KR101035240B1 - A low-steel type friction material and a brake for vehicle comprising the low-steel type friction material - Google Patents

Abstract

Provided are a rostil friction material and a vehicle brake including the same.

The rostil friction material according to the present invention is characterized by including a solid lubricant having a particle size of 180 to 220 μm and an abrasive having a particle size of 0.5 to 10 μm. The lostil friction material according to the present invention is stable due to a small change in the friction coefficient according to the speed and the braking deceleration, and has excellent resistance in terms of friction characteristics due to its excellent resistance to fading.

Description

A low-steel type friction material and a brake for vehicle comprising the low-steel type friction material}

The present invention relates to a rothyl-based friction material, and more particularly, to a rothyl-based friction material and a brake including the improved braking property and resistance to fade.

A brake friction material is a function of decelerating, braking, and clutching wheel or machine operation by frictional force on the surface (drum or disk) that faces the friction material, and generates kinetic (driving) energy due to friction. It means the device which converts into heat energy.

In the early 1900s, these friction materials were first made of woven fabrics made by impregnating cotton or asphalt with cotton fabrics, and since 1906, brake friction materials (linings) mainly composed of asbestos, which has excellent thermal safety, Was used for the first time in the braking system, and in 1960, when a phenol resin was developed, a friction mold-based friction material began to be produced in earnest from 1960.

Asbestos was identified as a carcinogen by the US Environmental Protection Agency (EPA) in the late 1980's, as a result of the regulation of various products, asbestos-based friction materials began to be developed. Has been steadily developed around non-steel friction materials that do not contain steel fibers and low-steel friction materials that contain steel fibers.

The use range of such friction materials is widely used in industrial machines, railway wheels, aircrafts, ships, etc., mainly in automobiles, and the amount of use of friction materials is increasing every year.

Friction material for automobile brake is generally composed of about 8 ~ 20 kinds of different raw materials, and its components are divided into about 6 kinds. In general, the components of friction material are matrix and binder. , Fillers, abrasives, lubricants, friction modifiers, and the like.

Each of these constituent materials is added in an appropriate amount to obtain the friction characteristics required for automobile braking, and it is common practice that the type and content of the constituent materials used are generally not disclosed as the know-how of the friction material producer.

The friction characteristics required for the braking of the vehicle are largely classified into stability and durability, and the stability is determined by the friction coefficient, the stability of the friction coefficient, the fade and recovery, the mechanical strength, and the like. This is determined by the relative surface damage and the presence of discomfort.

These frictional properties are determined by the raw materials of the friction material components, their composition ratios and mixing methods, and subsequent manufacturing processes.

The raw material of the friction material component is to examine the properties of the raw material, such as strength, hardness, melting point to screen the material to meet each role, size, surface treatment, density, etc. also affect the selection criteria. The compositional blending ratio varies with the fraction between the components. The friction material manufacturing process is carried out in the order of material weighing, mixing of materials, pre-form, hot-press molding, and post-curing process, and then the surface pressure, processing temperature and processing time of the molding process. Accordingly the friction characteristics can be adjusted.

On the other hand, the friction material containing the steel fiber of the fiber (fiber) serving as a substrate of the friction material components are commonly referred to as low-steel type brake lining (friction material that does not contain steel fiber) Is called non-steel type brake lining.

Among these, the Rothle brake friction material is thermally stable and has excellent strength and coefficient of friction, but has a disadvantage in that an insulating material for insulation with the brake pad body is required because of the high aggression and abrasion of the disc and the high thermal conductivity.

Conventional rostil friction material to solve this drawback used strain-based phenolic resin as a binder, but the strain-based phenolic resin has a disadvantage that the price is expensive, and the friction energy is mostly converted to heat during braking during high-speed driving There was a problem in the fade phenomenon in which the friction coefficient is lowered by increasing the temperature of the friction material and the disk, and the recovery phenomenon in which the friction coefficient is reduced during cooling to room temperature after the fade phenomenon.

Accordingly, the first problem to be solved by the present invention is to provide a rothyl-based friction material with improved braking properties and resistance to fade.

The second problem to be solved by the present invention is to provide a brake for a vehicle including the rostige friction material.

In order to achieve the first object of the present invention,

Provided is a rothyl-based friction material comprising a solid lubricant having a particle diameter of 180 to 220 µm and an abrasive having a particle diameter of 0.5 to 10 µm.

According to one embodiment of the invention, the solid lubricant may be graphite, antimony trisulfide, zinc sulfide, copper sulfide or mixtures thereof.

According to another embodiment of the present invention, the abrasive may be zirconium silicate, alumina, silicon dioxide, magnesium oxide or mixtures thereof.

According to another embodiment of the present invention, the volume percent of the solid lubricant may be 13 to 15.

According to another embodiment of the present invention, the volume% of the abrasive may be 4-6.

According to another embodiment of the present invention, the rostil-based friction material may further include a fiber base, a binder, a filler and a friction control agent.

According to another embodiment of the present invention, the volume percentage of the binder may be 9-11.

According to another embodiment of the present invention, the volume% of the filler may be 30 to 34.

According to another embodiment of the present invention, the volume percentage of the friction modifier may be 14 to 16.

According to another embodiment of the present invention, the binder may be a commercial phenol resin or a modified phenolic resin.

According to another embodiment of the present invention, the fiber substrate may be steel fibers, organic fibers, ceramic fibers, bronze fibers, copper fibers or mixtures thereof.

According to another embodiment of the invention, the friction modifier may be cashew dust, nitrile butadiene rubber or mixtures thereof.

According to another embodiment of the present invention, the filler may be calcium hydroxide, barite or mixtures thereof.

The present invention provides a brake for a vehicle including the rostial friction material in order to solve the second problem.

The lostil friction material according to the present invention is stable due to a small change in the friction coefficient according to the speed and the braking deceleration, and has excellent resistance in terms of friction characteristics due to its excellent resistance to fading. In addition, the abrasive and the solid lubricant according to the present invention have a small particle size and are uniformly distributed in the friction material, thereby improving the friction characteristics of the friction material, thereby increasing the binder and the bonding area, thereby increasing the existing expensive strain-type phenolic resin binder. It will be possible to replace with a commercial phenolic resin binder, which is inexpensive to manufacture, which would provide a significant advantage in the art.

The braking characteristic of the friction material is greatly influenced by the presence or absence of a transfer film formed between the friction material and the rotor, which is a counterpart, and its thickness and composition. Among the various materials constituting the friction material, abrasives and solid lubricants play an important role in determining the friction characteristics, and their type and content greatly influence the coefficient of friction and wear rate. In addition, solid lubricants and abrasives that play opposite roles in terms of friction film formation exhibit different characteristics depending on the temperature range.

The abrasive used in the friction material is added to remove the thermally deformed friction film on the rotor surface and also to adjust the friction force, and the solid lubricant is used to stabilize the friction coefficient, wear resistance, judder, and braking distance. It is added to adjust the noise characteristics.

Accordingly, the present inventors have focused on the fact that, in the case of using the same type of abrasives and solid lubricants as well as the relative amounts of lubricants and abrasives, they show different aggressiveness and wear patterns according to particle size and shape. And a test were carried out, and based on the results, the rostial friction material according to the present invention was completed.

The rostil-based friction material according to the present invention is characterized by including a solid lubricant having a particle size of 180 to 220 μm and an abrasive having a particle size of 0.5 to 10 μm, wherein the friction material has a speed and a brake within a particle size range of the solid lubricant and the abrasive. It is stable because the change of the friction coefficient with the deceleration is small, and the resistance to fade (fade resistance) is improved.

It is preferable that the particle size of the abrasive is 0.5 to 10㎛. If the thickness is less than 0.5㎛, the initial friction coefficient increases as the contact area between the abrasive and the counterpart increases, thereby reducing the frictional stability and fading at high temperatures. This is because when the thickness exceeds 10 µm, the abrasive is not evenly distributed, and the function of the abrasive is degraded, and the aggression is increased and the amount of wear of the counterpart is increased.

The particle size of the solid lubricant is preferably 180 to 220 μm, because if the particle size is less than 180 μm, the role of the solid lubricant to mitigate the aggressiveness of the abrasive is insufficient. This is because the difference is increased and it is not evenly distributed when mixed with the abrasive, which worsens the friction characteristics.

In the present invention, the solid lubricant is preferably graphite, antimony trisulfide, zinc sulfide, copper sulfide, or a mixture thereof, but is not particularly limited as long as it is a conventional solid lubricant used in friction materials.

In the present invention, the abrasive is preferably zirconium silicate (ZrSiO ₂ ), alumina (Al ₂ O ₃ ), quartz (SiO ₂ ), magnesium oxide (MgO) or a mixture thereof, but is not particularly limited as long as it is a conventional abrasive used in friction materials. Do not.

In the present invention, the volume percent of the solid lubricant is 13 to 15, and the volume percent of the abrasive is preferably 4 to 6, because the amount of wear of the friction material and the abrasive when the volume fraction of the solid lubricant is less than 13% by volume. When the increase is greater than 15% by volume, there is a problem that the friction coefficient falls, and when the volume fraction of the abrasive is less than 4% by volume, the coefficient of friction and the fade resistance are decreased, and when the amount is greater than 6% by volume. This is because the counterpart material is damaged or the amount of wear increases.

In the present invention, the rostil-based friction material further includes a fiber base, a binder, a filler and a friction control agent in addition to the abrasive and the solid lubricant.

It is preferable that the volume% of the binder is 9 to 11, because when the volume fraction of the binder is less than 9% by volume, it is difficult to provide sufficient bonding force between the friction material components, so that the strength of the friction material decreases, and exceeds 11% by volume. This is because the noise increases.

The volume% of the filler is preferably 30 to 34, because the wear resistance is increased when the volume fraction of the filler is less than 30% by volume, and the effect of the filler is insignificant when the volume fraction of the filler is more than 34% by volume. Because.

Preferably, the volume percentage of the friction modifier is 14 to 16, because the noise increases when the volume fraction of the friction modifier is less than 14% by volume, and the frictional coefficient decreases and the high temperature property exceeds 16% by volume. This is because there is a risk of worsening.

In the present invention, the binder is preferably a commercial phenolic resin (straight phenolic resin) or strain-based phenolic resin, but is not particularly limited as long as it is a binder commonly used in friction materials. In particular, in the present invention, by limiting the particle diameter of the abrasive and the solid lubricant as described above to increase the bonding area between the binder and the friction material component, it is possible to use not only strain-based phenol resins but also commercially available phenol resins with low manufacturing cost.

In the present invention, the fiber base is preferably steel fiber, organic fiber, ceramic fiber, bronze fiber, copper fiber or a mixture thereof, but is not particularly limited as long as it is conventionally used for rostil-based friction material.

Examples of the organic fibers include carbon fibers, aramid fibers, aramid pulp, polyimide fibers, polyamide fibers, phenol fibers, cellulose or acrylic fibers, and the like, and ceramic fibers include rock wool, potassium titanate, and the like. And other inorganic fibers such as willlastonite, sepiolite, attapulgite and artificial mineral fibers.

In the present invention, the friction modifier is preferably cashew dust, nitrile butadiene rubber (NBR) or a mixture thereof, but is not particularly limited as long as it is commonly used in friction materials.

The filler is preferably calcium hydroxide (CaOH), barite or a mixture thereof, but is not particularly limited as long as it is commonly used in friction materials.

The rostil-based friction material according to the present invention is manufactured through a mixing, preforming, hot press molding, and post curing process. In more detail the preparation method, first, the friction material composition is uniformly blended in a suitable mixer such as a Henschel mixer, a Lodge mixer or an Aririch mixer, and the formulation is preformed in a mold. Next, the preform is hot pressed at a temperature of 130 to 200 ° C. and a pressure of 10 to 100 MPa for a time of 2 to 15 minutes, and then the hot press is heat treated at 140 to 250 ° C. for 2 to 48 hours. After the post-curing, the coating and baking, and if necessary, the surface polishing treatment to produce a rothyl-based friction material.

The vehicular disk of the present invention is characterized by including the above-mentioned friction-based friction material.

The lostil friction material according to the invention can be used in a wide range of applications including brake linings, clutch facings, disc pads, paper clutch facings and brake shoes in automobiles, heavy trucks, railway vehicles and various types of industrial machinery.

Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples. However, these Examples and Test Examples are intended to illustrate the present invention in more detail, it is apparent to those skilled in the art that the scope of the present invention is not limited by these Examples and Test Examples. .

Example

Example 1

Roastil Friction material

In the present invention, Example 1 was a rostil-based friction material having a composition and composition ratio (volume fraction) as shown in Table 1 below.

Component  volume% importance Binder Commercial Phenolic Resin 10.60 1.3 Fiber base



Kevlar 5.90 1.4 Rock wool 8.20 2.32 Cut copper 1.10 8.65 Bronze fiber 1.10 8 Steel wool 5.10 7.5 Organic friction modifier
Cashew dust 8.50 1.28 NBR 7.00 0.96 Abrasive Zirconium Silicate (ZrSiO ₂ ) 5.60 4.43 Solid lubricant
Graphite 11.30 2.6 Luborid 3.30 3.05 filling
Calcium Hydroxide (CaOH) 4.00 2.2 Barite 28.30 4.3

In Example 1, as shown in Table 1, polyamide resin-based Kevlar ^™ was used as the organic fiber, rock wool was used as the ceramic fiber, and copper pieces, bronze fiber, and steel wool were used as the metal fiber. In addition, a commercial phenol resin was used as the binder.

In addition, a zirconium silicate having a particle size of 1 μm was used as the abrasive, and a solid lubricant used was graphite (particle size of 200 μm) and ruboride ^™ .

After the friction material component of Table 1 was prepared, the mixture was uniformly mixed in a lodge mixer of 1200rpm or more, and preformed for 2 minutes by adding a surface pressure of 400Kgf / cm ² at room temperature. The preform was hot pressed for 6 minutes by adding a surface pressure of 300 Kgf / cm ² at a temperature of 180 ° C., followed by post-curing at 200 ° C. for 2 hours and 240 ° C. for 4 hours to prepare a rothyl-based friction material.

Comparative Example 1

Roastil Friction material

In the present invention, a rothyl-based friction material having a composition and composition ratio (volume fraction) as shown in Table 2 was used as Comparative Example 1.

Component  volume% importance Binder Xyloke 10.60 1.3 Fiber base



Kevlar 5.90 1.4 Rock wool 8.20 2.32 Cut copper 1.10 8.65 Bronze fiber 1.10 8 Steel wool 5.10 7.5 Organic friction modifier
Cashew dust 8.50 1.28 NBR 7.00 0.96 Abrasive Zirconium Silicate (ZrSiO ₂ ) 5.60 4.43 Solid lubricant
Graphite 11.30 2.6 Luborid 3.30 3.05 filling
Calcium Hydroxide (CaOH) 4.00 2.2 Barite 28.30 4.3

The composition of Comparative Example 1 is the same as the composition of Example 1 (see Table 1), but as shown in Table 2, a zirconium silicate having a particle size of 75 μm with an abrasive and a point using a modified phenolic resin xylock as shown in Table 2 There is a difference in using and using a graphite having a particle diameter of 200 μm as a solid lubricant.

The manufacturing method of the friction material of the comparative example 1 is the same as the manufacturing method of Example 1, but only a difference is used in the component of Table 2.

Test Example

Friction Performance Test

The friction performance test was performed using a 1/5 scale dynamometer, and the test was performed by mounting a gray cast iron disk and the friction material of Example 1 or Comparative Example 1. Friction performance (effect test and fade & recovery test) was devised by devising a modified test method of JASO 406C-P1, which is a proven test method to see the change of friction coefficient according to speed and braking deceleration and increase of friction coefficient with temperature increase. Tested.

Table 3 shows the procedure and conditions of the test.

Referring to Table 3, the test procedure is as follows. First, preburnishing was performed in order to make the newly produced friction material uniformly contact the counterpart (rotor) surface. 1 and 2 show the results of the above-described preversity test of Comparative Example 1 and Example 1. FIG. Next, perform a first effectiveness test to determine the change in friction coefficient for braking deceleration and then reburnishing to remove the effect on the first effectiveness test. The first 1st Fade & Recovery test was then performed.

Thereafter, after the second reversing, the second 2nd Fade & Recovery test was performed, and after the third reversing, the second efficacy test was performed.

speed
(km / h) duration
(sec) IBT (℃) Braking deceleration (g) repeat
Count Reference Preburnish
(Preburnish) 65 - 120 0.3 200 Constant torque
(Constant Torque) 1st effect test
(1st Effectiveness)

50 - 80 0.1 to 0.6 6 or more at each speed

Constant pressure
(Constant Pressure)

100 0.1 to 0.8 130 0.1 to 0.8 1st Liberty
(Reburnish) 65 - 120 0.3 40 Constant torque
(Constant Torque) 1st Fade & Recovery

base line
check
(Base line
check) 50 - 100 0.3 3 Constant torque
(Constant Torque) Fade
exam
(Fade
test) 100 - 100 at first brake application 0.45 10 Constant torque-constant time
(Constant Torque-Duration time)
Recovery
exam
(Recovery test) 50 50 - 0.35 12 2nd Liberty  Same as 1st Liberty 2nd Fade & Recovery  Same as 1st fade & recovery 3rd Liberty  Same as 1st Liberty 2nd effect test  Same as 1st effect test

The IBT denotes an initial brake temperature, the interval of repetition refers to the number of brakings during the test, and the duration time is determined until the speed is increased again after the braking is completed during the test. It means the time interval.

(1) effect test result

Figure 3 shows the first efficacy test results of Comparative Example 1.

Figure 4 shows the second efficacy test results of Comparative Example 1.

3 and 4, as the braking deceleration increases, the friction coefficient tends to decrease, and as the speed increases, the friction coefficient decreases. As for the difference of the friction coefficient according to the braking deceleration of the comparative example 1, the maximum value was about 0.21 and the minimum value was about 0.12. In addition, as the speed increases, the friction coefficient difference of about 0.1 is shown. That is, in Comparative Example 1, it can be seen that the friction coefficient as a whole exists in the range of about 0.30 to 0.62.

Figure 5 shows the first efficacy test results of Example 1.

Figure 6 shows the second efficacy test results of Example 1.

Referring to FIGS. 5 and 6, in Example 1, unlike the Comparative Example 1, the coefficient of friction did not show a tendency to decrease as the braking speed was increased, and the variation in the friction coefficient was smaller than that of Comparative Example 1. Can be. The maximum width of the change in the friction coefficient of Example 1 was about 0.16 and the minimum was 0.05. Overall, the coefficient of friction is in the range of about 0.35 to 0.57, and the range is narrower than that of Comparative Example 1, indicating that the friction performance is stable.

(2) Fade  & Recovery  Test result

Figure 7 shows the first fade & recovery test results of Comparative Example 1.

Figure 8 shows the second fade & recovery test results of Comparative Example 1.

Referring to FIGS. 7 and 8, in Comparative Example 1, the friction coefficient of about 0.1 was decreased in the fade test, and the friction coefficient was recovered in the recovery test.

9 shows the results of the first fade & recovery test of Example 1. FIG.

10 shows the second fade & recovery test results of Example 1. FIG.

9 and 10, in the case of Example 1, the maximum reduction of the friction coefficient in the fade test is 0.07, which is on average less than that of Comparative Example 1, it can be seen that the recovery phenomenon is similar to Comparative Example 1. .

When referring to the friction performance test results, the change of the friction coefficient according to the speed and the braking deceleration is less in Example 1 according to the present invention than in Comparative Example 1, and the resistance to fade is also reduced in Example 1 according to the present invention. It can be seen that the improvement.

In conclusion, by adjusting the particle diameters of the solid lubricant and the abrasive as in Example 1 according to the present invention, the friction coefficient is stable due to the small change of the friction coefficient according to the speed and the braking deceleration, and thus the friction material having improved resistance to fading can be manufactured. It can be seen that there is.

1 shows the results of the prevernish test of Comparative Example 1. FIG.

2 shows the results of the prevernish test of Example 1. FIG.

Figure 3 shows the first efficacy test results of Comparative Example 1.

Figure 4 shows the second efficacy test results of Comparative Example 1.

Figure 5 shows the first efficacy test results of Example 1.

Figure 6 shows the second efficacy test results of Example 1.

Figure 7 shows the first fade & recovery test results of Comparative Example 1.

Figure 8 shows the second fade & recovery test results of Comparative Example 1.

9 shows the results of the first fade & recovery test of Example 1. FIG.

10 shows the second fade & recovery test results of Example 1. FIG.

Claims (14)

A rostil friction material comprising a solid lubricant having a particle diameter of 180 to 220 μm and an abrasive having a particle size of 0.5 to 10 μm, The solid lubricant is graphite, antimony trisulfide, zinc sulfide, copper sulfide or a mixture thereof, and the abrasive is zirconium silicate, silicon dioxide, magnesium oxide or a mixture thereof. delete delete The rostil friction material according to claim 1, wherein the volume percentage of the solid lubricant is 13 to 15. The rostil-based friction material according to claim 1, wherein the volume% of the abrasive is 4-6. The rostil-based friction material according to claim 1, further comprising a fiber base, a binder, a filler, and a friction modifier. 7. The rostil-based friction material as claimed in claim 6, wherein the volume% of the binder is 9-11. 7. The rostil friction material according to claim 6, wherein the volume% of the filler is 30 to 34. 7. The lost steel friction material according to claim 6, wherein the volume percentage of the friction regulator is 14 to 16. 7. The rostil-based friction material as claimed in claim 6, wherein the binder is a commercial phenol resin or a modified phenol resin. 7. The rostil-based friction material according to claim 6, wherein the fiber base material is steel fiber, organic fiber, ceramic fiber, bronze fiber, copper fiber or a mixture thereof. 7. The rostil-based friction material as claimed in claim 6, wherein the friction modifier is cashew dust, nitrile butadiene rubber or a mixture thereof. 7. The rostil-based friction material as claimed in claim 6, wherein the filler is calcium hydroxide, barite or a mixture thereof. A brake for a vehicle comprising the rostial friction material according to any one of claims 1 to 13.

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