JP2016011404A - Brake friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake friction material capable of ensuring friction factor and wear resistance even when a copper content is less than 5 mass%.SOLUTION: A brake friction material 3 contains at least reinforced fiber, a binder, a lubricating material, a friction adjustment material, and a filler. When a total amount of the brake friction material 3 is 100 mass%, a copper content in the brake friction material is not less than 3 mass% and less than 5 mass%, and a zirconium oxide content in the brake friction material is 5-15 mass%. The reinforced fiber is composed of copper fiber, and the copper fiber has a diameter of 150-230 μm.

Description

  The present invention relates to a brake friction material.

  In order to improve the wear resistance of the brake friction material, copper fibers are used as metal fibers, and conventionally used copper fibers having a fiber diameter of 50 μm to 100 μm are used. In order to satisfy conditions such as wear resistance and withstand use as a brake friction material, it is necessary to contain 5% by mass or more of copper fibers when the entire brake friction material is 100% by mass. However, since the friction material containing copper contains copper in the abrasion powder generated at the time of braking, there is an increasing demand for reducing its use.

JP 2010-77341 A

  According to the technique described in the above patent document, since copper fibers having a fiber diameter of 50 μm to 100 μm are used, if the content is reduced to less than 5% by mass, the wear amount of the brake friction material is increased and the wear resistance is increased. descend.

  In addition, there is a problem that the friction coefficient in the automobile engineering society standard JASO C 406 “passenger car—brake device—dynamometer test method” is lowered.

  Therefore, an object of the present invention is to provide a brake friction material that can ensure a friction coefficient and wear resistance even when the copper content is less than 5% by mass.

  As a result of intensive studies to solve the above problems, the present inventors have focused on the fiber diameter of the copper fiber, changed the fiber diameter of the copper fiber from 150 μm to 230 μm, and the content is 3 mass% or more 5 It has been found that the above problem can be solved by using less than mass% and further using 5 to 15 mass% of zirconium oxide.

  That is, the brake friction material of the present invention is a friction material containing at least a reinforcing fiber, a binder, a lubricant, a friction adjusting material, and a filler, and the total amount of the brake friction material is 100% by mass. The content of copper in the brake friction material is 3% by mass or more and less than 5% by mass, the content of zirconium oxide in the brake friction material is 5% by mass or more and 15% by mass or less, and the reinforcing fiber is It consists of copper fiber, The diameter of the said copper fiber is 150 micrometers or more and 230 micrometers or less.

  Further, the particle diameter of the zirconium oxide is preferably 1 μm or more and 5 μm or less.

  The brake friction material of the present invention can achieve both of ensuring a stable friction coefficient and ensuring wear resistance even when the copper content is less than 5% by mass.

  Further, if the particle diameter of zirconium oxide is 1 μm or more and 5 μm or less, it is possible to achieve both excellent fade resistance and a reduction in the amount of wear of the rotor, and further suppress an increase in cost.

It is a front view showing a brake pad as one example of application of a brake friction material of one embodiment concerning the present invention.

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 this embodiment is a brake friction material used for a brake pad for a disc brake and a brake shoe for a drum brake used for braking an automobile. These brake pads and brake shoes are adapted to brake a vehicle by abutting against a member to be braked such as a disk rotor or a brake drum to generate a frictional force. FIG. 1 shows a brake pad 1 for a disc brake as an example. The brake pad 1 includes a back plate 2 and a brake friction material 3 bonded to the surface of the back plate 2. The brake pad 1 is supported by the non-rotating portion of the vehicle on the back plate 2, and the brake friction material 3 is pressed by the disc brake caliper on the opposite side of the back plate 2 from the brake friction material 3. It contacts the disc that rotates with the wheel and brakes the rotation of the disc.

  The brake friction material of this embodiment is a brake friction material containing at least a reinforcing fiber, a binder, a lubricant, a friction adjusting material, and a filler, and the total amount of the brake friction material is 100% by mass. When the fiber diameter of the copper fiber as the reinforcing fiber is 150 μm to 230 μm, the copper content including the copper fiber is 3% by mass or more and less than 5% by mass, and the content of zirconium oxide as the friction modifier is It is 5 mass%-15 mass%.

  When the total amount of the brake friction material is 100% by mass, as described above, the copper content is 3% by mass or more and less than 5% by mass, of which the copper fiber is 3% by mass or more and less than 5% by mass. Contains.

  Here, the fiber diameter of the copper fiber is set to 150 μm to 230 μm when the copper fiber content is less than 5% by mass and the copper fiber having a fiber diameter smaller than 150 μm is used from the friction surface with the rotor. This is because dropping of copper fibers becomes severe, the coefficient of friction is low, and the amount of pad wear increases.

  Further, when copper fibers having a fiber diameter exceeding 230 μm are used, when the copper fiber content is less than 3% by mass, the dispersibility in the brake friction material is deteriorated, that is, in the contact surface to the braked member. The distribution of the copper fiber is biased, and the friction coefficient and the pad wear amount vary greatly, and there is a practical problem as a brake friction material.

  The reason why the copper fiber content is 3% by mass or more is that when the copper fiber content is less than 3% by mass, the dispersibility of the copper fiber in the brake friction material is deteriorated, and the friction coefficient and the pad wear amount are reduced. The variation becomes large and there is a practical problem.

  The reinforcing fibers contained in the brake friction material may include organic fibers such as aramid fibers, inorganic fibers such as rock wool, potassium titanate fibers, and the like as fibers other than copper fibers.

  As a friction modifier, 5 to 15 mass% of zirconium oxide is contained.

  The reason why the content of zirconium oxide is 5% by mass to 15% by mass is that when the content is less than 5% by mass, the effect of zirconium oxide is small, the friction coefficient during fading is greatly reduced, and the amount of pad wear increases. is there. On the other hand, if the amount exceeds 15% by mass, the amount of wear of the pad is small, but there is a problem that the abrasion powder is transferred to the rotor and abnormal noise is generated during braking. Further, since zirconium oxide is expensive, if it exceeds 15 mass%, the cost increases.

  Here, it is preferable to set the particle diameter of zirconium oxide from 1 μm to 5 μm because the wear of the rotor can be suppressed while increasing the friction coefficient. That is, when the particle diameter of zirconium oxide is less than 1 μm, the friction coefficient is slightly low because the particle diameter is small, and when it exceeds 5 μm, the wear of the rotor increases, and this causes problems such as contamination of the wheel.

  In addition, the particle diameter of zirconium oxide in the present embodiment indicates an average particle diameter, and does not indicate an absolute particle diameter.

  The friction modifier preferably includes one or both of an organic friction modifier and an inorganic friction modifier as a material other than zirconium oxide. As the inorganic friction modifier, dust, rubber powder, etc., powders such as alumina powder, iron oxide, zinc, and tin are preferably used.

  Further, as the lubricant, graphite, coke, antimony trisulfide, molybdenum disulfide, mica and the like are preferably used.

  As the filler, barium sulfate or the like is preferably used. As barium sulfate, natural barite pulverized powder is preferable.

  As the binder, an unmodified phenol resin or the like is preferably used.

  By setting it as such a structure, the total mass of each of a copper fiber and a zirconium oxide is optimized. As a result, the variation in the frictional characteristics is small and the stability is excellent, and the noise is excellently prevented.

  In addition, you may contain a pH adjuster etc. as needed. As the pH adjusting material, calcium hydroxide or the like is used.

According to the above embodiment, even when the copper content is less than 5% by mass, wear resistance can be ensured by using copper fibers having a fiber diameter of 150 μm or more and 230 μm or less, and the inclusion of zirconium oxide. By making the rate 5% by mass or more and 15% by mass or less, the friction coefficient can be stabilized. That is, according to the present embodiment, it is possible to achieve both a stable friction coefficient and a wear resistance.
In addition, since the diameter of the copper fiber is increased from 50 μm to 100 μm from the conventional one, the fiber diameter is increased from 150 μm to 230 μm, and the cross-sectional area is increased. Since it can be reduced to the extent, the power required for processing can be reduced and the burden on the environment can be reduced.
Here, if the particle diameter of zirconium oxide is 1 μm to 5 μm, both excellent fade resistance and reduction of the amount of rotor wear can be achieved, brake noise can be suppressed, and cost increase can be suppressed.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

  The brake friction material of Examples 1-12 was produced as follows.

  First, the back metal (back plate) was thoroughly washed with a solvent, and after this chemical conversion treatment such as shot blasting or phosphoric acid treatment was applied to the back metal, an adhesive was applied to the surface in contact with the friction material and dried.

  Further, copper fibers having an average fiber diameter of 150 to 230 μm and an average fiber length of 2 to 4 mm, zirconium oxide powder having an average particle diameter of 0.5 to 8.0 μm, a phenol resin and an unvulcanized nitrile rubber as a binder Powder, other reinforcing fibers such as potassium titanate plate fiber, rock wool and aramid fiber, antimony trisulfide as lubricant, artificial graphite, coke, mica, cashew dust powder as organic friction modifier, barium sulfate as filler A predetermined amount of calcium hydroxide as a pH adjusting material was weighed and mixed.

  Table 1 shows the amount (% by mass) of each of Examples 1 to 12.

Here, the fiber diameter of the copper fiber is 150 μm, which is the lower limit, and the content is 3.0% by mass, which is the lower limit. The particle diameter of the zirconium oxide powder is 1.0 μm, which is the intermediate value, and the content is intermediate. Example 1 shows a brake friction material of 10.0% by mass,
The fiber diameter of the copper fiber is 150 μm, which is the lower limit, and its content is 4.9 mass%, which is the upper limit. The particle diameter of the zirconium oxide powder is 1.0 μm, and its content is 10.0 mass%, which is the intermediate value. Example 2 for a brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit value, and its content is 3.0% by mass, which is the lower limit value. The particle diameter of the zirconium oxide powder is 1.0 μm, and its content is 10.0% by mass, which is an intermediate value. Example 3 for a brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.9% by mass, and the particle diameter of the zirconium oxide powder is 1.0 μm, and its content is 10.0% by mass, which is an intermediate value. Example 4 for a brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.0% by mass, the particle diameter of the zirconium oxide powder is 1.0 μm, and the content is 5.0% by mass, which is the lower limit. Example 5 for a brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.0% by mass, the particle diameter of the zirconium oxide powder is 1.0 μm, and the content is 15.0% by mass, which is the upper limit. Example 6 is a brake friction material.
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.0% by mass, the particle diameter of the zirconium oxide powder is 5.0 μm, and the content is 5.0% by mass, which is the lower limit. Example 7 for brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.0% by mass, the particle diameter of the zirconium oxide powder is 5.0 μm, and its content is 15.0% by mass, which is the upper limit. Example 8 for brake friction material
The fiber diameter of the copper fiber is 150 μm, which is the lower limit, and its content is 3.0% by mass, which is the lower limit. The particle diameter of the zirconium oxide powder is 1.0 μm, and the content is 5.0% by mass, which is the lower limit. Example 9 for a brake friction material
The fiber diameter of the copper fiber is 230 μm, which is the upper limit, and its content is 4.9% by mass, and the particle diameter of the zirconium oxide powder is 5.0 μm, and the content is 15.0% by mass, which is the upper limit. Example 10 is a brake friction material.
The fiber diameter of the copper fiber is 150 μm, which is the lower limit value, and its content is 4.0% by mass, the particle diameter of the zirconium oxide powder is 0.5 μm, and its content is 10.0% by mass, which is the intermediate value. Example 11 is a brake friction material.
The fiber diameter of the copper fiber is 150 μm, which is the lower limit, and the content thereof is 4.0% by mass, the particle diameter of the zirconium oxide powder is 8.0 μm, and the content is 10.0% by mass, which is the intermediate value. Example 12 for a brake friction material
It was.

  Thereafter, the mixture of each Example was cold compression molded at a pressure of 50 MPa and normal temperature (25 ° C.) using a predetermined mold to obtain a preformed product.

  Next, this cold compression molded product and the back metal 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 240 seconds at a pressure of 40 MPa.

  Furthermore, this molded product was heat-treated at 220 ° C. for 6 hours, and thereafter subjected to polishing and grooving to obtain brake pads of Examples 1 to 12.

  Brake pads (brake friction materials) of Comparative Examples 1-7 were produced in exactly the same manner as in Examples 1-12 above.

  Table 2 shows the amount (% by mass) of each of Comparative Examples 1 to 7.

Here, a brake friction material of 100 μm in which the fiber diameter of the copper fiber is smaller than the lower limit of 150 μm is referred to as Comparative Example 1.
A brake friction material of 250 μm in which the fiber diameter of the copper fiber is larger than the upper limit of 230 μm is used as Comparative Example 2,
Comparative Example 3, a brake friction material having a copper fiber content of 2.0% by mass less than the lower limit of 3.0% by mass,
Comparative Example 4, a brake friction material having a copper fiber content of 5.0% by mass greater than the upper limit of 4.9% by mass,
Comparative Example 5, a brake friction material having a zirconium oxide content of 3.0% by mass less than the lower limit of 5.0% by mass,
Comparative Example 6, a brake friction material having a zirconium oxide content of 20.0% by mass greater than the upper limit of 15.0% by mass,
A brake friction material using chemically synthesized barium sulfate was defined as Comparative Example 7.

  With respect to the brake pads of Examples 1 to 12 and Comparative Examples 1 to 7 thus manufactured, the friction characteristics, the amount of pad wear, the amount of rotor wear, and the frequency of occurrence of squealing by an actual vehicle were measured.

  The friction characteristics, pad wear amount, and rotor wear amount were measured based on the Japan Society of Automotive Engineers standard JASO C 406 “Passenger car-brake device-dynamometer test method”. Further, the amount of rotor wear was measured for two items, the second efficacy test and the first fade recovery test.

The squeal occurrence frequency is predetermined for each combination when the temperature of the brake friction material is in the temperature range from the outside air temperature to a maximum of 250 ° C. and the hydraulic pressure supplied to the disc brake caliper is in the range of 0.2 to 3.0 MPa. The braking test was performed with the actual vehicle, and the number of times when the loudness level generated at this time exceeded a certain value was counted, and the ratio was calculated.
The measurement results of Examples 1 to 12 are shown in Table 3, and the measurement results of Comparative Examples 1 to 7 are shown in Table 4, respectively.

  According to Table 3 and Table 4, it can be said that Examples 1-12 have the same performance as Comparative Example 4 (conventional product) containing 5.0% by mass of copper. It was confirmed that even when the amount was less than 5.0% by mass, it was possible to secure a stable coefficient of friction and ensure wear resistance.

  Even when compared with other comparative examples 1 to 3 and 5 to 7, it was confirmed that Examples 1 to 12 had small fluctuations in friction characteristics and excellent stability.

  Here, from Examples 11 and 12, even if the particle diameter of the zirconium oxide powder is outside the range of 1.0 μm to 5.0 μm, the friction characteristics are the results of the friction characteristics and the frequency of occurrence of squeal by the actual vehicle. It was confirmed to be equivalent to 1-10. However, in Examples 11 and 12, since the pad wear amount and the rotor wear amount are larger than those in Examples 1 to 10, the particle diameter of the zirconium oxide powder may be in the range of 1.0 μm to 5.0 μm. preferable. That is, Examples 1-10 are more excellent in abrasion resistance than Examples 11 and 12. Moreover, Examples 1-10 can obtain the effect of suppressing squeal noise and abnormal noise as compared with Examples 11 and 12.

  In addition, as shown in Comparative Example 6, when the content of zirconium oxide is 20% by weight, squeal noise and abnormal noise are generated. Therefore, the content of zirconium oxide is 5 mass from the viewpoint of brake noise suppression. % To 15% by mass is preferred. Further, when the content of zirconium oxide is 20% by weight, the cost increases. Therefore, from the viewpoint of cost, the content of zirconium oxide is preferably 5% by mass to 15% by mass.

  Further, as shown in Comparative Example 7, when chemically synthesized barium sulfate is used, the pad wear amount and the rotor wear amount are increased. Therefore, it is preferable to use barite as barium sulfate.

1 Brake pad 2 Back plate 3 Brake friction material

Claims (2)

In a brake friction material containing at least a reinforcing fiber, a binder, a lubricant, a friction modifier, and a filler,
When the total amount of the brake friction material is 100% by mass,
The copper content in the brake friction material is 3 mass% or more and less than 5 mass%,
The content of zirconium oxide in the brake friction material is 5% by mass or more and 15% by mass or less,
The reinforcing fiber is made of copper fiber,
The brake friction material, wherein the copper fiber has a diameter of 150 μm or more and 230 μm or less.   The brake friction material according to claim 1, wherein a particle diameter of the zirconium oxide is 1 µm or more and 5 µm or less.

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