JPH02212582A - Friction material - Google Patents

Abstract

PURPOSE:To obtain a friction material which is easy to mold, can suitably control the fading of a brake, etc., and has high durability by using as constituents a specified amount of carbon fibers and a specified amount of aramid fibers comprising a mixture of pulpy fibers and cut fibers. CONSTITUTION:A friction material containing as fibrous material 3-30wt.% carbon fibers (A) and 2-20wt.% aramid fibers (B) comprising a mixture of pulpy fibers (a) and cut fibers (b), wherein the weight ratio of (a) to (b) in B is 0.5 or greater. The fibrillar fibers (a) serve to improve the durability of a friction material after molding, and incorporate the fibers (b) and fibers (A) or other fillers, so that these fibers and fillers are suitably dispersed and an unnecessary increase in bulk density is prevented when the friction material is molded, thus giving a friction material which is easy to mold, can suitably control the fading of a brake, and has high durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] <Industrial Application Field> The present invention relates to a friction material used for automobile brake linings, disc brake pads, clutch facings, etc.

<Conventional technology> In recent years, asbestos has been used as a fiber material included in friction materials used in automobile disc brake pads, clutch facings, etc., as it suppresses the fading phenomenon and has superior wear resistance than the conventionally used asbestos. It has been proposed to use carbon fiber, aramid fiber, etc.
An example of this is disclosed in Japanese Patent No. 06980.

In such friction materials, especially aramid fibers, it is preferable to mix relatively high-strength cut fibers with pulp fibers that incorporate filler, resin, and other fibers into the fibril fibers. If there are too many cut fibers, the bulk increases as the fibers are defibrated, making molding difficult. If there are too many pulp fibers, it becomes difficult to obtain the desired strength.

<Problems to be Solved by the Invention> In view of the problems of the prior art, the main objects of the present invention are to facilitate molding, to suitably suppress fade phenomena in brakes, etc., and to increase strength after molding. and to provide a friction material with improved durability.

[Structure of the Invention] <Means for Solving the Problems> According to the present invention, such an object is achieved by using three carbon fibers.
% by weight to 30% by weight, and 2% to 20% by weight of aramid fibers consisting of a mixture of pulp fibers and cut fibers, and the weight ratio of the pulp fibers to the cut fibers is 0. This is achieved by providing a friction material characterized by a friction coefficient of 5 or more.

In this way, the durability after molding is improved by the pulp fibers of the aramid fibers, and the fibril fibers incorporate cut aramid fibers, carbon fibers, or other fillers, so that each of them can be suitably processed. In addition to being dispersed, there is no unnecessary increase in stiffness during molding.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 schematically show an automobile brake pad 1, a die 2 for molding a preform of the pad, and a punch 3 made of chrome-molybdenum steel.

The inside of the die 2 has a bottom surface area of 45 cd and is approximately fan-shaped, that is, the shape of a brake pad, and the punch 3 has a shape corresponding to this. Inside this die 2, 2.44% by weight of bulb-shaped aramid fibers (hereinafter referred to as wL%) and 1 cut aramid fiber with a diameter of 7 μm and a total length of 6+ am were placed as fiber materials. 24 wL% and a diameter of 6 μm and a total length of 3
mm carbon fiber 3°48wL%, copper powder 17.mm as a metal powder to increase the coefficient of friction. 16vL% and copper-zinc alloy powder 24.50wt%, graphite 3.68vL% and molybdenum disulfide 7°69wt% as a solid lubricant to prevent partial adhesion between the metal powder and the rotor. Silicon dioxide 4.32wL% as a high-hardness inorganic filler with a cleaning effect, and barium sulfate 18 as a relatively low-hardness inorganic filler to prevent and suppress pad wear and decrease in friction coefficient at high temperatures.
．． 04wt%, melamine dust 7.53wt% as an organic filler to stabilize the friction coefficient at low surface pressure, phenol resin as a binder: /9.21wt%, pH
n adjustment agent 0. Weigh 120 g of a mixed material made by mixing 72 wt% using a standard method and fill it into a die 2 with a cross-sectional area of 45 cm.
The material is compressed at a rate of 10 kg/cJ, and then finished to form the brake pad 1 shown in FIG. 2.

Here, the aramid fiber of this example is an aramid fiber made of Kevlar 49 (trademark of DuPont). Further, the carbon fiber of this example is a PAN-based carbon fiber made of Torayca T300 (trademark of Toshisha Co., Ltd.), which has high heat resistance and strength.

Figures 3 to 5 show a brake test conducted on the brake pad 1 and a conventional brake pad using a fiber material made of asbestos based on the passenger car brake system dynamometer test method specified in JASOC406-82. This is a graph comparing the results.

Here, the components contained in the conventional brake pad made of friction material are asbestos fiber 20.0 wt%, calcium carbonate 1
．． 0w1%, barium sulfate 32. 5vt%, cashew dust and phenol resin total 23, OwL
%, copper powder 20. 0w1%, zinc powder 0゜5wt%,
The iron powder was 3.0w1%.

First, based on the JASO regulations, initial measurements, pre-matching checks, first efficacy tests, and matching are performed, followed by a second effectiveness test. That is, the brake temperature before braking is 80°C,
Braking initial speed 50km+/h, 1100k/h and 130km/h
km/h, the braking deceleration is varied in the range of 0.1 to 0°8G, and the friction coefficient (μ) is determined from the braking torque at each braking deceleration (Fig. 3).

Subsequently, a first fade recovery test is performed. That is, the brake temperature before braking is 80°C, and the initial braking speed is 50 km/h.
, the braking deceleration is constant at 0.3G (or the pressure at which 0.3G is obtained is constant), and the number of brakings is set to 3 to check the baseline of the friction coefficient (μ).

Next, perform a fade test. That is, the brake temperature before the first braking was 60°C, the initial braking speed was 1100 k/h,
Assuming that the braking deceleration is constant at 0.45G (or the pressure is constant to obtain 0.45G), the braking interval is 35 seconds, and the number of braking is 10 times, calculate the brake temperature and the friction coefficient (μ) for each time (4th
figure). Also, continue with the recovery test. That is, the initial braking speed is 50 km/h, the braking deceleration is constant at 0.3 G (or the pressure obtained from the baseline check is constant), and the braking interval is 1.
Calculate the brake temperature and friction coefficient (μ) in the same way as the above fade test by braking 15 times for 20 seconds (Figure 4)
.

Furthermore, as a third effectiveness test, the coefficient of friction (μ) is determined under the same conditions as the second effectiveness test (Figure 5).

As clearly shown in FIG. 4, the brake pad 1 (solid line A) using the friction material according to the present invention is more sensitive to temperature changes in the brake than the brake pad (broken line B) using the conventional friction material. It can be seen that the change in the friction coefficient (μ) is small. Further, as clearly shown in FIGS. 3 and 5, the brake pad 1 (solid line A) using the friction material based on the present invention is
It can be seen that the change in the coefficient of friction (μ) due to thermal history is also smaller compared to a brake pad using a conventional friction material (broken line B).

In this example, carbon fibers with high thermal conductivity are used, but by combining them with aramid fibers with relatively low thermal conductivity, it is possible to not only prevent vapor lock of the brakes, but also to prevent the vapor lock of the brakes. Since it is made of loose aramid fiber, which has higher heat resistance (durability against abrasion cracks, etc.) than aramid fiber, by combining it with carbon fiber, a friction material with excellent heat resistance, durability, and fade resistance can be obtained. It will be done. In addition, PAN-based carbon fiber contributes to stabilizing the coefficient of friction (μ) at high temperatures.
The diameter of this PAN-based carbon fiber is preferably 15 μm or less in order to obtain a sufficient reinforcing effect, and furthermore, in order to obtain a reinforcing effect and a dispersion effect of the carbon fiber itself, its total length is 0.5 a+m to 9°0+a-. It is good to set it as a range.

In this example, a total of 3.68 wt% of pulp-like and cut aramid fibers was mixed into the friction material, but in reality, 2 to 20 wt% of pulp-like and cut aramid fibers were mixed.
It is sufficient to mix within the range of vt%. Here, if the aramid fiber content is less than 2 wt%, it becomes difficult to mold the preform, and if it exceeds 20 wt%, the friction coefficient decreases at high temperatures.

In addition, in this example, the pulp-like aramid fiber was
Although mixed in wt%, pulp-like aramid fiber not only improves durability, but also incorporates cut aramid fibers that tend to increase bulk density, and has the effect of suitably suppressing volume increase. It is sufficient if it is 1/2 or more of the cut aramid fiber. Here, if the pulp-like aramid fiber is less than 1/2 of the cut aramid fiber, it will not be possible to suppress the volume increase due to defibration of the cut aramid fiber, which will increase the pressurizing force during preform molding or increase the size of the mold. The need arises. Note that the pulp-like aramid fibers also have the effect of taking in fillers, resins, carbon fibers, etc. that are relatively easy to segregate, and dispersing them appropriately.

In addition, in this example, the cut aramid fiber was 1°24vt.
The cut aramid fibers have the effect of reducing rotor aggressiveness and further improving durability. Here, since the loose pulp aramid fibers used in this example have high durability, sufficient durability can be obtained even without mixing cut aramid fibers, for example.

In addition, in this example, 3.48wt% of PAN-based carbon fiber was mixed in the friction material, but in reality it was 3 to 30wt%.
Preferably, the weight of carbon fiber is at least 0.6 times the total amount of bulb-shaped aramid fibers and cut aramid fibers, and in this case, the fade rate of the friction material is significantly improved. do. Here, if the carbon fiber content is less than 3 wt%, it is difficult to stabilize the friction coefficient at high temperatures, and if it exceeds 3 Qvt%, the friction coefficient at normal temperatures decreases.

In addition, in this example, copper powder and copper-zinc alloy powder were mixed as metal powder in the friction material, but copper, nickel, copper-zinc alloy powder, etc.
At least one of zinc alloy, iron, and copper-tin alloy may be mixed in a range of 10 to 50 wt%. here,
If the metal powder is less than 10wt%, it will have little effect on increasing the coefficient of friction, and if it exceeds 50wt%, it will partially adhere to the rotor, causing shudder.

Furthermore, in this example, graphite and molybdenum disulfide were mixed as solid lubricants in the friction material, but in reality at least 11 types of graphite, molybdenum disulfide, zinc sulfide, lead sulfide, and antimony trisulfide were mixed into the friction material. ~2
It is sufficient to mix 0wt%.

Here, if the solid lubricant content is less than 5 wt%, there is little effect of preventing adhesion between the bipedal metal powder and the rotor, and if it exceeds 20 wt%, the coefficient of friction decreases.

In addition, in this example, silicon dioxide was mixed into the friction material as a high hardness inorganic filler, and barium sulfate was mixed as a low hardness inorganic filler, but in reality, silicon dioxide was mixed as a high hardness inorganic filler. , alumina, mullite, zirconium oxide, and spinel type ferrite (Fe304), and at least one of barium sulfate, calcium carbonate, and cupric oxide as a low hardness inorganic filler. It is sufficient to mix within a range of 50 wt%. Here, if it is less than 1QwL%, there is almost no effect of cleaning the rotor and suppressing the wear of the pad at high temperatures and the decrease in the friction coefficient, and if it exceeds 50wt%, the aggressiveness of the rotor becomes high (and uneven wear occurs). It causes.

Further, in this example, melamine dust was mixed as an organic filler in the friction material, but in reality, at least one of melamine dust, cashew dust, and phenol dust should be mixed in a range of 3 to 20 vt%. good. Here, if it is less than 3 vL%, there is almost no effect of stabilizing the coefficient of friction at low surface pressures, and if it exceeds 20 wt%, it causes a decrease in the coefficient of friction at high temperatures.

Furthermore, the phenol resin mixed into the friction material as a binder in this embodiment may actually be mixed in a range of 8 to 15 wt%. Here, if the phenol resin is less than 8 wL%, it has almost no effect as a binder, and 1
If it exceeds 5 wt%, the friction coefficient at high temperatures will decrease.

[Effects of the Invention] As described above, according to the present invention, the carbon fibers contained in the friction material are in the range of 3wt% to 30wt%, and the aramid fibers consisting of cut fibers and pulp fibers are in the range of 2wt% to 20wt%.
% range and the weight ratio of pulp fibers to cut fibers is 0.5 or more to obtain a friction material that is easy to mold, can suitably suppress the fade phenomenon in brakes, and has high durability. Because it can be done, the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a die and punch for molding a preform for an automobile brake pad using a friction material according to the present invention. FIG. 2 is a front view showing a brake pad made of a friction material according to the present invention. FIGS. 3 to 5 are graphs showing the results of brake tests conducted using a brake pad made of a friction material according to the present invention. 1...Brake Parameter 2...Dice 3...Punch Patent Applicant Honda Motor Co., Ltd. Nissin Kogyo Co., Ltd. Agent

Claims (4)

[Claims] (1) 3% to 30% by weight of carbon fibers, 2% of aramid fibers consisting of a mixture of pulp fibers and cut fibers.
% to 20% by weight, and the weight ratio of the pulp fiber to the cut fiber is 0.
A friction material characterized by having a friction coefficient of 5 or more. (2) The friction material according to claim 1, wherein the weight ratio of the carbon fiber to the aramid fiber is 0.6 or more. (3) The friction material according to claim 1 or 2, wherein the aramid fibers are made of para-aramid fibers. (4) 10% to 50% by weight of at least one of copper, nickel, copper-zinc alloy, iron and copper-tin alloy; graphite, molybdenum disulfide, zinc sulfide, lead sulfide and antimony trisulfide; At least one type of 5
% to 20% by weight, at least one of silicon dioxide, alumina, mullite, zirconium oxide, and spinel ferrite (Fe_3O_4) and at least one of barium sulfate, calcium carbonate, and cupric oxide. It is characterized by containing a total of 10% to 50% by weight, 3% to 20% by weight of at least one of melamine dust, cashew dust, and phenol dust, and 8% to 15% by weight of phenol resin. A friction material according to any one of claims 1 to 3.