JPH08145099A - Friction material for brake - Google Patents

Abstract

PURPOSE: To restrain opposite partner attacking performance during thermal hysteresis while the necessary coefficient of friction is maintained. CONSTITUTION: In a brake friction material containing fiber base material, resin binding agent and various adding agents, at least a part of hard particles (grinding material 3) composed of inorganic substance smong the adding agents is covered on its surface by a resin covering layer 4 being low in heat resistance than the resin binding agent. When heat acts on the friction face of the friction material, a covered resin layer 4 to cover the surface of the hard particles (grinding material 3) melts or thermally cracks prior to the resin binding agent, and the hard particles (grinding material 3) promptly drop out of the friction face of the friction material. Thus opposite partner attacking ability can be restrained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a friction material for a brake. INDUSTRIAL APPLICABILITY The friction material for a brake of the present invention can be suitably used for a disc brake pad as a brake material for automobiles.

[0002]

2. Description of the Related Art Conventionally, for a disc brake pad as a brake material for automobiles, a fiber base material made of organic fiber, inorganic fiber or metal fiber is bonded with a resin binder such as a thermosetting resin to adjust friction and wear. Friction materials for brakes to which various additives such as lubricants, solid lubricants and abrasives are added are used.

For example, JP-A-64-83936 discloses a friction material for a disc brake pad, a fiber base material made of non-ferrous metal fiber such as brass or copper or glass fiber, and a resin bond made of phenol resin. It is disclosed that the agent and various additives such as cashew dust, granular graphite, barium sulfate powder and silica powder are used. The above-mentioned various additives are mainly added to adjust the friction coefficient and wear resistance of the friction material, and particularly hard particles made of an inorganic material such as barium sulfate powder or silica powder have a friction coefficient of the friction material. It is an important additive for improving abrasion resistance. Further, the inorganic fibers and the metal fibers as the base fibers also play an important role in improving the friction coefficient of the friction material.

Further, Japanese Patent Application Laid-Open No. 4-306289 discloses a friction material containing copper fibers as a friction modifier.

[0005]

By the way, when the frequency of use of the brake increases, such as when traveling on a long downhill, the brake temperature rises, the coefficient of friction decreases, and the braking effectiveness decreases. . this is,
This is because the organic substances contained in the friction material cause thermal decomposition to generate gas or liquid, and lubricate the friction surface.

However, when the friction material receives a thermal history due to the above-mentioned fade phenomenon, even if the friction material was not hit by the rotor due to the balance between the organic material and the inorganic material until then, the thermal decomposition of the organic material caused the thermal decomposition of the inorganic material on the friction surface. Becomes a rich state, and it becomes difficult to form an organic transition film (protective film) on the rotor surface. Therefore, hard particles made of inorganic substances remaining on the friction surface, inorganic fibers and metal fibers can make the opponent material (rotor) more aggressive. growing. As a result, the rotor is unevenly worn, so that there is a problem in that a difference in wall thickness of the rotor grows and brake vibration occurs during braking.

On the other hand, since the copper fiber added as a friction modifier has high ductility, it is softened by heat during braking and extends and spreads on the friction surface of the friction material. When the copper layer spreads on the friction surface of the friction material in this way, wear powder, Fe powder generated from the rotor surface, and the like are easily incorporated into the copper layer. Then, uneven wear of the rotor progresses due to Fe powder or the like adhering to the friction surface, and the problem of brake vibration during braking occurs as described above.

The present invention has been made in view of the above circumstances, and suppresses the opponent's aggressiveness and suppresses the generation of brake vibration during braking while maintaining the friction coefficient required as a brake friction material. It is a technical subject to be solved to provide a friction material for a brake capable of achieving this.

[0009]

A friction material for a brake according to claim 1 for solving the above-mentioned problems is a friction material for a brake, which comprises a fiber base material, a resin binder and various additives.
At least a part of the hard particles made of an inorganic material among the above additives is characterized in that the surface thereof is coated with a resin coating layer having lower heat resistance than the resin binder.

The heat resistance lower than that of the resin binder means that the resin binder melts or decomposes at a temperature lower than that of the resin binder.
The friction material for brakes according to claim 2 which solves the above-mentioned subject is a friction material for brakes which contains a fiber base material, a resin binder, and various additives, and at least one copy of the above-mentioned fiber base material is partially. It is characterized by having a strength-reduced portion whose strength is reduced.

According to a third aspect of the present invention, there is provided a friction material for a brake, which includes a fiber base material, a resin binder, and various additives, and is a sintered powder made of copper and graphite. It is characterized by including.

[0012]

In the friction material for a brake according to the first aspect, at least a part of the hard particles made of an inorganic material out of the additives added for improving the friction coefficient and the wear resistance is more heat-resistant than the resin binder. Since its surface is coated with a low resin coating layer, when heat is applied to the friction surface of the friction material, the resin coating layer coating the surface of the hard particles is melted or decomposed before the resin binder, Hard particles quickly fall off from the friction surface of the friction material. Therefore, even if high heat is applied to the friction surface of the friction material due to a fade phenomenon and the organic substances such as the resin binder are thermally decomposed, the hard particles whose surface is coated with the resin coating layer quickly fall off from the friction surface. Therefore, the balance between the organic substance and the inorganic substance on the friction surface is maintained, and it is possible to prevent the opponent's aggressiveness from increasing while maintaining a high friction coefficient.

In the friction material for a brake according to claim 2, since at least a part of the fiber base material has a strength-reduced portion in which the strength is partially lowered, the fiber base material causes friction of the friction material. When exposed to the surface, it breaks at the strength-reduced portion and falls off.
Therefore, if the strength-reduced portion is formed on at least a part of the inorganic fiber or the metal fiber in the fiber base material, high heat is applied to the friction surface of the friction material due to a fade phenomenon or the like, and an organic material such as a resin binder is formed. Even if the tip of the inorganic fiber or the metal fiber is exposed to the friction surface due to the thermal decomposition of, since the inorganic fiber or the metal fiber having the above-mentioned strength-reduced portion is broken and falls off from the friction surface, the organic matter and the inorganic matter on the friction surface are Balance is maintained,
It is possible to prevent the opponent's aggressiveness from increasing while maintaining a high friction coefficient.

In the brake friction material according to the third aspect, since the sintered powder containing copper and graphite is contained, the graphite constituting the sintered powder present on the friction surface is softened by heat, and copper A lubricating coating is formed on the contact surface with the mating material. The presence of this lubricating coating can prevent copper from being softened by heat and extending and spreading on the friction surface of the friction material.
It becomes difficult for Fe powder and the like generated from the rotor surface to be taken into copper. Further, even if Fe powder or the like generated from the rotor surface adheres to the lubricating coating, the Fe powder and the like fall off from the friction surface together with the coating. On the other hand, the copper forming the above-mentioned sintered powder existing on the friction surface contributes to the improvement of the friction coefficient. Therefore, the opponent's aggressiveness can be suppressed while maintaining a high friction coefficient.

[0015]

【Example】

(Embodiment 1) The disc brake pad according to the present embodiment shown in the perspective view of FIG. 1 comprises a back metal 1 and a friction material 2 joined to the surface of the back metal 1. The friction material 2 includes an organic fiber (aramid fiber) and an inorganic fiber (potassium titanate fiber, glass fiber) as a fiber base material, a thermosetting resin (Si modified phenol) as a resin binder, and an additive. Organic filler (cashew dust), inorganic filler (barium sulfate), metal powder (copper powder), solid lubricant (graphite, molybdenum disulfide) and abrasive (Zr
It is composed of SiO ₄ , particle size 1 μm, and Mohs hardness: 8). The composition of the friction material 2 is as shown below.

Aramid fiber: 10% by weight Potassium titanate fiber: 8% by weight Glass fiber: 8% by weight Si-modified phenol: 20% by weight Cashew dust: 12% by weight Barium sulfate: 15% by weight Copper powder: 10% by weight Graphite: 7% by weight molybdenum disulfide: 5% by weight ZrSiO ₄ : 5% by weight Then, the abrasive 3 included in the friction material 2 is 70% of the total amount of the abrasive 3 on the surface of the abrasive 3, as shown in FIG. , A resin coating layer made of straight phenol having a lower heat resistance than Si-modified phenol as a resin binder (film thickness: about 1
μm) 4 is coated.

The disc brake pad according to this embodiment was manufactured as follows. First, the resin coating layer 4 was formed on the surface of the abrasive 3 by adding and mixing 5 wt% of the liquid resin to the abrasive. A mixture of the abrasive 3 having the resin coating layer 4 and the abrasive not having the resin coating layer in a predetermined ratio, an organic fiber, an inorganic fiber, a resin binder, and an organic filler. Then, the inorganic filler, the metal powder and the solid lubricant were mixed at a predetermined ratio, and the mixture was compression molded at a pressure of 6.5 MPa to obtain a crude material. Then, this rough material is treated with 19.6MP
a, the friction material 2 was formed by heat compression molding into a brake pad shape under conditions of 165 ° C. This friction material 2 at 280 ° C,
After post-curing under the condition of 3 hours and polishing the surface, it was bonded to the backing metal 1 to complete a disc brake pad.

Comparative Example 1 A disc brake pad according to Comparative Example 1 was manufactured in the same manner as in Example 1 except that the resin coating layer was not formed on the surface of the abrasive. (Evaluation) With respect to the disc brake pads according to the above Example 1 and Comparative Example 1, the mating material aggressiveness was evaluated. This evaluation uses a full size dynamometer as a testing machine,
Hydraulic pressure: 4.9 × 10 ⁶ Pa, while applying braking for 20 minutes, the rotor rotation speed: 900 rpm, the test time: 50 hours after the test, the rotor wall thickness difference growth amount was measured. .

The results are shown in FIG.
The disc brake pad according to the present embodiment 1 in which the resin coating layer 4 is formed on 0% is far more opponent than the disc brake pad according to the comparative example 1 in which the resin coating layer is not formed on the surface of the abrasive. It can be seen that the material aggressiveness has decreased. Further, the friction coefficient of the disc brake pad according to the present example was 0.37, and the friction coefficient of the disc brake pad according to the comparative example was 0.38, and the friction coefficient required for the brake pad was maintained.

In the first embodiment, the kind, particle size and addition ratio of the abrasive 3, and the ratio of forming the resin coating layer 4 on the surface of the abrasive 3 are not particularly limited, and the abrasive 3 itself. According to the hardness, the type of fibrous base material and other additives, the ratio of addition, etc., various settings can be made within a range in which the friction coefficient required for the friction material 2 can be maintained and the opponent aggressiveness can be suppressed to a low level. Is possible. Examples of the abrasive material 3 include ZrO ₄ (Mohs hardness 7), MgO (Mohs hardness 6), Al ₂ O ₃ (Mohs hardness 9), and the like, in addition to ZrSiO ₄ used in Example 1 above. Hard particles made of an inorganic material having a Mohs hardness of 6 or more can be used. Further, when the particle size of the abrasive 3 becomes large, the aggressiveness against the opponent becomes large without being subjected to heat history, and it tends to be difficult to be discharged as abrasion powder. On the other hand, when the particle size of the abrasive 3 becomes smaller, the effect of improving the friction coefficient as an abrasive tends to be lost. Therefore, the particle size of the abrasive 3 is preferably 1 to 50 μm. Further, when the proportion of the resin coating layer 4 formed on the surface of the abrasive 3 increases, the amount of the abrasive 3 remaining on the friction surface after being subjected to the heat history decreases, so that the friction coefficient required for the friction 2 can be maintained. Tends to disappear. On the other hand, when the ratio of forming the resin coating layer 4 on the surface of the abrasive 3 becomes small, the effect of suppressing the opponent attack tends to be lost. Therefore, the ratio of the resin coating layer 4 formed on the surface of the abrasive 3 is preferably 10 to 90% of the total amount of the abrasive. However, when the particle size of the abrasive 3 is as large as about 25 μm or more, the effect of improving the friction coefficient is great, so that it is possible to form the resin coating layer 4 on all the surfaces of the abrasive 3.

The type of the resin coating layer 4 is not particularly limited as long as it is a resin having lower heat resistance than the resin used as the resin binder. In addition to the straight phenol resin used in Example 1 above, a thermosetting resin such as a polyester resin, an epoxy resin or a melamine resin, or a thermoplastic resin such as a vinyl chloride resin or a methacrylic resin can be appropriately used. The film thickness of the resin coating layer 4 may be a film thickness that allows the abrasive 3 to fall off from the surface of the friction material 2 when it is subjected to a heat history, and may be about 1 to 10 μm.

Further, the composition of the friction material 2, the kind of the fiber base material and the kind of the resin binder are not particularly limited to those shown in the above Example 1, and other additives can be added appropriately.
When hard particles made of an inorganic material are added as other additives, it goes without saying that the resin coating layer 4 can be appropriately formed on the surface of the hard particles according to the opponent attack of the hard particles.

Furthermore, in the above-mentioned Example 1, when the inorganic fiber or the metal fiber is used as the base fiber, the strength lowering portion is formed in these fibers as in Example 2 described later, so that the heat history It is possible to further reduce the opponent's aggressiveness over time. (Example 2) In the disc brake pad according to this example, the friction material 2 is the same as in Example 1 except that the organic fiber (aramid fiber) and the inorganic fiber (ceramic fiber fiber diameter: 300 μm) as the fiber base material are Mohs hard. 9) 5
And a thermosetting resin (Si modified phenol) as a resin binder, an organic filler (cashew dust) as an additive, an inorganic filler (barium sulfate), a metal powder (copper powder), a solid lubricant (Graphite, molybdenum disulfide)
And an abrasive (MgO). The composition of the friction material 2 is as shown below.

Aramid fiber: 10% by weight Ceramic fiber: 16% by weight Si-modified phenol: 20% by weight Cashew dust: 12% by weight Barium sulfate: 15% by weight Copper powder: 10% by weight Graphite: 7% by weight Molybdenum disulfide: 5% % By weight MgO: 5% by weight Then, the inorganic fiber 5 contained in the friction material 2 has a structure shown in FIG.
As shown in (1), a large number of constricted portions 51 having a constricted diameter of 100 μm are formed at intervals of about 100 μm as strength-reduced portions.

The disc brake pad according to this example was manufactured as follows. First, the constricted portion 51 was formed in the inorganic fiber 5 by machining such as cutting. The inorganic fibers 5 in which the constricted portions 51 are formed, the organic fibers, the resin binder, the organic filler, the inorganic filler, the metal powder, the solid lubricant, and the abrasive in a predetermined ratio. And the mixture was compression molded at a pressure of 6.5 MPa to obtain a crude material. Then, this crude material was treated with 19.6 MPa, 165
The friction material 2 was formed by heat compression molding into a brake pad shape under the condition of ° C. This friction material 2 was post-cured at 280 ° C. for 3 hours, surface-polished, and then bonded to the backing metal 1 to complete a disc brake pad.

Comparative Example 2 A disc brake pad according to Comparative Example 2 was manufactured in the same manner as in Example 2 except that the constricted portion was not formed in the inorganic fiber. (Evaluation) With respect to the disc brake pads according to the above-mentioned Example 2 and Comparative Example 2, the mating material aggressiveness was evaluated in the same manner as above.

As shown in the results of FIG. 5, the disc brake pad according to the second embodiment in which the constricted portion 51 is formed in the inorganic fiber 5 is the disc brake according to the comparative example 2 in which the constricted portion is not formed in the inorganic fiber. It can be seen that the attacking property of the opponent material is much smaller than that of the pad. Further, the friction coefficient of the disc brake pad according to the present example was 0.37, and the friction coefficient of the disc brake pad according to the comparative example was 0.37, and the friction coefficient required for the brake pad was maintained.

In Example 2, the inorganic fiber 5 was used.
Type, fiber diameter, constriction diameter of constricted portion 51, and proportion of the total amount of inorganic fibers forming constricted portion 51 are not particularly limited, and hardness of inorganic fiber 5 itself, other fiber base materials and additives It is possible to set various values according to the type, the addition ratio, etc. within a range in which the friction coefficient required for the friction material 2 can be maintained and the opponent aggressiveness can be suppressed to be small. If the constricted portion 51 formed in the inorganic fiber has an excessively large constricted diameter, the constricted portion 51 does not easily break off and fall off during heat history, and the effect of suppressing the opponent's aggression cannot be obtained. It is preferable that the fiber diameter of the fiber forming the constricted portion 51 is 50% or less.

In the second embodiment, an example in which the constricted portion is formed as the strength-reduced portion has been described, but the strength-reduced portion is not particularly limited as long as it has a shape and a partially reduced strength. Further, the composition of the friction material 2 and the types of the fiber base material, the resin binder and the additive are not particularly limited to those shown in the above-mentioned Example 2. When other inorganic fibers or metal fibers are used as the fiber base material, it is needless to say that the strength-reduced portion can be appropriately formed in these fibers as well. However, when an organic fiber is used as the fiber base material, it is not necessary to form the strength-reduced portion because the organic fiber has a low opponent attacking property.

Furthermore, when hard particles made of an inorganic material are used as the additive in the above-mentioned Example 2, the surface of the hard particles is heat-cured having a lower heat resistance than the resin binder as in the above-mentioned Example 1. By forming the resin coating layer made of a conductive resin, it is possible to further reduce the opponent attacking property during heat history. Further, by forming the resin coating layer on the surface of the inorganic fiber or the metal fiber having the strength-reduced portion, it can be easily broken at the strength-reduced portion and fall off from the friction surface. It is possible to further reduce the sex.

(Embodiment 3) In the disc brake pad according to the present embodiment, the friction material 2 is the same as that in the above Embodiment 1.
It has a blending composition shown in.

[0032]

[Table 1] The disc brake pad according to this example was manufactured as follows. First, copper powder (average particle size of about 100 μm) and graphite powder (average particle size of about 10 μm) are mixed, and N ₂
In a mixed gas atmosphere of H ₂ and H ₂ , pressure: 9.8 × 10 ⁵
Sintered at Pa, temperature: 800 ° C. for 1 hour. This sintered product was crushed into fine particles, and a sintered powder made of copper and graphite having an average particle diameter of about 100 μm was prepared. Then, each compounding agent was mixed in the composition shown in Table 1, and this mixture was mixed with 2.0MP.
Compression molding was carried out at a pressure of a to obtain a crude shaped material. Next, this crude material was heated and compression-molded into a brake pad shape under the conditions of 5.0 MPa and 160 ° C. to form the friction material 2. This friction material 2 was post-cured at 220 ° C. for 3 hours, surface-polished, and then bonded to the backing metal 1 to complete a disc brake pad.

(Comparative Example 3) Copper fiber (fiber length 5 mm, fiber diameter 10) was used instead of the sintered powder made of copper and graphite.
A disc brake pad according to Comparative Example 3 was manufactured in the same manner as in Example 3 except that 0 μm) was used. (Evaluation) With respect to the disc brake pads according to Example 3 and Comparative Example 3, the mating material aggressiveness was evaluated in the same manner as above.

As shown in the results of FIG. 6, the disc brake pad according to the present Example 3 to which the sintered powder made of copper and graphite was added was the same as Comparative Example 3 in which copper fiber was added instead of the above-mentioned sintered powder. It can be seen that the aggressivity of the mating material is much smaller than that of the disc brake pad. As shown in FIG. 7, after braking, the graphite constituting the sintered powder 6 present on the friction surface 21 of the friction material 2 is softened by heat and becomes a contact surface with the copper counterpart material. It is considered that this is an effect due to the formation of the lubricating coating 7.

Further, the friction coefficient of the disc brake pad according to the present embodiment is 0.37, and the friction coefficient of the disc brake pad according to the comparative example is 0.37, which maintains the friction coefficient required for the brake pad. Was there. In addition,
In the above Example 3, when preparing the sintered powder, the average particle diameter of the copper powder used is 50 to 1 from the viewpoint of facilitating the sintering.
It is preferable that the average particle size of the graphite is 50 μm and the average particle size of the graphite is 1 to 20 μm.

[0036]

As described above in detail, since the friction material for a brake of the present invention can keep the required friction coefficient and suppress the attacking property of the opponent to a small extent, the uneven wear of the opponent material is prevented. It is possible to prevent it and improve the durability of the mating material.

[Brief description of drawings]

FIG. 1 is a perspective view of a disc brake pad according to a first embodiment.

FIG. 2 is a cross-sectional view schematically showing an abrasive contained in a friction material forming the disc brake pad according to the first embodiment.

FIG. 3 is a graph showing the results of evaluating the mating material aggressiveness of the disc brake pads according to Example 1 and Comparative Example 1.

FIG. 4 is a cross-sectional view schematically showing inorganic fibers contained in a friction material forming a disc brake pad according to a second embodiment.

FIG. 5 is a graph showing the results of evaluating the mating material aggressiveness of the disc brake pads according to Example 2 and Comparative Example 2.

FIG. 6 is a graph showing the results of evaluating the mating material aggressiveness of the disc brake pads according to Example 3 and Comparative Example 3.

FIG. 7 is a cross-sectional view schematically illustrating how the mating material aggression of the friction material forming the disc brake pad according to the third embodiment is suppressed.

[Explanation of symbols]

2 is a friction material, 3 is an abrasive, 4 is a resin coating layer, 5 is an inorganic fiber, 51 is a constricted portion, and 6 is a sintered powder.

Claims (3)

[Claims] 1. A friction material for a brake, which comprises a fiber base material, a resin binder, and various additives, wherein at least a part of the hard particles made of an inorganic material among the additives has a higher heat resistance than the resin binder. A friction material for a brake, the surface of which is coated with a low resin coating layer. 2. A friction material for a brake, which comprises a fiber base material, a resin binder, and various additives, wherein at least a part of the fiber base material has a strength-reduced portion in which the strength is partially reduced. A friction material for brakes that is characterized by 3. A friction material for a brake, which comprises a fiber base material, a resin binder, and various additives, wherein the friction material for a brake comprises sintered powder made of copper and graphite.