JP3228096B2 - Manufacturing method of 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 method for producing a friction material used for clutch facings, brake pads, and the like of automobiles, industrial machines, railway vehicles, and the like.

[0002]

2. Description of the Related Art The performance required of a friction material includes excellent wear resistance, a high friction coefficient, and a stable friction coefficient. It is difficult to satisfy these performances with a single material, and the friction material is composed of a composite material in which many materials are mixed.

[0003] Such friction materials can be roughly classified as follows. (1) Cork, cellulose: There are simple substances, but most are impregnated with resin and thermoformed. (2) Woven: String impregnated with glass, brass wire and made of asbestos, organic fiber, etc. with resin (3) Semi-mold: impregnated with resin, filled with rubber material, and thermoformed (4) Resin mold: Asbestos, glass fiber, etc. as base material, phenol (5) Rubber mold: A resin using rubber instead of resin in resin mold (6) Semi-metallic: Among resin molds, the base material is metal fiber ( 7) Sintered Metallic: Sintered metal powder (8) Cermet: Sintered ceramic powder and metal powder For automobiles, semi-molded and resin Rudo based friction material is frequently used. For example, in clutch facing of a car, a string is formed from a fiber base material such as glass fiber, and a friction modifier, a filler, a phenol resin, a compounded rubber, and the like are attached to the string and wound into a disk to form a preform. . It is manufactured by a semi-molding method in which it is thermoformed in a mold and further subjected to processes such as heat treatment, polishing, rust prevention treatment, and perforation.

[0004] Brake pads and the like are manufactured by a resin molding method in which a fiber base of short fibers is mixed with a friction modifier, a filler, a phenol resin, a rubber and the like, molded in a mold, and heat-treated. However, in a conventional friction material, under severe conditions in which the sliding surface is at a high temperature of 350 to 500 ° C., a liquid substance or a gaseous substance is generated by thermal decomposition of a binder or the like, which is formed as a fluidized bed. A fade phenomenon in which the friction coefficient decreases due to the presence on the moving surface may occur. Also,
Friction vibration occurs due to the change in the speed dependence of the friction coefficient,
Sometimes judder and squealing occurred.

Accordingly, Japanese Patent Application Laid-Open Nos. Sho 59-113038 and
Japanese Patent Publication No. -21528 and Japanese Examined Patent Publication No. 7-23465 describe a friction material that forms a thermally stable carbonaceous material by carbonizing a part of the binder etc. by heat treatment at a high temperature in a non-oxidizing atmosphere. A manufacturing method is disclosed. According to the friction material manufactured in this manner, since the generation of decomposition products during sliding at high temperature is small, the fade phenomenon is less likely to occur, and stable characteristics are exhibited.

[0006]

However, the friction material heat-treated in a non-oxidizing atmosphere has a problem that the wear resistance is significantly reduced. The reason for this is that the porosity increases due to volume shrinkage due to carbonization of the binder and the organic fibers. For example, a phenol resin widely used as a binder for a friction material is a resin which is less shrunk by carbonization among various resins.
Literature shows that the firing rate at 50 ° C. is about 52%, and the shrinkage in this case is about 48%. When the porosity increases in this way, the strength of the friction material decreases, and the wear resistance decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and aims to achieve both the prevention of a fade phenomenon and the improvement of wear resistance by suppressing volume shrinkage due to heat treatment in a non-oxidizing atmosphere. With the goal.

[0008]

Means for Solving the Problems A first method for solving the above problems is described below.
Features of the method of manufacturing the friction material of the invention, the fiber substrate friction adjustment
Contains sizing agent, inorganic filler and phenolic resin binder
A molded body is formed, and the molded body is 2 to 50 k in a non-oxidizing atmosphere.
Baking by heating to 350 to 700 ° C under a pressure of g / cm ²
By doing so, the porosity is set to 25% or less .

The method of manufacturing a friction material according to the second invention is characterized in that a fiber base material, a friction modifier, an inorganic filler, and phenol are used.
Forming a molded body containing a resin-based binder; heating the molded body to 350 to 700 ° C. in a non-oxidizing atmosphere ;
Pores are impregnated with a liquid binder and then fired to reduce the porosity to 2
5% or less .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, it is desirable that the amount of organic fibers in the fiber base material is regulated to 0 to 10% by volume and the amount of organic substances in the friction modifier is regulated to 0 to 5% by volume . Thereby, volume shrinkage when heat-treated in a non-oxidizing atmosphere is suppressed, and the porosity can be easily reduced to 25% or less.

[0011] Organic fibers include cotton, soup, rayon, polyester fiber, acrylic fiber, aramid fiber,
Examples include phenol fibers and the like, and examples of organic friction modifiers include cashew dust, rubber dust, and cork powder. These organic substances can be used in a non-oxidizing atmosphere.
Since the volume shrinks due to the decomposition and carbonization by the heat treatment at 50 to 700 ° C., the volume shrinkage can be suppressed by regulating the content as described above, and the porosity can be reduced to 25% or less. As described above, the porosity greatly affects the abrasion resistance. When the porosity exceeds 25%, the abrasion resistance rapidly decreases, so that the porosity is set to 25% or less.

The fibers other than the organic fibers used for the fiber base include metal fibers such as steel fibers, copper fibers and brass fibers, inorganic fibers such as glass fibers, alumina fibers, silicon nitride fibers and slag wool, and carbon fibers. And the like. Metal fibers are effective in improving strength, fading resistance and abrasion resistance.
It is preferable to configure so as to contain. In addition, since inorganic fibers are effective in improving the strength and stabilizing the friction coefficient, it is desirable to contain 5 to 20% by volume in the friction material. The fiber base material is contained in the friction material so as to be generally 10 to 50% by volume.

Examples of the friction modifier other than the organic substance include solid lubricants such as graphite and molybdenum disulfide powder, and abrasives such as alumina and magnesium oxide.
Examples of the inorganic filler include barium sulfate, calcium carbonate, clay, talc, lead sulfate, and tripolystone (siliceous limestone). Generally, the friction modifier is contained in the friction material in an amount of 10 to 50% by volume, and the inorganic filler is contained in the friction material in an amount of 0 to 40% by volume.

Examples of the phenolic resin used for the binder include a novolak type phenolic resin, a resol type phenolic resin, a melamine-modified phenolic resin, and a urea-modified phenolic resin.
-30% by volume. The non-oxidizing atmosphere may be a vacuum atmosphere, a nitrogen gas atmosphere, or an inert gas atmosphere. And the heat treatment temperature is 3
If the temperature is lower than 350 ° C., the carbonization of the binder or the like is insufficient, and the fading phenomenon easily occurs.
If the heat treatment is performed at a temperature higher than ℃, the carbonization proceeds excessively and the wear resistance decreases.

As a molding method of the molded article, the above-described semi-molding method or resin molding method can be used.
In the first invention of claim 1, and a molded body pressed during the heat treatment under a non-oxidizing atmosphere. By doing so, the pores generated by the progress of carbonization are crushed, and as a result, the porosity can be reduced to 25% or less.

In the case of the first invention, it is not necessary to regulate the amounts of the organic fibers and the organic friction modifier as described above .
If the porosity is regulated as described above , the porosity can be more easily increased to 25%.
% Or less. The pressure during heat treatment is 2
５０50 kg / cm ² . If the pressure is lower than 2 kg / cm ² , the effect of pressurization is small and it is difficult to reduce the porosity to 25% or less. If the pressure exceeds 50 kg / cm ² , cracks occur in the friction material and the wear resistance deteriorates conversely. May be.

The materials used and other manufacturing conditions are described above.
It is the same as doing . In the second invention according to claim 2,
After the molded body is heated to 350 to 700 ° C. in a non-oxidizing atmosphere and fired, it is impregnated with a liquid binder and fired. By doing so, the binder is filled in the pores generated during firing in a non-oxidizing atmosphere, so that the porosity can be reduced to 25% or less. In order to efficiently impregnate the pores with the binder, the impregnation is preferably performed in a negative pressure atmosphere or a pressurized atmosphere.

The materials used and other manufacturing conditions are the same as described above . Although the above-described production methods of the first and second inventions are effective even when used alone, the porosity can be more easily reduced to 25 by performing the respective methods in combination.
% Or less.

[0019]

EXAMPLES The present invention will be described more specifically with reference to Reference Examples, Examples and Comparative Examples. In addition, “%” of the contents described below all means volume%.

[0020]

[Table 1] ( Reference Example 1) As shown in Table 1, 8% of steel fiber, 5% of aramid fiber, 5% of cashew dust, 10% of potassium titanate fiber as inorganic fiber, 16% of graphite, and as a modifier also serving as an abrasive Was mixed with 28% of magnesium oxide, 28% of barium sulfate as another filler, and 20% of phenol resin, and the mixture was filled in a mold and heated under pressure to form a molded body.

Next, the compact is placed in a nitrogen gas atmosphere for 60 minutes.
Baking was performed at 0 ° C. for 2 hours, and the surface was polished to obtain a brake pad. In the brake pad obtained in this reference example, since the aramid fiber and the cashew dust were each as small as 5%, the volume shrinkage during firing was small, and the porosity was 20%. With respect to this brake pad, the minimum friction coefficient and the amount of wear at the time of the first fade were measured using a bench tester, and the results are shown in FIGS. 1 and 2. The test was performed by JASO-C406
It is equivalent to -82. ( Reference Example 2) As shown in Table 1, except that 18% of graphite and 31% of barium sulfate were used without using cashew dust.
A molded body was formed in the same manner as in Reference Example 1 and heat-treated in the same manner to produce a brake pad. The porosity of this brake pad was 17%, which was even smaller than in Reference Example 1.

The minimum coefficient of friction and the amount of wear were measured in the same manner as in Reference Example 1, and the results are shown in FIGS. 1 and 2. (Comparative Example 1) As shown in Table 1, a molded article was formed in the same manner as in Reference Example 1 except that aramid fiber was used at 12%, cashew dust was used at 10%, and barium sulfate was used at 16%. To produce a brake pad. The porosity of this brake pad is 28%, which is 25% or more.

The minimum coefficient of friction and the amount of wear were measured in the same manner as in Reference Example 1, and the results are shown in FIGS. (Evaluation) From FIGS. 1 and 2, it can be seen that the minimum friction coefficient at the time of the first fade is almost 0.3 with almost no difference, and that it is excellent in fade resistance. In addition, it can be seen that the brake pad obtained in Comparative Example 1 has the same fade resistance as the Reference Example, but the wear amount is significantly increased. On the other hand, in Reference Example 1 and Reference Example 2, the amount of wear decreases in this order, and it is clear that the smaller the porosity, the better the wear resistance. (Example 1 ) A molded product was formed in the same manner as in Reference Example 1 with the composition of Comparative Example 1 in Table 1. Next, in a nitrogen gas atmosphere, 5 kg /
baking at 600 ° C. for 2 hours while applying a surface pressure of ² cm ² ,
The surface was polished to obtain a brake pad. The porosity of this brake pad was 23%.

The minimum coefficient of friction and the amount of wear were measured in the same manner as in Reference Example 1. The results are shown in FIGS. (Example 2 ) A molded article was formed in the same manner as in Reference Example 1 with the composition of Comparative Example 1 in Table 1, and heat-treated in the same manner as in Reference Example 1. Next, this friction material itself was immersed in a liquid phenol resin, and the friction material was impregnated with the phenol resin in a vacuum atmosphere of 1/10 of atmospheric pressure. The impregnation amount is 8%.

Then, the impregnated phenol resin was cured by baking at 600 ° C. for 1 hour in a nitrogen gas atmosphere and polished to produce a brake pad. The porosity of this brake pad was 22%. Then, the minimum coefficient of friction and the amount of wear were measured in the same manner as in Reference Example 1, and the results are shown in FIGS. (Evaluation) From FIG. 3 and FIG. 4, it can be seen that the minimum coefficient of friction at the time of the first fade is almost 0.3 with almost no difference, and is excellent in fade resistance. Example 1 and Example
The brake pad obtained in Comparative Example 1 was superior to the brake pad obtained in Comparative Example 1 in terms of abrasion resistance despite being manufactured with the same composition as Comparative Example 1. It is clear that this is due to the reduced porosity, and it is possible to reduce the porosity even in the composition of Comparative Example 1 by baking under pressure or impregnating the phenol resin after baking. We can see that we can do it. It was formed similarly shaped body as in Reference Example 1 with the formulation of Reference Example 1 (Example 3) Table 1. Next, in a nitrogen gas atmosphere, 10 kg
Baked at 600 ° C. for 1 hour while applying a surface pressure of / cm ² , and the surface was polished to obtain a brake pad. The porosity of this brake pad was 19%.

Then, the minimum coefficient of friction and the amount of wear were measured in the same manner as in Reference Example 1, and the results are shown together with Reference Example 1 in FIGS. (Example 4) Table 1 to form a molded body in the same manner as in Reference Example 1 with the formulation of Reference Example 1, except that a temperature of 550 ° C. was heat-treated in the same manner as in Reference Example 1. Next, the friction material itself was immersed in a liquid phenol resin, and the pores were impregnated with the phenol resin in a vacuum atmosphere of 1/10 of the atmospheric pressure. The impregnation amount is 5%.

The impregnated phenol resin was cured by baking at 550 ° C. for 1 hour in a nitrogen gas atmosphere, and polished to produce a brake pad. The porosity of this brake pad was 18%. Then measure the minimum friction coefficient and wear amount in the same manner as in Reference Example 1. The results together with Reference Example 1 shown in FIGS. (Evaluation) From FIG. 5 and FIG. 6, it can be seen that the minimum friction coefficient at the time of the first fade is almost 0.3 with almost no difference, and is excellent in fade resistance. Example 3 and Example
Brake pads obtained in 4 is excellent in wear resistance than Example 1 despite prepared in the same formulation as in Reference Example 1. This is apparently due to the reduced porosity.

That is, in the first invention or the second invention ,
The fiber base contains organic fibers in an amount of 0 to 10% by volume of the entire friction material.
As a friction modifier, organic matter is 0 to 5% by volume of the entire friction material.
It can be seen that the porosity can be further reduced and the abrasion resistance can be improved by performing the combination in combination, as compared with the case of performing each independently.

[0029]

According to the method for producing a friction material of the present invention, a friction material which does not easily cause a fade phenomenon and has excellent wear resistance can be produced easily, stably and reliably.

[Brief description of the drawings]

FIG. 1 is a bar graph showing a minimum friction coefficient at the first fade of the brake pads manufactured in Reference Example 1, Reference Example 2, and Comparative Example 1.

FIG. 2 is a bar graph showing the amount of wear of the brake pads manufactured in Reference Example 1, Reference Example 2, and Comparative Example 1.

[3] Example 1 is a bar graph showing the minimum friction coefficient at the time of first fading brake pads prepared in Examples 2 and Comparative Example 1.

[4] Example 1 is a bar graph showing the amount of wear of the brake pads prepared in Example 2 and Comparative Example 1.

FIG. 5 is a bar graph showing the minimum coefficient of friction at the time of the first fade of the brake pads manufactured in Example 3 , Example 4 and Reference Example 1.

FIG. 6 is a bar graph showing the wear amount of the brake pads manufactured in Example 3 , Example 4, and Reference Example 1.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI // C08L 61:00 C08L 61:00 (72) Inventor Junichi Saito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 56) References JP-A-59-113038 (JP, A) JP-A-5-70610 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/14 C09K 3/14 F16D 69/02 C08L 61/00-61/34

Claims (3)

(57) [Claims] 1. A fiber base material, a friction modifier and an inorganic filler.
Forming a molded article containing a phenolic resin-based binder;
Under the pressure of 2-50kg / cm ² in non-oxidizing atmosphere
The porosity is increased by heating to 350 to 700 ° C and firing.
A method for producing a friction material, wherein the friction material is 25% or less . 2. A fiber base material, a friction modifier, and an inorganic filler.
A molded body containing a phenolic resin-based binder is formed, and the molded body is heated to 350 to 700 ° C. in a non-oxidizing atmosphere and fired.
And then impregnated with a liquid binder in the pores and then fired
A porosity of 25% or less . 3. An organic fiber is used as the fiber base material for the entire friction material.
0 to 10% by volume, and the friction modifier contains an organic substance
The composition according to claim 1, wherein 0 to 5% by volume of the whole material is contained.
The method for producing a friction material according to claim 2 .