JP6031393B2 - Brake friction material - Google Patents

Description

  The present invention relates to a brake friction material, and more particularly, to a brake friction material that is suitably used for a disc brake pad, a brake lining, etc. used for braking an automobile, has excellent friction characteristics, has good adhesion, and is easy to manufacture. It is about.

Conventionally, in brake friction materials for automobiles, natural or man-made fibers such as metal fibers such as steel fibers, mineral fibers, ceramic fibers, aramid fibers, potassium titanate fibers, or sodium titanate polycrystalline fibers are used as the fiber materials. Is used.
In addition to the above-mentioned fiber materials, this brake friction material includes a binder such as phenol resin, a carbon-based material, a lubricant such as molybdenum disulfide, a friction adjusting material such as cashew dust, ceramic powder, and metal powder, and barium sulfate. Several kinds of fillers and pH adjusting materials such as calcium hydroxide are mixed, and then compression molding (preliminary molding) at room temperature, followed by heat compression molding together with a backing metal previously coated with an adhesive, and further heat-treated. After that, it is adjusted to satisfy brake performance such as strength, adhesion, friction characteristics, wear characteristics, and squealing performance by performing groove processing and surface polishing.

As such a brake friction material, there is a brake friction material including graphite having crystal grains (La, Lc) of 80 to 90 nm, which is made of a fiber base material containing at least metal fibers, a filler, and a thermosetting resin. It has been proposed (Patent Document 1).
In this brake friction material, the graphite layer spacing (C / 2) is preferably 0.3357 nm, and the blending amount is preferably 5 to 20% by weight with respect to the total friction material.

JP-A-2-209635

In recent years, brake friction materials have been required to maintain a friction coefficient during braking and to reduce the amount of wear.
By the way, in the conventional brake friction material described above, the graphite contained in the brake friction material adheres to the disk rotor which is the counterpart material at the time of high-temperature braking, so that the problem of reducing the friction coefficient is solved. However, it is difficult to achieve both the maintenance of the friction coefficient during braking and the reduction of the amount of wear, and further improvements have been demanded.

  The present invention has been made in view of the above circumstances, and can further improve the maintenance of the friction coefficient during braking and the reduction of the amount of wear, thereby achieving both improvement of the friction coefficient and reduction of the amount of wear. An object of the present invention is to provide a brake friction material that can be used.

  As a result of intensive studies to solve the above problems, the present inventors, in a brake friction material comprising at least a reinforcing fiber, a binder, a lubricant, a friction modifier, a filler, and a pH adjuster, Paying attention to the average surface spacing indicating the degree of graphitization of the carbon-based material used as a lubricant, a carbon-based material having an average surface spacing of 0.343 to 0.358 nm is used as the carbon-based material. When the amount is 100% by mass, if the carbon-based material having an average surface separation of 0.343 to 0.358 nm is contained as the lubricant, 8 to 15% by mass, the friction coefficient is maintained and the amount of wear during braking is reduced. As a result, the inventors have found that it is possible to improve both the friction coefficient and the wear amount, thereby completing the present invention.

That is, the brake friction material of the present invention contains at least a reinforcing fiber, a binder, a lubricant, a friction modifier, a filler, and a pH adjuster , the phenol friction resin as the binder, When the total amount of the brake friction material is 100% by mass, the lubricant contains 8 to 15% by mass of a carbon-based material having an average surface separation of 0.343 to 0.358 nm.

According to the brake friction material of the present invention, in the brake friction material comprising at least a reinforcing fiber, a binder, a lubricant, a friction modifier, a filler and a pH adjuster, the binder contains a phenol resin, When the total amount of brake friction material is 100% by mass, 8-15% by mass of carbon-based material having an average surface separation of 0.343 to 0.358 nm is contained as a lubricant, so that the friction coefficient during braking is maintained. This can further improve the reduction in the amount of wear. Therefore, both improvement of the friction coefficient and reduction of the wear amount can be achieved.

The form for implementing the brake friction material of this invention is demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

The brake friction material of the present embodiment is a brake friction material containing at least a reinforcing fiber, a binder, a lubricant, a friction adjusting material, a filler, and a pH adjusting agent. The total amount of the brake friction material is 100% by mass. In this case, the lubricant contains 8 to 15% by mass of a carbon-based material having an average surface separation of 0.343 to 0.358 nm.
The brake friction material of this embodiment is characterized in that the carbon-based material is graphite or coke.
Note that the disk rotor or brake drum, which is the counterpart material of the brake friction material of the present embodiment, is made of cast iron, for example, gray cast iron such as FC150, FC190, FC200, FC220, and FC250.

The average spacing between the carbon-based materials described above can be easily measured by investigating the diffraction peak of the (002) plane derived from carbon using X-ray diffraction.
For example, the diffraction peak of the (002) plane derived from carbon is detected around 26 °. The interplanar spacing can be obtained from the angle of the diffraction peak and Bragg's law.

The average plane spacing of the carbon-based material needs to be in the range of 0.343 to 0.358 nm.
Here, the reason why the average spacing of the carbon-based material is in the range of 0.343 to 0.358 nm is that the friction coefficient during braking can be maintained when the carbon-based material is used as a lubricant. In addition, this is because the reduction of the amount of wear can be further improved.
If the average spacing between the carbon-based materials is less than 0.343 nm, the friction coefficient during braking cannot be maintained, and wear resistance is reduced. On the other hand, the average spacing between the planes exceeds 0.358 nm. This is not preferable because the friction coefficient during braking is reduced and the wear resistance is also reduced.

The content of the carbon-based material having the average spacing is preferably 8 to 15% by mass when the total amount of the brake friction material is 100% by mass.
Here, the reason for limiting the content of the carbon-based material having the above-described average spacing to 8 to 15% by mass is that when the content of the carbon-based material is less than 8% by mass, the amount of the carbon-based material is relative. However, if the content of the carbon-based material exceeds 15% by mass, the amount of the carbon-based material is too large, and the friction coefficient during braking is maintained. This is not preferable because it becomes difficult and wear resistance also decreases.

The carbon-based material is preferably graphite or coke in view of the fact that it is easy to maintain a friction coefficient, is easy to handle, and is inexpensive.
This carbon-based material may contain other lubricants such as antimony trisulfide and molybdenum disulfide as long as the characteristics as a lubricant are not impaired.

  Reinforcing fibers include copper fibers, steel fibers, iron-aluminum alloy fibers, etc., organic fibers such as aramid fibers, acrylic fibers, rock wool, wollastonite, potassium titanate fibers, sodium titanate fibers, carbon fibers. Natural or artificial fibers such as inorganic fibers (inorganic fibers) such as calcium carbonate fibers, magnesium carbonate fibers and ceramic fibers are preferably used.

  Examples of the binder include straight phenol resins (unmodified phenol resins), phenol resins such as modified phenol resins, polyimide resins, melamine resins, etc. In particular, straight phenol resins and modified phenols in terms of heat resistance. A phenol resin such as a resin is preferably used.

As the friction modifier, an organic friction modifier and / or an inorganic friction modifier is preferably used. Organic friction modifiers are cashew dust, rubber powder such as unvulcanized nitrile rubber powder, and inorganic friction modifiers are zinc, zirconium silicate, alumina, iron oxide, tin, zircon, mica powder, etc. Are preferably used.
As the filler, barium sulfate or the like is preferably used.
As the pH adjusting material, calcium hydroxide or the like is preferably used.

  The brake friction material includes a carbon-based material having an average surface separation of 0.343 to 0.358 nm, a reinforcing fiber, a binder, a lubricant other than the carbon-based material, a friction adjusting material, a filler, and a pH adjusting material. Each amount of the agent is adjusted and mixed so as to satisfy the brake performance such as strength, adhesiveness, friction characteristics, wear characteristics, squealing performance, and then compression molding (preliminary molding) at room temperature, It can be produced by heat compression molding together with a backing metal coated with an adhesive, heat treatment, and then groove processing or surface polishing.

As described above, according to this brake friction material, when the total amount of the brake friction material is 100% by mass, a carbon-based material having an average surface separation of 0.343 to 0.358 nm is 8 to 15 as a lubricant. Since it is contained by mass%, the friction coefficient during braking can be maintained, and the reduction in wear can be further improved. Therefore, both improvement of the friction coefficient and reduction of the wear amount can be achieved.
Moreover, since the carbon-based material having an average interplanar spacing of 0.343 to 0.358 nm does not have a high degree of graphitization and can control lubricity, the difference between the dynamic friction coefficient and the static friction coefficient can be reduced. Generation of goo noise can be suppressed.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.
"Examples 1 to 10"
The brake pads (brake friction materials) of Examples 1 to 10 were produced.
First, the back plate (back metal) is thoroughly cleaned using a cleaning agent, and after chemical conversion treatment such as shot blasting or phosphoric acid treatment is applied to the back plate, an adhesive is applied to the surface in contact with the friction material and dried. .

Moreover, four types of fast-curing phenol resin and modified phenol resin, inorganic fibers such as potassium titanate fiber and rock wool, copper fiber, steel fiber, aramid fiber, and average surface spacing of 0.343 to 0.358 nm. Carbon-based materials, cashew dust, organic friction modifiers such as vulcanized rubber powder, inorganic friction modifiers such as iron oxide, zinc powder and zirconium silicate, calcium hydroxide as pH adjuster, barium sulfate as filler Were weighed and mixed in a predetermined amount.
Table 1 shows the blending amounts (mass%) of Examples 1 to 10.

  Here, Example 1 is a brake pad including a carbon-based material having an average interplanar spacing of 0.343 nm, which is the lower limit of the present invention, and 8 mass% of the lower limit of the present invention. Example 2 is a brake pad containing 12% by mass of the material of the present invention, which is an intermediate value of the present invention, Example 3 is a brake pad containing 12% by mass of a carbon-based material having an average interplanar spacing of 0.349 nm, and an average interplanar spacing of 0.352 nm. Example 4 is a brake pad containing 12% by mass of the above carbon-based material, Example 5 is a brake pad containing 12% by mass of a carbon-based material having an average surface spacing of 0.355 nm, and the average surface spacing is the upper limit of the present invention. Example 6 is a brake pad containing 15% by mass of the carbon-based material of 0.358 nm which is the upper limit of the present invention, and Example 6 is a lower limit of the carbon-based material of 0.349 nm whose average interplanar spacing is the intermediate value of the present invention. In Example 8 is a brake pad containing 8% by mass, and Example 8 is an example of a brake pad containing 15% by mass of the carbon-based material of 0.349 nm having the same average plane spacing as that of Example 7 of the present invention. Example 9 is a brake pad containing a carbon-based material having a surface spacing of 0.343 nm, which is the lower limit of the present invention, and 15% by mass of the upper limit of the present invention, and an average surface spacing of 0.358 nm, the upper limit of the present invention. Example 10 is a brake pad containing 8% by mass of the above carbon-based material, which is the lower limit of the present invention.

Thereafter, this mixture was cold compression molded using a predetermined mold at a pressure of 80 MPa and at a normal temperature (25 ° C.).
Next, the cold compression molded product and the back plate coated with the above-mentioned adhesive were set in a mold heated to 150 ° C., and subjected to heat compression molding at this temperature for 300 seconds at a pressure of 40 MPa.
Next, this molded product was heat-treated at 200 ° C. for about 5 hours, and further subjected to polishing and grooving to obtain the brake pads of Examples 1 to 10.

"Comparative Examples 1-7"
The brake pads (brake friction materials) of Comparative Examples 1 to 7 were produced according to Examples 1 to 10.
Table 2 shows the amount (% by mass) of each of Comparative Examples 1 to 7.

  Here, a comparative example 1 is used for a brake pad containing a carbon-based material having an average interplanar distance of 0.336 nm, which is smaller than the lower limit of the present invention, and 12% by mass, which is the intermediate value of the present invention. A brake pad containing 12% by mass of a slightly smaller 0.342 nm carbon-based material is Comparative Example 2, and a brake pad containing 12% by mass of a 0.359 nm carbon-based material whose average interplanar spacing is slightly larger than the upper limit of the present invention. Comparative Example 3, a brake pad containing 12% by mass of a 0.366 nm carbon-based material having an average interplanar spacing greater than the upper limit of the present invention is Comparative Example 4, and 0.370 nm carbon having an average interplanar spacing of greater than the upper limit of the present invention. Comparative Example 5 is a brake pad containing 12% by mass of a system material, Comparative Example 6 is a brake pad containing 7% by mass of a carbon-based material having an average interplanar spacing of 0.349 nm less than the lower limit of the present invention. Surface interval has Comparative Example 7 the brakes pads containing 16 weight percent greater than the upper limit of the present invention the carbonaceous material 0.345 nm. In addition, said comparative example 1 was produced supposing the thing of the patent document 1 used as a prior art.

The friction characteristics of the thus-produced brake pads of Examples 1 to 10 and Comparative Examples 1 to 7 were evaluated.
Here, the first fade recovery test performed by pressing the brake friction material against the disc rotor was measured based on the Japan Society of Automotive Engineers standard JASO C 406 “passenger car-brake device-dynamometer test method”.

The automobile manufacturer defines the minimum friction coefficient (μ) during the first fade to a predetermined value within the range of 0.22 to 0.25, although this differs depending on the vehicle type. In order to make the value larger than the above range in consideration of the difference and the like, the allowable value of the minimum friction coefficient (μ) at the first fade was set to 0.235, which was used as a judgment criterion.
The minimum friction coefficient (μ) and wear amount (mm) at the first fade of each of Examples 1 to 10 are shown in Table 3, and the minimum friction coefficient (μ) and wear amount at the first fade of each of Comparative Examples 1 to 7 are shown in Table 3. Table 4 shows (mm).

According to Table 3 and Table 4, the minimum friction coefficient at the time of the 1st fade of each of Examples 1 to 10 was 0.235 or more, and it was confirmed that the allowable value was satisfied. Further, the wear amount was in the range of 0.526 mm to 0.614, which was smaller than the wear amount of Comparative Example 1 assumed as the prior art, and it was confirmed that the wear resistance was improved.
On the other hand, the minimum friction coefficient at the first fade of each of Comparative Examples 1 to 7 is smaller than 0.235 except for Comparative Example 6, and does not satisfy the allowable value of the minimum friction coefficient at the first fade. confirmed. Moreover, about the comparative example 6, the wear amount was larger than the wear amount of the comparative example 1 assumed as a prior art, and it was confirmed that abrasion resistance has fallen.

  As described above, according to the brake pads of Examples 1 to 10, when the total amount of the brake friction material is 100% by mass, a carbon-based material having an average surface separation of 0.343 to 0.358 nm is used as the lubricant. By containing 15% by mass, the friction coefficient during braking can be maintained, and it can be confirmed that the wear amount can be further reduced, and both the improvement of the friction coefficient and the reduction of the wear amount are achieved. I was able to confirm that I was able to.

  The present invention is a brake friction material containing at least a reinforcing fiber, a binder, a lubricant, a friction modifier, a filler and a pH adjuster, and when the total amount of the brake friction material is 100% by mass, By containing 8-15% by mass of a carbon-based material having an average surface separation of 0.343-0.358 nm as a lubricant, the friction coefficient during braking can be maintained, and the reduction of wear can be further improved. Therefore, it is possible to achieve both improvement in the coefficient of friction and reduction in the amount of wear, and because it is easy to manufacture, it can be applied not only to automobiles, but also to power machines having a brake mechanism, Its industrial significance is extremely large.

Claims (2)

In a brake friction material comprising at least a reinforcing fiber, a binder, a lubricant, a friction modifier, a filler and a pH adjuster,
Containing a phenolic resin as the binder,
When the total amount of the brake friction material is 100% by mass,
A brake friction material comprising 8 to 15 mass% of a carbon-based material having an average surface separation of 0.343 to 0.358 nm as the lubricant.   The brake friction material according to claim 1, wherein the carbon-based material is graphite or coke.