JPH0587670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sleeve cast-in cylinder block manufactured by casting an aluminum alloy.

[Conventional technology]

When manufacturing a cylinder block, there are two types: press-fit type cylinder blocks, in which a sleeve is press-fitted into a pre-cast aluminum alloy cylinder block, and cast-in type cylinder blocks, in which molten aluminum alloy is poured around the outer circumference of the sleeve. There are cases where The latter type of sleeve-cast cylinder block has many advantages, such as not requiring the dimensional adjustment and other processing required before press-fitting, which is required for the former type of sleeve-press-fit type cylinder block.

[Problem to be solved by the invention]

However, on the other hand, with sleeve-cast cylinder blocks, when the molten aluminum alloy solidifies, the solidification rate is fast on the outside but slow on the inside, so impurities such as gas dissolved in the molten aluminum alloy are absorbed into the inside part. The disadvantage is that casting defects such as blowholes are likely to occur in the central part of the cylinder block in the longitudinal direction. Furthermore, since this molten aluminum alloy solidifies from the outside toward the inside, there is a problem in that the shrinkage force generated at that time tends to cause compressive deformation in the center of the sleeve.

The present invention is a cylinder block manufactured by casting molten aluminum alloy around a cast iron or steel sleeve, and is a sleeve casting type cylinder block that prevents casting defects such as blowholes and compressive deformation of the sleeve. is intended to provide.

[Means to solve the problem]

In order to achieve the above object, the inventor of the present invention has conducted extensive research and found that it is important to create a combination of shapes of the sleeve and cylinder block that will allow the cooling rate of the cast aluminum alloy that constitutes the cylinder block to be approximately uniform in each part. Based on this knowledge, we have completed the present invention. That is, the present invention provides a sleeve casting type cylinder block formed by casting molten aluminum alloy on the outside of a cylindrical sleeve made of cast iron or steel so as to form a chain chamber in the vicinity of the sleeve. The wall thickness difference between the longitudinal center portion and both ends is made larger than the wall thickness difference caused by the draft angle attached to the casting sleeve made by the upper and lower split molds, while the wall thickness difference between the outer circumferential surface of the sleeve and the outer wall of the cylinder block is The wall thickness up to the chain chamber wall and the wall thickness up to the inner wall of the chain are each made thinner at a portion corresponding to the center portion in the longitudinal direction of the sleeve than at portions corresponding to both end portions.

[Effect]

The structure and operation of the present invention will be explained.

In the present invention, the wall thickness at the center in the longitudinal direction of the sleeve is made thicker than at both ends, while the wall thickness of the cylinder block itself from the outer wall of the sleeve to the outer wall of the cylinder block and the inner wall of the chain corresponds to the center part of the sleeve. The area is made thinner than both ends. As a result, the solidification rate of the molten aluminum alloy can be made substantially uniform throughout both inside and outside. Moreover, since the thick walled part at the center of the sleeve acts as a chiller, it promotes solidification of the inner part, which has a slow solidification rate, and makes the solidification rate uniform throughout the cylinder block. Prevent this from occurring in a concentrated manner. Also,
Since the solidification rate of the molten aluminum alloy has become uniform, the pressure applied to the inside during solidification and contraction is reduced, and since the central part of the sleeve is thick and rigid, it does not deform.

〔Example〕

FIG. 1 shows a tricycle equipped with an engine having a sleeve-cast cylinder block according to the present invention. 1 is the main frame, 2 is the down tube, 3
is the engine. The engine 3 has a sleeve-cast cylinder block 4 in the center, on which a cylinder head 5 is mounted. 6 is the front wheel and 7 is the rear wheel.

FIG. 2 is a longitudinal sectional view showing an enlarged main part of the cylinder block according to the present invention. The cylinder block 4 is formed by enclosing a cast iron or steel sleeve 8 therein and further casting molten aluminum alloy so as to form a chain chamber 10 on the side thereof. A piston 9 is inserted into the sleeve 8 as shown in phantom lines, and a chain chamber 10 is inserted into the sleeve 8.
A chain (not shown) connecting a crankshaft and a camshaft is inserted into the camshaft.

Sleeve 8 cast into cylinder block 4
The wall thickness at the center portion in the longitudinal direction of the portion surrounded by the cylinder block 44 is made larger than at both ends. That is, the sleeve 8 has a parabolic or arcuate curve in its cross-sectional outline including its axis, and has a rotating cylindrical shape that is rotated around the axis. On the other hand, the thickness of the cylinder block 4 itself from the outside of the sleeve 8 to the outer wall of the cylinder block is made thinner at a portion corresponding to the longitudinal center of the sleeve 8 than at both ends. Furthermore, the wall thickness from the outside of the sleeve 8 to the inner wall of the cam chamber 10 is made so that the portion corresponding to the longitudinal center of the sleeve 8 is thinner than both ends.

In addition to the shape shown in FIG. 2, the outer wall of the sleeve 8 may have a barrel shape as shown in FIG. 3A, a tapered shape as shown in FIG. 3B, and a cross-sectional shape as shown in FIG. 3C. Various shapes such as a trapezoid can be adopted.

As described above, in the sleeve cast-in type cylinder block of the present invention, the wall thickness at the longitudinal center of the sleeve 8 is thicker than at both ends, and the cylinder block itself extends from the outside of the sleeve 8 to the outer wall of the cylinder block and from the inside of the chain chamber. The thickness up to the wall is made thinner in the area corresponding to the center of the sleeve, where molten aluminum is difficult to solidify, than at both ends, making the solidification rate almost uniform throughout the cylinder block when molten aluminum alloy is cast. can do. Moreover, since the longitudinal center part of the cast iron or steel sleeve 8 has a large wall thickness, this acts as a cooling metal, further promoting uniformity of the solidification rate, and preventing casting defects such as blowholes from forming on the inside. Prevent it from occurring in concentrated areas.

In addition, the shrinkage force generated when the molten aluminum alloy solidifies is reduced by making the solidification rate uniform, thereby reducing the load on the inside.Furthermore, the sleeve 8 is made thicker at the center in the longitudinal direction to increase rigidity. Therefore, no deformation occurs.

In addition, although the case of the engine for a tricycle was explained in the above-mentioned embodiment, the present invention is also applicable to engines for motorcycles, passenger cars, and the like.

〔Effect of the invention〕

Since the present invention is constructed as described above, the solidification rate when molten aluminum alloy is cast can be made almost uniform throughout the cylinder block, and at this time, the thick part in the center of the sleeve can be cooled. Since gold acts to further equalize the solidification rate, it prevents casting defects such as blowholes from concentrating on the inner part.
In addition, by making the solidification rate uniform, the shrinkage force when the molten aluminum alloy solidifies is reduced, and the thickness of the sleeve at the center in the longitudinal direction is increased, which increases rigidity and prevents deformation. and is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a side view of a tricycle equipped with an engine having a sleeve cast-in type cylinder block according to the present invention, FIG. Figures A, B, and C are longitudinal sectional views showing other embodiments of the sleeve used in the present invention. 3...Engine, 4...Cylinder block, 8
...Sleeve, 10...Chain room.

Claims (1)

[Scope of Claims] 1. A sleeve casting type cylinder block formed by casting molten aluminum alloy on the outside of a cylindrical sleeve made of cast iron or steel so as to form a chain chamber in the vicinity of the sleeve. The difference between the wall thickness at the center in the longitudinal direction and the wall thickness at both ends,
The wall thickness is larger than the difference in wall thickness caused by the draft angle attached to a casting sleeve made by an upper and lower split mold, and the wall thickness from the outer peripheral surface of the sleeve to the outer wall of the cylinder block excluding the cooling fins and to the inner wall of the chain are 1. A sleeve cast-in type cylinder block characterized in that the wall thickness is made thinner in a portion corresponding to the longitudinal center portion of the sleeve than in a portion corresponding to both ends. 2. The sleeve cast-in type cylinder block according to claim 1, wherein a portion of uniform thickness with a constant width is formed in the central portion of the sleeve in the axial direction. 3. The sleeve cast-in type cylinder block according to claim 1, wherein a gentle curved surface is formed in the axial direction of the outer circumference of the central portion of the sleeve. 4. The sleeve cast-in type cylinder block according to claim 1, 2 or 3, wherein the thickness from the inner surface of the sleeve to the outer wall of the cylinder block excluding the cooling fin portion and the inner wall of the chain is approximately the same at every portion.