JPH05117633A - Friction material - Google Patents

Abstract

PURPOSE:To prevent the occurrence of low-frequency brake noise in an asbestosfree friction material. CONSTITUTION:3-20vol.% carbon black having a DBP adsorption of 80ml/100g or higher and an iodine adsorption of 80mg/g is incorporated into an asbestos- free friction material comprising a fibrous substrate material, a lubricant, an abrasive material, a filler, and a binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used for a disc brake of a vehicle such as an automobile or an industrial machine, and more particularly to a friction material capable of preventing the generation of low frequency brake noise. is there.

[0002]

2. Description of the Related Art Conventionally, an asbestos-based friction material containing asbestos as a main component has been used as a friction material used for a brake of an automobile or the like. However, in recent years, there has been concern about the effects of asbestos on the human body, and so-called asbestos-free friction materials that do not contain asbestos have been developed. As this asbestos-free friction material, a semi-metallic friction material using short steel fibers has been put into practical use. This is obtained by heat-molding a steel fiber as a reinforcing material, adding a large amount of graphite lubricant and metal powder, and using a phenol resin-based binder. The characteristic feature of this friction material is that it is excellent in wear resistance and fade resistance.
Fade resistance refers to the characteristic that when the brake operation or continuous operation becomes violent, the temperature of the rotor and the pad rises, the performance of the organic friction material begins to deteriorate, and a large decrease in the friction coefficient is prevented. .. However, this semi-metallic friction material has a problem that it is ignited during high-temperature braking, and the short steel fibers contained in the friction material cause great wear of the mating rotor. Therefore, as current asbestos-free friction materials, low-steel friction materials containing no more steel than necessary, or non-steel friction materials containing no steel have been developed.

[0003]

However, the low-steel and non-steel friction materials described above tend to generate low-frequency brake noise of 1 KHz or less, which is not found in conventional asbestos-type friction materials. In some cases, the vehicle is vibrated during braking, which causes a new problem of causing a great discomfort to the driver. The present invention has been made to solve such a problem, and in particular,
An object of the present invention is to provide an asbestos-free friction material capable of suppressing the generation of low-frequency brake noise of KHz or less.

[0004]

In order to achieve the above-mentioned object, the friction material of the present invention comprises a asbestos-free friction formed by thermoforming a fibrous base material, a lubricant, an abrasive, a filler and a binder. It is a material to which carbon black is added. This carbon black has a DBP adsorption amount of 80 ml / 100 g or more and an iodine adsorption amount of 80 mg / 100 g / 100 g / 100 g or more.
It is characterized in that it is used in an amount of g or less and the amount added to the friction material is more than 3% by volume and 20% by volume or less.

[0005]

The low-frequency brake noise of 1 KHz or less is a vibration noise due to the stick-slip phenomenon that occurs between the friction material and the mating rotor. In conventional asbestos-based friction materials, asbestos itself has a function of suppressing this stick-slip phenomenon. On the other hand, the carbon black particles have a chain structure, and the particles are connected by aggregation. In the present invention, by adding such carbon black, the aggregation is broken by the frictional force during braking,
As a result, the stick-slip force is reduced to suppress the generation of low-frequency brake noise. An index indicating the degree of aggregation of the particles is the DBP adsorption amount, and the larger the amount, the greater the degree of aggregation. Further, the iodine adsorption amount is related to the specific surface area, and if it is large, the specific surface area also becomes large.

[0006]

EXAMPLES Examples of the present invention will be described below. The friction material of the present invention and a comparative example were actually manufactured, and a brake noise test was conducted on both of them. First, the respective raw materials were mixed by an Erich mixer as shown in Tables 1 and 2 (the examples are represented as “actual” and the comparative examples are represented as “ratio”). In the thermoforming process, a predetermined amount of raw material was placed in a mold heated to 160 ° C. and pressure-molded for 10 minutes. The pressure value of the pressure molding was selected so that the molded friction material had a calculated porosity of 10%. Here, the classification of each raw material is steel fiber, copper fiber, aramid fiber is a fiber base material, phenol resin is a binder, carbon black, barium sulfate,
Kash dust is a filler and artificial graphite is a lubricant.
Further, each carbon black is as follows. MAF: Me
dium Abrasion Furnace, GPF: General Purpose Fu
rnace, SRF: Semi ReinforcingFurnace, ISA
F: Intermediate Super Abrasion Furnace. The porosity of the friction material was calculated from the difference between the true density and the apparent density of the friction material shown in the following formula.

[0007]

[Table 1]

[0008]

[Table 2]

[0009]

[Equation 1]

The true density of the friction material is measured by measuring the true density of each raw material by a gas replacement method such as a pycnometer.
The true density of the friction material was calculated according to the recipe. The apparent density was obtained by measuring the weight of the friction material by measuring the outer diameter of the friction material. Then, a curing process was performed at 230 ° C. for 3 hours. As a result, Comparative Examples 3 and 5 could not be molded as friction materials.

A brake noise test was conducted on the friction material molded as described above. Brake The braking schedule is shown in Table 3. Brake noise during braking was measured by using a vibration pickup, and vibration was measured by being separated into 20 KHz to 1 KHz by a bandpass filter. Then, when vibration exceeding a certain level occurred, it was counted that brake noise had occurred, brake noise generated during test braking was separated into low frequency noise and general noise, and the incidence of low frequency noise was measured. .. The results are shown in Table 4.

[0012]

[Table 3]

[0013]

[Table 4]

As shown in Table 4, as compared with Comparative Example 1 containing no carbon black, all the Examples of the present invention effectively suppress the generation of low frequency noise. In addition, Example 1
As can be seen from the comparison between Comparative Example 5, Comparative Example 5, and Example 2 and Comparative Example 4, if the amount of carbon black added is too small (Comparative Example 4), the effect of suppressing low frequency noise is small, and conversely there is too much. 5) and it becomes difficult to form the friction material. Further, even with the above addition amount, if the iodine adsorption amount is too high (Comparative Example 3), it cannot be molded as a friction material, and if the DBP adsorption amount is too low (Comparative Example 2), the low frequency suppression effect is obtained. Will be insufficient. From these results, the amount of carbon black to be added is more than 3% and 20% or less in volume%, and the DBP adsorption amount is 8%.
It was confirmed that 0 ml / 100 g or more and an iodine adsorption amount of 80 mg / g or less should be used.

[0015]

As described above, by adding a necessary amount of carbon black having a high agglomeration and a low specific surface area to a friction material, a low-frequency brake can be applied to asbestos-free friction materials such as low steel and non-steel. Noise can be effectively suppressed.

Claims (1)

[Claims] 1. An asbestos-free friction material comprising a fiber base material, a lubricant, an abrasive, a filler and a binder,
3% by volume of carbon black having a DBP adsorption amount of 80 ml / 100 g or more and an iodine adsorption amount of 80 mg / g or less
A friction material containing more than 20% by volume.