JP2020051438A - Friction member, friction material composition, friction material and vehicle - Google Patents

Abstract

To provide a friction material composition that can improve stability of a friction coefficient at normal load braking, and to provide a friction member and a friction material that use the friction material composition, and to provide a vehicle that is mounted with the friction member and the friction material.SOLUTION: A friction member includes a friction material and a back metal, where the friction material does not include copper or may include less than 0.5 mass% as a copper element, and includes a bismuth oxide and an inorganic filler for forming a coating.SELECTED DRAWING: None

Description

  The present invention relates to a friction member, a friction material composition, a friction material, and a vehicle.

Generally, brakes mounted on automobiles and the like are mainly divided into two main types, namely disc brakes and drum brakes. The disk brake is a device in which a disk rotor that rotates integrally with wheels during traveling is sandwiched between brake pads, and a braking force is generated by frictional force generated at that time. Drum brakes are, for example, those in which a brake lining (also called a brake shoe) is mounted inside a drum installed inside wheels, and exerts a braking force by pressing it from inside to outside. It is.
A friction material is provided on a brake pad of a disc brake (hereinafter, referred to as a disc brake pad) and a brake lining of a drum brake (hereinafter, referred to as a drum brake lining). It brakes by rubbing with the facing material and converting kinetic energy of a car or the like into heat energy. Therefore, the friction material is required to have a good friction coefficient, abrasion resistance (the life of the friction material is long), strength, vibration damping property (there is no occurrence of brake squeal), and the like.

  At present, as a friction material, a friction material containing no or almost no steel fiber, that is, a non-asbestos friction material (hereinafter sometimes abbreviated as NAO material) is mainly used, and the NAO material includes: Copper (including copper alloys) and the like have been used. However, since friction materials containing copper contain a large amount of copper in wear powder generated by braking, it has been suggested that such friction materials cause pollution of rivers, lakes, oceans, and the like. Therefore, in some parts of North America, laws have been enacted that prohibit the sale of friction materials containing 5% by mass or more of copper after 2021 and 0.5% by mass or more of copper after 2023 and the assembling to new vehicles. . Therefore, in order to make the friction material usable in the United States and other foreign countries, there is a need to contain no copper or to greatly reduce the content of copper.

  Under such circumstances, friction materials that do not contain copper or have a low copper content have been proposed (for example, see Patent Documents 1 and 2). The invention described in Patent Document 1 is a friction material composition containing a binder, an organic filler, an inorganic filler, and a fiber base material, and does not contain copper as an element or has a copper content of 0.1%. Not more than 5% by mass, containing potassium titanate, and further containing at least one of lithium potassium titanate and magnesium potassium titanate, wherein the potassium titanate, the lithium potassium titanate, and the magnesium potassium titanate The friction material composition has a total of at least one of 10 to 35% by mass and a mass reduction ratio of 5 to 20% when heated at 500 ° C in an air atmosphere. The invention described in Patent Literature 1 provides a transfer film (a film in which a friction material composition is transferred to the surface of a disk rotor) which is stable while lightly braking while having a composition having low environmental harm and human harm. An object of the present invention is to provide a friction material composition that forms and provides a friction material that exhibits a stable friction coefficient.

  The invention described in Patent Document 2 is a friction material composition including a binder, an organic filler, an inorganic filler, and a fiber base material, wherein the friction material composition does not include copper as an element. Or, the content of copper is 0.5% by mass or less, and one or more metal sulfides selected from tin sulfide, bismuth sulfide, and molybdenum disulfide are contained in an amount of 8 to 30% by mass. It is a friction material composition. The invention described in Patent Literature 2 discloses a friction material that does not contain copper, which deteriorates high-speed fade characteristics, or that can maintain a sufficient friction coefficient under high-speed fade conditions in a friction material having a copper content of 0.5% by mass or less. The object of the present invention is to provide a material composition.

JP-A-2017-002186 JP-A-2006-079250

However, in the invention described in Patent Document 1, a stable transfer film is formed during "light load braking" (for example, when the vehicle is traveling at a speed of about 20 to 50 km / h and the disk rotor temperature is low (50 [deg.] C.)). Develops a stable coefficient of friction. However, when the vehicle normally decelerates from the normal traveling speed in an urban area (for example, when traveling at a speed of approximately 40 to 70 km / h and decelerating at a speed of ² to 4 m / s2, hereinafter, referred to as "at the time of normal load braking". However, the stability of the coefficient of friction of the disk rotor at the start of deceleration is about 80 to 140 ° C.).
The invention described in Patent Literature 2 can maintain a sufficient friction coefficient under a high-speed fading condition (a condition in which the initial speed is 200 km / h and the deceleration is 0.8 G (about 8 m / s ² ) to 80 km / h). Although it is a friction material composition, stability of the friction coefficient during normal load braking is not considered as a problem, and a solution to the problem is unknown.

  In a conventional friction material containing copper, a copper spread film is formed at a friction interface by braking, and the spread film has an effect of preventing the friction material from being excessively worn when repeatedly braking. However, in the case of a friction material containing no copper or having a small copper content, the effect of copper is not substantially obtained. A method for increasing the stability of the coefficient of friction at the time is eagerly desired.

  Therefore, an object of the present invention is to provide a friction material composition that can improve the stability of the friction coefficient during normal load braking, to provide a friction member and a friction material using the friction material composition, and An object of the present invention is to provide a vehicle equipped with the friction member or the friction material.

  The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, a friction material composition containing no copper or containing less than 0.5% by mass of copper as a copper element even if copper is contained. Even so, it has been found that the use of the friction material composition containing bismuth oxide and the inorganic filler for film formation improves the stability of the friction coefficient during normal load braking, leading to the completion of the present invention. Was. The present invention has been completed based on such findings.

The present invention relates to the following [1] to [19].
[1] A friction member having a friction material and a back metal,
The friction material does not contain copper, or even if it contains copper, the content of copper is less than 0.5% by mass as a copper element, and contains bismuth oxide and a film-forming inorganic filler. Element.
[2] The friction member according to [1], wherein the melting point of the inorganic filler for forming a film is 800 to 1,200 ° C.
[3] The friction material further includes at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the bismuth oxide and the inorganic filler for forming a film), a fiber base material, and a binder. The friction member according to the above [1] or [2], comprising:
[4] The inorganic filler is graphite, calcium hydroxide, calcium oxide, magnesium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, coke, mica, vermiculite, zeolite, zirconium silicate (zircon), zirconia, The friction member according to the above [3], containing at least one selected from the group consisting of silica, triiron tetroxide, alumina and silicon carbide.
[5] The friction member according to any one of [1] to [4], wherein the content of the bismuth oxide in the friction material is 0.1 to 20% by mass.
[6] The above-mentioned [1] to [5], wherein the inorganic filler for film formation contains at least one selected from the group consisting of metal sulfides, titanates, and metals (excluding copper). ] The friction member according to any one of the above.
[7] The friction member according to any one of [1] to [6], wherein the content of the film-forming inorganic filler in the friction material is 5 to 55% by mass.
[8] The friction member according to any one of [1] to [7], which is for a disc brake pad or a drum brake lining.
[9] A vehicle equipped with the friction member according to any one of [1] to [8].
[10] A friction material composition containing no copper or containing less than 0.5% by mass of copper as a copper element, and containing bismuth oxide and an inorganic filler for film formation. A friction material composition to be contained.
[11] The friction material composition according to the above [10], wherein the melting point of the inorganic filler for forming a film is 800 to 1,200 ° C.
[12] The composition further comprising at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the bismuth oxide and the inorganic filler for forming a film), a fiber base material, and a binder. The friction material composition according to [10] or [11].
[13] The inorganic filler may be mica, graphite, coke, calcium hydroxide, calcium oxide, magnesium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, coke, mica, vermiculite, zeolite, zirconium silicate (zirconium ), Zirconia, silica, triiron tetroxide, alumina, and silicon carbide.
[14] The friction material composition according to any of [10] to [13], wherein the content of the bismuth oxide is 0.1 to 20% by mass.
[15] The above-mentioned [10] to [14], wherein the film-forming inorganic filler contains at least one selected from the group consisting of metal sulfides, titanates, and metals (excluding copper). ] The friction material composition according to any one of [1] to [10].
[16] The friction material composition according to any one of [10] to [15], wherein the content of the inorganic filler for forming a film is 5 to 55% by mass.
[17] The friction material composition according to any one of the above [10] to [16], which is used for a disc brake pad or a drum brake lining.
[18] A friction material comprising the friction material composition according to any one of [10] to [17].
[19] A vehicle equipped with the friction material according to the above [18].

According to the present invention, using a material having a low environmental load, a friction material composition that improves the stability of the friction coefficient during normal load braking, and a friction during normal load braking using the friction material composition A friction member and a friction material having excellent coefficient stability can be provided. Further, a vehicle equipped with the friction member or the friction material can be provided.
Further, when the friction material of the present invention is used as a friction material such as a disc brake pad or a drum brake lining, the environmental load is small.

FIG. 3 is a schematic view illustrating one embodiment of the friction member of the present invention.

Hereinafter, the present invention will be described in detail. However, in the following embodiments, the components are not essential unless otherwise specified. The same applies to numerical values and their ranges, and does not limit the present invention.
In the numerical ranges described in this specification, the upper limit or the lower limit of the numerical range may be replaced with the value shown in the embodiment. Further, the lower limit and the upper limit of the numerical range are arbitrarily combined with the lower limit and the upper limit of the other numerical ranges, respectively. Further, in the present specification, the content of each component in the friction material composition, when there are a plurality of types of substances corresponding to each component, unless otherwise specified, the plurality of components present in the friction material composition It means the total content of the species.
An embodiment in which the items described in this specification are arbitrarily combined is also included in the present invention.
Furthermore, in the present invention, “substantially 0% by mass” and “substantially do not include” mean that the content is 0% by mass and that the content is essentially insignificant. (For example, 0.5% by mass or less, 0.2% by mass or less, 0.1% by mass or less).

[Friction member]
A friction member according to one embodiment of the present invention is a friction member having a friction material and a backing metal, and the friction material does not contain copper, or even if it contains copper, the content of copper is 0.1 as a copper element. It is a friction member containing less than 5% by mass and containing bismuth oxide and a film-forming inorganic filler.
In the present invention, the “film-forming inorganic filler” refers to an inorganic filler that forms a film by transferring to a friction portion of a friction object when a brake is applied using a friction material. The film is generally called a transfer film. The inorganic filler for forming a film may form a film on a friction portion of a friction object while involving other components in the friction material composition.
Hereinafter, the material (friction material composition) used for the friction material will be described in detail. In addition, each component and its content in a friction material composition are the same as each component and its content in a friction material.

[Friction material composition]
The friction material composition according to one embodiment of the present invention does not contain copper, or has a copper content of less than 0.5% by mass as a copper element even if copper is contained, and A friction material composition containing bismuth oxide and an inorganic filler for film formation.
In a preferred embodiment of the friction material composition, an organic filler, an inorganic filler (excluding the bismuth oxide and the inorganic filler for film formation), a fiber base material, together with the bismuth oxide and the inorganic filler for film formation, And a friction material composition containing at least one member selected from the group consisting of a binder and a binder. A more preferred embodiment further includes an organic filler, an inorganic filler (excluding the bismuth oxide and the inorganic filler for film formation), a fiber base material, and a binder together with the bismuth oxide and the inorganic filler for film formation. Is a friction material composition.

  It is preferable that the friction material composition does not contain copper. When copper is contained, the content of copper in the friction material composition is set to less than 0.5% by mass as a copper element, so that the friction material composition can be used as wear powder in the environment. Even if released, it is possible to cause no pollution of rivers and the like. The copper content indicates the content of copper element (Cu) contained in fibrous and powdery copper, copper alloy and copper compound in the entire friction material composition. The content of copper in the friction material composition is more preferably 0.2% by mass or less as a copper element, and further preferably 0.05% by mass or less.

  Further, from the viewpoint of avoiding a decrease in durability due to rusting, it is preferable that the friction material composition of the present invention does not contain an iron-based metal. By setting the content of the iron-based metal to less than 0.5% by mass as iron element, rust resistance can be improved. The content of the iron-based metal in the friction material composition is more preferably 0.2% by mass or less as an iron element, and further preferably 0.05% by mass or less. Here, the iron-based metal is a metal containing iron as a main component and refers to general iron and steel. The iron content is defined as iron, iron alloy, and iron element (Fe) contained in iron compounds. The content in the entire friction material composition is shown.

  The friction material composition of the present invention is classified as a NAO (Non-Asbestos-Organic) material, and is a so-called non-asbestos friction material composition (a friction material composition containing no asbestos or containing asbestos). Even if it is, the asbestos content is a very small amount of the friction material composition). In the friction material composition, the content of asbestos is 0.2% by mass or less, and is substantially 0% by mass.

As described above, the friction material composition of the present invention contains bismuth oxide and a film-forming inorganic filler from the viewpoint of improving the stability of the friction coefficient during normal load braking.
(Bismuth oxide)
The bismuth oxide, bismuth trioxide _{(Bi 2 O} 3), include pentoxide bismuth _(Bi 2 _{O 5),} bismuth trioxide are preferred. The crystal structure of bismuth oxide is not particularly limited, and examples thereof include a monoclinic crystal, a tetragonal crystal, and a cubic crystal structure.
The average particle diameter of the bismuth oxide is not particularly limited, but from the viewpoint that moderately bismuth oxide particles are present on the friction surface and a stable friction coefficient is obtained at the time of repeated braking, preferably 50 μm or less. is there. From the same viewpoint, the average particle size of magnesium oxide is preferably 20 μm or less, more preferably 10 μm or less, further preferably 5 μm or less, and particularly preferably 2 μm or less. Further, the average particle diameter of bismuth oxide is preferably from 0.1 to 5 μm, more preferably from 0.5 to 2 μm, and still more preferably from 0.7 to 1 from the viewpoint of stabilizing the coefficient of friction during normal braking. A range of 0.5 μm can be selected.
The upper limit of the maximum primary particle diameter of bismuth oxide is not particularly limited, but is usually preferably 30 μm or less.
In the present specification, the average particle diameter means a value of d50 (median diameter of volume distribution, cumulative median value) measured using a laser diffraction particle size distribution measuring method.

The content of bismuth oxide in the friction material composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 16% by mass, and still more preferably, from the viewpoint of stability of the friction coefficient during normal load braking. It is 0.5 to 12% by mass. The content of bismuth oxide in the friction material composition may be 0.1 to 7% by mass or 0.1 to 3% by mass in consideration of wear resistance. In addition, from the viewpoint of increasing the average value of the friction coefficient during normal load braking, it may be set to 3 to 20% by mass, 3 to 16% by mass, 3 to 12% by mass, or 7 to 12% by mass. % By mass.
In particular, bismuth oxide is a very useful component in that even a small content, for example, about 1% by mass, greatly improves the stability of the friction coefficient during normal load braking.

(Inorganic filler for film formation)
The inorganic filler for forming a film is not particularly limited as long as it is an inorganic filler that transfers to a friction portion of a friction object to form a film when a brake is applied using a friction material. From the viewpoint of the function of forming a film by transferring to a frictional part of an object, its melting point is preferably 800 to 1,200 ° C, more preferably 900 to 1,100 ° C, and still more preferably 1,000 to 1,100 ° C. , 100 ° C.
When the friction material composition contains both the bismuth oxide and the inorganic filler for forming a film, copper is not contained, or even if copper is contained, the content of copper is less than 0.5% by mass as a copper element. Even with this, it is possible to obtain a friction material excellent in stability of the friction coefficient during normal load braking.

Examples of the inorganic filler for forming a film include metal sulfides, titanates, and metals (excluding copper), and the like. At least one selected from the group consisting of these is used. It is preferably contained as a material.
−metal sulfide−
Examples of the metal sulfide include bismuth sulfide, antimony sulfide, tin sulfide, molybdenum disulfide, iron sulfide, zinc sulfide, tungsten sulfide, and manganese sulfide, and are at least one selected from the group consisting of these. Is preferred. Among them, from the viewpoint of being less harmful to the human body, containing at least one selected from the group consisting of bismuth sulfide, tin sulfide, molybdenum disulfide, iron sulfide, zinc sulfide, tungsten sulfide and manganese sulfide It is more preferable that tin sulfide be contained from the viewpoint of the stability of the friction coefficient during normal load braking.
When the friction material composition contains a metal sulfide as the inorganic filler for film formation, the content of the metal sulfide is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, More preferably, it is 1 to 15% by mass, particularly preferably 1 to 10% by mass, and most preferably 3 to 8% by mass.

-Titanate-
Examples of the titanate include potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate, and are preferably at least one selected from the group consisting of these. Among them, potassium titanate is preferred from the viewpoint of stability of the friction coefficient during normal load braking.

The shape of the titanate is not particularly limited, and examples thereof include a fibrous shape, a columnar shape, a plate shape, a particle shape, and a flake shape. The shape of the titanate can be analyzed by, for example, observation with a scanning electron microscope (SEM).
The titanate is not particularly limited. For example, a titanate having an average particle diameter of 1 to 50 μm and a specific surface area of 0.5 to 10 m ² / g can be used. The specific surface area can be determined by a BET method using nitrogen gas as an adsorption gas.

When the friction material composition contains a titanate as an inorganic filler for forming a film, the content of the titanate is preferably 5 to 45% by mass, more preferably 5 to 35% by mass, and still more preferably 5 to 35% by mass. -30 mass%, particularly preferably 10-25 mass%.
When the content of the titanate is 5% by mass or more, the stability of the friction coefficient during normal load braking is improved, and the wear resistance tends to be improved. Further, when the content of the titanate is 45% by mass or less, a decrease in mechanical strength and a decrease in wear resistance of the friction material are suppressed, and a decrease in stability of the friction coefficient due to moisture absorption is suppressed, Furthermore, there is a tendency that fixation due to rust between the friction material and the friction object is suppressed, and a phenomenon (metal catch) in which a component such as a disk rotor serving as the friction object adheres to the friction material itself.

−metal−
Examples of the metal (excluding copper) include iron, cast iron, aluminum, nickel, tin, and zinc. Also, alloys containing at least one of the above metals can be used. The metal preferably does not contain copper, and more preferably does not contain copper and iron-based metals. As the metal, tin and zinc are preferable, and zinc is more preferable.
The shape of the metal as the inorganic filler for forming a film is not particularly limited, and may be a powder or a fiber.
When the friction material composition contains a metal as an inorganic filler for forming a film, the content is preferably 0.5 to 10% by mass, more preferably 0.5 to 8% by mass, and still more preferably 1 to 6% by mass. % By mass. In particular, when zinc (zinc powder) is used as the metal, zinc is more easily oxidized than iron. By setting zinc within the above range, generation of rust can be suppressed without affecting the friction characteristics.

  The content of the inorganic filler for film formation in the friction material composition (however, when a plurality of inorganic fillers for film formation are contained, the total content thereof) is usually the stability of the friction coefficient during load braking. From the viewpoint, the amount is preferably 5 to 55% by mass, more preferably 5 to 45% by mass, further preferably 8 to 40% by mass, particularly preferably 10 to 40% by mass, and most preferably 15 to 40% by mass. When the content of the inorganic filler for film formation in the friction material composition is 5% by mass or more, the stability of the friction coefficient during normal load braking tends to be sufficiently improved, and is 55% by mass or less. , There is a tendency that a decrease in wear resistance can be suppressed.

  As described above, in a conventional friction material containing copper, a copper spreading film is formed at a friction interface by braking, and the spreading film has an effect of preventing the friction material from being excessively worn when repeatedly braking. However, a friction material that does not contain copper or has a low copper content does not substantially achieve the effect of copper. Therefore, it is not always easy to improve the stability of the friction coefficient during normal load braking in a friction material that does not contain copper or has a low copper content, but it is not easy to use bismuth oxide and inorganic filler for film formation. With the friction material composition of the present invention containing a material, this can be achieved even with a friction material that does not contain copper or has a low copper content.

Hereinafter, each component which may be further contained in the friction material composition will be described in order.
(Organic filler)
The organic filler can exhibit a function as a friction modifier for improving the vibration damping property and the wear resistance. Here, in the present invention, the organic filler does not include a fibrous material (for example, an organic fiber described later). One kind of the organic filler may be used alone, or two or more kinds may be used in combination.
As the organic filler, an organic filler generally used in a friction material composition can be used. Examples of the organic filler include cashew particles, rubber, melamine particles, and the like, and it is preferable that at least one selected from the group consisting of these. Among these, cashew particles and rubber are preferable from the viewpoint of improving the stability of the coefficient of friction and the abrasion resistance and suppressing the squeal.
Further, as the organic filler, cashew particles and rubber may be used in combination, or cashew particles coated with rubber may be used.

The cashew particles are obtained by pulverizing hardened cashew nut shell oil and may be generally referred to as cashew dust.
Cashew particles are generally classified into brown, brown-black, black, and the like, depending on the type of curing agent used in the curing reaction. By adjusting the molecular weight and the like of the cashew particles, it is possible to easily control the heat resistance, the sound and vibration properties, and the film forming property on the disk rotor, which is a friction object, and the like.
The average particle size of the cashew particles is not particularly limited, but is preferably 850 μm or less, more preferably 750 μm or less, and even more preferably 600 μm or less from the viewpoint of dispersibility. The lower limit of the average particle size of the cashew particles is not particularly limited, and may be 200 μm or more, 300 μm or more, or 400 μm or more.
As cashew particles, commercially available products can be used.
One type of cashew particles may be used alone, or two or more types may be used in combination.

  When the friction material composition contains an organic filler, the content is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and still more preferably 4 to 10% by mass. By setting the total content of the organic filler in the above range, the elastic modulus of the friction material tends to be high, and it is possible to avoid deterioration in vibration damping properties such as squeal and wear resistance, and In addition, there is a tendency that deterioration in heat resistance and reduction in strength due to heat history can be avoided.

Examples of the rubber include a rubber generally used in a friction material composition, for example, a natural rubber and a synthetic rubber. Examples of the synthetic rubber include acrylonitrile-butadiene rubber (NBR), acrylic rubber, isoprene rubber, polybutadiene rubber (BR), styrene butadiene rubber (SBR), pulverized powder of silicone rubber and tire tread rubber, and the like. One type of rubber may be used alone, or two or more types may be used in combination. Among these, acrylonitrile-butadiene rubber (NBR) and pulverized powder of tire tread rubber are preferred from the viewpoint of the balance between heat resistance, flexibility and production cost.
When the friction material composition contains rubber, the content is preferably 1 to 30% by mass, more preferably 2 to 15% by mass, and still more preferably 2 to 8% by mass. . By setting the content of the rubber in the above range, the elastic modulus of the friction material tends to be high, and the vibration damping properties such as squeal tend to be prevented from deteriorating. There is a tendency that a decrease in strength due to heat history can be avoided.

(Inorganic filler)
The friction material composition may contain an inorganic filler. However, in order to avoid duplication, the inorganic filler does not include the bismuth oxide and the inorganic filler for forming a film.
The inorganic filler can exhibit a function as a friction adjusting material for avoiding deterioration of heat resistance, abrasion resistance and stability of friction coefficient of the friction material. Here, in the present invention, the inorganic filler does not include a fibrous material (for example, an inorganic fiber described later). As the inorganic filler, one type may be used alone, or two or more types may be used in combination.
The inorganic filler is not particularly limited, and an inorganic filler usually used for a friction material can be used. Examples of the inorganic filler include graphite, calcium hydroxide, calcium oxide, magnesium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, zinc oxide, barium sulfate, coke, mica, vermiculite, zeolite, zirconium silicate (zircon), Zirconia, silica, triiron tetroxide, alumina (α-alumina, γ-alumina), silicon carbide and the like can be mentioned. Among these, at least one selected from the group consisting of graphite, alumina, zirconium silicate (zircon), calcium hydroxide, magnesium oxide and barium sulfate is preferable, and graphite, alumina, zirconium silicate (zircon), and hydroxide are preferred. It is more preferable to use calcium, magnesium oxide and barium sulfate together.

  In addition, among the inorganic fillers, calcium hydroxide, calcium oxide, sodium carbonate, and zinc oxide are preferable from the viewpoint of suppressing rust generation of the friction material. However, calcium hydroxide, calcium oxide, and sodium carbonate increase the pH of the friction material, and the aramid fiber and the phenol resin tend to be easily decomposed. Therefore, the pH increases when used with the aramid fiber or the phenol resin. It is preferable to pay attention to the amount used so as not to be too small. For example, when calcium hydroxide is contained as an inorganic filler, the content of calcium hydroxide is preferably 0.1 to 100 parts by mass of the friction material composition. It is 5 to 10% by mass, more preferably 1 to 8% by mass, and still more preferably 1 to 5% by mass.

The graphite is not particularly limited, and any known graphite, that is, any of natural graphite and artificial graphite can be used. The graphite preferably has an average particle diameter of 1 to 50 μm, more preferably 2 to 40 μm, further preferably 5 to 30 μm, and particularly preferably 10 to 20 μm.
When the friction material composition contains graphite, its content is preferably 2 to 20% by mass, more preferably 3 to 15% by mass, still more preferably 3 to 10% by mass, and particularly preferably 3 to 8% by mass. It is. When the content is 2% by mass or more, the thermal conductivity of the friction material is easily improved, and when the content is 20% by mass or less, a decrease in the cohesive force of the friction material composition can be suppressed, and a decrease in the friction coefficient tends to be easily suppressed. is there.

When the friction material composition contains alumina, the content is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and still more preferably 0.5 to 3% by mass. Within the above range, there is a tendency that appropriate grinding properties are easily imparted without excessively wearing the friction object.
When the friction material composition contains zirconium silicate (zircon), the content is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, and still more preferably 3 to 8% by mass. Within the above range, there is a tendency that appropriate grinding properties are easily imparted without excessively wearing the friction object.
When the friction material composition contains magnesium oxide, the content is preferably 1 to 35% by mass, more preferably 5 to 30% by mass, and still more preferably 10 to 30% by mass. Within the above range, there is a tendency that appropriate grinding properties are easily imparted without excessively wearing the friction object.
Barium sulfate plays a role as a simple filler for adjusting the volume of the friction material composition. That is, the content of barium sulfate depends on the content of other components, and the remainder for adjusting the friction material composition to a predetermined amount can be supplemented with barium sulfate. By containing barium sulfate, the bulk density of the friction material composition is increased, and the handling properties are improved.

  The friction material composition of the present invention may or may not contain zirconium oxide. Even when zirconium oxide is contained, its content can be set to 10% by mass or less, 5% by mass or less, 1% by mass or less, and 0.1% by mass or less. It can be 5% by mass or less.

  As described above, when the friction material composition contains the inorganic filler, the total content of the inorganic filler, the bismuth oxide, and the film-forming inorganic filler is preferably 40 to 85% by mass, More preferably, it is adjusted to be 50 to 85% by mass, and still more preferably 60 to 85% by mass. When the total content of the inorganic filler, the bismuth oxide, and the film-forming inorganic filler is in the above range, deterioration of heat resistance tends to be easily avoided.

(Fiber base material: organic fiber and inorganic fiber)
The fiber base material has a reinforcing effect on the friction material. The friction material composition preferably contains an organic fiber as a fiber base material, and also preferably contains an inorganic fiber. One type of fiber base material may be used alone, or two or more types may be used in combination. Here, the organic fiber is a fibrous material containing an organic substance as a main component. Further, the inorganic fiber is a fibrous material mainly composed of an inorganic substance other than a metal and a metal alloy.

-Organic fiber-
Examples of the organic fiber include hemp, cotton, aramid fiber, cellulose fiber, acrylic fiber, and phenol resin fiber (having a crosslinked structure). One type of organic fiber may be used alone, or two or more types may be used in combination. As the organic fiber, an aramid fiber is preferable from the viewpoint of heat resistance. From the viewpoint of improving the strength of the friction material, it is preferable that the organic fibers contain fibrillated organic fibers, and it is more preferable that the organic fibers contain fibrillated aramid fibers. The fibrillated organic fiber is an organic fiber that has been split and has fluff, and fibrillated aramid fiber, fibrillated acrylic fiber, fibrillated cellulose fiber, and the like are commercially available. Needless to say, the friction material composition may contain other organic fibers together with the fibrillated organic fibers.
When the friction material composition contains an organic fiber, particularly a fibrillated organic fiber, the content is preferably 1 to 8% by mass, more preferably 2 to 7% by mass, and still more preferably 1 to 5% by mass. . When the content is 1% by mass or more, good shear strength, crack resistance and abrasion resistance tend to be developed, and when the content is 8% by mass or less, the organic fibers (fibrillated organic fibers) in the friction material composition and There is a tendency that deterioration of shear strength and crack resistance due to uneven distribution of other materials can be effectively suppressed.

-Inorganic fiber-
Inorganic fibers can exhibit the effect of improving the mechanical strength and wear resistance of the friction material.
Examples of the inorganic fiber include glass fiber, metal fiber, mineral fiber, carbon fiber, ceramic fiber, biodegradable ceramic fiber, sepiolite (α-type sepiolite and β-type sepiolite), attapulgite, potassium titanate fiber, silica alumina fiber, At least one selected from the group consisting of flame-resistant fibers and the like can be used. Among these, mineral fibers are preferred.

  The glass fiber refers to a fiber produced by melting and spinning glass. As the glass fiber, a glass fiber whose raw material is E glass, C glass, S glass, D glass, or the like can be used. Among them, a glass containing E glass or S glass from the viewpoint of particularly high strength. Preferably, fibers are used. Further, glass fibers obtained by treating the surfaces of glass fibers with aminosilane, epoxysilane, or the like are preferable for improving the affinity with the binder.

Examples of the metal fibers include fibers in the form of a single metal or alloy such as aluminum, iron, zinc, tin, titanium, nickel, and magnesium, and fibers mainly containing a metal such as cast iron. Examples of the alloy-type fiber (alloy fiber) include an iron alloy fiber and an aluminum alloy fiber. One type of metal fiber may be used alone, or two or more types may be used in combination. In the present invention, a friction material composition containing substantially no metal fibers may be used.
From the viewpoint of improving crack resistance and wear resistance, copper fibers, copper alloy fibers, iron fibers, and iron alloy fibers are generally preferred.
However, when copper or a copper alloy fiber is contained, the content of copper in the friction material composition is preferably less than 0.5% by mass as a copper element, and more preferably 0.3% by mass, for the reasons described above. In the following, the embodiment is more preferably 0.1% by mass or less, particularly preferably substantially free of copper. In addition, as a copper alloy fiber, a copper fiber, a brass fiber, a bronze fiber, etc. are mentioned.
Further, in the case where iron fibers or iron alloy fibers are contained, the content of iron in the friction material composition may be less than 0.5% by mass as an iron element from the viewpoint of suppressing a decrease in durability due to rusting. It is an embodiment that is preferably, more preferably 0.3% by mass or less, further preferably 0.1% by mass or less, and particularly preferably substantially free of iron.

Examples of the mineral fibers include natural mineral fibers; blast furnace slag such as slag wool, basalt such as basalt fiber, and artificial mineral fibers melt-spun with other natural rocks as main components. One type of mineral fiber may be used alone, or two or more types may be used in combination.
Examples of the artificial mineral fibers include artificial mineral fibers containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO, and Na ₂ O, or artificial mineral fibers containing one or more of these compounds. No. As the artificial mineral fiber, an artificial mineral fiber containing an aluminum element is preferable, an artificial mineral fiber containing Al ₂ O ₃ is more preferable, and an artificial mineral fiber containing Al ₂ O ₃ and SiO ₂ is further preferable.

The mineral fibers are preferably biosoluble from the viewpoint of harmful effects on the human body. The term "biosoluble mineral fiber" as used herein refers to a mineral fiber that has the characteristic of being partially decomposed in a short time and discharged out of the body even when taken into the human body. Specifically, the chemical composition is such that the total amount of alkali oxides and alkaline earth oxides (total amount of sodium, potassium, calcium, magnesium and barium oxides) is 18% by mass or more, and (a) short-term inhalation The half-life of a fiber having a length of more than 20 μm is less than 10 days in an in vivo durability test by exposure, and (b) a half-life of a fiber having a length of more than 20 μm in an in vivo durability test by short-term intratracheal injection. Less than 40 days, (c) no significant carcinogenicity in the intraperitoneal administration test, or (d) no pathological findings or tumor formation associated with carcinogenicity in the long-term inhalation exposure test. Fibers satisfying either (see EU Directive 97/69 / EC, Nota Q (exclusion of carcinogenicity)). Examples of such biodegradable mineral fibers include SiO ₂ —Al ₂ O ₃ —CaO—MgO—FeO (—K ₂ O—Na ₂ O) fibers and the like, and include SiO ₂ , Al ₂ O ₃ , and CaO. , MgO, FeO, K ₂ O, Na ₂ O and the like. Commercial products include Roxul series manufactured by LAPINUS FIBERS BV. “Roxul” includes SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO and the like, and may further include at least one selected from the group consisting of K ₂ O and Na ₂ O.

  Examples of the carbon fibers include flame-resistant fibers, pitch-based carbon fibers, PAN-based carbon fibers, and activated carbon fibers. One type of carbon fiber may be used alone, or two or more types may be used in combination.

  When the friction material composition contains a fibrous base material, the content is preferably 3 to 50% by mass, more preferably 3 to 30% by mass, still more preferably 3 to 20% by mass, and particularly preferably 5 to 15% by mass. % By mass. By setting the content of the fiber base material in the above range, an optimum porosity as a friction material can be obtained, squeal can be prevented, appropriate material strength can be obtained, abrasion resistance can be improved, and moldability can be further improved. There is a tendency that can be improved.

(Binder)
The binder has a function of combining and integrating an organic filler, an inorganic filler, a fiber base material, and the like, and giving a predetermined shape and strength. There is no particular limitation on the binder contained in the friction material composition, but a thermosetting resin generally used as a binder for the friction material can be used.
Examples of the thermosetting resin include a phenol resin, a modified phenol resin, an elastomer-dispersed phenol resin, an epoxy resin, a polyimide resin, and a melamine resin. Here, examples of the modified phenol resin include an acrylic-modified phenol resin, a silicone-modified phenol resin, a cashew-modified phenol resin, an epoxy-modified phenol resin, and an alkylbenzene-modified phenol resin. Examples of the elastomer-dispersed phenolic resin include an acrylic elastomer-dispersed phenolic resin and a silicone elastomer-dispersed phenolic resin.
In particular, a phenol resin, an acryl-modified phenol resin, a silicone-modified phenol resin, and an alkylbenzene-modified phenol resin are preferable, and a phenol resin is more preferable, since they provide good heat resistance, moldability, and friction coefficient.
One thermosetting resin may be used alone, or two or more thermosetting resins may be used in combination.

  When the friction material composition contains a binder, the content is preferably 5 to 25% by mass, more preferably 5 to 20% by mass, still more preferably 6 to 18% by mass, and particularly preferably 6 to 13% by mass. %. When the content of the binder is in the above range, the strength of the friction material is maintained, and deterioration of vibration damping properties such as squealing due to an increase in elastic modulus tends to be more easily suppressed.

(Other materials)
In addition to the above-described materials, other materials can be added to the friction material composition as needed.
Other materials include, for example, organic additives such as fluoropolymers such as polytetrafluoroethylene (PTFE) from the viewpoint of improving abrasion resistance and thermal fade characteristics.
When the friction material composition contains the other materials described above, the content is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and particularly preferably 3% by mass or less. And may not contain other materials.

[Friction material]
The present invention also provides a friction material containing the friction material composition. The friction material may be formed only from the friction material composition of the present invention, or may be a friction material having an upper material and a lower material, wherein at least one of the upper material and the lower material has the friction material. It may be a friction material formed from a material composition. When the friction material is a friction material having an upper material and a lower material, the friction material composition of the present invention is preferably used for the upper material. Referring to FIG. 1, the friction material having an upper material and a lower material will be described. The friction material composition of the present invention usually exhibits a stable friction coefficient at the time of load braking. It is preferable to use it as the upholstery 1. The upper lining material 1 is a friction material serving as a friction surface of the friction member, and the lower lining material 2 is provided between the upper lining material 1 and the back metal 3 and has a shear strength and a shear strength near a bonding portion between the friction material and the back metal. It is a layer for the purpose of improving crack resistance.

The friction material can be produced preferably by molding the friction material composition by heat and pressure molding.
The friction material having the upper material and the lower material is a friction material composition for the upper material and the friction material composition for the lower material, respectively, separately, a Reidige mixer ("Redige" is a registered trademark), Using a mixer such as a pressure kneader and an Eirich mixer (“Eirich” is a registered trademark) or the like, premixing the mixture for the upper material and the mixture for the lower material using a molding die, For example, the obtained preform is molded at a molding temperature of 130 to 160 ° C and a molding pressure of 20 to 50 MPa for 2 to 10 minutes, and the obtained molded product is heat-treated at, for example, 150 to 250 ° C for 2 to 10 hours. Manufactured in. Moreover, you may perform a coating, a scorch process, and a grinding | polishing process as needed. In the above steps, the mixture may be directly thermoformed without the preforming step.

The friction material can be used as a friction material for a disc brake pad of an automobile or the like and a friction material for a drum brake lining of an automobile or the like. The friction material composition can be used as a friction material for a clutch facing, an electromagnetic brake, a holding brake, and the like by performing processes such as molding, processing, and pasting into a desired shape.
The friction material of the present invention is generally excellent in friction coefficient stability during load braking, and thus is suitable as a friction material for vehicles, particularly for vehicles.

  The back metal is usually used as a friction member to improve the mechanical strength of the friction member, and a metal or a fiber-reinforced plastic or the like can be used as a material. Examples of the back metal include iron, stainless steel, inorganic fiber reinforced plastic, carbon fiber reinforced plastic, and the like. The primer layer and the adhesive layer may be any layers that are generally used for friction members such as brake pads and brake linings.

  In the present invention, as for the friction member 6 in FIG. 1, a friction member having a shim 4 on a side of the back metal 3 opposite to a side having the underlining material 2 can also be provided. The shim 4 is a spacer generally used for improving the vibration damping of the friction member.

[car]
The present invention also provides a vehicle equipped with the friction material or the friction member of the present invention. For example, the present invention provides a vehicle using the friction member of the present invention for a disc brake pad, a brake lining, a clutch facing, an electromagnetic brake, a holding brake, and the like. Examples of the car include large cars, medium cars, ordinary cars, large special cars, small special cars, large motorcycles and ordinary motorcycles.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples.

The friction material samples of the examples and comparative examples were measured and evaluated according to the following methods.
[Measurement and evaluation methods]
(1) Evaluation of average value of friction coefficient and stability of friction coefficient during normal load braking First, at the disk rotor temperature of 120 ° C. at the start of braking, braking is performed at 3.5 m / s ² from 65 km / h to 0 km / h. Was repeated 200 times, and the friction coefficient of each braking in the first to 200th braking was measured based on the Japan Society of Automotive Engineers Standard “JASO C406”.
<(1-1) Average value of friction coefficient>
The average friction coefficient of each braking in the 50th to 200th brakes was determined, and their average value [(average friction coefficient for the 50th brake + average friction coefficient for the 51st brake + ... + average friction for the 200th brake) Coefficient / 151] was calculated and evaluated according to the following evaluation criteria. The reason for not considering the friction coefficient up to the 49th brake in the evaluation of the average value of the friction coefficient is that the friction material is low because the surface is not adapted to a new or nearly new friction material and the contact area is small. This is because it is not appropriate to include it in the evaluation of the coefficient of friction. The excellent friction coefficient is in the order of A>B> C.
(Evaluation criteria for average value of friction coefficient of each braking)
A: The average value is 0.37 or more and less than 0.43.
B: The average value is 0.34 or more and less than 0.37, or 0.43 or more and less than 0.47.
C: The average value is less than 0.34 or 0.47 or more.

<(1-2) Stability of friction coefficient>
Further, the average friction coefficient of each braking from the first brake to the 200th brake was calculated, the difference between the maximum value and the minimum value was calculated from the average, and the stability of the friction coefficient was evaluated according to the following criteria. The superior stability of the coefficient of friction is in the order of A>B>C> D.
(Evaluation criteria for stability of friction coefficient)
A: The difference is less than 0.05.
B: The difference is 0.05 or more and less than 0.10.
C: The difference is 0.10 or more and less than 0.20.
D: The difference is 0.20 or more.

<(1-3) 1 Stability of friction coefficient during braking>
Further, for the difference between the maximum value and the minimum value of the friction coefficient that changes during each braking from the first brake to the 200th brake, an average value from the first brake to the 200th brake is calculated, and the friction coefficient during one brake is calculated. Was evaluated according to the following evaluation criteria. The order of A>B> C is excellent in the stability of the friction coefficient during one braking.
(Evaluation criteria for stability of friction coefficient during one braking)
A: The average value is less than 0.20.
B: The average value is 0.20 or more and less than 0.30.
C: The average value is 0.30 or more.

[Production of disc brake pad]
In producing the disc brake pad, the following components of the friction material composition were prepared. Each component described in Table 1 is as follows. The average particle diameter (d50) of bismuth oxide, magnesium oxide and graphite was measured using a laser particle size distribution analyzer “SALD2200” manufactured by Shimadzu Corporation.
(Binder)
・ Phenolic resin (organic filler)
・ NBR: Acrylonitrile-butadiene rubber ・ Pulverized powder of tire tread rubber ・ Cashew particles (bismuth oxide)
・ Bismuth oxide (average particle diameter 0.8μm)
(Inorganic filler for film formation)
・ Tin sulfide ・ Potassium titanate ・ Zinc (inorganic filler)
・ Graphite (average particle diameter 6-9 μm)
・ Alumina ・ Zircon ・ Calcium hydroxide ・ Magnesium oxide (average particle diameter 3-4μm)
・ Barium sulfate (fiber base material)
・ Aramid fiber: fibrillated aramid fiber ・ mineral fiber

[Examples 1 to 3 and Comparative Example 1] (Preparation of disc brake pad)
Each component was blended according to the blending amounts shown in Table 1 to obtain each friction material composition.
This friction material composition was mixed with a Reedige mixer (trade name: Reedige mixer M20, manufactured by Matsubo Corporation) to obtain a mixture. The obtained mixture was preliminarily molded by a molding press (manufactured by Oji Machine Industry Co., Ltd.). The obtained preform was heated together with an iron backing metal (manufactured by Hitachi Automotive Systems, Ltd.) using a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 145 ° C., a molding pressure of 35 MPa, and a molding time of 5 minutes. It was molded under pressure. The obtained molded article was heat-treated at 200 ° C. for 4.5 hours, polished using a rotary polisher, and scorched at 500 ° C. to obtain a disc brake pad. The disc brake pads obtained in the examples and the comparative examples have a friction material thickness of 9.5 mm.
From the obtained disc brake pads, test pieces having a size of 20 mm × 45 mm square were produced by a cutting machine, and each measurement and evaluation were performed according to the above-described methods. Table 1 shows the results.

  It can be seen that the friction material of the example has a small environmental load and is more excellent in stability of the friction coefficient during normal load braking than the friction material of the comparative example.

  The friction member and the friction material of the present invention do not contain copper, or a friction material having a low copper content and a low environmental load, and the stability of the friction coefficient during normal load braking is high. It is suitable as a friction member and a friction material for vehicles and the like.

DESCRIPTION OF SYMBOLS 1 Upper material 2 Lower material 3 Back metal 4 Shim 5 Friction material 6 Friction member

Claims (19)

A friction member having a friction material and a back metal,
The friction material does not contain copper, or even if it contains copper, the content of copper is less than 0.5% by mass as a copper element, and contains bismuth oxide and a film-forming inorganic filler. Element.   The friction member according to claim 1, wherein a melting point of the inorganic filler for forming a film is 800 to 1,200 ° C. 3.   The friction material further contains at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the bismuth oxide and the inorganic filler for forming a film), a fiber base material, and a binder. The friction member according to claim 1.   The inorganic filler may be graphite, calcium hydroxide, calcium oxide, magnesium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, coke, mica, vermiculite, zeolite, zirconium silicate (zircon), zirconia, silica, The friction member according to claim 3, wherein the friction member contains at least one selected from the group consisting of triiron oxide, alumina, and silicon carbide.   The friction member according to any one of claims 1 to 4, wherein a content of the bismuth oxide in the friction material is 0.1 to 20% by mass.   The film-forming inorganic filler contains at least one selected from the group consisting of metal sulfides, titanates, and metals (excluding copper). 3. The friction member according to 1.   The friction member according to any one of claims 1 to 6, wherein the content of the film-forming inorganic filler in the friction material is 5 to 55% by mass.   The friction member according to any one of claims 1 to 7, which is used for a disc brake pad or a drum brake lining.   A vehicle equipped with the friction member according to claim 1.   A friction material composition that does not contain copper or has copper content of less than 0.5% by mass as a copper element even if copper is contained, and contains bismuth oxide and a film-forming inorganic filler. Material composition.   The friction material composition according to claim 10, wherein the melting point of the inorganic filler for forming a film is 800 to 1200C.   Furthermore, it contains at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the bismuth oxide and the film-forming inorganic filler), a fiber base material and a binder. 12. The friction material composition according to item 11.   The inorganic filler may be graphite, calcium hydroxide, calcium oxide, magnesium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, coke, mica, vermiculite, zeolite, zirconium silicate (zircon), zirconia, silica, The friction material composition according to claim 12, comprising at least one selected from the group consisting of triiron oxide, alumina, and silicon carbide.   The friction material composition according to any one of claims 10 to 13, wherein the content of the bismuth oxide is 0.1 to 20% by mass.   The inorganic filler for forming a film contains at least one selected from the group consisting of metal sulfides, titanates and metals (excluding copper). 3. The friction material composition according to item 1.   The friction material composition according to any one of claims 10 to 15, wherein the content of the film-forming inorganic filler is 5 to 55% by mass.   The friction material composition according to any one of claims 10 to 16, which is used for a disc brake pad or a drum brake lining.   A friction material comprising the friction material composition according to claim 10.   A vehicle equipped with the friction material according to claim 18.