JPH03181627A - Friction material and manufacture thereof - Google Patents

Abstract

PURPOSE:To solve sanitary and environmental problems and to prevent any deterioration in brake performance and any squeaking noise at the time of braking by incorporating a mineral having a plain reticular crystal structure into a granule body, and aligning the direction of separation between the crystal layers of the mineral substantially along the frictional surface of a frictional material. CONSTITUTION:A granule body for regulating friction or abrasion includes a mineral having a plain reticular crystal structure. The mineral is dispersed in such a manner that the direction of separation between crystal layers is aligned substantially along the frictional surface of a frictional material. Accordingly, the granule is likely to generate fine separation on the frictional surface due to a frictional resistance caused by the contact between a brake pad and a disk at the time of the friction so that a stick slip phenomenon can be restrained, and further, any squeaking noise can be effectively prevented at the time of braking while preventing to the utmost a deterioration in brake performance due to a decrease of a frictional coefficient which leads to a fatal wound to the frictional material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a friction material and a method for manufacturing the same, and particularly to disc brakes for trucks, passenger cars, etc.

This invention relates to friction materials used in drum brakes, etc., and methods for manufacturing the same.

[Prior Art] Conventionally, as a friction material used in the brakes of trucks, passenger cars, etc., asbestos-based friction materials have been known for boat fishing. However, due to safety and health issues, there is a demand for friction materials that do not use asbestos.

Friction materials that do not use asbestos and have been generally known include, for example, Japanese Patent Application Laid-Open No. 54-3434.
Publication No. 9, Special Publication No. 4541 of 1983, Special Publication of Publication No. 1987-
Some of these are disclosed in Japanese Patent Publication No. 37187 and Japanese Patent Publication No. 59-4459. Below, they will be explained in order.

First, JP-A-54-34349 discloses a friction material made of a mixture of steel fiber or glass fiber and an inorganic reinforcing material other than asbestos molded with phenol formaldehyde resin, and one of the reinforcing materials is mica. are listed.

Japanese Patent Publication No. 64-4541 discloses that a friction material based on glass fiber and molten liquid crystalline polyester has physical property changes,
It has been disclosed that mica is used as one of the fillers for the purpose of cost reduction.

In Japanese Patent Publication No. 57-37187, fibrous substances O~5
Weight%, mica 20-60% by weight, phenol resin 5
-30% by weight of BaSO, 5-15% by weight of cashew dust, and 5-30% by weight of metal particles, and it has been shown that mica can replace asbestos as a base material. ing.

[Problem to be solved by the invention] As mentioned above, many friction materials that do not use asbestos have been proposed, but they cost the same as asbestos and lack the flexibility that asbestos has.

There is no alternative base material that has strength, abrasion resistance, and softness, and as a result, as mentioned above, multiple fibers have been used in combination to replace asbestos. However, most of the alternative fibers are thick and rigid and do not have the property of enveloping other powders like asbestos, so separation and segregation may occur during handling after mixing asbestos with other powders. If separation and segregation occur, there is a problem that a homogeneous mixture cannot be obtained.

In addition, scaly powder such as mica, which is effective as a substitute for asbestos, is light in weight and tends to fly up during mixing operations, making it extremely difficult to create a homogeneous mixture. Furthermore, materials such as mica have poor wettability with resins used as binders and are difficult to bond sufficiently, resulting in a decrease in the strength of the friction material and the problem of easy formation of cracks and gas blisters during molding and curing. there were. In order to prevent this, if the amount of resin in the binder is increased, the heat resistance of the friction material deteriorates, which has the drawback of increasing gas blistering. In other words, mica, which has been an effective substitute for asbestos, has had a problem in that it has been difficult to make the quality uniform during manufacturing.

On the other hand, among the characteristics conventionally required of friction materials for brakes, an unresolved problem is noise during braking.

Generally, friction materials containing a large amount of solid lubricant such as graphite are known as friction materials that are less likely to cause squeal during braking. However, if a large amount of graphite or the like is used, the friction coefficient μ decreases and the braking force decreases.

Also, those containing a large amount of organic filler such as rubber or cashew dust are also effective in preventing squeal during braking. These are disclosed, for example, in Japanese Patent Publication No. 59-4459. However, this friction material also has the drawback that the friction coefficient μ decreases at high speeds and high temperatures, resulting in increased wear. In other words, it has been difficult to effectively prevent squealing during braking without reducing the braking force, which has been a conventional problem.

This invention was made in order to solve the above-mentioned problems, and the purpose of the invention as set forth in claim 1 is to solve the problem of sanitary environment, and to reduce the coefficient of friction, which is fatal for friction materials. It is an object of the present invention to provide a friction material that can effectively prevent squealing during braking while minimizing a decrease in braking force due to a decrease in braking force.

The object of the invention as set forth in claim 2 is to solve problems in the sanitary environment, to achieve uniform quality during manufacturing, and to reduce the braking force due to a reduction in the coefficient of friction, which is fatal to friction materials. It is an object of the present invention to provide a friction material that can effectively prevent squeal during braking while preventing a decrease in friction as much as possible.

The object of the invention as set forth in claim 3 is to solve problems in the sanitary environment, and to prevent squealing during braking more effectively while preventing a reduction in braking force due to a reduction in the coefficient of friction, which would be fatal to a friction material. The object of the present invention is to provide a friction material that can prevent such problems.

The object of the invention as set forth in claim 4 is to solve problems related to sanitary environment and to ensure uniform quality during manufacturing.

[Means for Solving the Problem] The invention in the first claim is such that the granular material that adjusts friction and wear includes an inorganic substance having a planar network crystal structure, and the direction of delamination of crystal layers of the inorganic substance is aligned with the friction of the friction material. It is characterized by being distributed so as to be aligned in a direction substantially along the surface.

The invention in the second claim provides that the inorganic substance having a planar network crystal structure to be dispersed is granulated at least in part with a binder, and is granulated by pressure and/or heat during molding. It is characterized in that it includes a composite material that is granulated so that the granulated shape of the inorganic substance is deformed into a flat shape.

The invention in claim 3 provides that the inorganic substance having a planar network crystal structure is mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, rouseite, kaolin,
Chlorite, sericite, iron hydroxide.

It is characterized by containing one or more materials of montmorinite or a mixture thereof with graphite.

The invention according to claim 4 includes the steps of: granulating at least a part of a granular material made of an inorganic substance having a planar network crystal structure with a binder; and granulating the granulated granular material using pressure and/or heat. A step of deforming the granulated shape of the powder into a flat shape by molding, and a step of forming the powder to a predetermined thickness by polishing the friction material containing the powder whose shape has been flattened by the molding. including.

[Function] In the invention according to the first claim, the granular material contains an inorganic substance having a planar network crystal structure, and is dispersed so that the delamination direction of the crystals of the inorganic substance is aligned in a direction substantially along the friction surface of the friction material. Because of this, the powder particles tend to cause minute peeling on the friction surface.

In the invention according to claim 2, at least a part of the inorganic material having a planar network crystal structure to be dispersed is granulated with a binder, and the inorganic material is granulated by pressure and/or heat during molding. Since the friction material contains a composite material that is granulated so that the grain shape is flattened, inorganic lumps having a planar network crystal structure are formed, and the manufacturing environment of the friction material is made uniform. The inorganic substance having a planar network crystal structure is arranged so that its glabellar peeling direction is along the frictional direction of the friction material, making it easy for minute peeling to occur on the friction surface.

In the invention according to claim 3, the inorganic substance having a planar network crystal structure includes mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, Rouseite, kaolin,
Chlorite, sericite, iron hydroxide.

Since it contains one or more materials of montmorinite or a mixture thereof with graphite, micro-exfoliation is more likely to occur on the friction surface of the friction material.

In the invention according to claim 4, at least a part of the granular material made of an inorganic substance having a planar network crystal structure is granulated with a binder, and the granulated granular material is granulated using pressure and/or heat. Since the granulated shape of the powder is transformed into a flat shape by the granulation process, inorganic lumps having a planar network crystal structure are formed by granulation, and the manufacturing environment of the friction material is made uniform.

[Embodiment of the Invention] Table 1 shown below is a table showing the material compounding ratio of a disc brake pad according to an embodiment of the present invention. Table 2 shows the graphite particle size, mica particle size, graphite and mica granulation method, binder type and
18 combinations of amount, type of solvent, etc. (A, B
, C1, C2, Dl, D2. E, Fl-
F7. Gl, G2. This is a table showing H, I).

(Left below) Table 1 (Note) When graphite/mica granules are used, ff1 (vol) corresponds to 1/2 of the amount of binder used in the granules.
of phenolic resin.

The remaining 1/2 of the granulation binder is the logarithm of the above 100vo1%.

Mini A is a comparative example and does not contain any mica or graphite, and is not granulated. The molding conditions for the disc brake pad shown in Table 1 are: press temperature 160°C;
The pressing time is 10 minutes, and the pressing pressure is set to a value that gives the finished pad a porosity of 10%. After thermoforming, it is heated in a 220° C. furnace for 10 hours to complete hardening, and then polished to a predetermined thickness.

Referring to Table 2, the graphite used here is a natural scale-like one made in Sri Lanka, and the mica is phlogopite of Canadian acid, both of which are inorganic substances having a planar network crystal structure. Here, the inorganic substances having a planar network crystal structure are 5i04 acid groups, 5i04 polymerized acid groups, 5i04 and Al
It has a crystal structure in which silicate with cations bonded to the skeleton has developed into a secondary planar network. These are described in detail, for example, on pages 11 to 18 of the Ceramics Engineering Handbook edited by the Ceramics Association. In these materials, crystals are developed in a planar shape and are layered, and these layers are bonded by weak van der Waals forces, and there is a sliding phenomenon between the layers. In addition, as an inorganic substance having a planar network crystal structure,
In addition to mica and graphite, talc and vermiculite.

Aluminum hydroxide, magnesium hydroxide, Rouseki.

These include kaolin, chlorite, sericite, iron hydroxide, and montmorinite. Mica particle size is 70μm, 100μm
, 500μm, and the graphite particle size is 6
There are three types: 0 μm, 100 μm, and 270 μm. The granulation method is a method using a rotary pan type granulator and a method using a granulator with an inner diameter of 1 mm.
There are three methods: a method using a twin-screw extruder using slits, and a method in which the kneaded material is sandwiched between two release molds and compressed onto a 0.5 mm sheet with rolls. In Table 2, F-3 and F-6 are the method using a twin-screw extruder, F-3
-4 is granulated by a roll compression method.

Note that F-6 is pulverized after heating at 200° C. for 5 hours, but all other materials are dried below the boiling point of the solvent. Furthermore, granules with an average particle size of 300 μm can be obtained by classification and pulverization. When measuring the size of the granules on the polished surface of the disc brake pad to which the granules were added, it was found that all the granules, except for F-6, were stretched by at least 10%;
D.E.

H and I were stretched 30%.

FIG. 1 is a graph showing the squeal occurrence rate of brake pads A to ■, which were created based on Table 2. The conditions for measuring the squeal occurrence rate were as follows: A-H brake pads were installed on a 2000cc small car, the vehicle speed was 40 km/h, and the pad temperature before braking was varied in 20°C increments from 40°C to 260°C to 60°C. 1 cycle, and at each temperature of each cycle, the deceleration is further reduced by 0.05g between 0.05 and 0.5g.
The frequency of brake squeal was measured in 10 stages. Here, the frequency of brake squeal was measured for a total of 10 cycles and 2200 stops.

In addition to F-1 shown in FIG. 1, FIG.
-1 and F-3, F-4, F-5, F-6, and F-7, which have the same volume percentages of mica and graphite, are graphs showing the squeal occurrence rates measured under the same measurement conditions as in Figure 1. It is.

Figure 3 shows a moment of inertia of 6.0 kg-m-82, measured by a dynamometer assuming a 2000 cc small passenger car.
JA using a disc with a thickness of 22 mm and an outer diameter of 250 mm.
Tested according to the SO6914 test standard. It is a graph showing the friction coefficient μ under the conditions of a second effect of 130 Km/h and a deceleration of 0.6 g.

Experimental results will be described with reference to FIGS. 1, 2, and 3. First, referring to FIGS. 1 and 3, it can be seen that B, in which the amount of mica used is small, has a high squeaking occurrence rate. On the other hand, I, which uses a large amount of mica, has a lower squeal occurrence rate than B. Using mica and graphite together,
It can be seen that F has an even lower squeal occurrence rate than I, and a larger friction coefficient μ than ■. Next, referring to FIG. 2, it can be seen that F-6, which is thermoset using a thermosetting resin, has the highest squeal occurrence rate, and F-3, which is not thermoset, has a lower squeal occurrence rate. Furthermore, the squeaking occurrence rate of F-4 produced using the granulation method of compressing using rolls is lower than that of F-3.

In addition, F-7, which has small particle sizes of mica and graphite, is
It can be seen that the occurrence rate of squealing is as low as in -3.

Discussion will be given below based on the above experimental results.

When mica is used in the same volume, smaller particles are more effective in preventing squeal than larger particles. Furthermore, it is more effective to prevent squealing by scattering mica lumps with smaller particle sizes than by uniformly dispersing mica in the friction material. However, in order to create this mass, the conventionally proposed method of curing and pulverizing a composite material using a thermosetting resin as a binder actually reduces the effect of preventing squealing. This is because mica plates and scales are randomly arranged vertically, horizontally, and diagonally in the friction material. It is necessary to The reason why mica is arranged parallel to the friction surface and its particle size is smaller is more effective in preventing squeal is because the frictional resistance caused by the contact between the brake pad and the disc during friction causes minute flaking of the 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 even more preferably 150 μm or more. The stretched grain size of mica or mica and graphite at the friction surface is 500
It is preferable that the diameter is larger than μm.

Binders are molasses, sodium alginate, latex, polyvinyl alcohol, and cellulose.

Adhesives such as gelatin, pitch, and lignin, thermoplastic resins, and thermosetting resins in an incomplete state of curing reaction can be used.

These binders may be used alone, but in order to facilitate the granulation of mica-graphite, which has poor wettability, it is preferable to use a pressure-sensitive adhesive and a resin in combination. In this case, thermoplastic resins are preferred in terms of increasing the fluidity of the granules during molding. Note that the binder is not limited to organic materials, but may be inorganic materials such as sodium silicate and sodium polyphosphate.

The amount of binder used is 0.0 per 1 part of the granulated material in terms of volume ratio.
2 to 1.0 is good, more preferably 0.04 to 0.0.
5. Furthermore, 0.06 to 0.35 is desirable. If there is a lack of binder, granulation is insufficient and dust is likely to be generated.
Excessive use will deteriorate the friction performance when used in friction materials.

The granulation method uses a panburi mixer, a rubber roll for mixing, a pressure kneader, and an extruder to obtain a lump by applying heat and/or pressure. Then, dry and crush as necessary. In order to increase the fluidity during molding, a rotary pan type granulator is preferred since it can produce granules with low apparent density without applying pressure. Depending on the particle size of mica or graphite, a spray fluidized drying granulator may be used. Additionally, as an exception, the method of compressing it into a thin sheet with rolls is effective in preventing squealing because the mica and graphite are aligned in one direction.

Other than mica, inorganic substances with a planar network crystal structure include talc, vermiculite, aluminum hydroxide,
Examples include magnesium hydroxide, Rouseki, kaolin, chlorite, sericite, iron hydroxide, and montmorinite, and similar effects can be obtained by making granules of these and graphite.

Table 3 shown below is a table showing the material compounding 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 the squeal occurrence rate when a squeal test was conducted on the disc brake pads shown in Table 3 under the same measurement conditions as shown in FIG. 1.

(Margins below) FIG. 4 is a process diagram for explaining the method for manufacturing the disc brake pad shown in Table 3. Referring to FIG. 4, the method for manufacturing the disc brake pad shown in Table 3 will be described first.

First, as shown in step 101, the granulation raw materials shown in Table 3 are granulated using a rotary pan type granulator.

Sodium alginate and polyvinyl alcohol are used as the binder, and water is used as the diluent. Then, as shown in step 102, the molding conditions for the disc brake pad shown in Table 3 are the same as in Table 1: press temperature 160°C, press time 10 minutes, press pressure such that the porosity of the completed pad is 10%. After thermoforming, the resin was heated in a furnace at 220° C. for 10 hours to complete curing.

Thereafter, as shown in step 103, it is polished to a predetermined thickness.

Referring to Tables 3 and 4, talc, aluminum hydroxide, vermiculite, magnesium hydroxide, Rouseki, kaolin, chlorite, sericite, iron hydroxide, and montmorinite have the same effect on brake pad squealing as mica. It has the effect of reducing The amount of these added is preferably 1/2 or less of the total planar network crystal structure, more preferably 115 or less.

Note that graphite is a planar network crystal structure 1. 0vo
Maximum 2.0 vol or less, preferably 1.5 vol per l
It is desirable that it be less than 1, more preferably less than 1, Qvol.

Increasing the amount of graphite added is effective in preventing squealing, but this results in a decrease in the friction coefficient μ.

As described above, in this example, one or more of mica, vermiculite, graphite, talc, magnesium hydroxide, rouseki, kaolin, chlorite, sericite, iron hydroxide, and montmorinite are granulated with an organic/inorganic binder. The lumps are then shaped and used as part of the friction material raw material. The binder for granulation is one that can be softened and flowed by heat or both heat and pressure when molding the friction material, and the shape of the granules after molding is different from the original shape and is stretched flat. It is something that By using such a binder, inorganic lumps with a planar network crystal structure, such as mica, are dispersed on the surface of the friction material and arranged along the friction direction, making it easier for micro-peeling to occur. , is effective in reducing brake squeal. In addition, as a result of our search for a material that is effective in reducing brake squeal, we found mica, an inorganic material with a planar network crystal structure.

Vermiculite, aluminum hydroxide, and magnesium hydroxide are effective, and the effect can be improved by using graphite in combination. The amount of granules to be added may range from 1 to 35% by volume, preferably from 3 to 30% by volume.

More preferably, it is 5 to 25% by volume. Here, if the amount of granules added is small, the effect of preventing squeal is small, and conversely, if the amount added is too large, the high-speed friction coefficient μ decreases. Of course, ungranulated mica, graphite, etc. may also be used in combination with this granulated material. In this example, an inorganic material having a planar network crystal structure is used, but the present invention is not limited to this, and may have a crystal structure similar to the planar network crystal structure.

In addition, in the method for manufacturing a disc brake pad shown in Fig. 4, an inorganic substance having a planar network crystal structure, such as mica, is granulated with a binder, and then molded without curing, so that the granulated shape of mica etc. is flat. As a result, minute peeling is likely to occur 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 it is possible to effectively improve manufacturing problems such as mica flying up, which has been a problem in the past. In addition, since granulation reduces the number of particles, it is effective against the problems of separation and segregation when using conventional fibers as a base material, as well as the reduction in friction material strength due to poor wettability between mica and binder. can be prevented.

[Effects of the Invention] As described above, the invention according to the first claim solves the problem regarding the sanitary environment, and prevents as much as possible the decrease in braking force due to the decrease in the coefficient of friction, which would be fatal for a friction material. However, it has now been possible to provide a friction material that can effectively prevent squeal during braking.

According to the invention according to the second claim, problems regarding the sanitary environment can be solved and quality can be made uniform during manufacturing, and
It has now been possible to provide a friction material that can effectively prevent squeal during braking while minimizing the reduction in braking force due to a reduction in the coefficient of friction, which would be fatal to a friction material.

According to the invention according to the third claim, the problem in the sanitary environment is solved, and squealing during braking is more effectively prevented while preventing a decrease in braking force due to a decrease in the coefficient of friction, which would be fatal to a friction material. We have now been able to provide a friction material that can

According to the fourth aspect of the invention, it has become possible to provide a method for manufacturing a friction material that can solve problems related to the sanitary environment and also ensure uniform quality during manufacturing.

[Brief explanation of drawings]

Figure 1 is a graph showing the squeal occurrence rate of brake pads A to ■, which was created based on Table 2. Figure 2 shows the brake pads of F-1 and mica and F-3, F-4, F-5, F with the same volume percent of graphite
-6, F-7 are measured under the same measurement conditions as Figure 1. Figure 3 is a graph showing the noise occurrence rate measured under the same measurement conditions as Figure 1.
FIG. 4 is a graph showing the coefficient of friction μ when tested according to the test standards of No. 14, and FIG. 4 is a process diagram for explaining the manufacturing method of the disc brake pad shown in Table 3. In each figure, the same reference numerals indicate the same or corresponding parts. 3rd U￥J (:i) JAS○ 6914 $2 Effectiveness 30Km/H
o6gq44J? '-Bu 11th Figure 4

Claims (4)

[Claims] (1) A friction material made of a thermosetting resin including fibrous material as a base material and granular material for adjusting friction and wear, the granular material containing an inorganic substance having a planar network crystal structure, A friction material, characterized in that the inorganic crystals are dispersed so that the delamination direction is aligned in a direction substantially along the friction surface of the friction material. (2) At least a portion of the dispersed inorganic material having a planar network crystal structure is granulated with a binder, and the granulated shape of the granulated inorganic material is changed by pressure and/or heat during molding. The friction material according to claim 1, comprising a composite material that is granulated to be deformed into a flat shape. (3) The inorganic substance having a planar network crystal structure includes mica, talc, vermiculite, aluminum hydroxide, magnesium hydroxide, rouseki, kaolin, chlorite, sericite,
The friction material according to claim 1 or 2, characterized in that it contains one or more of iron hydroxide and montmorinite, or a mixture thereof with graphite. (4) A method for producing a friction material made of a thermosetting resin containing fibrous material as a base material and powder or granules that adjust friction and wear, the powder or granules made of an inorganic substance having a planar network crystal structure. granulating at least a portion of the powder with a binder; and shaping the granulated powder using pressure and/or heat to flatten the granulated shape of the powder. A method for manufacturing a friction material, comprising: forming the friction material to a predetermined thickness by polishing the friction material containing powder particles whose granulation shape has been flattened by the molding.