KR102239397B1 - Wet cylinder liner having hard chromium plating - Google Patents

Abstract

The present application relates to a wet cylinder liner having a plating layer formed thereon. More particularly, the present application relates to a wet cylinder liner in which the thickness of a plating layer is different for each formed area. According to the present application, the wet cylinder liner comprises: a cylinder liner including a crankcase contact part, a body part, and an O-ring mounting groove part for sealing; a first hard chrome plating layer formed on an outer surface of the crankcase contact part; a second hard chrome plating layer formed on an outer surface of the body part; and a third hard chrome plating layer formed on an outer surface of the O-ring mounting groove part.

Description

Wet cylinder liner including hard chromium plating layers with different plating thickness depending on the area {WET CYLINDER LINER HAVING HARD CHROMIUM PLATING}

The present application relates to a wet cylinder liner having a plating layer formed thereon, and relates to a wet cylinder liner that is different for each portion in which the thickness of the plating layer is formed.

The cylinder liner is a component that is charged into the cylinder, and is divided into a dry cylinder liner that does not directly contact the coolant, and a wet cylinder liner whose outer periphery forms a water jacket with the flow path groove of the cylinder block to directly contact the coolant.

On the other hand, the wet cylinder liner is in direct frictional contact with the piston on the inner side and at the same time contact with the high temperature/high pressure combustion gas and the coolant on the outer side. Must be equipped at the same time.

In addition, the conventional cast iron cylinder liner, although having a certain degree of corrosion resistance, is a cast article manufactured by casting, and microscopic shrinkage defects, that is, pinholes, air bubbles, and segregation of chemical components, are generated inside. , There is a problem that the degree of progression of stress corrosion cracking by direct contact with the cooling water proceeds faster than that of general steel.

In addition, since the conventional cast iron cylinder liner does not have sufficient corrosion resistance, the outer wall of the cylinder liner is damaged by a shock wave caused by the collapse of bubbles generated between the cylinder liner and the coolant during the combustion process of the engine and high-speed water injection. It causes minute plastic deformation, and thus, there is a problem of causing cavitation corrosion in which the oxide film of the metal is destroyed.

Efforts are being made to solve this problem. As one of them, techniques for forming a plating layer have been proposed. However, it was difficult to solve the above problems by simply adding a plating layer, and it is the time when a study on a method of forming a specific plating layer is required.

Korean Patent No. 10-1171022 (published on August 08, 2012)

According to an embodiment of the present application, it is intended to provide a design regarding the location of chromium plating and the thickness of the plating layer of a cylinder liner for a self-propelled gun diesel engine.

One aspect of the present application relates to a wet cylinder liner.

As an example, a cylinder liner including a crankcase contact portion, a body portion, and an O-ring mounting groove for sealing; A first hard chromium plating layer formed on the outer surface of the crankcase contact portion; A second hard chromium plating layer formed on the outer surface of the body portion; And a third hard chromium plating layer formed on the outer surface of the O-ring mounting groove, wherein the thickness of the first hard chromium plating layer is 100 µm to 150 µm, the thickness of the second hard chromium plating layer is 200 µm to 250 µm, and the third The thickness of the hard chromium plating layer is 100 µm to 150 µm.

As an example, the portion where the second hard chromium plating layer is formed is limited to a portion in contact with the cooling water supplied to the wet cylinder liner.

As an example, at the boundary between the first hard chromium plating layer and the second hard chromium plating layer, a gradient is formed so that the thickness of the plating layer decreases from the second hard chromium plating layer toward the first hard chromium plating layer.

As an example, at the boundary between the third hard chromium plating layer and the second hard chromium plating layer, a gradient is formed so that the thickness of the plating layer decreases from the second hard chromium plating layer toward the third hard chromium plating layer.

As an example, the surface hardness of the first hard chromium plating layer is 700 to 1000 Hv, the surface hardness of the second hard chromium plating layer is 700 to 1000 Hv, and the surface hardness of the third hard chromium plating layer is 700 to 1000 Hv.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent wear resistance is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent corrosion resistance is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent friction characteristics is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent lubricity is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent heat resistance is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner in which a plating layer having excellent hardness is formed.

According to the exemplary embodiment of the present application, it is possible to provide a wet cylinder liner capable of semi-permanent use by having resistance to cavitation erosion by cooling water.

According to an embodiment of the present application, it is possible to provide a wet cylinder liner applicable to a self-propelled gun diesel engine.

1 is a schematic diagram showing the shape of a cylinder liner.
2 is a schematic view showing a plating layer formed on the outer surface of the cylinder liner.
3 is an image before and after forming the chromium plating layer on the outer surface of the cylinder liner.
4 is an image taken of a cross-section of a cylinder liner having a chromium plating layer formed thereon in order to confirm the microstructure of the chromium plating layer formed on the outer surface of the cylinder liner.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "include" or "have" are intended to designate that features, elements, etc. described in the specification exist, but one or more other features or elements may not exist or be added. It doesn't mean none.

Unless otherwise defined, all terms used herein including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in the present application. Does not.

Hereinafter, with reference to the accompanying drawings, a wet cylinder liner including a hard chromium plating layer having a different plating thickness according to a portion of the present application will be described in detail. However, the accompanying drawings are exemplary, and the range of a wet cylinder liner including a hard chromium plating layer in which the plating thickness of the present application differs depending on the region is not limited by the accompanying drawings.

1 is a schematic diagram showing the shape of a cylinder liner.

As shown in Fig. 1, the cylinder liner has a hollow cylindrical shape and is inserted into the crankcase of the engine, and is a core component constituting the combustion chamber together with the upper cylinder head and the internal piston. There is cooling water in the space sealed by the flange at the top of the cylinder liner and the O-ring at the bottom, and it acts to cool the internal combustion heat from the outside of the cylinder liner.

In engines, in order to cool the high-temperature combustion heat generated from the cylinder, a wet cooling type in which the coolant is directly contacted outside the cylinder liner can be applied. When a cooling action occurs on the outer surface of the cylinder liner, the piston strikes the cylinder liner by the side pressure of the connecting rod in the process of converting the vertical linear motion of the piston into the rotational motion of the crankshaft during the explosion stroke on the inner surface of the cylinder liner.

At this time, bubbles are inevitably generated on the outer surface of the cylinder liner in contact with the coolant, and the bubbles collapse on the surface of the cylinder liner. The process of generation, growth, and collapse of such bubbles is called coolant cavitation, and the surface of the cast iron cylinder liner is eroded by cavitation as the engine operating time is accumulated.

If the erosion process of the cylinder liner continues, perforation occurs, and a trace amount of coolant passes through the cylinder liner wall and flows into the combustion chamber.If the erosion condition of the cavitation of the cylinder liner is maintained for a long period of time, the engine uses engine oil mixed with coolant. As a result, the oil pressure decreases, causing damage to the drive system.

According to an exemplary embodiment of the present application, it is intended to provide a hard chromium plating layer having a partially or partially different thickness on the outer surface of the cylinder liner so as to have resistance to cavitation erosion generated by cooling water on the outside of the cylinder liner.

2 is a schematic diagram showing a plating layer formed on the outer surface of the cylinder liner, and FIG. 3 shows images before and after the chromium plating layer is formed on the outer surface of the cylinder liner.

As shown in Figure 2, one aspect of the present application includes a wet cylinder liner (10).

The cylinder liner 10 includes a crankcase contact portion 11, a body portion 13, and an O-ring mounting groove 15 for sealing.

Crankcase Contact

The crankcase contact part 11 is a part that is coupled to the crank case, which is one of the components of the engine. The crank and crankcase are configurations that can be easily understood by those skilled in the art, and are not specifically described in this specification, and regardless of the shape or type, the portion where the cylinder liner and the crankcase abuts is referred to as a crankcase contact part. do.

In addition, the size or shape of the crankcase contact portion may be changed according to the shape of the cylinder liner.

Sealing O-ring Mounting groove

The sealing O-ring mounting groove 15 refers to a portion in which a groove to which a sealing O-ring is mounted is formed. The sealing O-ring is a configuration that can be easily understood by those skilled in the art, and it is not described in particular in this specification, and regardless of its shape or type, the cylinder liner and the sealing O-ring are mounted on the part where the sealing O-ring is mounted. It is referred to as a groove.

Torso

The body portion 13 refers to the remaining portion positioned between the crankcase contact portion 11 and the sealing O-ring mounting groove 15 as a body portion, and in particular, this portion is a portion in contact with the coolant of the wet cylinder liner.

That is, the present application relates to a technology for forming a coating layer on the outer surface of the cylinder liner in contact with the crankcase, not limiting the shape, with respect to the specific shape of the crankcase, sealing O-ring, cylinder liner, and the like.

No. 1 Hard chrome Plating layer

Further, a first hard chromium plating layer 21 is formed on the outer surface of the crankcase contact portion 11.

In the present application, hard chromium plating is applied to improve abrasion resistance as well as the aforementioned cavitation problem. In one example, hard chromium plating may mean a pure chromium metal plating layer that does not contain other metals or particles.

The method of forming the plating is not particularly limited, but various plating methods using a sulfuric acid bath, a fluorinated bath, an organic catalyst bath, or the like can be used.

Here, it is preferable that the thickness of the first hard chromium plating layer is 100 µm to 150 µm.

In addition, it is preferable that the surface hardness of the first hard chromium plating layer is 700 to 1000 Hv.

Second Hard chrome Plating layer

In addition, a second hard chromium plating layer 23 is formed on the outer surface of the body 13.

As an example, the portion where the second hard chromium plating layer is formed may be limited to a portion in contact with the cooling water supplied to the wet cylinder liner.

Here, it is preferable that the thickness of the second hard chromium plating layer is 200 µm to 250 µm.

In addition, it is preferable that the surface hardness of the second hard chromium plating layer is 700 to 1000 Hv.

As an example, an additional plating layer may be formed on the second hard chromium plating layer.

Third Hard chrome Plating layer

In addition, a third hard chromium plating layer 25 is formed on the outer surface of the O-ring mounting groove 15.

Here, it is preferable that the thickness of the third hard chromium plating layer is 100 µm to 150 µm.

Further, it is preferable that the surface hardness of the third hard chromium plating layer is 700 to 1000 Hv.

Regarding the thickness of the plating layer, as an example, at the boundary between the first hard chromium plating layer and the second hard chromium plating layer, a gradient is formed such that the thickness of the plating layer decreases from the second hard chromium plating layer toward the first hard chromium plating layer.

In addition, as an example, at the boundary between the third hard chromium plating layer and the second hard chromium plating layer, a gradient is formed so that the thickness of the plating layer decreases from the second hard chromium plating layer toward the third hard chromium plating layer.

Regarding the number of cracks in the plating layer, as an example, the number of cracks per unit length of the second hard chromium plating layer is the number of cracks per unit length of the first hard chromium plating layer and the number of cracks per unit length of the third hard chromium plating layer. Greater than That is, the number of cracks per second hard chromium plating layer formed on the outer surface of the body portion that is in contact with the cooling water is the smallest.

In the present application, since the object is to prevent cavitation damage occurring on the outer wall of the cylinder liner, the pores formed in the plating layer may be a large factor in lowering the cavitation resistance, and thus, a general hard chromium plating with a relatively dense plating layer is applied.

Through this, hard chromium plating (industrial chromium plating) is a plating that thickens the material surface by electrolyzing chromic acid in the plating solution at high current and high temperature. It has excellent hardness, and when applied to a cylinder liner, it has resistance to cavitation erosion by cooling water, so it can be used semi-permanently.

Hereinafter, the present application will be described in more detail through experimental examples.

[ Experimental example ]

In order to confirm the microstructure of the chromium plating layer formed on the outer surface of the cylinder liner, an image taken of a cross section of the cylinder liner on which the chromium plating layer is formed is shown in FIG. 6.

As shown in FIG. 4, the thickness of the plating layer was uniform at about 120 μm, and the surface hardness was about 850 Hv. Inside the plating layer, many micropores commonly found in hard chromium plating were observed, and defects such as pores or cracks were not found in the boundary layer between the plating layer and the base material (gray cast iron), so the bonding strength of the plating layer is expected to be excellent.

As described above, conventionally, a technique for extending the service life by applying a hard chromium plating technique to a piston ring or a cylinder liner of an internal combustion engine has been previously applied. In particular, in the case of cylinder liners, porous chromium plating is mainly applied to the inner wall of the cylinder to improve the permeability of lubricating oil, thereby preventing sticking of high speed and high pressure moving parts and improving wear resistance. However, in the present application, since the aim is to prevent cavitation damage occurring on the outer wall of the cylinder liner, the pores formed in the plating layer may rather become a large factor in lowering the cavitation resistance, and thus, a general hard chromium plating with a relatively dense plating layer was applied.

Although the above has been described with reference to the preferred embodiments of the present application, those skilled in the art will be able to variously modify and change the present application within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can.

10: cylinder liner
11: crankcase contact
13: torso
15: O-ring mounting groove for sealing
21: first hard chromium plating layer
23: second hard chromium plating layer
25: third hard chromium plating layer

Claims (5)

In the wet cylinder liner,
A cylinder liner including a crankcase contact portion, a body portion, and an O-ring mounting groove for sealing;
A first hard chromium plating layer formed on the outer surface of the crankcase contact portion;
A second hard chromium plating layer formed on the outer surface of the body portion; And
It includes a third hard chromium plating layer formed on the outer surface of the O-ring mounting groove,
The chromium plating layer is a pure chromium metal plating layer,
The thickness of the first hard chromium plating layer is 100 µm to 150 µm,
The thickness of the second hard chromium plating layer is 200 µm to 250 µm, and
The thickness of the third hard chromium plating layer is 100 µm to 150 µm,
At the boundary between the first hard chromium plating layer and the second hard chromium plating layer, a gradient is formed so that the thickness of the plating layer decreases from the second hard chromium plating layer toward the first hard chromium plating layer,
A wet cylinder liner having a gradient formed at a boundary between the third hard chromium plating layer and the second hard chromium plating layer so that the thickness of the plating layer decreases in a direction from the second hard chromium plating layer to the third hard chromium plating layer.
The method of claim 1,
A wet cylinder liner where the second hard chromium plating layer is formed is limited to a portion in contact with the coolant supplied to the wet cylinder liner.
delete delete The method of claim 1,
The surface hardness of the first hard chromium plating layer is 700 to 1000 Hv, the surface hardness of the second hard chromium plating layer is 700 to 1000 Hv, and the surface hardness of the third hard chromium plating layer is 700 to 1000 Hv.

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