JPH0446228A - Disc brake assembly - Google Patents

Abstract

PURPOSE:To suppress the low frequency noise by constituting the outer pad of a disc brake from the frictional member which contains reinforced fibers and does not contain asbestos and uses the binder selected from thermosetting resin and rubber and using the substance selected from silicate and hydroxides of specific metals. CONSTITUTION:A brake is driven by a piston 5 in a cylinder 4, and a rotor 1 is squeezed by an outer pad 6 and an inner pad 7. The outer pad 6 is made of a frictional member which contains the reinforcing fibers and does not contain as bestos and a frictional material which is joined by a bonding agent selected from thermosetting resin and rubber and contains silicate having a laminar crystalline structure which does not contain molybdenum disulfide and graphite and at least one kind selected from the hydroxides of Al, Mg, and Fe. The outer pad which tends to generate low frequency noise is constituted as described in the above, and the low frequency noise is suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a friction material type disc brake assembly used in vehicles such as passenger cars or industrial machines, and in particular, relates to a friction material type disc brake assembly that can prevent the generation of low-frequency brake noise. It relates to a disc brake assembly.

[Prior Art] Conventionally, asbestos-based friction materials containing asbestos have been used as friction materials for brakes of automobiles and the like. However, in recent years there has been growing concern about the effects of asbestos on the human body, and so-called asbestos-free friction materials that do not use asbestos have been developed.

That is, semi-metallic friction materials using short steel fibers have been put into practical use as asbestos-free friction materials. The semi-metallic friction material is made by using steel fiber as a reinforcing material, adding a large amount of graphite lubricant and metal powder, and heat-forming it using a phenolic resin binder. The performance characteristics of semi-metallic friction materials include excellent wear resistance and fade resistance. What is this fade resistance?
When braking or continuous braking becomes intense, the temperature of the rotor and pad increases and the performance of the organic friction material begins to deteriorate, which is a characteristic that prevents a significant drop in the coefficient of friction. However, this semi-metallic friction material has the problem of igniting during high-temperature braking, and also has the problem that short steel fibers contained in the friction material cause large wear on the mating rotor. Therefore, current asbestos-free friction materials include low-steel friction materials that do not contain more steel than necessary, or non-steel friction materials that do not contain steel at all. Furthermore, there are many friction materials for brakes that are made of a combination of two or more different materials. Some of them are listed below.
Shown in the table.

(Left below) Most of the above-mentioned known technologies improve braking characteristics,
This is intended to prevent uneven wear and normal winding. Also, No. 6 in Table 1. The friction materials described in each publication No. 8 have some similarities with the material of the present invention, but
Asbestos material is used as the friction material of the brake described in Publication No. 5, and the materials of the inner pad and outer pad are not specifically defined. No.

The friction material described in Publication No. 8 also uses asbestos material, and the arrangement relationship of the friction material, which is a combination of two different materials, is also not common to the present invention.

[Problems to be Solved by the Invention] However, the above conventional friction materials have the following problems.

Raw steel-based friction materials and non-steel friction materials can solve the problems of ignition during high-temperature braking and wear of mating rotors that occur with semi-metallic friction materials, but conventional asbestos-based friction materials 1kHz not seen in
A new problem has arisen in that low-frequency brake noise below z is likely to occur, and in some cases, the vehicle may be accompanied by vibrations during braking, causing great discomfort to the driver and the like.

In view of the above conventional problems, the present invention provides a disc brake assembly using a brake friction material that does not generate low-frequency brake noise during braking by devising the composition combination and arrangement of materials. The purpose is to

[Means for Solving the Problems] The disc brake assembly of the present invention includes an inner pad installed on the driving means side of the disc brake with respect to the brake disc, and a caliper installed on the driving means, which is connected to the brake disc. The outer pad fixed to the tip of an arm extending outwardly of the driving means holds both sides of the brake disc, and the driving means clamps the brake disc, and the inner pad and outer pad facing each other sandwich both sides of the brake disc. This relates to a brake disc that applies braking force by applying pressure to the brake disc. The characteristics of this disc brake assembly are that the friction materials that make up the inner pad and the outer pad have different compositions, and the outer pad is made of a friction material that contains reinforcing fibers and does not contain asbestos, such as phenolic resin, epoxy resin, It is bonded with a binder selected from other thermosetting resins and rubber, and is further combined with silicate having a layered crystal structure that does not contain graphite, molybdenum disulfide, etc., which are known as solid lubricants, and aluminum, magnesium, It is characterized by being made of a friction material containing at least one substance selected from various iron hydroxides.

Alternatively, the present invention provides a disc brake assembly having the same basic configuration as above, in which at least the vicinity of the outer periphery of the outer pad is made of a friction material containing reinforcing fibers and free of asbestos, such as phenolic resin, epoxy resin, or other heat-resistant material. It is bonded by a binder selected from curable resin and rubber, and is further combined with a silicate having a layered crystal structure that does not contain graphite, molybdenum disulfide, etc., which are known as solid lubricants, and aluminum, magnesium,
It includes a friction material containing at least one substance selected from iron hydroxides.

[Operation] Low frequency brake noise of IKHz or less is said to be caused by the stick-slip phenomenon that occurs between the brake disc of the mating rotor and the brake friction material.

The present inventors have investigated in what part of the brake pad this stick-slip phenomenon occurs; in other words, is it the entire surface of the brake pad, a part of it, or the inner pad side that is placed on the side that is fixed to the vehicle body? I investigated whether it was on the other side of Outerbad. As a result, the outer pad side has inferior rigidity compared to the inner pad side with respect to fluctuations in friction caused by stick-slip occurring between the mating rotor and the brake friction material.
It was discovered that the movement of the brake friction material was greater than that of the inner pad, promoting stick-slip. In addition, it was found that stick-slip was larger on the outer circumferential side than on the inner circumferential side of the friction material on the rear pad side. This is thought to be due to the difference in surface pressure distribution between the outer circumferential side and the inner circumferential side. As a result of studies based on these facts, we found a way to solve the problem of reducing low-frequency noise by selecting a material that is less likely to cause stick-slip as the friction material on the outer pad side.

On the other hand, it is generally believed that the stick-slip phenomenon occurs more easily when a friction material has a large static friction coefficient and a small dynamic friction coefficient, that is, a friction coefficient ratio R (= static friction coefficient μ, / dynamic friction coefficient μd). So this R
Focusing on this, we searched for materials that suppress stick-slip. As a result, mica, talc, vermiculite,
Silicates and iron with layered crystal structures such as kaolin,
It was found that aluminum and magnesium hydroxides are effective in reducing R. However, each of these raw materials has a common problem in that when added in a sufficient amount to suppress low frequency noise, fade resistance deteriorates. Therefore, by using a friction material with poor anti-fade properties but less likely to cause ice slip on the outer pad side and a friction material with excellent anti-fade properties on the inner pad side, we can maintain good anti-fade properties. , it became possible to suppress low frequency noise.

In addition to silicates with a layered structure such as mica, vermiculite, and talc, they have a layered structure with hydroxides of iron, magnesium, and aluminum, and are used as raw materials for brake pads to suppress low frequency noise. Effective for noise suppression.

Also, patent application No. 1-241570 filed by the present inventors
As explained in the above issue, even more effective low-frequency noise reduction effects can be obtained by using these materials in combination.

[Example] Examples for demonstrating the characteristics of the disc brake assembly of the present invention will be described below with reference to the drawings.

The disc brake assembly used in the performance evaluation tests in each of the following examples is schematically shown in FIG. 1. This disc brake assembly includes a rotor 1, a fixed support 3 supporting a caliper 2, a brake driving means consisting of a cylinder 4 and a piston 5, and a pair of disc pads, an outer pad 6 and an inner pad 7.
It is equipped with The outer pad 6 and the inner pad 7 are arranged on both sides of the rotor 1, and the outer pad 6 is fixed to the arm 2a of the caliper 2 and is arranged so as to be in contact with the outer surface of the rotor 2.

The inner pad 7 contacts the piston 5 and rotates the rotor 1.
The brake disc 1a is arranged so as to be in contact with the inner surface of the brake disc 1a. When pressurized brake fluid is introduced into the cylinder 4, the pressure chamber 8 therein expands and pushes the piston 5 to the left in FIG.
Push to the right.

As a result, the outer pad 6 and the inner pad 7 come into close contact with each side of the brake disc 1a of the rotor 1,
The desired braking force is applied. Note that the rotor 1 rotates together with the wheels around the axle 11 via bearings 12a and 1.2b.

Next, a performance evaluation test of the disc brake assembly of the present invention will be explained. First, brake friction materials for performing a performance evaluation test were mixed using an Eirich mixer with the compositions shown in Formulas A to D in Table 2.

(Leaving space below) Note 1) Note 2) Note 3) Note 4) Table 2 Composition of friction material (%) Kanto Steel #1-3 R18 Thickness 60 μm x length 3 mm DuPont Kevlar ■ At203: 49% , 5in2:51% 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 for pressure molding was selected to be an appropriate value so that the molded friction material had a calculated porosity of 10%. The porosity of the friction material was calculated using the difference between the true density and apparent density of the friction material as shown in the formula below.

[True density co=[apparent density]3/[100-porosity]/
100 The true density of the friction material was determined by measuring the true density of each raw material using a gas replacement method such as a pycnometer, and calculating the true density of the friction material according to the recipe.

Further, the apparent density was determined by volume measurement based on the weight and outer diameter of the friction material.

The curing process was carried out at 230° C. for 3 hours.

Further, in order to obtain the friction material 6a as shown in FIG.
Raw materials were separately charged and thermoformed so that the dimensions shown in the figure were h = 50 mm and a = 15 mm.

Using the friction material prototyped as described above, the following (1)
- (3) Three types of tests were conducted.

(1) Performance evaluation test to analyze the relationship between the combination of compound compositions of each friction material 6a, 7a of outer pad 6 and inner pad 7 and low frequency noise characteristics. A shown in Table 2
A brake noise test was conducted using the disc brake assembly shown in FIG. 1 using friction materials of -D in combinations shown in Table 3. 4th brake braking schedule
Shown in the table.

(Margin below) Table 3.

Composition of wear materials for outer pads and inner pads] A-D is! I! This corresponds to formulations A-D in Table 12.

Table 4.

Braking Schedule for Braking Noise Test Brake noise during braking was measured using a vibration pickup, and vibration was measured by separating it into 20 Hz to IKHz using a band pass filter. Then, if a vibration of a certain magnitude or higher occurs, it is counted as brake noise occurring, and the brake noise generated during test braking is separated from low-frequency noise and general brake noise, and low-frequency brake noise is detected. The incidence was calculated. The results are shown in Table 5.

(Leaving space below) (Note) The conditions for "2. Braking test" were carried out using combinations of each deceleration and each temperature before starting braking.

Table 5.

Brake noise test results Note) Low frequency noise occurrence rate, number of noise occurrences/number of braking times
100 (%) As is clear from Table 5, in the case of Examples 1 to 4 in which a friction material containing at least one of mica, talc, and Mg (OH2) was used on the outer pad side, the friction Compared to Comparative Example 1 in which no material was used on the outer pad side, the incidence of low frequency noise could be significantly suppressed.

(2) Performance evaluation test to analyze the relationship between the arrangement of the composition of the friction material of the outer pad and brake noise characteristics Next, as the friction material 7a on the inner pad side, the composition A shown in Table 1 was fixed. , friction material 6a on the outer pad 6 side
A brake noise test similar to that described above was conducted under the conditions shown in Table 4 using products made from a combination of two different raw materials shown in Table 6 below. The results are shown in Table 7.

(Margin below) Table 7.

Brake noise test results Table 6.

Arrangement of the composition of the friction material of the outer pad) Inner pad is fixed with composition A A-D correspond to formulations A-D in Table 2.

As is clear from Table 7, in Examples 5 to 7, the outer pad 6 side contains at least mica, talc, and Mg(OH)2 in the outer peripheral portion of the friction material 6a (the portion indicated by P in FIG. 2). In this case, generation of low frequency noise could be suppressed compared to Comparative Examples 2 and 3, which did not contain these raw materials in the outer peripheral portion.

(3) Performance evaluation test regarding braking characteristics.
A fade test was conducted using a dynamometer for the combinations shown in the table. The test schedule for this fade test was a partially modified version of JASOC406-74. The test conditions are shown in Table 8.

(Left space below) Table 9 shows the results of the above fade test and the measurement results of fade μm, which is the minimum dynamic friction coefficient μ during the fade test.

(Margin below) Table 8, Fade test conditions Table 9.

As is clear from Table 9 of the fade test results, a friction material 6a having at least one of mica, talc, and Mg(OH)2 on both sides of the outer pad 6 and the inner pad 7;
By using 7a, the fade μ. 1 degree significantly decreases by 1 degree (Example 4), but by using the friction material 7a with good fade resistance on the inner pad 7 side, the fade μff11. ．． It can be seen that it is possible to prevent a decrease in

[Effects of the Invention] As described above, the disc brake assembly of the present invention has the following effects.

(1) Low-frequency brake noise is suppressed by using a friction material that is less prone to stick-slip as the friction material on the outer pad side. Therefore, by first suppressing low-frequency noise by using a material that is less prone to stick-slip as the friction material on the outer pad side, and by selecting the friction material on the inner pad side, other performance can be adjusted, resulting in extremely high performance. We can provide high-performance disc brake assemblies.

(2) The tendency for stick-slip to occur near the outer periphery of the friction material on the outer pad side plays a major role in the generation of low-frequency noise. , low frequency noise can be suppressed. Therefore, by selecting the inner circumference of the friction material on the outer pad side and the friction material on the inner pad side, other performance can be adjusted, making it possible to provide an extremely high-performance disc brake assembly. Become.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing the configuration of a disc brake assembly to which the present invention is applied. FIG. 2, FIG. 3, and FIG. 4 are diagrams showing the outline of the shape of the friction material prototyped for the performance evaluation test of the disc brake assembly of the present invention. In the figure, 1 is the rotor, 1a is the brake disc, 2
is a caliber, 2a is an arm, 4 is a cylinder, 5 is a piston, 6 is an outer pad, 6a is a friction material, 7 is an inner pad, and 7a is a friction material. Figure 1 Figure 2 Figure 3 Figure 5, ノ■ Figure 4 7a: J Liao material

Claims (2)

[Claims] (1) An inner pad installed on the drive means side of the disc brake with respect to the brake disc, and fixed to the end of the arm of the caliper attached to the drive means, which extends from the brake disc to the opposite side of the drive means. In a disc brake assembly that applies braking force by applying pressure to an inner pad and an outer pad that sandwich both sides of a brake disc and are opposed to each other so that the driving means clamps the brake disc, The compositions of the friction members constituting the inner pad and the outer pad are different from each other, and the outer pad is a friction material containing reinforcing fibers and not containing asbestos, and is made of a phenolic resin, epoxy resin, or other thermosetting resin. Silicate, which has a layered bonding structure that does not contain graphite and molybdenum disulfide as a solid lubricant, and aluminum, magnesium,
A disc brake assembly comprising a friction material containing at least one substance selected from iron hydroxides. (2) An inner pad installed on the drive means side of the disc brake with respect to the brake disc, and an inner pad fixed to the tip of an arm extending from the brake disc of the caliper attached to the drive means to the side opposite to the drive means. In a disc brake assembly that applies braking force by applying pressure to an inner pad and an outer pad that sandwich both side surfaces of a brake disc and are opposed to each other so as to clamp the brake disc by the driving means, at least The vicinity of the outer periphery of the outer pad is made of a friction material that contains reinforcing fibers and does not contain asbestos, and is bonded with a binder selected from phenolic resin, epoxy resin, other thermosetting resins, and rubber, and further , contains at least one substance selected from silicates with a layered crystal structure that do not contain graphite and molybdenum disulfide as solid lubricants, and hydroxides of aluminum, magnesium, and iron. A disc brake assembly characterized by being made of a friction material.