JPH07109362A - Friction member - Google Patents

Abstract

PURPOSE:To prevent the production of rust on the joint face of a back plate and a friction material. CONSTITUTION:A friction material layer having pH of >=9 is formed between a back plate and a friction material. The adjustment of pH can be carried out by using an alkaline substance such as slaked lime, sodium nitrite and alkali dust. The rust-proofing property of the joint face of the back plate and the friction material is further improved by incorporating the friction material layer with powder or fiber of a metal having an ionization tendency larger than that of iron or by subjecting the back plate to a chemical conversion treatment such as soft nitriding treatment. The thickness of the friction material layer is generally 0.5-3mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake pad, a drum brake shoe, a clutch plate, etc. used for a brake, a clutch and the like of automobiles and industrial machines.
The present invention relates to a friction member composed of a steel back metal and a friction material integrally bonded to the surface thereof, and particularly to a friction member for preventing rusting of a joint surface between the metal back and the friction material.

[0002]

Friction materials used for automobile disc brake pads, drum brake shoes, etc. play an important role in converting kinetic energy into heat energy by frictionally engaging with the disc rotor and brake drum which are the counterpart members. I carry it. Therefore, the friction material always generates heat and becomes high temperature. Therefore, such a friction material is required not only to have heat resistance and wear resistance, but also to have stable friction characteristics with a small change in friction coefficient due to temperature changes, and low aggression with respect to a mating member.

Therefore, in order to satisfy these various characteristics, the friction material is formed as a composite material. That is, the friction material is generally composed of a fiber base material forming a skeleton, a resin binder for binding and holding the fiber base material, and various fillers dispersed and filled in a matrix of these fibers and the binder. Has been done. As the fiber base material, inorganic fiber such as glass fiber, organic fiber such as aramid fiber, metal fiber such as steel fiber, etc. are used, and as the resin binder, thermosetting resin such as phenolic resin is used. Alternatively, a crosslinkable rubber is used. Further, as the filler, barium sulfate, a constitutional filler such as calcium carbonate, a solid lubricant such as graphite or coke,
Organic polymer powders such as cashew dust which is a cured product of cashew oil, abrasives such as silica, and other additives for adjusting friction are used. Here, the solid lubricant is used to improve the wear resistance of the friction material and to secure the thermal stability of the friction coefficient. Especially, in recent years, as the performance of automobiles has been improved, graphite materials such as graphite have been used. In combination, metal sulfides such as molybdenum disulfide and lead sulfide are used. And this metal sulfide maintains the function as a solid lubricant especially in a high load region (high temperature region).

Such a friction material is integrally joined to a steel back metal forming a support thereof and used as a disc brake pad or the like. Conventionally, this bonding is generally performed by adhesion, and a thermosetting resin adhesive such as a phenol resin or an epoxy resin or a crosslinkable rubber adhesive is used. In some cases, the friction material may be joined to the back metal simultaneously with the molding of the friction material by press-molding the compounded composition of the friction material on the back metal.

Here, it is necessary that the friction material and the back metal are firmly bonded together, and if rusting or the like occurs on the bonding surface, the bonding force decreases, and eventually the friction material seems to come off from the back metal. There is a danger of falling into danger. So, from the past, in general,
The surface of the back metal to which the friction material is joined is subjected to chemical conversion treatment such as rust-preventing primer treatment and iron phosphate treatment.

[0006]

However, even in the friction member thus treated with the primer or chemical conversion treatment for rust prevention, rust still occurs on the joint surface between the backing metal and the friction material. Cases were often found. The occurrence of this rust was particularly large in the disc brake pads of RV vehicles that have become widespread in recent years. As described above, such rusting weakens the bondability between the friction material and the back metal, and if this progresses strongly, there is a risk that the friction material will eventually peel off from the back metal.

Therefore, a new measure for this rust prevention was required, but when the present inventor investigated the cause of this rust, the following was found. That is, the friction material is originally acidic due to carboxyl groups of organic polymers such as cashew dust contained therein or organic acids such as formic acid generated by thermal decomposition during heat molding thereof, or hydrochloric acid ions contained as impurities. The occurrence of rust on the back metal is caused by oxidation of metal sulfides such as molybdenum disulfide described above included as a filler in the friction material under high heat, rather than by these acids, and sulfurous acid or It must be based on the corrosive action of sulfuric acid. Also, this corrosion action should be caused by oxides of chromium and copper that are added in some cases to improve friction. And, such a corrosive action is further enhanced under conditions where expansion and contraction due to heating and cooling are repeated in a cold region, and under an environment where electrolytic corrosion is likely to occur in a salt-damaged region such as a coast. And so on.

Then, the present inventor has conducted further studies based on these findings, and as a result, the above-mentioned rust generation on the joint surface between the back metal and the friction material has an alkaline friction material layer interposed therebetween. It has been found that this can be advantageously prevented or reduced.

[0009] Therefore, an object of the present invention is to provide a friction member having improved rust preventive property of a joint surface between a backing metal and a friction material.

[0010]

The friction member of the present invention comprises a steel backing and a friction material containing a fiber base material, a resin binder, and a filler to be bonded to the backing metal, and between these, PH
9 or more friction material layers are interposed.

By interposing the alkaline friction material layer in this way, the acidic components in the friction material are neutralized, and the generation of rust on the joint surface of the backing metal with the friction material can be suppressed. Therefore, the higher the PH of this friction material layer, the more preferable, and it is generally preferable that the PH is 9 or more. And, more preferably, the pH is 10 or more. However, extremely high PH is not preferable because it adversely affects the friction material and the backing metal. In this sense, the PH of the friction material layer is preferably 12 or less.

The friction material layer having a PH of 9 or more (hereinafter, this friction material layer is simply referred to as a rust preventive layer for the sake of distinction from the friction material body) is formed of an arbitrary or special compounding composition. You can However, the bondability with the friction material body,
It is preferable that the rust preventive layer is formed from the same composition as that of the main body of the friction material from the viewpoints of ease of molding and uniformity of the entire friction material. And such a rust preventive layer can be formed at the same time when the friction material main body is formed, whereby a friction material having an integrated rust preventive layer can be obtained.

Any material can be used as the alkaline substance for adjusting the pH of the rust preventive layer to 9 or more. However, alkaline dusts such as slaked lime (calcium hydroxide), sodium nitrite (sodium nitrite), and blast furnace slag powder are particularly preferable in terms of thermal stability, ease of handling, and cost. And these can be used individually or in combination as appropriate.

Further, powder or fibers of a metal having an ionization tendency larger than that of iron Fe can be added to the rust preventive layer, whereby electrolytic corrosion of iron forming the back metal is reduced, and the back metal and the friction material. It is possible to further improve the rustproof property of the joint surface with. Examples of such a metal include chromium Cr, aluminum Al, magnesium Mg and the like, but zinc Zn is preferably used.

Such a rust preventive layer, that is, a friction material layer having a PH of 9 or more can be generally formed with a thickness of 0.5 to 3 mm. The thicker the alkaline layer is, the more improved the rust prevention property is. However, sufficient corrosion resistance can be obtained with a relatively small thickness, and a thickness of about 3 mm or less is generally sufficient. Further, if the thickness is too small, sufficient rust preventive properties cannot be obtained, so 0.5 mm or more is preferable.

Further, in the present invention, since the rust preventive layer is interposed between the back metal and the friction material as described above, the rust preventive power of the back metal can be sufficiently enhanced, and it is necessary to particularly perform the rust preventive treatment on the back metal as in the conventional case. There is no. However, it is more preferable to apply an appropriate anticorrosion treatment to the back metal, whereby the anticorrosion property of the back metal can be more perfect. One of such rust preventive treatments is soft nitriding treatment. This soft nitriding treatment is roughly classified into a method performed in a gas phase and a method performed in a salt bath, but any of these methods is also possible. Then, by this, a compound layer mainly composed of Fe-CN system is formed on the surface of the backing metal, the thickness of which is the treatment time, the heating temperature,
Further, there is a close relationship with the cyanide concentration, and as the treatment time is longer, the treatment temperature is higher, and the cyanide concentration is higher, a thicker compound layer is formed.
However, it goes without saying that there is a limit to the thickness of the layer formed in this way, but in practice, the thickness of this compound layer is generally preferably 5 μm to 40 μm. This soft nitriding treatment not only improves the rust prevention property, but also improves the bending strength of the backing metal due to its high compound layer, which allows the backing metal to be thinner and the weight of the backing metal to be lighter. Can be obtained. In addition, other suitable anticorrosion treatment method,
This is a conventional chemical conversion treatment for iron oxide, iron phosphate, zinc phosphate, etc. These treatments are also preferable for forming the base of the adhesive.

When the friction member of the present invention is manufactured, the rust preventive layer may be formed separately from the friction material main body and then integrated with the main body of the friction material. It is preferable that the friction material main body is molded at the same time as the friction material main body with the same composition as the material main body. Specifically, a predetermined material is filled with a compounding material of the friction material main body to which an alkaline substance is added, lightly pre-pressed and then the compounding material of the main body layer is filled, and then both are integrally added. It is pressure heating. This makes it possible to easily form the friction material including the rust preventive layer without any special operation. Then, the friction material including the rust preventive layer is adhered and bonded onto the back metal by a usual method using a phenolic resin or the like. In this case, the friction material including the anticorrosion layer can be directly pressure-heat-molded on the back metal, in which case the adhesion and the friction material molding are simultaneously performed.

In the present invention, the fibrous base material constituting the friction material body includes glass fibers, rock wool, silicate fibers, alumina fibers, carbon fibers, potassium titanate fibers, inorganic fibers such as slag wool, steel fibers, Examples thereof include metal fibers such as stainless steel fibers and copper fibers, aramid fibers, novoloid fibers, nylon fibers, organic fibers such as rayon fibers. And
These may be used alone or in combination as appropriate depending on the specific type or application of the friction material. As the resin binder, phenol resin, epoxy resin, melamine resin, polyimide resin, polyester resin, rubber such as SBR, etc. can be used. Further, as the filler, any of the above-mentioned body filler, solid lubricant, organic polymer powder, abrasive agent, and other additives for improving friction performance can be used.

The friction member of the present invention can be constructed as a disc brake pad, a drum brake shoe, a clutch plate, or the like by using a suitable backing member and mixing the materials as described above and the method. .

[0020]

In the friction member of the present invention, as shown in the following examples, the joint surface of the backing metal with the friction material maintains good rust prevention. This is the sulfurous acid generated in the friction material,
It is considered that corrosive substances such as sulfuric acid are effectively neutralized by the friction material layer having a PH of 9 or more, and the corrosive action on the back metal made of steel is prevented. Further, this rust preventive action is further enhanced by adding a metal powder or fiber having an ionization tendency larger than that of iron Fe to the friction material layer, or by subjecting the back metal to a chemical conversion treatment such as soft nitriding treatment. Can be improved.

[0021]

EXAMPLES The present invention will be specifically described below by way of examples in which the present invention is applied to a disc brake pad.

(Production of Pad and Composition of Friction Material) FIG. 1 shows a composition of a friction material layer having a PH of 9 or more (hereinafter, simply referred to as a rust preventive layer) according to an embodiment of the present invention. Further, the comparative example does not have a rust preventive layer, and therefore the composition shown in FIG. 1 is the composition of the friction material itself. And
The friction material body in the example has the composition of this comparative example.

As shown in FIG. 1, the rust preventive layers in Examples 1 to 5 are basically composed of the same composition as that of the friction material main body in this example. That is, as the fiber base material,
A mixture of 5% by weight copper fiber, 3% by weight steel fiber, 8% by weight aramid fiber and 8% by weight potassium titanate fiber was used. Here, the aramid fiber is specifically Kevlar fiber (manufactured by DuPont). Further, specifically, a phenolic resin is used as the resin binder, and is used at 12% by weight. Furthermore, as the filler, graphite and lead sulfide, which are solid lubricants, are used at 5% by weight and 10% by weight, cashew dust at 10% by weight, and barium sulfate, respectively.

Although 39% by weight of this barium sulfate is used in the friction material main body, part of it is replaced with an alkaline material or the like in the rust preventive layers in Examples 1 to 5. That is, 5% by weight of slaked lime in Examples 1 and 6, 5% by weight of sodium nitrite in Example 2, a mixture of 3% by weight of slaked lime and 10% by weight of alkaline dust in Example 3, and 3% by weight of slaked lime in Example 4. And 3% by weight of sodium nitrite, and in Example 5, 5% by weight of slaked lime and 5% by weight of zinc powder, respectively.

The pad was manufactured as follows. The composition of the anticorrosion layer of Examples 1 to 6 well mixed in advance in the mold was uniformly filled, and the surface of the friction material was flattened by lightly pressing the composition, and then the friction material body having the composition shown in Comparative Example was prepared. Was filled with the mixture and was pressed at room temperature to form a preform of the friction material having a rust preventive layer. On the other hand, a pad backing made of steel having a thickness of about 6 mm was surface-treated by shot blasting or the like for cleaning, and then a phenol resin adhesive was applied and dried. Then, a preform of a friction material having a rust preventive layer is overlaid on the back metal coated with this adhesive, and the temperature is 160 ° C. and the pressure is 40 in the mold.
It was thermoformed at 0 kg / cm ² for 10 minutes and then heat-treated at 250 ° C. for 120 minutes. As a result, a disc brake pad was obtained in which the friction material was integrally joined to the back metal via the rust preventive layer. The rust preventive layer had a thickness of about 2 mm and the friction material had a thickness of about 18 mm.

Similarly, a comparative pad having no rust preventive layer was prepared. In Example 6 and Comparative Example 2, the back metal was soft-nitrided in advance. Specifically, the back metal was immersed in a molten cyanide salt bath for 30 minutes for soft-nitriding treatment.

(Rust Generation Test) A rust generation test (rust test) was performed on the disc brake pads of the examples and comparative examples thus produced.

In this rust test, the following steps 1) to 6) are defined as 1 cycle (1 day) and 30 cycles (30 days)
It was done by repeating.

1) Immersion in 5% saline at room temperature (about 25 ° C.) for 1 hour 2) Drying at 105 ° C. for 1 hour 3) Leave at -30 ° C. for 2 hours 4) Atmosphere of 35 ° C. and 90% humidity Leave for 16 hours 5) Leave for 2 hours at 200 ° C 6) Leave for 2 hours at room temperature Then, after rusting the back metal by this rust test,
According to JASO C44-78, the joint surface between the back metal and the friction material (anticorrosion layer) was sheared to remove the friction base material, and the ratio (%) of the area of the base material remaining on the back metal was calculated.

Further, the friction base material remaining on the back metal was removed by immersing it in a solution of caustic soda, and the ratio of the rusted area of the back metal was calculated.

(Results and Discussion) FIG. 1 shows the ratio (%) of the remaining area of the base material and the ratio (%) of the rusted area calculated as described above. Note that FIG. 1 also shows the separately measured PH of the friction material (rust preventive layer).

As shown in these results, Examples 1 to 6 in which an alkaline friction material layer (rust preventive layer) is interposed between the back metal and the friction material are comparative examples in which the friction material is directly adhered to the back metal. On the other hand, the anticorrosion effect is significantly improved in both cases. This rust-preventing effect is enhanced as the alkalinity of the friction material layer (rust-preventing layer) is increased, and by addition of zinc powder, which is a metal having a greater ionization tendency than iron Fe, or by soft nitriding the back metal. , Is further enhanced.

Here, PH of the friction material main body is in Comparative Examples 1 and 2.
As shown in Fig. 3, the PH5 level is shown and it is acidic. For example, the cashew dust itself has a PH of 3 to
Although it depends on the fact that it is as low as about 4, it is considered to be based on sulfurous acid or sulfuric acid generated by the thermal decomposition of lead sulfide added as a solid lubricant as described above. And
It is considered that the corrosive action of the back metal due to these acid components is prevented by the neutralizing action of the alkaline friction material layer (rust preventive layer).

[0034]

As described above, in the friction member of the present invention, PH9 is provided between the steel backing and the friction material integrally bonded to the backing including the fiber base material, the resin binder and the filler. The above friction material layer is interposed. Therefore, corrosion of the back metal due to the acidic component of the friction material is prevented, and good bonding between the back metal and the friction material can be maintained for a long period of time. Further, since the friction material layer having a PH of 9 or more can be easily formed by adding an alkaline substance such as slaked lime, sodium nitrite, and alkali dust to a normal friction material, the friction material has no characteristic. There is no loss.
Further, by adding powder or fibers of a metal having an ionization tendency larger than that of iron Fe to the friction material layer, or by subjecting the back metal to chemical conversion treatment such as soft nitriding in advance, the surface of the back metal to be joined to the friction material The rust resistance of is further improved. Further, such a friction member of the present invention can be advantageously applied as a disc brake pad used in a severe corrosive environment such as an AV vehicle.

[Brief description of drawings]

FIG. 1 is a composition (weight%) of a friction material layer of a disc brake pad in Examples and Comparative Examples of the present invention, its PH, and a base material remaining area (%) after a rust test and a rust generation area ( Is a table showing the measurement results of (%).

Claims (7)

[Claims] 1. A friction member comprising a backing made of steel and a friction material containing a fibrous base material, a resin binder, and a filler bonded to the surface of the backing. PH9 is provided between the backing and the friction material. A friction member including the above friction material layer. 2. The friction member according to claim 1, wherein the friction material layer contains slaked lime. 3. The friction member according to claim 1, wherein the friction material layer contains sodium nitrite. 4. The friction member according to claim 1, wherein the friction material layer contains alkali dust. 5. The friction member according to claim 1, wherein the friction material layer contains powder or fibers of a metal having an ionization tendency smaller than that of iron. 6. The friction member according to claim 1, wherein the friction material layer has a thickness of 0.5 to 3 mm. 7. The friction member according to claim 1, wherein at least a surface of the backing metal to which the friction material is joined is subjected to chemical conversion treatment such as soft nitriding treatment.