Metal deforming – By shot-blasting
Reexamination Certificate
1999-03-25
2001-08-07
Larson, Lowell A. (Department: 3725)
Metal deforming
By shot-blasting
Reexamination Certificate
active
06269669
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a friction component for brakes and clutches for vehicles, and the like, and more particularly to a method of surface-treating a back plate of the friction material.
DESCRIPTION OF THE RELATED ART
A friction component, used for disk brake pads, brake shoes, clutch plates, and the like for automobiles is formed by integrally bonding a back plate made of ferric metal to friction material.
To the friction component is applied relative movement while being pressed between a disk rotor and a mated clutch plate, and frictional force generated at that moment causes an automobile to be stopped or driving force of an engine to be transmitted to wheels. As a result, considerably large sharing force is applied to the friction material and the back plate. Therefore, it is required to provide strong bonding force between the friction material and the back plate to bear the above-mentioned large sharing force.
In order to obtain strong bonding force to meet the above object, it has conventionally been carried out to make a bonding surface of the back plate rough to such an extent, as to be the surface roughness (average roughness on center line) Ra=2-7 &mgr;m to increase bonding surface and bonding force. Further, rust, oxidized film, or the like on the bonding surface of the back plate may cause the bonding force to be decreased, so that the both removal of the rust, the oxidized film and so on as well as rust preventing treatment are also important.
From this point of view, conventionally, the back plate, of which surface is made rough, and from which rust, oxidized film and the like are removed, is covered by forming film of zinc calcium phosphates of which thickness is approximately 3 &mgr;m to 5 &mgr;m, and then, primer material is spread on the film and is baked thereon to form a primer layer of approximately 15 &mgr;m to 25 &mgr;m. In other words, these forming film and primer layer function to prevent rust. On the other hand, bonding to the friction material is conducted through the primer layer and a newly applied bonding agent on the primer layer.
By the way, when the surface of the back plate is too rough, a portion of the back plate may penetrate the primer layer at the formation of the primer layer, which causes rust to be generated, and the rust may reach inside of the back plate. On the contrary, if the surface roughness of the back plate is too small, the improvement of bonding force can not, be expected. It is therefore the best to obtain maximum surface roughness so far as there is no fear that the primer layer is not penetrated. This preferable range is (Ra=)2 &mgr;m to 7 &mgr;m as described above.
Therefore, in the above-mentioned processes, the process of obtaining rough surface of the back plate is very important. Conventional method of obtaining rough surface is further described below.
Back plates are formed through striking process with a press from steel plate or the like, and on the surface of the steel plate or the like before formation or machining is attached rust, oxidized film, and the like. Further, at the striking process or the like, a great amount, of lubricant and rust preventing oil are adhered to the surface. The existence of the oil and oxidized film may reduce bonding force, so that it, is preferable to remove them.
Then, a back plate subjected to formation is firstly de-fatted with chlorine solvent to remove oil such as rust preventing oil. Then, with dry-grid-blast method, grid particles of cast iron are struck to the back plate through a rotor or the like to make the surface of the back plate rough up to Ra=2 &mgr;m to 7 &mgr;m described above, and at the same time, oxidized film and the like are removed. After that, forming film of zinc calcium phosphate is formed to prevent rust, and further primer material is applied thereon and is baked, then friction material is adhered thereto with bonding agent.
In the above-mentioned method, however, there are problems that remarkably large amount of lust is generated and chlorine solvent is used. To avoid these problems, wet-blasting method has been used. This method is advantageous also since blasting process and de-fatting are simultaneously carried out. In this method, many works are fed into a barrel, and while the barrel rotates the works are subjected to blasting treatment by blasting water (slurry) containing grinding particles to the works rotating in the barrel through high pressure air. The slurry is obtained by mixing alumina grinding particles, and further adding alkali de-fatter by about several percents thereto. This is a wet method, so that no dust is generated. In addition, alumina grinding particles are strong in grinding force, so that a prescribed surface roughness is achieve in a short period of time, and at the same time, with this method, de-fatting function is preferably provided due to the mixing of alkali de-fatter.
However, with this method, alumina is hard and brittle, so that when blasted to the works the alumina grinding particles are liable to be broken, resulting in generation of dusts and sludge. Further, edge portions generated at, the break sometimes become remarkably sharp, and the sharp edges penetrate the back plate and remains on the surface of the works, causing bonding force to be lowered. In addition, alumina grinding particles are repeatedly used, but the alumina particles recovered become drastically smaller and smaller as they are broken, which increases the amount of slurry and finally desired surface roughness can not be obtained. As a result, alumina grinding particles must be replaced every two weeks. In this case, slurry containing alumina must, have totally been replaced and waste fluid must be disposed as industrial waste.
Further, with the above-mentioned method, the directions of the works in the barrel are scattered in all directions, so that the directions of the works must manually be adjusted on a conveyor one by one just before sending the next process, therefore, it is impossible to reduce manpower and the efficiency itself is not good.
Still further, since material to be treated after blasting is zinc calcium phosphate, waste fluid treating facility unfavorably becomes large.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned fact, and it is therefore an object of the present invention to provide a method of surface-treating back plates of friction material in which desired surface roughness is securely obtained for a long period of time. Further object of the present, invention is to provided the method to automatically transport works from blasting process to the next. Still further object of the present invention is to provide the method with which waste fluid treating facility is made small even when forming treatment is conducted.
To achieve the above objects, a surface-treating method for a back plate for friction material according to the present invention is characterized in that slurry containing particles made of plastic material is blasted through high pressure air to a surface of a back plate for friction material.
It is possible to arrange the back plates on a conveyor and blast the slurry containing the particles made of plastic material through high pressure air from upside of the conveyor.
After the above surface treatment, de-fatting may be conducted on the extension of the conveyor, and then, forming treatment with phosphate may be carried out; the above-mentioned plastic material may be substantially ball-shaped; and the plastic material may be stainless steel or titanium.
Further, in the above method, the back plate for friction material can be made of ferric metal; the slurry may repeatedly be used through a circulation route; it is possible to install a magnet on the circulating route of the slurry; and ferric rust, steel powder and the like in the slurry can be removed through magnetic force.
REFERENCES:
patent: 4115076 (1978-09-01), Hitzrot, Jr.
patent: 5193375 (1993-03-01), Meister
patent: 5456
Matsubara Tohru
Seki Kazuhiro
Larson Lowell A.
Muramatsu & Associates
Nisshinbo Industries Inc.
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