JPS60243349A - Cylinder liner - Google Patents

Abstract

PURPOSE:To raise the overall strength of a cylinder liner and to facilitate manufacture of the same, by decreasing the stress acted to the layer of cast iron by fitting a sleeve-shaped, reinforcing steel member on the inside of a flange portion of a cylinder liner made of a cast iron in the manner that the reinforcing steel member is positioned coaxially with the cylinder liner. CONSTITUTION:A sleeve-shaped, reinforcing steel member 3 is fitted on the inside of a flange portion 2 of a cylinder liner 1 made of cast iron in the manner that it is positioned coaxially with the cylinder liner 1. The thickness of the reinforcing steel member 3 is made equal, for instance, in the axial direction of the cylinder liner 1. Such a cylinder liner 1 having a three-layer structure can be manufactured by internal chill casting the steel member 3, so that manufacture of the cylinder liner can be made easy and economical. Further, since the explosion stress and the thermal stress acted to the inner and outer layers of cast iron are lowered, the overall strength of the cylinder liner 1 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cylinder liner, and particularly to a cylinder liner whose flange portion is reinforced with a multilayer structure.

[Background of the Invention] Cylinder liners are usually made of cast iron (for example, flake graphite cast iron) with excellent sliding properties because their inner peripheral surfaces slide on piston rings.

This cylinder liner is subject to large thermal stress and mechanical stress because the inner circumferential surface receives the heat and pressure of the combustion gas, and the outer circumferential surface is cooled to keep the sliding surface below a predetermined temperature (for example, about 200 degrees Celsius). It is subjected to fluctuating stress (explosion stress). In recent years, efforts have been made to increase combustion pressure and combustion temperature in order to increase engine output, and research is being conducted on cylinder liners that can withstand even greater stress. A two-layer liner has been developed in which the inner circumferential side of the liner is made of flake graphite cast iron and the outer circumferential side is made of 7-layer cast iron or steel. However, in the case of a two-layer structure, the thermal stress and fluctuating stress on the outer circumferential side become large, and the thickness of the outer layer material must be considerably increased. In addition, such thick multi-layer liners can generally be manufactured only by centrifugal casting, resulting in a large loss of equipment and high equipment costs.

[Object of the Invention] An object of the present invention is to solve the problems of the prior art described above, and to provide a cylinder liner in which the stress in the cast iron layer in a multi-layer cylinder liner is reduced, and which is easy to manufacture.

[Structure of the Invention] In order to achieve this object, the cylinder liner of the present invention has a three-layer structure by providing a reinforcing toning member inside the flange part. The gist of the present invention is a cylinder liner 1 characterized in that a cylindrical steel reinforcing member is provided inside the flange portion coaxially with the cylinder liner.

[Embodiments of the invention] The present invention will be described in detail below with reference to the drawings.

1 and 2 are cross-sections of the flange portion of a cylinder liner showing an embodiment of the present invention, in which a cylindrical steel reinforcing member 3.4 is installed inside the flange portion 2 of the cylinder liner 1. It is provided coaxially with 1. .

In the embodiment shown in FIG. 1, the thickness of the steel reinforcing member 3 is uniform in the axial direction of the cylinder liner 1, and the structure is simple and manufacturing is extremely easy.

Furthermore, in the embodiment shown in FIG. 2, the wall thickness of the steel reinforcing member 4 is small where the flange portion 2 is thick, and conversely, the wall thickness of the steel reinforcing member 4 is small where the flange portion 2 is thin. It's getting bigger. This is because the greater the wall thickness of the flange portion 2, the smaller the stress level of the flange portion 2.
This is because the steel reinforcing member only needs to have a small wall thickness.

Further, as the distance from the top dead center increases, the pressure in the cylinder decreases due to the lowering of the piston, so the wall thickness of the steel reinforcing member can be reduced accordingly.

Such a three-layer cylinder liner can be manufactured by casting the steel reinforcing member 3.4, and does not require costly centrifugal casting equipment, making it easy to manufacture and requiring low equipment costs.

FIG. 3 is a schematic diagram illustrating the stress distribution of the cylinder liner of the present invention, in which the horizontal axis represents the thickness direction of the cylinder liner, and the vertical axis represents stress.

In the figure, the broken line indicates the stress of the conventional example without steel reinforcing members,
The solid line shows the stress of the present invention.

In conventional cylinder liners, the explosion stress gradually decreases away from the combustion chamber surface. Furthermore, the thermal stress increases linearly as it moves away from the combustion chamber surface. The sum of internal stresses (tensile stress) on the surface of the cooling chamber was considerably large.

In contrast, in the cylinder liner of the present invention, the explosion stress and thermal stress in the cast iron layers on the inner and outer circumferential sides are reduced, and the sum of internal stresses on the cooling chamber surface is also reduced, which increases the strength of the cylinder liner. It means that it was done.

In the cylinder liner of the present invention, the thermal stress level of the intermediate steel layer increases, but since this intermediate layer is originally near the neutral plane and has a low stress level, even if there is a slight increase in stress, the absolute value will not change. Moreover, the fluctuating stress level of this intermediate layer also increases, but since this intermediate layer is made of steel and has high strength, it can sufficiently cope with this level of stress.

In the present invention, flake graphite cast iron or C graphite cast iron is used as the cast iron constituting the wall thickness and outer layer, and cast steel, forged steel, etc. can be considered as the steel used for the steel reinforcement member, but spheroidal graphite cast iron is used. It is also possible to adopt

Further, the wall thickness of the steel reinforcing member is usually about 20 to 80% of the wall thickness of the flange portion, but is not limited to this. The steel reinforcing member may be provided over the entire area of the flange portion in the axial direction, or may be provided so as to cover only the portion near the top dead center.

Furthermore, minimizing the weight of the parts reduces the cost of the parts.
This is important for minimizing the cooling effect during casting. For this purpose, the inner and outer surfaces of the steel reinforcing member may have a wavy shape or the like. At this time, when the curvature of the wavy member is small, the stress concentration coefficient becomes large, which is disadvantageous in terms of strength, so it is preferable to pay attention to this in design.

[Effects of the Invention] As detailed above, the cylinder liner of the present invention uses steel for the intermediate layer and cast iron for the inner and outer layers.The stress in the cast iron of the inner and outer layers is reduced, and the entire cylinder liner It has high strength. Moreover, it can be manufactured by a method other than centrifugal casting, and is easy to manufacture.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing one embodiment of a cylinder litchi according to the present invention, and FIG. 3 is a graph showing stress distribution in the cylinder litchi. l...Fist cylinder litchi, 21I-Φ flange part, 3.4...Steel reinforcement member. Agent Patent Attorney Takeshi Shigeno Figure 1 Figure 2

Claims (2)

[Claims] (1) In a cast iron cylinder liner having a flange, a cylindrical steel reinforcing member is placed inside the flange.
A cylinder liner characterized by being provided coaxially with the cylinder liner. (2) The wall thickness distribution of the flange portion and the steel reinforcing member in the axial direction is such that as the wall thickness of the flange portion increases, the wall thickness of the steel reinforcing member becomes smaller.
Cylinder liner described in section.