Dry friction material, torque limiting device, and method for manufacturing dry friction material

Abstract

The present invention provides a dry friction material in which the friction coefficients (μ) of the surface and the back can be easily made different, a torque limiting device using the dry friction material, and a manufacturing method for the dry friction material. The dry friction material 1 is installed on the surface of a plate 6 in a torque limiting device 5, and includes a reinforcing fiber 12 and a vulcanized rubber 11. The dry friction material 1 has an anti-slip portion 111 including carbide at a contact surface 1A in contact with the surface of the plate 6. The anti-slip portion 111 is formed by locally applying a heat treatment to the contact surface 1A of the dry friction material 1 to carbonize the vulcanized rubber 11 of the surface layer of the contact surface 1A.

Description

Technical Field

[0001] This invention relates to dry friction materials, dry friction materials, torque limiting devices, and fixing structures for dry friction materials. Background Technology

[0002] Vehicles such as hybrid vehicles are equipped with torque limiting devices that provide stable torque transmission and torque suppression when excessive torque is generated (i.e., unit protection). The torque limiting device includes an annular plate on which dry friction material is mounted. Inside the torque limiting device, the dry friction material abuts against the plate it is rubbing. When transmitting torque, the friction generated by the dry friction material on its surface causes the plate and the plate to move in tandem. Furthermore, when suppressing torque, the dry friction material slides its surface relative to the plate, causing the plate to slide.

[0003] Dry friction material is mounted on a plate by engaging a hole on its back surface with a pin on the mounting surface of the plate. If the dry friction material slides relative to the plate when transmitting or suppressing torque, the force applied by the plate via the pin is borne only by the hole, which can lead to breakage of the dry friction material. To prevent such breakage, it is desirable to increase the coefficient of friction (μ) of the back surface of the dry friction material to suppress sliding of the back surface relative to the mounting surface of the plate.

[0004] Therefore, for dry friction materials in torque limiting devices, it is necessary to have different coefficients of friction (μ) on the surface and the back surface so that the surface can slide relative to the plate being rubbed while the back surface does not slide relative to the plate. As an example of such a dry friction material capable of achieving different coefficients of friction (μ) on the surface and the back surface, the dry friction material described in Patent Document 1 can be cited.

[0005] Patent Document 1 describes a dry friction material that is a flat, annular dry friction material containing glass fibers, a synthetic resin for impregnating the glass fibers, and compounded rubber. The glass fiber content and compounded rubber content at the fixed portion of the dry friction material and at other locations are varied. This dry friction material is manufactured by moving the glass fibers, or those at the fixed portion and other locations, in one direction during a molding process that forms a pre-molded article of mating materials into a circle, thereby increasing the glass fiber content or compounded rubber content at the fixed portion.

[0006] Patent documents Patent document 1: WO2012 / 014535. Summary of the Invention

[0007] Specifically, in the technology disclosed in Patent Document 1, a stamping metal die with ribs (protrusions) protruding towards the molding body side (friction surface side) is used to press and mold the preform under high pressure. The ribs push the glass fibers to move in one direction, thereby causing the glass fibers to be unevenly distributed, resulting in differences in the glass fiber content and the composite rubber content.

[0008] However, in dry friction materials based on the above technology, since grooves are formed in the ribs of the stamping metal mold, it is easy to cause adverse conditions such as increased resistance to demolding from the metal mold, reduced demolding performance, and decreased flatness of the surface and back. This requires complicated operations such as shape correction and flatness improvement through grinding.

[0009] The present invention was made in view of the above-mentioned actual situation, and its object is to provide a dry friction material that can easily make the coefficients of friction (μ) of the surface and the back surface different, a torque limiting device using the dry friction material, and a method for manufacturing the dry friction material.

[0010] This invention includes the following inventions.

[0011] (1) A dry friction material, which is a dry friction material installed on the surface of a plate in a torque limiting device, characterized in that, Includes reinforcing fibers and vulcanized rubber. The contact surface that contacts the aforementioned surface of the plate has an anti-slip portion containing carbides.

[0012] (2) The dry friction material as described in (1) above, wherein the carbide is derived from the vulcanized rubber.

[0013] (3) The dry friction material as described in (1) or (2) above, wherein the contact surface is flat.

[0014] (4) The dry friction material described in any of (1) to (3) above, wherein the reinforcing fibers are composed of short fibers and oriented in a certain direction.

[0015] (5) The dry friction material as described in (4) above, wherein the shape of the dry friction material is an annular flat plate, and the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

[0016] (6) The dry friction material as described in (4) above, wherein the shape of the dry friction material is a fan-shaped flat plate, and the orientation of the reinforcing fiber is parallel to the outer edge of the arc-shaped dry friction material.

[0017] (7) The dry friction material as described in (4) above, wherein the shape of the dry friction material is a button-shaped plate, and the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

[0018] (8) A torque limiting device comprising a dry friction material as described in any one of (1) to (7) above, and a plate on which the dry friction material is mounted, characterized in that, The plate has multiple fixed-shape portions on the mounting surface on which the dry friction material is mounted, and the dry friction material has fixed-shape portions that engage with the fixed-shape portions.

[0019] (9) The torque limiting device as described in (8) above, wherein the dry friction material comprises short fibers oriented in a certain direction as the reinforcing fibers.

[0020] (10) The torque limiting device as described in (8) or (9) above, wherein, The shape of the mounting surface of the aforementioned plate when viewed from above is annular. The aforementioned dry friction material is in the shape of a ring-shaped flat plate. The aforementioned dry friction material has the same number of the aforementioned fixed shape portions as the aforementioned fixed shape portions. One of the aforementioned dry friction materials is fixed in a concentric circle to one of the aforementioned mounting surfaces of the aforementioned plate.

[0021] (11) The torque limiting device as described in any of (8) to (10) above, wherein, The shape of the mounting surface of the aforementioned plate when viewed from above is annular. The aforementioned dry friction material is in the shape of a fan-shaped flat plate. The aforementioned dry friction material has the aforementioned fixed shape at both ends. One of the aforementioned dry friction materials is secured to multiple of the aforementioned fixed shape portions by the aforementioned fixed shape portion, and multiple of the aforementioned dry friction materials are secured to one of the aforementioned mounting surfaces of the aforementioned plate.

[0022] (12) The torque limiting device as described in any of (8) to (11) above, wherein, The shape of the mounting surface of the aforementioned plate when viewed from above is annular. The aforementioned dry friction material is in the shape of a button-shaped flat plate. The aforementioned dry friction material has the aforementioned fixed shape portion at its center. One of the aforementioned dry friction materials is fixed to one of the aforementioned fixed shape parts through the aforementioned fixed shape part, and a plurality of the aforementioned dry friction materials are fixed on one of the aforementioned mounting surfaces of the aforementioned plate.

[0023] (13) The torque limiting device as described in (8) above, wherein, The aforementioned plates are cover plates and pressure plates. The cover plate and the push plate are configured such that the mounting surfaces on which the dry friction material is mounted are opposite each other. The friction plate is disposed between the cover plate and the push plate in a state of contact with the aforementioned dry friction material.

[0024] (14) A method for manufacturing a dry friction material as described in any one of (1) to (7) above, characterized in that it includes a step of applying local heating treatment to the contact surface of the dry friction material to carbonize the vulcanized rubber on the surface of the contact surface, thereby forming the anti-slip part.

[0025] (15) The method for manufacturing dry friction material as described in (14) above, wherein the local heating treatment is laser treatment.

[0026] (16) A method for manufacturing a dry friction material as described in (14) or (15) above, comprising: a step of extruding a compound of uncured rubber forming the above-described vulcanized rubber and the above-described reinforcing fiber to obtain a composition for friction materials; and, The process involves filling the cavity of a metal mold with the above-mentioned friction material composition and then vulcanizing it to obtain the above-mentioned dry friction material having a skin layer formed on the surface in contact with the wall of the cavity.

[0027] According to the dry friction material of the present invention, since the contact surface of the torque limiting device in contact with the plate surface has an anti-slip part containing carbides, it is easy to make the coefficient of friction (μ) of the front and back surfaces different.

[0028] According to the method for manufacturing dry friction material of the present invention, an anti-slip portion can be provided by applying local heating treatment to the contact surface of the dry friction material, which can eliminate the complicated operations previously required, such as operations related to shape correction and operations related to improving flatness by grinding. Therefore, it is easy to make the coefficient of friction (μ) of the surface and the back surface different. Attached Figure Description

[0029] Figure 1 A transverse cross-sectional view illustrating the dry friction material of the present invention; Figure 2 To illustrate the dry friction material of Example 1, (a) represents a top view, (b) represents a bottom view, (c) represents a top sectional view, and (d) represents a transverse sectional view along line dd in (a). Figure 3To illustrate the dry friction material of Example 2, (a) shows a top view after partial cross-section, and (b) shows a bottom view; Figure 4 To illustrate the dry friction material of Example 3, (a) represents a top view, (b) represents a top sectional view, and (c) represents a bottom view; Figure 5 A longitudinal sectional view is shown in the assembled state to illustrate the torque limiting device. Figure 6 To illustrate the plate of the torque limiting device in Embodiment 1, (a) shows a top view and (b) shows a longitudinal sectional view along line bb in (a). Figure 7 To illustrate the torque limiting device of Embodiment 1, a perspective view in an exploded state is shown. Figure 8 To illustrate the schematic diagram of the plate of the torque limiting device in Embodiment 2, (a) shows a top view and (b) shows a longitudinal sectional view along line bb of (a). Figure 9 To illustrate the schematic diagram of the plate of the torque limiting device in Embodiment 3, (a) shows a top view and (b) shows a longitudinal sectional view along line bb in (a). Figure 10 The schematic diagrams (a) to (h) illustrate the shape and configuration of the anti-slip parts in the contact surface of dry friction materials. Detailed Implementation

[0030] The present invention will now be described with reference to the accompanying drawings. The items shown herein are exemplary and intended to illustrate embodiments of the invention. The purpose of these descriptions is to provide a description that is considered most effective and readily understood of the principles and conceptual features of the invention. In this regard, these descriptions are necessary for a fundamental understanding of the invention and are not intended to depict excessive structural details, but rather to clarify, through description in conjunction with the accompanying drawings, how several embodiments of the invention are actually implemented.

[0031] [1] Dry friction materials The dry friction material 1 of the present invention is a dry friction material installed on the surface of a plate 6 in a torque limiting device 5. It is characterized by comprising reinforcing fibers 12 and vulcanized rubber 11, and having a carbide-containing anti-slip portion 111 on the contact surface 1A that contacts the surface of the plate 6 (see...). Figure 1 ).

[0032] The vulcanized rubber 11 contained in the dry friction material 1 is a material used as a so-called "matrix component" and constitutes the parent phase (continuous phase) for the reinforcing fibers 12. In addition, the vulcanized rubber 11 is the main material used in the torque limiting device 5 to generate frictional force in the dry friction material 1 that contacts the corresponding component.

[0033] There are no particular limitations on the types of vulcanized rubber. Examples of such types include acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), styrene-butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), chloroprene rubber (CR), polyisobutylene rubber, acrylate rubbers (acrylate-2-chloroethyl vinyl ether copolymer rubber, acrylate-acrylonitrile copolymer rubber, etc.), polyurethane rubber, fluororubbers (fluorinated olefin-vinylidene fluoride copolymer rubber, etc.), and silicone rubber. These vulcanized rubbers can be used individually or in combination.

[0034] Among the aforementioned vulcanized rubbers, from the viewpoint of frictional properties and impact resistance, the vulcanized rubbers included as dry friction materials are preferably NBR, SBR, BR, NR, IR, and CR, with NBR and SBR being more preferred.

[0035] There is no particular limitation on the content of vulcanized rubber 11 contained in the dry friction material 1. When the dry friction material as a whole is set to 100% by mass, it can be set to 1 to 50% by mass. The content of vulcanized rubber can preferably be set to 2 to 45% by mass, more preferably 3 to 40% by mass, even more preferably 4 to 35% by mass, particularly preferably 5 to 30% by mass, and most preferably 6 to 25% by mass.

[0036] Dry friction material 1 may contain components other than vulcanized rubber as a so-called "matrix component". There are no particular limitations on other components, but cured resins (resins formed by curing curable resins) can be listed.

[0037] There are no particular limitations on the types of curing resins, but examples include phenolic resins (phenolic resin, phenolic varnish resin (novolac resin), methyl phenolic resin, melamine-modified phenolic resin, etc.), urea-formaldehyde resin, epoxy resin, polyimide resin, unsaturated polyester resin, alkyd resin, polyurethane resin, polyimide resin (cured polyimide resin), and modified resins of these resins. These curing resins can be used alone or in combination with two or more.

[0038] From the viewpoint of frictional properties and impact resistance, among the cured resins included in dry friction materials, phenolic resins and melamine-modified phenolic resins are preferred. It should be noted that melamine-modified phenolic resin is a thermosetting resin in which phenol and melamine are used together as monomers. There is no particular limitation on the composition ratio of melamine-modified phenolic resin, but when the sum of units derived from phenol and units derived from melamine is set to 100%, for example, the units derived from melamine can be set to 30-80%.

[0039] When the dry friction material 1 contains a curing resin, there is no particular limitation on the amount of curing resin, and it can usually be determined based on the amount of vulcanized rubber. For example, if the vulcanized rubber is set to 100 parts by mass, the amount of curing resin can be set to 1 to 100 parts by mass, 2 to 75 parts by mass, 3 to 50 parts by mass, 4 to 40 parts by mass, or 5 to 35 parts by mass.

[0040] When the dry friction material 1 contains a cured resin, a plasticizer may be included as needed. The type of plasticizer is generally selected appropriately based on the type of cured resin, without particular limitation.

[0041] There is no particular limitation on the amount of plasticizer contained in the dry friction material 1. For example, if the vulcanized rubber is set to 100 parts by mass, it can be set to 0.1 to 50 parts by mass, 1 to 40 parts by mass, 3 to 30 parts by mass, 6 to 25 parts by mass, or 8 to 20 parts by mass.

[0042] The reinforcing fibers 12 included in the dry friction material 1 are a material used as a so-called "dispersion material," dispersed in a matrix phase with vulcanized rubber as the parent phase (matrix component). Furthermore, the reinforcing fibers 12 are used to reinforce vulcanized rubber with fibers to improve the strength, durability, and other properties of the dry friction material 1.

[0043] The reinforcing fiber 12 can be any type of organic fiber or inorganic fiber, without particular limitation. Generally, from the perspective of friction performance, heat resistance, safety and cost of dry friction material 1, inorganic fiber can be preferred.

[0044] There are no particular limitations on the types of inorganic fibers. Examples include amorphous fibers (glass fiber, silica fiber, slag wool, rock wool, etc.), monocrystalline fibers (ceramic fiber, alumina fiber, magnesium oxide fiber, titanate fiber, wollastonite fiber, etc.), polycrystalline fibers (ceramic fiber, alumina fiber, silica-alumina fiber, etc.), carbon-based fibers (carbon fiber, carbonized fiber, etc.), and metal fibers. These inorganic fibers can be used individually or in combination.

[0045] For the reinforcing fiber 12 of the dry friction material 1, amorphous fibers and / or carbon fibers are preferred among the above-mentioned inorganic fibers, glass fibers and / or carbon fibers are more preferred, and glass fibers are particularly preferred.

[0046] The reinforcing fiber 12 can be a heat-resistant product. There are no particular limitations on the specific heat resistance properties of the reinforcing fiber 12, but its melting point or decomposition temperature is preferably above 200°C, more preferably above 350°C. There are no particular limitations on the upper limit of the melting point or decomposition temperature; it can generally be set below 3500°C.

[0047] There are no particular limitations on the shape of the reinforcing fiber 12, but the aspect ratio (fiber length / fiber diameter), which is the ratio of fiber length to fiber diameter, is preferably 50 or more. Furthermore, there is no upper limit on the aspect ratio, which can usually be set to 1000 or less.

[0048] For reinforcing fiber 12, either long fiber or short fiber can be used. There is no specific definition for the fiber length of long fiber and short fiber. Long fiber can refer to fiber with a fiber length (maximum length) of more than 1000m, and short fiber can refer to fiber with a fiber length (maximum length) of about 1mm to 128mm.

[0049] Long fibers (filaments) can be used directly, or multiple filaments can be bundled together to form a thread, or multiple threads can be bundled together to form a rope or net-like roving.

[0050] Staples can be used directly, or multiple staples can be twisted into a thread to form a spun, or multiple spun yarns can be twisted into a cabled yarn.

[0051] To ensure the reinforcing fibers are continuously aligned in a specific direction, many dry friction materials use roving (long fibers) as reinforcing fibers. From the viewpoint of preventing roving segmentation, the manufacture of such dry friction materials involves pre-forming a pre-molded product, such as roving coated with rubber material, and then pressing it under high pressure. Other methods, such as extruding a rubber-fiber mixture into a metal mold, or directly molding the dry friction material without forming a pre-molded product, would lead to roving segmentation and are therefore difficult to employ. Furthermore, the shapes that can be used as dry friction materials are limited to those that minimize roving bending, such as rings.

[0052] In view of the above, short fibers are preferred for the reinforcing fibers. That is, in the manufacture of dry friction materials using short fibers as reinforcing fibers, methods such as extruding a mixture of fibers and rubber materials into a metal mold for molding can be employed, and the molding method for the dry friction material is essentially unrestricted. For example, the method of extruding a mixture of fibers and rubber materials into a metal mold allows the fibers to be oriented along the extrusion direction (a certain direction) of the mixture within the metal mold, and the dry friction material obtained by this method has properties equivalent to those of dry friction materials using roving. Furthermore, when short fibers are used as reinforcing fibers, they can be easily incorporated into the dry friction material without bending or other defects, and the shape of the dry friction material is essentially unrestricted.

[0053] As described above, from the viewpoint of suppressing the fragmentation and bending of fibers within the dry friction material 1 and improving or optimizing fiber orientation, short fibers can be used for the reinforcing fiber 12. In particular, when short fibers are used for the reinforcing fiber 12, a dry friction material with excellent dimensional accuracy and impact resistance can be obtained.

[0054] There is no particular limitation on the specific fiber length of the reinforcing fiber 12. The average fiber length of the material fiber used is preferably 0.5 to 10 mm, more preferably 1 to 8 mm, even more preferably 1.5 to 6 mm, and particularly preferably 2 to 5 mm.

[0055] There is no particular limitation on the specific fiber diameter of the reinforcing fiber 12, but the average fiber diameter is preferably 0.5~20μm, more preferably 2~15μm, even more preferably 3~14μm, and particularly preferably 6~13μm.

[0056] When the average fiber length and average fiber diameter are within the above range, it is easier to orient the fibers in a certain direction. Therefore, significant results can be achieved in improving and optimizing the orientation of the fibers when short fibers are used in the reinforcing fiber 12.

[0057] It should be noted that the average fiber length and average fiber diameter refer to the average values ​​of the fiber length (maximum length) and fiber diameter (maximum diameter) measured in 50 randomly selected reinforcing fibers.

[0058] Furthermore, regarding the fiber length of the aforementioned reinforcing fiber 12, the average fiber length of the material fibers used refers to the length when the dry friction material 1 is combined with other materials (more specifically, the length when the material fibers used as reinforcing fibers are combined with unvulcanized rubber, etc., during the preparation of the compound). During the manufacture of the dry friction material 1 (e.g., during extrusion compounding), the reinforcing fiber 12 in the dry friction material 1 may break. Therefore, the actual fiber length of the reinforcing fiber 12 inside the dry friction material 1 may be shorter than the aforementioned average fiber length.

[0059] There is no particular limitation on the content of reinforcing fiber 12 contained in the dry friction material 1. Based on the mass ratio when the vulcanized rubber is set to 100 parts by mass, it is preferably 50 parts by mass or more and 300 parts by mass or less, more preferably 60 parts by mass or more and 280 parts by mass or less, further preferably 80 parts by mass or more and 250 parts by mass or less, particularly preferably 100 parts by mass or more and 220 parts by mass or less, and especially preferably 120 parts by mass or more and 200 parts by mass or less.

[0060] When the content of reinforcing fiber 12 is within the above range, it is easier to orient the fiber in a certain direction. Therefore, significant results can be obtained in improving and optimizing the orientation of the fiber when using short fibers for reinforcing fiber 12.

[0061] When using short fibers, the reinforcing fibers 12 can be contained in the dry friction material 1 in a state of orientation along a certain direction.

[0062] Here, the orientation of the reinforcing fibers 12 in a certain direction refers to the state in which the extending direction (length direction) of the reinforcing fibers 12 dispersed in the parent phase composed of vulcanized rubber or the like is aligned in a certain direction. Furthermore, the alignment of the extending direction (length direction) of the reinforcing fibers 12 in a certain direction is not limited to the state in which the extending directions of all the reinforcing fibers 12 are substantially completely consistent in the specified direction, but also includes the state in which the extending directions of at least a portion of the reinforcing fibers 12 deviate from the direction intersecting the specified direction by a certain range of intersecting angles.

[0063] It should be noted that if the state of being completely aligned with the specified direction is set to 0 degrees, then the intersection angle can be set to 45 degrees or less, preferably 30 degrees or less, more preferably 20 degrees or less, and even more preferably 15 degrees or less.

[0064] The preferred orientation of the reinforcing fiber 12 is parallel to the outer edge of the dry friction material (see [reference]). Figure 1 , Figure 2 (c) Figure 3 (a) Figure 4 (b) etc.

[0065] That is, since the dry friction material 1 used in the torque limiting device 5 rotates and slides relative to the friction plate, its outer edge can be formed into a circle or an arc. Moreover, when the outer edge of the dry friction material 1 is formed into a circle or an arc, the reinforcing fiber 12 is preferably oriented with its length direction parallel to the outer edge.

[0066] In other words, regarding this morphology, the extending direction of the reinforcing fiber 12 is preferably substantially parallel to the tangent of the circular or arc-shaped outer edge of the dry friction material 1. Moreover, regarding this orientation, it is preferable that at least 50% of the number of reinforcing fibers 12 follows this rule, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90%, and more preferably at least 95%.

[0067] The dry friction material 1 may contain other components besides the reinforcing fiber 12 as a so-called "dispersion material". There are no particular limitations on the other components, and friction modifiers can be listed.

[0068] Friction modifiers are materials that help perform their function as dry friction materials, especially those with friction-modulating properties. Friction modifiers have a non-fibrous shape (the shape excluding the fibrous shape of the reinforcing fibers from the overall morphology) and have a different morphology from the reinforcing fibers.

[0069] There are no particular limitations on the types of friction modifiers. Examples include inorganic friction modifiers (inorganic friction modifiers composed of inorganic materials, composite inorganic friction modifiers that are mainly inorganic materials but also contain organic materials, etc.) and organic friction modifiers (inorganic friction modifiers composed of organic materials, composite inorganic friction modifiers that are mainly organic materials but also contain inorganic materials, etc.). These friction modifiers can be used alone or in combination with two or more.

[0070] There are no restrictions on the types of inorganic friction modifiers, but examples include sulfate-based materials {metal sulfates (magnesium sulfate, calcium sulfate, barium sulfate, etc.)}, carbonate-based materials {metal carbonates (magnesium carbonate, calcium carbonate [heavy calcium carbonate, light calcium carbonate], barium carbonate, etc.)}, titanate-based materials {metal titanates (potassium titanate, etc.)}, silicate-based materials {metal silicates (alumina silicate, zirconium silicate, etc.)}, hydroxide-based materials {metal hydroxides (calcium hydroxide, aluminum hydroxide, etc.)}, and oxide-based materials {metal oxides (zinc oxide [zinc white], titanium oxide, etc.)}. Materials include: iron, alumina, zirconium oxide, magnesium oxide, etc.; sulfide materials (metallic sulfides such as molybdenum disulfide and non-metallic sulfides such as antimony trisulfide); carbide materials (metallic carbides such as titanium carbide and non-metallic carbides such as silicon carbide and boron carbide); nitride materials (non-metallic nitrides such as silicon nitride and boron nitride); mineral materials (diatomaceous earth, wollastonite, dolomite, silica, mica, talc, kaolin, etc.); carbon-based materials (graphite, carbon black, coke, etc.); and metallic materials (aluminum, copper, brass, etc.). These materials can be used individually or in combination.

[0071] There are no restrictions on the types of organic friction modifiers, but examples include resins (cashewresin, melamine resin, cashew powder, etc.), rubber powder, and plant materials (plant bark (cork, etc.), seed shells (walnut shells, coconut shells, etc.)). These materials can be used individually or in combination.

[0072] There are no particular limitations on the morphology of the friction modulating material, as long as it is not fibrous. Specifically, as for the particle size, the ratio of the maximum length (major axis) to the minimum length (minor axis), i.e., the aspect ratio, is preferably less than 50 (1 or more).

[0073] Furthermore, the maximum length of the particle size is preferably less than 500 μm, and more preferably less than 750 μm. That is, the form of the friction modifier can be granular, irregular, blocky, needle-like, whisker-like, etc.

[0074] The average particle size d of the friction modifier can be set to 0.1≤d(μm)<500μm, further set to 1≤d(μm)≤350, and even further set to 2≤d(μm)≤200μm.

[0075] The average particle size of the friction modifier can be determined according to JIS Z8827-1 (static image analysis method).

[0076] There is no limitation on the content of friction modifier in the dry friction material 1. Relative to 100 parts by mass of vulcanized rubber, the friction modifier can be set to 50 parts by mass or more and 1000 parts by mass, further set to 60 parts by mass or more and 800 parts by mass, further set to 80 parts by mass or more and 600 parts by mass, further set to 90 parts by mass or more and 400 parts by mass, further set to 100 parts by mass or more and 350 parts by mass, and further set to 150 parts by mass or more and 300 parts by mass.

[0077] Figure 1 The diagram illustrates the dry friction material of the present invention, showing a cross-sectional view of the dry friction material mounted on a plate.

[0078] The dry friction material 1 of the present invention is a material used in a torque limiting device, which is mounted on the mounting surface 61 of the plate 6 provided in the torque limiting device (see [reference]). Figure 1 ).

[0079] The shape of the dry friction material 1 is not particularly limited as long as it is a shape that can be installed on the plate 6 of the torque limiting device.

[0080] There is no particular limitation on the overall shape of the dry friction material 1. Generally, from the viewpoint of using the dry friction material 1 sandwiched between the plate 6 and the plate being rubbed, it can be set to a flat plate shape. In addition, other shapes besides flat plate shape can also include curved plate shape, corrugated plate shape, etc.

[0081] There is no particular limitation on the shape of the dry friction material 1 when viewed from above. Typically, the shape of the plate 6 when viewed from above is annular (see...). Figure 6 (a)) The shape of the dry friction material 1 when viewed from above can be set to the shape of the surface contained in the plate 6.

[0082] Specifically, regarding the shape of the dry friction material 1, in terms of its shape when viewed in three dimensions, a button shape can be listed as an example (see...). Figure 2 (a)), Ring (see also) Figure 3 (a)), sector (see Figure 4 (a)), In addition, based on the shape when viewed from above, we can list circles, ovals, polygons, arcs, etc.

[0083] There is no particular limitation on the thickness of the dry friction material 1, which can be set to 2.0 mm or more and 2.6 mm or less. The thickness of the dry friction material 1 can preferably be set to 2.1 mm or more and 2.5 mm or less, and more preferably 2.2 mm or more and 2.4 mm or less.

[0084] It should be noted that "button shape" refers to a small, sheet-like shape with a specified thickness. More specifically, it is a shape whose maximum length when viewed from above is greater than its thickness when viewed from the side. There are no restrictions on the shape when viewed from above; for example, a circle can be used (see [link to other shape description]). Figure 2 (a) elliptical, polygonal, etc. Specifically, in the case of a button shape, the maximum length when viewed from above can be set to 8mm or more and 30mm or less, the thickness when viewed from the side can be set to 1mm or more and 5mm or less, and the ratio of the maximum length to the thickness (maximum length / thickness) can be set to 1.6~30.

[0085] Additionally, a ring refers to a ring-shaped form with a specified thickness. More specifically, it refers to a shape whose outer diameter and inner diameter, when viewed from above, are larger than its thickness when viewed from the side. There are no restrictions on the shape when viewed from above; for example, a circular ring can be used (see...). Figure 3 (a) elliptical ring, polygonal ring. Specifically, in the case of a ring, the outer diameter when viewed from above can preferably be set to 100 mm or more and 300 mm or less, more preferably 150 mm or more and 240 mm or less, and the thickness when viewed from the side can be set to 1 mm or more and 5 mm or less.

[0086] Additionally, a sector refers to an arc-shaped form with a specified thickness and a certain width. More specifically, it is a shape whose width is greater when viewed from above than its thickness when viewed from the side. The shape viewed from above can be arc-shaped (see [link to article]). Figure 4 (a)). Specifically, in the case of a sector shape, the shape when viewed from above can be set as the shape of a circle divided into 3 to 6 equal parts, in other words, it is an arc shape with a central angle of 60 to 120 degrees.

[0087] As a fixing structure for fixing to plate 6, dry friction material 1 may have a fixed shape portion 2 on the contact surface 1A (see...). Figure 2 (b) Figure 3 (b) Figure 4 (c)).

[0088] There are no particular limitations on the shape of the fixed shape portion 2. For example, as a top view, it can be a circle, an ellipse, a polygon, an arc, etc. Furthermore, as a cross-sectional view, the shape of the fixed shape portion 2 can be concave (see...). Figure 2 (d)), convex, cut-out (see...) Figure 4 (b) ), through-hole shape, etc.

[0089] There is no particular limitation on the size of the fixed shape part 2 when viewed from above, and it can be appropriately determined according to the shape of the fixed shape part 2 and the size of the fixed shape part 7 provided on the mounting surface 61 of the plate 6.

[0090] When the shape of the fixed shape portion 2 in cross-section is concave, the depth of the concavity measured from the contact surface 1A can be, for example, 1.2 mm or more, and preferably 1.5 mm to 1.7 mm. Generally, the depth of the concavity measured from the contact surface 1A is less than or equal to the thickness of the dry friction material 1. When the depth of the concavity is the same as the thickness of the dry friction material 1, the shape of the fixed shape portion 2 in cross-section is a through hole.

[0091] When the shape of the fixed shape part 2 is convex in cross-section, the height of the convexity measured from the contact surface 1A can be, for example, 1.0mm to 2.0mm, and preferably 1.1mm to 1.3mm.

[0092] In the dry friction material 1, the contact surface 1A that contacts the mounting surface 61 of the plate 6 has an anti-slip portion 111 containing carbides (see...). Figure 1 ).

[0093] The contact surface 1A of the dry friction material 1 suppresses sliding relative to the mounting surface 61 of the plate 6 by having an anti-slip portion 111. That is, when transmitting torque using the torque limiting device and when suppressing torque, the dry friction material 1 suppresses sliding relative to the plate 6 by the frictional force generated on the contact surface 1A with the anti-slip portion 111.

[0094] The dry friction material 1, whose sliding relative to the plate 6 is suppressed, is fixed to the plate 6 by remaining in a non-moving state on the mounting surface 61 of the plate 6. In other words, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A as a fixing structure for fixing it to the mounting surface 61 of the plate 6.

[0095] The dry friction material 1 has an abutment surface 1B at a position opposite to the contact surface 1A. The abutment surface 1B of the dry friction material 1 can abut against the friction plate of the torque limiting device. When transmitting torque using the torque limiting device, the dry friction material 1 causes the plate 6 and the friction plate to move in coordination through the friction force generated on the abutment surface 1B. When suppressing torque, the abutment surface 1B slides relative to the friction plate, causing the plate 6 to slide.

[0096] When suppressing torque, the dry friction material 1 allows the contact surface 1B to slide relative to the plate being rubbed, but prevents the contact surface 1A from sliding relative to the plate 6. Therefore, the dry friction material 1 is configured to have different coefficients of friction (μ) on the contact surface 1A and the contact surface 1B.

[0097] Specifically, the contact surface 1A has an anti-slip part 111, and its coefficient of friction (μ1) is higher than that of the contact surface 1B (μ2) (μ1>μ2).

[0098] Although the coefficient of friction (μ1) of the contact surface 1A is not limited, the ratio (μ1 / μ2) of the coefficient of friction (μ2) of the contact surface 1A to that of the abutment surface 1B is preferably set to more than 1 and less than 5 [1 < (μ1 / μ2) ≤ 5], more preferably 1.1 or more and less than 4 [1.1 ≤ (μ1 / μ2) ≤ 4], even more preferably 1.3 or more and less than 3 [1.3 ≤ (μ1 / μ2) ≤ 3], and particularly preferably 1.5 or more and less than 2.5 [1.5 ≤ (μ1 / μ2) ≤ 2.5].

[0099] There is no particular limitation on the shape of the contact surface 1A; it can be flat, uneven, curved, etc. However, from the viewpoint that setting it to a shape corresponding to the shape of the mounting surface 61 of the plate 6 increases the contact area with the mounting surface 61, thereby increasing the frictional force and thus increasing the fixing force of the dry friction material 1 relative to the plate 6, it is preferable to set it to a shape that is the same as the shape of the mounting surface 61 of the plate 6. Usually, the shape of the mounting surface 61 of the plate 6 is flat, therefore, the shape of the contact surface 1A is preferably flat.

[0100] The anti-slip portion 111 contains carbides, and by bringing the anti-slip portion 111 into contact with the plate 6, the coefficient of friction (μ1) of the contact surface 1A of the dry friction material 1 can be made different from the coefficient of friction (μ2) of the abutment surface 1B. Therefore, the anti-slip portion 111 is preferably exposed to the outside on the contact surface 1A of the dry friction material 1, in other words, exposed to the outside.

[0101] There are no particular limitations on the types of carbides contained in the anti-slip part 111, such as carbon, graphite, carbon sulfide, carbon chloride, carbon fluoride, silicon carbide, etc.

[0102] There is no particular limitation on the amount of carbide contained in the anti-slip portion 111. When the total amount of the anti-slip portion 111 is set to 100 parts by mass, the lower limit can be set to 50 parts by mass or more. The lower limit of the amount of carbide contained in the anti-slip portion 111 is preferably set to 60 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more. The upper limit of the amount of carbide contained in the anti-slip portion 111 is generally 100 parts by mass. When this amount is 100 parts by mass, the anti-slip portion 111 can be formed solely of carbide.

[0103] There are no particular limitations on the method of providing the anti-slip part 111 on the contact surface 1A. For example, the vulcanized rubber contained in the contact surface 1A can be carbonized by heating or the like, or the aforementioned carbonized material can be coated onto the contact surface 1A by coating or bonding.

[0104] There are no particular limitations on the shape and arrangement of the anti-slip part 111 in the contact surface 1A. The shape of the anti-slip part 111 can be set as follows when viewed from above the contact surface 1A (or when viewed from below the dry friction material 1): Figure 10 (a) shows a continuous band-like pattern. Figure 10 (b) shows the discontinuous banded pattern. Figure 10 (c) shows the circle, Figure 10 (d) shows the ellipse, Figure 10 (e) shows a continuous linear pattern. Figure 10 (f) shows the dotted lines, etc. Regarding the configuration of the anti-slip part 111, when taking the case where the shape of the anti-slip part 111 is circular when viewed from above (or below), it can be set as follows: Figure 10 (g) shows the checkerboard pattern. Figure 10 The interlacing pattern shown in (h) is an example.

[0105] It should be explained that Figure 10 (a) to (d) describe an embodiment in which only one row of anti-slip parts 111 is provided, but it is not limited thereto and multiple rows of anti-slip parts 111 may be provided.

[0106] Figure 10 (e) to (f) describe an embodiment with two rows of anti-slip parts 111, but it is not limited to this. The anti-slip parts 111 may be provided in only one row, or in three or more rows.

[0107] Figure 10 The embodiments described in (g) to (h) are of two columns of anti-slip parts 111, but are not limited thereto. The anti-slip parts 111 may be arranged in three or more columns, or the anti-slip parts 111 may be arranged in a checkerboard or staggered pattern. For example, they may be arranged in an irregular random pattern.

[0108] The anti-slip part 111 may contain substances other than carbides. Examples of substances other than carbides include rubbers such as vulcanized rubber, fibers such as reinforcing fibers, resins such as cured resins, and friction modifiers.

[0109] Regarding the substances other than carbides contained in the anti-slip part 111, specifically, when the anti-slip part 111 is provided on the contact surface 1A by heating or the like, it is mainly a substance that has not been carbonized by heating or the like. When the anti-slip part 111 is provided on the contact surface 1A by coating with carbides or the like, it is mainly a solvent, adhesive, glue, etc.

[0110] There is no particular limitation on the size of the anti-slip part 111. When observing the contact surface 1A from above (or the dry friction material 1 from below), as... Figure 10 As shown in (a)~(h), the anti-slip part 111 can be partially provided on a part of the contact surface 1A, or it can be provided entirely on all parts of the contact surface 1A, so that the entire contact surface 1A can be provided with the anti-slip part 111.

[0111] For example, regarding the size of the anti-slip part 111, when the total area of ​​the contact surface 1A is 100, the ratio of the area of ​​the anti-slip part 111 to the area of ​​the contact surface 1A can be set to 0.1% to 100%, preferably 1% to 70%, more preferably 3% to 50%, and even more preferably 5% to 30%.

[0112] There is no particular limitation on the thickness of the anti-slip portion 111, but the lower limit can be set to 1 μm or more. The lower limit of the thickness is preferably set to 10 µm or more, more preferably 50 µm or more, and even more preferably 100 µm or more. The upper limit of the thickness of the anti-slip portion 111 can be set to 1 mm or less. The upper limit of the thickness is preferably set to 500 µm or less, and more preferably 300 µm or less.

[0113] The carbide included in the anti-slip part 111 may be a substance derived from the vulcanized rubber 11. Specifically, the carbide included in the anti-slip part 111 may be a substance obtained by carbonizing the vulcanized rubber on the surface of the contact surface 1A of the dry friction material 1 through heating or the like.

[0114] There are no particular limitations on the method for carbonizing the vulcanized rubber on the surface of the contact surface 1A, and methods such as laser treatment, burner treatment, and hot plate treatment can be listed. Among these, from the viewpoint that the vulcanized rubber on the surface of the contact surface can be appropriately and easily carbonized by heating only the surface of the contact surface to a high temperature, laser treatment is the preferred method.

[0115] [2][Torque Limiting Device] The torque limiting device 5 of the present invention includes a dry friction material 1 and a plate 6 for mounting the dry friction material 1. Plate 6 has multiple fixed-shape portions 7 on the mounting surface 61 where the dry friction material 1 is mounted. The dry friction material 1 has a fixed shape portion 2 that engages with the fixed shape portion 7 (see [reference]). Figures 5-8 ).

[0116] The dry friction material 1 provided in the torque limiting device 5 may be the dry friction material described in [1] above.

[0117] The plate 6 of the torque limiting device 5 is not particularly limited as long as it is a plate on which the dry friction material 1 is installed; typically, a cover plate 6A or a push plate 6B can be used (see [reference]). Figure 5 ).

[0118] The cover plate 6A and the push plate 6B are plates 6 included in the torque limiting device 5, used for mounting the dry friction material 1. The cover plate 6A and the push plate 6B are arranged such that the mounting surfaces 61 of the dry friction material 1 are opposite to each other.

[0119] It can be configured such that the friction plate 121 is disposed between the cover plate 6A and the push plate 6B in a state of contact with the dry friction material 1.

[0120] Alternatively, as a torque limiting device 5, plate 6 may be implemented as one or more intermediate plates disposed between cover plate 6A and push plate 6B.

[0121] In this case, the middle plate uses both its surface and back as mounting surfaces, and the dry friction material 1 is fixed on these mounting surfaces.

[0122] Alternatively, it can be configured such that the friction plate 121 is disposed between the cover plate 6A or the push plate 6B and the intermediate plate, or between the intermediate plates, in a state of contact with the dry friction material 1.

[0123] Plate 6 can typically be designed as a ring-shaped flat plate (see...). Figure 6 (a), (b)).

[0124] When plate 6 is a cover plate 6A and a push plate 6B, a locking hole 14 can be provided in the cover plate 6A, and a locking tab 13 can be provided in the push plate 6B (see...). Figure 7 , Figure 8 ).

[0125] The engaging hole 14 is formed by penetrating the cover plate 6A along the thickness direction of the cover plate 6A. The engaging tab 13 is formed by protruding from the outer periphery of the push plate 6B in a direction opposite to the cover plate 6A.

[0126] The cover plate 6A can be engaged with the push plate 6B via the engaging hole 14 and the engaging tab 13, preventing the cover plate 6A and the push plate 6B from rotating relative to each other around the axis C, but allowing them to move relative to each other along the axis. It should be noted that the push plate 6B is subjected to force on the cover plate 6A by a force-applying mechanism (not shown).

[0127] Regarding the materials of plate 6 and the rubbed plate 121, stainless steel or other metals can usually be used.

[0128] The surface of plate 6 can be used as a mounting surface 61 for mounting the dry friction material 1. There is no particular limitation on which part of the surface of plate 6 is used as the mounting surface 61. Specifically, the part that contacts the friction plate 121 is used as the mounting surface 61. For example, in the case of cover plate 6A and push plate 6B, the part on their surfaces that contacts the friction plate 121 disposed between them can be used as the mounting surface 61.

[0129] The mounting surface 61 of plate 6 can be surface treated by coating or the like. The coefficient of friction (μ3) of the surface-treated mounting surface 61 can be set to be higher than the coefficient of friction (μ4) of the surface of the plate 121 being rubbed (μ3>μ4).

[0130] A fixed-shape part 7 is provided on the mounting surface 61 of the plate 6 as a fixing structure for fixing the dry friction material 1.

[0131] Multiple fixed-shape parts 7 can be arranged parallel to the inner or outer periphery of the plate 6 (6 in the figure) (see Figure 6 (a) and (b)). Multiple fixed-shape portions 7 can be arranged on the same circumference on the mounting surface 61 of the plate 6. Furthermore, multiple fixed-shape portions 7 can be arranged at equal intervals.

[0132] It should be noted that "parallel" means that the imaginary lines connecting the centers of the multiple fixed-shape parts 7 are substantially circular and are substantially concentric with the inner and outer peripheries of the plate 6.

[0133] There is no particular limitation on the shape of the fixed shape part 7, and it can usually be set to a shape that can engage with the fixed shape part 2 of the dry friction material 1.

[0134] That is, as the shape when viewed from above, the shape of the fixed shape part 7 can be a circle, an ellipse, a polygon, an arc, etc.

[0135] Furthermore, as the shape in cross-section, the shape of the fixed shape portion 7 can be a convex shape, a concave shape, a through hole shape, etc., corresponding to the cross-sectional shape of the fixed shape portion 2 (see [reference]). Figure 6 (a), (b)).

[0136] There is no particular limitation on the size of the fixed shape part 2, and it can be appropriately determined according to the shape of the fixed shape part 2 and the size of the fixed shape part 7 provided on the mounting surface 61 of the plate 6.

[0137] When the fixed shape portion 2 is convex, the height of the convex shape can be set to 1.0mm to 2.0mm, preferably 1.1mm to 1.3mm. When the fixed shape portion 2 is concave, the depth of the concave shape can be set to 1.2mm or more, preferably 1.5mm to 1.7mm.

[0138] It should be noted that the depth of the concave shape is usually less than the thickness of the plate 6. When the depth of the concave shape is the same as the thickness of the plate 6, the fixed shape part 7 is a through hole.

[0139] There is no particular limitation on the number of dry friction materials 1 installed relative to the plate 6; only one may be used, or more than two may be used. Generally, the number of dry friction materials 1 installed can be determined based on the shape of the dry friction materials 1, the number of fixed shape parts 2 provided, etc.

[0140] For example, if the shape of the dry friction material 1 when viewed from above is button-shaped, the number of dry friction materials 1 installed relative to the plate 6 can be set to multiple and the same as the number of fixed shape parts 7 of the plate 6.

[0141] When the shape of the dry friction material 1 in top view is fan-shaped, the number of dry friction materials 1 installed relative to the plate 6 can be set to multiple and less than half the number of fixed shape parts 7 of the plate 6.

[0142] That is, regarding the mounting of the dry friction material 1 on the plate 6, for example, one dry friction material 1 can be fixed on one fixed shape portion 7. Specifically, it can be configured such that one dry friction material 1 is fixed on one fixed shape portion 7 by fitting the fixed shape portion 2 provided at the center of the bottom surface of the button-shaped dry friction material 1 with the fixed shape portion 7 provided on the surface of the plate 6. In this embodiment, when the dry friction materials 1 are arranged at equal intervals in the circumferential direction of the plate 6, the fixed shape portions 7 are generally also arranged at equal intervals.

[0143] Alternatively, the dry friction material 1 can be configured such that it is secured to multiple fixed shape portions 7 by the fixed shape portion 2. Specifically, it can be configured such that the fixed shape portion 2 at both ends of the fan-shaped dry friction material 1 in the arc direction engages with the fixed shape portion 7 on the surface of the plate 6, thereby securing (clamping) the dry friction material 1 between multiple fixed shape portions 7. In this embodiment, when the dry friction materials 1 are arranged at equal intervals in the circumferential direction of the plate 6, the pair of fixed shape portions 7 corresponding to the two ends of the dry friction material 1 are also arranged at equal intervals.

[0144] Alternatively, the dry friction material 1 can be fixed to a plate 6 by engaging multiple fixed shape portions 2 on the contact surface 1A of the annular dry friction material 1 with multiple fixed shape portions 7 on the surface of the plate 6. In this embodiment, the number of fixed shape portions 2 on the dry friction material 1 is the same as the number of fixed shape portions 7 on the plate 6.

[0145] When multiple dry friction materials 1 are installed relative to the plate 6, the dry friction materials 1 can be located on the inner periphery side and / or the outer periphery side of the mounting surface 61 of the plate 6.

[0146] Alternatively, the dry friction material 1 can be positioned at the midpoint between the inner and outer peripheries of the mounting surface 61 of the plate 6.

[0147] Furthermore, the above-mentioned dry friction material 1 can be combined in two or more ways for use.

[0148] Regarding the above configuration, for example, the dry friction material 1 can be arranged entirely on one circumference of the surface of the plate 6.

[0149] In addition, multiple dry friction materials 1 can be disposed on multiple circumferences of different diameters on the surface of the plate 6.

[0150] Alternatively, depending on the design conditions of plate 6 (e.g., the position of the engagement hole, etc.), a portion of the dry friction material 1 can be arranged off-circumference.

[0151] In the above configuration, for example, the dry friction material 1 can be arranged at equal intervals on a circumference.

[0152] Alternatively, depending on the design conditions of plate 6 (e.g., the position of the engagement holes), some or all of the dry friction material 1 can be arranged at unequal intervals in the circumferential direction of plate 6.

[0153] For example, the dry friction material 1 can be bonded to the surface of the plate 6 by an adhesive material or the like. From the viewpoint of processability, the dry friction material 1 is preferably not bonded to the surface of the plate 6, but is fixed by the engagement relationship between the fixed shape part 2 and the fixed shape part 7.

[0154] [3] Manufacturing method of dry friction material The method for manufacturing the dry friction material of the present invention includes: The process of applying localized heat treatment to the contact surface of the aforementioned dry friction material to carbonize the vulcanized rubber on the surface of the contact surface, thereby forming the aforementioned anti-slip part.

[0155] The dry friction material manufactured by the manufacturing method of the present invention can be the dry friction material described in [1] above.

[0156] Dry friction materials are obtained by applying localized heating treatment to form an anti-slip layer on the contact surface. This localized heating treatment refers to the treatment of heating the dry friction material locally, specifically, heating only the surface layer of the contact surface of the dry friction material, which is different from the so-called "heat treatment" that heats the entire dry friction material.

[0157] Localized heating treatment is not particularly limited as long as it can heat only the surface layer of the contact surface of the dry friction material; examples include laser treatment, blowtorch treatment, and hot plate treatment. Among these, laser treatment can heat only the surface layer of the contact surface to a high temperature, causing the vulcanized rubber on that surface to carbonize in a short time, and is therefore preferred as a localized heating treatment.

[0158] In laser processing, there are no particular restrictions on the type of heat source. Suitable heat sources include CO2 lasers, YAG lasers, YLF lasers, and Yb lasers.

[0159] There are no particular limitations on the output in laser processing; the output that can cause carbonization of the vulcanized rubber contained in the dry friction material can be selected as appropriate. For example, the output can be set to 1J~20J, preferably 2J~15J, and more preferably 3J~10J.

[0160] There are no particular limitations on the wavelength and pulse width in laser processing; the wavelength and pulse width that can cause carbonization of the vulcanized rubber contained in the dry friction material can be selected as appropriate. In addition, the oscillation mode can be set to either continuous or pulsed.

[0161] In laser processing, only the portion of the contact surface irradiated by the laser is heated to a high temperature, causing the vulcanized rubber to carbonize and thus forming an anti-slip part.

[0162] The size of the anti-slip portion on the contact surface can be determined based on the range of the irradiated laser. From the viewpoint of maintaining an effective focal length, the range of the irradiated laser is usually a part of the contact surface. In this case, the anti-slip portion can be formed as a line or a strip on the contact surface. Alternatively, if the irradiation range is expanded to the entire contact surface by appropriately moving the irradiation position of the laser, the anti-slip portion can be formed on the entire contact surface.

[0163] The manufacturing method of the present invention may include: a step of extruding a compound of uncured rubber, which is to be formed into the above-mentioned vulcanized rubber, and the above-mentioned reinforcing fiber to obtain a composition for friction materials; and, The process involves filling the cavity of a metal mold with the above-mentioned friction material composition and then vulcanizing it to obtain the above-mentioned dry friction material having a skin layer formed on the surface in contact with the wall of the cavity.

[0164] In the manufacturing method of dry friction materials, a friction material composition is used to obtain the dry friction material. This friction material composition can be a substance extruded from a mixture of uncured rubber that will form a vulcanized rubber and reinforcing fibers (material fibers used to reinforce the reinforcing fibers).

[0165] Regarding the reinforcing fibers, as described in the dry friction materials described above [1].

[0166] Uncured rubber is a precursor to the vulcanized rubber contained in the dry friction material described above [1]. In order to convert uncured rubber into vulcanized rubber by vulcanization, the above compound may contain a vulcanizing agent (crosslinking agent) and a vulcanization accelerator (crosslinking accelerator).

[0167] There are no restrictions on the type of vulcanizing agent, but examples include sulfur-based vulcanizing agents (such as sulfur), organic peroxide-based vulcanizing agents, metal oxide-based vulcanizing agents, sulfur-containing organic compounds, polyamine-based vulcanizing agents, polyol-based vulcanizing agents, metal soap-based vulcanizing agents, triazine-based vulcanizing agents, quinone-type vulcanizing agents, and maleimide-based vulcanizing agents. Only one of these vulcanizing agents can be used, or two or more can be used simultaneously.

[0168] Examples of sulfur-based vulcanizing agents include sulfur (sulfur powder, sulfur bloom, surface-treated sulfur, colloidal sulfur, etc.) and sulfur chloride. Examples of organic peroxide-based vulcanizing agents include dicumyl peroxide, cumene peroxide, cumyl peroxide, dicumyl peroxide, and bis(α,α-dimethylbenzyl) peroxide. Furthermore, examples of metal oxide vulcanizing agents include zinc oxide and magnesium oxide. Examples of sulfur-containing organic vulcanizing agents include morpholine disulfide, alkylphenol disulfide, and thiuram polysulfide. Additionally, examples of polyamine-based vulcanizing agents include hexamethylenediamine carbamate, hexamethylenediamine, triethylenetetramine, tetraethylenediamine, and ammonium benzoate. Furthermore, examples of polyol-based vulcanizing agents include bisphenol, hydroquinone, and pentaerythritol. Additionally, examples of metal soap-based vulcanizing agents include sodium stearate, potassium stearate, sodium oleate, and potassium oleate. Only one of these vulcanizing agents may be used, or two or more may be used simultaneously.

[0169] There are no restrictions on the types of vulcanization accelerators, but are examples that can be listed, such as hexamethylenetetramine, butylaldehyde-monobutylamine condensate, tributylenetetramine, guanidine salts like diphenylguanidine; thiazoles like imidazoline and mercaptothiazoline; thiourea such as sulfenamide, thiocarbamide, diethylthiourea, and dibutylthiourea; dithiocarbamates like sodium dimethyl dithiocarbamate, thiuram compounds, and thioglycolic acid esters. Only one of these vulcanization accelerators can be used, or two or more can be used simultaneously.

[0170] Specifically, the manufacturing method of dry friction materials may include a rubber mixing process, an extrusion process, and a thermoforming process.

[0171] The rubber compounding process is the process of obtaining a compound of uncured rubber and reinforcing fibers.

[0172] The extrusion process is the process of extruding a compound to obtain a composition for friction materials.

[0173] The thermoforming process involves filling a metal mold cavity with a composition of friction material and then vulcanizing it to obtain a dry friction material with a skin layer formed on the surface in contact with the wall of the cavity.

[0174] Regarding the rubber compounding process, the compounding of uncured rubber with reinforcing fibers and vulcanizing agents can be carried out in any manner. For example, extruders (single-screw extruders, twin-screw extruders, etc.), kneaders, and mixers (high-speed flow mixers, paddle mixers, screw mixers, etc.) can be used. Only one type of these machines can be used, or two or more can be used simultaneously. When using two or more mixers, they can be used continuously or in batches. Furthermore, the raw materials can be compounded together or added in multiple stages.

[0175] In addition, there are no restrictions on the mixing temperature during mixing. For example, it can be set to 25°C or higher and 400°C or lower, 50°C or higher and 350°C or lower, 75°C or higher and 325°C or lower, or 100°C or higher and 300°C or lower.

[0176] Regarding the extrusion process, by extruding the compound, the reinforcing fibers within the extruded compound can be oriented. The extrusion of the compound can be carried out in any manner, for example, using a single-screw extruder, a twin-screw extruder, a 1.5-screw extruder, or other extruders.

[0177] Regarding the thermoforming process, the friction material composition, which is filled into the cavity of a metal mold and vulcanized, forms a skin layer at the surface in contact with the cavity wall due to the rapid curing of the vulcanized rubber. This skin layer, due to shrinkage and curing caused by vulcanization, causes the reinforcing fibers to be pressed inwards and move, resulting in a state that contains almost no reinforcing fibers. The anti-slip part can be formed by carbonizing this skin layer (vulcanized rubber), making it almost free of carbides from the reinforcing fibers. In other words, by making the anti-slip part contain only carbides from the vulcanized rubber, the problem of instability in the coefficient of friction (μ) caused by foreign matter such as carbides from the reinforcing fibers can be eliminated.

[0178] The thermoforming process can include an extrusion step by simultaneously filling the friction material composition into a metal mold and extruding the compound in the extrusion step. In this case, the metal mold can be, for example, a mold having a preparatory cavity for receiving the compound, a molding cavity for molding the precursor (excipient before vulcanization) to be formed into a dry friction material, and a flow channel connecting these preparatory cavities and the molding cavity. That is, by receiving the compound in the preparatory cavity and by molding, the compound is moved from the preparatory cavity to the molding cavity via the flow channel, thereby extruding while it can move from the flow channel to the molding cavity. As a result, the reinforcing fibers in the compound received in the molding cavity can be formed into a state of orientation in a certain direction.

[0179] The extrusion operation described above can be performed once or multiple times. Multiple extrusions refer to extruding the extruded compound (hereinafter also simply referred to as "extrudate") again. For example, multiple extrusions can be performed to improve the orientation of the reinforcing fibers. On the other hand, it is preferable not to perform operations that reduce the orientation of the reinforcing fibers on the extrudate. That is, it is preferable not to perform operations that involve mixing or granulating the extrudate.

[0180] When inorganic fibers are used as reinforcing fibers, the fibers themselves possess moderate rigidity. Therefore, by flowing the compound, it is easy to align the orientation of the reinforcing fibers, and the reinforcing fibers can be oriented without bending or stretching. Furthermore, the reinforcing fibers are less likely to be fragmented during the flow of the compound, and their length can be maintained, which is also preferable.

[0181] The shape of the extrudate is not limited and can be cylindrical (including continuous linear), tubular, sheet-like, etc., with cylindrical or tubular shapes being preferred, and cylindrical shapes being more preferred. Therefore, the die used for extrusion is also not limited, but a die capable of shaping the extrudate into a cylindrical or tubular shape is preferred, and a die capable of shaping it into a cylindrical shape is more preferred. Furthermore, when the extrudate is cylindrical, its cross-sectional shape is not limited and can be circular, polygonal (triangle, quadrilateral), etc., with circular shapes being preferred. It should be noted that a circular shape can include not only a perfect circle but also shapes such as ellipse, teardrop shape, etc., where at least a portion of the outer edge is curved.

[0182] When the extrudate is cylindrical (including continuous linear shapes with circular cross-sections), there is no limitation on its diameter from the viewpoint of the flowability of the unvulcanized rubber and the compound of reinforcing fibers, the average length of the reinforcing fibers, etc. For example, it can be set to 1mm~50mm, 2mm~40mm, 3mm~30mm, 4mm~25mm, or 5mm~20mm.

[0183] Regarding the orientation of the reinforcing fibers, it is preferable that all of them are in the same orientation; typically, it is preferable that 50% or more of the reinforcing fibers are in the same orientation. From the viewpoint of improving dimensional stability and impact resistance, this proportion is preferably larger, preferably 60% or more, more preferably 70% or more, further preferably 80% or more, particularly preferably 90% or more, and especially preferably 95% or more.

[0184] It should be noted that the orientation of the reinforcing fibers achieved through extrusion is not obtained by individually orienting each and every single reinforcing fiber. Therefore, it is extremely difficult to uniquely specify and quantify, for example, how many reinforcing fibers are oriented in the first direction and how many are oriented in the second direction. Consequently, directly specifying the orientation of the reinforcing fibers in dry friction materials is almost impractical; there are situations that are impossible and impractical.

[0185] Dry friction materials are formed by curing friction materials with a composition through heating during a thermoforming process. Curing is typically carried out using the aforementioned curing agents and curing accelerators. Furthermore, there are no limitations on the heating temperature during curing; for example, it can be set to 100°C or higher and 400°C or lower, 110°C or higher and 350°C or lower, 115°C or higher and 300°C or lower, or 120°C or higher and 250°C or lower.

[0186] The aforementioned dry friction material 1 has an anti-slip portion 111 on the contact surface 1A of the mating component such as a plate, resulting in a different coefficient of friction (μ) between the contact surface 1A and the abutment surface 1B. In the manufacturing method of this dry friction material, the anti-slip portion can be formed by carbonizing the skin layer (vulcanized rubber) formed on the surface by contacting the friction material composition with the wall of the cavity through localized heating treatment such as laser processing.

[0187] In other words, in the aforementioned method for manufacturing dry friction materials, it is not necessary to create ribs (protrusions) in the metal mold to cause uneven distribution of reinforcing fibers (glass fibers), as was done in the past. Furthermore, it is unnecessary to perform shape-related operations due to the formation of such ribs (protrusions). Additionally, in the past, the skin layer caused sliding of mating parts such as plates, thus requiring grinding or other removal processes. In the aforementioned method for manufacturing dry friction materials, since the skin layer is utilized in the formation of the anti-slip portion, grinding-related operations are unnecessary.

[0188] Therefore, according to the method for manufacturing dry friction material of the present invention, by applying local heat treatment to the dry friction material to form an anti-slip part, there is no need to perform complicated operations such as operations related to shape correction or operations related to improving flatness through grinding, and the friction coefficients (μ) of the surface and back of the dry friction material can be made different.

[0189] The present invention will now be described in more detail through Examples 1 to 3.

[0190] <Example 1> like Figure 2 As shown in (a) to (d), the dry friction material 1 is formed into a button shape that appears circular when viewed from above, and a fixed shape portion 2 is provided at the center of the bottom surface. The fixed shape portion 2 is a concave shape that appears circular when viewed from above.

[0191] The reinforcing fiber 12 is composed of short fibers and is oriented in a circular manner parallel to the outer periphery of the dry friction material 1.

[0192] An anti-slip portion 111 is formed on the bottom surface, i.e., the contact surface 1A, of the dry friction material 1. This anti-slip portion 111 is formed into a circular line by irradiating the radial center of the contact surface 1A with a laser in a circular manner.

[0193] like Figure 6 (a), (b) and Figure 7 As shown, the torque limiting device 5 includes a plate 6 and a dry friction material 1 fixed to the surface of the plate 6.

[0194] Plate 6 has a fixing shape portion 7 on the mounting surface 61 for fixing. The fixing shape portion 7 is convex (see...). Figure 6 (b)) The shape is circular when viewed from above.

[0195] The shape of plate 6 when viewed from above is annular. Multiple (6 in the figure) of fixed shape part 7 and dry friction material 1 are provided in a manner parallel to the inner or outer periphery of plate 6.

[0196] The fixed shape portion 7 and the dry friction material 1 are all arranged on the same circumference of the surface of the plate 6. Furthermore, the fixed shape portion 7 and the dry friction material 1 are arranged at equal intervals.

[0197] In plate 6, a dry friction material 1 is fixed on a fixed shape portion 7. Specifically, by fitting the fixed shape portion 2 of the dry friction material 1 with the fixed shape portion 7 of plate 6, a dry friction material 1 is fixed on a fixed shape portion 7.

[0198] Specifically, the torque limiting device 5 includes a cover plate 6A and a push plate 6B as plates 6. These plates 6A and 6B are arranged such that the mounting surfaces 61 (surfaces) on which the dry friction material 1 is mounted are opposite each other. Furthermore, the friction plate 121 is disposed between the plates 6A and 6B in a state of abutting against the contact surface 1B of the dry friction material 1.

[0199] The pusher plate 6B is provided with a locking tab 13 extending along the axis C.

[0200] The cover plate 6A is provided with a locking hole 14 that engages with the locking tab 13.

[0201] By engaging the engaging tab 13 with the engaging hole 14, the cover plate 6A and the push plate 6B are configured to be unable to rotate relative to each other about the axis C but are able to move relative to each other along the axial direction. Furthermore, the push plate 6B is subjected to force on the cover plate 6A by a force-applying mechanism (not shown).

[0202] In the torque limiting device 5, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A that contacts the plate 6, thereby making the coefficient of friction (μ) of the contact surface 1A higher than that of the contact surface 1B that abuts against the rubbed plate 121.

[0203] The dry friction material 1 does not have an anti-slip portion 111 on the contact surface 1B, and the coefficient of friction (μ) of the contact surface 1B is lower than that of the contact surface 1A. When torque is transmitted using the torque limiting device 5, the dry friction material 1 causes the plate 6 and the rubbed plate 121 to move in tandem through the frictional force generated on the contact surface 1B. When suppressing torque, the contact surface 1B slides relative to the rubbed plate 121, causing the plate 6 to rotate relative to the rubbed plate 121 (slippage).

[0204] In the dry friction material 1, by having an anti-slip part 111, the coefficient of friction (μ) of the contact surface 1A is increased, thereby suppressing sliding relative to the mounting surface 61 (surface) of the plate 6.

[0205] Furthermore, when suppressing torque, the dry friction material 1 causes the contact surface 1B to slide relative to the rubbed plate 121, while preventing the contact surface 1A from sliding relative to the plate 6. Therefore, the dry friction material 1 can always remain fixed relative to the plate 6.

[0206] As can be seen from the above, by providing an anti-slip portion 111 on the contact surface 1A, which is the back side, the dry friction material 1 can make the coefficient of friction (μ) of the contact surface 1B, which is the surface, different from that of the contact surface 1A. As a result, the torque limiting device 5 can perform appropriate torque transmission and torque suppression functions.

[0207] In addition, in the torque limiting device 5, the dry friction material 1 is segmented by setting the number of dry friction materials 1 installed on the plate 6 to multiple.

[0208] The segmentation of such dry friction material 1 can increase the yield (due to the reduction of material costs caused by the reduction of friction area and the increase of output caused by the increase of heat treatment input, etc.) while improving the design freedom (miniaturization, weight reduction, and rationalization of required values ​​(flatness deviation, cracking, etc.)).

[0209] In particular, the segmentation of the dry friction material 1 ensures a more stable coefficient of friction due to the smaller friction area and increased surface pressure (specifically, reducing the rate of decrease in the coefficient of friction during thermally degraded sliding).

[0210] Furthermore, due to the significant difference in the coefficient of friction (μ) between the contact surface 1A and the abutment surface 1B caused by the anti-slip part 111, the torque limiting device 5 can effectively perform its appropriate torque transmission and torque suppression functions.

[0211] Furthermore, the dry friction material 1 is formed in the shape of a button, and a fixed shape portion 2 is provided at the center of the contact surface 1A. As a result, the dry friction material 1 can appropriately withstand the force applied by the plate 6 via the fixed shape portion 7, thereby enabling the suppression of damage.

[0212] In addition, the fixed position and number of dry friction materials 1 can be adjusted according to the size of the plate 6, and the same button-shaped dry friction material 1 can easily handle plates 6 of different sizes.

[0213] In particular, for annular dry friction materials, it is necessary to manufacture materials that match the size of the plate, but button-shaped dry friction materials 1 can be manufactured in the same size regardless of the size of the plate, thus enabling low-cost and efficient manufacturing.

[0214] Furthermore, through the fixing structure of the dry friction material 1 provided on the contact surface 1A, which consists of the fixed shape portion 2 and the anti-slip portion 111, the dry friction material 1 is fixed to the plate 6 without the use of adhesive materials or the like, but rather through a snap-fit ​​relationship and frictional force. In other words, without the need for adhesive coating processes, the dry friction material 1 can be fixed simply by installing it onto the plate 6, thereby achieving cost reduction.

[0215] <Example 2> like Figure 3 As shown in (a) and (b), the dry friction material 1 is annular, and multiple fixed-shape parts 2 are provided on the contact surface 1A (bottom surface).

[0216] In addition, the dry friction material 1 is configured such that its inner diameter is approximately equal to that of the plate 6, and its dimensions match those of the plate 6.

[0217] The reinforcing fiber 12 is composed of short fibers and is oriented in a circular manner parallel to the outer and inner peripheries of the dry friction material 1.

[0218] On the bottom surface of the dry friction material 1, i.e. the contact surface 1A, a circular line is formed by irradiating two locations in a circular manner, one near the outer periphery and the other near the inner periphery.

[0219] The torque limiting device 5 uses the same device as in Example 1, and includes a plate 6 and a dry friction material 1 fixed to the surface of the plate 6.

[0220] That is, such as Figure 8 As shown in (a) and (b), the shape of plate 6 when viewed from above is annular, and multiple (6 in the figure) fixed shape parts 7 are provided on the mounting surface 61.

[0221] In the dry friction material 1, a plurality of fixed shape portions 2 are arranged in such a way that they correspond to the plurality of fixed shape portions 7 provided on the plate 6.

[0222] A dry friction material 1 is mounted on a plate 6. Specifically, by fitting each of the fixed shape portions 2 of the dry friction material 1 with each of the fixed shape portions 7 of the plate 6, a dry friction material 1 is secured on a plate 6.

[0223] In the torque limiting device 5, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A that contacts the plate 6, thereby making the coefficient of friction (μ) of the contact surface 1A higher than that of the contact surface 1B that abuts against the rubbed plate 121. In other words, the coefficient of friction (μ) of the contact surface 1A and the contact surface 1B of the dry friction material 1 is different.

[0224] When torque is transmitted using torque limiting device 5, the dry friction material 1 causes plate 6 and the rubbed plate 121 to move in coordination through the friction force generated by the contact surface 1B. When suppressing torque, the contact surface 1B slides relative to the rubbed plate 121, causing plate 6 to rotate relative to the rubbed plate 121 (slippage).

[0225] In the dry friction material 1, by having an anti-slip part 111, the coefficient of friction (μ) of the contact surface 1A is improved, and by preventing the contact surface 1A from sliding relative to the plate 6, it can always maintain a fixed state relative to the plate 6.

[0226] That is, by providing an anti-slip part 111 on the contact surface 1A, the dry friction material 1 can easily make the coefficient of friction (μ) of the contact surface 1A and the abutment surface 1B different. As a result, the torque limiting device 5 is able to perform its proper torque transmission and torque suppression functions.

[0227] It should be noted that the dry friction material 1 is formed in a ring shape. That is to say, for the dry friction material 1, even without the use of roving, it is easy to manufacture a product with a shape equivalent to existing products.

[0228] <Example 3> like Figure 4As shown in (a) to (c), the dry friction material 1 is fan-shaped, and has fixed shape portions 2 at both ends in the arc direction. The fixed shape portions 2 are slit-shaped. The slit-shaped fixed shape portions 2 are portions where an arc-shaped slit is formed from the end face of the dry friction material 1 in the arc direction towards the inside.

[0229] The reinforcing fiber 12 is formed from short fibers and is oriented in an arc shape parallel to the outer and inner peripheries of the dry friction material 1.

[0230] An anti-slip portion 111 is formed on the bottom surface, i.e., the contact surface 1A, of the dry friction material 1. The anti-slip portion 111 is formed into an arc-shaped line by irradiating the middle portion of the contact surface 1A in the radial (width direction) direction, avoiding the fixed shape portion 2.

[0231] The torque limiting device 5 uses the same device as in Example 1, and includes a plate 6 and a dry friction material 1 fixed to the surface of the plate 6.

[0232] That is, such as Figure 9 As shown in (a) and (b), the shape of plate 6 when viewed from above is annular, and multiple (6 in the figure) fixed shape parts 7 are provided on the mounting surface 61.

[0233] One dry friction material 1 is secured to multiple (two in the figure) fixed shape portions 7 by a fixed shape portion 2. Specifically, by engaging the fixed shape portion 2 of the dry friction material 1 with the fixed shape portion 7 of the plate 6, one dry friction material 1 is secured (clamped) between multiple fixed shape portions 7.

[0234] In addition, a plurality of dry friction materials 1 (three in the figure) are installed on a plate 6, and they are arranged at equal intervals in the circumferential direction of the plate 6.

[0235] In the torque limiting device 5, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A that contacts the plate 6, thereby making the coefficient of friction (μ) of the contact surface 1A higher than that of the contact surface 1B that abuts against the rubbed plate 121. In other words, the coefficient of friction (μ) of the contact surface 1A and the contact surface 1B of the dry friction material 1 is different.

[0236] When torque is transmitted using torque limiting device 5, the dry friction material 1 causes plate 6 and the rubbed plate 121 to move in coordination through the friction force generated by the contact surface 1B. When suppressing torque, the contact surface 1B slides relative to the rubbed plate 121, causing plate 6 to rotate relative to the rubbed plate 121 (slippage).

[0237] In the dry friction material 1, by having an anti-slip part 111, the coefficient of friction (μ) of the contact surface 1A is improved, and by preventing the contact surface 1A from sliding relative to the plate 6, it can always maintain a fixed state relative to the plate 6.

[0238] That is, by providing an anti-slip part 111 on the contact surface 1A, the dry friction material 1 can easily make the coefficient of friction (μ) of the contact surface 1A and the abutment surface 1B different. As a result, the torque limiting device 5 is able to perform its proper torque transmission and torque suppression functions.

[0239] Multiple (six in the figure, relative to three) dry friction materials 1 can be installed adjacent to each other in the circumferential direction relative to one plate 6. In this case, the overall shape of the multiple fan-shaped dry friction materials 1 is annular.

[0240] That is, the fan-shaped dry friction material 1 can be processed as a product that is segmented by dividing the annular dry friction material 1 into multiple segments.

[0241] Compared with annular dry friction materials, segmented dry friction material 1 can achieve increased yield (due to reduced material costs from smaller friction area and increased production from increased heat treatment input) while also improving design freedom (miniaturization, lightweighting, and rationalization of required values ​​(flatness deviation, cracking, etc.)).

[0242] Symbol Explanation 1: Dry friction material; 1A: Contact surface; 1B: Abutment surface. 2: Fixed shape part 11: Vulcanized rubber, 12: Reinforcing fiber, 111: Anti-slip part 5: Torque limiting device 6: Plate, 6A: Cover plate, 6B: Push plate 61: Mounting surface, 7: Fixed Shape Part 14: Engaging hole, 13: Engaging tab, 121: Friction plate.

Claims

1. A dry friction material, which is a dry friction material mounted on the surface of a plate in a torque limiting device, characterized in that, Includes reinforcing fibers and vulcanized rubber. The contact surface that contacts the surface of the plate has an anti-slip portion containing carbides.

2. The dry friction material as described in claim 1, wherein, The carbide is derived from the vulcanized rubber.

3. The dry friction material as described in claim 1 or 2, wherein, The contact surface is flat.

4. The dry friction material as described in claim 1 or 2, wherein, The reinforcing fibers are composed of short fibers and are oriented in a certain direction.

5. The dry friction material as described in claim 4, wherein, The dry friction material is in the shape of a ring-shaped flat plate. The orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

6. The dry friction material as described in claim 4, wherein, The dry friction material is in the shape of a fan-shaped flat plate. The orientation of the reinforcing fibers is parallel to the outer edge of the arc-shaped dry friction material.

7. The dry friction material as described in claim 4, wherein, The dry friction material is in the shape of a button-shaped flat plate. The orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

8. A torque limiting device comprising a dry friction material as described in claim 1 or 2, and a plate on which the dry friction material is mounted, characterized in that, The plate has multiple fixed-shape portions on the mounting surface where the dry friction material is installed. The dry friction material has a fixed shape portion that engages with the fixed shape portion.

9. The torque limiting device as claimed in claim 8, wherein, The dry friction material comprises short fibers oriented in a certain direction as reinforcing fibers.

10. The torque limiting device as claimed in claim 8 or 9, wherein, The mounting surface of the plate has a ring-shaped form when viewed from above. The dry friction material is in the shape of a ring-shaped flat plate. The dry friction material has the same number of fixed shape portions as the fixed shape portions. One of the dry friction materials is fixed to one of the mounting surfaces of the plate in a concentric circle.

11. The torque limiting device as claimed in claim 8 or 9, wherein, The mounting surface of the plate has a ring-shaped form when viewed from above. The dry friction material is in the shape of a fan-shaped flat plate. The dry friction material has the fixed shape portion at both ends. One of the dry friction materials is secured to a plurality of the fixed shape portions by the fixed shape portion, and a plurality of the dry friction materials are secured to one of the mounting surfaces of the plate.

12. The torque limiting device as claimed in claim 8 or 9, wherein, The mounting surface of the plate has a ring-shaped form when viewed from above. The dry friction material is in the shape of a button-shaped flat plate. The dry friction material has the fixed shape portion at its center. One of the dry friction materials is fixed to one of the fixed shape portions through the fixed shape portion, and a plurality of the dry friction materials are fixed on one of the mounting surfaces of the plate.

13. The torque limiting device as claimed in claim 8, wherein, The plates are a cover plate and a push plate. The cover plate and the push plate are configured such that the mounting surfaces on which the dry friction material is mounted are opposite each other. The friction plate is disposed between the cover plate and the push plate in a state of contact with the dry friction material.

14. A method for manufacturing a dry friction material as described in claim 1 or 2, characterized in that, It includes the process of applying localized heat treatment to the contact surface of the dry friction material to carbonize the vulcanized rubber on the surface of the contact surface, thereby forming the anti-slip part.

15. The method for manufacturing the dry friction material as described in claim 14, wherein, The localized heating treatment is laser treatment.

16. The method for manufacturing the dry friction material as described in claim 14 or 15, comprising: The process involves extruding a compound of uncured rubber, which will be formed into the vulcanized rubber, and the reinforcing fiber to obtain a composition for friction materials. as well as, The process of filling the cavity of a metal mold with the friction material composition and vulcanizing it to obtain the dry friction material having a skin layer formed on the surface in contact with the wall of the cavity.

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