JPH0335863Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cylinder liner for an internal combustion engine.

As is well known in the art, a separately manufactured cylinder liner is supported on the cylinder part formed in the engine crankcase or cylinder block, and the outer periphery of the cylinder liner is used as a jacket for cooling water. The so-called wet liner system is widely used in automobile diesel engines and the like. In this type of engine, a radially extending flange is provided on the outer periphery of the upper end of the cylinder liner, and the flange is supported by the upper end of the cylinder part of the crankcase, and the lower part of the cylinder liner is supported by the opposing crankcase. It is supported only in the radial direction by the inner supporting wall surface.
This is the most common structure, but when multiple cylinder liners are installed in a row for a crankcase with a given size, there are various structural constraints that make it difficult to keep the bore pitch sufficiently small. In other words, a cylinder liner with a larger diameter cannot be disposed within a crankcase having a given size, resulting in a problem of limited output. Therefore, a step or flange is provided at the lower part of the cylinder liner that does not cause interference with various components on the cylinder head such as the head bolt, and this step or flange is placed on a corresponding annular deck provided on the crankcase. At the same time, the upper end of the cylinder liner is brought into contact with the cylinder head via the cylinder head gasket, and the cylinder head is tightened to the crankcase with a head bolt, thereby fixing and supporting the cylinder liner to the crankcase. A type of engine has been proposed that does this.

Now, an example of its typical structure will be explained with reference to FIG. 2. Reference numeral 10 is a cylinder liner, and the upper end thereof has a stepped portion 10a of a slight height for receiving the cylinder head gasket 12, and a crankcase 14.
An upper flange 10b is provided which is supported in the radial direction by a corresponding upper deck 14a, and a lower flange 10c is formed in the lower portion to be mounted on an annular lower deck 14b formed in the crankcase 14. Further, a thin cylindrical extension portion 10d is formed below the lower flange 10c. And the upper flange 10
The wall thickness t of the liner central portion 10e between the upper and lower flanges 10b and 10c is
It is usually smaller than c. Note that 16 is a cylinder head that is fastened to the upper surface of the crankcase 14 by a head bolt (not shown);
20 is a cooling water jacket formed between the cylinder liner 10 and the crankcase 14 surrounding the center portion 10e of the cylinder liner 10; 20 is the upper flange 1;
This is an O-ring for maintaining watertightness that is interposed between Ob and the top deck 14a of the crankcase surrounding the outer periphery of O-ring.

In the above structure, when the cylinder head 16 is tightened with a head bolt through the gasket 12, the cylinder liner 10
The cylinder liner is compressed in the axial direction by the tightening force F acting on the cylinder liner a and the lower flange 10c, but the line of action of the force F and the thickness center line of the cylinder liner central portion 10e Since the upper and lower portions are offset by l ₁ and l ₂ as shown, the cylinder liner 10 has an upper flange 1.
At 0b, in addition to the compressive force F, the bending moment M ₁
＝F×l ₁ acts, and in addition to the compressive force F, bending moment M ₂ =F also acts on the lower flange 10c.
×l ₂ works. For this purpose, the cylinder liner 10 is usually made of a cast iron material with a relatively low Young's modulus.
The inner diameter of the upper and lower flange portions is smaller than the normal inner diameter, and the thinner central portion 10e is larger than the normal inner diameter, resulting in an extremely complicated deformation mode. Such a complicated deformation mode naturally causes the piston ring (pressure ring and oil ring) fitted on the outside of the piston, which slides up and down inside the cylinder liner 10 at high speed, to undergo radial changes. This forces large contractions and expansions, which has the disadvantage of accelerating piston ring wear and increasing oil consumption.
Furthermore, since there is a large cross-sectional change between the upper and lower flanges 10b and 10c and the thin liner central portion 10e, stress concentration is unavoidable, and cast iron liner materials are naturally susceptible to stress concentration, so cracks can occur. There are some problems that can easily cause problems such as

The present invention was devised in view of the above, and consists of an inner cylinder made of cast iron, and an outer cylinder made of steel that is attached to the outer periphery of the inner cylinder and has approximately the same thickness from the upper end to the lower end. The upper end surface of the outer cylinder is in contact with the cylinder head via a cylinder head gasket, and the lower end surface of the outer cylinder is placed on an annular deck provided in the crankcase, and the lower end surface of the outer cylinder is placed on an annular deck provided in the crankcase. The internal combustion engine is characterized in that the liner tightening force generated by tightening is supported only by the deck on the crankcase side and supported by the rigidity of the outer cylinder on the liner side. The main topic is the engine's cylinder liner.

An embodiment of the present invention will be described in detail below with reference to FIG. (Members and portions that are substantially the same as those in the structure of FIG. The central portion 10e between the upper step 10a cooperating with the lower step 10c' supported on the lower deck of the crankcase has an inner cylinder 10e ₁ over its entire length.
It has a double cylinder structure consisting of an outer cylinder 10e2 and an outer cylinder _10e2 . In this embodiment, the inner cylinder 10e ₁ extends from the upper end of the liner to the downward extension 10d and is made of a cast iron material as in the past, while the outer cylinder 10e ₂ is made of a steel material with a relatively high Young's modulus. It is formed to have approximately the same wall thickness from its upper end to its lower end. Cylinder liner 10 having such a configuration
When a tightening force similar to that shown in FIG. 2 is applied to the upper step portion 10a and the lower step portion 10c', bending moments M ₁ and M occur for the same reason as described above (but the absolute value is small as described later). ₂ acts, and therefore a similar inner diameter deformation mode is about to occur, but the above deformation is effectively suppressed by the outer cylinder _10e2 , which has a high Young's modulus, so piston ring wear and oil consumption are significantly reduced. This has the advantage of being reduced.

In the above embodiment, the method of attaching the outer cylinder 10e ₂ to the outside of the inner cylinder 10e ₁ includes a method of making the outer cylinder 10e ₂ in advance and integrally casting it when casting the inner cylinder 10e ₁ ; A method is adopted in which the inner cylinder 10e ₁ is cast in advance, the outer peripheral surface is machined, and then the outer cylinder 10e ₂ is press-fitted. Furthermore, in the above embodiment, the outer cylinder 10e ₂ has the inner cylinder 1 except for the upper step part 10a.
It is molded to have the same wall thickness as 0e ₁ , and the shape shown in Figure 2 is designed to reduce the bending moment arm, especially at the lower deck support part, and to avoid stress concentration. However, it is more advantageous if the thickness of the central portion 10e is completely the same over the entire length.

As mentioned above, the cylinder liner of the internal combustion engine according to the present invention includes an inner cylinder made of cast iron and a steel material that is attached to the outer periphery of the inner cylinder and has approximately the same thickness from the upper end to the lower end. The upper end surface of the outer cylinder is in contact with the cylinder head via the cylinder head gasket, and the lower end surface of the outer cylinder is placed on an annular deck provided on the crankcase. The liner tightening force generated by tightening the cylinder head is supported only by the deck on the crankcase side, and is carried by the rigidity of the outer cylinder on the liner side. In engines where the cylinder liner is supported on the crankcase at its lower part, it avoids complicated inner diameter deformation of the cylinder liner and contributes to reducing piston ring wear and oil consumption. This is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a conceptual diagram showing a conventional cylinder liner and its support structure. 10...Cylinder liner, 10e ₂ ...Outer cylinder, 1
0e ₁ ...Inner cylinder.

Claims (1)

[Scope of utility model registration request] It is formed from an inner cylinder made of cast iron and an outer cylinder made of steel that is attached to the outer periphery of the inner cylinder and has approximately the same wall thickness from the upper end to the lower end, and the upper end surface of the outer cylinder is the cylinder head. The liner is brought into contact with the cylinder head via a gasket, and the lower end surface of the outer cylinder is placed on an annular deck provided in the crankcase, and the liner tightening force generated by tightening the cylinder head is applied to the crankcase. A cylinder liner for an internal combustion engine, characterized in that the case side is supported only by the deck, and the liner side is supported by the rigidity of the outer cylinder.