thickness direction, dividing the potential stress in each layer, and dispersing the stress of one plate layer to a small extent, thereby suppressing the warpage. I let it.

That is, the present invention is as follows.
[1] The core plate according to claim 1 is a core plate for a wet friction material that forms an annular shape and is a wet friction material by arranging a friction base material on a main surface,
The gist is to provide two or more plate layers in the thickness direction.
[2] The core plate according to the second aspect is the core plate according to the first aspect, further comprising three or more plate layers in a thickness direction.
Having two outer plate layers constituting the front and back surfaces, and at least one middle plate layer sandwiched between the two outer plate layers,
At least one of the middle plate layers has a plurality of arc-shaped parts assembled in an annular shape.
[3] A core plate according to a third aspect of the present invention is the core plate according to the second aspect, wherein each of the two outer layers is formed of one annular metal plate.
[4] The core plate according to claim 4 is the core plate according to claim 2 or 3, wherein the arc-shaped parts are assembled via a gap,
The gist is that the gap is an oil passage penetrating through the inner peripheral side and the outer peripheral side of the core plate.
[5] In the core plate according to the fifth aspect, in the core plate according to any one of the second to fourth aspects, the outer plate layer and the middle plate layer are joined to each other via a cured resin. The gist is that
[6] The wet friction material according to claim 6, wherein the core plate according to any one of claims 1 to 5,
And a friction substrate disposed on the main surface of the core plate.
[7] The method for manufacturing a core plate according to claim 7 is the method for manufacturing a core plate according to any one of claims 1 to 6, wherein
A punching step of punching a plate material obtained by unwinding the roll to obtain two annular plate layers;
The gist of the present invention is to provide an arrangement step in which the two plate layers obtained in the punching step are arranged in the following arrangement (1) or (2).
(1) The inner surface of each of the two plate layers in the wound state is directed toward the center in the thickness direction. (2) The inner surface of each of the two plate layers in the wound state. Are arranged outward in the thickness direction.

  The present core plate 1 is a core plate 1 for a wet friction material, which is formed in an annular shape and is a wet friction material 2 by disposing a friction base material 3 on a main surface 1c, and has two or more layers in a thickness direction. A plate layer 13 is provided. According to the core plate 1, each plate layer 13 can be formed by using a material having a smaller thickness than that of the related art (see FIG. 10). That is, each plate layer 13 can be formed by using a material having a smaller curl as compared with the related art. For this reason, it is possible to disperse the stress in the layer thickness direction while suppressing the stress caused by the winding of the single plate layer 13 to be small. Thereby, the deformation with time of the wet friction material 2 can be significantly suppressed. As a result, it is possible to suppress a decrease in friction characteristics, particularly a decrease in μ value. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed.

  In the present core plate 1, three or more plate layers 13 are provided in the thickness direction, and two outer plate layers (131 and 132) constituting the front surface 1a and the back surface 1b, and these two outer plate layers (131 and 132). 132), and at least one middle plate layer 133 sandwiched between the middle plate layers 133, and at least one of the middle plate layers 133 is formed by a plurality of arc-shaped parts 139 being assembled in an annular shape. In addition to the above-described effects, by dividing the middle plate layer 133 of the core plate 1 in the plane direction, the stress caused by the curl latent in the middle plate layer 133 is reduced by the division, and the stress in the plane direction is reduced. Can be dispersed. Thereby, the deformation with time of the wet friction material 2 can be significantly suppressed. As a result, a reduction in the μ value and an improvement in heat resistance can be achieved.

  In the present core plate, when each of the two outer plate layers (131 and 132) is made of one annular metal plate, the outer plate layers (131 and 132) are divided in the plane direction ( That is, as compared with the case where it is configured as an aggregate of a plurality of arc-shaped parts 139), the deformation impulses resulting from the release of the stress in the middle plate layer 133 can be effectively suppressed. Thereby, the deformation with time of the wet friction material 2 can be largely suppressed, and a reduction in the μ value and an improvement in heat resistance can be achieved.

In the core plate, arc-shaped parts 139 to each other, are set through the gap 15, the gap 15, the inner circumferential side S _I and the outer S _O and the oil passage 15 passing through in the of the core plate 1 In the case of, the deformation when the stress is released can be absorbed by the gap 15. Therefore, the deformation with time of the wet friction material 2 can be extremely effectively suppressed, and as a result, a reduction in the μ value and an improvement in heat resistance can be achieved. In addition, since the gap 15 between the arc-shaped parts 139 can function as the oil passage 15, the core plate itself can be cooled from inside the core plate 1 during use.

  In the present core plate, when the outer plate layers (131 and 132) and the middle plate layer 133 are joined to each other via a cured resin, the stress in the outer plate layers (131 and 132) and the middle plate layer 133 is increased. The deformation impulses resulting from the release can be effectively suppressed by the cured resin. That is, since the stress is reduced by the division in the thickness direction, the outer plate layers (131 and 132) and the middle plate layer 133 can be restrained by joining with the cured resin, and the deformation impulses can be suppressed. Therefore, the deformation with time of the wet friction material 2 can be extremely effectively suppressed, and a reduction in the μ value and an improvement in heat resistance can be achieved.

  The present wet friction material 2 has a present core plate 1 and a friction substrate 3 arranged on a main surface 1c of the present core plate 1. As described above, since the core plate 1 is a core plate that can suppress temporal deformation under a heat cycle, the effect can be exerted even in the wet friction material 2 using the core plate. As a result, in the present wet friction material 2, a decrease in the contact area with the mating material due to the deformation of the core plate 1 can be suppressed, and a decrease in friction characteristics, particularly, a decrease in μ value can be suppressed. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed.

  The method of manufacturing the core plate 1 includes a punching step of punching a sheet material obtained by unwinding the rolled state to obtain two annular plate layers 13, and a two-layer plate layer obtained by the punching step. 13 are arranged in the arrangement of (1) or (2) described above. According to this method, it is possible to obtain the core plate 1 in which the curl that can be caused by the curling is arranged toward the center or the outside in the thickness direction of the core plate 1. That is, by dividing the core plate 1 in the thickness direction, in addition to dividing the stress latent in each plate layer into small portions, the deformation impulses due to the stress release can be directed to the center side or the outside in the thickness direction of the core plate. Can be. For this reason, the deformation impulses can be offset from both surface sides toward the center side or the outside. Therefore, it is possible to obtain a core plate that effectively suppresses the deformation of the wet friction material over time and achieves a reduction in μ value and an improvement in heat resistance. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed.

It is a perspective view showing an example of this core plate. FIG. 3 is an exploded perspective view showing an example of the present core plate. It is a perspective view which shows the other example of this core plate. It is a perspective view which decomposes | disassembles and shows another example of this core plate. It is a perspective view showing an example of this wet friction material. It is a perspective view showing other examples of this wet type friction material. It is explanatory drawing explaining the oil passage of another example of this wet friction material. It is explanatory drawing explaining the oil passage of another example of this wet friction material. FIG. 4 is an explanatory diagram illustrating a change over time of the present wet friction material. It is explanatory drawing explaining the manufacturing method of this core plate, and a temporal change. It is explanatory drawing explaining the time-dependent change of the conventional wet-type friction material. It is explanatory drawing explaining the manufacturing method of the conventional core plate, and a temporal change. It is a graph which shows the endurance cycle by each wet friction material of an example and a comparative example, and a μd value, a core plate temperature, and a correlation with the amount of warpage of a core plate.

Hereinafter, the present invention will be described with reference to the drawings. The matters described here are for the purpose of exemplification and illustrative embodiments of the present invention, and are considered to be the descriptions that enable the principle and conceptual features of the present invention to be understood most effectively and without difficulty. It is stated for the purpose of providing what is In this regard, it is necessary for a basic understanding of the present invention and is not intended to show more than a certain degree of structural detail of the present invention, and some forms of the present invention will be described in conjunction with the drawings. Will be apparent to those skilled in the art how is actually implemented.
In the description of the planar shape of each part in this specification, the shape will be described assuming that it is arranged at the 12 o'clock position on the timepiece dial.

[1] Core plate The core plate (1) of the present invention has a circular shape, and is used for a wet friction material that becomes a wet friction material (2) by disposing a friction substrate (3) on a main surface (1c). The core plate (1) includes two or more plate layers (13) in a thickness direction (see FIGS. 1 to 4).

The core plate 1 has an annular shape (that is, a ring shape). That is, it has a ring shape in which the center of the plate body is opened. The core plate 1 has the center of this ring as the rotation center P.
The main surface 1c of the core plate 1 is a surface on which the friction base material 3 is arranged. That is, it means a surface excluding the peripheral surface (the inner peripheral surface and the outer peripheral surface) of the core plate 1. In the present application, one of the main surfaces 1c of the core plate 1 is referred to as a front surface 1a, and the other surface is referred to as a back surface 1b. The friction substrate 3 may be disposed only on the front surface 1a of the core plate 1, or may be disposed on both the front surface 1a and the rear surface 1b (see FIGS. 1 and 3).

The “plate layer (13)” is a layer constituting the core plate 1 (see FIGS. 2 and 4). The plate layer 13 is a layer made of a structural material, and is a layer excluding a layer (joining layer) having only a function of only joining the structural materials.
The plate layer 13 means a specific layer constituting the core plate 1, and the plate layer 13 may be a single integrated layer or a single layer formed of a plurality of parts. Layer. That is, when the core plate 1 is composed of three plate layers 13, one intermediate plate layer 133 as an intermediate layer can be composed of four arc-shaped parts 139 as shown in FIG. 4. In FIG. 4, the middle plate layer 133 is a single layer composed of four arc-shaped parts 139.

  The core plate 1 has two or more plate layers 13. That is, the core plate 1 is configured by laminating two or more plate layers 13. As a result, the deformation impulses caused by the stress latent in the single plate layer 13 can be reduced as compared with the core plate formed of a single annular metal plate that has been conventionally used. That is, the stress associated with the winding potential of the plate material supplied in a rolled state is greater as the thickness of the plate material is larger, and as the thickness is larger, a cost for suppressing this stress is required, Material becomes expensive. In this regard, in the present core plate 1, the thickness of the single plate layer 13 can be reduced, so that the stress latent in the single plate layer 13 can be reduced, and a low-cost material can be used. Then, the stress can be dispersed to the two or more plate layers 13.

And the above-mentioned action can significantly suppress the deformation of the wet friction material over time. As a result, it is possible to suppress a decrease in friction characteristics, particularly a decrease in μ value. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, since the warpage of the core plate 1 with time can be suppressed, the clearance (pack clearance) between the core plate 1 and the mating material can be maintained for a long time without changing from the initial value. Can be suppressed.
In addition, as described above, by using a thin plate material, the fracture surface can be made smoother. That is, the plate layer 13 is usually formed by stamping out a plate material. Although a burr-like non-smooth portion generated at the time of punching is inevitably formed in this fractured surface, the non-smooth portion can be reduced as the thickness of the plate material as the raw material is reduced. Therefore, in the present multi-layered core plate, the non-smooth portion generated in the fracture surface of each single plate layer 13 can be reduced. Therefore, when the spline teeth are provided, the engagement surface with the spline shaft can be made smooth and the aggressiveness to the spline shaft can be reduced.

The thickness of each plate layer 13 is not limited, but is usually 3 mm or less. The thickness of the plate layer 13 can be, for example, 0.1 mm or more and 3 mm or less, and preferably 0.2 mm or more and 2 mm or less. Further, each plate layer 13 usually has a substantially uniform thickness. That is, in one plate layer 13, it is preferable that the main part thereof (the main part excluding a groove or the like in the case of having a groove) has substantially the same thickness. On the other hand, each of the plurality of plate layers 13 may have the same thickness, or may have different thicknesses. That is, for example, in the case of the core plate 1 having the two plate layers 13 of the A layer and the B layer, the A layer and the B layer may have the same thickness or different thicknesses. .
Note that the thickness of the plate layer 13 is an average value of the thickness measured at ten different points in the main part of the plate layer 13.

The material constituting the plate layer 13 is not limited, but is usually a metal and / or a resin. Among them, various metals, aluminum alloys, titanium alloys and the like can be used as the metal. Among them, as the steel material, a carbon steel (S35C, S55C, etc.), a cold-rolled steel plate (SPCC, SPCCT, etc.), and a low carbon high tensile steel (NCH780, etc.) can be used. These may be used alone or in combination of two or more.
Examples of the resin include polyamide resin (heat-resistant polyamide resin), epoxy resin, polyimide resin, polyacetal resin, fluorine resin, polyetherketone resin, polyetheretherketone resin, polyetherketoneetherketoneketone resin, polyphenylsulfone. Resin, polyphenylene sulfide resin and the like, and fiber reinforced products of these resins. These may be used alone or in combination of two or more.

  As described above, the core plate 1 preferably has at least one or more metal plate layers 13 because deformation due to curling of the steel material can be suppressed as described above. That is, the core plate 1 can be the core plate 1 including two or more plate layers 13 in the thickness direction, and at least one of the plate layers 13 is a metal plate layer 13.

  Further, the outer surface of the core plate 1 (in this case, both surfaces of the front surface 1a and the back surface 1b) is preferably made of metal. Since the outer surface is made of metal, it is possible to obtain characteristics equivalent to those of a conventionally used core plate made of a single annular metal plate in characteristics such as heat resistance, heat dissipation and flexibility. it can. From such a viewpoint, the present core plate 1 preferably has two metal outer plate layers (a front plate layer 131 and a back plate layer 132) constituting the front surface 1a and the back surface 1b.

  Further, each of the outer plate layers (the front plate layer 131 and the back plate layer 132) can be composed of a plurality of arc-shaped parts (arc-shaped parts obtained by dividing an annular shape). Preferably, it is formed of a single annular metal plate (see FIG. 4). When a single annular metal plate is used, the stress release in the middle plate layer 133 is smaller than when the outer plate layer is divided in the plane direction (that is, when the outer plate layer is configured as an aggregate of a plurality of arc-shaped parts). Deformation impulses resulting from the above can be effectively suppressed. Thereby, the deformation with time of the wet friction material 2 can be suppressed, and the reduction in the μ value and the improvement in heat resistance can be achieved.

Further, the core plate 1 can include three or more plate layers 13 in the thickness direction (see FIGS. 3 and 4). That is, the two outer plates (the front plate layer 131 and the back plate layer 132) constituting the front surface 1a and the back surface 1b and the two outer plate layers (the front plate layer 131 and the back plate layer 132) are sandwiched. And at least one middle plate layer 133. At this time, the middle plate layer 133 may be composed of only one layer, or may be composed of two or more layers.
At least one of the middle plate layers 133 can be a layer in which a plurality of arc-shaped parts 139 are collected in an annular shape (see FIG. 4).

In the present core plate, as described above, when at least one middle plate layer 133 is formed as an annular aggregate of a plurality of arc-shaped parts 139 (see FIG. 4), the middle plate layer 133 is hidden by the middle plate layer 133. The stress caused by the curling can be reduced and dispersed by the division in the plane direction. In addition, since the division in the plane direction is different from the division in the thickness direction, the stress can be dispersed in a direction different from that of the outer plate layers (the front plate layer 131 and the back plate layer 132). Thus, the deformation of the core plate over time in the wet friction material can be significantly suppressed. As a result, a reduction in the μ value and an improvement in heat resistance can be achieved.
When the middle plate layer 133 is formed as an aggregate of the arc-shaped parts 139, the number of the arc-shaped parts 139 is not limited, but usually it is preferably 2 pieces or more and 30 pieces or less, more preferably 2 pieces or more and 15 pieces or less. Preferably, it is 2 pieces or more and 10 pieces or less.

Furthermore, when the middle plate layer 133 is formed of an annular assembly in which a plurality of arc-shaped parts 139 are arranged in an annular shape, these arc-shaped parts 139 are brought into close contact with their side end faces so that no gap is formed. Can be assembled. On the other hand, the side end surfaces of the arc-shaped parts 139 can be assembled via the gap 15 without making the side end faces contact each other (see FIG. 4). When an annular aggregate in which a plurality of arc-shaped parts 139 are assembled via the gap 15 is used as the middle plate layer 133, the gap 15 is formed in the outer plate layer (the front plate layer 131 and the back plate layer) in the thickness direction. since sandwiched 132) or the like, the gap 15, into an inner side _{S I} and the outer _{S O} of the core plate 1 is penetrated. For this reason, the gap can function as the oil passage 15.

  When the core plate 1 includes the middle plate layer 133 having the gap 15, even if the stress latent in the plurality of arc-shaped parts 139 constituting the middle plate layer 133 is released in use, the deformation accompanying the stress is eliminated. Can be absorbed by the gap 15. That is, since the respective side end surfaces of the arc-shaped parts 139 that are assembled in an annular shape are arranged via the gap 15, even if the arc-shaped parts 139 are deformed, the gap 15 can be deformed and absorbed. . Furthermore, in other words, when an annular aggregate in which the respective side end surfaces of the arc-shaped part 139 are in close contact with each other is used as the intermediate plate layer 133, there is no place where the deformation of the arc-shaped part 139 is released, and the arc-shaped part 139 is not released. When the arc-shaped parts 139 are pressed against each other, they may be stressed and accumulated in the middle plate layer 133. On the other hand, in the middle plate layer 133 having the gap 15, even such stress accumulation can be prevented, and the deformation of the gap 15 can absorb the deformation of the arc-shaped part 139.

By using the annular aggregate having such a gap 15 as the middle plate layer 133, it is possible to extremely effectively suppress the deformation of the wet friction material over time. As a result, a reduction in the μ value and an improvement in heat resistance can be achieved.
In addition, the gap 15 can function as the oil passage 15 in the wet friction material 2. Thus, in use, through the oil passage 15, from the inner circumferential side S _I to the outer peripheral side S _O can be circulated lubricating oil, which allows the cooling of the core plate 1 itself from the inside of the core plate 1. The degree of cooling can be designed according to the size and number of the gaps 15. From such a viewpoint, the heat resistance of the wet friction material 2 can be improved. From the viewpoint of cooling the core plate 1 through the oil passage 15, the middle plate layer 133 is preferably thicker, and the number of the oil passages 15 is preferably large.

  In the case where the arc-shaped parts 139 are employed in the core plate 1, the arc-shaped parts 139 have no engaging portions at their side ends to engage with each other regardless of the presence or absence of the gap 15. Is preferred. When the arc-shaped part 139 has an engaging portion, the deformation generated in each arc-shaped part 139 is easily spread to other arc-shaped parts 139 through the engaging portion, and the intermediate plate layer 133 is divided into circles. This is because it is difficult to enjoy the advantage of using the arc-shaped part 139 as the annular polymer.

  When the core plate 1 includes the gap 15, the core plate 1 may include any number of places, and the number is not limited. For example, the core plate 1 shown in FIG. 4 has four gaps 15, but is not limited thereto, may have less than four gaps 15, or may have more than four gaps 15. Specifically, the gap 15 can be two or more places, preferably two or more places, and 30 or less places, more preferably two or more places and 15 places or less, and more preferably two places or more and ten places or less. It is particularly preferred to do so. By providing two or more gaps 15, the deformation of the arc-shaped part 139 can be absorbed. From the viewpoint of absorption of deformation and cooling as an oil passage, it is preferable that the gap 15 is large, and the gap 15 can be 10 or more, and further, 15 or more, but more than 30. Although the number may be large, it is preferably 30 or less from the viewpoint of increasing the rigidity of the core plate 1.

The width of the gap 15 is not limited, for example, the width _{W SI} of the inner circumferential side of the gap 15 may be a 0.1mm or 3mm or less, it is preferable to 0.2mm or 2mm or less. Similarly, the width W _SO on the outer peripheral side of the gap 15 can be 0.1 mm or more and 3 mm or less, and preferably 0.2 mm or more and 2 mm or less. However, the width W _SI on the inner circumference side and the width W _SO on the outer circumference side may be the same width or different widths.
That is, when the gap 15 functions as the oil passage 15, the shape of the passage is not limited. For example, the core plate 1 shown in FIG. 4, but illustrates the oil passage 15 of substantially uniform width between the inner circumferential side S _I and the outer S _O, but is not limited thereto. For example, the inner circumferential side S _I may be an oil passage which is wider than the outer peripheral side S _O, may be an oil passage whose inner circumferential side S _I is narrower than the outer circumferential side S _O Good.

In the core plate 1, the outer plate layers (the front plate layer 131 and the back plate layer 132) and the middle plate layer 133 may be joined in any manner. When both the back plate layer 132) and the middle plate layer 133 are made of a metal plate, these layers can be joined via a cured resin. When a joining material is not used, a roll-joined metal that has been roll-joined can also be used. Further, for example, when the outer plate layers (the front plate layer 131 and the back plate layer 132) are made of a metal plate and the middle plate layer 133 is made of a cured resin, the outer plate layer (the front plate layer) is formed by the middle plate layer 133 itself. 131 and the back plate layer 132).
Examples of the cured resin include a phenol resin (a resol type phenol resin and a novolak type phenol resin), an epoxy resin and the like. These may be used alone or in combination of two or more.

The correlation between the outer diameter and the inner diameter of the core plate 1 is not limited. For example, when the outer diameter is R ₁ and the inner diameter is R ₂ , the ratio R ₁ / R ₂ is 1 ≦ R ₁ / R ₂ ≦ 10 and 1.05 ≦ R ₁ / R ₂ ≦ 5, and 1.1 ≦ R ₁ / R ₂ ≦ 3.
Among them, for example, R ₂ can be 30 ≦ R ₂ (mm) ≦ 300, 40 ≦ R ₂ (mm) ≦ 250, and 50 ≦ R ₂ (mm) ≦ 200. be able to.
The outer diameter R ₁ is the diameter of the outer peripheral basal surface, the inner diameter R ₂ is the diameter of the inner peripheral basal surface, it is assumed that the average value of the basal plane diameter of 10 locations to be measured at random. For example, when spline teeth protrude from the peripheral surface (inner peripheral surface or outer peripheral surface) of the core plate 1, the peripheral surface excluding the spline teeth is the base surface.
The core plate 1 does not need to have spline teeth, but may have spline internal teeth projecting from the inner peripheral surface or spline external teeth projecting from the outer peripheral surface.

Further, the thickness of the core plate 1 is not limited. For example, when the thickness is D, 0.3 ≦ D (mm) ≦ 12, and 0.4 ≦ D (mm) ≦ 8. And 0.5 ≦ D (mm) ≦ 6.
Note that the thickness D is the thickness at the base, and is an average of the thicknesses of the 10 bases measured at random.

[2] Wet friction material The wet friction material (2) of the present invention includes the above-described core plate (1) of the present invention. Further, the wet friction material (2) includes a friction substrate (3) arranged on the main surface (1c) of the core plate (1) (see FIGS. 5 to 9).

  The wet friction material 2 includes the core plate 1 described above. Therefore, the effect that the temporal deformation obtained by the core plate 1 can be greatly suppressed, and further, the effect obtained by that effect, that is, the reduction of the frictional characteristics, particularly the reduction of the μ value, can be enjoyed as they are. Similarly, since a local increase in temperature due to frictional heat can be suppressed, the effect of improving heat resistance can be enjoyed as it is.

The surface of the friction substrate 3 is a friction surface, and the friction between the wet friction material 2 and the mating material depends on the degree of contact between the wet friction material 2 and the mating material (such as a separator plate) adjacent thereto. It is a member that can adjust the degree of interlocking. That is, it is a member that can exhibit a braking function (braking function) and a torque transmitting function for the partner material.
The configuration of the friction base material 3 is not limited, and for example, a material obtained by hardening a paper body containing a base fiber and a filler with a curable resin can be used.
Among them, various synthetic fibers, regenerated fibers, inorganic fibers, natural fibers, and the like can be used as the 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, and the like can be used. These may be used alone or in combination of two or more. Further, a phenol resin and / or a modified resin thereof can be used as the thermosetting resin.
The friction substrate 3 is usually fixed by being joined to the main surface 1c of the core plate 1, but the joining method with the core plate 1 is not limited, and the adhesion (adhesion) via heat fusion, an adhesive or the like is performed. ) Can be used.

Further, only one or a plurality of friction substrates 3 can be provided for one core plate 1. As described above, since the core plate 1 has an annular shape, the friction base material 3 is usually also arranged in an annular shape (see FIGS. 5 to 9).
When only one friction substrate 3 is provided, an annular friction substrate 3 corresponding to the annular shape of the core plate 1 can be obtained.
When a plurality of friction substrates 3 are provided, they can be arranged in an annular shape corresponding to the annular shape of the core plate 1. In particular, it is possible to provide a gap between adjacent friction substrates 3 and arrange them in an annular shape. In this case, a gap defined by adjacent friction substrates 3 functions as an oil groove 4. That is, the oil groove 4 is a through groove is penetrated into the inner circumferential side S _I and the outer S _O.

Oil groove 4, the lubricating oil supplied from the inner peripheral side S _I of the wet friction material 2, may serve as a guide for discharging toward the outer circumferential side S _O. Further, it can function as a weir for preventing the lubricant oil from running on the surface of the friction substrate 3 more than necessary. Also, a plurality of oil grooves 4 can be arranged according to the number of friction base materials 3.

When a plurality of friction substrates 3 are provided, the planar shapes of the friction substrates 3 may be the same or different from each other. Similarly, when a plurality of oil grooves 4 are provided, the plane shapes of the oil grooves 4 may be the same or different from each other. In particular, the oil groove 4 can have an appropriate shape as needed. For example, the oil groove 4, the inner circumferential side S gradually wide toward the outer circumferential side S _O from _I narrowing shape oil groove of substantially equal width shape from the inner circumferential side S _I to the outer periphery S _O oil grooves, such as oil groove shape that gradually narrow reduction toward the outer circumferential side S _O to the inner circumferential side S _I is exemplified. These may be used alone or in combination of two or more.

  In the present wet friction material 2, the number of the friction substrates 3 arranged on one main surface 1c of the core plate 1 is not limited, but may be, for example, 10 or more and 120 or less. This number is preferably 15 or more and 100 or less, more preferably 20 or more and 80 or less, and particularly preferably 25 or more and 60 or less.

[3] Manufacturing method of core plate The manufacturing method of the core plate (1) of the present invention includes: a punching step of punching a plate material obtained by unwinding a roll to obtain two annular plate layers;
And (b) arranging the two plate layers obtained in the punching step in the following arrangement (1) or (2).
(1) The inner surface in the wound state of each of the two plate layers is oriented toward the center in the thickness direction. (2) The inner surface in the wound state of each of the two plate layers is aligned in the thickness direction. Outward arrangement

  As described above, the inventor of the present invention has found that the core plate itself has been deformed with the passage of time while examining the suppression with time of the frictional characteristics of the wet friction material. Although the cause of this deformation is not clear, it was thought to be due to the plate material (raw material of the core plate) supplied in a wound state. Specifically, the core plate is manufactured using a prototype cut out of a band-shaped plate material. Since this plate material is supplied in the form of a strip, it has a “winding”. That is, even though the plate material (raw material of the core plate) supplied in the wound state is unwound and appears to be flat, the stress of returning to the wound state (ie, curling). But is hidden inside it. Further, even if leveling is performed on the unwound flat plate material by means of pressurization or pressurization and heating, it is difficult to remove the stress or to release the stress. For this reason, even if the plate material is subjected to leveling, the stress continues to be latent. When a friction base material is provided on the core plate where the stress is latent to obtain a wet friction material, the core plate is exposed to a hot cycle in which heating and cooling during use are repeated, and the latent stress is gradually released. It is considered that this causes the deformation (warpage) of the wet friction material to appear.

  When the above-described warpage occurs, the contact area of the wet friction material such as the separator plate with the counterpart material that is the contact partner decreases (see FIG. 11), and the μ value can be reduced with time. Furthermore, when the contact area between the friction base material and the mating material decreases, frictional heat is concentrated at the contact portion, and it is considered that the material constituting the friction base material is thermally degraded. For this reason, it was considered that if the above-mentioned warpage could be suppressed, a decrease in the contact area between the friction base material and the mating material could be suppressed, and the thermal deterioration of the material constituting the friction base material could be suppressed at the same time. Then, it was thought that warping could be suppressed by dividing the core plate in the thickness direction, subdividing the stress latent in each layer, and dispersing the stress of one plate layer to a small extent. Further, as a result, the plate material having a small thickness has a small latent stress, and the cost for suppressing the stress can be reduced.

In addition, as in the present method, the two plate layers obtained in the punching step are arranged such that the inner side surfaces in the wound state of the two plate layers are directed toward the center in the thickness direction. In the case where there is a disposing step, a core plate (1-1) in which the inner side surfaces in the wound state of each of the two plate layers are joined to face the center in the thickness direction is obtained.
On the other hand, in a case where the two plate layers obtained in the punching step each have an arrangement step of disposing the inner side surface in the wound state of each of the two plate layers so as to face outward in the thickness direction. Can obtain a core plate (1-2) in which the inner side surfaces in the wound state of each of the two plate layers are bonded to face outward in the thickness direction.

In the core plate (1-1) thus obtained, a core plate in which curls that can be caused by curling are arranged toward the center in the thickness direction of the core plate can be obtained. In other words, by dividing the core plate in the thickness direction, in addition to being able to divide the stress latent in each plate layer into small portions, it is possible to direct the deformation impulses due to the stress release toward the center of the core plate in the thickness direction in a well-balanced manner. it can. For this reason, the deformation impulses can be offset from both surfaces toward the center. Therefore, it is possible to obtain a core plate that effectively suppresses the deformation of the wet friction material over time and achieves a reduction in μ value and an improvement in heat resistance.
On the other hand, in the core plate (1-2), it is possible to obtain a core plate in which curls that can be caused by curling are arranged outward in the thickness direction of the core plate. That is, by dividing the core plate in the thickness direction, in addition to being able to divide the stress latent in each plate layer into smaller portions, the deformation impulses due to the stress release can be directed to the outside in the thickness direction of the core plate in a well-balanced manner. . For this reason, the deformation impulses can be offset from both surface sides to the outside. Therefore, it is possible to obtain a core plate that effectively suppresses the deformation of the wet friction material over time and achieves a reduction in μ value and an improvement in heat resistance.

As described above, in the case of the above (1) arrangement or the above (2) arrangement, it is preferable that the two plate layers have substantially the same thickness. Specifically, when one thickness of the two plate layers is D ₁ (mm) and the other thickness is D ₂ (mm), D ₁ / D ₂ is 0.8 ≦ D It is preferable that ₁ / D ₂ ≦ 1.2, and it is more preferable that 0.9 ≦ D ₁ / D ₂ ≦ 1.1. As described above, the core plate having a configuration in which the core plates are uniformly arranged inward can be applied to a configuration other than the above-described two layers. That is, the present invention can be applied to a core plate divided into even layers.
On the other hand, when the configuration number of the core plate is an odd-numbered layer, it is preferable that a larger number of plate layers are arranged facing each other (inward and outward) in a well-balanced manner. It is preferable that the layer that cannot be made uniform in any direction be disposed closer to the center.

[4] Embodiment (1) Embodiment 1 (two-layer core plate and wet friction material)
As shown in FIG. 10, two cut plate members 62 are obtained from a metal plate member 61 supplied in a rolled state, and are corrected and subjected to correction. Is latent) get. The corrected plate material 63 is punched (a punching step) to obtain two ring-shaped integrated plate layers 13. Next, the inner side surfaces (62a and 62b) in the wound state of each of the obtained two plate layers are arranged toward the center in the thickness direction (arrangement step), and these layers are joined by a cured resin. Thus, a core plate 1 (see FIGS. 1 and 2) is obtained.

The obtained core plate 1 (see FIGS. 1 and 2) becomes an annular core plate 1 having two plate layers 13 in the thickness direction. These two layers are both outer plate layers (a front plate layer 131 and a back plate layer 132), each of which is formed of one annular metal plate. Further, the stresses caused by the latent curl are offset toward each other toward the center in the thickness direction, and are restrained by the cured resin.
Then, the friction base material 3 is joined to the main surface 1c (both the front surface 1a and the back surface 1b) of the core plate 1 using a hardening resin to obtain a wet friction material 2 (see FIG. 5).
Note that the thickness of each plate layer 13 (the front plate layer 131 and the back plate layer 132) can be, for example, 0.25 to 0.50 mm.

  The thus obtained wet friction material 2 (see FIG. 5) can form the plate layer 13 using a thin material having a smaller curl than conventional ones. In addition to reducing the resulting stress, the stress can be dispersed in the layer thickness direction. Furthermore, the stress can be offset by the arrangement. The temporal deformation of the wet friction material 2 can be greatly suppressed. As a result, it is possible to suppress a decrease in friction characteristics, particularly a decrease in μ value. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed (see FIG. 9).

  9A is a diagram in comparison with FIG. 11A, and schematically shows that the core plate 1 does not deform over time. FIG. 9 (b) is a diagram in comparison with FIG. 11 (b), and schematically shows that the wet friction material 2 does not deform over time. Since the wet friction material 2 is not deformed in this way, the contact area does not decrease as shown in FIG. 11B, and the frictional heat is concentrated at the portion where the contact area decreases, and the friction base material is removed. It is possible to suppress the constituent materials from being thermally degraded.

(2) Embodiment 2 (Three-layer core plate and wet friction material)
In the same manner as in the first embodiment, two annular plate layers 13 are obtained. These become the outer plate layers (the front plate layer 131 and the back plate layer 132) as in the case of the first embodiment.
On the other hand, one cut plate 62 is obtained from the metal plate 61 supplied in a rolled state, and is subjected to correction to obtain a corrected plate 63 (the plate 63 has a winding 69 latent. Get) The corrected plate material 63 is punched (a punching step) to obtain a middle plate layer 133 including four arc-shaped parts 139. The four arc-shaped parts 139 are formed so as to interpose the gap 15 when assembled into an annular shape.

  Next, the inner side surfaces (62a and 62b) in the wound state of each of the obtained two plate layers are arranged toward the center in the thickness direction (arrangement step), and four arc-shaped layers are formed between these layers. The parts 139 are grouped and arranged in an annular shape, and the respective layers are joined with a cured resin to obtain the core plate 1 (see FIGS. 3 and 4). At this time, of the four arc-shaped parts 139, two parts face the inner surface in the wound state toward the outside in the thickness direction, and two parts have the inner surface in the wound state toward the center in the thickness direction. , The uneven distribution of stress due to the middle plate layer 133 can be prevented.

The obtained core plate 1 (see FIGS. 3 and 4) becomes an annular core plate 1 having three plate layers 13 in the thickness direction. Two of the three layers are outer plate layers (a front plate layer 131 and a back plate layer 132), each of which is formed of one annular metal plate. The stresses caused by the latent winding of the outer layer are offset toward the center in the thickness direction and are restrained by the cured resin. Also, the middle plate layer 133 is assembled via the gap 15 and is sandwiched between outer plate layers (the front plate layer 131 and the back plate layer 132) and is joined by a cured resin. Then, the gap 15 of the middle plate layer 133 having four positions, an example of the inner circumferential side _{S I} and the outer _{S O} oil passage 15 penetrates into a _{(W SI} and _{W SO} transgressions Tohaba of the core plate 1 Is).
Then, the friction base material 3 is joined to the main surface 1c (both the front surface 1a and the back surface 1b) of the core plate 1 using a hardened resin to obtain a wet friction material 2 (see FIGS. 6 and 7).
Note that the thickness of each plate layer 13 (the front plate layer 131, the back plate layer 132, and the middle plate layer 133) can be, for example, 0.25 to 0.35 mm.

The wet friction material 2 thus obtained (see FIGS. 6 and 7) is supplied from the inner shaft side during use by having four oil passages 15 in addition to the same operation as the first embodiment. lubricating oil, as shown in FIG. 7, from the inner circumferential side S _I to the outer peripheral side S _O, it can be circulated through the oil passage 15. Thereby, cooling from the inside of the core plate 1 is promoted, and the heat cycle imposed on the wet friction material 2 can be reduced. By these actions, the deformation of the wet friction material 2 over time can be significantly suppressed. As a result, it is possible to suppress a decrease in friction characteristics, particularly a decrease in μ value. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed (see FIG. 9).

In the case where three plate layers 13 are provided, for example, a core plate 1 having a thickness of 0.9 mm in which three plate layers 13 having the same thickness of 0.3 mm are laminated (for example, a bonding layer having a total thickness of 0.1 mm) , The total thickness is 1 mm). That is, a core plate 1 having a thickness of 3X (mm) in which three plate layers 13 having the same thickness of X (mm) are laminated (when a bonding layer having a total of Z mm is provided, 3X + Zmm is obtained). .
Further, for example, in the case where three plate layers 13 are similarly provided, two plate layers 13 having the same thickness of 0.2 mm and a plate layer 13 having a thickness of 0.5 mm sandwiched between the two. Can be a core plate 1 having a thickness of 0.9 mm and a total thickness of 1 mm if a total of 0.1 mm bonding layers are provided. That is, 2X + Y (mm) in which two plate layers 13 of the same thickness of X (mm) and one plate layer 13 of the thickness of Y (mm) sandwiched therebetween are laminated. (In the case of having a total bonding layer of Z mm, it becomes 2X + Y + Z mm). When the middle plate layer 133 is thicker than the outer plate layer as in the latter case, the flow rate of the lubricating oil through the oil passage 15 can be increased, and the cooling effect can be improved.

In addition, although the outer plate layers (the front plate layer 131 and the back plate layer 132) have the spline internal teeth 8, the outer plate layers (the front plate layer 131 and the back plate layer 132) have the spline inner teeth. It is not necessary to have the teeth 8. That is, for example, when the middle plate layer 133 has sufficient rigidity to constitute the spline internal teeth 8 by itself, only the middle plate layer 133 has the spline internal teeth 8 and the outer plate layer (front side). The plate layer 131 and the back plate layer 132) may not have the spline internal teeth 8. In this case, the inner periphery of the outer plate layer (the front plate layer 131 and the back plate layer 132) is positioned at the root of the spline internal teeth 8 of the middle plate layer 133 or on the outer peripheral side S _O therefrom. An outer plate layer (a front plate layer 131 and a back plate layer 132) having an inner peripheral diameter larger than that of the plate layer 133 can be used.

(3) Embodiment 3 (four-layer core plate and wet friction material)
In the same manner as in the second embodiment, two integrated plate layers 13 each having a ring shape are obtained. These become the outer plate layers (the front plate layer 131 and the back plate layer 132) as in the case of the first embodiment.
On the other hand, two cut plate members 62 are obtained from the metal plate member 61 supplied in a rolled state, and are corrected and corrected. Get) The corrected plate material 63 is punched (a punching step) to obtain a two-layer middle plate layer 133 including six arc-shaped parts 139. The six arc-shaped parts 139 are formed so as to interpose the gap 15 when assembled in an annular shape.

  Next, the inner side surfaces (62a and 62b) in the wound state of each of the obtained two plate layers are arranged (arrangement step) toward the center in the thickness direction, and six arc-shaped portions are formed between these layers. The parts 139 are grouped and arranged in an annular shape, and the respective layers are joined with a cured resin to obtain the core plate 1. At this time, of the six arc-shaped parts 139, three of the parts have the inner surface in the wound state facing outward in the thickness direction, and the three parts have the inner surface in the wound state centered in the thickness direction. , The uneven distribution of stress due to the middle plate layer 133 can be prevented. Further, the two-layered arc-shaped parts 139 are arranged at different angles so that the gaps are arranged at intervals of 30 degrees, so that the gaps 15 can be provided at 12 places at an equal angle.

The obtained core plate 1 is an annular core plate 1 having four plate layers 13 in the thickness direction. Two of the four layers are outer plate layers (a front plate layer 131 and a back plate layer 132), each of which is formed of one annular metal plate. The stresses caused by the latent winding of the outer layer are offset toward the center in the thickness direction and are restrained by the cured resin. Further, the two middle plate layers 133 are assembled via the gap 15 and are sandwiched between outer plate layers (the front plate layer 131 and the back plate layer 132) and are joined by a cured resin. Then, the gap 15 of the six locations each intermediate plate layer 133 had (a total of 12 locations), the inner circumferential side _{S I} and the outer _{S O} and the penetrating oil passage 15 of the core plate 1 _{(W SI} and _{W SO} Are examples of equal width).
Thereafter, the friction base material 3 is joined to the main surface 1c (both the front surface 1a and the rear surface 1b) of the core plate 1 using a hardened resin to obtain a wet friction material 2 (see FIG. 8).
The thickness of each plate layer 13 (the front plate layer 131, the back plate layer 132, and the two middle plate layers 133) can be, for example, 0.20 to 0.35 mm.

The wet friction material 2 obtained in this manner (see FIG. 8) has lubricating oil supplied from the inner shaft side during use by having twelve oil passages 15 in addition to the same operation as the first embodiment. as shown in FIG. 8, from the inner circumferential side S _I to the outer peripheral side S _O, it can be circulated through the oil passage 15. Thereby, cooling from the inside of the core plate 1 is promoted, and the heat cycle imposed on the wet friction material 2 can be reduced. By these actions, the deformation of the wet friction material 2 over time can be significantly suppressed. As a result, it is possible to suppress a decrease in friction characteristics, particularly a decrease in μ value. Further, since a local increase in temperature due to frictional heat can be suppressed, heat resistance can be improved. Further, the initial pack clearance can be maintained for a long period of time, and the increase in drag torque accompanying the decrease in pack clearance can be suppressed (see FIG. 9).

In the case where four plate layers 13 are provided, for example, a core plate 1 having a thickness of 1.2 mm in which four plate layers 13 having the same thickness of 0.3 mm are laminated (for example, a bonding layer having a total thickness of 0.1 mm) , The total thickness is 1.3 mm). That is, a core plate 1 having a thickness of 4X (mm) in which four plate layers 13 of the same thickness of X (mm) are laminated (when a bonding layer having a total of Z mm is provided, 4X + Zmm is obtained). .
Further, for example, in the case where four plate layers 13 are similarly provided, two plate layers 13 having the same thickness of 0.2 mm and a plate layer 13 having a thickness of 0.4 mm sandwiched between the two. And a core plate 1 having a thickness of 1.0 mm (a total thickness of 1.1 mm if a total of 0.1 mm bonding layers are provided). That is, 2X + 2Y (mm) in which two plate layers 13 of the same thickness of X (mm) and two plate layers 13 of the thickness of Y (mm) sandwiched therebetween are laminated. (The total thickness is 2X + 2Y + Zmm when the bonding layer has a total thickness of Z mm). When the middle plate layer 133 is thicker than the outer plate layer as in the latter case, the flow rate of the lubricating oil through the oil passage 15 can be increased, and the cooling effect can be improved.

  In addition, although the outer plate layers (the front plate layer 131 and the back plate layer 132) have the spline internal teeth 8, the outer plate layers (the front plate layer 131 and the back plate layer 132) have the spline inner teeth. The fact that the teeth 8 need not be provided is the same as in the second embodiment.

Hereinafter, the present invention will be described by way of examples. The description common to each embodiment is omitted.
[1] Adjustment of wet friction material [Example 1]
(1) Core plate (see FIGS. 3 and 4)
The core plate 1 shown in FIGS. 3 and 4 was manufactured. Each layer is made of NCH780, has a thickness of 0.3 mm (total thickness of 0.9 mm), and each has spline teeth protruding from the inner peripheral surface. The ratio R ₁ / R ₂ between the outer diameter R ₁ and the inner diameter R ₂ of the core plate 1 is 1.10 (R ₁ = 158 mm, R ₂ = 144 mm). The oil passages 15 are provided at four positions at intervals of 90 degrees, and the opening width W _SI on the inner peripheral side and the opening width W _SO on the outer peripheral side of each oil passage 15 are both 1 mm.

(2) Wet friction material (see FIGS. 6 and 7)
Using the core plate 1 shown in (1) above, a wet friction material 2 shown in FIGS. 6 and 7 was obtained. The wet friction material 2 includes a core plate 1 and a friction substrate 3 joined to both main surfaces 1a. The friction substrates 3 each have a substantially trapezoidal shape, and a total of 80 sheets (40 on the front main surface and 40 on the back main surface) are equiangularly provided with each other. An oil groove 4 is provided between the friction bases 3.
The friction substrate 3 is made of a paper body obtained by forming a fiber substrate such as pulp and aramid fiber, a friction modifier such as cashew dust, and a filler such as diatomaceous earth. It is hardened after impregnation. Each friction substrate 3 is joined to the main surface 1a of the core plate 1 by heating under pressure.

[Comparative Example 1]
A core plate 1 'was produced. It is made of a single-layer annular NCH780 metal plate, has a thickness of 0.9 mm, and has spline teeth protruding from the inner peripheral surface. The ratio R _{1 /} R ₂ between the outer diameter R ₁ and the inner diameter R ₂ of the core plate 1 is the same as Example Product does not have an oil passage.
The friction substrate 3 was joined to the core plate 1 'in the same manner as in the example product to obtain a wet friction material 2'.

[2] Evaluation (1) Correlation between Number of Endurance Cycles and μd Value Three wet friction materials of the example product and the comparative example product of the above [1] are alternately arranged with four mating materials (plates). It was assembled on an inertial friction tester (SAE # 2). Then, the correlation between the engagement time and the torque required to engage the rotating wet friction material is determined by μ-V at each of 500, 1000, 1500, 2000, and 3000 times of engagement. It was obtained as a characteristic graph, and the dynamic friction coefficient μd value at each number of engagements was calculated from this graph. The results (numerical trends) are shown in the graph of FIG. In this graph, the number of endurance cycles corresponds to the number of engagements.
Input shaft rotation speed = 8000 rpm
Engagement surface pressure = 0.785 MPa
Moment of inertia = 0.245 kg · m ²
Lubricating oil (ATF) amount = 100 mL / min (axial lubrication)
Lubricating oil (ATF) temperature = 120 ° C
Pack clearance: 0.2 mm / sheet The μd value is a median value (dynamic friction coefficient in the middle of time) between μi (dynamic friction coefficient at the beginning of engagement) and μ0 (dynamic friction coefficient at the end point of engagement) in the μ-V characteristic graph. ).
In addition, automatic transmission lubricating oil (AutoAtic Transmission Fluid, “ATF” is a registered trademark of Idemitsu Kosan Co., Ltd., but hereafter abbreviated to “ATF” regardless of the registered trademark).

(2) Correlation between the number of endurance cycles and the amount of warpage of the core plate At each number of engagements in the above engagement test, the flatness of the core plate before and after each test was measured using a height gauge. The difference in flatness was defined as the amount of warpage (mm) of the core plate. The obtained results (numerical trends) are also shown in the graph of FIG.

(3) Correlation between the number of endurance cycles and the temperature of the core plate The temperature of the core plate was measured at each of the engagement times in the above engagement test. The obtained results (numerical trends) are also shown in the graph of FIG.

[3] Effect of Example As a result of the evaluation of the above [2], it can be seen that, in the comparative example, when the number of endurance cycles exceeds 1500, the amount of warpage of the core plate sharply increases. Further, it can be seen that the μd value is reduced as this tendency is accompanied. In addition, the temperature rise of the core plate is significantly increased at each endurance cycle number as compared with the example product, and it can be seen that the dissociation from the example product increases as the endurance cycle number increases.
On the other hand, in the example product as well, although the amount of warpage of the core plate increases when the number of endurance cycles is 1500 to 2000, the amount is 33.3% of that of the comparative example when the number of endurance cycles is 2000, It was suppressed as small as 23.3% of the comparative example. As a result, the warpage amount of the core plate increased 5.00 times in the comparative example between 500 and 3000 endurance cycles, while the example product was suppressed to 1.17 times.

  As with the tendency of the above-mentioned warping, the decrease in the μd value of the example product was suppressed to a small extent. That is, in the endurance cycle number of 1500 times, the comparative example product was reduced by 3.0% from the initial value, whereas the example product was suppressed by 1.5%. Similarly, at the endurance cycle number of 2000 times, the product of the comparative example was reduced by 14.8% from the initial value, while the product of the example was suppressed to be reduced by 2.9%. Further, in the number of endurance cycles of 3000, the product of the comparative example was reduced by 21.5% from the initial value, whereas the product of the example was suppressed by 3.7%. That is, the μd value of the comparative example product was reduced by 21.5% between 500 and 3000 endurance cycles, whereas the μd value of the example product was suppressed to 3.7%.

Furthermore, the temperature rise of the core plate in the example product was suppressed to be smaller than that in the comparative example product. In other words, the temperature of the core plate increased by 19.2% between the number of endurance cycles of 500 to 3000 in the comparative example, whereas the temperature of the core plate was suppressed to 8.0% in the example.
As for the parameters of the core plate warpage, the μd value, and the core plate temperature, the dissociation between the example product and the comparative product increased as the number of endurance cycles increased.
From the above, it can be seen that the core plate having a structure in which two or more plate layers 13 are stacked in the thickness direction can suppress the warpage of the core plate due to the hot cycle. As a result, it can be seen that a decrease in the μd value can be suppressed and a rise in the temperature of the core plate can be suppressed.

  It should be noted that the present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention according to the purpose and application.

  The application of the wet friction material of the present invention is not particularly limited, and is widely applied to, for example, automobiles (eg, four-wheeled vehicles, two-wheeled vehicles), railway vehicles, ships, airplanes, and the like. Among them, as an automotive article, it is suitably used for an automatic transmission (automatic transmission, AT). Although only one wet friction material may be used in the transmission, a plurality of wet friction materials may be used, but a plurality of the friction materials are preferably used. The greater the use of this wet friction material in one transmission, the greater the cumulative effect. That is, the drag torque can be reduced more effectively in a wet multi-plate clutch that uses a large number of wet friction materials.

1; core plate, 1 '; conventional core plate,
1a; front surface, 1b; back surface, 1c;
13; plate layer, 131; front plate layer, 132; back plate layer,
133: middle plate layer, 139: arc-shaped part,
15; gaps, oil passages,
2; wet friction material, 2 '; conventional wet friction material,
3; friction substrate, 4; oil groove,
5; separator plate (counterpart material),
61; rolled plate, 62; cut plate, 63; straightened plate, 69; latent winding
8; spline internal teeth,
P; rotation center,
R ₁ ; outer diameter,
R ₂ ; inner diameter,
S _I ; inner circumference side,
S _O ; outer peripheral side.

Claims (7)

A core plate for a wet friction material that forms an annular shape and is a wet friction material in which a friction base material is disposed on a main surface,
A core plate comprising two or more plate layers in a thickness direction. With three or more plate layers in the thickness direction,
Having two outer plate layers constituting the front and back surfaces, and at least one middle plate layer sandwiched between the two outer plate layers,
2. The core plate according to claim 1, wherein at least one of the middle plate layers is formed by a plurality of circular arc-shaped parts assembled in an annular shape. 3.   The core plate according to claim 2, wherein each of the two outer plate layers is formed of one annular metal plate. The arc-shaped parts are assembled via a gap,
4. The core plate according to claim 2, wherein the gap is an oil passage penetrating the inner peripheral side and the outer peripheral side of the core plate. 5.   The core plate according to any one of claims 2 to 4, wherein the outer plate layer and the middle plate layer are joined to each other via a cured resin. A core plate according to any one of claims 1 to 5,
A friction substrate disposed on a main surface of the core plate. It is a manufacturing method of the core plate in any one of Claims 1 thru | or 6, Comprising:
A punching step of punching a plate material obtained by unwinding the roll to obtain two annular plate layers;
A method of manufacturing a core plate, comprising: arranging the two plate layers obtained in the punching step into the following arrangement (1) or (2).
(1) The inner surface of each of the two plate layers in the wound state is directed toward the center in the thickness direction. (2) The inner surface of each of the two plate layers in the wound state. Are arranged outward in the thickness direction.

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