JP2616057B2 - Manufacturing method of cylinder block - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cylinder block, and more particularly, to a method for manufacturing a cylinder block made of an aluminum alloy in which a cylinder liner made of cast iron is cast by low pressure casting or gravity casting. To a method of manufacturing.

2. Description of the Related Art As a cylinder block for an internal combustion engine, there is known a structure in which a cylinder liner made of cast iron is casted out of an aluminum alloy so that a cylinder bore is formed of cast iron. This cylinder block is generally manufactured by low-pressure casting or gravity casting. In order to secure dimensional accuracy and obtain the cylinder liner's retaining effect (anchor effect due to uneven contact with the mating aluminum alloy) In some cases, a spiral groove extending in the circumferential direction, such as a thread groove, is formed on the outer peripheral surface of the liner in advance, and then the liner is inserted.

Problems to be Solved by the Invention In the above-described manufacturing method, the degree of adhesion between the cast iron cylinder liner and the aluminum alloy, which are dissimilar materials, is an important factor, but if there is a spiral groove, The discharge of air in the product space and the run of hot water are poor, and the improvement of the adhesion of the cylinder liner to the aluminum alloy cannot be expected. As a result, during the operation of the engine, the efficiency of heat transfer from the inside of the cylinder bore to the cooling water in the water jacket deteriorates, and there is a concern that the engine performance may be degraded.

Here, the cause of the above-mentioned poor adhesion is presumed as follows. That is, in a method of manufacturing a cylinder block by low-pressure casting or gravity casting, a cylinder liner is set in a mold in an upright posture, and a sprue portion connected to a lower end of a portion to be a skirt portion of the cylinder block is provided. From the bottom to the top of the product space by a spiral groove perpendicular to the axis of the cylinder liner. The cause is considered to be that the flow of the flowing molten metal (fluidity) is hindered, and at the same time, it is difficult to completely exhaust the air in the product space.

The present invention has been made in view of the above-described problems, and has as its object to improve the flow of molten metal while maintaining the effect of preventing the groove formed on the outer periphery of the cylinder liner. An object of the present invention is to provide a method of manufacturing a cylinder block.

Means for Solving the Problems The present invention relates to a method for manufacturing a cylinder block formed by casting a cylinder liner made of cast iron with an aluminum alloy, and forming a plurality of circumferential grooves around the entire outer peripheral surface of the cylinder liner. Performing a shot peening process on the outer peripheral surface of the grooved cylinder liner; positioning the shot peened cylinder liner in the mold in an upright position; And filling the molten metal of the aluminum alloy upward from a sprue provided continuously at the lower end of the portion to be formed into a cylinder liner, and casting the cylinder liner.

The above shot peening process is performed in order to secure a molten metal passage in the longitudinal direction of the outer periphery of the cylinder liner by depressing a convex portion existing between adjacent grooves into a local portion. The diameter of the steel ball) is equal to or larger than the pitch between the grooves.

That is, when the pitch between the grooves is P and the diameter of the shot material used in the shot peening process is d, the relationship between the pitch P and the diameter d of the shot material is 1.
Set 0P ≦ d ≦ 2.5P.

According to the method described above, by performing the shot peening process on the outer peripheral surface of the grooved cylinder liner, the convex portion existing between the adjacent grooves is locally crushed as described above, and the depression is formed. Is formed.

Then, after setting the cylinder liner in the mold in an upright posture to fill the cylinder liner that has been subjected to shot peening, and filling it with the molten aluminum alloy, the molten metal rises smoothly as a passage with the depression,
The hot water and the air in the product space are discharged well.

As a result, the degree of adhesion between the cylinder liner and the aluminum alloy, which is an important element in a so-called liner insert-type cylinder block, is greatly improved.

Embodiment FIG. 1A is an explanatory view showing an embodiment of the present invention, and shows an example in which a cylinder block is cast by a low-pressure casting method.

As shown in FIG. 1, a cylinder liner 6 made of cast iron and a water are previously provided in a product space 5 of a mold M defined by a lower mold 1 and an upper mold 2 and a mold 3 and 4 movable in a horizontal direction. After positioning the jacket core 7 in the upright posture, the molten metal of aluminum alloy is filled from the sprue portion 10 continuously provided at the lower end of the portion to be the skirt portion 9 of the cylinder block 15 toward the upper product space 5. Then, casting is performed so as to insert the cylinder liner 6. Reference numeral 11 denotes a feeder for guiding the molten metal from a molten metal holding furnace (not shown) to the gate section 10.

Prior to such cast-in-place casting, the cylinder liner 6
2 and 3, a circumferential groove 12 is formed in advance on the entire outer peripheral surface of the cylinder liner 6, and after the groove processing, the outer peripheral surface of the grooved cylinder liner 6 is shot peened. Perform processing.

The groove processing is performed, for example, by turning the cylinder liner 6.
A spiral groove 12 such as a screw groove is formed from one end outer peripheral surface to the other end outer peripheral surface. However, the groove 12 does not necessarily need to be continuous like a thread groove.

Shot peening is performed on the previously machined grooves 12,12.
This is performed for the purpose of locally recessing the convex portion 13 located between the grooves 12, and is performed using a shot material (steel ball) having a diameter equal to or larger than the pitch P between the grooves 12, 12. I do. In this case, if the diameter d of the shot material is too large, the convex portion 13 is too crushed and the effect of the groove processing is significantly reduced. Therefore, the shot peening process is performed under the following conditions.

Shot peening condition ・ Shot material diameter (d): 1.0P ≦ d ≦ 2.5P (However, P
Is the pitch of the grooves 12.) Projection speed: 50 to 70 m / sec. Projection density: 300 to 500 kg / m ² · min. By performing shot peening, the grooves 12 and 12 as shown in FIG. The convex portion 13 between them is locally crushed to form a dent 14. Due to the dent 14, the grooves 12, 12 extending in the circumferential direction of the cylinder liner 6 are mutually connected in the longitudinal direction of the cylinder liner 6. Will be in communication.

When cast-in casting is performed as shown in FIG. 1 (A) using the cylinder liner 6 that has been subjected to such groove processing and shot peening processing, the depression 14 causes the molten metal flowing from the skirt 9 to the upper end of the cylinder bore. Functioning as a passage in the longitudinal direction that promotes the flow of the molten metal, the air in the product part space 5 accompanying the filling of the molten metal is smoothly discharged, and the running of the molten metal is greatly improved. And, the degree of adhesion between the cylinder liner 6 and the aluminum alloy after casting is greatly improved by the air discharge and the smoothness of the molten metal.

The inventor cuts the cylinder block 15 in which the cylinder liner 6 which has been subjected to the shot peening process as described above is cast into a gap 16 (FIG. 5) as shown in FIG. 4 and FIG. The cylinder liner 6 and the aluminum alloy without the occurrence of
The area of the portion where 17 and 17 were completely in contact (the portion indicated by cross-hatching C in FIG. 4) was determined, and the ratio of the above-mentioned contact area to the entire inner peripheral area of the cylinder bore was determined as the degree of adhesion (%). And about this adhesion degree,
As shown in the figure, comparison was made with Comparative Examples 1, 2, and 3.

Comparative Example 1 was obtained by subjecting the cylinder liner 6 to only groove processing, Comparative Example 2 was obtained by performing sanding paper polishing instead of shot peening after groove processing, and Comparative Example 3 was similarly shot after groove processing. Sand shot processing was performed instead of peening processing.

As a result, as shown in FIG. 6, it can be seen that shot peening is most effective in improving the degree of adhesion between the cylinder liner 6 and the aluminum alloy 17.

7 to 10 are enlarged views of the surface state of the cylinder liner 6 of the present invention and Comparative Examples 1, 2, and 3. In Comparative Example 1 of FIG. 7, the grooves 12 and the grooves 12, 12 are shown. Convex part 13 between each other
In the comparative example 2 of FIG. 8 and the comparative example 3 of FIG. 9, the grooves 12 and the projections 13 are uniformly polished. It is understood that the air discharge and the run of the hot water were not improved and did not significantly contribute to the improvement in the degree of adhesion.

On the other hand, in the case of the present invention shown in FIG. 10, the projections 13 between the grooves 12, 12 are locally crushed by the shot peening process to form dents (dents of shot material) 14. Is clearly shown. And this depression
14 functions as a passage in the longitudinal direction of the cylinder liner 6 at the time of filling the molten metal, thereby improving the air discharge and the run of the molten metal, and greatly contributing to the improvement in the degree of adhesion between the cylinder liner 6 and the aluminum alloy 17. Understood.

In addition, there is a large correlation between the diameter of the shot material (steel ball) used in the shot peening process and the degree of adhesion,
According to the result of the experiment performed by the inventor, the pitch P between the grooves
It was found that the use of a shot material having a diameter of 0.6 mm or 1.4 mm as shown in FIG.

Advantageous Effects of the Invention As described above, according to the present invention, by forming a circumferential groove on the entire outer peripheral surface of the cylinder liner and then performing shot peening to cast-in, the shot peening process The convex portion between the grooves is locally crushed to form a dent, and the dent functions as a molten metal passage in the longitudinal direction of the cylinder liner when filling the molten metal. Is greatly improved. As a result, the degree of adhesion between the cylinder liner and the aluminum alloy can be improved while maintaining the retaining effect due to the formation of the groove on the outer periphery of the cylinder liner. Can greatly contribute.

[Brief description of the drawings]

1 (A) is a sectional view of a mold for explaining the method of the present invention, FIG. 1 (B) is an enlarged view of a main part of a cylinder liner after a shot peening process, and FIG. 2 is an overall shape of the cylinder liner. FIG. 3 is an enlarged view of a main part of the cylinder liner before the shot peening process, FIG. 4 is a cross-sectional view of the cylinder block after casting, and FIG. 5 is an enlarged view taken along line VV in FIG. FIG. 6 is a cross-sectional view, and FIG. 6 is a view comparing the present invention and Comparative Examples 1, 2, and 3 with different surface treatment methods for the degree of adhesion between the cylinder liner and the aluminum alloy, and FIGS. 7, 8, and 9; And FIG. 10 is an enlarged view showing the surface state of the cylinder liner subjected to each surface treatment of the present invention and Comparative Examples 1, 2, and 3, and FIG. 11 shows the relationship between the above-mentioned adhesion and the diameter of the shot material. FIG. 5 ... product space, 6 ... cylinder liner, 9 ... skirt, 10 ... gate, 12 ... groove, 13 ... convex, 14 ...
Dent, 15 ... Cylinder block, 17 ... Aluminum alloy, M ... Mold.

Claims (1)

(57) [Claims] 1. A method for manufacturing a cylinder block, comprising: casting a cylinder liner made of cast iron with an aluminum alloy; forming a plurality of circumferential grooves all around the outer peripheral surface of the cylinder liner; Applying a shot peening process to the outer peripheral surface of the cylinder liner subjected to the shot peening; positioning the shot-peened cylinder liner in the mold in an upright posture; Filling the molten metal of the aluminum alloy upward from a sprue portion connected to the lower end and casting the cylinder liner, and setting the pitch between the grooves to P, which is used for shot peening. When the diameter of the shot material is d, the relationship between the pitch P and the diameter d of the shot material is set to 1.0P ≦ d ≦ 2.5P. Manufacturing method of that cylinder block.