Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
1999-05-06
2001-06-12
Morgan, Eileen P. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S029000, C451S061000, C451S076000
Reexamination Certificate
active
06244934
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a method for blasting an inside surface of a cylinder, in which an inside surface of a cylinder of a workpiece, for example, an internal combustion engine cylinder is blasted.
The methods for blasting an inside surface of an internal combustion engine cylinder includes a method in which the surface of a base material is roughened by blasting as a preceding process of thermal spraying and a method in which a blast deposit is formed (for example, a method disclosed in Japanese Patent Provisional Publication No. 8-333671 (No. 333671/1996)).
In the blasting method as a preceding process of thermal spraying, abrasive particles such as alundum, densic, and steel are blown against the surface of a base material by using compressed air or motor power to roughen the surface of the base material. For example, in the method disclosed in Japanese Patent Provisional Publication No. 60-44267 (No. 44267/1985), coarse blast particles and fine blast particles are mixed so as to make the most of the advantages of particles of these two types mutually, by which an attempt has been made to provide good adhesion of thermal spray deposit.
Also, in the method disclosed in Japanese Patent Provisional Publication No. 64-58477 (No. 58477/1989), a blast nozzle and a thermal spraying gun are integrated, and the blast nozzle of a vacuum blaster type is used, by which an attempt has been made to omit a process and to simplify the configuration of the blasting apparatus.
Further, in the method disclosed in Japanese Patent Provisional Publication No. 6-136504 (No. 136504/1994), thermal spraying is performed while the area just in front of the portion where a thermal spray deposit is formed is blasted, by which an attempt has been made to remove rebounding particles and minute particles at the time of thermal spraying.
However, the above-mentioned methods each have problems as described below.
In Japanese Patent Provisional Publication No. 60-44267, although a specified particle size distribution can be obtained in the initial state, the abrasive particles, once being blown, are broken, so that the distribution changes undesirably. Therefore, it is difficult to specify the particle size distribution in high volume production. In order to maintain the specified particle size distribution, the apparatuses for particle recovery, fractionation, and supply must be made considerably complicated.
Also, in Japanese Patent Provisional Publication No. 64-58477, the blast nozzle has to come into contact with the base material to take advantage of the vacuum blaster type, so that there is the possibility of the surface of base material being damaged. The blast nozzle must be changed for each cylinder to blast cylinders of various diameters, so that the facility is complicated. Since the blast nozzle is in contact with the base material, the once-roughened surface is rubbed by the blast nozzle, so that the roughening state is deteriorated.
Further, in Japanese Patent Provisional Publication No. 6-136504, since the thermal spray deposit is formed immediately after blasting, a large number of blast particles remain in the thermal spray deposit.
Thus, although the blasting process contributes greatly to the quality of the thermal spray deposit, a satisfactory method of obtaining the rough surface in the cylinder has not been disclosed in any Publications. The following is a description of the problems in blasting the inside surface of cylinder.
[Problems Concerning the Shape of Cylinder]
The cylinder bore of the internal combustion engine normally has a diameter not larger than 80 mm, large one having a diameter of about 100 mm. It has a cylindrical shape with a relatively small diameter, and is formed with many screw holes and the like. Therefore,
(1) the blast particles blown to roughen the inside surface of cylinder rebound and hit the inside surface on the opposite side. If the rebounding particles hit the properly roughened surface, the surface roughness is deteriorated, so that the adhesion strength of deposit is decreased.
(2) Fine aluminum powders scraped off from the inside surface of cylinder and the blast particles are liable to remain on the inside surface of cylinder.
(3) The blast particles easily remain in the screw holes or the like. Once the blast particles get into the screw holes or the like, they cannot be removed easily by cleaning etc. If the blast particles remaining in the screw holes or the like are left unremoved, they bite into the inside surface of cylinder when the engine is assembled, leading to poor assembly.
[Problems Concerning Blasting]
For blasting to obtain rough inside surface of cylinder, the blast particles must be blown ranging from the upper end to the lower end of the inside surface of cylinder. Therefore,
(4) To protect the mating surface with the cylinder head, a masking plate is necessary. If the masking plate is mounted in each cylinder, the manpower increases, and a large number of masking plates must be prepared. Further, if the number of cylinder types increase, different masking plates need to be prepared.
(5) Since blasting is performed to roughen the surface, the masking plates are consumed heavily.
[Problems Concerning the Apparatus]
(6) For blasting, to prevent the blast particles from scattering, the roughening of surface is usually performed in a state in which a workpiece is placed in a cabinet. However, when the cabinet is used, the automatic opening/closing of a door and the movement of the workpiece associated therewith are needed for the loading and unloading of the workpiece. Therefore, the mechanism is complicated, and also the number of moving parts increases. As a result, a trouble caused by biting of blast particles occurs easily. Also, the movement mechanism of blast gun is subjected to restrictions as to the movement of blast gun and the size of mechanism by the size of the cabinet. Further, the apparatus must have a sufficient dust collecting function corresponding to the capacity of cabinet, so that the space for the cabinet itself is increased, and the apparatus becomes larger.
In the case where a blast deposit is formed, the above items (4) to (6) are applicable in the process.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a method for blasting an inside surface of a cylinder in which a steady rough surface is always obtained in the whole region of inside surface of cylinder for an internal combustion engine, a masking plate mounting process is decreased even in the case of high volume production, and the method is simplified to the necessary minimum scale for roughening the inside surface of cylinder or forming a blast deposit.
“A steady rough surface is always obtained” described above means that the whole region of the inside surface of cylinder bore exhibits almost constant surface roughness, and for example, there is no difference in surface roughness of the inside surface of bore between the cylinder head side and the crankcase side.
To achieve the above object, in the method for blasting an inside surface of a cylinder, blast particles are blown in the slant downward direction from a blast gun, by which an inside surface of a cylinder extending in the vertical direction of a workpiece is blasted downward.
Also, a cylinder block is placed upright with a cylinder head mating surface on the upper side, a masking member is mounted on the cylinder head mating surface, and blast particles are blown in the slant downward direction from a blast gun, by which an inside surface of a cylinder is blasted downward.
The masking member may consist of a masking member body and a detachable contact portion on the cylinder head mating surface side of the masking member body.
Also, the method may be such that the cylinder block is placed on a pallet, and a space from the masking member to the pallet is formed into a continuous in-pipe space, by which
Kunioka Seiya
Miyai Kenji
Takahashi Tadashi
Morgan Eileen P.
Reed Smith LLP
Suzuki Motor Corporation
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