JP3068798B2 - Friction material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used as a disc brake pad, a drum brake lining, or a clutch facing of an automobile or the like.

[0002]

2. Description of the Related Art Friction materials used for disc brake pads, drum brake shoes, and the like of an automobile frictionally engage with a disc rotor and a brake drum, which are mating members, to convert kinetic energy into heat energy. It plays an important role in changing. Therefore, the friction material needs to have not only a sufficient coefficient of friction but also high strength capable of withstanding a high load, and excellent heat resistance and wear resistance. Further, it is necessary that the coefficient of friction is stable with little change with respect to temperature change due to heat generated during braking. Furthermore, it is also important that the aggressiveness against the opponent material is low, and that noise (brake squeal) and judder are less generated, and the characteristics required for the friction material cover various items.

[0003] Therefore, in order to satisfy these various characteristics, the friction material has conventionally been constituted as a composite material composed of many material components. That is, the friction material is a fibrous base material that is a fibrous component forming the skeleton thereof, a resin binder that is a resin component that binds and holds the fibrous base material, and a powdery component. It is formed from various fillers dispersed and filled in a matrix of a base material and a resin binder for improving friction and wear characteristics. In addition,
As the resin binder, a thermosetting resin such as a phenol resin is generally used. In addition, as a filler,
Solid lubricants such as graphite for adjusting and stabilizing the coefficient of friction, friction modifiers such as cashew dust, and fillers such as barium sulfate and calcium carbonate for ensuring heat and wear resistance. In addition, abrasives such as zirconium silicate powder for increasing the coefficient of friction are used.

[0004] Here, a fiber base material which forms its skeleton as a base material of a friction material, imparts appropriate porosity to the skeleton, and gives the overall strength and elasticity thereof has a major influence on its main characteristics. It is an important ingredient. As such a fiber base material, asbestos fiber (asbestos) has been used in the past, but since the dust has health concerns, fiber materials other than asbestos fiber have recently been used.

As one example, there is a semi-metallic friction material using steel (carbon steel) fiber as a main material of a fiber base material. This semi-metallic friction material is excellent in heat resistance and wear resistance, and can obtain a relatively high friction coefficient. However, on the other hand, it has a problem that it is heavy, rusts, and furthermore, the mating material is easily damaged and worn.

[0006] Therefore, in recent years, so-called non-steel friction materials which do not use steel fibers as a fiber base material or have a small blending amount even if they are used have become the mainstream of friction materials. In this non-steel friction material, heat-resistant organic fibers such as aramid fibers, glass fibers, inorganic fibers such as potassium titanate fibers or whiskers, and non-ferrous metal fibers such as copper fibers and brass fibers are mainly used as the fiber base material. In addition, since only one of these types does not provide sufficient performance as an alternative to asbestos fiber, a combination of a plurality of types is used.

[0007] However, non-steel friction materials using such asbestos-substitute fibers tend to have a generally low coefficient of friction because the fibers are relatively soft and have relatively low hardness. Therefore, in particular, in this kind of friction material, it is known to use abrasive ceramic fibers in combination with a part of the fiber base material in order to sufficiently increase the friction coefficient (for example, see Japanese Patent Application Laid-Open Publication No. H11-163873). JP-A-4-60225, JP-A-4-106183, JP-A-4-30
4284, JP-A-8-296678, etc.).

That is, the abrasive ceramic fiber is generally made of a high-hardness ceramic fiber having a Mohs hardness of 4 or more, and specifically, silica fiber, alumina fiber,
Alumina-silica-based fibers, alumina-silica-zirconia-based fibers, silicon carbide-based fibers, slag wool, rock wool and the like can be mentioned. Among these, alumina-
Silica-based fibers and alumina-silica-zirconia-based fibers have relatively high hardness, and are therefore the most typical of such ceramic fibers. In addition, these ceramic fibers are generally a method in which a melt of a raw material flows down from a nozzle and is applied to a high-speed airflow, or a method of forming fibers by utilizing the centrifugal force of a rotating disk, a so-called molten fiber. A precursor fiber from a spinning solution (spinning raw material) containing the constituent elements of the target fiber by
It is manufactured by firing it in a predetermined atmosphere, a so-called precursor fiber method.

By using such a ceramic fiber as a part of the fiber base material, the friction coefficient of the friction material can be improved due to its abrasiveness, and the friction coefficient generated on the friction engagement surface of the mating material can be improved. Stained rust can be satisfactorily removed and cleaned. However, its abrasiveness (grindability)
At the same time, it increases the wear of the mating material. Therefore, in the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-296678 filed by the applicant of the present invention, while suppressing the wear of the mating material to a lesser extent, in order to increase the friction coefficient, the fiber diameter is sufficiently small. Has an average fiber diameter of 1.0 to 4.
The use of 5 μm ceramic fibers is proposed.

[0010]

Thus, the friction material,
In particular, in non-steel friction materials, it is known to use abrasive ceramic fibers such as silica-alumina as a part of the fiber base material. And according to this,
Not only can the strength and heat resistance of the friction material be improved, and the wear resistance can be further improved, but also the abrasiveness of the ceramic fibers can effectively increase the friction coefficient of the friction material and improve the rust resistance. Dropping property can be secured. However, conversely, the abrasiveness (grindability) of the ceramic fiber also increases the aggressiveness to the counterpart material, which increases its wear. Also, the wear of the mating material increases as the content of the ceramic fiber increases in order to obtain a higher coefficient of friction. Such an increase in the wear of the mating member is not only undesirable, but if it proceeds excessively, it may cause uneven wear, which may cause noise or abnormal vibration such as brake judder. .

However, regarding the conflicting improvement of the friction coefficient and the increase (deterioration) of the wear of the mating material, the above-mentioned Japanese Patent Application Laid-open No.
According to the technical means disclosed in Japanese Unexamined Patent Publication No. 296678/1990, it is possible to solve the problem advantageously. That is, as taught in the publication, the use of an abrasive ceramic fiber having a sufficiently small fiber diameter makes it possible to increase the friction coefficient without increasing the wear of the mating material. In other words, while suppressing the wear of the mating material to a low level,
A high coefficient of friction can be ensured.

However, even with such a friction material using a ceramic fiber having a sufficiently small fiber diameter, particularly in recent years, the braking conditions tend to become more and more severe due to an increase in the output and speed of an automobile. Therefore, it is needless to say that it is desirable to obtain an even higher coefficient of friction. Also, with the recent spread of RV vehicles, good rust removal properties are also important characteristics required for friction materials. For this reason, friction materials containing abrasive ceramic fibers such as alumina-silica fibers as a part of the fiber base material, particularly non-steel friction materials, reduce the wear of the mating material and increase the friction. Coefficient and
Ensuring better rust removal properties is still one of the major issues.

Accordingly, an object of the present invention is to provide a friction material which can ensure a high coefficient of friction and good rust-removing property and can reduce the amount of wear of a mating material. is there.

[0014]

The present inventors have conducted further detailed studies on the abrasive ceramic fibers based on the teachings of the above-mentioned Japanese Patent Application Laid-Open No. 8-296678, and as a result, have found that the teachings are as follows. In addition, the coefficient of friction and the wear of the mating material mainly depend on the fiber diameter, and a sufficiently small fiber diameter can improve the friction coefficient while suppressing the wear of the mating material to a small extent. It is not only related to the fiber diameter but also related to the fiber length, and it is relatively long with respect to the fiber diameter, but it has been found that by having a fiber length in an appropriate range that is not too long, good rust removing properties can be obtained. . Further, the abrasive ceramic fiber produced by the melt fiberization method or the precursor fiber method also has a scaly shape formed by exfoliating the surface layer of the fiber into a scaly shape at the time of production (at the time of cooling). The flakes inhibit abrasiveness and reduce the wear of the mating material, but tend to lower the coefficient of friction in particular, and therefore, as ceramic fibers, the content of the flakes By reducing the amount sufficiently, that is, by using less flakes that increase the bulk, relatively high bulk density,
They have found and confirmed that a higher coefficient of friction can be ensured.

That is, the friction material according to the present invention is a friction material comprising a fiber substrate containing abrasive ceramic fibers, a resin binder and a filler, wherein the abrasive ceramic fibers have an average fiber diameter. Is 1.0 to 5.0 μm, the average fiber length is 50 to 150 μm, and the bulk density is 0.20 to
0.40 g / cm ³ , 1 to 10
It is characterized in that it is contained in a proportion of% by weight (claim 1).

According to another aspect, the friction material according to the present invention comprises: a fiber base material containing abrasive ceramic fibers;
In a friction material composed of a resin binder and a filler, the abrasive ceramic fibers have an average fiber diameter of 1.0 to 5.0.
0 μm, the average fiber length is 50 to 150 μm, and
The content ratio of the scale-like material obtained by peeling the surface layer of the fiber to the entire fiber is 30% or less, and 1 to 1 to the entire friction material.
It is characterized by being contained at a ratio of 10% by weight.

Here, the content ratio of the scaly material is determined from a scanning electron microscope (SEM) photograph of the fiber. That is, the SEM photograph (magnification: 10
The area occupied by the scaly material and the area occupied by the fibrous material (fiber main body) are determined by rough estimation, respectively, and the area of the fibrous material and the area of the scaly material in the area of the scaly material are calculated. Is calculated as a ratio to the total area. Further, here, the flaky material, which is a peeled material of the fiber surface layer, is not only one that is completely peeled off from the fiber main body, but is attached to the fiber main body but is in a state where it is substantially peeled off. It also includes scales.

Thus, in the friction material of the present invention,
As a part of the fiber base material, the fiber diameter is sufficiently small, the average fiber diameter is 1.0 to 5.0 μm, and the average fiber length is 50 to
With a suitable range of 150 μm and a bulk density of 0.2
Abrasive ceramic fibers having a relatively large ratio of 0 to 0.40 g / cm ³ , that is, a small percentage of flakes, which are exfoliated material of the fiber surface layer, and a ratio of 30% or less to the entire fiber, are friction materials. Since it is blended at a ratio of 1 to 10% by weight with respect to the whole, as is clear from the test results described later, it is possible to suppress the wear of the mating material to a small extent,
Higher coefficient of friction and good rust removal properties can be ensured.

Although the reason for this is not necessarily clear, it can be inferred from the test results as follows. In other words, the coefficient of friction can be increased to the same degree by the abrasiveness regardless of the fiber diameter of the ceramic fiber. However, with respect to the abrasion of the mating material, if the fiber diameter is relatively large, the grinding (grinding) of the mating material becomes coarse. As a result, the abrasion of the mating material also increases. On the other hand, if the fiber diameter is sufficiently small, the polishing is performed more uniformly and smoothly. It is considered that the reason why the fiber diameter is sufficiently small as described above is that the friction coefficient can be increased while the wear of the mating material is suppressed relatively small. Similarly, with respect to the rust-removing property, the rust-removing property can be enhanced while the abrasion of the mating material is reduced by the fiber diameter being sufficiently small. It is at such a fiber length that the rust-removing property is obtained when the ceramic fibers are best arranged in parallel with the friction material surface at the time of preforming the friction material by compression molding, so that better with the mating material surface. Probably because contact was obtained. Furthermore, the flakes, which are the product of peeling of the surface layer of the ceramic fiber, hinder the abrasiveness because the flakes that are easily broken are further pulverized at the time of frictional engagement with a counterpart material, and the pulverized particles are formed. Is considered to be interposed between the friction material and the mating material and rather act as a lubricant. This is probably because the content of such scaly substances is sufficiently small and the bulk density is relatively high, so that a higher coefficient of friction can be obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the friction material will be described in more detail.

As described above, in the friction material of the present invention, the average fiber diameter is 1.0 to 5.
0 μm, the average fiber length is 50 to 150 μm, and
Abrasive ceramic fibers having a bulk density of 0.20 to 0.40 g / cm ^3, that is, having a small proportion of flakes contained in the fibers and having a bulk density of 30% or less based on the entire fibers are used.

As the abrasive ceramic fibers, those having a Mohs hardness of generally 4 or more can be used. However, potassium titanate fibers or whiskers having a Mohs hardness of 4 are not included in the abrasive ceramic fibers because they have excellent wear resistance but no abrasive properties. Therefore, the Mohs hardness of the abrasive ceramic fiber is more strictly 4.5 or higher than that of the potassium titanate fiber or whisker. On the other hand, the upper limit is not particularly limited,
Even if the hardness is too high, the effect of improving the coefficient of friction is limited. For this reason, the Mohs hardness of the ceramic fibers used is generally generally 4.5 to 9, preferably the Mohs hardness of the alumina fibers, and more preferably about 5 to 7 in practical use.

Examples of the abrasive ceramic fibers having such Mohs hardness include silica fibers, alumina fibers, zirconia fibers, alumina-silica fibers, alumina-silica-zirconia fibers, and silicon carbide. System fiber, rock wool or slag wool can be used. However, among these, alumina-silica-based fibers and alumina-silica-zirconia-based fibers, which are also common as ceramic fibers for thermal insulation, have a moderately high hardness and can easily obtain desired properties. In this respect, it can be particularly preferably used.

In general, these abrasive ceramic fibers are produced by melting a raw material, stretching the melt into a fibrous form, and cooling and solidifying the melt. A precursor fiber can be obtained by a method of forming a precursor fiber from a spinning solution containing a constituent element of a target fiber and firing the fiber in a predetermined atmosphere to produce a fiber, a so-called precursor fiber method. More specifically, for example, in the case of alumina-silica-based fiber, raw materials alumina and silica are mixed and melted at a predetermined ratio to form a raw material melt, and this melt is injected from a nozzle into an air jet. And blown off with an air jet to split and stretch to make fine fibers and to cool and solidify (blowing method), or to flow the melt down onto a rotating disk and use the centrifugal force of it. It can be manufactured by a method of splitting and drawing by spinning to form fibers by cooling and solidifying by cooling (spinning method). In the case of the precursor fiber method, the same method is used, but a basic aluminum formate or the like is used as an alumina source, and a water-soluble silicone or silica sol is used as a silica source. The fiber diameter and fiber length of the obtained ceramic fiber can be adjusted by appropriately setting conditions such as blowing.

The fiber diameter of the abrasive ceramic fiber is preferably as small as possible in order to sufficiently suppress the wear of the mating material, and is preferably smaller than 5.0 μm in average fiber diameter. However, for fibers having an average fiber diameter of less than 1.0 μm,
Not only is it relatively difficult to manufacture, but also it tends to be difficult to ensure a sufficient coefficient of friction and rust removal properties of the mating material. Therefore, it is appropriate that the average fiber diameter is 1.0 to 5.0 μm. In addition to the fiber diameter, the average fiber length of the ceramic fibers used is 50 to 1 in terms of average fiber length.
Suitably, it is 50 μm, whereby particularly good rust removal properties can be obtained. That is, from the viewpoint of rust removal properties, the fiber length is preferably as relatively long as possible, and the average fiber length of 50 μm or more which is at least 10 times the average fiber diameter is preferable. However, if the fiber length is too long, the rust-removing property tends to be rather deteriorated, and within the range confirmed experimentally, the average fiber length is preferably shorter than 150 μm.
The fiber diameter and the fiber length can be set independently of each other.However, considering the ease of production and the holding property in a friction material, the average fiber length with respect to the average fiber diameter is considered. The ratio (aspect ratio) is most preferably about 20 to 50.

By the way, as described above, the flaky material, which is a product of peeling the fiber surface layer, is completely peeled off from the fiber in the ceramic fiber generally produced by the melt fiberization method or the precursor fiber method. It is contained in a state or as it is adhered to the fiber. That is, this scaly substance is
In the cooling process during the production of ceramic fibers, due to the difference in cooling rate between the surface and the interior of the fiber (particularly due to rapid cooling of the surface), the surface layer becomes brittle and peels off like scales (flakes). To generate. And when such a scale is large, it may be contained in a ratio exceeding 40% in some cases. In addition, this flaky material increases the bulk of the fiber, and therefore, as the content thereof increases, the bulk density of the ceramic fiber decreases.

Since the flakes are made of flakes, they are contained in the fibers only in a relatively small proportion in weight. However, this hinders the abrasiveness of the ceramic fiber, thereby reducing the effect of improving the coefficient of friction. Therefore, in order to obtain a higher coefficient of friction, it is preferable that this flake is removed as much as possible, and the content of the fiber calculated from the SEM photograph is preferably at least 30% or less, and 20% or less. Or less, and 1
More preferably 5%, most preferably 10%.
% Or less. However, it is impossible to completely remove the flakes because at least a part of the flakes is integrally adhered to the fiber, and the content thereof is practically limited to about 5%. . The removal of the scale can be carried out by treatment with a dry air classifier or the like, but the lower the content ratio, the higher the cost required. Therefore, at least 30
%, But the specific content of the scaly material to be removed can be appropriately determined in consideration of the cost.

On the other hand, when the ceramic fiber to be used has been subjected to such a scaly removal treatment and has a bulk density of 0.20 g / cm ³ or more, a higher friction coefficient can be secured. Has been confirmed. That is, the bulk density of the ceramic fibers is relatively large,
When g / cm ³ or more, the scale contained therein is sufficiently small (at least 30% or less), whereby the abrasiveness of the ceramic fiber is sufficiently exhibited.
A higher coefficient of friction can be obtained. The upper limit of the bulk density is not particularly important, but is too large.
If it exceeds 0.40 g / cm ³ , the fiber diameter or fiber length of the ceramic fiber may fall outside the above-mentioned appropriate range. Therefore, the bulk density of the ceramic fiber used is 0.1.
A range from 20 to 0.40 g / cm ³ is preferred and suitable. The bulk density is calculated from the volume of a sample fiber taken in a measuring cup, subjected to microtremor, and weighed.

Then, the abrasive ceramic fiber is
Generally, it can be blended at a ratio of 1 to 10% by weight with respect to the entire friction material. In other words, the content of this compound is too small.
If the amount is less than the percentage by weight, it is difficult to obtain a sufficient effect of improving the coefficient of friction, and it is also difficult to satisfactorily remove the rust of the mating material. On the other hand, as the content of the composition is increased, the coefficient of friction is further improved, and the rust-removing property is also enhanced. However, if the composition is too large, the wear of the mating material also tends to increase. For this reason, it is preferable that the content is limited to 10% by weight or less. Therefore also
The compounding ratio is usually less than half of the entire fiber substrate even when it is large.

The friction material components other than the ceramic fibers, that is, other fiber base materials, resin binders, and fillers, are basically the same as those in the related art.

That is, as the fibrous base material, a fibrous material having no or little aggressiveness to a mating material, that is, a non-abrasive material and usually having a Mohs hardness of 4 or less can be used. Specifically, heat-resistant organic fibers such as aramid fibers, novoloid fibers, nylon fibers, rayon fibers, etc .; inorganic fibers such as potassium titanate fibers or whiskers, carbon fibers, or glass fibers; non-ferrous metals such as copper fibers and brass fibers. Fiber and the like. These fibers can generally be used in combination with the above-mentioned abrasive ceramic fibers by combining two or more of them.

As the fiber substrate, steel fibers or stainless steel fibers can also be used.
When this steel fiber is used as the main material of the fiber base material, the friction material is formed as a semi-metallic friction material. In this case, the friction coefficient is sufficiently increased by the abrasive steel material. The ceramic fiber contained as a part of the fiber base material increases the friction coefficient of the friction material, rather than increasing the friction coefficient of the friction material. .

As the resin binder for binding and holding the fiber base material and the filler, phenol resin, melamine resin,
Epoxy resin, polyimide resin, polyester resin, or rubber such as SBR can be used.
However, among these, a phenol resin or various modified products thereof are the most commonly used, and are particularly preferable. As the phenol resin, a novolak-type powder can be generally used.

Further, as fillers for adjusting and improving the friction and wear characteristics of the friction material, solid lubricants such as graphite (graphite), molybdenum disulfide, antimony trisulfide and the like, fillers such as barium sulfate and calcium carbonate can be used. , Cashew dust or other polymer powders, mainly metal powders such as copper powder, zinc powder, brass powder for improving thermal conductivity, or other additives for friction adjustment. Further, when the friction coefficient is still insufficient due to the use of the above-mentioned abrasive ceramic fibers, if necessary, use an abrasive agent such as alumina powder, silica powder, zirconium silicate powder, or zirconium oxide powder in combination. You can also. However, the effect of improving the rust-removing property cannot be expected much with this abrasive.

The friction material of the present invention comprising the above components, that is, a fiber base material containing abrasive ceramic fibers, a resin binder, and a filler is prepared by mixing these material components. Can be manufactured by a conventional thermoforming method of preforming by compression and then heating and pressing.

[0036]

The present invention will be more specifically described below with reference to examples and comparative examples.

FIG. 1 is a table showing the compounding composition (% by weight) of the friction material according to the example of the present invention and the evaluation test results. FIG. 2 is a table showing the composition (% by weight) of the friction material of the comparative example and the evaluation test results.

[Production of Friction Material (Pad)] The friction materials of Examples 1 to 6 of the present invention were produced with the composition (% by weight) shown in FIG. Further, for comparison with these examples, the friction materials of Comparative Examples 1 to 6 were also produced with the composition (% by weight) shown in FIG. Note that the friction materials of these examples and comparative examples are specifically embodied as pads for disc brakes of automobiles.

As shown in FIGS. 1 and 2, the friction materials of these examples and comparative examples are composed of a fibrous base material which is a fibrous component forming a skeleton thereof, and a resin bond for bonding and holding the fibrous base material. And a filler, which is a powdery component that is dispersed and filled in a matrix of these fiber base materials and a resin binder, and as a part of the fiber base material, an abrasive ceramic It contains fibers. In each of these Examples and Comparative Examples, the type of the abrasive ceramic fiber and the mixing ratio thereof were variously changed.

Specifically, the fiber base material includes aramid fiber as a main material, a potassium titanate whisker for mainly ensuring heat resistance and abrasion resistance, and a fiber for mainly maintaining thermal conductivity. In addition to copper fiber, the abrasive ceramic fiber is used. Therefore, each friction material is formed here as a non-steel friction material that does not include steel fibers. And in each example and comparative example,
With the aramid fiber 5% by weight, the potassium titanate whisker 8% by weight, and the copper fiber 11% by weight as fixed conditions, the ratio of the ceramic fiber was changed in the range of 0 to 11% by weight.

A phenol resin (novolak type) was used as a resin binder, and was mixed with a curing agent at a ratio of 7% by weight in each of Examples and Comparative Examples.

As the filler, cashew dust for adjusting and stabilizing the coefficient of friction, graphite which is a solid lubricant mainly for improving abrasion resistance, and alkali for maintaining the alkalinity of the friction material. Slaked lime for enhancing rust prevention, zirconium silicate as an abrasive, and barium sulfate as a filler were used. In each of Examples and Comparative Examples, 9% by weight of cashew dust and 7% of graphite were used.
%, And 4% by weight of slaked lime, as fixed conditions, and zirconium silicate is 12% by weight and 8% by weight in Examples 1 and 6, respectively, in which the amount of ceramic fiber is relatively small as described later. In Comparative Example 6, where no ceramic fiber was blended, the content was 14% by weight, and in each of the other Examples and Comparative Examples, 4% by weight was blended. Then, the mixing ratio of barium sulfate was changed to adjust the total to 100% by weight. That is, in each of the examples and comparative examples, the components other than the abrasive ceramic fiber are the same, and the mixing ratios of the ceramic fiber and zirconium silicate are substantially the same.

Here, as the abrasive ceramic fiber,
The following nine types of alumina-silica-based ceramic fibers A differing in fiber diameter, fiber length, bulk density, and content of flakes
~ I were prepared. These alumina-silica-based ceramic fibers (Mohs hardness 6) were produced by the melt fiberization method under various conditions of fineness, etc. The flakes (fiber release product) contained in the flakes were separated and removed using a dry air classifier, more precisely, the content was reduced. However, in the case of the ceramic fiber I, the scaly material was not removed.

<Ceramic fiber A> Average fiber diameter 5.0 μm
m, average fiber length 150 μm, bulk density 0.24 g / cm ³ ,
Approximately 10% content of flakes. <Ceramic fiber B> Average fiber diameter: 3.0 μm, average fiber length: 130 μm, bulk density: 0.20 g / cm ³ , scale content: about 10%. <Ceramic fiber C> Average fiber diameter: 3.0 μm, average fiber length: 100 μm, bulk density: 0.25 g / cm ³ , flake content: about 10%. <Ceramic fiber D> Average fiber diameter: 3.0 μm, average fiber length: 70 μm, bulk density: 0.35 g / cm ³ , flake content: about 5%. <Ceramic fiber E> Average fiber diameter 1.0 μm, average fiber length 70 μm, bulk density 0.23 g / cm ³ , content of flakes about 10%. <Ceramic fiber F> Average fiber diameter 0.9 μm, average fiber length 40 μm, bulk density 0.25 g / cm ³ , flake content about 10%. <Ceramic fiber G> Average fiber diameter 5.5 μm, average fiber length 160 μm, bulk density 0.25 g / cm ³ , flake content about 10%. <Ceramic fiber H> Average fiber diameter 5.0 μm, average fiber length 30 μm, bulk density 0.45 g / cm ³ , content ratio of flakes about 10%. <Ceramic fiber I> Average fiber diameter: 3.0 μm, average fiber length: 100 μm, bulk density: 0.18 g / cm ³ , scale content: about 35%. As described above, the content ratio (%) of the flaky material was determined from a scanning electron microscope (SEM) photograph of the fiber, and the area of the flaky material / (the area of the fibrous material + the flaky shape) (Area of an object).

In Example 1, the ceramic fiber A was blended at a ratio of 1% by weight to the whole friction material.
Similarly, the ceramic fiber B is used in Example 2, the ceramic fiber C is used in Example 3, and the ceramic fiber D is used in Example 4.
Was blended at a ratio of 5% by weight, and in Example 5, the ceramic fiber E was blended at 10% by weight, and in Example 6, the ceramic fiber C was blended at a ratio of 3% by weight.

In contrast to these examples, the ceramic fiber F in Comparative Example 1, the ceramic fiber G in Comparative Example 2,
In Comparative Example 3, 5% by weight of the ceramic fiber H was added, and in Comparative Example 4, 5% by weight of the ceramic fiber I was added. In Comparative Example 5, ceramic fiber I was also used, and its blending ratio was increased to 11% by weight. Further, in Comparative Example 6, no ceramic fiber was blended.

The production of the friction materials (disk brake pads) of these Examples and Comparative Examples was carried out by a usual thermoforming method, specifically as follows. That is, the friction material raw materials of the above-mentioned composition containing various ceramic fibers in various ratios are mixed sufficiently uniformly with a blender,
This powdery mixture was put into a preforming mold and pressed at a normal temperature of 200 kg / cm ² for about 1 minute to form a substantially pad-shaped friction material preform. Next, the preform of the friction material was set in a thermoforming mold together with a back metal having a surface coated with a phenolic resin adhesive in advance, and a pressure of 400
Thermoforming was performed at a temperature of 160 ° C. for 10 minutes at kg / cm ² . This was further heat-treated at 250 ° C. for 120 minutes to obtain a friction material integrated with the back metal, ie, a disc brake pad.

[Evaluation Test] Next, with respect to the friction materials (disc brake pads) produced in these Examples and Comparative Examples, the friction coefficient, the aggressiveness of the mating material (abrasion of the mating material) and the rust-removing property were evaluated. An evaluation test was performed.

Regarding the coefficient of friction, 3000 reduction braking tests were performed, and the final coefficient of friction at that time was measured.
The test conditions are as follows. Caliper brake model used: PD51-18V Inertia: 4.0 kgfms ² Temperature before braking: 100 ° C Initial speed: 50 km / h Deceleration: 0.1G.

Regarding the aggressiveness with respect to the mating material (a 18 mm thick ventilated disc rotor made of cast iron), a braking test was performed 400 times, and the wear amount of the mating material at that time was measured. The test conditions are as follows. Caliper brake model used: PD51-18V Inertia: 4.0 kgfms ² Temperature before braking: 120 ° C Initial speed: 65 km / h Deceleration: 0.35G.

Further, regarding the rust-removing property, a braking test was performed 100 times with the above-mentioned disk rotor in which rust was generated in advance as a mating material, and the thickness of the rust dropped at that time (the thickness of the remaining rust) was determined. The rust removal rate (thickness of dropped rust / thickness of initial rust [%]) was measured. The test conditions are as follows. Caliper brake model used: PD51-18V Rotor rust thickness before test: 50-100 μm Inertia: 4.0 kgf · m · s ² Temperature before braking: 120 ° C. Initial speed: 65 km / h Deceleration: 0.35 G.

FIG. 1 and FIG. 2 show the measured friction coefficient, the wear amount (μm) of the disk rotor as the mating material, and the rust removal rate (%) together with the composition of the friction material.

[Test Results] As shown in FIG. 1, the average fiber diameter of the abrasive ceramic fibers was 1.0 to 5.0 μm.
Ceramic (alumina-silica) fibers A to E having an average fiber length in the range of 50 to 150 μm, a bulk density of 0.20 or more, and a flake content of about 10% or less. In the friction materials of Examples 1 to 6 used, while the wear amount of the disk rotor as the mating material was maintained at a sufficiently small level, a sufficiently high friction coefficient and good rust-removing property were obtained. Have been. This effect is more apparent from comparison with the comparative example in FIG.

That is, as shown in FIG. 2, Comparative Example 1 uses ceramic fibers F having an average fiber diameter of 0.9 μm, which is smaller, and an average fiber length of 40 μm, which is relatively short. According to this, the amount of wear of the mating material is smaller, but at the same time, the coefficient of friction is slightly reduced and the rust-removing property is significantly reduced. Conversely, the average fiber diameter is 5.5 μm, which is larger, and the average fiber length is 16 μm.
Comparative Example 2 using ceramic fiber G having a relatively long length of 0 μm
However, the friction coefficient and the rust-removing property are further enhanced, but the wear of the mating material is increasing more than the increase. Although the average fiber diameter is 5.0 μm, in Comparative Example 3 using the ceramic fiber H whose average fiber length is as short as 30 μm, the wear of the mating material still tends to be large.

Further, the ceramic fibers I were used in Examples 3 and 6.
The average fiber diameter is 3.
0 μm, the average fiber length is 100 μm, but the flakes are not removed, and the content ratio of the flakes is as large as about 35%, whereby the bulk density is 0.1%.
It is as small as 8 g / cm ³ . In Comparative Example 4 in which 5% by weight of the ceramic fiber I was blended, the ceramic fiber C (the content of the flakes was about 10% and the bulk density was 0.2%).
Compared with Example 3 in which 5) was used in the same amount, the wear amount of the mating material was smaller and the rust-removing property was hardly changed.
In particular, the obtained coefficient of friction is low. In Comparative Example 5 in which the amount of the ceramic fiber I was increased to 11% by weight, a sufficient friction coefficient could be secured, but the wear amount of the mating material was increased.

In Comparative Example 6 in which no ceramic fiber was blended, the friction coefficient was ensured by increasing the amount of the abrasive (zirconium silicate), but this abrasive had almost no effect of removing rust of the mating material. No rust-removing property is obtained because there is no rust.

Therefore, from the results of this evaluation test, in order to suppress the wear of the mating material to a sufficiently small level, and to ensure a sufficiently high friction coefficient and good rust-removing property, it is necessary to use a fiber base material. The ceramic fiber used as a part has a fiber diameter that is sufficiently small but not too small (average fiber diameter 1.0 to 5.0 μm) and an appropriate fiber length (average fiber length 50 to 150 μm). In addition, scaly substances, which are exfoliated fiber surface layers generated during the production of ceramic fibers, are removed as much as possible, and the content of the scaly substances is low and the bulk density is relatively high (0.20 g / cm ^3). It turns out that it is preferable to use the above.

By the way, the friction material of the present invention has been mainly described by taking a pad for a disc brake as an example. However, the present invention is not limited to this. The present invention can be similarly applied to other friction materials used in a dry friction engagement device such as lining or clutch facing. Also,
The type and composition of the fibrous base material and the like can be variously changed without being limited to the above embodiment.

[0059]

As described above, the friction material according to the first aspect of the present invention is a friction material comprising an abrasive ceramic fiber, a resin binder, and a filler. The fiber has an average fiber diameter of 1.0 to 5.0 μ
m, the average fiber length is 50 to 150 μm, the bulk density is 0.20 to 0.40 g / cm ³ , and the content is 1 to 10% by weight based on the whole friction material. Is what you do.

A friction material according to a second aspect of the present invention is a friction material comprising a fiber base material containing abrasive ceramic fibers, a resin binder, and a filler, wherein the abrasive ceramic fibers are average fibers. The diameter is 1.0 to 5.0 μm, the average fiber length is 50 to 150 μm, and the ratio of the scale-like material obtained by peeling the surface layer of the fiber to the entire fiber is 30% or less, and the entire friction material is Is contained at a ratio of 1 to 10% by weight.

Therefore, according to this friction material, an abrasive ceramic fiber is blended as a part of the fiber base material, and the abrasive ceramic fiber has a sufficiently small fiber diameter and an appropriate fiber length. Because we use
The scaly material, which is a product of peeling the fiber surface layer that inhibits the abrasion, as well as the friction coefficient and the rust-removing property can be enhanced by its abrasion while suppressing the wear of the mating material to a small extent. Is removed, and a material whose content ratio is small or whose bulk density is relatively large and moderate is used, so that its abrasiveness can be more effectively exhibited, and in particular, the friction coefficient can be further improved. That is, according to the friction material of the present invention, there is an effect that the wear of the mating material can be sufficiently reduced, and a higher friction coefficient and better rust-removing property can be secured.

[Brief description of the drawings]

FIG. 1 is a table showing the composition of a friction material (disk brake pad) according to an example of the present invention and the results of an evaluation test thereof.

FIG. 2 is a table showing the composition of a friction material (disk brake pad) according to a comparative example and the results of an evaluation test thereof.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-60225 (JP, A) JP-A-8-296678 (JP, A) JP-A-8-283076 (JP, A) JP-A-7- 18092 (JP, A) JP-A-6-346045 (JP, A) JP-A-7-19272 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16D 69/02 C08J 5 / 14 CFB C09K 3/14 520

Claims (2)

(57) [Claims] 1. A friction material comprising a fiber base material containing an abrasive ceramic fiber, a resin binder and a filler, wherein the abrasive ceramic fiber has an average fiber diameter of 1.0 to 1.0.
5.0 μm, the average fiber length is 50 to 150 μm, the bulk density is 0.20 to 0.40 g / cm ³ , and the content is 1 to 10% by weight based on the whole friction material. Characteristic friction material. 2. A friction material comprising a fiber base material containing abrasive ceramic fibers, a resin binder, and a filler, wherein the abrasive ceramic fibers have an average fiber diameter of 1.0 to 1.0.
5.0 μm, the average fiber length is 50 to 150 μm, and the ratio of the scale-like material obtained by peeling the surface layer of the fiber to the entire fiber is 30% or less, and 1 to 10 to the entire friction material. A friction material characterized in that it is contained in a proportion of weight%.