JPH0333457A - Two-layer liner for cylinder - Google Patents

Abstract

PURPOSE:To decrease the thickness of a liner by forming an inner ring from cast iron haing a Young's modulus E1, and forming the outer ring from high tension steel having a Young's modulus E2, wherein the ratio of Young's modulus of the inner to outer ring shall be F2/E1>=1.5. CONSTITUTION:The ratio of stress in an inner ring to that of outer rind depends upon the ratio of Young's moduli of the inner to outer ring and the ratio of their mean dias. That is, the stress in the inner ring decreases if the Young's modulus E1 of inner ring is small and that of outer ring E2 is large. The stress ratio in the circumferential direction due to gas pressure of the inner to outer ring when the former is made of cast iron while the latter from high tension steel depends finally upon the ratio of Young's moduli E2/E1. Because E1 ranges 8000-12000kg/mm<2> and E2 19000-22000, the wall thickness can be reduced to approx. the half of any conventional by conditioning the ratio of Young's moduli so that E2/E1>=1.5. Thus small wall thickness is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-layer cylinder liner for medium to large-sized diesel engines.

[Conventional technology]

Conventional cylinder liners for diesel engines are made of cast iron in order to maintain wear resistance, and are thick-walled single-piece liners that can withstand combustion gas pressure and are equipped with water cooling holes (bore cool). .

Figures 5 and 6 show the structure of a conventional cylinder liner, where 1' is the liner body, 3 is the bore cool hole, 5' is the pressure receiving part, and 4' is the piston.

(Problem to be solved by the invention) However, in conventional cylinder liners made of cast iron, which has good wear resistance, cast iron has low tensile strength and is subject to high gas pressure, so the cylinder liner has to be thick and the outer diameter has to be increased. If the wall becomes thicker, the thermal stress on the cylinder liner due to gas combustion will increase, making it necessary to provide drilled cooling holes (bore cool holes) for cooling, and the openings will reduce the strength of the cylinder liner. It has the following disadvantages.

Furthermore, in Japanese Patent Application No. 58-72249, a method was proposed in which the outer cylinder was made of steel and the inner cylinder was manufactured by centrifugally casting cast iron inside the outer cylinder, but because the casting of the outer steel material and the cast iron of the inner cylinder was poor,
There was a drawback that the liner was not cooled sufficiently due to poor heat conduction of the cylinder liner.

Therefore, in the conventional integrated bore cool type cast iron cylinder, there is no margin in design, the strength is at its limit, there is no thinning, and it is difficult to increase the output, making it impossible to make the ship more compact by shortening the length of the engine.

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-layer cylinder liner that solves the problems of the conventional apparatus, reduces the thickness of the cylinder liner, increases output, and makes the ship more compact by shortening the length of the engine.

Means for Solving +ta] The two-layer cylinder liner of the present invention uses cast iron with a Young's modulus of El for the inner ring to maintain wear resistance, and uses cast iron with a Young's modulus of E for the outer ring.
2 high tensile strength steel is used, and the Young's modulus ratio of the outer ring and inner ring is E.
2/E1≧1.5.

[For production]

Below, we will prove that thinning is possible by calculating the stress in the inner peripheral direction based on the internal pressure (corresponding to gas pressure in diesel engines) of a two-layer cylinder liner. As will be explained in the examples, this calculation formula (9) is calculated by considering a thin-walled cylinder and arranging the stress ratio in the circumferential direction of the inner and outer rings from the balance between the inner and outer rings. (See Figure 3) However, where El: Young's modulus of the inner ring material E2: Young's modulus of the outer ring material Rml: Average radius of the inner ring Rn+2: Average radius of the outer ring As shown above, the stress ratio of the inner and outer rings is the Young's modulus of the inner and outer rings. Rate ratio E I / E ! Even if cast iron with good wear resistance is used for the inner ring, the Young's modulus of cast iron
1 is small, so if high-tensile steel with a large Young's modulus E2 is used for the outer ring, the stress in the cast iron used for the inner ring can be reduced, making it possible to reduce the thickness of the cylinder liner and improve output.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Figure 1 is a cross-sectional view of a two-layer cylinder liner, where l is FC.
25 shows an inner ring made of cast iron, 2 shows an outer ring made of 5 CPH steel, FIG. 2 is a longitudinal sectional view of FIG. 1, 4 shows the bottom dead center position of the piston, and 5 shows the pressure receiving part. In the figure, inner ring 1 and outer ring 2 are old P (Hot l5ostatic Press i).
Since they are integrally bonded using the NG method, they do not separate even after long-term use and have good thermal conductivity.

Next, the reason why a two-layer cylinder liner reduces the stress in the inner ring and allows the cylinder liner to be made thinner will be explained using the formula for a thin cylinder.

When a two-layer cylinder liner whose Young's modulus is different from that of the inner ring El and the outer ring E2 is subjected to an internal pressure P, the inner ring 1 and the outer ring 2 are each subjected to the same internal pressure and external pressure at the fitting portion q. At this time, the amount of deformation u in the radial direction of the inner ring 1 and outer ring 2
l+u! are as follows:

...(1) Since the inner ring and outer ring are fitted without any gap, the amount of displacement in the radial direction should be equal...(2) Therefore, the external pressure q due to the outer ring is the following value.

R2m+ ...(3) Also, the stress in the circumferential direction of the cylinder is σ.

Therefore, by substituting equations (3) to (8) into equation (7), the stress ratio of the two-layer cylinder liner is determined by the ratio of Young's modulus and the average radius. It can be seen that it is determined by the ratio. That is, when the Young's modulus E1 of the inner ring is small and the Young's modulus E2 of the outer ring is large, the stress σ□ of the inner ring decreases.

In a two-layer cylinder liner, when the inner ring is made of ordinary cast iron and the outer ring is made of high-strength steel, the stress ratio in the circumferential direction due to gas pressure in the inner and outer rings is finally determined by the ratio of the Young's modulus of the inner and outer rings using equation (9). It can be seen that it is determined by

The Young's modulus of the entire inner ring is E, ~10,000kg/Kaku2,
Young's modulus of the outer ring is Ez ~20,000kg/mm
2, the inner ring stress σ1. If the diameter of the liner is sufficiently large, the influence of the radius ratio will be reduced, the stress in the inner ring is σ, and I is the stress in the outer ring.

It is thought that it will be close to about half of that. -For boat fishing, the Young's modulus of the cast iron inner ring is El = 8,000 -12,000
kg/mm", Young's modulus of the outer ring is E2 = 19,000 ~
22.000kg/+m++2.

If we assume that the circumferential stress of the entire inner ring is equal to the circumferential stress of a conventional single-piece liner, and refer to the relational expression 〇〇) between the circumferential stress of the inner and outer rings, the following relational expression % formula %) can be obtained. Therefore, the total thickness of the two-layer cylinder liner is t.

Since the diameter of the liner is large, the outer and inner ring radius ratio of the liner is Rmz/
If Ra+, #l, then Lz=X45tζ0.5t... 06) Therefore, in the two-layer cylinder liner of the present invention, the liner thickness can be half that of the conventional integrated liner, and 11
Due to 1P processing, the inner and outer rings are completely in contact,
Good cooling performance can be maintained without separation from the interface even after a long period of time.

〔Effect of the invention〕

The two-layer cylinder liner of the present invention has an inner ring made of cast iron fitted into the inner periphery of an outer ring made of high-strength steel, and the Young's modulus ratio of the outer and inner rings is set to E2/E1≧1.5, so the thickness of the liner can be significantly reduced. This makes it possible to reduce the thickness of the ship, making it possible to make the ship more compact by shortening the length of the chief engineer.

[Brief explanation of drawings]

Figures 1 to 4 relate to embodiments of the present invention. Figure 1 is a cross-sectional view of a two-layer cylinder liner, Figure 2 is a longitudinal cross-sectional view of the same, and Figure 3 is a stress stress in the circumferential direction of the inner and outer rings. Distribution diagram, Figure 4 is an explanatory diagram related to strength calculation when internal pressure p acts on a two-layer cylinder liner, Figures 5 and 6 are conventional examples, Figure 5 is a diagram corresponding to Figure 1, and Figure 6 is an explanatory diagram related to strength calculation when internal pressure p acts on a two-layer cylinder liner. The figure corresponds to Figure 2. ■...Inner ring, 2...Outer ring, 4...Piston, E,
...Young's modulus of the inner ring, E2...Young's modulus of the outer ring. Outer ring Diagram Diagram Diagram Diagram Double layer cylinder Diagram 4 Diagram 5 Diagram 6

Claims (1)

[Claims] In a two-layer cylinder liner in which an inner ring is fitted to the inner circumference of an outer ring, when the outer ring is made of iron-based material with a Young's modulus of E_2 and the inner ring is made of cast iron with a Young's modulus of E_1, the ratio of the Young's modulus of the outer ring and the inner ring is A two-layer cylinder liner characterized in that E_2/E_1≧1.5.