JP2612960B2 - Friction material pad - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material pad, and more particularly to a friction material used for a friction type brake of a vehicle such as an automobile or an industrial machine, for braking with a disk rotor interposed therebetween. About the pad.

[Prior Art] Conventionally, asbestos-based friction materials containing asbestos as a main component have been used as friction materials for brakes of automobiles and the like. However, in recent years, there has been a concern about the effect of asbestos on the human body, and so-called asbestos-free friction materials that do not use asbestos have been developed. That is, as an asbestos-free friction material, a semi-metallic friction material using steel short fibers has been put to practical use. However, this semi-metallic friction material has a problem that it is ignited at the time of high-temperature braking, and also has a problem that short steel fibers contained in the friction material cause large wear of the rotating disk rotor. Therefore, as current asbestos-free friction materials, low-steel friction materials that do not contain steel unnecessarily or non-steel friction materials that do not contain steel at all have been developed, and high-temperature braking generated by semi-metallic friction materials has been developed. The problem of ignition and wear of the rotating disk rotor could be solved.

However, compared to conventional asbestos-based friction materials, low-frequency brake noise of 1 KHz or less is more likely to occur, and in some cases, the braking may be accompanied by vibration of the vehicle body, causing a great deal of discomfort to the driver. There is a new problem of giving. As a measure against this low frequency noise,
2. Description of the Related Art Conventionally, friction materials have been developed in which the effect of suppressing or reducing the generation of low-frequency noise can be obtained by the composition and arrangement of the friction materials.
A number of friction materials having a coating on the surface have been proposed, but most of them are aimed at improving the initial braking characteristics and preventing normal squeal.

Most of the coating agent also uses an organic binder. These are, for example, Japanese Patent Publication No. 50-25
No. 932, JP-B-53-20536, JP-A-55-63025
Japanese Patent Application Laid-Open Nos. Sho 56-734645, Sho 59-166735, Sho 62-106134, and the like.

By the way, the condition where low frequency noise is most likely to occur is
It is a combination of a continuous use disk rotor and a new pad.
That is, this is a combination immediately after replacing only worn pads with new ones at the time of vehicle inspection or the like. Under such conditions where low-frequency noise is likely to occur, use pads with low-frequency noise countermeasures with the composition of the friction material.Also, always replace the disk rotor when replacing the pad. It is considered that the occurrence of low frequency noise can be reduced by polishing the surface of the disk rotor with sandpaper to remove the deposits on the surface of the disk rotor.

[Problems to be Solved by the Invention] However, among the above-mentioned ones that use low-frequency noise with a composition of a friction material, a car on which a different kind of friction material pad has been mounted is used as a new pad. It is not easy to install a friction material pad with low frequency noise countermeasures above because of the change in braking characteristics, etc. There is a problem that leads to an increase in cost. Further, the method of polishing the surface of a continuously used disk rotor using sandpaper or the like has a problem that a very troublesome operation of polishing the disk rotor surface is involved. Among the friction materials coated on the surface as a countermeasure against the above-described high-frequency noise, those disclosed in Japanese Patent Publication No. 53-20536 have been disclosed in Japanese Patent Application Publication No. Sho 53-20536. A friction material to which a conductive resin is fixed has been disclosed. However, in the case of using such an organic binder, a combination of a continuously used disk rotor and a new pad has little effect on noise reduction as described later. Results were also obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and when a new pad and a continuous use disk rotor are combined at the time of vehicle inspection or the like, the replacement cost can be easily increased without increasing the replacement cost. It is another object of the present invention to provide a friction material pad capable of reducing generation of low-frequency noise.

[Means for Solving the Problems] A friction material pad according to the present invention is a friction material pad for braking with a disk rotor interposed therebetween, and is fixed to a surface of a pad portion which is opposed to and contacts the disk rotor. And polishing means made of only alkali silicate. Preferably, the friction material pad of the present invention is more effective when the above-mentioned disk rotor is used continuously.

[Operation] In the friction material pad according to the present invention, the pad portion is disposed so as to be in contact with the disk rotor, and a polishing means made of only alkali silicate for polishing the surface of the disk rotor is fixed to the surface of the pad portion. Therefore, when a new pad and a continuously used disk rotor are combined, wear powder and the like adhering to the disk rotor surface are polished and removed.

In general, when the disk rotor is used continuously, abrasion powder and the like adhere to the disk rotor, and the disk rotor turns black. If a new pad is used in this state, low-frequency noise is likely to occur as described above. On the other hand, the low-frequency noise of 1 KHz or less is considered to be caused by the stick-slip phenomenon between the brake disk of the partner disk rotor and the brake friction material. further,
It is considered that the stick-slip phenomenon is more likely to occur as the friction material having a large static friction coefficient and a small dynamic friction coefficient, that is, the friction coefficient ratio R (= static friction coefficient μs / dynamic friction coefficient μd) increases.

[Embodiment of the Invention] Table 1 shown below is a table showing evaluation conditions by a combination of a disk rotor and a pad, Table 2 is a table showing a braking schedule of a brake noise test, and a third table is shown.
The table shows the results of measurement of the friction coefficient ratio R under the evaluation conditions in Table 1 under the braking conditions in Table 2.
7 is a table showing the results of measuring the low-frequency noise generation rate under the evaluation conditions shown in the table and using the braking conditions in Table 2. Table 5 is a table showing the types of coating agents of Examples 1 to 3 and Comparative Examples 1 to 4, and Table 6 is a table showing no coating agent treatment and Examples 1 to 3 and Comparative Example 1. 6 is a table showing low-frequency noise generation rates measured under the evaluation conditions C and D for the cases where the coating agents of Nos. To 4 were applied.

First, the present inventors investigated why low frequency noise is likely to occur in a combination of a continuous disk rotor and a new pad. Specifically, using the braking conditions shown in Table 2 in accordance with the evaluation conditions in Table 1 above, the friction coefficient ratio in the combination with the new disk rotor / new pad and the combination with the continuous disk rotor / new pad was actually When R was measured, as shown in Table 3, the value of the friction coefficient ratio R in the combination of the continuous disk rotor and the new pad (evaluation condition D) was larger. Table 1 and 4
As is clear from the table, it is found that the deposit on the continuous disk rotor contributes to the generation of low frequency noise.

That is, it is considered that abrasion powder adheres to the disk rotor and peculiar sliding occurs with a new pad, resulting in a large friction coefficient ratio R and low frequency noise. As a result of examination based on these facts, it has been clarified that by removing the deposits on the continuous disk rotor, the generation of low frequency noise in the combination of the continuous disk rotor and the new pad can be reduced. Here, as means for removing the deposits on the continuous rotor, polishing of the disk rotor surface by sandpaper or the like as described above can be considered.
However, removing and polishing the disk rotor each time the pad is replaced is a very laborious task.

Thus, the present inventors have devised a method of coating the surface of the pad with a polishing material to some extent and removing the deposits on the continuous disk rotor by the first few brakings after replacing the pad. That is, a coating agent having a polishing action was searched for.

As shown below, it has been found that the use of an alkali silicate (water glass) such as sodium silicate as a coating agent has an effect of reducing the occurrence of low frequency noise.

First, the asbestos-free friction material was coated with various coatings, and a noise test was performed on the friction material for brakes.

The type of the coating agent is shown in Table 5. In Examples 1 to 3 and Comparative Examples 1 and 2, the coating agent was air-dried for 1 hour after brush application, and further dried at 150 ° C. for 1 hour to be fixed. . Further, for Comparative Examples 3 and 4,
After the brush coating, the film was air-dried for 1 hour and further dried at 200 ° C. for 1 hour to be fixed. In Comparative Example 4, 5% by weight of the thermosetting resin was used.
Is added. In addition, as the friction material pad to be coated, an asbestos-free friction material pad which has a market record at present is used.

Here, in the alkali silicate system as in Examples 1 to 3,
Air drying alone results in high solubility in water after fixation, and may re-gel depending on the surrounding temperature and humidity. Therefore, in order to stabilize the quality, it is necessary to dry at least 100 ° C. or harden using a hardener such as salts in order to remove physically absorbed moisture.

The noise test is based on the braking schedule shown in Table 2 (1.
After performing the fitting and 2. the braking test), the friction material pad was replaced with a predetermined friction material pad, and the noise generation rate when only the 2. braking test was performed in the braking schedule was evaluated.
Here, the number of brakings after the replacement with the predetermined friction material pad is 35 times. Also, referring to Table 2, the conditions of the braking test were implemented by a combination of each deceleration and each temperature before the start of braking. The braking noise during braking is measured using a vibration pickup, and the vibration is measured at 20Hz to 1K by a bandpass filter.
Hz. Then, when a certain level of vibration or more is generated, it is counted that the brake noise has occurred, and the brake noise generated during the test braking is separated into a low-frequency brake noise and a general brake noise to separate the low-frequency brake noise. The incidence was calculated by the following formula.

As shown in Table 3, the friction coefficient ratio R, which is the ratio between the static friction coefficient μs and the dynamic friction coefficient μd, has a large evaluation condition D and small evaluation conditions C and A. Further, as shown in Table 4, the evaluation condition D, which is a combination of the continuous disk rotor and the new pad, has the highest low frequency noise generation rate. This indicates that the occurrence of low-frequency noise is caused by the disk rotor, and that the rate of low-frequency noise can be reduced by removing the deposits on the disk rotor.

Also, as shown in Table 6, as a coating agent,
Example 1 using sodium silicate was the most effective under the evaluation condition D, and the noise generation rate of Example 1 was the case where no treatment was performed with the coating agent, and the noise between the new pad and the new disk rotor was small. It is almost at the same level as in the case of the combination evaluation condition C. In addition, it can be seen that the same curing as in Example 1 can be obtained with alkali silicates as in Examples 2 and 3.

In addition, the coating agents evaluated this time have been worn out in the braking test (35 braking times), and fluctuations in the braking characteristics do not pose any particular problem.

As described above, in the present embodiment, the pad surface is coated with alkali silicate and fixed, so that the occurrence of low-frequency noise can be effectively reduced even when a combination of a disc rotor for continuous use and a new pad is used. Can be.

[Effects of the Invention] As described above, according to the present invention, the polishing means made of only alkali silicate is fixed to the surface of the pad portion opposed to the disk rotor so as to be in contact with the new pad. When the combination with the used disk rotor is used, wear powder and the like adhering to the disk rotor surface are polished and removed. It has been possible to provide a friction material pad capable of easily reducing the occurrence of low-frequency noise without increasing the cost.

Claims (2)

(57) [Claims] 1. A friction material pad for braking with a disk rotor interposed therebetween, the polishing means comprising a polishing means made of only alkali silicate, which is fixed to a surface of a pad portion opposed to and arranged in contact with the disk rotor. Including, friction material pad. 2. The friction material pad according to claim 1, wherein said disk rotor is used continuously.