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

Abstract

The present invention provides a dry friction material that allows the friction coefficient (μ) of a front surface and a back surface to be easily made different, a torque limiter device using the dry friction material, and a method for manufacturing the dry friction material. A dry friction material 1 is attached to a front surface of a plate 6 of a torque limiter device 5. The dry friction material 1 includes a reinforcement fiber 12 and a vulcanized rubber 11, and has a non-slip part 111 including a carbide on a contact surface 1A that is in contact with the front surface of the plate 6. The non-slip part 111 is formed by partially heating the contact surface 1A of the dry friction material 1 and carbonizing the vulcanized rubber 11 on a surface layer of the contact surface 1A.

Description

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

[0001] The present invention relates to a dry friction material, a torque limiter device, and a fixing structure for the dry friction material.

[0002] Hybrid vehicles and other vehicles are equipped with torque limiters that provide stable torque transmission and torque suppression (i.e., unit defense) functions when excessive torque occurs. The torque limiter device includes a ring-shaped plate to which a dry friction material is attached. Inside the torque limiter device, the dry friction material abuts its surface against a friction plate. During torque transmission, the dry friction material generates frictional forces on its surface, causing the plate to cooperate with the friction plate. During torque suppression, the dry friction material slides its surface against the friction plate. The dry friction material is attached to the plate by engaging holes on its back surface with pins on the plate's mounting surface. If the dry friction material slips against the plate during torque transmission or torque suppression, the force applied from the plate via the pin is received only by the holes, resulting in damage to the dry friction material. To prevent such damage, it is desirable to increase the friction coefficient (μ) of the dry friction material's back surface to suppress slippage of the back surface against the plate's mounting surface. Therefore, the dry friction material of a torque limiter device must have different coefficients of friction (μ) between its front and back surfaces so that its front surface can slide against the friction plate while preventing its back surface from sliding against the plate. An example of such a dry friction material that allows for different coefficients of friction (μ) between its front and back surfaces is the dry friction material described in Patent Document 1. The dry friction material described in Patent Document 1 is a flat ring-shaped dry friction material containing glass fiber, a synthetic resin for impregnating glass fiber, and compounded rubber, and the glass fiber content and compounded rubber content at the position of the fixed portion to the core material of the dry friction material differ from those at positions other than the fixed portion in one or both of the glass fiber content and the compounded rubber content. This dry friction material is manufactured by moving the glass fiber at the fixed portion or other than the fixed portion in one direction during molding to increase the glass fiber content or compounded rubber content at the fixed portion during molding in a molding process in which a circular preform is formed from the compounded material.

[0003] WO2012 / 014535

[0004] Specifically, the technology disclosed in Patent Document 1 uses a press die with ribs (protruding portions) protruding toward the molded body side (friction surface side), and when a preform is press-molded under high pressure, the ribs push the glass fibers in one direction, causing the glass fibers to be unevenly distributed, resulting in different glass fiber content and rubber content. However, in dry friction materials made using the above technology, grooves are formed by the ribs on the press die, which can easily lead to problems such as increased mold release resistance, reduced mold release properties, and reduced flatness of the front and back surfaces, requiring complicated work such as modifying the shape and polishing to improve flatness.

[0005] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a dry friction material that can easily make the friction coefficient (μ) of the front and back surfaces different, a torque limiter device using the dry friction material, and a method for manufacturing the dry friction material.

[0006] The present invention includes the following inventions. [1] A dry friction material attached to the surface of a plate in a torque limiter device, comprising reinforcing fibers and vulcanized rubber, and characterized in that the contact surface that comes into contact with the surface of the plate has an anti-slip portion containing carbide. [2] The dry friction material according to [1] above, wherein the carbide is derived from the vulcanized rubber. [3] The dry friction material according to [1] or [2] above, wherein the contact surface is flat. [4] The dry friction material according to any of [1] to [3] above, wherein the reinforcing fibers are short fibers and oriented in a fixed direction. [5] The dry friction material according to [4] above, wherein the shape of the dry friction material is a ring-shaped flat plate, and the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material. [6] The dry friction material according to [4] above, wherein the dry friction material has a fan-shaped flat plate shape, and the orientation of the reinforcing fibers is parallel to the outer edge of the arc-shaped dry friction material. [7] The dry friction material according to [4] above, wherein the dry friction material has a button-shaped flat plate shape, and the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material. [8] A torque limiter device comprising the dry friction material according to any of [1] to [7] above and a plate to which the dry friction material is attached, wherein the plate has a plurality of fixing shapes on a mounting surface to which the dry friction material is attached, and the dry friction material has fixing shapes that engage with the fixing shapes. [9] The torque limiter device according to [8] above, wherein the dry friction material includes short fibers oriented in a certain direction as the reinforcing fibers.

[10] The torque limiter device according to [8] or [9], wherein the mounting surface of the plate has a ring-shaped configuration in a plan view, the dry friction material has a ring-shaped flat plate shape, the dry friction material has the same number of fixed shape portions as the fixing shape portions, and one dry friction material is fixed concentrically to one mounting surface of the plate.

[11] The torque limiter device according to any one of [8] to

[10] above, wherein the mounting surface of the plate has a ring shape in a plan view, the dry friction material has a fan-shaped flat plate shape, the dry friction material has the fixed portion at both ends, one dry friction material is fastened to multiple fixed portions via the fixed portion, and multiple dry friction materials are fastened to one mounting surface of the plate.

[12] The torque limiter device according to any one of [8] to

[11] above, wherein the mounting surface of the plate has a ring shape in a plan view, the dry friction material has a button-shaped flat plate shape, the dry friction material has the fixed portion at a center, one dry friction material is fastened to one fixed portion via the fixed portion, and multiple dry friction materials are fastened to one mounting surface of the plate.

[13] The torque limiter device according to [8] above, wherein the plates are a cover plate and a push plate, the cover plate and the push plate are arranged with the mounting surfaces, on which the dry friction material is attached, facing each other, and a friction plate is disposed between the cover plate and the push plate in a state of abutting against the dry friction material.

[14] The method for manufacturing a dry friction material according to any of [1] to [7] above, comprising the steps of: subjecting the contact surface of the dry friction material to a partial heat treatment; and carbonizing the vulcanized rubber in the surface layer of the contact surface to form the anti-slip portion.

[15] The method for manufacturing a dry friction material according to

[14] above, wherein the partial heat treatment is laser treatment.

[16] A method for producing a dry friction material according to the above

[14] or

[15] , comprising the steps of: extruding a mixture of unvulcanized rubber to become the vulcanized rubber and the reinforcing fibers to obtain a friction material composition; and filling the friction material composition into a cavity of a mold and vulcanizing it to obtain the dry friction material having a skin layer formed on the surface that contacts the wall surface of the cavity.

[0007] According to the dry friction material of the present invention, the contact surface that comes into contact with the plate surface of the torque limiter device has an anti-slip portion containing carbide, so that the coefficient of friction (μ) of the front and back surfaces can be easily made different. According to the manufacturing method of the dry friction material of the present invention, the anti-slip portion can be provided by applying a partial heat treatment to the contact surface of the dry friction material, and complicated work such as work related to shape correction and work related to improving flatness by polishing, which has been required in the past, can be omitted, so that the coefficient of friction (μ) of the front and back surfaces can be easily made different.

[0008] 1 is a cross-sectional view illustrating a dry friction material according to the present invention.

[0023] FIG. 1 is a schematic diagram illustrating a dry friction material according to a first embodiment, where (a) is a plan view, (b) is a bottom view, (c) is a cross-sectional plan view, and (d) is a cross-sectional view taken along line dd-dd in (a).

[0024] FIG. 2 is a schematic diagram illustrating a dry friction material according to a second embodiment, where (a) is a partially cutaway plan view and (b) is a bottom view.

[0025] FIG. 3 is a schematic diagram illustrating a dry friction material according to a third embodiment, where (a) is a plan view, (b) is a cross-sectional plan view, and (c) is a bottom view.

[0026] FIG. 4 is a schematic diagram illustrating a torque limiter device, where a longitudinal cross-sectional view is shown in an assembled state.

[0027] FIG. 5 is a schematic diagram illustrating a plate of the torque limiter device according to the first embodiment, where (a) is a plan view and (b) is a cross-sectional plan view taken along line bb in (a).

[0028] FIG. 6 is a schematic diagram illustrating the torque limiter device according to the first embodiment, where a perspective view is shown in an exploded state. 1A and 1B are schematic diagrams illustrating plates of a torque limiter device of Example 2, where (a) is a plan view and (b) is a longitudinal cross-sectional view taken along line bb of (a). 1C are schematic diagrams illustrating plates of a torque limiter device of Example 3, where (a) is a plan view and (b) is a longitudinal cross-sectional view taken along line bb of (a). 1D are schematic diagrams illustrating the shape and arrangement of anti-slip portions on the contact surface of a dry friction material, where (a) to (h) are bottom views.

[0009] The present invention will be described below with reference to the drawings. The matters shown here are for illustrative purposes and are intended to exemplify embodiments of the present invention, and are set forth in order to provide what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this regard, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some aspects of the present invention can be actually embodied.

[0010] [1] Dry Friction Material The dry friction material 1 of the present invention is a dry friction material attached to the surface of a plate 6 in a torque limiter device 5, and is characterized in that it contains reinforcing fibers 12 and vulcanized rubber 11, and has an anti-slip portion 111 containing carbide on a contact surface 1A that comes into contact with the surface of the plate 6 (see FIG. 1).

[0011] The vulcanized rubber 11 contained in the dry friction material 1 is a material known as a "matrix component" and forms a parent phase (continuous phase) for the reinforcing fibers 12. The vulcanized rubber 11 is also a primary material for generating frictional force in the dry friction material 1 that comes into contact with a counter member in the torque limiter device 5. The type of vulcanized rubber is not particularly limited, and 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, acrylic rubber (acrylic ester / 2-chloroethyl vinyl ether copolymer rubber, acrylic ester / acrylonitrile copolymer rubber, etc.), urethane rubber, fluororubber (fluorinated olefin / vinylidene fluoride copolymer rubber, etc.), and silicone rubber. These vulcanized rubbers can be used alone or in combination of two or more types.

[0012] Among the above-mentioned vulcanized rubbers, NBR, SBR, BR, NR, IR, and CR are preferred as vulcanized rubbers contained in the dry friction material from the viewpoint of friction characteristics and impact resistance, with NBR and SBR being more preferred. The content of the vulcanized rubber 11 contained in the dry friction material 1 is not particularly limited, but can be 1 to 50 mass% when the entire dry friction material is taken as 100 mass%. The content of the vulcanized rubber is preferably 2 to 45 mass%, more preferably 3 to 40 mass%, even more preferably 4 to 35 mass%, and particularly preferably 5 to 30 mass%, and most preferably 6 to 25 mass%.

[0013] The dry friction material 1 may contain other components other than the vulcanized rubber as so-called "matrix components." The other components are not particularly limited, but may include cured resins (resins obtained by curing curable resins). The types of cured resins are not particularly limited, but may include phenolic resins (phenolic resins, novolac resins, resol resins, melamine-modified phenolic resins, etc.), urea resins, epoxy resins, polyimide resins, unsaturated polyester resins, alkyd resins, polyurethane resins, polyimide resins (curable polyimide resins), and modified resins thereof. These cured resins may be used alone or in combination of two or more.

[0014] Among the cured resins described above, phenolic resins and melamine-modified phenolic resins are preferred as cured resins contained in dry friction materials from the viewpoint of friction characteristics and impact resistance. Melamine-modified phenolic resins are thermosetting resins that use phenol and melamine as monomers. The composition ratio of melamine-modified phenolic resins is not limited. For example, when the total of the phenol-derived units and the melamine-derived units is taken as 100%, the melamine-derived units may be 30 to 80%. When the dry friction material 1 contains a cured resin, the amount of the cured resin is not particularly limited and can usually be determined depending on the amount of vulcanized rubber. For example, the amount of the cured resin may be 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, when the total vulcanized rubber is taken as 100 parts by mass.

[0015] When the dry friction material 1 contains a cured resin, it may contain a plasticizer as needed. The type of plasticizer can usually be selected appropriately depending on the type of cured resin, and is not particularly limited. The amount of plasticizer contained in the dry friction material 1 is not particularly limited, but may be, for example, 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, based on 100 parts by mass of the entire vulcanized rubber.

[0016] The reinforcing fibers 12 contained in the dry friction material 1 are a so-called "dispersion material" material, and are dispersed in the matrix phase (matrix component) of vulcanized rubber. The reinforcing fibers 12 are a material for reinforcing the vulcanized rubber to improve the strength, durability, etc. of the dry friction material 1. The reinforcing fibers 12 may be either organic or inorganic fibers, and are not particularly limited. However, from the viewpoints of the friction performance, heat resistance, safety, cost, etc. of the dry friction material 1, inorganic fibers are preferably used.

[0017] The type of inorganic fiber is not particularly limited, but examples include amorphous fibers (glass fibers, silica fibers, slag wool, rock wool, etc.), single crystal fibers (ceramic fibers, alumina fibers, magnesia fibers, titanate fibers, wollastonite fibers, etc.), polycrystalline fibers (ceramic fibers, alumina fibers, silica-alumina fibers, etc.), carbon-based fibers (carbon fibers, carbonized fibers, etc.), and metal fibers. These inorganic fibers may be used alone or in combination of two or more. Among the inorganic fibers described above, amorphous fibers and / or carbon-based fibers are preferred for the reinforcing fibers 12 of the dry friction material 1, and glass fibers and / or carbon fibers are more preferred, with glass fibers being particularly preferred.

[0018] The reinforcing fibers 12 may be heat-resistant. The specific heat resistance of the reinforcing fibers 12 is not particularly limited, but the melting point or decomposition temperature is preferably 200°C or higher, more preferably 350°C or higher. The upper limit of the melting point or decomposition temperature is not particularly limited, but can usually be 3500°C or lower. The shape of the reinforcing fibers 12 is not particularly limited, but the aspect ratio, which is the ratio of fiber length to fiber diameter (fiber length / fiber diameter), is preferably 50 or higher. The upper limit of the aspect ratio is not particularly limited, but can usually be 1000 or lower.

[0019] Both long fibers and short fibers can be used for the reinforcing fibers 12. The fiber lengths of the long fibers and short fibers are not particularly defined, but long fibers can be defined as fibers with a fiber length (maximum length) of 1000 m or more, and short fibers can be defined as fibers with a fiber length (maximum length) of approximately 1 mm to 128 mm. Long fibers (filaments) can be used as they are, but can also be used as strands in which multiple filaments are bundled together into a thread-like shape, or as rovings in which multiple strands are pulled together into a string-like or rope-like bundle. Short fibers (staples) can be used as they are, but can also be used as spun yarns in which multiple staples are twisted together, or as cabled yarns in which multiple spans are twisted together.

[0020] Here, many dry friction materials use roving (long fibers) as the reinforcing fibers to align the reinforcing fibers continuously in a uniform direction. To prevent the roving from fragmenting, such dry friction materials are manufactured by forming a preformed product in advance by coating the roving with a rubber material, followed by press molding under high pressure. Other methods, such as directly molding the dry friction material without forming a preform by extruding a mixture of rubber material and fibers into a mold, are difficult to adopt because they result in fragmented roving. Furthermore, the shapes that can be adopted for dry friction materials are limited to shapes such as ring shapes that minimize bending of the roving. In view of the above, it is preferable to use short fibers as the reinforcing fibers. That is, in the manufacture of dry friction materials using short fibers as the reinforcing fibers, methods such as extruding a mixture of fibers and rubber material into a mold can be used, and the molding method for dry friction materials is not substantially limited. For example, a method of molding a mixture of fibers and rubber material by extruding it into a mold allows the fibers to be oriented in the extrusion direction (a fixed direction) of the mixture in the mold, and a dry friction material obtained by this method has performance equivalent to that of a dry friction material using roving. Furthermore, when short fibers are used as reinforcing fibers, the fibers can be easily incorporated into a dry friction material without bending, and there are no practical limitations on the shape of the dry friction material that can be adopted.

[0021] As described above, short fibers can be used for the reinforcing fibers 12 from the viewpoint of suppressing fiber fragmentation and bending within the dry friction material 1 and improving and optimizing fiber orientation. In particular, when short fibers are used for the reinforcing fibers 12, a dry friction material with excellent dimensional accuracy and impact resistance can be obtained. The specific fiber length of the reinforcing fibers 12 is not particularly limited, but the average fiber length of the material fibers 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. The specific fiber diameter of the reinforcing fibers 12 is not particularly limited, but the average fiber diameter is preferably 0.5 to 20 μm, more preferably 2 to 15 μm, even more preferably 3 to 14 μm, and particularly preferably 6 to 13 μm. When the average fiber length and average fiber diameter are within the above ranges, the fibers can be easily oriented in a certain direction, which can significantly improve and optimize fiber orientation when short fibers are used for the reinforcing fibers 12.

[0022] The average fiber length and average fiber diameter are the average values ​​of the fiber length (maximum length) and fiber diameter (maximum diameter) measured for 50 randomly selected reinforcing fibers. Regarding the fiber length of the reinforcing fibers 12, the average fiber length of the material fibers used is the length when blended into the material for the dry friction material 1 (more specifically, the length when blended as material fibers to be used as reinforcing fibers when obtaining a kneaded product with unvulcanized rubber, etc.). The reinforcing fibers 12 in the dry friction material 1 may be broken during the manufacturing process of the dry friction material 1 (e.g., during extrusion of the kneaded product). Therefore, the actual fiber length of the reinforcing fibers 12 inside the dry friction material 1 may be shorter than the average fiber length.

[0023] The content of the reinforcing fibers 12 contained in the dry friction material 1 is not particularly limited, but is preferably 50 parts by mass to 300 parts by mass, more preferably 60 parts by mass to 280 parts by mass, even more preferably 80 parts by mass to 250 parts by mass, particularly preferably 100 parts by mass to 220 parts by mass, and especially preferably 120 parts by mass to 200 parts by mass. When the content of the reinforcing fibers 12 is within the above range, the fibers are easily oriented in a certain direction, and therefore, when short fibers are used as the reinforcing fibers 12, a significant effect can be obtained in improving and optimizing the orientation of the fibers.

[0024] When short fibers are used, the reinforcing fibers 12 may be included in the dry friction material 1 in a state where they are oriented in a certain direction. Here, the state where the reinforcing fibers 12 are oriented in a certain direction refers to a state where the extension directions (longitudinal directions) of the reinforcing fibers 12 dispersed in a matrix such as vulcanized rubber are aligned in a certain direction. The state where the extension directions (longitudinal directions) of the reinforcing fibers 12 are aligned in a certain direction is not limited to a state where the extension directions of all the reinforcing fibers 12 are substantially completely aligned in a predetermined direction, but also includes a state where the extension directions of at least some of the reinforcing fibers 12 are shifted by a certain range of crossing angles in a direction intersecting the predetermined direction. The crossing angle, where a state where the extension directions are completely aligned in the predetermined direction is defined as 0 degrees, may be 45 degrees or less, preferably 30 degrees or less, more preferably 20 degrees or less, and even more preferably 15 degrees or less.

[0025] Specifically, the orientation direction of the reinforcing fibers 12 is preferably parallel to the outer edge of the dry friction material (see FIGS. 1, 2(c), 3(a), 4(b), etc.). That is, the dry friction material 1 used in the torque limiter device 5 can have a circular or arc-shaped outer edge so that it rotates and slides against the friction plate. When the outer edge of the dry friction material 1 is circular or arc-shaped, the reinforcing fibers 12 are preferably oriented so that their longitudinal direction is parallel to the outer edge. In other words, the extension direction of the reinforcing fibers 12 is preferably approximately parallel to a tangent to the circular or arc-shaped outer edge of the dry friction material 1. Preferably, 50% or more of the number of reinforcing fibers 12 conform to this rule, and more preferably, 60% or more, even 70% or more, even 80% or more, even 90% or more, and even 95% or more of the number of reinforcing fibers 12 conform to this rule.

[0026] The dry friction material 1 may contain other components other than the reinforcing fibers 12 as so-called "dispersing materials." The other components are not particularly limited, but may include a friction modifier. The friction modifier is a material that contributes to the performance of the dry friction material, and in particular, a material that has a friction-modifying effect. The friction modifier has a non-fibrous form (a form obtained by excluding the fibrous form exhibited by the reinforcing fibers from the overall form) and has a form different from that of the reinforcing fibers. The type of friction modifier is not particularly limited, and may include inorganic friction modifiers (inorganic friction modifiers made of inorganic materials, complex inorganic friction modifiers mainly composed of inorganic materials but also containing organic materials, etc.) and organic friction modifiers (inorganic friction modifiers made of organic materials, complex inorganic friction modifiers mainly composed of organic materials but also containing inorganic materials, etc.). These may be used alone or in combination of two or more types.

[0027] The type of inorganic friction modifier is not limited, and examples thereof 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 (aluminum silicate, zirconium silicate), etc.}, hydroxide-based materials {metal hydroxides (calcium hydroxide, aluminum hydroxide), etc.}, oxide-based materials {metal oxides (zinc oxide [zinc oxide], titanium oxide, Examples of suitable materials include: sulfide-based materials {metal sulfides (molybdenum disulfide), non-metallic sulfides (antimony trisulfide), etc.}, carbide-based materials {metal carbides (titanium carbide), non-metallic carbides (silicon carbide, boron carbide), etc.}, nitride-based materials {non-metallic nitrides (silicon nitride, boron nitride, etc.)}, mineral-based materials (diatomaceous earth, wollastonite, dolomite, silica, mica, talc, kaolin, etc.), carbon-based materials (graphite, carbon black, coke, etc.), and metal materials (aluminum, copper, brass, etc.). These may be used alone or in combination of two or more. The type of organic friction modifier is not limited, and examples thereof include resins (cashew resin, melamine resin, cashew dust, etc.), rubber dust, plant materials (plant bark (cork, etc.), seed shells (walnut shells, coconut shells, etc.)), etc. These may be used alone or in combination of two or more.

[0028] The form of the friction modifier is not particularly limited as long as it is non-fibrous. Specifically, the aspect ratio, which is the ratio of the maximum length (major axis) to the minimum length (minor axis) of the particle size (maximum length / minimum length), is preferably less than 50 (1 or more). The maximum length of the particle size is preferably less than 500 μm, and more preferably less than 750 μm. That is, examples of the form of the friction modifier include granular, irregular, lumpy, needle-like, and whisker-like. The average particle size d of the friction modifier can be 0.1≦d (μm)<500 μm, or can be 1≦d (μm)≦350, or can be 2≦d (μm)≦200 μm. The average particle size of the friction modifier can be measured in accordance with JIS Z8827-1 (static image analysis method).

[0029] The content of the friction modifier in the dry friction material 1 is not limited, but may be 50 parts by mass or more and 1,000 parts by mass or less, further 60 parts by mass or more and 800 parts by mass or less, further 80 parts by mass or more and 600 parts by mass or less, further 90 parts by mass or more and 400 parts by mass or less, further 100 parts by mass or more and 350 parts by mass or less, or further 150 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the vulcanized rubber.

[0030] FIG. 1 is a schematic diagram illustrating the dry friction material of the present invention, showing a cross-sectional view of the dry friction material attached to a plate. The dry friction material 1 of the present invention is for use in a torque limiter device, and is attached to a mounting surface 61 of a plate 6 included in the torque limiter device when in use (see FIG. 1). The shape of the dry friction material 1 is not particularly limited as long as it can be attached to the plate 6 of the torque limiter device. The overall shape of the dry friction material 1 is not particularly limited, but can usually be a flat plate, as the dry friction material 1 is typically used by being sandwiched between the plate 6 and a friction plate. Shapes other than a flat plate include curved and corrugated plates.

[0031] The shape of the dry friction material 1 in a plan view is not particularly limited. Typically, the shape of the plate 6 in a plan view is ring-shaped (see FIG. 6( a)), and the shape of the dry friction material 1 in a plan view can be a shape that fits on the surface of the plate 6. Specific examples of the shape of the dry friction material 1 in a three-dimensional view include a button shape (see FIG. 2( a)), a ring shape (see FIG. 3( a)), and a sector shape (see FIG. 4( a)). Other examples of the shape in a plan view include a circle, an ellipse, a polygon, and an arc. The thickness of the dry friction material 1 is not particularly limited, but can be 2.0 mm or more and 2.6 mm or less. The thickness of the dry friction material 1 can be preferably 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.

[0032] The term "button-shaped" refers to a small piece-like shape having a predetermined thickness. More specifically, it refers to a shape in which the maximum length in a plan view is greater than the thickness in a side view. The shape in a plan view is not limited, but may be, for example, a circle (see FIG. 2(a)), an ellipse, a polygon, or the like. Specifically, in the case of a button-shaped shape, the maximum length in a plan view may be 8 mm or more and 30 mm or less, the thickness in a side view may be 1 mm or more and 5 mm or less, and the ratio of the maximum length to the thickness (maximum length / thickness) may be 1.6 to 30. The term "ring-shaped" refers to an annular shape having a predetermined thickness. More specifically, it refers to a shape in which the outer diameter and inner diameter in a plan view are greater than the thickness in a side view. The shape in a plan view is not limited, but may be, for example, a circular ring (see FIG. 3(a)), an elliptical ring, or a polygonal ring. Specifically, in the case of a ring shape, the outer diameter in plan view can be preferably 100 mm or more and 300 mm or less, more preferably 150 mm or more and 240 mm or less, and the thickness in side view can be 1 mm or more and 5 mm or less. Furthermore, a "fan shape" refers to an arc-shaped shape having a predetermined thickness and a constant width. More specifically, it refers to a shape in which the width in plan view is greater than the thickness in side view. The shape in plan view can be an arc shape (see FIG. 4(a)). Specifically, in the case of a fan shape, the shape in plan view can be a shape obtained by dividing a circle into three to six parts, in other words, a shape having an arc with a central angle of 60 degrees to 120 degrees.

[0033] The dry friction material 1 can have a fixed shape portion 2 on the contact surface 1A as a fixing structure for fixing to the plate 6 (see FIGS. 2(b), 3(b), and 4(c)). The shape of the fixed shape portion 2 is not particularly limited, and can be, for example, a circle, an ellipse, a polygon, an arc, or the like when viewed from above. Furthermore, the shape of the fixed shape portion 2 when viewed from above can be a concave shape (see FIG. 2(d)), a convex shape, a notched shape (see FIG. 4(b)), a through hole, or the like when viewed from above. The size of the fixed shape portion 2 when viewed from above is not particularly limited, and can be determined appropriately depending on the shape of the fixed shape portion 2, the size of the fixing shape portion 7 provided on the mounting surface 61 of the plate 6, and the like.

[0034] When the cross-sectional shape of the fixed shape portion 2 is concave, the depth of the concave shape from the contact surface 1A can be, for example, 1.2 mm or more, and preferably 1.5 mm to 1.7 mm. Usually, the depth of the concave shape from the contact surface 1A is equal to or less than the thickness of the dry friction material 1, and when the depth of the concave shape is the same as the thickness of the dry friction material 1, the cross-sectional shape of the fixed shape portion 2 becomes a through-hole. When the cross-sectional shape of the fixed shape portion 2 is convex, the height of the convex shape from the contact surface 1A can be, for example, 1.0 mm to 2.0 mm, and preferably 1.1 mm to 1.3 mm.

[0035] In the dry friction material 1, the contact surface 1A that comes into contact with the mounting surface 61 of the plate 6 has an anti-slip portion 111 containing carbide (see FIG. 1 ). The contact surface 1A of the dry friction material 1 has the anti-slip portion 111, which prevents the dry friction material 1 from slipping relative to the mounting surface 61 of the plate 6. In other words, when the torque limiter device transmits torque or limits torque, the dry friction material 1 is prevented from sliding relative to the plate 6 by the friction force generated at the contact surface 1A having the anti-slip portion 111. The dry friction material 1, whose sliding relative to the plate 6 is prevented, is fixed to the plate 6 by being kept immovable on the mounting surface 61 of the plate 6. In other words, the dry friction material 1 has the anti-slip portion 111 on the contact surface 1A as a fixing structure for fixing the dry friction material 1 to the mounting surface 61 of the plate 6.

[0036] The dry friction material 1 has an abutment surface 1B facing the contact surface 1A. The abutment surface 1B of the dry friction material 1 can abut against a friction plate provided in a torque limiter device. When torque is transmitted by the torque limiter device, the friction force generated at the abutment surface 1B causes the plate 6 to cooperate with the friction plate, and when torque is restricted, the abutment surface 1B slides against the friction plate, causing the plate 6 to slide.

[0037] During torque suppression, the dry friction material 1 allows the contact surface 1B to slide against the friction plate, but prevents the contact surface 1A from sliding against the plate 6. For this reason, the dry friction material 1 has different friction coefficients (μ) between the contact surface 1A and the contact surface 1B. Specifically, the contact surface 1A has the anti-slip portion 111, so that its friction coefficient (μ1) is higher than the friction coefficient (μ2) of the contact surface 1B (μ1>μ2).

[0038] The coefficient of friction (μ1) of the contact surface 1A is not limited, but the ratio (μ1 / μ2) to the coefficient of friction (μ2) of the abutting surface 1B can be preferably greater than 1 and less than 5 [1 < (μ1 / μ2) ≦ 5], more preferably 1.1 to 4 [1.1 ≦ (μ1 / μ2) ≦ 4], even more preferably 1.3 to 3 [1.3 ≦ (μ1 / μ2) ≦ 3], and particularly preferably 1.5 to 2.5 [1.5 ≦ (μ1 / μ2) ≦ 2.5]. The shape of the contact surface 1A is not particularly limited and can be flat, uneven, curved, etc. However, it is preferable that the contact surface 1A have the same shape as the mounting surface 61 of the plate 6, from the viewpoint that by having a shape that corresponds to the shape of the mounting surface 61 of the plate 6, the contact area with the mounting surface 61 is increased, the friction force is increased, and the fixing force of the dry friction material 1 to the plate 6 is increased. Since the surface shape of the mounting surface 61 of the plate 6 is usually flat, it is preferable that the surface shape of the contact surface 1A is also flat.

[0039] The anti-slip portion 111 contains carbide, and when the anti-slip portion 111 contacts the plate 6, the contact surface 1A of the dry friction material 1 can have a friction coefficient (μ1) that is different from the friction coefficient (μ2) of the abutment surface 1B. For this reason, the anti-slip portion 111 is preferably exposed to the outside at the contact surface 1A of the dry friction material 1. The type of carbide contained in the anti-slip portion 111 is not particularly limited, and examples thereof include carbon, graphite, carbon sulfide, carbon chloride, carbon fluoride, and silicon carbide. The amount of carbide contained in the anti-slip portion 111 is not particularly limited, but the lower limit can be set to 50 parts by mass or more, assuming that the total amount of the anti-slip portion 111 is 100 parts by mass. The lower limit of the amount of carbide contained in the anti-slip portion 111 is preferably 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 non-slip portion 111 is usually 100 parts by mass, and in the case of this 100 parts by mass, the non-slip portion 111 can be formed only from carbide.

[0040] The method of providing the anti-slip portions 111 on the contact surface 1A is not particularly limited, and examples thereof include carbonizing the vulcanized rubber or the like contained in the contact surface 1A by heating, or applying the above-mentioned carbide to the contact surface 1A by painting, gluing, or the like. The shape and arrangement of the anti-slip portions 111 on the contact surface 1A are not particularly limited. When the contact surface 1A is viewed from above (or the dry friction material 1 is viewed from the bottom), the shape of the anti-slip portions 111 may be a continuous band as shown in FIG. 10( a), an intermittent band as shown in FIG. 10( b), a circle as shown in FIG. 10( c), an ellipse as shown in FIG. 10( d), a continuous line as shown in FIG. 10( e), a chain line as shown in FIG. 10( f), or the like. When the shape of the anti-slip portions 111 is circular in a plan view (bottom view), the arrangement of the anti-slip portions 111 may be a checkerboard pattern as shown in FIG. 10( g), a staggered pattern as shown in FIG. 10( h), or the like.

[0041] 10(a) to 10(d) show a configuration in which only one row of anti-slip portions 111 is provided, but this is not a limitation and multiple rows of anti-slip portions 111 may be provided. 10(e) to 10(f) show a configuration in which two rows of anti-slip portions 111 are provided, but this is not a limitation and multiple rows of anti-slip portions 111 may be provided. 10(g) to 10(h) show a configuration in which two rows of anti-slip portions 111 are provided, but this is not a limitation and multiple rows of anti-slip portions 111 may be provided. Alternatively, the anti-slip portions 111 may be arranged in an irregular, random pattern, for example, rather than in a checkerboard or staggered pattern.

[0042] The non-slip portion 111 may contain a material other than a carbide, and examples of the material other than a carbide include rubbers such as vulcanized rubber, fibers such as reinforcing fibers, resins such as cured resins, friction modifiers, etc. Specifically, the material other than a carbide contained in the non-slip portion 111 is mainly materials that have not been carbonized by heating or the like when the non-slip portion 111 is provided on the contact surface 1A by heating or the like, and is mainly solvents, adhesives, pressure-sensitive adhesives, etc. when the non-slip portion 111 is provided on the contact surface 1A by coating or the like with a carbide.

[0043] The size of the anti-slip portion 111 is not particularly limited. When the contact surface 1A is viewed from above (or when the dry friction material 1 is viewed from the bottom), the anti-slip portion 111 can be provided partially on a part of the contact surface 1A, as shown in FIGS. 10( a) to 10(h), or can be provided entirely on the entire contact surface 1A, i.e., the entire contact surface 1A can be the anti-slip portion 111. For example, the size of the anti-slip portion 111 can be 0.1% to 100%, preferably 1% to 70%, more preferably 3% to 50%, and even more preferably 5% to 30%, of the area of ​​the contact surface 1A, assuming the total area of ​​the contact surface 1A to be 100. The thickness of the anti-slip portion 111 is not particularly limited, but the lower limit can be 1 μm or more. The lower limit of the thickness can be preferably 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 1 mm or less. The upper limit of the thickness is preferably 500 μm or less, and more preferably 300 μm or less.

[0044] The carbide contained in the anti-slip portion 111 may be derived from the vulcanized rubber 11 described above. Specifically, the carbide contained in the anti-slip portion 111 may be formed by carbonizing the vulcanized rubber on the surface layer of the contact surface 1A by, for example, heating the contact surface 1A of the dry friction material 1. The method for carbonizing the vulcanized rubber on the surface layer of the contact surface 1A is not particularly limited, but examples include laser treatment, burner treatment, and hot plate treatment. Among these, laser treatment is a preferred method because it can heat only the surface layer of the contact surface to a high temperature and suitably and easily carbonize the vulcanized rubber on the surface layer.

[0045] [2] Torque limiter device The torque limiter device 5 of the present invention comprises a dry friction material 1 and a plate 6 to which the dry friction material 1 is attached, the plate 6 having a plurality of fixing shaped portions 7 on a mounting surface 61 to which the dry friction material 1 is attached, and the dry friction material 1 having fixed shaped portions 2 that engage with the fixing shaped portions 7 (see FIGS. 5 to 8). The dry friction material 1 included in the torque limiter device 5 can be the dry friction material described in [1] above.

[0046] The plate 6 provided in the torque limiter device 5 is not particularly limited as long as it can be fitted with the dry friction material 1, but typically a cover plate 6A or a push plate 6B can be used (see FIG. 5). The cover plate 6A and the push plate 6B are the plates 6 provided in the torque limiter device 5, and are fitted with the dry friction material 1. The cover plate 6A and the push plate 6B are arranged so that their mounting surfaces 61, on which the dry friction material 1 is fitted, face each other. A friction plate 121 can be arranged between the cover plate 6A and the push plate 6B in a state of contact with the dry friction material 1.

[0047] Alternatively, the torque limiter device 5 may employ a configuration in which the plate 6 is one or more intermediate plates disposed between the cover plate 6A and the push plate 6B. In this case, the intermediate plate has both the front and back surfaces as mounting surfaces, and the dry friction material 1 is fixed to these mounting surfaces. Furthermore, a friction plate 121 may be 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.

[0048] The plate 6 can usually be shaped like a ring-like flat plate (see FIGS. 6(a) and 6(b)). When the plate 6 is a cover plate 6A and a push plate 6B, an engagement hole 14 can be formed in the cover plate 6A, and an engagement protrusion 13 can be formed in the push plate 6B (see FIGS. 7 and 8). The engagement hole 14 is formed by penetrating the cover plate 6A in its thickness direction. The engagement protrusion 13 is formed by protruding from the outer peripheral edge of the push plate 6B in a direction facing the cover plate 6A. The engagement hole 14 of the cover plate 6A and the engagement protrusion 13 of the push plate 6B engage with each other, making the cover plate 6A and the push plate 6B non-rotatable relative to each other around the axis C but movable relative to each other in the axial direction. The push plate 6B is biased toward the cover plate 6A by a biasing means (not shown).

[0049] The plate 6 and the friction plate 121 can usually be made of a metal such as stainless steel. The surface of the plate 6 can serve as a mounting surface 61 to which the dry friction material 1 is attached. There is no particular limitation on which part of the surface of the plate 6 serves as the mounting surface 61, but specifically, the part that comes into contact with the friction plate 121 serves as the mounting surface 61. For example, in the case of the cover plate 6A and the push plate 6B, the part on their surfaces that comes into contact with the friction plate 121 disposed between them can serve as the mounting surface 61. The mounting surface 61 of the plate 6 can be surface-treated by coating or the like. The surface-treated mounting surface 61 can have a friction coefficient (μ3) that is higher than the friction coefficient (μ4) of the surface of the friction plate 121 (μ3 > μ4).

[0050] The mounting surface 61 of the plate 6 is provided with a fixing shape portion 7 as a fixing structure for fixing the dry friction material 1. A plurality of (six in the figure) fixing shape portions 7 may be arranged parallel to the inner peripheral edge or the outer peripheral edge of the plate 6 (see FIGS. 6( a) and 6(b)). The plurality of fixing shape portions 7 may be arranged on the same circumference on the mounting surface 61 of the plate 6. Furthermore, the plurality of fixing shape portions 7 may be arranged at equal intervals. Note that "parallel" means that an imaginary line connecting the centers of the plurality of arranged fixing shape portions 7 is substantially circular and substantially concentric with the inner peripheral edge and the outer peripheral edge of the plate 6.

[0051] The shape of the fixing portion 7 is not particularly limited, but can usually be a shape that can engage with the fixing portion 2 of the dry friction material 1. That is, the shape of the fixing portion 7 can be a circle, ellipse, polygon, arc, or the like when viewed from above. Furthermore, the shape of the fixing portion 7 when viewed from a cross section can be a convex shape, a concave shape, a through-hole shape, or the like that corresponds to the cross-sectional shape of the fixing portion 2 (see FIGS. 6( a) and 6(b)). The size of the fixing portion 2 is not particularly limited, and can be determined appropriately depending on the shape of the fixing portion 2, the size of the fixing portion 7 provided on the mounting surface 61 of the plate 6, and the like. When the fixing portion 2 is convex, the height of the convex shape can be 1.0 mm to 2.0 mm, and preferably 1.1 mm to 1.3 mm. When the fixing portion 2 is concave, the depth of the concave shape can be 1.2 mm or more, and preferably 1.5 mm to 1.7 mm. The depth of the recess is usually equal to or less than the thickness of the plate 6, and when the depth of the recess is equal to the thickness of the plate 6, the fixed shape portion 7 has a through-hole shape.

[0052] The number of dry friction materials 1 attached to the plate 6 is not particularly limited, and may be one or more than one. Usually, the number of dry friction materials 1 attached can be determined depending on the shape of the dry friction material 1 and the number of fixed shaped portions 2 provided thereon. For example, if the shape of the dry friction material 1 in a plan view is button-shaped, the number of dry friction materials 1 attached to the plate 6 may be multiple and may be the same as the number of fixed shaped portions 7 of the plate 6. If the shape of the dry friction material 1 in a plan view is fan-shaped, the number of dry friction materials 1 attached to the plate 6 may be multiple and may be half or less the number of fixed shaped portions 7 of the plate 6.

[0053] That is, in attaching the dry friction material 1 to the plate 6, for example, one dry friction material 1 can be fixed to one fixing portion 7. Specifically, the fixing portion 2 provided at the center of the bottom surface of the button-shaped dry friction material 1 fits into the fixing portion 7 provided on the surface of the plate 6, thereby fixing one dry friction material 1 to one fixing portion 7. In this configuration, when the dry friction materials 1 are arranged at equal intervals in the circumferential direction of the plate 6, the fixing portions 7 are also usually arranged at equal intervals.

[0054] Furthermore, one dry friction material 1 can be fixed to a plurality of fixing portions 7 via fixed portions 2. Specifically, the fixed portions 2 provided at both ends of the fan-shaped dry friction material 1 in the arc direction engage with the fixing portions 7 provided on the surface of the plate 6, so that one dry friction material 1 can be fixed (sandwiched) between a plurality of fixing portions 7. In this configuration, when the dry friction materials 1 are arranged at equal intervals in the circumferential direction of the plate 6, the pairs of fixing portions 7 corresponding to both ends of one dry friction material 1 are also usually arranged at equal intervals.

[0055] Alternatively, a plurality of fixed shape portions 2 provided on the contact surface 1A of the ring-shaped dry friction material 1 may be fitted into a plurality of fixed shape portions 7 provided on the surface of the plate 6, so that one dry friction material 1 is fixed to one plate 6. In this embodiment, the number of fixed shape portions 2 provided on one dry friction material 1 is the same as the number of fixed shape portions 7 of the plate 6.

[0056] When a plurality of dry friction materials 1 are attached to the plate 6, the dry friction materials 1 may be arranged near the inner peripheral edge and / or the outer peripheral edge of the attachment surface 61 of the plate 6. Alternatively, the dry friction materials 1 may be arranged in the middle between the inner peripheral edge and the outer peripheral edge of the attachment surface 61 of the plate 6. Furthermore, two or more of the above-mentioned arrangements of the dry friction materials 1 may be combined.

[0057] Regarding the above arrangement, for example, all of the dry friction materials 1 may be arranged on one circumference on the surface of the plate 6. Alternatively, a plurality of dry friction materials 1 may be arranged on each of a plurality of circumferences having different diameters on the surface of the plate 6. Alternatively, depending on the design conditions of the plate 6 (for example, the position of the engagement holes), some of the dry friction materials 1 may be arranged off the circumference.

[0058] In the above arrangement, for example, the dry friction materials 1 may be arranged at equal intervals on one circumference. Alternatively, depending on the design conditions of the plate 6 (for example, the position of the engagement holes), some or all of the dry friction materials 1 may be arranged at unequal intervals in the circumferential direction of the plate 6.

[0059] For example, the dry friction material 1 may be bonded to the surface of the plate 6 with an adhesive or the like. However, from the viewpoint of workability and the like, it is preferable that the dry friction material 1 is not bonded to the surface of the plate 6, but is fixed by the engagement relationship between the fixed shape portion 2 and the fixing shape portion 7.

[0060] [3] Manufacturing Method of Dry Friction Material The manufacturing method of the dry friction material of the present invention includes a step of partially heating 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 portion.

[0061] The dry friction material produced by the production method of the present invention can employ the dry friction material described in [1] above. The dry friction material is obtained by forming an anti-slip portion on the contact surface by performing a partial heat treatment. This partial heat treatment is a process of partially heating the dry friction material, specifically a process of heating only the surface layer of the contact surface of the dry friction material, and is different from the so-called "heat treatment" in which the dry friction material is heated as a whole. The partial heat treatment is not particularly limited as long as it can heat only the surface layer of the contact surface of the dry friction material, and examples of the partial heat treatment include laser treatment, burner treatment, and hot plate treatment. Among these, laser treatment is preferred as the partial heat treatment because it heats only the surface layer of the contact surface to a high temperature and can carbonize the vulcanized rubber in that surface layer in a short period of time.

[0062] In the laser treatment, the type of heat source is not particularly limited. ２ Lasers such as a YAG laser, a YLF laser, and a Yb laser can be used. The output power in the laser treatment is not particularly limited, and an output power capable of carbonizing the vulcanized rubber contained in the dry friction material can be selected as needed. For example, the output power can be 1 J to 20 J, preferably 2 J to 15 J, and more preferably 3 J to 10 J. The wavelength and pulse width in the laser treatment are not particularly limited, and an output power capable of carbonizing the vulcanized rubber contained in the dry friction material can be selected as needed. The oscillation mode can be either continuous or pulsed.

[0063] In laser treatment, only the area of ​​the contact surface irradiated with laser light is heated to a high temperature, carbonizing the vulcanized rubber and forming a non-slip portion. The size of the non-slip portion on the contact surface can be determined depending on the area of ​​irradiation with the laser light. The area of ​​irradiation with the laser light is usually a part of the contact surface from the viewpoint of maintaining an effective focal length, and in this case, the non-slip portion can be formed in a line or band shape on the contact surface. Furthermore, if the irradiation area is expanded to cover the entire contact surface by, for example, appropriately moving the irradiation position of the laser light, the non-slip portion can be formed over the entire contact surface.

[0064] The manufacturing method of the present invention can include the steps of: extruding a mixture of the unvulcanized rubber that will become the vulcanized rubber and the reinforcing fibers to obtain a friction material composition; and filling the friction material composition into a cavity of a mold and vulcanizing it to obtain the dry friction material having a skin layer formed on the surface that contacts the wall surface of the cavity.

[0065] In the manufacturing method of a dry friction material, a friction material composition is used to obtain the dry friction material. This friction material composition can be obtained by extruding a mixture of unvulcanized rubber to be vulcanized rubber and reinforcing fibers (material fibers used for the reinforcing fibers). The reinforcing fibers are as described in the dry friction material described in [1] above. The unvulcanized rubber is a precursor to the vulcanized rubber contained in the dry friction material described in [1] above. To convert the unvulcanized rubber into vulcanized rubber by vulcanization, the mixture can contain a vulcanizing agent (crosslinking agent) and a vulcanization accelerator (crosslinking accelerator).

[0066] The type of vulcanizing agent is not limited, and examples thereof 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, quinoid-based vulcanizing agents, and maleimide-based vulcanizing agents. These may be used alone or in combination of two or more. Among these, sulfur-based vulcanizing agents include sulfur (powdered sulfur, sulfur flowers, surface-treated sulfur, colloidal sulfur, etc.) and sulfur chloride. Furthermore, 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. Examples of polyamine vulcanizing agents include hexamethylenediamine carbamate, hexamethylenediamine, triethylenetetramine, tetraethylenepentamine, and ammonium benzoate. Examples of polyol vulcanizing agents include bisphenol, hydroquinone, and pentaerythritol. Examples of metal soap vulcanizing agents include sodium stearate, potassium stearate, sodium oleate, and potassium oleate. These may be used alone or in combination of two or more.

[0067] The type of vulcanization accelerator is not limited, and examples thereof include hexamethylenetetramine, butylaldehyde-monobutylamine condensates, tricrotonylidenetetramine, guanidine salts such as diphenylguanidine, thiazoles such as imidazoline and mercaptothiazoline, sulfenamide, thiocarbamide, thioureas such as diethyl thiourea and dibutyl thiourea, dithiocarbamates such as sodium dimethyl dithiocarbamate, thiuram compounds, thioglycolic acid esters, etc. These may be used alone or in combination of two or more.

[0068] Specifically, the method for producing a dry friction material can include a rubber kneading step, an extrusion step, and a thermoforming step. The rubber kneading step is a step for obtaining a kneaded mixture of unvulcanized rubber and reinforcing fibers. The extrusion step is a step for extruding the kneaded mixture to obtain a friction material composition. The thermoforming step is a step for filling the friction material composition into a cavity of a mold and vulcanizing it to obtain a dry friction material having a skin layer formed on the surface layer that contacts the wall surface of the cavity.

[0069] In the rubber kneading process, the unvulcanized rubber, reinforcing fibers, and vulcanizing agents may be kneaded in any manner. For example, kneaders such as extruders (single-screw extruders, twin-screw extruders, etc.), kneaders, and mixers (high-speed fluid mixers, paddle mixers, ribbon mixers, etc.) can be used. These kneaders may be used alone or in combination of two or more. When two or more kneading gases are used, they may be used continuously or in a batch system. Furthermore, the raw materials may be kneaded all at once or may be added in multiple stages in multiple batches. Furthermore, the kneading temperature during kneading is not limited, but may be, for example, 25°C to 400°C, 50°C to 350°C, 75°C to 325°C, or 100°C to 300°C.

[0070] In the extrusion process, extruding the kneaded material allows the reinforcing fibers in the extruded material to be oriented. The kneaded material may be extruded in any manner, including, for example, a single-screw extruder, a twin-screw extruder, or a 1.5-screw extruder. In the thermoforming process, the friction material composition filled into the cavity of a mold and vulcanized forms a skin layer in the surface layer that contacts the cavity wall, as the vulcanized rubber quickly hardens. This skin layer becomes substantially free of reinforcing fibers as the reinforcing fibers are pushed inward by shrinkage and hardening due to vulcanization. The non-slip portion can be formed by carbonizing this skin layer (vulcanized rubber), and can be substantially free of chars derived from the reinforcing fibers. In other words, by making the non-slip portion contain only chars derived from the vulcanized rubber, it is possible to eliminate the instability of the friction coefficient (μ) caused by the presence of foreign matter such as chars derived from the reinforcing fibers.

[0071] The thermoforming process can include an extrusion process by combining the filling of the friction material composition into a mold with the extrusion of the kneaded material in the extrusion process. In this case, the mold can be, for example, a molding die equipped with a preliminary cavity for accommodating the kneaded material, a molding cavity for molding a precursor (a shaped material before vulcanization) to become the dry friction material, and a runner connecting the preliminary cavity and the molding cavity. That is, the kneaded material is accommodated in the preliminary cavity, and the kneaded material is transferred from the preliminary cavity to the molding cavity via the runner by pressing, so that the kneaded material can be extruded as it moves from the runner to the mold cavity. This allows the reinforcing fibers in the kneaded material accommodated in the molding cavity to be oriented in a certain direction.

[0072] The above-mentioned extrusion operation may be performed only once or multiple times. Performing multiple extrusions means performing another extrusion operation on the extruded mixture (hereinafter simply referred to as the "extrudate"). 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 an operation that reduces the orientation of the reinforcing fibers on the extrudate. In other words, it is preferable not to perform an operation such as kneading or pelletizing the extrudate. When inorganic fibers are used as the reinforcing fibers, the fibers themselves have appropriate rigidity. For this reason, by flowing the kneaded mixture, the reinforcing fibers can be easily oriented in the same direction, and the reinforcing fibers can be oriented in an elongated state without being bent. Furthermore, it is also preferable that the reinforcing fibers are less likely to be broken down when the kneaded mixture is flowed, and their length can be maintained.

[0073] The shape of the extrudate is not limited, and can be columnar (including continuous linear), tubular, sheet-like, etc., of which columnar or tubular shapes are preferred, and columnar shapes are more preferred. Therefore, the die used for extrusion is also not limited, but a die capable of shaping the extrudate into a columnar or tubular shape is preferred, and a die capable of shaping into a columnar shape is more preferred. Furthermore, when the extrudate is columnar, its cross-sectional shape is not limited, and can be circular, polygonal (triangular, rectangular), etc., of which circular shapes are preferred. Note that the circular shape includes not only perfect circles, but also ellipses, teardrop shapes, etc., in which at least a portion of the outer edge is curved.

[0074] When the extrudate is formed into a cylindrical shape (including a continuous linear shape with a circular cross section), the diameter is not limited in view of the fluidity of the mixture of unvulcanized rubber and reinforcing fibers, the average length of the reinforcing fibers, etc., but can be, for example, 1 mm to 50 mm, 2 mm to 40 mm, 3 mm to 30 mm, 4 mm to 25 mm, or 5 mm to 20 mm.

[0075] It is preferable that all reinforcing fibers have the same orientation, and typically, 50% or more of the reinforcing fibers have the same orientation. From the viewpoint of improving dimensional stability and impact strength, this percentage is preferably larger, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, particularly preferably 90% or more, and most preferably 95% or more. Note that the orientation of the reinforcing fibers obtained by the extrusion process is not obtained by individually orienting all of the contained reinforcing fibers. For this reason, it is extremely difficult to unambiguously identify or quantify, for example, the number of reinforcing fibers oriented in a first direction and the number of reinforcing fibers oriented in a second direction. Therefore, directly identifying the orientation of the reinforcing fibers in dry friction materials is generally impractical, and in some cases impossible or impractical.

[0076] Dry friction materials are produced by vulcanizing a friction material composition by heating in a thermoforming process. Vulcanization is usually carried out using the vulcanizing agent, vulcanization accelerator, etc. The heating temperature during vulcanization is not limited, but may be, for example, 100°C to 400°C, 110°C to 350°C, 115°C to 300°C, or 120°C to 250°C.

[0077] The dry friction material 1 described above has an anti-slip portion 111 on the contact surface 1A with a mating member such as a plate, thereby making the coefficient of friction (μ) of the contact surface 1A different from that of the abutment surface 1B. In this method for producing a dry friction material, the anti-slip portion can be formed by carbonizing a skin layer (vulcanized rubber) formed on the surface by contacting the friction material composition with the wall surface of the cavity through partial heating treatment such as laser treatment. That is, the method for producing the dry friction material described above does not require uneven distribution of the reinforcing fibers (glass fibers) by providing ribs (protrusions) on a mold as in the conventional method, and does not require work such as modifying the shape associated with forming such ribs (protrusions). Furthermore, while the skin layer, which allows the mating member such as a plate to slide, must be removed by grinding or the like in the conventional method for producing a dry friction material, the method for producing the dry friction material described above utilizes the skin layer to form the anti-slip portion, eliminating the need for work such as grinding. Therefore, according to the method for producing a dry friction material of the present invention, by providing an anti-slip portion by partially heating the dry friction material, it is possible to easily make the coefficients of friction (μ) of the front and back surfaces of the dry friction material different from each other without the need for complicated work such as work to modify the shape or work to improve flatness by polishing.

[0078] The present invention will be explained in more detail below with reference to Examples 1 to 3.

[0079] 2(a) to 2(d), the dry friction material 1 is formed in a circular button shape in plan view, and a fixed shape portion 2 is provided in the center of the bottom surface. The fixed shape portion 2 has a circular concave shape in plan view. The reinforcing fibers 12 are made of short fibers and are oriented to describe a circle that is parallel to the outer periphery of the dry friction material 1. An anti-slip portion 111 is formed on the contact surface 1A, which is the bottom surface of the dry friction material 1. The anti-slip portion 111 is formed in a linear shape that describes a circle by irradiating a laser beam in a circular manner on the radially middle portion of the contact surface 1A.

[0080] As shown in Figures 6(a), 6(b) and 7, the torque limiter device 5 includes a plate 6 and a dry friction material 1 fixed onto the surface of the plate 6. The plate 6 has a fixing shape portion 7 for fixing to a mounting surface 61. The fixing shape portion 7 has a convex shape (see Figure 6(b)) and a circular shape in a plan view.

[0081] The plate 6 has a ring-shaped shape in a plan view. A plurality of fixed shape portions 7 and dry friction materials 1 (six in the figure) are provided parallel to the inner or outer peripheral edge of the plate 6. The fixed shape portions 7 and dry friction materials 1 are all arranged on the same circumference on the surface of the plate 6. Furthermore, the fixed shape portions 7 and dry friction materials 1 are arranged at equal intervals.

[0082] In the plate 6, one dry friction material 1 is fixed to one fixing portion 7. Specifically, the fixed portion 2 of the dry friction material 1 is fitted into the fixing portion 7 of the plate 6, so that one dry friction material 1 is fixed to one fixing portion 7.

[0083] Specifically, the torque limiter device 5 includes a cover plate 6A and a push plate 6B as plates 6. These plates 6A and 6B are arranged with their mounting surfaces 61 (surfaces) facing each other, to which the dry friction material 1 is attached. Furthermore, a friction plate 121 is disposed between the plates 6A and 6B in a state of contact with the contact surface 1B of the dry friction material 1.

[0084] The push plate 6B is provided with an engagement protrusion 13 extending in the direction of the axis C. The cover plate 6A is provided with an engagement hole 14 that engages with the engagement protrusion 13. By engaging the engagement protrusion 13 with the engagement hole 14, the cover plate 6A and the push plate 6B are unable to rotate relative to each other around the axis C but are able to move relative to each other in the axial direction. Furthermore, the push plate 6B is urged toward the cover plate 6A by a urging means (not shown).

[0085] In the torque limiter device 5, the dry friction material 1 has an anti-slip portion 111 on a contact surface 1A that comes into contact with the plate 6, thereby increasing the friction coefficient (μ) of the contact surface 1A compared to a contact surface 1B that comes into contact with the friction target plate 121. The dry friction material 1 does not have an anti-slip portion 111 on the contact surface 1B, and the friction coefficient (μ) of the contact surface 1B is lower than the friction coefficient (μ) of the contact surface 1A. When torque is transmitted by the torque limiter device 5, the dry friction material 1 causes the plate 6 and the friction target plate 121 to cooperate with each other due to the frictional force generated on the contact surface 1B, and when torque is suppressed, the contact surface 1B slides against the friction target plate 121, causing the plate 6 and the friction target plate 121 to rotate relative to each other (slip).

[0086] The coefficient of friction (μ) of the contact surface 1A of the dry friction material 1 is increased by the provision of the anti-slip portion 111, and sliding relative to the mounting surface 61 (front surface) of the plate 6 is suppressed. During torque suppression, the dry friction material 1 allows the abutment surface 1B to slide relative to the friction plate 121, while preventing the contact surface 1A from sliding relative to the plate 6. This allows the dry friction material 1 to always remain fixed to the plate 6. From the above, by providing the anti-slip portion 111 on the contact surface 1A (back surface), the dry friction material 1 can have a different coefficient of friction (μ) from that of the abutment surface 1B (front surface). As a result, the torque limiter device 5 can exhibit appropriate torque transmission and torque suppression functions.

[0087] Furthermore, in the torque limiter device 5, the dry friction material 1 is segmented by attaching a plurality of dry friction materials 1 to the plate 6. Segmenting the dry friction material 1 in this manner improves yield (reducing material costs by reducing the friction area, increasing output by increasing the amount of heat treatment input, etc.) and also improves design flexibility (reducing size, weight, optimizing required values ​​(deflatness, burst, etc.)). In particular, segmenting the dry friction material 1 reduces the friction area and increases the surface pressure, ensuring a more stable friction coefficient (specifically, reducing the rate of decrease in the friction coefficient during thermally deteriorated sliding). Furthermore, the provision of the anti-slip portion 111 significantly increases the difference in the friction coefficient (μ) between the contact surface 1A and the abutment surface 1B, allowing the torque limiter device 5 to effectively perform its appropriate torque transmission and torque suppression functions.

[0088] The dry friction material 1 is formed in a button shape, and a fixed portion 2 is provided in the center of the contact surface 1A. This allows the dry friction material 1 to favorably receive the force applied from the plate 6 via the fixed portion 7, thereby suppressing damage. Furthermore, the fixing locations and number of the dry friction material 1 can be adjusted depending on the size of the plate 6, so that the same button-shaped dry friction material 1 can easily be used to accommodate plates 6 of different sizes. In particular, while ring-shaped dry friction materials had to be made to fit the size of the plate, the button-shaped dry friction material 1 can be manufactured in the same size regardless of the size of the plate, allowing for efficient manufacturing at low cost.

[0089] Furthermore, the fixing structure of the dry friction material 1 using the fixed shape portion 2 and the anti-slip portion 111 provided on the contact surface 1A fixes the dry friction material 1 to the plate 6 by an engaging relationship and frictional force, without bonding with an adhesive or the like. In other words, the dry friction material 1 can be fixed simply by attaching the dry friction material 1 to the plate 6 without requiring an adhesive application process or the like, thereby reducing costs.

[0090] 3( a) and 3(b), the dry friction material 1 is ring-shaped, and a plurality of fixed shape portions 2 are provided on the contact surface 1A (bottom surface). The inner diameter of the dry friction material 1 is approximately equal to the inner diameter of the plate 6, and the size of the dry friction material 1 is matched to the size of the plate 6. The reinforcing fibers 12 are made of short fibers and are oriented so as to describe a circle that is parallel to the outer circumferential edge and the inner circumferential edge of the dry friction material 1. The contact surface 1A, which is the bottom surface of the dry friction material 1, is formed into a line shape that describes a circle by irradiating two locations, one near the outer circumferential edge and the other near the inner circumferential edge, with laser light in a circular pattern.

[0091] The torque limiter device 5 used is the same as that in the first embodiment, and includes a plate 6 and a dry friction material 1 fixed onto the surface of the plate 6. That is, as shown in Figures 8(a) and 8(b), the plate 6 has a ring-shaped shape in a plan view, and a plurality of (six in the figure) fixed shape portions 7 are provided on the mounting surface 61.

[0092] In the dry friction material 1, the multiple fixed shape portions 2 are arranged so as to correspond to the multiple fixed shape portions 7 provided on the plate 6, respectively. One dry friction material 1 is attached to one plate 6. Specifically, each fixed shape portion 2 of the dry friction material 1 is fitted into each fixed shape portion 7 of the plate 6, thereby locking one dry friction material 1 to one plate 6.

[0093] In the torque limiter device 5, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A that comes into contact with the plate 6, which increases the friction coefficient (μ) of the contact surface 1A compared to the contact surface 1B that comes into contact with the friction target plate 121. In other words, the contact surface 1A and the contact surface 1B of the dry friction material 1 have different friction coefficients (μ). When torque is transmitted by the torque limiter device 5, the dry friction material 1 causes the plate 6 and the friction target plate 121 to cooperate with each other due to the frictional force generated on the contact surface 1B, and when torque is suppressed, the contact surface 1B slides against the friction target plate 121, causing the plate 6 and the friction target plate 121 to rotate relative to each other (slip).

[0094] The coefficient of friction (μ) of the contact surface 1A of the dry friction material 1 is increased by the inclusion of the anti-slip portion 111, and by preventing the contact surface 1A from slipping relative to the plate 6, the dry friction material 1 can always be kept fixed to the plate 6. In other words, by providing the anti-slip portion 111 on the contact surface 1A, the coefficients of friction (μ) of the contact surface 1A and the abutment surface 1B can easily be made different, thereby allowing the torque limiter device 5 to exhibit appropriate torque transmission and torque suppression functions. The dry friction material 1 is formed in a ring shape. In other words, the dry friction material 1 can be easily manufactured to have a shape equivalent to that of conventional products without using roving.

[0095] 4( a ) to 4 ( c ), the dry friction material 1 is fan-shaped, and has fixed portions 2 at both ends in the arc direction. The fixed portions 2 are notched. The notched fixed portions 2 are portions that are cut out in an arc shape from the end face of the dry friction material 1 in the arc direction. The reinforcing fibers 12 are made of short fibers and are oriented so as to describe an arc that is parallel to the outer and inner peripheral edges of the dry friction material 1. An anti-slip portion 111 is formed on the contact surface 1A, which forms the bottom surface of the dry friction material 1. The anti-slip portion 111 is formed in a linear arc shape at the middle part of the contact surface 1A in the radial direction (width direction) by irradiating a laser beam in an arc shape while avoiding the fixed portions 2.

[0096] The torque limiter device 5 used is the same as that in the first embodiment, and includes a plate 6 and a dry friction material 1 fixed onto the surface of the plate 6. That is, as shown in Figures 9(a) and 9(b), the plate 6 has a ring-shaped shape in a plan view, and a plurality of (six in the figure) fixed shape portions 7 are provided on the mounting surface 61.

[0097] Each dry friction material 1 is fixed to a plurality of (two in the figure) fixing portions 7 via a fixed portion 2. Specifically, the fixing portion 2 of the dry friction material 1 engages with the fixing portion 7 of the plate 6, so that one dry friction material 1 is fixed (sandwiched) between the fixing portions 7. A plurality of (three in the figure) dry friction materials 1 are attached to one plate 6 so as to be spaced at equal intervals in the circumferential direction of the plate 6.

[0098] In the torque limiter device 5, the dry friction material 1 has an anti-slip portion 111 on the contact surface 1A that comes into contact with the plate 6, which increases the friction coefficient (μ) of the contact surface 1A compared to the contact surface 1B that comes into contact with the friction target plate 121. In other words, the contact surface 1A and the contact surface 1B of the dry friction material 1 have different friction coefficients (μ). When torque is transmitted by the torque limiter device 5, the dry friction material 1 causes the plate 6 and the friction target plate 121 to cooperate with each other due to the frictional force generated on the contact surface 1B, and when torque is suppressed, the contact surface 1B slides against the friction target plate 121, causing the plate 6 and the friction target plate 121 to rotate relative to each other (slip).

[0099] The dry friction material 1 has an increased coefficient of friction (μ) on the contact surface 1A due to the presence of the anti-slip portion 111, and by preventing the contact surface 1A from slipping relative to the plate 6, the dry friction material 1 can always maintain a fixed state relative to the plate 6. In other words, by providing the anti-slip portion 111 on the contact surface 1A, the dry friction material 1 can easily make the coefficients of friction (μ) of the contact surface 1A and the abutment surface 1B different, and as a result, the torque limiter device 5 can exhibit an appropriate torque transmission function and torque suppression function.

[0100] A plurality of dry friction materials 1 (six in contrast to three in the figure) can be attached to one plate 6 so as to be adjacent to each other in the circumferential direction of the plate 6. In this case, the plurality of fan-shaped dry friction materials 1 form a ring shape as a whole. That is, the fan-shaped dry friction materials 1 can be treated as segments obtained by dividing the ring-shaped dry friction material 1 into a plurality of pieces. Compared to ring-shaped dry friction materials, the segmented dry friction materials 1 can improve yield (reduced material costs by reducing the friction area, increased production volume by increasing the amount of heat treatment input, etc.) and can also improve design freedom (reduced size, reduced weight, optimization of required values ​​(off-flatness, burst, etc.)).

[0101] 1; dry friction material, 1A; contact surface, 1B; abutment surface, 2; fixed shape portion, 11; vulcanized rubber, 12; reinforcing fiber, 111; anti-slip portion, 5; torque limiter device, 6; plate, 6A; cover plate, 6B; push plate, 61; mounting surface, 7; fixed shape portion, 14; engagement hole, 13; engagement protrusion, 121; friction plate.

Claims

1. A dry friction material attached to the surface of a plate in a torque limiter device, It contains reinforcing fibers and vulcanized rubber, A dry friction material characterized in that the contact surface of the plate that comes into contact with the surface of the plate has an anti-slip portion containing carbide.

2. The dry friction material according to claim 1, wherein the carbide is derived from the vulcanized rubber.

3. The dry friction material according to claim 1 or 2, wherein the contact surface is flat.

4. The dry friction material according to claim 1 or 2, wherein the reinforcing fibers consist of short fibers and are oriented in a certain direction.

5. The dry friction material has a ring-shaped flat plate form. The dry friction material according to claim 4, wherein the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

6. The dry friction material has a fan-shaped flat plate form. The dry friction material according to claim 4, wherein the orientation of the reinforcing fibers is parallel to the outer edge of the arc-shaped dry friction material.

7. The dry friction material has a button-shaped flat plate form. The dry friction material according to claim 4, wherein the orientation of the reinforcing fibers is parallel to the outer edge of the circular dry friction material.

8. A torque limiter device comprising a dry friction material according to claim 1 or 2, and a plate to which the dry friction material is attached, The plate has a plurality of fixed-shaped portions on the mounting surface to which the dry friction material is attached. The torque limiter device is characterized in that the dry friction material has a fixed-shape portion that engages with the fixed-shape portion.

9. The torque limiter device according to claim 8, wherein the dry friction material includes short fibers oriented in a certain direction as the reinforcing fibers.

10. The mounting surface of the plate has a ring shape when viewed from above. The dry friction material has a ring-shaped flat plate form. The dry friction material has the same number of fixed-shaped portions as the fixed-shaped portions, The torque limiter device according to claim 8, wherein one dry friction material is fixed concentrically to one of the mounting surfaces of the plate.

11. The mounting surface of the plate has a ring shape when viewed from above. The dry friction material has a fan-shaped flat plate form. The dry friction material has the fixed-shape portion at both ends, The torque limiter device according to claim 8, wherein one dry friction material is locked to a plurality of fixed shapes via the fixed shapes, and a plurality of dry friction materials are locked to one of the mounting surfaces of the plate.

12. The mounting surface of the plate has a ring shape when viewed from above. The dry friction material has a button-shaped flat plate form. The dry friction material has the fixed-shape portion in its center, The torque limiter device according to claim 8, wherein one dry friction material is fixed to one fixed shape portion via the fixed shape portion, and a plurality of dry friction materials are fixed to one mounting surface of the plate.

13. The aforementioned plates are a cover plate and a push plate, The cover plate and the push plate are arranged with their mounting surfaces, on which the dry friction material is attached, facing each other. The torque limiter device according to claim 8, wherein a friction plate is disposed between the cover plate and the push plate in a state in contact with the dry friction material.

14. A method for manufacturing a dry friction material according to claim 1 or 2, A method for manufacturing a dry friction material, characterized by comprising the step of applying a partial heat treatment to the contact surface of the dry friction material, thereby carbonizing the vulcanized rubber on the surface layer of the contact surface to form the anti-slip portion.

15. The method for manufacturing a dry friction material according to claim 14, wherein the partial heating treatment is laser treatment.

16. A step of obtaining a friction material composition by extruding a mixture of the unvulcanized rubber that becomes the vulcanized rubber and the reinforcing fibers, A method for producing a dry friction material according to claim 14, comprising the steps of filling the cavity of a mold with the friction material composition and vulcanizing it to obtain the dry friction material having a skin layer formed on the surface that contacts the wall of the cavity.