JPWO2019151390A1 - Friction material, friction material composition, friction member and vehicle - Google Patents

Abstract

It is a friction material that does not contain copper, or even if it contains copper, whose content is 0.5% by mass or less as a copper element, and contains an inorganic fiber (X1) and a shot (X2) of the inorganic fiber (X1). The present invention relates to a friction material in which the content of the shot (X2) is 0.2% by mass or more in the total amount of the inorganic fibers (X1) and the shot (X2).

Description

The present invention relates to friction materials, friction material compositions, friction members and vehicles.

Friction materials such as disc brake pads and brake linings are used for braking in automobiles and the like. These friction materials play a braking role by rubbing against the disc rotor, brake drum, etc., which are mating materials. Therefore, the friction material is required not only to have an appropriate coefficient of friction (effectiveness characteristic) according to the usage conditions, but also to be less likely to cause brake squeal (squealing characteristic) and to have a long life of the friction material (wear resistance). Etc. are required.

The friction material is a semi-metallic material containing 30 to 60% by mass of steel fiber as a fiber base material, a low steel material containing less than 30% by mass of steel fiber, and a NAО (Non-Asbestos Organic) material containing no steel fiber. It is roughly divided. However, friction materials containing a small amount of steel fibers may also be classified as NAO materials.

Since the NAО material does not contain steel fibers, it is characterized in that it is less aggressive to the disc rotor, which is the mating material, as compared with the semi-metallic material and the low steel material. Due to these advantages, NAО materials, which are effective and have an excellent balance of squeal and wear resistance, are currently the mainstream in Japan, the United States, and the like. On the other hand, in Europe, low-steel materials were often used from the viewpoint of maintaining the friction coefficient during high-speed braking, but in recent years, NAO materials that are less likely to cause tire wheel stains and brake squeal in order to respond to the trend toward higher-end markets. Is being used more and more.

The NAO material generally contains copper in the form of powder or fiber. However, it has been suggested that friction materials containing copper, copper alloys, etc. may contaminate rivers, lakes, etc. because copper is contained in the abrasion powder generated during braking. Therefore, in California, Washington, etc. in the United States, there is a bill prohibiting 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 assembly to new cars. It has been passed, and there is an urgent need to develop NAO materials that do not contain copper or have a low copper content in order to respond to this.

One of the typical functions of copper is to impart thermal conductivity. Since copper has high thermal conductivity, the heat generated during braking is diffused from the friction interface to suppress wear due to excessive temperature rise.
The second typical function of copper is the protection of the friction interface during high temperature braking.
Since copper has high ductility and malleability, it extends to the surface of the friction material by braking to form a film. As a result, it is possible to reduce the wear of the friction material during high-speed high-temperature braking and to develop a stable friction coefficient. Further, since the copper spreading film easily holds the abrasive, a good friction coefficient can be exhibited even in a low-speed low-temperature braking region.
Therefore, in order to develop a NAO material that does not contain copper or has a low copper content, a copper alternative technology is required from the viewpoints of improving thermal conductivity, protecting the interface, and retaining the abrasive as described above. ..

In such a movement, friction materials that do not contain copper or have a low copper content have been studied (for example, Patent Documents 1 and 2 and the like).

Japanese Unexamined Patent Publication No. 2015-205959 Japanese Unexamined Patent Publication No. 2015-059125

Moreover, in recent years, an important problem has arisen from a viewpoint different from the above-mentioned copper substitution. It is the compatibility with control brakes represented by regenerative braking. In the conventional hydraulic brake, the driver fine-tunes the input from the brake pedal to adjust the braking force of the vehicle in a timely manner.
However, in the control brake, since the system side is responsible for a part of the braking, if the friction coefficient developed by the friction material fluctuates extremely, a control problem will occur. For example, if the coefficient of friction is extremely low, the braking distance becomes too long, which may cause an accident in the worst case. Therefore, in order to improve the accuracy of the control brake, it is extremely important that the friction coefficient developed by the friction material is stable at all times.

A typical example in which the friction coefficient fluctuates is a decrease in the friction coefficient in the low-speed low-temperature braking range in a friction material containing no copper. With a friction material that does not contain copper, it is difficult to form a transfer film on the surface of the disc rotor in the low-speed low-temperature braking range, and it is difficult to exhibit the effect of holding the abrasive. As a result, the aggression to the disc rotor due to the grinding action and the shear drag generated between the iron component derived from the disc rotor and the disc rotor are reduced, so that the friction coefficient tends to be lower than in the normal state. In that case, as described above, problems such as a long braking distance and a decrease in braking force occur, and the comfort of the driver is impaired.

In addition, an increase in the coefficient of friction fluctuation during one braking in low-speed low-temperature braking is also cited as a typical example of fluctuation in the friction coefficient. With a friction material that does not contain copper, the discharge of wear debris generated during braking is low, and the wear debris tends to accumulate at the friction interface between the friction material and the disc rotor. As a result, the powder resistance at the friction interface increases, and the volatility of the friction coefficient increases. This causes problems such as squealing when the vehicle is stopped with the brake applied, and the driver's comfort is impaired.

In the regenerative brake, the ratio of the braking force obtained by friction is reduced, that is, the braking load is reduced as compared with the conventional hydraulic brake. Therefore, it becomes difficult to remove the rust that has rusted on the surface of the rotor, and sticking due to rust occurs between the rotor and the brake pad, and the friction material may be separated at the time of starting. Therefore, in order to improve the compatibility with the regenerative brake, it is required to give the brake pad a performance capable of removing rust rusted on the rotor surface.

From this point of view, the techniques disclosed in Patent Documents 1 and 2 focus only on the high thermal conductivity and high-temperature lubricity of copper, and only complement the frictional characteristics during high-speed high-temperature braking. However, the stability of the friction coefficient in the low-speed low-temperature braking range, rust removal property, and other friction characteristics are not considered.

Therefore, the present invention has a composition that does not contain copper, or even if it contains copper, has a content of 0.5% by mass or less as a copper element, which is less harmful to the environment and human body, and is excellent in a low-speed low-temperature braking range. It is an object of the present invention to provide a friction material, a friction material composition, a friction member using the friction material, and a vehicle, which have both stability of the friction coefficient and an excellent friction coefficient in a normal braking range and are excellent in rust removing property. ..

As a result of intensive research to achieve the above object, the present inventor has found that a friction material containing an inorganic fiber containing a specific amount of shots has excellent friction coefficient stability in a low-speed low-temperature braking range and is usually It was found that the friction coefficient in the braking range is compatible with the excellent rust removing property. That is, the present invention relates to the following [1] to [20].
[1] A friction material that does not contain copper, or has a copper element content of 0.5% by mass or less as a copper element, and is a shot (X2) of an inorganic fiber (X1) and the inorganic fiber (X1). A friction material containing, and the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fibers (X1) and the shot (X2).
[2] The friction material according to the above [1], wherein the average fiber length of the inorganic fiber (X1) is 100 to 800 μm.
[3] The total content of the inorganic fibers (X1) and shots (X2) is 1.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of friction material. The friction material according to [2].
[4] The above-mentioned [1] to [3], wherein the content of the shot (X2) is 0.2 to 10% by mass based on the total amount of the inorganic fibers (X1) and the shot (X2). Friction material.
[5] The friction material according to any one of the above [1] to [4], wherein the content of Al ₂ O _{3 in} the inorganic fiber (X1) and the shot (X2) is 1 to 35% by mass.
[6] Further, as the inorganic filler, zirconium silicate having an average particle diameter of 0.4 to 2 μm is contained in an amount of 4 to 10% by mass based on 100% by mass of the total amount of the friction material, as described above [1] to [5]. The friction material described in any of.
[7] Further, as the inorganic filler, a non-needle-shaped titanate having an average particle diameter of 2 to 50 μm is contained in an amount of 15 to 25% by mass based on 100% by mass of the total amount of the friction material [1]. ] To [6].
[8] The friction material according to any one of the above [1] to [7], further containing 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material.
[9] The friction material according to any one of the above [1] to [8], further containing 2 to 10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total amount of the friction material.
[10] A friction member in which the friction material according to any one of [1] to [9] above and a back metal are integrated.
[11] A vehicle equipped with the friction member according to the above [10].
[12] A friction material composition that does not contain copper, or even if it contains copper, has a content of 0.5% by mass or less as a copper element, and is a shot of an inorganic fiber (X1) and the inorganic fiber (X1). A friction material composition containing X2) and the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fibers (X1) and the shot (X2).
[13] The friction material composition according to the above [12], wherein the average fiber length of the inorganic fiber (X1) is 100 to 800 μm.
[14] The total content of the inorganic fibers (X1) and shots (X2) is 1.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of the friction material composition. ] Or the friction material composition according to [13].
[15] The above-mentioned [12] to [14], wherein the content of the shot (X2) is 0.2 to 10% by mass based on the total amount of the inorganic fibers (X1) and the shot (X2). Friction material composition.
[16] The friction material composition according to any one of the above [12] to [15], wherein the content of Al ₂ O _{3 in} the inorganic fiber (X1) and the shot (X2) is 1 to 35% by mass. Stuff.
[17] Further, as the inorganic filler, zirconium silicate having an average particle diameter of 0.4 to 2 μm is contained in an amount of 4 to 10% by mass based on 100% by mass of the total amount of the friction material composition, as described above [12] to [ 16] The friction material composition according to any one of.
[18] Further, as the inorganic filler, titanate which is non-needle-shaped and has an average particle diameter of 2 to 50 μm is contained in an amount of 15 to 25% by mass based on 100% by mass of the total amount of the friction material composition. The friction material composition according to any one of [12] to [17].
[19] The friction material according to any one of [12] to [18] above, further containing 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material composition. Composition.
[20] The friction according to any one of [12] to [19] above, further containing 2 to 10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total amount of the friction material composition. Material composition.

According to the present invention, the composition does not contain copper, or even if it contains copper, the content thereof is 0.5% by mass or less as a copper element, which is less harmful to the environment and human body, and is excellent in a low-speed low-temperature braking range. It is possible to provide a friction material, a friction material composition, a friction member using the friction material, and a vehicle, which have both stability of the friction coefficient and an excellent friction coefficient in a normal braking range and are excellent in rust removing property.

Hereinafter, the friction material, the friction material composition, and the friction member of the present embodiment will be described in detail, but the present invention is not limited to the following embodiments.
The friction material and the friction material composition of the present embodiment do not contain asbestos, and are so-called non-asbestos friction materials and non-asbestos friction material compositions.

[Friction material and friction member]
The friction material according to the present embodiment is a friction material that does not contain copper, or even if it contains copper, the content thereof is 0.5% by mass or less as a copper element, and the inorganic fiber (X1) and the inorganic fiber (X1). ) Is contained, and the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fibers (X1) and the shot (X2).

The friction material of the present embodiment does not contain copper, or even if it contains copper, the content thereof is as small as 0.5% by mass or less as a copper element. Therefore, the friction material of the present embodiment has low environmental hazards and human body hazards.
The above-mentioned "copper" is copper in the form of fibrous or powder; a copper element contained in a copper alloy, a copper compound, etc., and the "copper content" is the content based on 100% by mass of the total amount of friction material. Shown.
The copper content is preferably less than 0.5% by mass, more preferably 0.3% by mass or less, and 0.1% by mass, based on 100% by mass of the total amount of friction material, from the viewpoint of environmental harm and human body harm. % Or less is more preferable, and copper is particularly preferable.

<Friction material components>
The friction material of the present embodiment preferably contains one or more selected from the group consisting of a fiber base material, an inorganic filler, an organic filler and a binder.
Hereinafter, each component contained in the friction material of the present embodiment will be described.

<Fiber base material>
The friction material according to the present embodiment contains inorganic fibers as a fiber base material.
Inorganic fiber is a component that not only reinforces the friction material by its fibrous shape, but also adjusts the friction characteristics such as friction coefficient and rotor aggression by selecting various material characteristics such as composition, fiber length, and toughness. is there.

(Inorganic fiber (X1) and shot (X2))
The friction material according to the present embodiment contains an inorganic fiber (X1) and a shot (X2) of the inorganic fiber (X1), and the content of the shot (X2) is the inorganic fiber (X1) and the shot (X2). ) Is 0.2% by mass or more in the total amount.
The friction material of the present embodiment has excellent rust removing property when the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fibers (X1) and the shot (X2). ..
In addition, the "shot" in this specification is a non-fibrous particle which cannot become a fiber and remains as a grain in the manufacturing process of an inorganic fiber, and has a particle diameter of 125 μm or more. Here, the "particle size of the shot" means the major axis of the particles in the particle projection image, and can be measured using, for example, a scanning electron microscope (SEM).

The inorganic fiber (X1) is not particularly limited, but is preferably a mineral fiber.
The mineral fiber referred to here is an artificial inorganic fiber melt-spun mainly containing blast furnace slag such as slag wool, basalt fiber and the like; and other natural rocks as a main component, and is a natural mineral containing an Al element. Is more preferable. Specifically, those containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, Fe ₂ O ₃ , Na ₂ O and the like can be used as the mineral fiber.

The inorganic fiber (X1) is preferably an inorganic fiber having biosolubility.
The biosoluble inorganic fiber referred to here has a characteristic that it is partially decomposed in a short time and discharged to the outside of the body even when it is taken into the human body, and examples thereof include biosoluble mineral fibers. .. Specifically, in a short-term biopermanent test by breathing, the chemical composition is 18% by mass or more of the total amount of alkaline oxides and alkaline earth oxides (total amount of oxides of sodium, potassium, calcium, magnesium, and barium). Inorganic fibers with a mass half-life of 20 μm or greater within 40 days, or satisfying that there is no evidence of excessive carcinogenicity in intraperitoneal studies or no associated pathogenicity and tumorigenesis in long-term respiratory studies (EU). NotaQ of Directive 97/69 / EC (carcinogenic exemption)).
Examples of such inorganic fibers (X1) include SiO _2- Al ₂ O ₃ -CaO-MgO-Fe ₂ O _3- Na ₂ O-based fibers, SiO ₂ , Al ₂ O ₃ , CaO, MgO, and the like. Examples thereof include fibers containing Fe ₂ O ₃ , Na ₂ O and the like in any combination.

The inorganic fiber (X1) is preferably an inorganic fiber containing calcium oxide (hereinafter, also referred to as “CaO”) and magnesium oxide (hereinafter, also referred to as “MgO”).
The above-mentioned "inorganic fiber containing CaO and MgO" means an inorganic fiber containing CaO and MgO as a component constituting one fiber, and the same applies to each component other than CaO and MgO described later. Is. The content of each component in the following inorganic fibers (X1) is a content based on 100% by mass of the total amount of the inorganic fibers (X1).
The content of CaO in the inorganic fiber (X1) is preferably 15 to 30% by mass, more preferably 17 to 25% by mass, and even more preferably 18 to 22% by mass.
The content of MgO in the inorganic fiber (X1) is preferably 3 to 20% by mass, more preferably 4 to 15% by mass, and even more preferably 5 to 8% by mass.
The total content of CaO and MgO in the inorganic fiber (X1) is preferably 18 to 40% by mass, more preferably 22 to 35% by mass, and even more preferably 25 to 30% by mass.

The inorganic fiber (X1) may contain other oxides other than CaO and MgO. Examples of other oxides include SiO ₂ , Al ₂ O ₃ , Na ₂ O, K ₂ O, TiO ₂ , P ₂ O ₅ , MnO, Fe ₂ O ₃ , SrO, ZrO _{2, and the} like. Among these, it is preferable to contain SiO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ .
When the inorganic fiber (X1) contains one or more selected from the group consisting of SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , the content in the inorganic fiber (X1) is as follows. ..
The content of SiO ₂ is preferably 10 to 60% by mass, more preferably 30 to 50% by mass, further preferably 35 to 47% by mass, and particularly preferably 40 to 45% by mass.
The content of Al ₂ O ₃ is preferably 1 to 35% by mass, more preferably 5 to 32% by mass, further preferably 10 to 30% by mass, further preferably 13 to 25% by mass, and 15 to 20% by mass. Is particularly preferable.
The content of Fe ₂ O ₃ is preferably 1 to 10% by mass, more preferably 2 to 9% by mass, still more preferably 4 to 8% by mass.
The total content of CaO, MgO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O _{3 in} the inorganic fiber (X1) is preferably 90% by mass or more, more preferably 93% by mass or more, and further preferably 95% by mass or more. preferable. Further, the total content may be 100% by mass or less, 98% by mass or less, or 97% by mass or less.

When the inorganic fiber (X1) further contains one or more selected from the group consisting of Na ₂ O, K ₂ O, TiO ₂ , P ₂ O ₅ and Mn O, the content thereof in the inorganic fiber (X1). The amount is as follows.
The content of Na ₂ O is preferably 1 to 5% by mass, more preferably 1.5 to 4% by mass, and even more preferably 2 to 3% by mass.
The content of K ₂ O is preferably 0.1 to 1.5% by mass, more preferably 0.2 to 1.2% by mass, and even more preferably 0.4 to 0.8% by mass.
The content of TiO ₂ is preferably 0.2 to 3% by mass, more preferably 0.7 to 2% by mass, and even more preferably 1 to 1.5% by mass.
The content of P ₂ O ₅ is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.5% by mass, and even more preferably 0.15 to 0.3% by mass.
The content of MnO is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, and even more preferably 0.07 to 0.2% by mass.
The total content of one or more selected from the group consisting of Na ₂ O, K ₂ O, TiO ₂ , P ₂ O ₅ and MnO in the inorganic fiber (X1) is preferably 0.5 to 10% by mass. 2 to 7% by mass is more preferable, and 3 to 5% by mass is further preferable.
The content of SrO in the inorganic fiber (X1) is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, from the viewpoint of rust removing property and stability of the friction coefficient in the low-speed low-temperature braking range. .. Further, from the same viewpoint, it is more preferable that the inorganic fiber (X1) does not contain SrO.
The content of ZrO ₂ in the inorganic fiber (X1) is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, from the viewpoint of rust removing property and stability of the friction coefficient in the low-speed low-temperature braking range. preferable. Further, from the same viewpoint, it is more preferable that the inorganic fiber (X1) does not contain ZrO ₂ .

The content of CaO, MgO and other oxides in the inorganic fiber (X1) can be measured by fluorescent X-ray analysis. Further, the content of the oxide can be the content of each oxide converted from the content of atoms other than oxygen forming the oxide.

The average fiber length of the inorganic fiber (X1) is preferably 100 to 800 μm, more preferably 140 to 500 μm, and even more preferably 170 to 300 μm. When the average fiber length is in the above range, the stability of the friction coefficient can be improved without causing adverse effects such as a significant increase in rotor aggression.
The average fiber diameter of the inorganic fiber (X1) is preferably 1 to 10 μm, more preferably 2 to 8 μm, still more preferably 3 to 6 μm. When the average fiber diameter is in the above range, the stability of the friction coefficient can be improved without causing adverse effects such as a significant increase in rotor aggression.
Here, the average fiber length and the average fiber diameter refer to a number average fiber length or a number average fiber diameter indicating an average value of the lengths or diameters of the corresponding fibers. For example, the average fiber length of 200 μm means that 50 fibers used as a raw material of the friction material composition are randomly selected, the fiber length is measured with an optical microscope, and the average value is 200 μm.

As described above, the friction material of the present embodiment contains an inorganic fiber (X1) and a shot (X2) generated in the manufacturing process of the inorganic fiber (X1).
Therefore, the shot (X2) has the same material as the inorganic fiber (X1).
Since the shot (X2) is generally mixed in the inorganic fiber (X1) used as a raw material, the inorganic fiber (X1) and the shot (X2) are usually mixed in the manufacturing process of the friction material. The shot (X2) isolated from the inorganic fiber (X1) may be blended separately from the inorganic fiber (X1).

The average particle size of the shot (X2) is preferably 125 to 300 μm, more preferably 125 to 200 μm, and even more preferably 125 to 150 μm from the viewpoint of rust removal property.
The average particle size of the shots (X2) can be obtained as an average value by measuring the particle size of any 50 shots using, for example, a scanning electron microscope (SEM). The definitions of "shot" and "shot particle size" here are as described above.

The content of the shot (X2) is 0.2% by mass or more, preferably 0.2 to 20% by mass, based on the total amount of the inorganic fibers (X1) and the shot (X2) from the viewpoint of rust removal property. 2 to 15% by mass is more preferable, 0.2 to 12% by mass is further preferable, 0.2 to 10% by mass is further preferable, 0.2 to 8% by mass is further preferable, and 0.2 to 6% by mass is preferable. % Is particularly preferable, and 0.2 to 5% by mass is most preferable.

The content of the shot (X2) in the friction material of the present embodiment is preferably 0.001 to 2% by mass, more preferably 0.002 to 1% by mass, based on 100% by mass of the total amount of the friction material. It is more preferably 003 to 0.75% by mass, further preferably 0.005 to 0.5% by mass, particularly preferably 0.007 to 0.3% by mass, and most preferably 0.01 to 0.25% by mass.

The total content of the inorganic fibers (X1) and shots (X2) in the friction material of the present embodiment is 1.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of the friction material. preferable. When the total content is in the above range, stability of a high friction coefficient can be obtained in the low-speed low-temperature braking range, the fluctuation coefficient of the friction coefficient during one braking is small, and an excellent friction coefficient can be obtained in the normal braking range. .. In particular, when the content of the inorganic fiber (X) is 1.0% by mass or more, the friction coefficient stability in the low-speed low-temperature braking region can be ensured, and the friction coefficient fluctuation rate during one braking can be reduced. Further, when the content of the inorganic fiber (X) is less than 10.0% by mass, the friction coefficient stability in the low-speed low-temperature braking range becomes good while ensuring that the friction coefficient fluctuation rate during one braking is low. ..
From the same viewpoint, the total content of the inorganic fibers (X1) and shots (X2) in the friction material of the present embodiment is 2.0 to 9.9% by mass with respect to 100% by mass of the total amount of the friction material. Preferably, 4.0 to 8% by mass is further preferable, and 5.0 to 7% by mass is even more preferable.

The friction material of the present embodiment preferably contains at least one selected from the group consisting of organic fibers, other inorganic fibers and metal fibers, in addition to the inorganic fibers (X1). These fiber substrates exhibit a reinforcing action in the friction material. As for the organic fiber, other inorganic fiber and the metal fiber, one type may be used alone or two or more types may be used in combination.
The friction material of the present embodiment does not contain metal fibers, or even if it contains metal fibers, the total amount of the friction material is 100% by mass from the viewpoint of not excessively increasing the aggression to the disc rotor which is the mating material. On the other hand, it is preferably 0.5% by mass or less.

(Organic fiber)
Examples of the organic fiber include aramid fiber, acrylic fiber, cellulose fiber and the like. Among these, aramid fiber is preferable from the viewpoint of heat resistance, reinforcing effect and appropriate voiding. As the aramid fiber, a known material used for the friction material can be used. The average fiber length of the organic fiber is, for example, 650 to 1500 μm, preferably 1000 to 1300 μm. The method for measuring the average fiber length is the same as described above.
When the friction material of the present embodiment contains organic fibers, the total content thereof is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, based on 100% by mass of the total amount of the friction material. ~ 4% by mass is more preferable.

(Other inorganic fibers)
Examples of other inorganic fibers include ceramic fibers, biodegradable ceramic fibers, mineral fibers, carbon fibers, glass fibers, potassium titanate fibers and the like. From the viewpoint of harmfulness to the human body, it is preferable not to contain potassium titanate fiber or the like. Further, if the amount of the inorganic fiber having high toughness added is excessively large, the rotor aggression is remarkably deteriorated. Therefore, from the viewpoint of the toughness of the inorganic fiber, it is preferable not to contain the ceramic fiber and the carbon fiber.
Further, the friction material of the present embodiment may not contain other inorganic fibers, depending on the desired performance.
In this specification, metal fibers are not included in the definition of inorganic fibers.

The total content of the fiber base material in the friction material of the present embodiment is preferably 6 to 20% by mass, more preferably 7 to 17% by mass, and 8 to 15% by mass with respect to 100% by mass of the total amount of the friction material. More preferred. When the total content of the fiber base material is in the above range, stability with a higher coefficient of friction can be obtained in the low-speed low-temperature braking region and the normal braking region.

<Inorganic filler>
The friction material of the present embodiment preferably contains an inorganic filler.
Examples of the inorganic filler include titanate, wollastonite, metal powder, graphite, various oxides used as abrasives, and other inorganic fillers.
As the inorganic filler, one type may be used alone, or two or more types may be used in combination.
Examples of the metal powder include iron powder, tin powder, zinc powder, aluminum powder, and alloy powders thereof.
However, the friction material of the present embodiment does not contain metal powder, or even if it contains metal powder, the total amount of the friction material is 100% by mass from the viewpoint of not excessively increasing the aggression to the disc rotor which is the mating material. On the other hand, it is preferably less than 0.5% by mass, more preferably less than 0.1% by mass, and even more preferably less than 0.01% by mass.

(Titanate)
The friction material of the present embodiment preferably contains titanium salt as an inorganic filler.
Since titaniumate has a low Mohs hardness of about 4 and a relatively high melting point of 1000 ° C. or higher, it is possible to reduce an increase in wear of the friction material by intervening at the friction interface during high-speed high-temperature braking.
Examples of the titanate include potassium hexatitanate, potassium octatitanate, lithium potassium titanate, magnesium potassium titanate, sodium titanate and the like. Among these, potassium hexatitanium and potassium octatitanate are preferable from the viewpoint of stability of the friction coefficient in the low-speed low-temperature braking range.
As the titanate, one type may be used alone or two or more types may be used in combination, but from the viewpoint of wear resistance during high-speed high-temperature braking, one type of titanium salt may be used alone. preferable.

Titanate is preferably non-needle-shaped from the viewpoint of harm to the human body. That is, the friction material of the present embodiment preferably contains a non-needle-shaped titanate. The non-needle-shaped titanium salt means a plate-shaped titanium salt having a polygonal, circular, elliptical shape, or an indefinite shape.
The average particle size of the titanate is preferably 2 to 50 μm, more preferably 2.2 to 40 μm, and even more preferably 2.5 to 30 μm.
Unless otherwise specified, the average particle size in the present specification means a median diameter (D ₅₀ ), and can be measured by using a method such as laser diffraction particle size distribution measurement. As the measuring device, for example, a laser diffraction / scattering type particle size distribution measuring device, trade name: LA-920 (manufactured by Horiba Seisakusho Co., Ltd.) can be used. It can also be measured by sieving classification represented by JISB 4130 or the like.

When the friction material of the present embodiment contains titanium salt, the content thereof is preferably 15 to 25% by mass, more preferably 15 to 22% by mass, and 15 to 20% by mass with respect to 100% by mass of the total amount of the friction material. Mass% is more preferred. When the content of titanium salt is at least the above lower limit value, the wear resistance during high-speed high-temperature braking is excellent, and the effect of maintaining a sufficient friction coefficient is obtained. When it is at least the above upper limit value, the low-speed low-temperature braking range It is possible to suppress a decrease in the friction coefficient in.
From the viewpoint of the stability of the friction coefficient, the friction material of the present embodiment is a non-needle-shaped titanate having an average particle diameter of 2 to 50 μm, which is 15 to 25 mass by mass with respect to 100 mass% of the total amount of the friction material. % Is particularly preferable.

(Wollast Night)
Wollastonite is a silicate mineral represented by CaSiO ₃ , for example, having a needle-like or oblong columnar shape.
The average aspect ratio (average length / average diameter or thickness) of wollastonite is preferably 3 or more, more preferably 4 to 12, and even more preferably 5 to 8. When the average aspect ratio is 3 or more, the shear strength and crack resistance of the friction material at normal temperature and high temperature can be effectively improved. The average aspect ratio refers to D ₅₀ value (cumulative median of the volume distribution), for example, it can be measured by a dynamic image analysis method.
The average length of the wollastonite is preferably 100 to 500 μm, more preferably 150 to 450 μm, and even more preferably 200 to 400 μm from the viewpoint of imparting strength to the friction material.
When the friction material of the present embodiment contains wollastonite, the content thereof is preferably 2 to 10% by mass, more preferably 3 to 8% by mass, and 4 to 7 with respect to 100% by mass of the total amount of the friction material. Mass% is more preferred.

(Abrasive)
The friction material of the present embodiment may contain zirconium silicate, triiron tetroxide, triiron dioxide, bismuth oxide, zirconium oxide or the like as an abrasive. Among these, zirconium silicate and zirconium oxide are preferable.

Zirconium silicate has a high Mohs hardness of 6 to 7.5 and is effective in developing a friction coefficient by grinding.
The average particle size of zirconium silicate is preferably 0.2 to 2 μm, more preferably 0.3 to 2 μm, and even more preferably 0.4 to 2 μm.
When the friction material of the present embodiment contains zirconium silicate, the content thereof is preferably 4 to 10% by mass, more preferably 5 to 10% by mass, based on 100% by mass of the total amount of the friction material.
From the viewpoint of the stability of the friction coefficient, the friction material of the present embodiment may contain 4 to 10% by mass of zirconium silicate having an average particle diameter of 0.4 to 2 μm with respect to 100% by mass of the total amount of the friction material. Especially preferable.
The friction material of the present embodiment may not contain zirconium silicate, depending on the desired performance.

The average particle size of zirconium oxide is preferably 1 to 14 μm, more preferably 5 to 10 μm, and even more preferably 8 to 9 μm.
When the friction material of the present embodiment contains zirconium oxide, the content thereof is preferably 10 to 20% by mass, more preferably 12 to 19% by mass, and 14 to 18% by mass with respect to 100% by mass of the total amount of the friction material. % Is more preferable. When the content of zirconium oxide is at least the above lower limit value, the wear resistance during high-speed high-temperature braking is excellent, and the effect of maintaining a sufficient coefficient of friction can be obtained. It is possible to suppress a decrease in the coefficient.

(graphite)
The friction material of the present embodiment preferably contains graphite. By containing graphite, excellent thermal conductivity can be imparted to the friction material.
The average particle size of graphite is preferably 100 to 600 μm, more preferably 200 to 450 μm, and even more preferably 300 to 350 μm. Further, the average particle size of graphite may be 10 to 90 μm or 20 to 60 μm depending on the desired thermal conductivity. As the graphite, two or more kinds having different average particle diameters may be used in combination. For example, graphite (I) having an average particle diameter of 100 to 600 μm, preferably 200 to 450 μm and an average particle diameter of 10 to 90 μm may be used. Graphite (II), preferably 20 to 60 μm, may be used in a mass ratio (graphite (I) / graphite (II)) of 0.5 to 5, preferably 1 to 2.
When the friction material of the present embodiment contains graphite, the total content thereof is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and 2 to 2 to 5% by mass with respect to 100% by mass of the total amount of the friction material. 4% by mass is more preferable.
When the average particle size and the total content of graphite are in the above ranges, it is possible to both impart thermal conductivity to a good friction material and maintain a friction coefficient.

(Other inorganic fillers)
Other inorganic fillers include magnesium oxide, antimony trisulfide, zirconium hydroxide, tin sulfide, molybdenum disulfide, bismuth sulfide, zinc sulfide, iron sulfide, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate. , Barium sulfate, coke, γ-alumina, α-alumina, mica, vermiculite, calcium sulfate, mulite, chromate, titanium oxide, silica and the like. Among these, antimony trisulfide, tin sulfide, mica, calcium hydroxide, and barium sulfate are preferable. As these other inorganic fillers, general ones used for friction materials can be used.

When the friction material of the present embodiment contains tin sulfide, the content thereof is preferably 0.5 to 5% by mass, more preferably 1.5 to 3% by mass, based on 100% by mass of the total amount of the friction material.
The average particle size of tin sulfide is preferably 100 to 800 μm, more preferably 200 to 700 μm, and even more preferably 250 to 650 μm.
When the friction material of the present embodiment contains antimony trisulfide, the content thereof is preferably 0.2 to 4% by mass, more preferably 1.0 to 2% by mass, based on 100% by mass of the total amount of the friction material. ..
The average particle size of antimony trisulfide is preferably 10 to 300 μm, more preferably 20 to 200 μm, and even more preferably 30 to 170 μm.
When the friction material of the present embodiment contains mica, the content thereof is preferably 1 to 10% by mass, more preferably 3 to 7% by mass, based on 100% by mass of the total amount of the friction material.
The average particle size of mica is preferably 5 to 100 μm, more preferably 10 to 60 μm, and even more preferably 12 to 20 μm.
When the friction material of the present embodiment contains calcium hydroxide, the content thereof is preferably 0.01 to 1% by mass, preferably 0.05 to 0.3% by mass, based on 100% by mass of the total amount of the friction material. More preferred.
The average particle size of calcium hydroxide is preferably 10 to 300 μm, more preferably 30 to 200 μm, and even more preferably 50 to 100 μm.
When the friction material of the present embodiment contains barium sulfate, the content thereof is preferably 5 to 20% by mass, more preferably 8 to 12% by mass, based on 100% by mass of the total amount of the friction material.
The average particle size of barium sulfate is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm.
When the friction material of the present embodiment contains another inorganic filler, the total content thereof is preferably 12 to 50% by mass, more preferably 15 to 40% by mass, based on 100% by mass of the total amount of the friction material. 20 to 35% by mass is more preferable.

The total content of the inorganic filler in the friction material of the present embodiment is preferably 50 to 85% by mass, more preferably 60 to 80% by mass, and 65 to 75% by mass with respect to 100% by mass of the total amount of the friction material. More preferred.

<Organic filler>
The friction material of the present embodiment preferably contains an organic filler. The organic filler is contained as a friction modifier for improving the sound vibration performance, wear resistance, etc. of the friction material.
As the organic filler, one type may be used alone, or two or more types may be used in combination.
Examples of the organic filler include cashew dust and rubber components.
The cashew dust may be, for example, one usually used as a friction material, which is obtained by pulverizing a polymerized and cured cashew nut shell oil. The cashew dust is preferably unmodified cashew dust.
The average particle size of cashew dust is preferably 50 to 600 μm, more preferably 70 to 550 μm, and even more preferably 100 to 500 μm.
When the friction material of the present embodiment contains cashew dust, the content thereof is preferably 4 to 20% by mass, more preferably 8 to 16% by mass, and 10 to 14% by mass with respect to 100% by mass of the total amount of the friction material. % Is more preferable.
When the content of cashew dust is within the above range, it is possible to improve the sound vibration performance such as squealing due to the low elasticity of the friction material.

As the rubber component, known rubber components used for friction materials can be used, and examples thereof include tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), and SBR (styrene butadiene rubber).
When the friction material of the present embodiment contains a rubber component, the content thereof is preferably 0.2 to 10% by mass, more preferably 0.5 to 5% by mass, based on 100% by mass of the total amount of the friction material. 1 to 3% by mass is more preferable.

The friction material of the present embodiment preferably contains at least one selected from the group consisting of cashew dust and a rubber component, and more preferably a cashew dust and a rubber component are used in combination. When cashew dust and a rubber component are used in combination, cashew dust coated with a rubber component may be used, or cashew dust and a rubber component may be mixed separately from the viewpoint of sound vibration performance. Good.

When the friction material of the present embodiment contains an organic filler, the total content thereof is preferably 2 to 20% by mass, more preferably 5 to 17% by mass, and 10 to 10% by mass with respect to 100% by mass of the total amount of the friction material. 15% by mass is more preferable.
When the total content of the organic filler is within the above range, the sound vibration performance such as squealing due to the low elasticity of the friction material can be improved, and the deterioration of heat resistance and the decrease in strength due to the heat history can be avoided.

<Binder>
The friction material of the present embodiment preferably further contains a binder. The binder is a material that integrates the organic filler, fiber base material, etc. contained in the friction material to give strength.
As the binder, one type may be used alone, or two or more types may be used in combination.
As the binder, a thermosetting resin usually used as a friction material can be used.
Examples of the thermosetting resin include various modified phenol resins such as phenol resins, acrylic rubber-modified phenol resins, silicone-modified phenol resins, cashew-modified phenol resins, epoxy-modified phenol resins, and alkylbenzene-modified phenol resins. Among these, a silicone-modified phenol resin is preferable from the viewpoint of being able to enhance the water repellency of the friction interface. As the silicone-modified phenol resin, a phenol resin in which silicone oil or silicone rubber is dispersed is preferable. The silicone-modified phenol resin may be used alone, or may be used in combination with a thermosetting resin other than the above-mentioned silicone-modified phenol resin, and is preferably used in combination with an acrylic rubber-modified phenol resin.
When the silicone-modified phenol resin and the acrylic rubber-modified phenol resin are used in combination, the content ratio [silicone-modified phenol resin: acrylic rubber-modified phenol resin] is preferably 20:80 to 80:20, preferably 30: 70 to 70:30 is more preferable, and 40:60 to 60:40 is even more preferable.

The total content of the binder in the friction material of the present embodiment is preferably 4 to 14% by mass, more preferably 6 to 12% by mass, and further 8 to 10% by mass with respect to 100% by mass of the total amount of the friction material. preferable.
When the total content of the binder is within the above range, the decrease in the strength of the friction material can be further suppressed, the porosity of the friction material is reduced, and the deterioration of sound vibration performance such as squeal due to the high elastic modulus is suppressed. it can.

<Other ingredients>
The friction material of the present embodiment may contain other materials other than the above-mentioned components, if necessary.

<Manufacturing method of friction material>
The friction material of the present embodiment can be produced by a commonly used method.
Examples of the method for producing the friction material of the present embodiment include a method of heat-press molding a friction material composition satisfying the composition of the friction material of the present embodiment. Specifically, for example, the friction material composition of the present embodiment described later is uniformly mixed using a mixer such as a Raydige (registered trademark) mixer, a pressurized kneader, or an Erich (registered trademark) mixer, and this mixture is mixed. Pre-molded with a molding die, the obtained pre-molded product was molded under the conditions of a molding temperature of 140 to 150 ° C., a molding pressure of 30 to 45 MPa, and a molding time of 3 to 6 minutes, and the obtained molded product was 180 to 210. A method of heat-treating at ° C. for 3 to 4 hours can be mentioned. If necessary, painting, scorch treatment, polishing treatment and the like may be performed.

<Use of friction material>
The friction material of the present embodiment is used, for example, in the following aspects (1) to (3).
(1) Configuration of only friction material (2) Friction member having a back metal and a friction material of the present embodiment which is a friction surface formed on the back metal (3) In the configuration of (2) above, the back metal A structure in which a primer layer for surface modification to enhance the adhesive effect of the back metal and an adhesive layer for adhesion between the back metal and the friction member are further interposed between the back metal and the friction member. As in 2) or (3), it is preferable to use the friction member of the present embodiment as a friction member in which the back metal is integrated.
The back metal is used for improving the mechanical strength of the friction member, and examples of the material thereof include metals such as iron and stainless steel; fiber reinforced plastics such as inorganic fiber reinforced plastics and carbon fiber reinforced plastics. ..
The primer layer and the adhesive layer may be those usually used for friction members such as brake shoes.

The friction material of this embodiment is suitable as a friction material for disc brake pads of automobiles and the like, brake linings and the like. Further, the friction material of the present embodiment can also be used as a friction material for clutch facings, electromagnetic brakes, holding brakes, etc. by subjecting the desired shape to steps such as molding, processing, and pasting.
Further, the friction material of the present embodiment is suitable for a brake pad for a passenger car mounted on a control brake such as a regenerative brake because it can exhibit a stable friction coefficient in a low-speed low-temperature braking range. That is, according to the present invention, it is also possible to provide a passenger car such as an electric vehicle or a hybrid vehicle equipped with a control brake using the friction material of the present embodiment.
Further, since the friction material of the present embodiment is excellent in stability of friction coefficient, wear resistance at high temperature, etc., it is useful as a "upholstery material" for friction members such as disc brake pads and brake linings, and further friction. It can also be molded and used as a "underlaying material" for members. The "upholstery material" is a friction material that serves as a friction surface of the friction member, and the "underlay material" is a friction material that is interposed between the friction material that is the friction surface of the friction member and the back metal. It is a layer for the purpose of improving shear strength and crack resistance in the vicinity of the adhesive portion with the back metal.

[Friction material composition]
The friction material composition according to the present embodiment is a friction material composition that does not contain copper, or even if it contains copper, the content thereof is 0.5% by mass or less as a copper element, and the inorganic fiber (X1) and the above. A friction material containing a shot (X2) of an inorganic fiber (X1), wherein the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fiber (X1) and the shot (X2). It is a composition.
The types of each component contained in the friction material composition of the present embodiment and the method for producing the same are described in the same manner as the friction material of the present embodiment, and all preferred embodiments thereof are also the same. The preferable range of the content of each component in the friction material composition is the same as the preferable range described in the friction material of the present embodiment, but the standard of the content is "100% by mass of the total amount of the friction material composition". And.
Furthermore, the present invention also provides a friction material obtained by molding the friction material composition of the present embodiment. The friction material obtained by molding the friction material composition of the present embodiment is, for example, a method of hot-press molding a preformed body obtained by pre-molding the friction material composition of the present embodiment, a friction material composition of the present embodiment. It can be manufactured by a method such as direct thermal pressure molding and, if necessary, heat treatment to heat-cure the binder. The specific manufacturing method is as described in the manufacturing method of the friction material of the present embodiment and the examples described later.

[vehicle]
The vehicle of this embodiment is a vehicle equipped with the friction member of this embodiment.
Examples of the vehicle of the present embodiment include vehicles in which the friction member of the present embodiment is used for disc brake pads, brake linings, clutch facings, electromagnetic brakes, holding brakes, and the like. Examples of the vehicle include automobiles such as large automobiles, medium-sized automobiles, ordinary automobiles, large special automobiles, small special automobiles, large motorcycles, and ordinary motorcycles.
As the vehicle equipped with the friction member of the present embodiment, passenger vehicles such as electric vehicles and hybrid vehicles equipped with a regenerative braking system are particularly suitable because they can exhibit excellent rust removing property even when braking at a low load.

Hereinafter, the friction material and the friction material composition of the present embodiment will be described in more detail by way of examples, but the present invention is not limited thereto.

<Examples 1 to 4 and Comparative Examples 1 to 2>
[Making disc brake pads]
The materials were blended according to the blending amount (mass%) shown in Table 1 to obtain the friction material compositions of Examples 1 to 4 and Comparative Examples 1 and 2.
Next, this friction material composition is mixed with a Ladyge (registered trademark) mixer (manufactured by Matsubo Co., Ltd., trade name: Ladyge Mixer M20), and this mixture is preformed by a molding press (manufactured by Oji Machinery Co., Ltd.). did. Next, the obtained premolded product was subjected to a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 150 ° C., a molding pressure of 30 MPa, and a molding time of 5 minutes, and a back metal (made of iron) manufactured by Hitachi Automotive Systems Co., Ltd. And heat and pressure molding. Subsequently, the obtained molded product is heat-treated at 200 ° C. for 4 hours, polished using a rotary polishing machine, and scorch-treated at 500 ° C. to perform a disc brake pad (friction material thickness 9 mm, friction material projected area). 52 cm ² ) was obtained.

The details of the various materials used in the examples and comparative examples are as follows.
In the following description and Table 1, when the term "shot content" is simply used, it means the content (mass%) of the shot (X2) in the total amount of the inorganic fibers (X1) and the shot (X2). , "Shot content in friction material" means the content (mass%) of shot (X2) with respect to 100% by mass of the total amount of friction material.

[Binder]
-Resin A: Silicone-modified phenol resin (PR54529 manufactured by Sumitomo Bakelite Co., Ltd.)
-Resin B: Acrylic rubber modified phenol resin (PR55291A manufactured by Sumitomo Bakelite Co., Ltd.)

[Organic filler]
-Cashew dust A: Black cashew dust, average particle size 150-500 μm
-Cashew dust B: Silicone rubber coated cashew dust, average particle size 150-500 μm
-Rubber component (tire rubber powder): Powder TPA manufactured by Carquest Co., Ltd.

[Fiber base material]
-Copper fiber: Average fiber length 3000 μm
-Aramid fiber: Average fiber length 1170 μm
-Mineral fiber A: Biosoluble mineral fiber Shot content: 0.1% by mass
Average fiber length: 230 ± 50 μm
Average fiber diameter: 5.5 μm
Composition: CaO (21.3 wt%), MgO (6.0 _wt%), SiO 2 (42.5 _{wt%), Al 2 O 3 (} 18.0 _wt%), TiO 2 (1.5 wt% ), Fe ₂ O ₃ (7.9% by mass), Na ₂ O (2.0% by mass), K ₂ O (0.5% by mass), P ₂ O ₅ (0.2% by mass), MnO ( 0.1% by mass)
-Mineral fiber B: Biosoluble mineral fiber Shot content: 0.2% by mass
Average fiber length: 650 ± 150 μm
Average fiber diameter: 5.5 μm
Composition: CaO (21.3 wt%), MgO (6.0 _wt%), SiO 2 (42.5 _{wt%), Al 2 O 3 (} 18.0 _wt%), TiO 2 (1.5 wt% ), Fe ₂ O ₃ (7.9% by mass), Na ₂ O (2.0% by mass), K ₂ O (0.5% by mass), P ₂ O ₅ (0.2% by mass), MnO ( 0.1% by mass)
-Mineral fiber C: Biosoluble mineral fiber Shot content: 1% by mass
Average fiber length: 125 ± 25 μm
Average fiber diameter: 5.5 μm
Composition: CaO (21.3 wt%), MgO (6.0 _wt%), SiO 2 (42.5 _{wt%), Al 2 O 3 (} 18.0 _wt%), TiO 2 (1.5 wt% ), Fe ₂ O ₃ (7.9% by mass), Na ₂ O (2.0% by mass), K ₂ O (0.5% by mass), P ₂ O ₅ (0.2% by mass), MnO ( 0.1% by mass)
-Mineral fiber D: Biosoluble mineral fiber Shot content: 5% by mass
Average fiber length: 125 ± 25 μm
Average fiber diameter: 5.5 μm
Composition: CaO (21.3 wt%), MgO (6.0 _wt%), SiO 2 (42.5 _{wt%), Al 2 O 3 (} 18.0 _wt%), TiO 2 (1.5 wt% ), Fe ₂ O ₃ (7.9% by mass), Na ₂ O (2.0% by mass), K ₂ O (0.5% by mass), P ₂ O ₅ (0.2% by mass), MnO ( 0.1% by mass)
-Mineral fiber E: Biosoluble mineral fiber Shot content: 15% by mass
Average fiber length: 125 ± 25 μm
Average fiber diameter: 5.5 μm
Composition: CaO (21.3 wt%), MgO (6.0 _wt%), SiO 2 (42.5 _{wt%), Al 2 O 3 (} 18.0 _wt%), TiO 2 (1.5 wt% ), Fe ₂ O ₃ (7.9% by mass), Na ₂ O (2.0% by mass), K ₂ O (0.5% by mass), P ₂ O ₅ (0.2% by mass), MnO ( 0.1% by mass)

[Inorganic filler]
-Potassium titanate: average particle diameter 2.5 μm, shape: plate-shaped-Wollastonite: average length 300 μm, aspect ratio: 6
Graphite A: Average particle size 300 μm
Graphite B: Average particle size 35-55 μm
-Zirconium oxide: Average particle size 8-9 μm
-Zirconium silicate: average particle diameter 0.4 to 0.6 μm, maximum particle diameter 1.1 μm (A-PAXUF manufactured by Kinsei Matek Co., Ltd.)
-Metallic sulfide A: tin sulfide, average particle size 300-600 μm
-Metal sulfide B: Antimony trisulfide: Average particle size 50 to 150 μm
-Mica: Average particle size 16 to 17 μm
-Calcium hydroxide: Average particle size 50-70 μm
-Barium sulfate: Average particle size 12.5 μm

The disc brake pads obtained in each example were evaluated for various performances using a brake dynamo testing machine (manufactured by Shin Nihon Tokuki Co., Ltd.). In the experiment, a general pin slide type collet type caliper and a ventilated disc rotor manufactured by Kiriu Corporation (FC250 (gray cast iron)) were used, and the evaluation was performed with a moment of inertia of 50 kgm ² .

[Evaluation of friction coefficient stability in the low-speed low-temperature braking range and friction coefficient volatility during one braking]
The test environment was carried out under the conditions of 25 ° C. and 30% humidity, braking at 40 km / h and 0.15 G was performed 1500 times, and the rate of change of the friction coefficient from the 500th braking number to the 1500th braking number was changed to ". Friction coefficient stability in the low-speed low-temperature braking range ”was evaluated based on the following evaluation criteria. The results are shown in Table 1.
(Evaluation criteria)
A: Rate of change within ± 5% B: Rate of change over + 5% + 10% or less, or -10% or more and less than -5% C: Rate of change over 10% or less than -10%

Further, the fluctuation rate of the friction coefficient during one braking at the 1500th braking frequency was defined as the "friction coefficient fluctuation rate during one braking", and the evaluation was made based on the following calculation method and the following evaluation criteria. The results are shown in Table 1.
(Calculation method)
(1) Friction coefficient fluctuation rate during braking (%) = ((Friction coefficient at time X2 − Friction coefficient at time X3) × 100) / (X2-X3)
Braking start time (seconds): X1
Braking end time (seconds): X2
Midpoint (seconds) of actual braking time: X3 = (X1 + X2) / 2
(Evaluation criteria)
A: Volatility 3% or less B: Volatility over 3% 5% or less C: Volatility over 5%

[Evaluation of friction coefficient in normal braking range]
The test environment was carried out under the conditions of 25 ° C. and 30% humidity, and the friction coefficient at 200 km / h and 0.6 G braking in the second efficacy test was measured in accordance with JASO C406 and evaluated based on the following evaluation criteria. The results are shown in Table 1.
(Evaluation criteria)
A: 0.38 or more and less than 0.41 B: 0.35 or more and less than 0.38 C: less than 0.35

[Evaluation of rust removal property]
Under the test conditions of initial braking speed of 60 km / h, 2.0 MPa braking, 1000 braking times, and pre-braking braking temperature of 100 ° C, the degree of rust grinding of the disc rotor that had rusted on the surface in advance was evaluated based on the following criteria. ..
(Evaluation criteria)
A: Rust is completely removed B: Rust is almost completely removed C: Rust is slightly left D: Rust is left

Examples 1 to 4 show the same level of friction coefficient stability during low-speed low-temperature braking as in Comparative Example 1 containing copper, and have better friction coefficient and rust removal property during normal braking than in Comparative Example 1. .. Further, in Examples 1 to 4, the friction coefficient fluctuation rate during one braking, the friction coefficient in the normal braking range, and the friction coefficient in the normal braking range are compared with those of Comparative Example 2 using the mineral fiber A having a shot content of less than 0.2% by mass. It is found that the rust removing property is excellent, the stability of the excellent friction coefficient in the low speed low temperature braking range and the excellent friction coefficient in the normal braking range are compatible, and the rust removing property is excellent.

Compared with conventional products, the friction material, friction material composition, and friction member of the present invention are excellent in rust removing property without using copper, which has a high environmental load. Therefore, of course, for general passenger cars, regenerative brakes, etc. It is suitable for brake pads for passenger cars equipped with control brakes.

Claims (20)

It is a friction material that does not contain copper, or even if it contains copper, whose content is 0.5% by mass or less as a copper element, and contains an inorganic fiber (X1) and a shot (X2) of the inorganic fiber (X1). A friction material in which the content of the shot (X2) is 0.2% by mass or more based on the total amount of the inorganic fibers (X1) and the shot (X2). The friction material according to claim 1, wherein the average fiber length of the inorganic fiber (X1) is 100 to 800 μm. The first or second claim, wherein the total content of the inorganic fibers (X1) and shots (X2) is 1.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of friction material. Friction material. The friction material according to any one of claims 1 to 3, wherein the content of the shot (X2) is 0.2 to 10% by mass based on the total amount of the inorganic fibers (X1) and the shot (X2). The friction material according to any one of claims 1 to 4, wherein the content of Al ₂ O _{3 in} the inorganic fiber (X1) and the shot (X2) is 1 to 35% by mass. Further, according to any one of claims 1 to 5, zirconium silicate having an average particle diameter of 0.4 to 2 μm is contained as an inorganic filler in an amount of 4 to 10% by mass based on 100% by mass of the total amount of the friction material. The friction material described. Further, as the inorganic filler, 15 to 25% by mass of titaniumate which is non-needle-shaped and has an average particle diameter of 2 to 50 μm is contained in an amount of 15 to 25% by mass based on 100% by mass of the total amount of the friction material, according to claims 1 to 6. The friction material according to any one item. The friction material according to any one of claims 1 to 7, further containing 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material. The friction material according to any one of claims 1 to 8, further containing 2 to 10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total amount of the friction material. A friction member in which the friction material according to any one of claims 1 to 9 and a back metal are integrated. A vehicle equipped with the friction member according to claim 10. A friction material composition that does not contain copper, or even if it contains copper, has a content of 0.5% by mass or less as a copper element, and includes an inorganic fiber (X1) and a shot (X2) of the inorganic fiber (X1). The friction material composition contains 0.2% by mass or more of the total amount of the inorganic fibers (X1) and the shots (X2). The friction material composition according to claim 12, wherein the average fiber length of the inorganic fiber (X1) is 100 to 800 μm. According to claim 12 or 13, the total content of the inorganic fibers (X1) and shots (X2) is 1.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of the friction material composition. The friction material composition described. The friction material composition according to any one of claims 12 to 14, wherein the content of the shot (X2) is 0.2 to 10% by mass based on the total amount of the inorganic fibers (X1) and the shot (X2). Stuff. The friction material composition according to any one of claims 12 to 15, wherein the content of Al ₂ O _{3 in} the inorganic fiber (X1) and the shot (X2) is 1 to 35% by mass. Further, as an inorganic filler, any one of claims 12 to 16 contains 4 to 10% by mass of zirconium silicate having an average particle diameter of 0.4 to 2 μm with respect to 100% by mass of the total amount of the friction material composition. The friction material composition according to the item. Further, claims 12 to 12 to claim, wherein, as an inorganic filler, titanate which is non-needle-shaped and has an average particle diameter of 2 to 50 μm is contained in an amount of 15 to 25% by mass based on 100% by mass of the total amount of the friction material composition. The friction material composition according to any one of 17. The friction material composition according to any one of claims 12 to 18, further containing 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material composition. The friction material composition according to any one of claims 12 to 19, further containing 2 to 10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total amount of the friction material composition.