JPH0128288Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a cylinder block for a multi-cylinder engine.

Conventionally, the cylinder block of a multi-cylinder engine has been equipped with a water jacket between the cylinder part in which the piston moves reciprocally and the outer wall of the block, and the rigidity of the upper wall part connecting the cylinder part and the outer wall of the block has been increased. It is known that each cylinder is approximately uniform (for example, Lucie Elegato Structure and Maintenance, published October 1978, p. 64).

By the way, if the cylinder head is fixed to the upper part of the cylinder block of the conventional multi-cylinder engine with a tightening bolt via a gasket, the following problem may occur. That is, as shown in FIG. 1, a bending moment M is created in the cylinder block 1 due to the tension of the tightening bolts that tends to bend both ends of the upper wall upward, and the surface pressure of the gasket, which is considered to be a substantially uniformly distributed load. , M, the cylinder block 1 is deformed as shown in the imaginary line (exaggeratedly shown). Such deformation of the upper wall portion of the cylinder block 1, that is, the top deck, is determined by the combination of the bending action of the top deck directed upward by the head bolt and the bending action of the gasket directed downward. and,
In a structure where the number of head bolts is reduced as much as possible, the bending action of these head bolts is not balanced by the bending action due to the gasket surface pressure, which is considered to be an approximately evenly distributed load.
As a result, a deformation occurs in which both ends lift up. And the bending moment M, M
As a result, as shown by the imaginary line in FIG. 2, the deformation of the cylinder bores 4 and 5 of the cylinders 2 and 3 located at the ends becomes larger than the deformation of the cylinder bores 8 and 9 of the cylinders 6 and 7 located at the center, and The cylinder bores 4 and 5 of the cylinders 2 and 3 are ellipsoids with their long axes extending in a direction perpendicular to the longitudinal direction of the cylinder block 1, and their major axes are significantly longer than their minor axes. For this reason, the conventional cylinder block 1 has problems in that uneven wear and gas leakage occur in the piston rings, pistons, cylinder liners, etc. in the end cylinders.

In order to solve the above problem, this device has a cylinder part in which a piston reciprocates, an outer wall of the block, and an upper wall part and a lower wall part that connect the cylinder part and the outer wall of the block at the upper and lower parts. A pair of cylinders are arranged symmetrically across a center line connecting the centers of each cylinder bore, on the outer end in the cylinder row direction of the cylinder bore located at the end, and on the above-mentioned upper wall section only between the cylinder bores. In a cylinder block of a multi-cylinder engine in which a head bolt threading part is formed and a cylinder head is fixed to an upper wall part by a cylinder head bolt, a cross section passing through the center of the cylinder bore in a direction perpendicular to the center line, The cross-sectional area of the upper wall of the outer circumference of the cylinder bore located at the end is made larger than the cross-sectional area of the upper wall of the outer circumference of the cylinder bore located at the center, and the cross-sectional area of the upper wall of the outer circumference of the cylinder bore located at the end is The upper wall is formed approximately symmetrically within the range of the cylinder bore diameter in the cylinder row direction with respect to the cross section passing through the center of the cylinder bore, thereby effectively preventing deformation of the upper wall of the cylinder block. The object of the present invention is to provide a new engine cylinder block that can prevent uneven wear and gas leakage of piston rings, pistons, and cylinder liners.

This invention will be explained in detail below with reference to illustrated embodiments.

In Figures 3, 4, and 5, 11 is a cylinder block of a 4-cylinder engine, 12, 13, 14, 15
is the cylinder part of each cylinder, 16, 17, 18, 19
are formed inside the cylinder parts 12, 13, 14, 15 of each cylinder, and each cylinder bore in which a piston (not shown) reciprocates; 21 is the outer wall of the block; 22 is the cylinder part 12, 13, 14, 15 and the outer wall 21 of the block. A water jacket 25 is formed between the cylinder parts 12, 13, 14, 1.
5 and the outer wall 21 of the block, 26 is a bolt hole as a threaded portion for a cylinder head bolt, and 27 is a cooling water passage. The bolt holes 26 are located at the outer ends in the cylinder row direction of the cylinder bores 16 and 19 located at the ends, and at the upper wall portion 25 only between the cylinder bores.
They are arranged symmetrically across the center line connecting the centers of each cylinder bore.

The thickness of the upper wall portion 25 in the vertical direction is the third,
As shown in Figures 4 and 5, the cylinders 2 and 3 at both ends are different from the cylinders 6 and 7 at the center. That is,
The wall thickness X of the upper wall portions 32, 35 of the cylinders 2, 3 at both ends is made thicker than the wall thickness Y of the upper wall portions 33, 34 of the cylinders 6, 7 on the center side, that is, the cylinder bore located at the end. The cross-sectional area of the upper wall of the outer periphery is made larger than the cross-sectional area of the upper wall of the outer periphery of the cylinder bore located at the center, so that the rigidity of the upper wall parts 32, 35 of the cylinders 2, 3 at both ends is increased from that of the cylinder 6 on the center side. , 7.

Now, although not shown, a cylinder head is fixed to the cylinder block 11 having the above configuration by a tightening bolt as a cylinder head bolt via a gasket, and the tension of the tightening bolt and the surface pressure of the gasket cause the first It is assumed that a bending moment similar to the bending moments M and M shown in FIG. 2 acts on the cylinder block 11 so as to bend it in the longitudinal direction.

At this time, the bending moment acting on the cylinder block 11 is determined by the combination of the force exerted by the tightening bolts to direct both ends of the upper wall portion upward and the force exerted by the gasket to direct both ends downward. In a structure like this engine, in which the number of head bolts is reduced as much as possible, the bending action due to the tension of the tightening bolts and the bending action due to the gasket surface pressure, which is considered to be an approximately evenly distributed load, are not balanced, and as a result, both ends of the upper wall are A lifting deformation is about to occur, and the cylinder bores 16 and 19 of the cylinders 2 and 3 at both ends are deformed more than the cylinder bores 17 and 18 of the cylinders 6 and 7 at the center, so that the long axis becomes perpendicular to the longitudinal direction of the cylinder block 11. Try to become an ellipse. however,
The thickness X of the upper wall portions 32, 35 of the cylinders 2, 3 at both ends is the thickness Y of the upper wall portions 33, 34 of the cylinders 6, 7 on the center side.
Since the upper wall portions 32 and 35 of the cylinders 2 and 3 at both ends have high rigidity, deformation of the cylinder bores 16 and 17 in the cylinders 2 and 3 at both ends is suppressed. In other words, the upper wall portions 32 and 35 of only the cylinders 2 and 3 at both ends where the deformation is most likely to occur
The wall thickness is increased, and the cylinder row is perpendicular to the cylinder row.
Moreover, since the rigidity is increased substantially symmetrically within the diameter of the cylinder bore with respect to a line passing through the center of the cylinder bore, deformation of the cylinder bores 16 and 19 is effectively suppressed. Therefore, uneven wear of the piston rings and the like is prevented, and gas leakage from between the cylinder liner and the piston is prevented.

In the modification shown in FIGS. 6 and 7, the cylinders 2 and 3 at both ends are
The upper wall portions 32 and 35 are made to protrude beyond the upper wall portions 33 and 34 of the cylinders 6 and 7 on the center side in a direction perpendicular to the center line of the cylinder bores 16 and 19, and the upper wall of the outer periphery of the cylinder bore located at the end The cross-sectional area of the parts 32 and 35 is the upper wall part 3 of the outer periphery of the cylinder bore located in the center.
The cross-sectional area of cylinders 3 and 34 is increased to increase the rigidity of the upper walls 32 and 35 of the cylinders 2 and 3 at both ends, thereby effectively suppressing deformation of the cylinder block and reducing the deformation of the cylinder bores 16 and 19. It is designed to effectively suppress the

Note that the cylinder head bolt may be a built-in stud bolt.

As is clear from the above explanation, according to this invention, the rigidity of the upper wall parts of the cylinders at both ends is made higher than the rigidity of the upper wall part of the central cylinder, and this highly rigid part is connected to the cylinder row. Since it is orthogonal and symmetrical within the diameter of the cylinder bore with respect to the line passing through the center of the cylinder bore, deformation of the cylinder block can be effectively prevented, and therefore piston rings, cylinder liners, etc. It can prevent uneven wear and gas leakage.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional engine cylinder block, FIG. 2 is a plan view of the cylinder block, FIG. 3 is a plan view of an embodiment of this invention, and FIG.
The figure is a sectional view taken along the line A-A in Fig. 3, Fig. 5 is a sectional view taken along the line B-B in Fig. 3, Fig. 6 is a plan view of a modified example, and Fig. 7 is a sectional view taken along the line BB in Fig.
The figure is a sectional view taken along the line A--A in FIG. 6. 12, 13, 14, 15...Cylinder part, 21
. . . Block outer wall, 22 . . . Water jacket, 25, 32, 33, 34, 35 . . . Upper wall portion.

Claims (1)

[Claims for Utility Model Registration] A cylinder part in which a piston moves back and forth;
The block has an outer wall, an upper wall part and a lower wall part that connect the cylinder part and the block outer wall at the upper and lower parts, and a water jacket is formed between these parts, while the outer wall of the cylinder bore located at the end in the direction of the cylinder row. A pair of cylinder head bolt threading parts are formed symmetrically across the center line connecting the centers of each cylinder bore on the above upper wall part only between the ends and the cylinder bores, and the cylinder head is fixed to the upper wall part by the cylinder head bolts. In the cylinder block of a multi-cylinder engine, the cross section passing through the center of the cylinder bore in a direction perpendicular to the center line, the cross-sectional area of the upper wall of the outer circumference of the cylinder bore located at the end is defined as the outer circumference of the cylinder bore located at the center. larger than the cross-sectional area of the upper wall portion, and within the range of the cylinder bore diameter in the cylinder row direction with respect to a cross section passing through the center of the cylinder bore in a direction perpendicular to the center line of the cylinder bore located at the end, An engine cylinder block characterized in that the upper wall portion is formed substantially symmetrically.