JP3122242B2 - Method for producing product having boss and mold used for the production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a product having a boss portion manufactured by a casting method, for example, a cylinder block of a vehicle engine having a boss portion to which an oil filter is screwed. , A mold used for the production thereof.

[0002]

2. Description of the Related Art Generally, a cylinder of a vehicle engine is
It is composed of a cylinder head forming a combustion chamber, a cylinder block in which a piston reciprocates, and a crankcase for incorporating a crank and the like. A cylindrical boss portion for screwing an oil filter for cleaning engine oil is formed on the cylinder block, particularly among the cylinder portions.

The cylinder block is usually manufactured by a casting method, but the boss formed on the cylinder block has a shape protruding outward from the body of the cylinder block. Later, problems such as insufficient strength may occur.

[0004] This problem will be specifically described with reference to the drawings. FIG. 3 is a diagram showing an example of a cylinder block. In FIG. It is a formed boss for screwing an oil filter. FIG. 4 is a view showing the boss portion 2 and the cylinder block molding die 3 (portion for molding the boss portion 2).

The boss 2 comprises an inner cylinder 4 and an outer cylinder 5 formed outside the inner cylinder 4. The space between the inner cylinder part 4 and the outer cylinder part 5 constitutes one flow path 6 of the oil, and the inner surface 7 of the inner cylinder part 4 has a screw for screwing an oil filter after casting. Is formed. The distal end portion 8 of the inner cylindrical portion 4 is formed with an enlarged diameter portion 10 that increases the diameter of the hole 9 in the inner cylindrical portion 4 at the distal end portion 8.

The reason for forming the enlarged diameter portion 10 is that, when a screw is formed in the hole 9 by tapping after casting, if the diameter of the hole 9 at the tip end portion 8 is adjusted to the tap diameter, tapping is performed. In this case, there is an inconvenience that a processing bulge occurs at the tip portion 8, and in order to avoid this, a portion having a diameter slightly larger than the tap diameter is formed.

[0007]

In the casting method, it is an important point to determine the quality of a cast product until the molten metal is poured into a mold and cooled and solidified. In this case, when the product is formed using the mold 3 as shown in FIG. 3 described above, the intersection 13 between the tip surface 11 of the tip portion 8 and the inner surface 12 of the enlarged diameter portion 10 is sharp, so that the molten metal is Causes poor rotation. That is, the tip surface 1 of the tip portion 8
1 and the inner surface 12 of the enlarged diameter portion 10 have a sharp portion, so that the molten metal loses fluidity in this portion 13 and the properties of each part of the product become uneven when cooled and solidified. Could be. Further, when the molten metal is injected, a gas such as air is simultaneously entrained and the mold 2
In the mold 3, the air and the like are caught and solidified while the air or the like is caught in the portion 13 of the tip portion 8. As a result, a defect occurs in the properties of the tip portion 8 of the boss portion 2, and there is a problem that the yield of the product is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a method of manufacturing a product having a boss portion capable of always forming a boss portion satisfactorily and obtaining a product with a high yield, and manufacturing the same. An object of the present invention is to provide a mold used for the above.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a product having a boss portion, the method comprising the steps of: casting a product having a cylindrical boss portion having an inner surface subjected to thread processing; The product is cast by forming the boundary between the end surface of the portion and the inner peripheral surface into a smoothly continuous curved surface from the end surface to the inner peripheral surface, and then casting the product on the inner surface of the boss portion, from the portion formed on the curved surface It is characterized by being subjected to screw processing.

A mold used for manufacturing a product having a boss portion according to claim 2 is a mold for casting a product having a cylindrical boss portion on which an inner surface is subjected to thread processing. The surface forming the boundary between the end surface of the portion and the inner peripheral surface is formed as a smoothly continuous curved surface from the end surface to the inner peripheral surface.

[0011]

In the manufacturing method according to the first aspect, the boundary between the end surface of the boss portion and the inner peripheral surface is formed as a smoothly continuous curved surface from the end surface to the inner peripheral surface, so that the fluidity of the molten metal is ensured. And a good product is obtained. In addition, when tapping is performed from a portion formed on a curved surface, processing swelling is suppressed.

In the mold according to the second aspect, the boundary between the end surface of the boss portion and the inner peripheral surface and the outer peripheral surface is formed by a curved surface that is smoothly continuous from the end surface to the inner peripheral surface and the outer peripheral surface. Accordingly, the fluidity of the molten metal in the mold is promoted, whereby a good cast product can be obtained, and the inner peripheral surface of the boss can be easily threaded.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a boss mold according to the present invention will be described below with reference to the drawings. The embodiment described here is an example in which the present invention is applied to a method for manufacturing a vehicle cylinder block as shown in FIG. 3 and a mold used therefor.

FIG. 1 shows a boss 21 of a cylinder block.
And a mold 22 for molding the boss 21.
The boss portion 21 is provided on the cylinder block 1 shown in FIG.
Formed on the same cylinder block as
Its components are substantially the same as those in FIG. 4 and include an inner tube portion 23 and an outer tube portion 24. The space between the inner cylinder part 23 and the outer cylinder part 24 constitutes one flow path 25 of oil, and a screw for screwing an oil filter after casting is formed on the inner surface 25 of the inner cylinder part 23. It is formed.

On the other hand, a mold 22 for forming the boss 21
Are different from the mold 3 shown in FIG.
The surface forming the tip 26 has the following shape. That is, the surfaces forming the outer surface 27 and the inner surface 28 of the inner cylindrical portion 23 are formed along the vertical plane at the position shown in FIG. Then, a surface 30 and an end surface 2 which are boundaries between the end surface 29 of the inner cylindrical portion 23 and the outer surface 27 are described.
The surface forming the boundary 31 between the inner surface 9 and the inner surface 28 is a smoothly continuous curved surface.

Accordingly, the shape of the distal end portion 26 of the inner cylindrical portion 23 of the boss portion 21 formed by the mold 22 is a curved surface 31 where the shape of the inner surface 28 and the end surface 29 is smoothly continuous.
The shape of the outer surface 27 and the end surface 29 is also a smoothly continuous curved surface 30.

In the casting using the mold 22, when the molten metal is poured into the mold 22, the molten metal turns to a portion where the inner cylindrical portion 23 and the outer cylindrical portion 24 in the mold 22 are formed as shown in FIG. . At this time, the molten metal is uniformly distributed in the mold 22 because the curved surfaces 30, 31 of the distal end portion 26 are formed smoothly in the inner cylindrical portion 23 and the fluidity is improved. Therefore, when the product is taken out by cooling and solidifying after the injection of the molten metal, the properties of the respective portions of the boss portion 21 are uniform, and no defect or the like occurs.

FIG. 2 shows that after the boss 21 is formed in this manner, the boss 21 faces the curved surface 31 formed by the inner surface 28 and the end surface 29 of the tip portion 26 with the tap 32 facing the portion. FIG. 11 is a diagram when a tapping process is performed to form a screw 33 for screwing an oil filter on the inner surface 28. At the time of this tapping, the curved surface 31 is formed as a smooth curved surface as described above.
It is possible to suppress the occurrence of processing swelling in the initial stage of performing the thread cutting from the tip of 2, and to perform tapping on the end surface 29 of the boss portion 21 without projecting the flesh of the boss portion 21 from the end surface 29.

[0019]

As is apparent from the above description, according to the manufacturing method of the first aspect of the present invention, it is possible to secure the fluidity of the molten metal in the boss portion and to suppress the occurrence of defective products. ,
A good product can always be obtained by suppressing processing swelling during tapping. Therefore, a molded product can be manufactured with good yield. Further, according to the mold of the present invention, when the molten metal is poured into the mold, a sharp portion is not formed as a boss portion in the mold, so that the fluidity of the molten metal is secured and the properties of the product are uniform. Can always get good products.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a mold used for manufacturing a product having a boss portion according to the present invention and the product.

FIG. 2 is an enlarged sectional view of a main part when tapping is performed on a product manufactured by using the mold of the present invention.

FIG. 3 is a perspective view of a cylinder block having a boss.

FIG. 4 is an enlarged sectional view of a main part of a conventional mold used for manufacturing a product having a boss portion and the product.

[Explanation of symbols]

 21 Boss part 22 Mold 28 Inner surface 29 End surface 31 Curved surface

Claims (2)

(57) [Claims] When casting a product having a cylindrical boss portion on which an inner surface is subjected to thread processing, a boundary between an end surface of the boss portion and the inner peripheral surface is smoothly formed from the end surface to the inner peripheral surface. A method for producing a product having a boss portion, wherein the product is cast by forming the product into a continuous curved surface, and thereafter, the inner surface of the boss portion is subjected to threading from a portion formed on the curved surface. 2. A mold for casting a product having a cylindrical boss portion on which an inner surface is subjected to thread processing, wherein a surface forming a boundary between an end surface of the boss portion of the product and an inner peripheral surface is formed. A mold used for manufacturing a product having a boss portion, wherein a boundary is formed in a smoothly continuous curved surface from the end surface to the inner peripheral surface.