JPH0148386B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to internal combustion engines such as diesel engines having three or more cylinders, and relates to the structure of a Siamese cylinder liner used in such engines. Regarding.

(Prior Art) In general, in a cylinder liner having a Siamese structure, as shown in FIG. ) are integrally continuous. According to this structure,
Compared to the case where the individual cylinder liners 1 and 2 are provided independently as shown in Fig. 5, the total length of the cylinder liner section 6 (length in the left-right direction in Figs. 4 and 5) can be shortened, and the overall engine is lightweight and compact. can be achieved.

(Problem to be Solved by the Invention) However, in the cylinder liner portion 6 of the conventional Siamese structure, the thickness of the cylinder liners 1 and 2 is almost constant over the entire circumference, and the rigidity in the longitudinal direction X of the crankshaft is The rigidity of the cylinder block (not shown) in the width direction Y (direction perpendicular to the crankshaft direction X and the combustion chamber center line O) is lower than that of the cylinder block (not shown). Also, the cylinder liner side part 8 (width direction Y across the combustion chamber center line O)
Since the continuous portion 3 is farther away from the cooling water jacket inside the cylinder block and the outer surface of the cylinder block than the circular arc-shaped portion (opposed to In comparison, the temperature of the continuous portion 3 is higher, and differences occur in thermal deformation of each portion.

Therefore, in the operating state, as shown by the solid line in FIG. 7, the amount of deformation differs in each part of the central cylinder liner 2, and the cylinder liner 2 takes on an elliptical shape that is elongated in the width direction Y. Also, as shown by line a in FIG. 8, the deformation ratio E of this ellipse is extremely large compared to other structures. Note that the line b in FIG. 8 shows the deformation characteristics of the independent cylinder liner shown in FIG. 5, and the line c shows the deformation characteristics of the Siamese-structured cylinder liner employed in a two-cylinder engine.

Further, the elliptic deformation ratio E and PV value in FIG. 8 are as follows.

E=(Db-Da)/D D: Liner inner diameter at room temperature (Fig. 7) Da: Minor diameter of the ellipse during deformation Db: Major diameter of the ellipse during deformation PV = (Net average effective pressure) x (Piston speed ) As mentioned above, in the structure shown in FIG. 4, the cylinder liner 2 is largely deformed into an elliptical shape, whereas the piston (not shown) has a circular outer circumferential profile during operation, as in the case of the independent cylinder liner structure. A device that transforms into is used.

Therefore, in the conventional structure, there is a risk that scuffing or seizure may occur on the inner surface of the cylinder liner 2 or the sliding surface of the outer circumference of the piston during operation. Further, as shown in FIG. 8, as the engine load (corresponding to the PV value) increases, the elliptic deformation ratio E increases, so the above-mentioned problem is particularly likely to occur at high loads.

The present invention attempts to solve the above problems.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides for each cylinder liner of an in-line engine having three or more cylinders to In the cylinder liner part of the Siamese structure that is continuous with other cylinder liners, the thickness of the part of the intermediate cylinder liner facing in the direction perpendicular to the crankshaft across the combustion chamber center line is calculated as follows: It is characterized by being approximately 50% to 100% larger than the minimum effective thickness of the part.

(Function) In the above structure, high rigidity is given to the uneven thickness portion (cylinder liner side portion) that faces the direction perpendicular to the crankshaft across the combustion chamber centerline among the various portions of the intermediate cylinder liner. Therefore, each part of the cylinder liner expands almost uniformly, making the entire cylinder liner circular. Therefore, the contact behavior between the inner surface of the cylinder liner and the piston becomes smooth, and scuffing and seizure are prevented from occurring.

(Embodiment) Fig. 1 is a cross-sectional view of a cylinder liner section of an embodiment of the present invention adopted in an in-line three-cylinder engine, and parts corresponding to those in Fig. 4 are given the same reference numerals. There is. In FIG. 1, the cylinder liners 1 at both ends have a uniform thickness over the entire circumference, except for a continuous portion 3 that is integrated with the cylinder liner 2 in the middle. Further, the continuous portion 3 common to the cylinder liners 1 and 2 has a larger thickness than the other portions of the cylinder liner 1.

Of the respective parts of the intermediate cylinder liner 2, both side parts 8, that is, the parts with arcuate cross sections facing in the width direction Y across the combustion chamber center line O, have a larger thickness than the side parts 10 of the cylinder liner 1 at both ends. It has a T. Reference numeral 11 indicates a boundary between the continuous portion 3 and the side portion 8, in other words, a portion adjacent to both ends of each continuous portion 3. The side portion 8 has the largest thickness T at the intermediate portion between the two boundary portions 11, 11, and the thickness gradually decreases as it approaches the boundary portion 11.

FIG. 3 is a schematic cross-sectional view of FIG. 1, and as shown by solid lines in FIG.
It is also possible to make only the upper half (on the cylinder head side) of the upper half (on the cylinder head side) thicker than the outer surface 13, or to make the outer surface 13 smoothly sloped so that the thickness gradually decreases as it goes downward. can.

t in Figure 1 is the minimum effective thickness of the cylinder liner 2 (the minimum value of the thickness calculated backward from the strength against stress)
This is a value that almost matches the thickness of the boundary portion 11.
According to the present invention, when the thickness unevenness rate P of the side portion 8 is calculated using the following formula using the minimum effective thickness t as a reference,
Thickness unevenness rate P is set to approximately 50 to 100%.

P=(T-t)/t×100 (%) According to the above structure, the side portion 8 has higher rigidity than the conventional side portion 8 (FIG. 4) having a uniform thickness. Therefore, each part of the cylinder liner 2 expands almost uniformly, and the entire cylinder liner 2 becomes a perfect circle even after expansion, as shown by the broken line R1 in FIG. 2. Therefore, the contact behavior between the inner surface of the cylinder liner 2 and the piston is smoothed.

In addition, in Fig. 2, the solid line R2 indicates that the thickness unevenness rate P is 0%.
The deformed shape in the case of is shown, and the dashed-dotted line _R3 shows the shape before deformation.

Also, in Figure 8, the thickness unevenness rate P is 100% (line P10) and 50%.
(Line P5) shows the ellipse deformation ratio E when it is 0% (a). As is clear from this figure, even when the thickness unevenness ratio P is 50% (P5), it is possible to obtain an elliptical deformation ratio E that is almost the same as that of the conventional independent structure cylinder liner (line c), and When the ratio P is 100% (P10), the elliptic deformation ratio E can be much smaller than that of a conventional independent cylinder liner.

(Effects of the Invention) As explained above, according to the present invention, since the side portion 8 of the intermediate cylinder liner 2 is given uneven thickness to increase its rigidity, it is possible to deform the entire cylinder liner 2 into a substantially perfect circle. can. Therefore, the contact behavior between the inner surface of the cylinder liner 2 and the piston becomes smooth, and it is possible to prevent scuffing and seizure from occurring.

Further, since the thickness deviation ratio is set to about 100% or less, the side portion 8 is prevented from protruding outward to a large extent, and the size and weight of the entire engine can be kept small.

(Other Embodiments) The present invention can be applied to an internal combustion engine having four or more cylinders, and in that case, the uneven thickness structure described above is adopted at the side portions of the cylinder liner other than at both ends.
The present invention can also be applied to an internal combustion engine in which a sleeve is interposed between the cylinder block and the cylinder liner.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, FIG. 2 is a schematic plan view showing a deformed state of the liner, and FIG.
Fig. 4 is a schematic cross-sectional view of the cylinder liner section of the conventional Siamese structure, Fig. 5 is a schematic cross-sectional view of the cylinder liner section of the conventional independent type, and Fig. 6 is the temperature distribution of the cylinder liner section. 7 is a schematic diagram showing a deformation pattern of a cylinder liner portion of a conventional Siamese structure, and FIG. 8 is a graph showing the relationship between PV value and elliptic deformation ratio. 1, 2...
... Cylinder liner, 3 ... Continuous part, 6 ... Cylinder liner part, 8 ... Side part, O ... Combustion chamber center line,
X: Crankshaft direction, Y: Direction perpendicular to the crankshaft, t: Minimum effective thickness.

Claims (1)

[Claims] 1. In the cylinder liner part of a Siamese structure in which each cylinder liner of an in-line engine with three or more cylinders is continuous with other cylinder liners in the part located in the crankshaft direction with respect to the combustion chamber center line, the middle cylinder The cylinder liner is characterized in that the thickness of the portion of the liner facing perpendicular to the crankshaft across the combustion chamber centerline is approximately 50% to 100% larger than the minimum effective thickness of the other portions of the cylinder liner. Cylinder liner structure of a multi-cylinder internal combustion engine.