JP2009103308A - Wet-type friction material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To significantly shorten a manufacturing time by reducing a manufacturing process, while preventing generation of unnecessary polishing chips and cutting chips, by stabilizing an initial friction characteristic without performing initial running-in work, polishing and cutting, in a wet-type friction material. <P>SOLUTION: In this wet-type friction material 1, a ring-shaped friction material substrate 3 is compressed and fixed on a surface of core metal 2 by heat-pressing by manufacturing metal molds 4 and 5. Since a taper of an angle alpha corresponding to a taper on the outer peripheral side of an upper mold 4 is attached to the outer peripheral side of the ring-shaped friction material substrate 3, the taper is formed such that the thickness in the radial direction of the ring-shaped friction material substrate 3 becomes thin from a middle point in the radial direction toward the outer peripheral direction, without adding a new process to a conventional manufacturing process, and thus, an initial friction coefficient can be stabilized by smoothly engaging by a surface not by a line from the outer peripheral side of high torque when the ring-shaped wet-type friction material 1 engages with a disk. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

 The present invention relates to a wet friction material capable of stabilizing the initial friction characteristics of a wet friction material without using a polishing device or a cutting device, and a method for manufacturing the wet friction material, thereby preventing generation of unnecessary wear scraps and cutting scraps. The present invention relates to a wet friction material capable of significantly reducing time and a manufacturing method thereof.

 As a wet friction material for an automatic transmission, a ring-shaped friction material substrate cut out from a friction material substrate or a plurality of segment pieces is bonded to one or both surfaces of a flat ring metal core. Yes. These wet friction materials require a rotating lining surface (friction material base material surface) to be pressed against a disk or the like so that rotational force is transmitted, so that the friction coefficient of the lining surface is required to be stable. . Therefore, as shown in Patent Document 1, an initial leveling operation of a new wet friction material has been performed at the manufacturing stage in order to make the friction coefficient constant.

 However, since the initial leveling operation of the wet friction material is performed by incorporating the wet friction material and the disk in an apparatus similar to an actual product apparatus, it takes a considerable time until the desired friction coefficient is obtained. However, the manufacturing cost could not be reduced due to an increase in manufacturing steps and a delay in manufacturing time. Therefore, in the invention described in Patent Document 2, a polishing process in which the friction surface of the ring-shaped friction material is polished by a polishing surface comprising a flat surface and a plurality of grooves formed on the flat surface. Disclosed is a wet friction material.

 In the wet friction material described in Patent Document 2, the friction surface is polished by a polishing surface composed of a flat surface and a plurality of grooves formed on the flat surface, so that unnecessary polishing is not performed. It is said that rapid initial leveling is possible and manufacturing time can be shortened. In the invention described in Patent Document 3, the surface of the friction material used in the lock-up clutch is cut to obtain a wet friction material that can obtain stable friction characteristics from the beginning of use.

 However, the techniques described in Patent Document 2 and Patent Document 3 also require a polishing process or a cutting process that is shorter than the initial leveling operation during the manufacturing process. There has been a problem that unnecessary polishing scraps and cutting scraps are generated in the cutting process.

Therefore, in the invention described in Patent Document 4, the thickness of the ring-shaped wet friction facing provided on the outer peripheral side of the piston of the lockup clutch is reduced from the radially outer peripheral side toward the inner peripheral side. In addition to the tapered surface, the density on the outer peripheral side in the radial direction of the wet friction facing is made smaller than that of other portions. Alternatively, a taper surface is formed on the radially outer peripheral side of the fixed surface of the wet friction facing of the piston along the slope of the friction surface facing the wet friction facing, and the radially outer peripheral portion of the wet friction facing is fixed. Tapered surface corresponding to the surface. As a result, the μ-V characteristic of the lock-up clutch is improved, and the occurrence of judder during slip control can be suppressed.
Japanese Examined Patent Publication No. 6-37909 Japanese Patent Laid-Open No. 11-193841 JP 2003-231043 A Japanese Patent Laid-Open No. 2004-11710

 However, in the technique described in Patent Document 4 described above, when the density on the radially outer peripheral side of the wet friction facing is tapered so as to be smaller than other portions, the radially inner peripheral side of the wet friction facing is provided. Even when the pressure of the friction surface facing the wet friction facing increases because the strength of the wet friction facing increases, it becomes difficult for the entire surface of the wet friction facing to adhere to the facing friction surface. In addition, when a taper is provided on the outer peripheral side in the radial direction of the fixed surface, there is a problem that the entire piston has to be manufactured separately from a normal piston.

 Therefore, the present invention can stabilize the initial friction characteristics of the wet friction material without initializing work, polishing or cutting, thereby preventing generation of unnecessary polishing scraps and cutting scraps as well as normal flat plates. An object of the present invention is to provide a wet friction material that can use a ring-shaped metal core as it is, and can reduce the manufacturing process and significantly reduce the manufacturing time, and a method for manufacturing the wet friction material.

The manufacturing method of the wet friction material according to the invention of claim 1 is a wet friction material that requires close contact with the outer peripheral portion of the friction surface, and is provided on one side of a flat ring metal core provided on the outer peripheral side of the piston of the lockup clutch or A method for producing a wet friction material obtained by bonding and fixing a ring-shaped friction material substrate or a plurality of segment pieces cut from a friction material substrate on both surfaces, the ring-shaped friction material substrate or the plurality of segments. When the piece is bonded and fixed to the flat ring-shaped cored bar, the ring-shaped friction material substrate or the plurality of the plurality of ring-shaped friction material bases are simultaneously heated and pressed with a die having a tapered shape corresponding to the friction surface in the radial direction. Forming a taper shape that linearly changes the thickness of the segment piece in the radial direction so as to be thin so as to correspond to the friction surface over the entire length in the radial direction A. And the radial thickness of the ring-shaped friction material substrate or the plurality of segment pieces other than the portion that is linearly changed from the middle in the radial direction is constant.
Further, the resin / fibers present in the ring-shaped friction material substrate or the extreme surface layer portion of the plurality of segment pieces are heated by laser light, from the depth from the surface to 1 μm to the thickness from the surface to 15 μm. It is carbonized within the range of the depth.

 The manufacturing method of the wet friction material according to the invention of claim 1 is a wet friction material that requires close contact with the outer peripheral portion of the friction surface, and is a ring shape cut out from the friction material base on one or both sides of a flat plate ring-shaped cored bar. A method of manufacturing a wet friction material by bonding and fixing a friction material substrate or a plurality of segment pieces, wherein the ring-shaped friction material substrate or the plurality of segment pieces are bonded and fixed to a flat ring metal core At the same time, the radial thickness of the ring-shaped friction material substrate or the plurality of segment pieces is extended over the entire length in the radial direction by heating and pressing with a die having a tapered shape corresponding to the friction surface in the radial direction. A taper shape that linearly changes so as to become thin so as to correspond to the friction surface is formed.

As a result, in the conventional planar friction material base material, only the corner portion of the outer peripheral end surface first contacts the counterpart material, so that smooth engagement was not obtained, but the method for producing the wet friction material according to the present invention The wet friction material manufactured in the above method has a taper that is substantially the same as the friction surface of the mating material on the surface of the ring-shaped friction material substrate or the friction material substrate of a plurality of segment pieces. The entire surface of the part comes into contact with the surface of the mating member, and an extremely smooth engagement can be obtained.
Thus, since the entire surface of the tapered portion is engaged with the surface of the counterpart material from the beginning, a stable initial friction coefficient can be obtained. The process of tapering the surface of the ring-shaped friction material substrate or the friction material substrate of a plurality of segment pieces is performed simultaneously with the step of crimping and fixing the friction material substrate to the surface of the core metal. There is no need to provide it, and the conventional initial leveling work, polishing process and cutting process can be omitted, so that the manufacturing process can be reduced and the manufacturing time can be greatly shortened. In addition, since the maximum crushing margin on the outer peripheral side is as small as 5/100 or less, the taper size does not change the density of the friction material base, and a normal flat ring metal core is used. be able to.

In this way, the initial friction characteristics of the wet friction material can be stabilized without initial leveling work, polishing or cutting, thereby preventing generation of unnecessary polishing scraps and cutting scraps. It becomes a manufacturing method of the wet friction material which can use a metal core as it is, and can aim at the significant shortening of manufacturing time by reducing a manufacturing process.
The radial thickness of the ring-shaped friction material substrate or the plurality of segment pieces other than the portion that is linearly changed from the middle in the radial direction is constant. Accordingly, it is not necessary to apply excessive pressure in the step of forming a taper shape or an R shape on the surface of the friction material base of the ring-shaped friction material or the plurality of segment pieces, thereby extending the life of the manufacturing mold. At the same time, it saves manufacturing energy.

Furthermore, the resin / fiber existing in the ring-shaped friction material base or the extreme surface layer portion of the plurality of segment pieces is heated by laser light, and the depth from the surface to a thickness of 1 μm to the thickness from the surface to 15 μm. Carbonize within the depth range.
As a result, the light intensity of the laser light is stable, and fine adjustment of the light intensity can be easily performed. It is possible to carbonize uniformly by the thickness. Then, by carbonizing the extreme surface layer portion, the effect of improving the μ-V positive gradient property as a wet friction material can be obtained. Here, if the portion to be carbonized is less than the depth from the surface to a thickness of 1 μm, the effect of improving the μ-V positive gradient is hardly obtained, and the portion to be carbonized has a thickness from the surface to 15 μm. If the depth is exceeded, the carbonized layer of the extreme surface layer will peel off.
In this way, the initial friction characteristics of the wet friction material can be stabilized without initial leveling work, polishing or cutting, thereby preventing generation of unnecessary polishing scraps and cutting scraps. In this way, the manufacturing method of the wet friction material can be used as it is, the manufacturing process can be reduced, the manufacturing time can be greatly shortened, and the μ-V positive gradient property is improved.

 Hereinafter, a wet friction material and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS.

 FIG. 1 is a cross-sectional view schematically showing the overall configuration of a wet friction material and a manufacturing apparatus according to an embodiment of the present invention. FIG. 2A is a longitudinal sectional view showing a cross-sectional shape of a ring-shaped friction material substrate of a wet friction material according to Reference Example 1 of the embodiment of the present invention, and FIG. 2B is an example of the embodiment of the present invention. The longitudinal cross-sectional view which shows the cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning (c) is a cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning the reference example 2 of embodiment of this invention (D) is a longitudinal cross-sectional view which shows the cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning the reference example 3 of embodiment of this invention.

 FIG. 3A is a graph showing initial friction characteristics of a wet friction material having a uniform ring-shaped friction material base material, and FIG. 3B is an initial friction characteristic of the wet friction material according to the embodiment of the present invention. It is a graph which shows. FIG. 4 compares the variation in the initial friction coefficient μ of the wet friction material according to the embodiment of the present invention with the variation in the initial friction coefficient μ of the wet friction material having a uniform thickness of the conventional ring friction material base. It is a bar graph to show. FIG. 5A is a partial cross-sectional view showing a state in which the wet friction material according to Reference Example 1 of the embodiment of the present invention is in contact with the counterpart material, and FIG. 5B is the maximum pressure applied to the counterpart material. It is a fragmentary sectional view showing a state.

 FIG. 6 is a schematic diagram showing the relationship between the taper width x and the taper height y of the ring-shaped friction material base material of the wet friction material according to Reference Example 1 of the embodiment of the present invention. FIG. 7A is a graph showing variations in the taper width x of the ring-shaped friction material base material of the wet friction material according to the conventional manufacturing method, and FIG. 7B is based on the wet friction material manufacturing method according to the embodiment of the present invention. The graph which shows the dispersion | variation in the taper width x of the ring-shaped friction material base material of a wet friction material, (c) is a graph which shows the dispersion | variation in the taper height y by the conventional manufacturing method, (d) is embodiment of this invention. It is a graph which shows the dispersion | variation in the taper height y by the manufacturing method of this wet friction material.

 As shown in the sectional view of FIG. 1, the wet friction material 1 according to the present embodiment is a ring-shaped wet friction material in which a ring-shaped friction material base material 3 is bonded and fixed to the surface of a flat ring metal core 2. The dashed-dotted line in FIG. 1 represents the rotation center axis of the ring-shaped wet friction material 1 and the rotation center axis of the production dies 4 and 5 of the wet friction material 1. A ring-shaped friction material base material 3 is placed on the surface of a flat plate ring-shaped core metal 2 coated with an adhesive, and the ring-shaped friction material base material 3 is attached to the core metal 2 using manufacturing dies 4 and 5. The process of crimping and fixing to the surface is the same as the manufacturing process of the conventional ring-shaped wet friction material.

 The difference is that in the wet friction material 1 according to the present embodiment, a taper is provided on the outer peripheral side of the upper mold 4 among the manufacturing molds 4 and 5, and the upper mold of the manufacturing molds 4 and 5. 4 and the lower die 5 are pressed at a surface pressure of 20 kgf / cm 2 to 30 kgf / cm 2 and heated to 220 ° C. to 230 ° C. As a result, the ring-shaped friction material base 3 is pressure-bonded and fixed to the surface of the core metal 2, and a taper having an angle α corresponding to the taper on the outer peripheral side of the upper mold 4 is formed on the outer peripheral side of the ring-shaped friction material base 3. Will be attached.

 The taper angle α is as small as about 0.3 degrees in the wet friction material 1 according to the present embodiment, but in each drawing including FIG. The figure is greatly emphasized. And the crushing allowance of the ring-shaped friction material base material 3 is set to 5/100 or less also in the largest part of the outermost periphery of the ring-shaped friction material base material 3.

 In this way, the ring-shaped friction material base 3 is simultaneously added to the surface of the core metal 2 by pressure bonding without adding a new process to the conventional manufacturing process of the ring-shaped wet friction material. Since the taper is formed by linearly changing the thickness in the radial direction from the middle in the radial direction toward the outer circumferential direction, compared to the conventional manufacturing method that performs initial leveling work, polishing process and cutting process Thus, the manufacturing method of the wet friction material 1 can be greatly shortened.

 As shown in FIG. 1, since the taper is formed so that the radial thickness of the ring-shaped friction material base material 3 becomes thinner from the middle in the radial direction toward the outer circumferential direction, the ring-shaped wet friction is obtained. When the material 1 is engaged with the disc, the initial friction coefficient can be stabilized by smoothly engaging with the surface instead of the line from the outer peripheral side where the torque is high. Here, it is necessary to change how the taper is attached depending on the shape of the mating material to be engaged. Then, the taper of the ring-shaped friction material base material in the wet friction material 1 concerning this Embodiment is demonstrated with reference to FIG.

 FIG. 2A shows a reference example of this embodiment in which a taper is formed by linearly changing the thickness in the radial direction from the middle in the radial direction toward the outer circumferential direction, as shown in FIG. 1 shows a cross-sectional shape of a ring-shaped friction material substrate 3 according to FIG. FIG. 2B shows a ring-shaped friction material base material according to an example of the present embodiment in which a taper whose thickness decreases linearly from the inner peripheral side toward the outer peripheral side over the entire length in the radial direction is shown. The cross-sectional shape of 3B is shown. FIG. 2C shows a reference example 2 of the present embodiment in which a taper is formed such that the thickness increases linearly from the inner peripheral side toward the outer peripheral side over the entire length in the radial direction, contrary to the example. The cross-sectional shape of the ring-shaped friction material base material 3C which concerns on is shown.

 FIG. 2D shows an example 3 of the present embodiment in which the R shape is formed by changing the thickness in the radial direction so as to become thinner from the middle in the radial direction toward the outer circumferential direction. The cross-sectional shape of the ring-shaped friction material substrate 3D is shown. Here, except for the ring-shaped friction material base material 3C according to Reference Example 2 in which a taper in which the thickness is linearly increased from the inner peripheral side toward the outer peripheral side is used, all of them are from the inner peripheral side toward the outer peripheral side. Since the thickness is linearly or curvilinearly thinned, a disk that protrudes linearly from the inner circumference side to the outer circumference side as a conventional material used (projection angle = α) On the other hand, it has the effect of engaging smoothly.

 On the other hand, in the ring-shaped friction material base material 3C according to Reference Example 2 in which the taper is linearly increased from the inner peripheral side toward the outer peripheral side, the outer peripheral member is different from the counterpart material conventionally used. This has the effect of smoothly engaging the disc that protrudes linearly from the side toward the inner peripheral side.

 Therefore, the conventional ring-shaped wet friction material bonded with a flat ring-shaped friction material substrate and the ring-shaped friction material substrates according to Reference Example 1, Example, and Reference Example 3 of this embodiment are bonded. The ring-shaped wet friction material was pressed against a disk as a counterpart material at a pressure of 200 kPa, and the change in the friction coefficient μ was measured while increasing the rotation speed, and this was repeated ten times continuously. The result is shown in FIG.

 FIG. 3A shows a measurement result of a ring-shaped wet friction material in which a conventional planar ring-shaped friction material substrate is bonded, and FIG. 3B shows a ring shape according to Reference Example 1 of the present embodiment. It is a measurement result about the ring-shaped wet friction material which adhere | attached what irradiated the laser beam to the surface of the friction material base material 3. FIG. The surface of the ring-shaped friction material base material 3 according to Reference Example 1 is irradiated with laser light in advance in order to improve compatibility with a disk as a counterpart material in the same manner as in the present invention. The same effect was also obtained for the ring-shaped wet friction material obtained by bonding the ring-shaped friction material substrate 3 according to Reference Example 1 in which the surface of No. 3 was heated but the laser beam was not irradiated.

 Here, the resin / fiber existing in the extreme surface layer portion of the ring-shaped friction material base 3 is heated by the laser light irradiation, and the depth range from the depth from the surface to 1 μm to the depth from the surface to 15 μm. It is carbonized within. Thereby, the effect that the μ-V positive gradient property of the ring-shaped wet friction material 1 is improved is obtained. Since the laser light has a stable light intensity and fine adjustment of the light intensity can be easily performed, the resin / fiber existing in the extreme surface layer portion of the ring-shaped friction material base 3 is uniformly carbonized to an arbitrary thickness. It is possible to

 As shown in FIG. 3A, in the conventional flat ring-shaped friction material base material, the friction coefficient μ changes greatly while repeating the frictional rotation 10 times, but FIG. As shown in FIG. 2, the width of the change in the friction coefficient μ is small in the case where the surface of the ring-shaped friction material substrate 3 according to Reference Example 1 is irradiated with laser light. FIG. 4 shows the results of measuring the rate of change of the friction coefficient μ at a rotation speed of 50 rpm. As shown in FIG. 4, compared to the conventional flat ring-shaped friction material base material, the ring-shaped friction material base materials 3, 3B according to Reference Example 1, Example, and Reference Example 3 of the present embodiment. 3D, the rate of change of the friction coefficient μ is much smaller, and it is clear that the initial friction coefficient is stable.

 The reason why the initial friction coefficient of the ring-shaped wet friction material bonded with the ring-shaped friction material substrate according to the present embodiment is stable will be described with reference to FIG. As shown in FIG. 5A, the ring-shaped wet friction material 1 according to Reference Example 1 of the present embodiment is initially pressed against a disk 10 as a counterpart material at a low pressure. Projecting linearly from the outer periphery to the outer peripheral side (actually, the projecting angle = α = 0.3 degrees is smaller than that shown in the figure), so that in the conventional planar ring-shaped friction material base, the outer peripheral corner portion Only hit, and a smooth engagement could not be obtained.

 However, in the ring-shaped wet friction material 1 according to Reference Example 1 of the present embodiment, the thickness in the radial direction of the ring-shaped friction material base material 3 is such that the taper angle = α = 0.3 degrees from the middle. Since it is set, as shown in FIG. 5A, the right side surface of the disk 10 uniformly contacts the outer peripheral surface, so that smooth engagement can be obtained. When the pressing pressure is gradually increased, the flexible ring-shaped friction material base material 3 is deformed into a shape along the right side surface of the disk 10, and the disk 10 is formed on the entire surface of the ring-shaped friction material base material 3. It is possible to efficiently transmit the rotational force by engaging with the right side surface.

 Next, design criteria for the ring-shaped friction material base material 3 used for the ring-shaped wet friction material 1 according to Reference Example 1 of the present embodiment will be described with reference to FIG. As a design standard, the target size of the shape is set in consideration of the mechanism at the time of engagement and the density distribution of the ring-shaped friction material base 3. As shown in FIG. 6, when the length in the radial direction of the ring-shaped friction material substrate 3 is X and the maximum thickness is Y, the taper width x is 28% to 50% of the radial length X, and the taper height is high. The upper mold 4 of the manufacturing molds 4 and 5 is designed so that the thickness y is 5% or less of the maximum thickness Y.

 This is because if the taper height y exceeds 5% of the maximum thickness Y, the ring-shaped friction material base material 3 is compressed too much and the density becomes too high. The taper width x is the taper height y. On the other hand, since it is set so as to match the angle of the mating material with which the ring-shaped wet friction material 1 is engaged, it is 28% to 50% of the radial length X.

 Next, regarding the accuracy in taper processing of the ring-shaped friction material base material 3, the taper processing method by cutting according to the prior art and the taper processing method by heating and pressurization according to the present embodiment are compared, referring to FIG. explain. As shown in the left half of FIGS. 7 (a) and 7 (c), in the taper processing method by cutting according to the prior art, both the taper width x and the taper height y are sharply cut while the cutting jig is new. However, the variation is extremely large. As shown in the right half of FIGS. 7 (a) and 7 (c), when the cutting jig is consumed, it becomes impossible to cut, so both the taper width x and the taper height y are greatly below the target dimensions. I'm stuck.

 On the other hand, as shown in FIGS. 7B and 7D, in the taper processing method by heating and pressurization according to the present embodiment, both the taper width x and the taper height y have small variations. The dimensions (taper width x = 5 mm, taper height y = 0.04 mm) are always almost satisfied. Therefore, the conventional construction method not only requires frequent replacement of the cutting jig, but also the accuracy of the obtained product is not stable, whereas the method for manufacturing the wet friction material according to the present embodiment is not obtained. The accuracy of the manufactured product is stable, the manufacturing mold can be used semipermanently, and the cost can be reduced without the need to increase the manufacturing process.

 Thus, in the wet friction material 1 and the manufacturing method thereof according to the present embodiment, the initial friction characteristics of the wet friction material can be stabilized without initializing work, polishing, or cutting. While preventing generation | occurrence | production of an unnecessary grinding | polishing waste and cutting waste, a manufacturing process can be reduced and manufacturing time can be reduced significantly.

 In the present embodiment, the case where the taper width x = 5 mm and the taper height y = 0.04 mm has been described, but this value is appropriately set depending on the protrusion angle of the mating material with which the wet friction material 1 is engaged. Needless to say. Moreover, in this Embodiment, although the case where the ring-shaped friction material base material 3 cut out from the friction material base material was adhere | attached and fixed to the single side | surface of the flat ring-shaped cored bar 2 was demonstrated, the flat ring-shaped cored bar 2 Similar effects can be obtained with the ring-shaped friction material base material 3 bonded and fixed to both sides of the same.

 Further, in the present embodiment, the case of the ring-shaped wet friction material 1 in which the ring-shaped friction material base material 3 is bonded and fixed to the flat ring metal core 2 is described. In the segment wet friction material in which a plurality of segment pieces cut out from the material base material are bonded and fixed, the same configuration can be taken and the same effect can be obtained.

 In the present embodiment, the case where the ring-shaped friction material base material 3 is pressure-bonded and fixed to the surface of the core metal 2 at a surface pressure of 20 kgf / cm 2 to 30 kgf / cm 2 and a temperature of 220 ° C. to 230 ° C. has been described. The pressure and heating temperature are optimally set depending on the composition and thickness of the friction material base material, the type of adhesive, and the like.

 In carrying out the present invention, the configuration, shape, material, thickness, size, quantity, connection relationship, etc. of other parts of the wet friction material, and other processes of the wet friction material manufacturing method, The present invention is not limited to this embodiment.

 In addition, since the numerical value quoted in the embodiment of the present invention does not indicate a critical value but indicates a preferable value suitable for implementation, even if the numerical value is slightly changed, the implementation is denied. is not.

FIG. 1 is a cross-sectional view schematically showing the overall configuration of a wet friction material and a manufacturing apparatus according to an embodiment of the present invention. FIG. 2A is a longitudinal sectional view showing a cross-sectional shape of a ring-shaped friction material substrate of a wet friction material according to Reference Example 1 of the embodiment of the present invention, and FIG. 2B is an example of the embodiment of the present invention. The longitudinal cross-sectional view which shows the cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning (c) is a cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning the reference example 2 of embodiment of this invention (D) is a longitudinal cross-sectional view which shows the cross-sectional shape of the ring-shaped friction material base material of the wet friction material concerning the reference example 3 of embodiment of this invention. FIG. 3A is a graph showing initial friction characteristics of a wet friction material having a uniform ring-shaped friction material base material, and FIG. 3B is an initial friction characteristic of the wet friction material according to the embodiment of the present invention. It is a graph which shows. FIG. 4 compares the variation in the initial friction coefficient μ of the wet friction material according to the embodiment of the present invention with the variation in the initial friction coefficient μ of the wet friction material having a uniform thickness of the conventional ring friction material base. It is a bar graph to show. FIG. 5A is a partial cross-sectional view showing a state in which the wet friction material according to Reference Example 1 of the embodiment of the present invention is in contact with the counterpart material, and FIG. 5B is the maximum pressure applied to the counterpart material. It is a fragmentary sectional view showing a state. FIG. 6 is a schematic diagram showing the relationship between the taper width x and the taper height y of the ring-shaped friction material base material of the wet friction material according to Reference Example 1 of the embodiment of the present invention. FIG. 7A is a graph showing variations in the taper width x of the ring-shaped friction material base material of the wet friction material according to the conventional manufacturing method, and FIG. 7B is based on the wet friction material manufacturing method according to the embodiment of the present invention. The graph which shows the dispersion | variation in the taper width x of the ring-shaped friction material base material of a wet friction material, (c) is a graph which shows the dispersion | variation in the taper height y by the conventional manufacturing method, (d) is embodiment of this invention. It is a graph which shows the dispersion | variation in the taper height y by the manufacturing method of this wet friction material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wet friction material 2 Core metal 3, 3B, 3C, 3D Ring-shaped friction material base material

Claims (1)

A ring-shaped friction material base material, which is a wet friction material that requires close contact with the outer peripheral portion of the friction surface, cut out from the friction material base material on one or both sides of a flat ring metal core provided on the outer peripheral side of the piston of the lock-up clutch Or a method for producing a wet friction material formed by bonding and fixing a plurality of segment pieces,
The thickness of the ring-shaped friction material substrate or the plurality of segment pieces in the radial direction is the largest on the outer peripheral side where the thickness decreases linearly from the inner peripheral side to the outer peripheral side over the entire length in the radial direction. A taper with a crushing margin of 5/100 or less is formed, and the resin / fibers present in the extreme surface layer portion of the ring-shaped friction material substrate or the plurality of segment pieces are heated by laser light to increase the thickness from the surface. A method for producing a wet friction material, characterized by carbonizing within a depth range of 1 μm to 15 μm.

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