JP2867661B2 - Friction material and method of manufacturing the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material and a method of manufacturing the same, and more particularly, to a friction material used for a disc brake or a drum brake of a truck or a passenger car and a method of manufacturing the same.

[Prior Art] Conventionally, as a friction material generally used for a brake of a truck, a passenger car, or the like, there has been a material using asbestos as a base material. However, friction materials that do not use asbestos have been demanded due to safety and health problems. Conventionally known friction materials that do not use asbestos include, for example, JP-A-54-34349.
And JP-B-64-4541, JP-B-57-37187, and JP-B-59-4459. Hereinafter, description will be made in order.

First, Japanese Patent Application Laid-Open No. 54-34349 discloses a friction material formed by molding a mixture of a steel fiber or a glass fiber and an inorganic reinforcing material other than asbestos with a phenol formaldehyde resin. One of the reinforcing materials is mica. Are listed.

Japanese Patent Publication No. 64-4541 discloses the use of mica as one of fillers for the purpose of changing physical properties and reducing costs in a friction material based on glass fiber and molten liquid crystalline polyester. .

In JP-B 57-37187, JP-fibrous materials 0-5 wt%, mica 20-60 wt%, the phenol resin 5 to 30 wt%, BaSO ₄ 5-30 wt%, cashew dust 5 to 15 wt%, metal A friction material consisting of 5 to 30% by weight of granules is disclosed, showing that mica can replace asbestos as a base material.

[Problems to be Solved by the Invention] As described above, a number of friction materials that do not use asbestos have been proposed. However, at the same cost as asbestos, properties such as flexibility, strength, wear resistance, There was no alternative substrate having softness, and as a result, as described above, a plurality of fibers were used in combination to replace asbestos. However, most of the substitute fibers are thick and rigid, and do not have the property of wrapping other powders like asbestos,
Separated by handling after mixing asbestos with other powders,
Segregation may occur. When separation and segregation occur, there is a problem that a homogeneous mixture cannot be obtained.

In addition, scale-like powders such as mica, which are effective as substitutes for asbestos, are light in weight, so that they can easily fly during the mixing operation and it is very difficult to form a homogeneous mixture. Furthermore, since mica and the like have poor wettability with the resin used as a binder and are hard to be sufficiently bonded, the strength of the friction material is reduced, and cracks and gas swelling are likely to occur during molding and curing. there were. If the amount of resin in the binder is increased in order to prevent this, the heat resistance of the friction material is deteriorated, and gas swelling is rather increased. That is, conventionally, mica and the like that are effective as substitutes for asbestos have a problem that it is difficult to make the quality uniform at the time of production.

On the other hand, among the characteristics that have conventionally been required for a friction material of a brake, an unsolved problem is a squeal during braking. In general, as a friction material which is unlikely to cause squealing during braking, a friction material containing a large amount of a solid lubricant such as graphite is known. However, when graphite or the like is frequently used, there is a disadvantage that the friction coefficient μ decreases and the braking force decreases. In addition, a material to which a large amount of an organic filler such as rubber or cashew dust is added is also effective in preventing squeal during braking. These are disclosed, for example, in JP-B-59-4459. However, this friction material also has a drawback that the friction coefficient μ decreases at high speed and high temperature, resulting in an increase in wear. That is, it has been difficult to effectively prevent squeal during braking without lowering the braking force, which is a conventional problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to solve the problem of the sanitary environment and to provide a fatal friction coefficient as a friction material. Another object of the present invention is to provide a friction material capable of effectively preventing squeal during braking while minimizing a decrease in braking force due to a decrease in the brake force.

The object of the invention described in claim 2 is to solve the problem of sanitary environment, to achieve uniform quality at the time of manufacturing, and to reduce the frictional coefficient as a fatal material as a friction material due to a reduction in the frictional force. Another object of the present invention is to provide a friction material that can effectively prevent squeal at the time of braking while minimizing the reduction of the friction.

The third object of the present invention is to solve the problem of the sanitary environment, and to more effectively prevent the squeal during braking while preventing a reduction in the braking force due to a reduction in the friction coefficient that is fatal as a friction material to some extent. Another object of the present invention is to provide a friction material that can be prevented.

An object of the invention described in claim 4 is to solve the problem of the sanitary environment and to make the quality at the time of manufacture uniform.

[Means for Solving the Problems] According to the first aspect of the present invention, the powder for adjusting friction and wear includes an inorganic substance having a plane network crystal structure, and the direction of delamination of the inorganic substance between the friction material and the friction material is the same. It is characterized by being distributed so as to be aligned in a direction substantially along the surface.

The invention according to the second aspect is characterized in that the inorganic substance having a planar network crystal structure to be dispersed is at least partially granulated with a binder, and the inorganic substance granulated by both or one of pressure and heat during molding. It is characterized by including a composite material that is granulated so that the granulated shape is deformed flat.

According to a third aspect of the present invention, the inorganic substance having a plane network crystal structure is one or more of mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, limestone, kaolin, chlorite, sericite, iron hydroxide, and montmorillonite. It is characterized by including two or more materials or those obtained by adding graphite.

The invention according to a fourth aspect provides a step of granulating at least a part of a granular material made of an inorganic substance having a plane network crystal structure with a binder, and using the pressure and / or heat to granulate the granular material. A step of deforming the granulated shape of the granular material to be flat by molding, and a step of forming the granulated shape to a predetermined thickness by polishing a friction material containing the granular material whose granulated shape has been flattened by molding. including.

[Action] In the invention according to the first aspect, the granular material contains an inorganic substance having a plane network crystal structure, and is dispersed such that the direction of delamination of the crystal of the inorganic substance is substantially aligned with the direction along the friction surface of the friction material. As a result, the granular material is liable to cause minute peeling on the friction surface.

In the invention according to the second aspect, at least a part of the dispersed inorganic material having a planar network crystal structure is granulated with a binder, and the inorganic material granulated by both or one of pressure and heat during molding. Since the friction material contains a composite material that is granulated so that the grain shape is deformed flat, a mass of inorganic substances having a plane network crystal structure is formed, and the production environment of the friction material is made uniform, Inorganic substances having a plane network crystal structure are arranged such that the direction of delamination thereof is along the direction of friction of the friction material, so that minute peeling is likely to occur on the friction surface.

According to the third aspect of the present invention, the inorganic substance having a planar network crystal structure includes one of mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, limestone, kaolin, chlorite, sericite, iron hydroxide, and montmorillonite. Alternatively, since two or more materials or those obtained by adding graphite thereto are included, minute peeling is more likely to occur on the friction surface of the friction material.

In the invention according to the fourth aspect, at least a part of the granular material made of an inorganic material having a plane network crystal structure is granulated by a binder, and the granulated granular material uses both or one of pressure and heat. Since the granulated shape of the granular material is flattened by being formed by the compacting, the agglomeration of the inorganic substance having the plane network crystal structure is formed by the granulation, and the production environment of the friction material is made uniform.

[Examples of the Invention] Table 1 shown below is a table showing the material mixing ratio of a disc brake pad according to an example of the present invention. Second
The table shows the 18 combinations (A, B, C1, C1) of the graphite particle size, mica particle size, graphite and mica granulation method, binder type and amount, and solvent type shown in Table 1. C2,
D1, D2, E, F1 to F7, G1, G2, H, I).

 It is to provide a friction material which can be prevented.

Here, A is a comparative example, which contains neither mica nor graphite, and is not granulated. The molding conditions of the disc brake pad shown in Table 1 are as follows: press temperature 160 ° C,
Pressing time is 10 minutes. Pressing pressure is the porosity of the finished pad.
Set the value to 10%. After thermoforming, in a furnace at 220 ° C, 10
After completion of curing by heating for a period of time, polishing is performed to a predetermined thickness.

Referring to Table 2, the graphite used here is a natural scale-like product made of Sri Lanka, and mica is a phlogopite of canadic acid, both of which are inorganic substances having a plane network crystal structure. Here, the inorganic substance having a planar reticulated crystal structure, SiO ₄ group, the polymerization the acid groups of SiO _4, and copolymerized acid groups of SiO ₄ and AlO ₄ as a skeleton, to which the form of cations bound The silicate has a crystal structure developed in a secondary planar network. These are described in detail in, for example, pages 11 to 18 of the Ceramics Engineering Handbook edited by the Ceramics Association of Japan. In these substances, the crystals develop into a planar shape and are layered, and these layers are bonded by a weak van der Waals force, causing a slip phenomenon between the layers. Examples of the inorganic substance having a planar network crystal structure include mica and graphite, as well as talc, vermiculite, aluminum hydroxide, magnesium hydroxide, limestone, kaolin, chlorite, sericite, iron hydroxide, and montmorillonite. Mica has three types of particle diameters of 70 μm, 100 μm, and 500 μm, and graphite has three types of particle diameters of 60 μm, 100 μm, and 270 μm. Granulation methods include a method using a rotary pan-type granulator, a method using a twin-screw extruder using a slit with an inner diameter of 1 mm, and a method in which a kneaded material is sandwiched between two release types on a 0.5 mm sheet. And roll compression. In Table 2, F-3 and F-6 are granulated by a method using a twin screw extruder, and F-4 is granulated by a method of compressing with a roll. Note that F-6 is pulverized after heating at 200 ° C. for 5 hours, but all others are dried at a boiling point of the solvent or lower. Further, a granulated product having an average particle size of 300 μm can be obtained by classification and pulverization. When the size of the granulated material on the polished surface of the disc brake pad to which the granulated material was added was measured, it was stretched by at least 10% or more except for F-6, and C-1, D, E, H
And I were stretched 30%.

FIG. 1 is a graph showing the squeal occurrence rates of the brake pads A to I created based on Table 2. The measurement conditions for the squealing rate were as follows: A to H brake pads were attached to a 2000cc small car, the vehicle speed was 40km / h, and the pad temperature before braking was 20.
The temperature was changed from 40 ° C to 260 ° C to 60 ° C for each cycle, and this was defined as one cycle.
The frequency of occurrence of brake squeal was measured in 10 steps of 0.05 g from 05 to 0.5 g. Here, a total of 10 cycles, 2
The frequency of brake squeal at 200 stops was measured.

FIG. 2 shows, in addition to F-1 shown in FIG.
For F-3, F-4, F-5, F-6, and F-7, which are the same as F-1 only in the volume percentage of mica and graphite, the squealing rates measured under the same measurement conditions as in FIG. 1 are shown. It is a graph.

FIG. 3 shows a test using a dynamometer assuming a small 2,000 cc passenger car using a disk having a moment of inertia of 6.0 kg · m · S ² , a thickness of 22 mm, and an outer diameter of 250 mm in accordance with the test standard of JAS06914. 4 is a graph showing a friction coefficient μ under a condition of a second effect of 130 km / h and a deceleration of 0.6 g.

The experimental results will be described with reference to FIG. 1, FIG. 2, and FIG. First, referring to FIGS. 1 and 3,
It can be seen that B, which uses a small amount of mica, has a high squealing rate. In contrast, I, which uses a large amount of mica, has a lower squealing rate than B. D, F using mica and graphite together
It can be seen that the squealing rate is lower than I and the friction coefficient μ is larger than I. Next, referring to FIG. 2, it can be seen that the squealing rate of F-6 thermoset using a thermosetting resin is the highest, and that of F-3 not thermoset is lower. Furthermore, the squealing rate of F-4 manufactured using the granulation method of compressing using a roll is lower than that of F-3. Further, F-7 having a small particle size of mica and graphite is F-
It can be seen that the squealing rate is as low as that of No. 3.

The following is a discussion based on the above experimental results. When mica is used in the same volume, a smaller particle size is more effective in preventing squeal than a larger particle size. In addition, it is more effective to prevent squeal from scattering mica lump having a smaller particle size than dispersing mica uniformly in the friction material. However, in order to form such a lump, in a composite material which has been cured and then pulverized using a thermosetting resin as a binder according to a conventionally proposed method, the prevention of squealing hardens. This is because, in the friction material, plate- and scale-like mica are randomly arranged vertically, horizontally and diagonally, and in order to improve the effect of preventing squeal, the mica is almost parallel to the friction surface. Need to be The reason that mica is arranged in parallel to the friction surface and that the smaller the particle size is, the more effective it is to prevent squealing is because the frictional resistance due to the contact between the brake pad and the disc during friction causes micro exfoliation of mica, This is because the stick-slip phenomenon is suppressed.

Further, the particle size of graphite and mica is preferably 300 μm or more, more preferably 200 μm or more, and more preferably 1 μm or more.
50 μm or more is preferred. The stretched particle size of the mica or mica and graphite on the friction surface preferably contains 500 μm or more.

The binder is molasses, sodium alginate, latex,
Adhesives such as polyvinyl alcohol, celluloses, gelatin, pitch, and lignin, thermoplastic resins, and thermosetting resins in a state where the curing reaction is not completed can be used. These binders may be used alone, but as a method for facilitating granulation of mica / graphite having poor wettability, it is preferable to use an adhesive and a resin together. In that case, a thermoplastic resin is preferable in that the fluidity of the granulated material at the time of molding is increased. The binder is not limited to an organic substance, but may be an inorganic substance such as sodium silicate and sodium polyphosphate.

The amount of binder used is 0.02 per granulated material 1 by volume ratio.
1.0 to 1.0, more preferably 0.04 to 0.5, and more preferably 0.
06-0.35 is desirable. If the binder is insufficient, the granulation is insufficient and dust is likely to be generated. If the binder is frequently used, the friction performance is deteriorated when used as a friction material.

The granulation method is as follows: Banbury mixer, rubber roll for kneading,
Using a pressure kneader or an extruder, a lump is obtained by one or both of heat and pressure. Thereafter, if necessary, the material is dried and pulverized. In order to increase the fluidity during molding, a rotary pan type granulator capable of obtaining granules having a small apparent density without applying pressure is preferable. Depending on the particle size of mica and graphite, a spray fluidized-bed granulator may be used. Also, exceptionally, the method of compressing into a thin sheet with a roll is effective in preventing squeal because mica and graphite are arranged in one direction.

Other than mica, examples of inorganic substances having a planar network crystal structure include talc, vermiculite, aluminum hydroxide, magnesium hydroxide, rubite, kaolin, chlorite, sericite, iron hydroxide, montmorillonite, and the like. The same effect can be obtained even if a granulated product is produced.

Table 3 below is a table showing the material mixing ratio of a disc brake pad using an inorganic material having a planar network crystal structure other than mica according to the second embodiment of the present invention.
Table 4 is a table showing a squeal occurrence rate when a squeal test is performed on the disk brake pads shown in Table 3 under the same measurement conditions as those shown in FIG.

FIG. 4 is a process diagram for explaining a method of manufacturing the disc brake pad shown in Table 3. With reference to FIG. 4, a method of manufacturing the disc brake pad shown in Table 3 will be described first. First, as shown in step 101, the granulated raw materials shown in Table 3 are granulated using a rotary pan granulator. As a binder, sodium alginate and polyvinyl alcohol are used, and as a diluting solvent,
Use water. Then, as shown in step 102, the third
The molding conditions of the disc brake pad shown in the table were the same as those in Table 1, at a press temperature of 160 ° C., a press time of 10 minutes, and a press pressure set to a value at which the porosity of the finished pad was 10%. Heat in oven for 10 hours to complete curing. After that, as shown in step 103, polishing is performed to a predetermined thickness.

Referring to Tables 3 and 4, talc, aluminum hydroxide, vermiculite, magnesium hydroxide, fluorite, kaolin, chlorite, sericite, iron hydroxide, and montmorillonite have the same brake pad squealing rate as mica. It has the effect of reducing. The addition amount of these is preferably 1/2 or less, more preferably 以下 or less, of the total planar network crystal structure. The graphite is desirably at most 2.0 vol, preferably at most 1.5 vol, more preferably at most 1.0 vol with respect to 1.0 vol of the planar network crystal structure. Increasing the amount of graphite is effective in preventing squealing, but causes a decrease in the friction coefficient μ.

As described above, in the present embodiment, at least one of mica, vermiculite, graphite, talc, magnesium hydroxide, rubite, kaolin, chlorite, sericite, iron hydroxide, and montmorillonite is granulated with an organic / inorganic binder. To form a lump, which is used as a part of the friction material raw material. The binder for granulation is a material that can be softened and flowed by heat or both heat and pressure when the friction material is molded, and the shape of the granulated material after the molding is flattened unlike the original form. Is what it is. By using such a binder, a lump of inorganic substances having a plane network crystal structure such as mica is dispersed on the surface of the friction material and is arranged along the friction direction, and as a result, fine peeling is likely to occur. It is effective for reducing brake squeal. In addition, as a result of searching for materials that are effective in reducing brake squeal, mica, vermiculite, aluminum hydroxide, and magnesium hydroxide, which are inorganic substances with a planar network crystal structure, are effective. The effect can be improved. The amount of granules to be added is
It may be in the range of 1 to 35% by volume of the whole, preferably 3 to 30% by volume, more preferably 5 to 25% by volume. Here, if the added amount of the granulated material is small, the effect of preventing squeal is small, and if the added amount is too large, the friction coefficient μ at high speed is reduced. Of course, mica, graphite, or the like that has not been granulated may be used in combination with the granulated material. In the present embodiment, an inorganic material having a plane network crystal structure is used. However, the present invention is not limited to this, and may have a crystal structure similar to the plane network crystal structure.

In addition, in the method for manufacturing a disc brake pad shown in FIG. 4, an inorganic substance having a plane network crystal structure such as mica is granulated by a binder, and then molded without curing, and the granulated shape such as mica is flattened. Therefore, minute peeling easily occurs on the friction surface of the disc brake pad. As a result, brake squeal can be reduced. In addition, since agglomerates such as mica are formed by granulation, the weight becomes heavy, and inconveniences in production such as mica soaring which have been a problem in the past can be effectively improved. Furthermore, since the number of particles is reduced by granulation, it is also effective in reducing the friction material strength due to separation, segregation and poor wettability between the binder and mica, which were problems when using conventional fibers as the base material. Can be prevented.

[Effects of the Invention] As described above, according to the first aspect of the present invention, it is possible to solve the problem of the sanitary environment and to minimize the decrease in the braking force due to the decrease in the friction coefficient that is fatal as a friction material. However, it has become possible to provide a friction material that can effectively prevent squeal during braking.

According to the second aspect of the present invention, it is possible to solve the problem of the sanitary environment, to achieve uniform quality at the time of manufacturing, and to decrease the braking force due to a decrease in the friction coefficient that is fatal as a friction material. Thus, it is possible to provide a friction material that can effectively prevent squeal during braking while minimizing noise.

According to the third aspect of the invention, it is possible to solve the problem of the sanitary environment and to more effectively prevent the squeal at the time of braking while preventing a reduction in the braking force due to a reduction in the friction coefficient which is fatal as a friction material. It is possible to provide a friction material that can be used.

According to the fourth aspect of the present invention, it is possible to provide a method of manufacturing a friction material capable of solving the problem of the sanitary environment and achieving uniform quality at the time of manufacturing.

[Brief description of the drawings]

FIG. 1 is a graph showing the squealing rates of brake pads A to I created based on Table 2, and FIG. 2 is a graph showing F-1 and mica in addition to F-1 shown in FIG. F-3, F-4, F-5, F-6, F-7 which are the same only by volume% of graphite
FIG. 3 is a graph showing the squealing rate measured under the same measurement conditions as in FIG. 1, FIG. 3 is a graph showing a friction coefficient μ when tested according to the test standard of JAS06914 by a dynamometer assuming a 2000 cc compact passenger car, FIG. 4 shows the third
It is a process figure for explaining the manufacturing method of the disc brake pad shown in the table. In the respective drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuya Kishimoto 1-1-1, Koyokita, Itami-shi, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (56) References JP-A-64-40730 (JP, A JP-A-3-181628 (JP, A) JP-A-4-139290 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16D 69/02 C09K 3/14 520 C08J 5 /14

Claims (4)

(57) [Claims] 1. A friction material made of a thermosetting resin containing a fibrous material serving as a base material and particles for controlling friction and wear, wherein the particles are made of an inorganic substance having a plane network crystal structure. A friction material, wherein the frictional material is dispersed such that a direction of delamination of the inorganic crystal is aligned with a direction substantially along a friction surface of the friction material. 2. The dispersed inorganic material having a planar network crystal structure, at least a part of which is granulated with a binder,
2. The method according to claim 1, further comprising a composite material that is granulated so that the granulated shape of the granulated inorganic substance is deformed flat by at least one of pressure and heat during molding. 3. Friction material. 3. The inorganic substance having a planar network crystal structure,
It contains one or more materials of mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, roesite, kaolin, chlorite, sericite, iron hydroxide, montmorillonite, or a mixture thereof with graphite. The friction material according to claim 1 or 2, wherein 4. A method for producing a friction material comprising a thermosetting resin including a fibrous material serving as a base material and a powdery material for controlling friction and wear, wherein the powder comprising an inorganic substance having a planar network crystal structure is provided. Granulating at least a portion of the granules with a binder, and deforming the granulated shape of the granules to be flat by molding the granulated granules using both or one of pressure and heat. A method for producing a friction material, comprising: a step of forming a predetermined thickness by polishing a friction material containing a granular material whose granulated shape is flattened by the molding.