JPH01204728A - Disk brake pad - Google Patents

Abstract

PURPOSE:To contrive reduction of wear of a rotor by reducing adhesion between a disk brake pad and the rotor, by a method wherein a carbonized film is deposited on a surface part by performing carbonization treatment through resin coating and heat treatment by making use of a steel fiber as a base fiber. CONSTITUTION:An uncured solution of thermosetting resin is stuck to the surface of a steel fiber, which is heated, cured and made a resin coating film. Then the same is carbonized by raising a heating temperature. Then after carbonization, the same may be made into graphite or form the graphite by performing CVD treatment further. A brake pad is manufactured in the same manner as a normal friction material. The pad is formed by arranging the friction material 9 for a base fiber of which a steel fiber having a carbonized film is used and the friction material 8 for which the normal steel fiber is used respectively on a part where it is apt to generate dragging and the other part. The pad formed of the friction material like this can reduce wear of a rotor, carbide to be generated through wear of a carbonized film works as a lubricant and a coefficient of friction can be improved on an exposed steel surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disc brake pad using a base material mainly composed of steel fibers.

[Prior Art] A method of using steel fiber as a base material for a non-asbestos disc brake pad is known.

Steel fiber is the same type of metal as the disc rotor, and uses its adhesion to the mating material to ensure a high coefficient of friction μ. However, the adhesion of steel fibers causes friction surface roughness on the rotor surface. Therefore, the rotor 1
9! This has the disadvantage that brake vibration occurs due to the roughening of the friction surface. As a way to prevent this, configure the brake padff! ! A method of adding a lubricant to a friction material, particularly a method of adding graphite, is known. However, the addition of graphite lowers the friction coefficient μ. In addition, when the amount of graphite added is increased, the flow of the binder resin improves, resulting in a dense r! AI! ! (friction material with low porosity), which not only reduces the coefficient of friction but also adversely affects fade and brake squeal.

Furthermore, Japanese Patent Laid-Open No. 56-92982 discloses that in order to improve the wetting characteristics between steel fiber and thermosetting resin,
There is a disclosure that a liquid thermosetting resin is applied to the surface of a steel fiber in advance and cured to form a resin coating. Furthermore, JP-A-59-77138 discloses a method of forming a triiron tetroxide <Fe5Oa) film on the surface of steel fibers to improve the rust prevention properties and compressive properties of steel fibers.

[Problems to be Solved by the Invention] However, the method of coating the surface of the still fiber with a thermosetting resin, etc. does not improve the strength of the friction material obtained by improving the wettability with the binder. can. However, it is not possible to prevent still fibers from adhering to the rotor to the necessary extent. Furthermore, although the method of forming an oxide film has a rust-preventing effect, it cannot improve the friction characteristics.

The present invention has been made in view of the above points, and is a disc brake pad that reduces adhesion between the disc brake pad (hereinafter referred to as "pad") and the rotor, the main material of which is steel fiber, and improves rotor wear. The purpose is to provide the following.

[Means for Solving the Problems] The disc brake pad of the present invention is formed of steel fibers as the main base material, and the steel fibers are coated with a resin and have a carbonized film formed by carbonization treatment by heat treatment on the surface. It is characterized by being deposited on the area.

The carbonized film formed on the surface of the steel fiber preferably has a thickness of 10 μm or more. This carbonized film is made by carbonizing resin and is mainly made of carbon. The carbonized film is preferably composed mainly of graphite.

To form this carbonized film, first, an uncured solution of a thermosetting resin such as a phenol resin is applied to the surface of a steel fiber, and the solution is heated and cured to form a resin coating film. Then, the heating temperature is increased to carbonize. After carbonization, rough CVD (
It is also possible to graphitize or form graphite by performing a chemical vapor deposition method or the like.

The pad of the present invention can be manufactured in the same manner as a conventional friction material manufacturing method. In other words, steel fibers with a carbonized film formed thereon, base fibers made of a combination of metal fibers, Hiramix fibers, organic fibers, etc. as necessary, binder powder such as phenolic resin, and additives mainly to adjust friction and wear are added. The mixture is then mixed in a mixer such as a Banbury mixer to form a mixed raw material. Fill the mold with this mixed raw material! Preforming is performed by rolling and pressing to produce a rough shaped material. Next, the rough shaped material is put into a heating mold, aged, and heat treated to form an integrally hardened and bonded friction material.

[Operations and Effects of the Invention] The present invention is a disc brake pad formed of steel fibers with a carbonized film deposited on the surface portion as the main fibers. A porous friction material with low hardness, high porosity, and high compressive strain can be formed by using steel fibers with this carbonized film formed thereon.

Pads made of this friction material can reduce wear on the mating material, the rotor, by adhesion, and the carbide produced by the wear of the carbonized film acts as a lubricant, increasing the coefficient of friction on the exposed steel surface. Can be done. Furthermore, since the surface of the steel fiber is covered with a carbonized film, it is possible to prevent the steel from rusting inside the friction material.

Furthermore, pads made of steel fiber as a base material are usually used in applications that require a high coefficient of friction. Therefore, the amount of lubricant added must be reduced. However, when the amount of lubricant is reduced, adhesion with the mating material increases and wear increases.

However, in the present invention, the carbonized film on the surface of the steel fiber acts as a lubricant (therefore, it can reduce wear and increase the coefficient of friction. Also, this S vibration material is placed in a specific part of the mating material that is difficult to wear. It is possible to create a pad that is less likely to damage the mating material.

[Example] The present invention will be explained below with reference to Examples.

(Formation of carbonized film on steel fiber) Fiber diameter 5
A methanol solution of phenolic resin was sprayed onto the surface of a steel fiber with a length of 5 μm and 1 fiber length of 2 mm, and it was dried to coat the surface of the steel fiber with a thin film of resin.Then, the phenolic resin was cured by heating to about 300°C. Further, the resin layer was carbonized or graphitized by heat treatment at 1000° C. for about 1 minute under an inert gas.

Next, CVD treatment (CVD method using thermal decomposition of hydrocarbon gas) is performed at 2000°C for about 2 minutes in a vacuum atmosphere to graphitize the carbon in the carbonized film or deposit graphite, leaving a carbonized film mainly composed of graphite on the surface. A steel fiber was produced with

The coated still fiber was analyzed by XTA diffraction analysis to distinguish its crystal structure.

The thickness of this carbonized film can be determined by cutting a cross section of a friction material made by mixing steel fibers with a binder and additives and observing the surface of the steel fibers with a microscope. The coating thickness was measured and found to be 15 μm.

(Manufacture of Pad) As shown in the plan view of FIG. 9, this disc brake pad has a substantially quadrilateral thick plate shape.

A pack plate is coupled to the back surface of this pad.

Steel fiber with a carbonized film formed on the surface with the composition ratio shown in Table 1, phenolic resin, cashew dust (particle size 100 μm or less) as an organic component, rubber (particle size 500 μm or less) as an organic component, and inorganic lubricant. As metal sulfide (particle size 50μm or less), fine powder graphite (particle size 50μm or less)
μm or less), barium sulfate as an inorganic filler, (particle size 2
A mixture of 5ift (particle size of 20μm or less) was placed in the mold as an abrasive material, and a 400ka
A preform was obtained by compressing with a pressure of /cwt.

This preform was then heated and compression molded in a mold heated to 160°C to form a! Manufactured vibration material. This friction material is 1
After post-curing by holding in a heating furnace at 80° C. for 16 hours, the surface of the friction material was polished and bonded to a back plate to obtain the pad of this example. A schematic cross-sectional view of the obtained pad is shown in FIG. The steel fiber 2 has a carbonized coating 3 formed on its surface. Steel fibers 2, organic additives 10 and inorganic additives 11 are then dispersed in a binder 12 forming a matrix.

In the comparative example, a pad was manufactured with the same composition as in the example except that the steel fiber was 55% by weight and the fine powder graphite was 10% by weight D.

The physical properties of the obtained pad are shown in Table 1.

Table 1 *Amount of distortion when 2 sheets are stacked and 3 tons of pressure is applied (Example 2) A schematic diagram of the disc brake shown in FIG. 8 is shown.

When the rotor 1 idles, the upper end surface of the outer pad 6 and the lower end surface of the inner pad 7 drag against the rotor, causing the rotor to wear out (black portion).

Therefore, as shown in Fig. 9 and Fig. 10, a friction material 9 using steel fiber as a base material $111 with a carbonized film on the parts where stagnation is likely to occur (upper end surface, lower end surface) is used, and the other parts are A pad 1144B made of still fiber was placed to form a pad. When a wear test was conducted using this pad by idling the rotor, the wear of the rotor was extremely small.

(Evaluation) A rotor wear test using a pad was conducted. Evaluations were made using a brake dynamometer described in JASOM Rating 0406 using the Example product and the Comparative Example product. The test code was tested in accordance with the instructions shown in Table 2, with one cycle of repeated braking and idling. The results are shown in FIG. In FIG. 1, the vertical axis shows the amount of wear, and the horizontal axis shows the unit nicle Table 2. FIG. 2 shows a schematic cross section of the rotor and shows the measurement points at which the amount of wear was measured. The amount of wear is shown as the average value measured at six points on both sides of the rotor, at each end and in the center. In the graph of FIG. 1, in the comparative example, the amount of wear increased from the second cycle onwards, and especially rapidly increased from the fifth cycle onwards, reaching 125 μm at the end of the test. On the other hand, the rotor wear of the product of this example tends to increase as the Nycle content increases, but unlike the comparative example, the rotor wear after the test was 18 μm, which was about 14% of the comparative example, which was a good result. Ta.

Next, changes in the coefficient of friction of the pads were compared based on JASO standard C406. The results are shown in FIGS. 3 and 4. Figure 3 shows the change in the friction coefficient when the speed is 50 km/h with the second effect, and Figure 4 shows the change in the friction coefficient when the speed is 1100 km/h with the second effect.The vertical axis is the friction coefficient μ and the horizontal axis is the oil pressure. It represents.

The comparative example shows an abrasive effect in the low oil pressure range and has a high friction coefficient. However, as the oil pressure increases, the effect of the finely powdered graphite added as a lubricant becomes apparent. ! This shows a tendency for the ta coefficient to decrease.

On the other hand, in the product of this example, the initial friction coefficient is low in the low oil pressure range, but as the oil pressure increases, the carbonized film wears away and the steel fibers are exposed, thereby maintaining a high friction coefficient.

The reason for maintaining a higher coefficient of friction is that in this example, as shown in the physical property values in Table 1, the hardness is small, the porosity is large, and the compressive strain resistance is large, so the rotor and friction material fit well. (The contact area became more uniform and the contact area increased).

Furthermore, a low friction coefficient at low pressure and a high porosity have the effect of improving brake squeal characteristics. Figure 5 shows 11! at low pressure! A correlation diagram between friction coefficient and brake squeal occurrence rate is shown. The higher the friction coefficient, the more likely it is that brake squeal will occur, but in the case of this example, the brake squeal generation rate is low and the friction coefficient is also located at a favorable position (white circle). Figure 6 is a diagram showing the correlation between the porosity of the friction material and the squeal generation rate.

The incidence of squealing is higher when the porosity is smaller. The porosity of this example (white circles) indicates that the porosity is at a low level with a low squeaking occurrence rate. Therefore, it is a friction material with excellent brake squeal characteristics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the amount of wear in Examples and Comparative Examples.
Figure 2 is a cross-sectional view of the rotor and shows the wear a measurement point, Figures 3 and 4 are graphs showing changes in the coefficient of friction due to changes in oil pressure, Figure 3 is at a speed of 150 km/h, Figure 4 is at a speed of 110
It is 0k/h. FIG. 5 is a graph showing the correlation between the squeal generation rate and the friction coefficient at low pressure, and FIG. 6 is a graph showing the correlation between the II friction coefficient and the porosity. Fig. 7 is a schematic cross-sectional view of the pad, Fig. 8 is a schematic plan view showing the state of the pad and rotor during idling, Fig. 9 is a friction surface of the inner pad, and Fig. 10 is a friction surface of the outer pad. FIG. 1... Rotor 2... Steel fiber 3... Carbonized coating 4... Pad 5... Back plate 6... Outer pad 7... Inner pad 8... Pad 9 made of steel fiber. ...Pad made of still fiber with carbonized film 10...Organic additive 11...Inorganic additive 12.
...Binding resin patent applicant Toyota Motor Corporation representative Patent attorney Hiroshi Okawa Figure 2 M M M Figure 3 Figure 4: ii￥L (kgt/Cm) Porosity ['/,] Figure 7

Claims (1)

[Claims] (1) In a disc brake pad formed of steel fibers as the main base fibers, the steel fibers are coated with a resin and carbonized by heat treatment to form a carbonized film deposited on the surface. A disc brake pad featuring: