JP5578391B2 - Non-asbestos friction material - Google Patents

Description

  The present invention relates to a non-asbestos-based friction material, and more particularly to a non-asbestos-based friction material that is a friction material that does not use asbestos and is used for a brake pad for a vehicle.

  In general, non-asbestos-based friction materials used for vehicle brake pads, etc. have a large decrease in the coefficient of friction at high temperatures of 500 ° C or higher. Alternatively, it is known to use a sintered friction material.

Conventionally, a brake friction material comprising a metal fiber, a heat-resistant organic fiber, a predetermined fiber base material, a thermosetting resin, and a friction modifier is known (for example, see Patent Document 1).
In addition, such a friction material is known in which the hole system and the cumulative porosity are adjusted to improve the fade resistance and reduce the opponent attack property (see, for example, Patent Document 2).
JP 63-266231 A Japanese Patent Laid-Open No. 11-322959

However, in the friction materials as described above, those containing iron fibers and sintered friction materials have a problem of being inferior in wear at 500 ° C. or less and in friction coefficient stability.
Further, in the conventional friction material, it cannot be said that the decrease in the friction coefficient in a high temperature region exceeding 500 ° C. is necessarily small, and the stability of the friction coefficient at 500 ° C. or less is not sufficient. Furthermore, there is room for further improvement in the wear characteristics at high temperatures, especially the opponent attack.

The present invention has been made in view of such problems of the prior art, and the object of the present invention is to suppress the reduction of the friction coefficient in the high temperature range, the stability of the friction coefficient, and the reduction of the opponent attack. The object is to provide a non-asbestos-based friction material that is balanced .

  As a result of intensive studies to achieve the above object, the present inventors have achieved the above object by using an aggregate fiber made of a predetermined metal fiber and, if necessary, a predetermined high temperature lubricating fiber. The present inventors have found that this can be done and have completed the present invention.

That is, the non-asbestos-based friction material of the present invention is composed of metal fibers having a hardness of 85 to 145 Hv, a tensile strength of 400 to 600 N / mm ^2, an elongation of 20 to 49%, and a melting point of 1450 ° C. or higher. A non-asbestos-based friction material containing at least one aggregate fiber selected from the group consisting of titanium (Ti), titanium alloy, nickel (Ni), and nickel alloy , an organic fiber, and a binder. ,
Friction formed shallower than 200 μm from the surface of the non-asbestos-based friction material after high-temperature friction that causes the non-asbestos-based friction material to reach 700 ° C. by braking under the condition of speed reduction from 144 km / hr to 80 km / hr. The amount of the aggregate fiber contained in the deteriorated layer is 80 to 100% by mass of the amount before the high-temperature friction.

  As will be described later, in the non-asbestos-based friction material, the “aggregate function value” is a value determined by the tensile strength of at least one of the aggregate fiber and the high-temperature lubricating fiber and the content of the fiber. The “value” is a value determined by the Vickers hardness and content of at least one of the aggregate fiber and the high temperature lubricating fiber.

According to the present invention, since aggregate fibers made of predetermined metal fibers are used, and predetermined high-temperature lubricating fibers are used as necessary, suppression of friction coefficient decrease at high temperatures , stability of friction coefficient, It is possible to provide a non-asbestos-based friction material that balances the reduction of opponent attack .

Hereinafter, the non-asbestos-based friction material of the present invention will be described in detail.
As described above, the non-asbestos-based friction material of the present invention contains an aggregate fiber, an organic fiber, and a binder, and the aggregate fiber has a hardness of 85 to 145 Hv, 400 to 600 N / mm. ^It consists of metal fibers having a tensile strength of ^{2 and} an elongation of 20-49% and a melting point of 1450 ° C. or higher.

Here, the aggregate fiber has a function of forming a skeleton of the non-asbestos-based friction material, and plays a role of suppressing a decrease in the friction coefficient, particularly a decrease in the friction coefficient at a high temperature exceeding 500 ° C.
In addition, although the fiber diameter and fiber length of this aggregate fiber are not specifically limited, It is preferable to set it as 30-100micrometerphi * 1-5mm.

In the present invention, the aggregate fiber may be composed of a metal fiber having the above-described characteristics. Examples of the metal fiber include titanium (Ti), titanium alloy, nickel (Ni), nickel composite. mention may be made of gold or we made metal fibers, these Ru used alone or as a mixture in the present invention.
The characteristics of the titanium alloy and the nickel alloy are that they have a hardness of 85 to 350 Hv, a tensile strength of 300 to 1000 N / mm ² , and an elongation of 10 to 50%.

The organic fiber has a function of reinforcing the friction material and is preferably heat-resistant, and examples thereof include an aramid fiber, a phenol fiber, and an acrylic fiber.
The binding material has a function of binding various components to each other, and examples thereof include a phenol resin, a polyimide resin, and a furan resin.

In the non-asbestos-based friction material of the present invention, the metal fiber other than the above-described aggregate fiber has a hardness of 80 Hv or less, a tensile strength of 150 to 400 N / mm ^{2, and} an elongation of 10% or more. High temperature lubricating fibers made of metal fibers having a melting point of 700 to 1100 ° C. can be blended.
By blending such a high-temperature lubricating fiber, it is possible to significantly reduce the opponent attack in a high temperature range.

  That is, in the non-asbestos-based friction material of the present invention, when a metal fiber that is a constituent material is a metal fiber (aggregate fiber) that can maintain strength even at high temperatures and a metal fiber that has a lubricating effect (high-temperature lubrication fiber). Although the reduction of the friction coefficient at a high temperature of 500 ° C. or higher is effectively suppressed, the skeleton of the friction material can be maintained and the rapid increase in wear of both the friction material and the rotor can be suppressed.

Here, the maintainability of such a friction material skeleton can be evaluated by the following aggregate function values.
This “ aggregate functional value” is the tensile strength at room temperature (N / mm ² ) of the metal fiber composed of at least one of the aggregate fiber and the high-temperature lubricating fiber, both of which are metal fibers, and the content of these metal fibers. The value obtained by dividing the product of (vol%) by 100 is shown.
For example, when the metal fiber is composed of aggregate fiber, the aggregate fiber amount is 20 vol%, and the tensile strength (room temperature) of the aggregate fiber is 300 N / mm ² , the aggregate function value is 20 × 300 ÷ 100 is 60.

In the non-asbestos-based friction material of the present invention, the aggregate function value is preferably 30 or more.
When the aggregate function value is less than 30, the aggregate fiber cannot hold the friction material at a high temperature of 500 ° C. or higher, and the fiber diameter of the aggregate fiber existing in the friction deteriorated layer is less than 20% before the high temperature friction. As a result, the skeleton of the friction material cannot be maintained, and the friction coefficient may decrease at high temperatures.

On the other hand, the opponent aggression property in a high temperature range can be evaluated by the following hardness function value.
This “hardness functional value” is the Vickers hardness (Hv) at room temperature of the metal fibers composed of aggregate fibers and / or high-temperature lubricating fibers, both of which are metal fibers, and the content (vol%) of these metal fibers. The value obtained by dividing the product of and by 100.
For example, when the metal fiber portion is composed of aggregate fiber, the aggregate fiber amount is 20 vol%, and the hardness of the aggregate fiber is 90 Hv, the hardness function value is 18 by 20 × 90 ÷ 100.

In the non-asbestos-based friction material of the present invention, the hardness function value is preferably 10 or less.
When the hardness function value exceeds 10, the hardness of the metal fiber is large and the total amount is also increased, so that the opponent attack is increased, and the metal fiber falls off as a wear component, so that the rotor and the friction material are separated. By interposing, the frictional material wear may also deteriorate.

  In the non-asbestos-based friction material of the present invention, when both the aggregate fiber value and the high temperature lubricating fiber are included as the metal fiber fiber, the aggregate function value is 30 or more, and the hardness function value is 10 or less. It is preferable that the metal fiber content is included at a rate of 10 to 60% by mass, of which the aggregate fiber accounts for 5 to 40% by mass and the high temperature lubricating fiber accounts for 5 to 20% by mass.

If the metal fiber content is less than 10% by mass, the decrease in the friction coefficient at high temperatures cannot be suppressed, and if it exceeds 60% by mass, the decrease in the friction coefficient at high temperatures can be suppressed. The opponent's aggression increases, the wear of the rotor and the friction material increases, and abnormal noise and squeal are liable to occur.
If the aggregate fiber is less than 5% by mass, it is not possible to suppress the decrease in the friction coefficient at high temperatures, and if it exceeds 40% by mass, it is possible to suppress the decrease in the friction coefficient at high temperatures. The other party's aggression increases, wear of the rotor and friction material increases, and abnormal noise and squealing are likely to occur.
In addition, if the high-temperature lubricating fiber is less than 5% by mass, the function of the lubricating fiber may not be achieved, abnormal noise or squealing is likely to occur, and the lubricating performance at high temperatures is reduced. Rotor wear due to aggregate fibers and abrasives may increase. If it exceeds 20% by mass, the lubrication performance becomes excessive and the retention of the coefficient of friction at high temperatures may be hindered.

The metal fiber constituting the high-temperature lubricating fiber as described above is not particularly limited as long as the above characteristics are satisfied, but typically, a fiber made of copper (Cu) or a copper alloy can be exemplified. In the present invention, fibers made of copper (Cu) or a copper alloy are used.

The non-asbestos-based friction material of the present invention can contain inorganic fibers, organic fillers, fillers, lubricants, abrasives and the like in addition to the above-described components.
Examples of inorganic fibers include rock wool and glass fibers. Examples of organic fillers include rubber and dust. Examples of fillers include barium sulfate, mica, and calcium oxide. Examples of lubricants include graphite, carbon, and metal. Examples of abrasives such as sulfides include zirconia, alumina, and mica.

Further, the non-asbestos-based friction material of the present invention is such that the fiber diameter of the aggregate fiber present in this layer is high-temperature friction in a friction-degraded layer formed shallower than 200 μm from the surface of the non-asbestos-based friction material after high-temperature friction. It has the previous 100-20% size.
That is, even after high-temperature friction, the fiber diameter of the aggregate fiber is not so small. Therefore, the aggregate fiber sufficiently functions as a skeleton-forming material, and the high temperature of the non-asbestos-based friction material. It can be seen that the friction coefficient decrease in the region is sufficiently suppressed.

Furthermore, non-asbestos friction material of the present invention, in the friction degradation layer, the fibers of the aggregate fibers present in this layer is, that have a quantity of 80 to 100 wt% before the high temperature friction.
That is, even after high temperature friction, the amount of the aggregate fiber does not decrease so much. From this, the aggregate fiber sufficiently functions as a skeleton-forming material, and the high temperature of the non-asbestos-based friction material. It can be seen that the friction coefficient decrease in the region is sufficiently suppressed.

  Specifically, high-temperature friction can be performed by holding and rotating a rotating body such as a rotor with a non-asbestos-based friction material formed in a pad shape at 700 ° C. For example, as a speed conversion of an automobile, It can be performed under the condition of decelerating from 144 km / h to 80 km / h.

From the viewpoint of such aggregate characteristics, titanium (Ti) and titanium alloys are good. For example, titanium (Ti) having a fiber diameter of 30 μm does not change its fiber diameter even after high-temperature friction, and the friction The deteriorated phase also exists only in a range of about 30 μm or less from the friction material surface.
Nickel (Ni) and nickel alloys can also be used. For example, in nickel (Ni) having a fiber diameter of 50 μm, the fiber diameter after high-temperature friction is only reduced to about 10 μm. The friction deterioration phase is also in a range of about 200 μm or less from the friction material surface. However, when nickel is used as an aggregate fiber, the effect as an aggregate function is high, but it is preferable not to use it together with sulfide because of the relationship between nickel and sulfide.

In the non-asbestos-based friction material of the present invention, the blending amount of various components is not particularly limited as long as the above-mentioned characteristics after high-temperature friction are satisfied, but aggregate fiber is 5 to 40% by mass, as necessary It is preferable to blend the high-temperature lubricating fiber at a ratio of 5 to 20% by mass.
When the amount of aggregate fiber is less than 5% by mass, the skeleton cannot be maintained, and the skeleton formation function during high-temperature friction may not be achieved. On the other hand, if it exceeds 40% by mass, abnormal noise and squeal are likely to occur, and wear may increase.
If the blending amount of the high-temperature lubricating fiber is less than 5% by mass, the function of the lubricating fiber may not be achieved, abnormal noise and squeal are likely to occur, and wear may be increased. Moreover, when it exceeds 20 mass%, the frame | skeleton formation function at the time of high temperature friction may be inhibited, and the friction coefficient at the time of high temperature may fall.

Next, the manufacturing method of the non-asbestos-based friction material of the present invention will be described.
After the non-asbestos-based friction material of the present invention is uniformly mixed with the above-described various components, it is preformed, and after the back metal and the preform are inserted into the mold, it is then molded by a heat and pressure molding method. After manufacturing by heat treatment or after mixing uniformly, after inserting the mixed powder and the back metal into the mold, after molding by the hot press molding method, or after molding by the hot press molding method, It can be manufactured by performing a heat treatment.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

After uniformly mixing the various components shown in Table 1, after preforming, and then inserting the back metal and the preform into the mold, after molding by the heat and pressure molding method, heat treatment is performed, A friction material was produced.
In Table 1, titanium 28 mass%, 14 mass% and 7 mass% are 10 vol%, 5 vol% and 2.5 vol%, nickel 28 mass% is 10 vol%, copper 14 mass% and 7 mass% are 5 vol%, respectively. % And 2.5 vol%, stainless steel 28 mass% is equivalent to 10 vol%, steel 28 mass% is equivalent to 10 vol%, and is measured from the relationship between the amount of friction material components used, density and weight of friction material, and density. can do.

[Performance evaluation]
(1) Friction coefficient change during fading The friction material of each example was subjected to the following test conditions using a 1/5 size brake dynamo scale tester. Specifically, the treatment was carried out in the order of lapping 1 → roughing 2 → main test, the friction coefficient in the main test was measured, and the obtained results are shown in Table 2.

・ Rice 1
Pre-braking temperature: 120 ° C
First braking speed: 60km / h
Final braking speed: 0km / h
Deceleration: 0.3G
Number of braking: 200 times

・ Rice 2
Pre-braking temperature: 80 ° C
First braking speed: 130km / h
Final braking speed: 0km / h
Deceleration: 0.6G
Number of braking: 10 times

・ Main test temperature before braking: 60 ℃
Brake initial speed: 144 km / h
Final braking speed: 80km / h
Deceleration: 0.5G
Braking interval: 22 seconds Number of braking cycles: Conducted until the friction material reaches 700 ° C

(2) Amount of wear After performing a test piece test based on JASO C406: 2000, the amount of wear of the friction material of each example was measured. The obtained results are shown in Table 3.

(3) Surface observation of friction material after fading For the friction materials of Example 1, Example 2, Example 3 and Comparative Example 3, each was subjected to a fading treatment under the following test conditions, and then the cross section was subjected to an optical microscope. Observed at. These optical micrographs are shown in FIGS. 1, 2, 3 and 4, respectively.

(A) Test conditions Tests were performed using a gray cast iron rotor and the friction material of Example 1 as a pad. The speed was reduced from 144 km / h to 80 km / h. The initial temperature was 60 ° C. and the deceleration was 0.5 G.

(B) Test Results In the friction material of Example 1, when the temperature was 700 ° C., the number of braking was 6 and the friction coefficient μ was 0.30. Further, the rotor thickness reduction was 0.041 mm, and the pad thickness reduction was 1.40 mm.
In the friction material of Example 2, when the temperature was 700 ° C., the number of braking was 8 and the friction coefficient μ was 0.19. Further, the rotor thickness reduction was 0.038 mm, and the pad thickness reduction was 1.33 mm.
In the friction material of Example 3, when the temperature was 700 ° C., the number of braking was 7, and the friction coefficient μ was 0.23. Further, the rotor thickness reduction was 0.028 mm, and the pad thickness reduction was 0.87 mm.
On the other hand, in the friction material of Comparative Example 3, when the temperature was 700 ° C., the number of braking was 9 and the friction coefficient μ was 0.17. Further, the rotor thickness reduction was 0.031 mm, and the pad thickness reduction was 0.79 mm.

  From the above results, Examples 1 to 3 can suppress the decrease in the friction coefficient at high temperature from the function of sufficiently fulfilling the skeleton function by blending the aggregate fiber as compared with Comparative Example 3, It can be seen that by optimizing the blending of the material fibers and the high-temperature lubricating fibers, it is possible to achieve both the suppression of the friction coefficient decrease at high temperatures and the wear reduction of the pad and rotor.

  1 to 4, the thickness of the deteriorated layer and the state of the aggregate fiber and the lubricating fiber after high-temperature friction can be confirmed from cross-sectional observation. By controlling the composition of the aggregate fiber and the lubricating fiber, the thickness of the deteriorated layer, the fiber diameter of the aggregate fiber in the deteriorated layer can be controlled, and the friction coefficient reduction at high temperature and the pad, It can be seen that it is possible to reduce the wear of the rotor.

(4) Analysis of amount of metal on friction material surface, etc. Further, the friction materials of Example 1, Example 2, Example 3 and Comparative Example 3 were each subjected to a fade treatment under the above test conditions, and then the friction material. Surface metal component analysis and fluorescent X-ray line analysis were performed to analyze the maintenance rate of the amount of metal and the amount of metal fibers on the surface of the friction material.
These analysis results are shown in Table 4 and Table 5, respectively. Table 4 shows the maintenance rate of the amount of the metal fiber component used relative to the amount of the entire metal component used in the friction material. However, the component contained as components other than powder and fiber may also be detected. Table 5 shows the retention rate when measuring an object that is considered as close to the fiber as possible.

FIG. 5 shows the results of fluorescent X-ray surface analysis performed on the metallic content before and after the evaluation.
Among the respective metal components, those having a high peak value are components detected on the surface, mainly metal fibers. However, the high detection value of iron after the evaluation is a result of detection of an adhering rotor component due to wear. Tables 4 and 5 show the quantitative values of these metal fibers.

In the metal component analysis in Table 4, the amount of metal component on the surface of the friction material including the deteriorated layer after the evaluation was compared with the amount of metal component before evaluation, and expressed in terms of maintenance rate. In contrast, Example 3 and Comparative Example 4 are increasing.
This is because the deteriorated layer contains iron, which is a wear powder component of the rotor, and the amount of metal component detected before evaluation is reduced by detecting the iron component. It is considered that some copper deteriorated at a high temperature, was included in the deteriorated layer, and increased because the copper component was detected.

  On the other hand, Table 5 measured the thing considered to be close to the metal fiber as much as possible, and described the maintenance rate. In Examples 1 to 3, it is detected that the aggregate fiber contained in the frictionally deteriorated layer formed shallower than 200 μm after the evaluation contains a fiber amount of 80% or more with respect to the metal fiber amount before the evaluation. It was done. However, in Comparative Example 3, the copper used as the aggregate fiber contains a fiber amount of 80% or more, but as is clear from Table 4, it also functions as a high temperature lubricating fiber and is included in the deteriorated layer. This confirms that the reduction of the friction coefficient is promoted as a lubricating function.

  From the above analysis results, the state of the aggregate fiber and the lubricating fiber after high-temperature friction can be confirmed. By controlling the blending of aggregate fiber and lubricating fiber, the thickness of the deteriorated layer, the fiber diameter of the aggregate fiber in the deteriorated layer, and the amount of fiber can be controlled, and the reduction in friction coefficient at high temperatures is suppressed. It can be seen that it is possible to reduce wear of the pad and the rotor.

2 is an optical micrograph showing the surface of a friction material after fading. 2 is an optical micrograph showing the surface of a friction material after fading. 2 is an optical micrograph showing the surface of a friction material after fading. 2 is an optical micrograph showing the surface of a friction material after fading. It is a chart which shows the result of having performed fluorescent X-ray surface analysis about metallic quantity.

Claims (6)

Hardness of 85~145Hv, 400~600N / mm ² tensile strength, have an elongation of 20-49%, a melting point Ri consists 1450 ° C. or more metal fiber, titanium (Ti), titanium alloys, nickel ( A non-asbestos-based friction material containing at least one aggregate fiber selected from the group consisting of Ni) and a nickel alloy , an organic fiber, and a binder,
Friction formed shallower than 200 μm from the surface of the non-asbestos-based friction material after high-temperature friction that causes the non-asbestos-based friction material to reach 700 ° C. by braking under the condition of speed reduction from 144 km / hr to 80 km / hr. A non-asbestos-based friction material, wherein a fiber amount of the aggregate fiber contained in the deteriorated layer is 80 to 100% by mass of the amount before the high-temperature friction. Furthermore, a high-temperature lubricating fiber comprising a copper fiber (Cu) or a copper alloy fiber having a hardness of 80 Hv or less, a tensile strength of 150 to 400 N / mm ^2, an elongation of 10% or more, and a melting point of 700 to 1100 ° C. The non-asbestos-based friction material according to claim 1, comprising:   The aggregate function value of the aggregate fiber or the metal fiber composed of the aggregate fiber and the high-temperature lubricating fiber is 30 or more, and the hardness function value is 10 or less. The non-asbestos-based friction material according to 1 or 2.   The metal fiber content is included at a rate of 10 to 60% by mass, wherein the aggregate fiber accounts for 5 to 40% by mass and the high temperature lubricating fiber accounts for 5 to 20% by mass. Item 4. The non-asbestos-based friction material according to Item 3.   The non-asbestos-based friction material according to any one of claims 1 to 4, wherein the aggregate fiber is included at a rate of 5 to 40% by mass.   The non-asbestos-based friction material according to any one of claims 2 to 5, wherein the high-temperature lubricating fiber is contained at a ratio of 5 to 20% by mass.

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