JPH01247743A - Cylinder block - Google Patents

Abstract

PURPOSE:To prevent local projection of a cylinder liner due to temperature difference by forming a part of thin thickness part in the circumferential direction of a lower deck which supports the lower end of a separated cylinder liner fitted in a cylinder bore. CONSTITUTION:A cylinder block is made from aluminum alloy and manufactured by casting, and a separated cylinder liner 5 made from iron is fitted, for example by press fitting, in the cylinder bore wall 30. In this case, on respective lower end surfaces 13, 14 of a lower deck 6 opposed to a main bearing housing 8 and in the direction meeting at right angles against a camshaft 35, respective grooves 15, 16 are arranged and provided, for example, so that their width T is less than 6mm and their depth H is less than half of the distance between a water jacket 2 and the lower end of lower deck and total sum of their respective central angles against the cylinder is less than 90degree. This thickness part 17, 18 in a part of the circumferential direction are thus formed due to the respective grooves 15, 16.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a lychee-type cylinder block for an internal combustion engine.

<Prior art> As a cylinder block of a conventional internal combustion engine, for example, the third
There is something like the one shown in the figure.

The cylinder block shown in this figure is made of aluminum alloy, manufactured by casting, and has an iron cylinder liner 5 press-fitted into the cylinder wall 30, or the iron cylinder liner 5 is fitted by being cast around the cylinder wall 30. . The cylinder block shown in FIG. 3 is of the dry liner type, and is of the Yammies type in which mutually continuous cylinder walls 30 (not shown) are connected, and a water jacket 2 is formed between the top deck 1 and the lower deck 6. The iron cylinder liner 5 is cooled.

A piston 32 equipped with a compression ring 31 etc. slides on the bore surface 4 of the cylinder block.
The piston skirt portion 33 of the piston 32 receives side pressure from the combustion pressure of the combustion chamber 11, which is separated from the main bearing housing 8 by the bulkhead 7, and also radiates heat from the piston 32 (for example, in Japanese Utility Model Application No. 60-108).
(See Publication No. 48).

<Problems to be Solved by the Invention> However, in such a conventional cylinder block, the lower end 12 of the iron cylinder liner 5 is inserted up to the lower end of the lower deck 6, and the lower end 12 of the iron cylinder liner 5 is inserted all the way around the entire circumference by the lower deck 6. Because of the support, there were the following problems.

That is, due to heat radiation from the 7-ton screw 32, the cylinder wall 30
Although the temperature of the lower end 1 of the iron cylinder liner 5 increases,
The lower deck 6 supporting 2 becomes insufficiently cooled,
The inner surface of the lower deck 6, which is in contact with the iron cylinder liner 5, becomes hotter than other parts. Therefore, when the cylinder block is cast due to the heat generated during engine operation, the solidification shrinkage strain due to the internal stress remaining in the cylinder block is released.
When the engine is cold at, for example, -40° C., the inner surface of the lower deck 6 in contact with the iron cylinder liner 5 expands, but the outer surface does not, so that the lower deck 6 is locally pushed into the inside of the cylinder. Therefore, the bore surface 4 is locally pushed inside the cylinder bore, and when starting a cold engine, the inner circumferential surface of the lower end 12 of the iron cylinder liner 5 corresponding to the pushed bore surface 4 is pressed against the piston 32. There is a problem that the piston skirt portion 33 is damaged and scuffing wear occurs due to poor lubrication.

The present invention has been made in view of these conventional circumstances, and aims to prevent the bore surface, and even the iron cylinder liner, from locally protruding due to temperature differences, which acts on the piston and causes scuffing wear. The purpose is to

<Means for Solving the Problems> For this reason, the present invention provides a cylinder block made of aluminum alloy in which a separate cylinder liner is attached to the cylinder bore portion, in which the wall thickness of the lower deck supporting the lower end of the cylinder liner is increased. , it has a structure in which a portion is formed thinly in the circumferential direction.

In the above configuration, if a part of the wall of the lower deck is made thinner during casting, the heat concentration in that part will be reduced, thereby reducing the solidification shrinkage strain, and the thickness will be made thinner by processing after casting. If formed, due to the release of stress at that time,
Solidification shrinkage strain is released. Therefore, the inner surface of the lower deck expands due to the release of the solidification and shrinkage strain due to heat during engine operation when the engine is cold, and the bore surface formed by the separate cylinder liner due to this expansion locally becomes the cylinder bore. It is suppressed from being pushed inward.

<Example> Embodiments of the present invention will be described below based on the drawings.

In the figures described below, the same elements as in FIG. 3 are given the same reference numerals to simplify the explanation.

FIG. 1 shows a first embodiment.

Like the conventional example shown in FIG. 3, the cylinder block is made of aluminum alloy and manufactured by casting, and a separate iron cylinder liner 5 is press-fitted into the cylinder bore wall 30, or
Alternatively, the iron cylinder liner 5 is mounted so as to be cast around the cylinder wall 30. It is also a dry liner type cylinder, which is a Saiyamize type cylinder in which adjacent cylinder parts (not shown) are connected.

As a configuration according to the present invention, a lower end surface 13 of the lower deck 6 that fits into the main bearing housing 8.
Grooves 15 each having a medium T of 6 ma+ or less in the direction perpendicular to the camshaft 35 of 14, and a depth H of not more than half the distance between the water jacket 2 of the lower deck 6 and the lower end surface 13° 14. .16 are provided so that the sum of the centers α and β of the grooves 15 and 16 with respect to the cylinder is 90° or less. The grooves 15, 16 may be provided by a mold when the cylinder block is cast, or the lower end surfaces 13, 14 of the lower deck 6 may be cast flat during casting, and then provided by machining.

By providing the grooves 15 and 16, the thickness of the lower deck is partially reduced in the circumferential direction.

Next, the effect will be explained.

When the grooves 15 and 16 are formed during casting, heat concentration in the thin wall portions 17 and 18 of the lower deck formed by the grooves 15 and 16 is reduced, and solidification shrinkage distortion due to internal stress remaining in the cylinder block is reduced ( In addition, during casting, the lower end surfaces 13 and 14 of the lower deck 6 are cast flat,
If the grooves 15 and 16 are subsequently provided by machining,
Solidification shrinkage strains are released during machining of grooves 15,16.

Therefore, even if the inner surface of the lower end of the lower deck 6 in contact with the iron cylinder liner 5 becomes high temperature due to heat radiation from the piston 32, the solidification shrinkage distortion due to the heat during engine operation when the engine is cold is small, so that the solidification shrinkage due to the heat during engine operation when the engine is cold or the like is small. Expansion toward the inner surface of the lower deck 6 due to the release of strain, and furthermore, the bore surface 4 formed by the separate iron cinder liner 5 is suppressed from being locally pushed inside the cylinder bore.

Furthermore, during casting, the lower end surfaces 13, 1 of the lower deck 6 are
4 is cast flat and then machined to form the liquid groove 15.1.
6 is more effective because it eliminates thermal strain during cooling associated with casting and allows deformation of the lower end of the bore to escape toward the grooves 15 and 16.

As described above, since the bore surface 4 is prevented from being locally pushed into the cylinder bore, the piston skirt portion 33 of the piston 32 is not damaged by the lower end portion 12 of the iron cylinder liner 5, and scuffing due to poor lubrication is avoided. The occurrence of wear is suppressed.

Further, the thin wall portion 17.18 of the lower deck 6 formed by providing the liquid groove 15.16 allows the lower deck 6 to
The lower end portion 13.14 is not restrained around the entire circumference, and even if the iron cylinder liner 5 becomes hot and expands, the expansion escapes into the liquid groove 15.16 and does not protrude to the inner surface. None.

A second embodiment, shown in FIG.
, 20 and the end of the water jacket 2 with respect to the liquid groove, in order to make the distances A and B similar to the conventional example, the lower deck 6
The length in the water jacket direction is shortened by the length of the liquid grooves 15 and 16.

In this embodiment as well, the inner surface of the lower deck 6 expands due to the release of the solidification shrinkage strain due to heat during engine operation when the engine is cold, and the bore surface 4 formed by the separate iron cylinder liner 5 locally. Regarding the effect of preventing the cylinder from being pushed into the inside of the cylinder bore, the first
It will be played in the same way as the example.

In the second embodiment, when the bore surface 4 protrudes inward, the thicker portion that contacts the piston 32 moves toward the top deck 1, so that the piston 32
If the sliding resistance between the cylinder liner 5 and the piston 32 increases slightly, the lower end 12 of the cylinder liner 5
This will not damage the piston skirt portion 33 of the piston.

Further, since the lower deck 6 can be sufficiently thick, the strength of the lower deck 6 portion can be ensured, and the rigidity is also increased, which is advantageous in terms of the vibration characteristics of the engine.

<Effects of the Invention> As explained above, according to the present invention, it is possible to prevent the bore surface formed by a separate cylinder liner from protruding locally due to temperature differences, which acts on the piston and causes scuffing wear. , the piston can move smoothly, engine noise can be reduced, and the life of the engine can be extended. In addition, since the piston always maintains good contact with the cylinder liner, the airtightness of the combustion chamber is improved, increasing the engine's output and reducing oil consumption, which has great practical effects. .

[Brief explanation of the drawing]

FIG. 1(A) shows the first embodiment of the present invention: Top deck 2 Water jacket 4 Bore surface 5 Cylinder liner 6 Lower deck 15.16 Groove 17.18...Lower deck thin wall part 30...Cylinder wall agent Patent attorney Fujio Sasashima 4...Bore surface 15.16...Groove 17, 18...Lower deck thin wall part 30...Cylinder wall (B) Figure 1

Claims (1)

[Claims] In an aluminum alloy cylinder block with a separate cylinder liner attached to the cylinder bore, the thickness of the lower deck that supports the lower end of the cylinder liner is
A cylinder block characterized by being partially thin in the circumferential direction.