JPH09144792A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the wear resistance without substantially increasing the wear of a counter material. SOLUTION: A friction material is formed of a fiber base material containing the fibrilized aramid fiber and the novoloid fiber of the mean fiber diameter of <=23μm and consisting of 1-10vol. part novoloid fiber relative to 10vol. part aramid fiber at the ratio of 6-20vol.% relative to the whole composition of the friction material, a resin binder, and the filler such as the friction adjusting agent. Because the novoloid fiber of small fiber diameter is blended at the prescribed ratio, the wear resistance of the friction material (non-steel type) in which the aramid fiber is used as the main component of the fiber main material can be improved without substantially increasing the wear of the counter material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material such as a disc brake pad and a drum brake lining used in vehicles, industrial machines and the like.

[0002]

Friction materials such as disc brake pads and drum brake linings used in automobiles are
It plays an important role in converting kinetic energy into heat energy by frictionally engaging with the disc rotor and brake drum, which are its counterparts. Therefore, not only is the friction material required to have excellent wear resistance, but it is also necessary to have a sufficiently high coefficient of friction, and moreover, heat is constantly generated during braking, and the temperature is high. Stable friction characteristics with little change in friction coefficient are required. Furthermore, it is also necessary that there is no aggressiveness to the mating material, that noise (abnormal noise, squeaking) does not occur during braking, and the like, and the characteristics required for the friction material cover many items.

Therefore, conventionally, in order to satisfy these various characteristics, the friction material is constructed as a composite material. That is, the friction material is a fiber base material that forms its skeleton,
It is generally composed of a resin binder for binding and holding the fiber base material and various fillers such as a friction modifier dispersed and filled in a matrix of these fibers and the binder. A phenol resin, which is a thermosetting resin, is generally used as the resin binder. Further, as the filler, mainly barium sulfate for improving wear resistance and heat resistance, body filler such as calcium carbonate, graphite for adjusting and stabilizing the friction coefficient, solid lubricant such as molybdenum disulfide, Friction modifiers such as cashew dust and abrasives such as zirconium oxide are used.

Here, the fibrous base material, which is a fibrous component, forms the skeleton of the friction material, imparts appropriate porosity to it, and imparts strength and elasticity to the entire friction material. It is the most important material that greatly influences its main characteristics. And asbestos fiber (asbestos) was used as such a fiber base material in the old days.
However, it turns out that this asbestos fiber is not good for your health,
Therefore, in recent years, fiber materials other than asbestos fibers have been used as fiber base materials for friction materials.

An example thereof is a so-called semi-metallic friction material using steel (carbon steel) fiber as the main material of the fiber base material.
It is disclosed in Japanese Patent No. 7985. Such a semi-metallic friction material has not only excellent heat resistance but also excellent wear resistance and a relatively high friction coefficient because the steel fiber has high hardness. However, on the other hand, it has a drawback that it is heavy, rusts, and moreover, it easily attacks and abrades an opponent material made of the same kind of steel. Since squealing during braking is also likely to occur,
In the one disclosed in the above publication, the squeal is improved by mixing graphite and metal sulfide in a specific ratio and ratio.

Therefore, recently, a so-called non-steel friction material, which does not use steel fiber as a fiber base material or has a small amount of steel fiber even if it is used, is a mainstream of friction material instead of a semi-metallic friction material. Has become. In this non-steel friction material, the fiber base material is lightweight, and although it is an organic fiber, aramid fiber (aromatic polyamide fiber) having particularly high strength and relatively excellent heat resistance Is generally used as the main material. Further, the aramid fiber is also characterized in that it can be fibrillated, and thereby the retention of the filler component can be enhanced, so that the aramid fiber is fibrillated, that is, pulp-like aramid. Fiber is commonly used. Since aramid fibers alone do not provide sufficient performance to substitute asbestos fibers, other fiber substrates include potassium titanate fibers or whiskers, inorganic fibers such as ceramic fibers, copper fibers, brass fibers, etc. Non-ferrous metal fibers, etc. are used in an appropriate combination.

Regarding the non-steel type friction material using the fiber base material containing such an aramid fiber as a main material, for example, Japanese Patent Laid-Open Nos. 2-298575 and 5-58 can be used.
No. 1277, Japanese Patent Laid-Open No. 6-129455 and the like are disclosed in various modes or modifications. The materials disclosed in these publications specifically relate to the type and blending of solid lubricants with the object of improving wear resistance.

As an asbestos substitute material composed of organic fibers for use in industrial materials, in addition to the above aramid fibers, for example, novoloid fibers which are cured products of novolac type phenol resin fibers are known. The novoloid fiber is used for various purposes such as a composite material because of its excellent heat resistance, chemical resistance, heat insulation and the like. As one of its applications, there is an example of a clutch facing which is a semi-mold type friction material obtained by winding a fiber roving to which a compounded rubber is adhered in a ring shape, and then heat and pressure molding the novoloid fiber. Used as a fiber to form rovings. However, since the novoloid fiber is not so high in strength, it is not actually used in a composition-based friction material that is a normal friction material such as a disc brake pad and a drum brake lining.

[0009]

As described above, as the friction material for the disc brake pad or the like, aramid fiber,
In particular, a non-steel friction material using a fiber base material containing fibrillated aramid fiber as a main material is general. According to such a friction material, it is possible to obtain various excellent characteristics such as being lightweight, not rusting, having less aggressiveness against the mating material, and having less noise (noise). Further, according to the aramid fiber, since the fibrils are entangled with the powdery filler component and also have the function of holding it, the handleability at the time of mixing the material components of the friction material is good, and the material component after molding is also good. It is possible to obtain a uniform friction material free from segregation.

However, this non-steel type friction material tends to have low wear resistance because the aramid fiber which is the main material of the fiber base material is relatively soft or has relatively low hardness. And this wear resistance is one of the most important characteristics originally required for friction materials, and in recent years, braking conditions have become more and more severe with the increasing speed and output of automobiles. Has become particularly important.

Therefore, in order to improve its wear resistance,
Various technical means have been investigated and tried mainly from the viewpoint of composition. A typical means thereof is to use a relatively large amount of solid lubricant such as graphite or molybdenum disulfide, which is a filler, as described in the above publications. However, if the amount of the solid lubricant is increased, the wear resistance is improved due to its lubricity, but at the same time, the friction coefficient is also lowered. Therefore, this kind of means had its limits.

Further, although many other means for improving the wear resistance improve the wear resistance itself of the friction material,
On the contrary, the aggression against the mating material was increased, and the amount of wear was remarkably increased. Further, such an increase in wear of the mating member is not only unfavorable, but also the progress of the wear may cause judder vibration. Therefore, aramid fiber as a fiber substrate, especially,
In the friction material containing the fibrillated aramid fiber, there is still a strong demand for improvement in its wear resistance.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a friction material capable of improving wear resistance without substantially increasing the amount of wear of the mating material. To do.

[0014]

Means for Solving the Problems As a result of various investigations and studies for solving the above-mentioned problems, the present inventors have added the above-mentioned novoloid fibers in a predetermined ratio to aramid fibers. Therefore, it is possible to effectively improve the wear resistance, however, the blending of novoloid fibers tends to increase the wear of the mating material, but by using novoloid fibers having a fiber diameter of a certain value or less, It was found and confirmed that it does not substantially increase the wear of the.

That is, the friction material according to claim 1 comprises fibrillated aramid fibers and novoloid fibers having an average fiber diameter of 23 μm or less and consisting of 1 to 10 parts by volume with respect to 10 parts by volume of the aramid fibers. The fiber base material is contained in a proportion of 6 to 20% by volume with respect to the entire friction material component, a resin binder made of a phenol resin, and a filler such as a friction modifier.

As described above, in this friction material, the novoloid fiber having a small diameter of a predetermined value or less is mixed in a fixed ratio to the fiber base material containing the fibrillated aramid fiber. As can be seen from the above, the wear resistance can be effectively improved without substantially increasing the wear amount of the mating material. Further, since the total compounding ratio of the fibrillated aramid fiber and the novoloid fiber is set to an appropriate constant range, other properties as a friction material can be maintained well.

Although it is only speculated that abrasion resistance can be improved by blending novoloid fibers,
It is thought to be due to the following reasons. That is, since the novoloid fiber and the resin binder are made of the same phenol resin, they have high mutual adhesiveness and strongly bond in the friction material. Therefore, by these novoloid fibers and the resin binder, the friction material component such as the powdery filler is firmly bonded and held in the friction material, and the abrasion of the friction material due to the dropping of the component is suppressed. As a result, it is considered that the wear resistance is improved. In addition, the reason why the wear amount of the mating material does not substantially increase due to the use of the small diameter novoloid fiber having an average fiber diameter of 23 μm or less is that the novoloid fiber has a relatively high hardness, and therefore, the mating property of the novoloid fiber causes Grind the material, but if the fiber diameter is relatively small,
Because the polishing by it becomes more uniform and smooth,
As a result, it is considered that the amount of wear of the mating material does not substantially increase. However, these are just speculations, and it is considered that the action of the aramid fiber is actually deeply involved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The friction material will be described in more detail below.

As described above, in the friction material of the present invention, in addition to pulp-like, that is, fibrillated aramid fibers, a predetermined fiber diameter is used as the fiber base material which is the fibrous component forming the skeleton. The novoloid fiber having is used in combination at a predetermined ratio.

Here, the novoloid fiber is composed of a cured product of a phenol resin, and is generally obtained by melt spinning a phenol resin composed of an addition polycondensation product of phenol and formaldehyde and then subjecting this to a curing reaction. You can Specifically, for example, excess phenol and formaldehyde are reacted under an acidic catalyst to obtain a novolac type phenolic resin, the novolac type resin is melt-spun, and then the obtained uncured novolac type resin fiber is obtained. It can be produced by a method in which formaldehyde is added to and reacted in the presence of an acidic catalyst and then cured. The novoloid fiber thus obtained basically has a chemical structure in which phenol is bound in a three-dimensional network by a methylene group, and because of its amorphous and non-oriented structure, the strength is not very high, It is about the same as rayon and acetate. However, since it is a thermosetting resin, it is infusible, has higher heat resistance than aramid fiber, has excellent chemical resistance, and has low toxicity of combustion gas.

In the present friction material, the novoloid fiber is used to improve its wear resistance. As the shape of the novoloid fiber used, the shape of chopped fiber or milled fiber such as chopped fiber is preferable from the viewpoint of handleability and uniform dispersibility in the friction material, and even in the case of chopped fiber, The average fiber length is preferably about 6 mm or less. However, conversely, if the fiber length is too small, the reinforcing effect as the fiber base material is reduced, so that even in the case of the milled fiber, the average fiber length is preferably about 0.1 mm or more.

Irrespective of such fiber length, as the novoloid fiber, a sufficiently thin fiber having an average fiber diameter of 23 μm or less is used so as not to substantially increase the wear amount of the mating material. To do. That is, there is a certain degree of correlation between the fiber diameter of the novoloid fiber and the amount of wear of the mating material. Generally, the larger the fiber diameter, the more the wear of the mating material tends to increase. Therefore, as a novoloid fiber,
A material having an average fiber diameter of 23 μm or less, which is a practically acceptable level of wear of the mating material and does not substantially increase, is used. Therefore,
The lower limit is not particularly limited, and fine fibers can be used as long as they can be produced technically. However, the lower limit is preferably about 5 μm, which is the limit of mass production.

The novoloid fiber having an average fiber diameter of less than this fixed value is the fibrillated aramid fiber 10
Generally, it is preferable to mix 1 to 10 parts by volume with respect to the parts by volume. Further, in this case, it is preferable that the total amount of the aramid fiber and the novoloid fiber is 6 to 20% by volume with respect to the entire friction material component. That is, if the compounding amount of the novoloid fiber is too small, it is difficult to sufficiently improve the wear resistance in practical use. Therefore, the compounding amount is 1 part by volume or more with respect to 10 parts by volume of the aramid fiber. preferable. However, too much of it tends to increase the wear of the mating material,
Further, it is not preferable because it lowers the fade resistance,
Therefore, it is preferable that the ratio is equal to or less than that of the aramid fiber. Further, regarding the total mixing ratio of the aramid fiber and the novoloid fiber to the entire friction material component, if this is too small, the absolute amount of each of those fiber components will be insufficient, and sufficient strength by the aramid fiber and sufficient by the novoloid fiber It becomes difficult to obtain wear resistance and
On the other hand, if the amount is too large, the fiber component is excellent in heat resistance, but since it is an organic fiber, the heat resistance of the friction material is lowered and the fade resistance is also lowered. Therefore, the total blending amount should be 6 vol% as the lower limit, and 20 vol%
Is preferably the upper limit.

Further, the blending amount of the fibrillated aramid fiber and the novoloid fiber is more preferably 5 to 15% by volume for the aramid fiber and 1 to 10% by volume for the novoloid fiber in the ratio with respect to the whole friction material component. The blending ratio of the novoloid fiber is more preferably 3 to 5% by volume. By such blending, the characteristics of each fiber can be better exhibited, the wear resistance can be improved without increasing the wear of the mating material, and the other friction performance of the friction material is good. Can be maintained at.

Fiber substrates other than these fibrillated aramid fibers and novoloid fibers which are organic fibers, that is, inorganic fibers and metal fibers are the same as conventional ones.

That is, as the inorganic fiber, silicate fiber, alumina fiber, alumina-silica fiber, tyranno fiber, potassium titanate fiber or whisker, carbide or nitride fiber or whisker, magnesium oxide whisker, rock wool, slag. Examples thereof include ceramic fibers such as wool, whiskers, carbon fibers, glass fibers and the like. Further, as the metal fiber, a copper fiber,
Examples include non-ferrous metal fibers such as brass fibers, steel fibers such as steel fibers, and stainless steel fibers.

The inorganic fibers including these metal fibers may be any one or more of them added to the above fibrillated aramid fiber and novoloid fiber,
It can be used as a fiber substrate. However, as the fibers to be used together with those organic fibers, particularly, potassium titanate fibers or whiskers which are excellent in heat resistance and abrasion resistance, and also have little attack on the mating material, and ceramic fibers which are abrasive hard inorganic fibers, and non-ferrous metals. Mention may be made of combinations of metal fibers. According to this combination, the heat resistance lacking in organic fibers can be supplemented mainly by potassium titanate fibers or whiskers, the friction coefficient by ceramic fibers, and the appropriate thermal conductivity by nonferrous metal fibers.

As the fiber base material, steel fibers can also be used, whereby the strength and the like of the friction material can be supplemented. However, in the present friction material using the aramid fiber and the novoloid fiber, it is preferable to mix the friction material to the minimum limit, and it is preferable that the content is 5% by volume or less based on the whole friction material component.

As a resin binder for binding and holding such a fiber base material and a filler, a phenol resin, which is excellent in bonding strength and thermal strength among various thermosetting resins, is used. To be done. Phenolic resin includes phenols such as phenol and cresol and formaldehyde,
It is obtained by reacting with aldehydes such as acetaldehyde, and generally powdery novolac type resin can be used. However, a resol type resin can also be used if necessary. Further, as these phenol resins, modified phenol resins modified with alkylbenzene or the like can also be used.

As the filler, body fillers such as barium sulfate and calcium carbonate, solid lubricants such as molybdenum disulfide, antimony trisulfide and graphite, cashew dust or other organic polymer powder, zirconium oxide and silica. Abrasive agents such as alumina, metal powders such as copper powder, zinc powder, brass powder, etc., mainly for improving thermal conductivity,
Alternatively, other additives for friction adjustment and the like can be used.

The friction material is, for example, a fiber base material containing fibrillated aramid fibers and novoloid fibers in the above-mentioned predetermined ratios, a resin binder made of a phenol resin,
And a filler such as a friction modifier are uniformly mixed, the mixture is preformed, and then the preformed body can be produced by a usual thermoforming method in which the preformed body is heated and pressed.

[0032]

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

FIG. 1 is a table showing the composition (volume%) of the friction materials of Examples 1 to 4 of the present invention, and Comparative Examples 1 and 2 and the evaluation test results. FIG. 2 is a table showing the composition (volume%) of the friction materials of Examples 1 to 9 of the present invention and the evaluation test results (Examples 1 to 4 are reprinted).

[Preparation of Friction Material (Pad)] FIGS. 1 and 2
Friction materials of Examples 1 to 9 of the present invention were produced with the compounding composition (volume%) shown in. Further, for comparison with these examples, friction materials of Comparative Examples 1 and 2 were also produced. The friction materials of these examples and comparative examples are specifically embodied as disc brake pads for automobiles.

<Examples 1 to 4, Comparative Examples 1 and 2> As shown in FIG. 1, the friction materials (disk brake pads) of Examples 1 to 4 and Comparative Examples 1 and 2 are Any of these, a fiber base material containing aramid fibers and novoloid fibers, a resin binder made of a phenol resin that holds the fiber base material together, and dispersed in a matrix of these fiber base materials and resin binders. It is formed from various fillers to be filled. However, in each of these Examples and Comparative Examples, the type of novoloid fiber contained as a part of the fiber base material is variously changed.

More specifically, the fibrous base material, which is a fibrous component forming the skeleton of the friction material, comprises 10% by volume of fibrillated pulp-like aramid fibers, 3% by volume of novoloid fibers, and heat resistance. 10% by volume of potassium titanate whiskers for ensuring strength and wear resistance, 10% by volume of ceramic wool for ensuring heat resistance and friction coefficient, and mainly copper fibers for ensuring thermal conductivity. Three
A mixture with% by volume was used in each example and comparative example. However, in Comparative Example 2, the novoloid fiber was not blended and the amount of the aramid fiber was increased to 15% by volume.
And Therefore, each friction material is formed here as a non-steel friction material that does not include steel fibers.

The resin binder composed of a phenol resin was blended in a proportion of 17% by volume in each of the examples and comparative examples.

As the filler, 17% by volume of cashew dust for adjusting and stabilizing the friction coefficient and 5% by volume of graphite, which is a solid lubricant mainly for improving the wear resistance in the low temperature region and the medium temperature region, are used. And 2% by volume of antimony trisulfide, which is a solid lubricant for improving wear resistance especially in a high temperature range
And 3% by volume of slaked lime for keeping the friction material alkaline and enhancing the rustproof property of the joint surface with the back metal, and 20% by volume of barium sulfate as a constitutional filler were blended in each example and comparative example. . However, in Comparative Example 2, the novoloid fiber was unblended and the aramid fiber was 5% by volume.
The amount of barium sulfate was decreased while the amount was increased, and the respective compounding amounts were 15% by volume and 18% by volume.

Under this blended composition, the type of novoloid fiber was changed to form each friction material. Here, as the novoloid fibers, the following five types of fibers A to E, which are composed of chopped fibers and milled fibers and have different fiber diameters or lengths, were prepared.

(Novoloid fiber) Novoloid fiber A: average fiber diameter 14 μm (average fiber length 6
mm) novoloid fiber B: average fiber diameter 14 μm (average fiber length 0.2 mm) novoloid fiber C: average fiber diameter 20 μm (average fiber length 0.3 mm) novoloid fiber D: average fiber diameter 23 μm (average fiber length 0.3 mm) Novoloid Fiber E: Average Fiber Diameter 33 μm (Average Fiber Length 0.3 mm) Then, in Example 1, the fiber diameter is small and the fiber length is relatively long, and in Example 2, the fiber diameter is equal to the novoloid fiber A. However, the novoloid fiber B having a short fiber length
In Example 3, the fiber length is almost equal to that of the novoloid fiber B, but the novoloid fiber C has a relatively large fiber diameter.
In Example 4, novoloid fibers D having the same fiber length but a larger fiber diameter are respectively added as described above.
It was compounded at a ratio of 3 parts by volume to 10 parts by volume of aramid fiber. On the other hand, in Comparative Example 1, the fiber lengths are equal,
Novoloid fibers E having a larger fiber diameter were mixed in the same proportion, and in Comparative Example 2, no novoloid fibers were mixed.

As described above, friction materials of Examples 1 to 4 and Comparative Example were produced with the same composition of components except that the type of novoloid fiber was changed.

<Examples 5 to 9> In addition to Examples 1 to 4, the friction ratio of Examples 5 to 9 of the present invention was changed by changing the compounding ratio of the aramid fiber and the novoloid fiber, which are organic fibers. A material was produced. Here, as the novoloid fiber, a novoloid fiber A having an average fiber diameter of 14 μm (average fiber length of 6 mm) was used.

As shown in FIG. 2, the friction materials (disc brake pads) of Examples 5 to 9 were the same as those of Examples 1 to 4, and the fiber base containing the aramid fiber and the novoloid fiber was used. Material, a resin binder made of phenolic resin, and various fillers, and other components except for aramid fiber and novoloid fiber, which are organic fiber components of the fiber base material, and barium sulfate, which is a body filler. In each of the Examples, the same proportions as in Examples 1 to 4 are blended. That is, 10% by volume of potassium titanate whiskers, 10% by volume of ceramic wool, 3% by volume of copper fibers as a fiber base material, 17% by volume of phenol resin as a resin binder, and 17% by volume of cashew dust as a filler. 5% by volume of graphite, 2% by volume of antimony trisulfide and 3% by volume of slaked lime are mixed.

In each embodiment, the mixing ratio of the aramid fiber and the novoloid fiber is variously changed.

That is, in Example 5, aramid fiber and novoloid fiber were mixed in a volume ratio of 10: 1. Specifically, the mixing ratio of the aramid fiber is set to 10% by volume, which is the same as in Examples 1 to 4, and the mixing ratio of the novoloid fiber is reduced to 1% by volume.

In Example 6, aramid fibers and novoloid fibers were mixed at a volume ratio of 10: 5. Specifically, the mixing ratio of aramid fiber is also 1
0% by volume and increase the blending ratio of novoloid fiber to 5
It is the volume%.

In Example 7, aramid fibers and novoloid fibers were mixed at a volume ratio of 10:10. Specifically, the mixing ratio of the aramid fiber is 7% by volume, and the mixing ratio of the novoloid fiber is 7% by volume.

Further, in Example 8, the total mixing ratio of the aramid fiber and the novoloid fiber to the whole friction material component was relatively small, and was 6% by volume. Specifically, Example 8 uses 5% by volume of aramid fiber as the fiber base material,
It contains 1% by volume of novoloid fibers. The volume ratio of these is 10: 2.

In Example 9, the total blending ratio of the aramid fiber and the novoloid fiber to the whole friction material component was relatively high, and was 20% by volume. Specifically, Example 9 contains 15% by volume of aramid fiber and 5% by volume of novoloid fiber as the fiber base material. The volume ratio of these is 10: 3.3.

In these examples, the amount of increase or decrease in the amount of aramid fiber and novoloid fiber was adjusted by increasing or decreasing the amount of barium sulfate as a body filler.

The friction materials (disc brake pads) of Examples 1 to 9 and Comparative Examples 1 and 2 having these compounding compositions were prepared by a conventional method of thermoforming. Went as follows. That is, the friction material raw material having the above composition containing the aramid fiber and the novoloid fiber is sufficiently and uniformly mixed with a blender, and then the powder mixture is put into a preforming die, and at room temperature, 200 kg / cm.
A pressure of ² (19.6 MPa) was applied for 1 minute to form a pad-shaped preform of the friction material. Then, the preform of this friction material was set in a thermoforming mold together with a back metal whose surface was previously coated with a phenol resin adhesive, and 400 kg
Thermoforming was performed for 10 minutes at a pressure of 160 ° C./cm ² (39.2 MPa). Then, this was further heat-treated at 250 ° C. for 120 minutes to obtain a friction material as a disc brake pad.

[Evaluation Test] Next, regarding each friction material (disk brake pad) of Examples and Comparative Examples produced by changing the kind of novoloid fiber and changing the composition of aramid fiber and novoloid fiber, An evaluation test was carried out on the wear resistance of and the aggression of the mating material (disk rotor).

Regarding wear resistance, JASO-C406
According to -82, a braking test at the time of the second effect (stable period) after rubbing was performed, and the wear amount of each friction material after 1000 times of braking was measured. Further, the wear rate was calculated from the measured wear amount. The test conditions are as follows. Caliper brake model used: PE54-22V. Inertia: 53.9 kg · m ² . Initial speed: 50km / h. Deceleration: 3 m / s ² . Temperature before braking: 200 ° C.

With respect to the aggressiveness to the mating material (ventilated steel disc rotor having a thickness of 22 mm), the amount of wear of the mating material after 1000 times of braking according to the above braking test was measured.

The wear rate (× 10 ^-5 mm ³ / N · m) and the wear amount (μm) of the mating material for each friction material of the examples and comparative examples are shown in FIGS. 1 and 2. .

[Test Results] As shown in FIG. 1, the friction material (disk brake pad) of Comparative Example 2 in which aramid fiber or the like was mixed as the fiber base material was a conventional general friction material (non-steel type). Correspondingly, according to this, the wear rate is relatively high and is 2.4 × 10 ⁻⁵ mm ³ / N · m. The amount of wear of the mating material (disk rotor) is 12μ.
It is as small as m, and the attacking property against the mating material is well suppressed.

On the other hand, Examples 1 to 9 and Comparative Example 1 in which the novoloid fiber was further mixed as the fiber base material.
The wear rate of each of the friction materials is significantly reduced. That is, the wear resistance of the friction material is effectively improved by blending the novoloid fiber.

However, as a novoloid fiber, a comparative example 1 using novoloid fiber E having a large average fiber diameter
In the friction material of No. 1, the wear rate of the friction material is reduced (1.
4 × 10 ⁻⁵ mm ³ / N · m), on the other hand, the amount of wear of the mating material markedly increased to 21 μm. That is,
Although the wear resistance is improved, at the same time, the aggressiveness against the mating material, which was good, is significantly deteriorated.

On the other hand, in contrast to this Comparative Example 1, Examples 1 to 9 in which thin novoloid fibers A to D having an average fiber diameter of 23 μm or less were used as the novoloid fibers.
In each of the above friction materials, not only the wear rate of the friction material itself is favorably reduced, but also the wear amount of the mating material is reduced, which is as good as the case of Comparative Example 2 in which novoloid fiber is not mixed. Indicates a value. That is, in the examples, the wear resistance of the friction material is effectively improved without substantially increasing the wear amount of the mating material.

In this test result, when the novoloid fibers A and B having the same fiber diameter but different fiber lengths are compared with each other in Example 1 and Example 2, the pad wear rate and the pad wear rate in these are compared. The rotor wear amount is slightly smaller in the case of Example 2 using the novoloid fiber B having a shorter fiber length, but there is almost no difference. In other words, there is no particular tendency between the fiber length of the novoloid fiber and the pad wear rate and rotor wear amount. In addition, even when the examples 1 to 4 and the comparative example 1 are compared with each other, no particular tendency is observed between the fiber diameter of the novoloid fiber and the wear property of the friction material. .

Further, from Examples 5 to 7 in which the mutual mixing ratio of the aramid fiber and the novoloid fiber was changed, the wear rate of Example 5 in which the mutual mixing ratio was 10: 1 in volume ratio was 1 6 × 10 ⁻⁵ mm ³ / N · m, whereas the combined ratio is 10: 5 and 10:10, respectively
The wear rates of the friction materials of Example 6 and Example 7 are almost unchanged, being 1.4 × 10 ⁻⁵ mm ³ / N · m and 1.5 × 10 ⁻⁵ mm ³ / N · m, respectively. , All show low values. Regarding the amount of wear of the mating material, 13 μm in Example 5, 12 μm in Example 6, and 7
Is 14 μm, which is a low value.
Therefore, the mixing ratio of the aramid fiber and the novoloid fiber to each other is 10: 1 to 10 in terms of volume ratio, that is, 1 part of the novoloid fiber to 10 parts by volume of the aramid fiber.
It can be seen that the ratio of 10 to 10 parts by volume is preferable.

Further, according to Examples 8 and 9 in which the total blending ratio of the aramid fiber and the novoloid fiber to the entire friction material component was changed, the friction of Example 8 in which the total blending ratio was 6% by volume. The wear rate of the material is 1.7
The wear rate was × 10 ⁻⁵ mm ³ / N · m, and although this wear rate was significantly smaller than that of Comparative Example 1 in which novoloid fiber was not mixed, it was slightly higher. On the other hand, in the friction material of Example 9 in which the total compounding ratio was 20% by volume, the wear rate was 1.1 × 10 ⁻⁵ mm ³ / N · m, which showed excellent wear resistance. There is. However, if the total blending ratio of the aramid fiber and the novoloid fiber, which are organic fibers, is so large, the heat resistance may be insufficient. Therefore, it is understood that the total compounding ratio of the aramid fiber and the novoloid fiber is preferably 6 to 20% by volume with respect to the entire friction material components, with the limits of Examples 8 and 9.

From this test result, the fibrillated aramid fiber and the novoloid fiber having an average fiber diameter of 23 μm or less and 1 to 10 parts by volume with respect to 10 parts by volume of the aramid fiber were used as the whole friction material component. For 6 to 20
By blending as a fiber base material in a volume% ratio,
It can be seen that the wear resistance can be improved without substantially increasing the wear amount of the mating material.

Although the friction material of the present invention has been described by taking the disc brake pad as an example, the present invention is not limited to the disc brake pad, and is not limited to the disc brake pad. The same can be applied to other friction materials such as linings and clutch facings. Further, the kind and the blending ratio of the fiber base material are not limited to those in this embodiment, and can be variously changed.

[0065]

As described above, the friction material according to claim 1 has the fibrillated aramid fiber and the average fiber diameter of 23 μm or less, and the friction material is 1 with respect to 10 parts by volume of the aramid fiber.
A fibrous base material containing 10 to 10 parts by volume of novoloid fibers in a proportion of 6 to 20% by volume with respect to the entire friction material component;
It contains a resin binder made of a phenol resin and a filler such as a friction modifier.

Therefore, in this friction material, since the novoloid fiber which is the phenol resin fiber is blended in a predetermined ratio to the fiber base material containing the aramid fiber, its abrasion resistance should be greatly improved. You can In addition, since the novoloid fiber having a small fiber diameter is used, the abrasion of the mating material is not increased. That is, according to this friction material, there is an effect that the wear resistance can be improved without substantially increasing the wear amount of the mating material.

[Brief description of the drawings]

FIG. 1 is a graph showing the composition (volume%) of the friction materials (disc brake pads) of Examples 1 to 4 and Comparative Examples 1 and 2 of the present invention, and their friction materials. It is a table which shows the result of an evaluation test.

FIG. 2 is a blending composition (volume%) of a friction material (disc brake pad) according to Examples 1 to 9 of the present invention.
FIG. 6 is a table showing the results of evaluation tests of these friction materials.

Claims (1)

[Claims] 1. A fibrillated aramid fiber, 23 μm
A novoloid fiber having the following average fiber diameter and comprising 1 to 10 parts by volume with respect to 10 parts by volume of the aramid fiber,
A friction material comprising a fibrous base material in a proportion of 6 to 20% by volume with respect to the entire friction material component, a resin binder made of a phenol resin, and a filler such as a friction modifier.