JP2002275452A - Non-asbestos-based friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a non-asbestos-based friction material undergoing little wear during high-speed braking, excellent in heat resistance, having stable braking effectiveness and good strength and generating little undesirable brake noise and suitable especially as brake lining for drum brakes. SOLUTION: This non-asbestos-based friction material is obtained by molding and curing a composition comprising a fibrous base other than asbestos, a binder and a filler as main components. The non-asbestos-based friction material is characterized by including 1-15 vol.% inorganic fibers having <4.5 Moh's hardness as a part of the fibrous base and including 0.5-15 vol.% cashew dust as one filler, based on the overall friction material composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-asbestos-based friction material which satisfies the required performance of both a service brake (for regular use) and a parking brake (for parking).

[0002]

2. Description of the Related Art
Friction materials for drum brakes used for braking automobiles, heavy trucks, railway vehicles, and various industrial machines have excellent braking effect (high friction coefficient), high heat resistance, and squealing. Various characteristics are required, for example, such that the friction material is not cracked when the friction material is bolted and riveted to the brake shoe.

In this case, since the brake shoe and the brake lining are arranged so as to enter the inside of the drum, the heat generated during braking is less likely to be radiated to the outside, and the friction of the shoe and the lining surface is increased. The material is burned by the heat, and the so-called fade phenomenon in which the braking effect is extremely reduced is apt to occur. Therefore, improvement of heat resistance is strongly desired.

In the case of friction materials for automobiles, in particular, brake linings, cashew dust is indispensable and useful for the purpose of improving wear resistance and effectiveness during normal use, or improving familiarity at the beginning of use. One of the raw materials. For example, Japanese Unexamined Patent Publication (Kokai) No. 63-62926 contains 7% by weight (about 16 to 18% by volume) of cashew dust in the entire friction material. In Japanese Patent Application Laid-Open No. 2-269149, 20% by volume of cashew dust is used.

However, when cashew dust is used in a large amount to improve the effect and abrasion resistance as described above,
There is a problem that friction at high temperature increases due to a decrease in heat resistance, and a film is easily formed on a surface facing the friction, so that abnormal noise is easily generated.

On the other hand, if a large amount of hard fiber such as glass fiber is used to improve the strength and toughness, the effect is improved.
There is a problem that the opponent's aggressiveness becomes a problem, and squealing and unusual noise are likely to occur.

On the other hand, in recent years, the demands for the feeling during braking, especially for the generation of brake squeal and abnormal noise, have become more and more severe. What has little sound generation is desired.

The present invention has been made in view of the above circumstances, and has a small amount of wear during high-speed braking, has excellent heat resistance, can ensure stable braking effectiveness and sufficient strength, and has a swing at the end of braking. No abnormal noise caused by return, and less noise caused by rocking of the vehicle body at the time of getting off and riding after parking brake is applied.
It is an object of the present invention to provide a high-performance non-asbestos-based friction material that satisfies both performance requirements of a service brake (for regular use) and a parking brake (for parking).

[0009]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to achieve the above object, the present inventor has reduced the amount of cashew dust which is one of the organic fillers, (I) using a fixed amount of soft inorganic fibers, or (ii) using a combination of hard inorganic fibers and soft inorganic fibers, while maintaining strength and a coefficient of friction, can reduce squeal and low-frequency noise. It was found that it was effective in reducing the occurrence.

That is, a fiber base material other than asbestos, a binder,
Forming a non-asbestos-based friction material composition containing a filler as a main component,
The cured non-asbestos-based friction material contains (i) an inorganic fiber having a Mohs hardness of less than 4.5 as a part of the fiber base material in an amount of 1 to 15% by volume of the whole friction material composition, and a filler material. As one, cashew dust is added to the friction material composition in an amount of 0.1%.
By containing 5 to 15% by volume, since the soft inorganic fiber is used, the organic film on the friction facing side can be removed without causing the aggressiveness of the mating surface and the deterioration of the squeal.

[0011] Further, a fiber base material other than asbestos, a binder,
Forming a non-asbestos-based friction material composition containing a filler as a main component,
A cured non-asbestos-based friction material, (ii) an inorganic fiber having a Mohs hardness of less than 4.5 as a part of the fiber base material;
By using a combination of inorganic fibers having a Mohs hardness of 4.5 or more and including cashew dust as one of the fillers in an amount of 0.5 to 15% by volume of the entire friction material composition, two or more Mohs hardnesses can be obtained. Since inorganic fibers of different types are combined, the characteristics of each inorganic fiber can be effectively brought out even with a small blending amount, and the stability of the effect level can be enhanced.

In any of the above (i) and (ii), the amount of wear at the time of high-speed braking is small, heat resistance is excellent, stable braking effectiveness and sufficient strength are secured, and braking is completed. Both the service brake (for regular use) and the parking brake (for parking), without generating abnormal noise due to the swing back of the vehicle, and generating less noise due to the swing of the vehicle body when getting off and riding after the parking brake is activated. It has been found that a high-performance non-asbestos-based friction material satisfying the required performance can be obtained, and the present invention has been accomplished.

That is, the present invention provides the following non-asbestos-based friction material. <Claim 1>: A non-asbestos-based friction material obtained by molding and curing a non-asbestos-based friction material composition containing a fiber base material other than asbestos, a binder, and a filler as main components. As a part of the material, an inorganic fiber having a Mohs hardness of less than 4.5 is contained in an amount of 1 to 15% by volume of the entire friction material composition, and cashew dust is used as one of the fillers in an amount of 0.5 to 15% of the entire friction material composition. A non-asbestos-based friction material characterized by containing by volume. <Claim 2> A non-asbestos-based friction material obtained by molding and curing a non-asbestos-based friction material composition mainly containing a fiber base material excluding asbestos, a binder, and a filler. And a combination of an inorganic fiber having a Mohs hardness of less than 4.5 and an inorganic fiber having a Mohs hardness of 4.5 or more. A non-asbestos-based friction material containing 0.5 to 15% by volume. <Claim 3>: The non-woven fabric according to claim 2, wherein the mixing ratio B / (A + B) of the inorganic fiber B having a Mohs hardness of 4.5 or more with respect to the inorganic fiber A having a Mohs hardness of less than 4.5 is 80% by volume or less. Asbestos-based friction material. <Claim 4>: The inorganic fiber having a Mohs hardness of less than 4.5 is one or more selected from potassium titanate fiber, magnesium carbonate fiber, magnesium sulfate fiber, and calcium carbonate fiber. 4. The non-asbestos-based friction material according to 2 or 3. <Claim 5>: The inorganic fiber having a Mohs hardness of 4.5 or more is one or two or more selected from glass fiber, rock wool, ceramic fiber, and metal fiber.
5. The non-asbestos-based friction material according to 3 or 4. <Claim 6>: The inorganic fiber has a fiber length of 50-4.
The non-asbestos-based friction material according to any one of claims 1 to 5, wherein the non-asbestos-based friction material has a fiber diameter of 5 to 60 µm.

Hereinafter, the present invention will be described in more detail. The non-asbestos-based friction material of the present invention is obtained by molding and curing a non-asbestos-based friction material composition containing a fiber base material other than asbestos, a binder, and a filler as main components. As a part of the material, an inorganic fiber having a Mohs hardness of less than 4.5 is contained in an amount of 1 to 15% by volume of the entire friction material composition, and cashew dust is used as one of the fillers in an amount of 0.5 to 15% of the entire friction material composition. (Ii) a combination of an inorganic fiber having a Mohs hardness of less than 4.5 and an inorganic fiber having a Mohs hardness of 4.5 or more as a part of the fiber base material; Cashew dust as one of the 0.5 to 0.5% of the entire friction material composition
It is characterized by containing 15% by volume.

Here, (i) as a part of the fiber base material, 1 to 15% by volume, particularly 3 to 10% by volume, of a soft inorganic fiber having a Mohs hardness of less than 4.5 is added to the friction material composition. At the same time, cashew dust is added as one of the fillers in an amount of 0.5 to 15% by volume of the entire friction material composition.
It is preferable to add 10 to 10% by volume.

If the amount of the soft inorganic fiber having a Mohs hardness of less than 4.5 and the amount of the cashew dust are out of the above ranges, insufficient effect, insufficient heat resistance, increased wear, generation of abnormal noise, or squealing will occur. Will cause problems such as the occurrence of
The objects and effects of the present invention cannot be achieved.

Examples of the soft inorganic fiber having a Mohs hardness of less than 4.5 include potassium titanate fiber, magnesium carbonate fiber, magnesium sulfate fiber, calcium carbonate fiber and the like. One of these can be used alone or two or more can be used. They can be used in combination. Of these, potassium titanate fibers are preferred. In this case, the inorganic fiber has a fiber length of 50 to 4000 μm, preferably 80 to 350 μm.
m, and the fiber diameter is preferably 5 to 60 μm.

As the cashew dust, those usually used for friction materials can be used.
500 μm, preferably 200-500 μm, with a tar content of 6-12% by mass is preferred.

Further, the non-asbestos-based friction material of the present invention comprises (i)
i) an inorganic fiber having a Mohs hardness of less than 4.5 as a part of the fiber base material, and a Mohs hardness of 4.5 or more, preferably 4.5.
To 8, and more preferably 6 to 8 inorganic fibers, and at the same time, add cashew dust as one of the fillers in an amount of 0.5 to 15% by volume of the entire friction material composition.
It is preferable to add 10 to 10% by volume.

In this case, the ratio B / (A + B) of the inorganic fiber having a Mohs hardness of 4.5 or more to the inorganic fiber having a Mohs hardness of less than 4.5 is 80% by volume or less, and particularly, A: B
It is preferable to mix at a volume ratio of = 1: 2 to 30: 1.

The total amount of the inorganic fibers having a Mohs hardness of less than 4.5 and the inorganic fibers having a Mohs hardness of 4.5 or more is as follows:
It is 1 to 25% by volume, preferably 3 to 20% by volume, especially 5 to 15% by volume based on the whole friction material composition.

As the soft inorganic fibers having a Mohs hardness of less than 4.5 and cashew dust, the same materials as described above can be used. Examples of the inorganic fibers having a Mohs hardness of 4.5 or more include glass fibers, rock wool, ceramic fibers, and metal fibers such as iron, copper, brass, bronze, and aluminum. The above can be used in combination. In this case, the inorganic fiber has a fiber length of 50 to 4000 μm, preferably 2 to
000-3000 μm, and the fiber diameter is 5-60 μm
m is preferable.

As the fiber base material other than the above-mentioned inorganic fibers, nylon, polyester, and the like usually used for friction materials are used.
Organic fibers such as rayon, phenol fibers, and aramid fibers can be used, and the total amount of the fiber base material other than the inorganic fibers is 0 to 15% by volume, preferably 2 to 12% by volume based on the whole friction material composition. %.

As the binder, known binders usually used for friction materials can be used. For example, phenol resins, melamine resins, epoxy resins, epoxy-modified phenol resins, oil-modified phenol resins, alkylbenzene-modified phenol resins, cashews Various modified phenol resins such as a modified phenol resin, NBR and the like can be mentioned, and one of these can be used alone or in combination of two or more.

The amount of the binder is 10 to 25% by volume, preferably 12 to 20% by volume, based on the whole friction material composition.
It is.

Examples of the organic filler other than cashew dust include various rubber powders such as rubber dust and melamine dust, tire powder, and the like. One of these powders may be used alone or in combination of two or more. it can.

The total amount of the organic filler is 5 to 35% by volume, preferably 10 to 2% by volume based on the whole friction material composition.
5% by volume.

Examples of the inorganic filler include molybdenum disulfide, antimony trisulfide, calcium carbonate, barium sulfate, magnesium oxide, graphite, calcium hydroxide, calcium fluoride, talc, molybdenum trioxide, antimony trioxide, and zirconium silicate. , Iron oxide, mica, iron sulfide,
Zirconium oxide, metal powder, quartz, silicon oxide, alumina, chromium oxide, vermiculite, and the like,
One of these can be used alone or two or more can be used in combination.

The amount of the inorganic filler is 20 to 65% by volume, preferably 35 to 55% by volume based on the whole friction material composition.
% By volume.

In the method for producing a non-asbestos-based friction material according to the present invention, a predetermined amount of the fiber base material, the binder and the filler is measured by using a mixer such as a Henschel mixer, a Loedige mixer or an Erich mixer. The mixture is uniformly mixed, and the mixture is pre-formed in a molding die.
200 ° C., 2 at a molding pressure of 100 to 1000 / cm ²
Molded for 10 to 10 minutes, and the obtained molded article is 140 to 250 ° C.
At a temperature of 2 to 48 hours (post-curing) and, if necessary, spray coating, baking and polishing to obtain a finished product.

The non-asbestos-based friction material of the present invention can be used for disc pads, brake shoes, brake linings, etc. of automobiles, heavy trucks, railway vehicles, various industrial machines and the like. Materials are service brakes (for regular use) and parking brakes (for parking)
Meet both performances. That is, for traveling, it has good effect, friction resistance, heat resistance, squealing performance, strength, low-frequency noise, and opponent's aggressiveness. Good. Therefore, the drum brake at the rear of a small car is often used for both traveling and parking, and is effective for such use.

[0032]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 11, Comparative Examples 1 to 3
A friction material composition having the composition shown in No. 2 was blended, and the mixture was uniformly mixed using a Loedige mixer.
Preforming was performed by pressing at g / cm ² for 10 minutes. This preform is molded at a molding temperature of 160 ° C. and a molding pressure of 250 kg / cm.
Molding for any time under the conditions of ²
Heat treatment (post-curing) was performed for a time, and brake linings for drum brakes of Examples 1 to 11 and Comparative Examples 1 to 3 were prepared.

With respect to the obtained brake linings of Examples 1 to 11 and Comparative Examples 1 to 3, a friction coefficient, a squeal, an abnormal noise generation test, and a wear test were performed by the following evaluation methods. The results are shown in Tables 1 and 2.

<Friction Coefficient> According to JASO C406 < Squealing and abnormal noise generation test (according to JASO C402)> Through actual vehicle tests, the frequency of occurrence of noise and the frequency of occurrence of abnormal noise during braking were evaluated according to the following criteria. <Evaluation Criteria> A: Occurrence rate 1% or less O: Occurrence rate 3% or less C: Occurrence rate less than 10% X: Occurrence rate 10% or more

<Wear test (based on JASO C406)>
Under the test conditions of an initial braking speed of 50 km / h, a braking deceleration of 0.15 g, a braking frequency of 1,000 times, and a brake temperature before braking of 150 ° C., the degree of wear of the facing surface (drum) was evaluated based on the following criteria. ◎: Very small (less than 100 μm) ○: Small (100 to 200 μm) △: Slightly large (200 to 300 μm) ×: Many (more than 300 μm)

[0037]

[Table 1]

[0038]

[Table 2] * Inorganic fiber Potassium titanate fiber (Mohs hardness 4, fiber length 150μ)
m, fiber diameter 30 μm) Glass fiber (Mohs hardness 6, fiber length 3000 μm, fiber diameter 10 μm) Rock wool (Mohs hardness 6, fiber length 250 μm, fiber diameter 5 μm) * Other organic fillers: tire rubber, rubber powder (volume ratio) 1: 1) * Inorganic filler: slaked lime 3% by volume, calcium carbonate balance

[0039]

The non-asbestos-based friction material of the present invention has the following excellent effects. (1) The occurrence of unusual return noise at the end of braking is significantly reduced. (2) The generation of abnormal noise due to the swing was significantly reduced. (3) Heat resistance was improved. (4) The effect is stabilized. (5) Friction face-to-face aggression was reduced.

Claims (6)

[Claims] 1. A non-asbestos-based friction material obtained by molding and curing a non-asbestos-based friction material composition mainly containing a fiber base material excluding asbestos, a binder, and a filler. Of the friction material composition as a part of the friction material composition, and cashew dust as one of the fillers is 0.5 to 15 volume% of the whole friction material composition. % Non-asbestos-based friction material. 2. A non-asbestos-based friction material obtained by molding and curing a non-asbestos-based friction material composition containing a fiber base material excluding asbestos, a binder, and a filler as main components. A part of the inorganic fiber having a Mohs hardness of less than 4.5 and an inorganic fiber having a Mohs hardness of 4.5 or more are used in combination, and cashew dust is used as one of the fillers in the friction material composition. A non-asbestos-based friction material containing 5 to 15% by volume. 3. The non-asbestos according to claim 2, wherein the mixing ratio B / (A + B) of the inorganic fiber B having a Mohs hardness of 4.5 or more with respect to the inorganic fiber A having a Mohs hardness of less than 4.5 is 80% by volume or less. Friction material. 4. The inorganic fiber having a Mohs hardness of less than 4.5 is one or more selected from potassium titanate fiber, magnesium carbonate fiber, magnesium sulfate fiber and calcium carbonate fiber. Or the non-asbestos-based friction material according to 3. 5. The inorganic fiber having a Mohs hardness of 4.5 or more is one or more selected from glass fiber, rock wool, ceramic fiber and metal fiber.
5. The non-asbestos-based friction material according to 3 or 4. 6. The inorganic fiber has a fiber length of 50-4.
The non-asbestos-based friction material according to any one of claims 1 to 5, wherein the non-asbestos-based friction material has a fiber diameter of 5 to 60 µm.