JP2013148026A - Cylinder liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder liner superior in corrosion resistance to sulfuric acid, and consequently superior in abrasion resistance, in spite of having a simple and inexpensive constitution.SOLUTION: A cylinder liner 10 is the cylinder liner 10 for holding a piston 1 which is fitted and inserted, making reciprocating linear motion, via a top ring 2, a second ring 4 and an oil ring 5 being piston rings, and is characterized by applying a material 20 of high corrosion resistance to a range including at least an abutting part on the top ring 2 being the piston ring in a piston top dead center position of an inner wall surface of the cylinder liner 10 in the reciprocating linear motion direction of the piston 1.

Description

  The present invention relates to a cylinder liner for an internal combustion engine.

  Cylinder liners of internal combustion engines need to be slidably inserted and held while maintaining airtightness of pistons and piston rings that reciprocate at high speed. It is desirable to be able to slide well without causing any wear, and to prevent the piston and the piston ring from being worn or the like without violently attacking the piston and the piston ring over a long period of time.

For this reason, various improvements have been made in the past, and various types of alloy cast iron having a structure in which graphite and carbide are dispersed in a predetermined manner have been proposed, but are excellent in scuff resistance and wear resistance. As cast iron, for example, flake graphite cast iron (grey cast iron) is often employed.
In addition, Patent Document 1, Patent Document 2, and Patent Document 3 describe examples of improving the cylinder liner material.

Japanese Patent Laid-Open No. 05-214482 JP 2006-206986 A JP 2008-106357 A

  Here, it is an important subject to purify the exhaust from the internal combustion engine to suppress the expansion of air pollution. As one of the systems (apparatus) for this purpose, a part of the exhaust from the internal combustion engine is removed from the combustion chamber. A so-called EGR (Exhaust Gas Recirculation) system for reducing the concentration of nitrogen oxides (hereinafter referred to as NOx) (exhaust amount) in the exhaust gas by lowering the combustion temperature by recirculation and re-combustion. It has been adopted.

  In such an EGR system, since EGR gas is recirculated to the combustion chamber, the EGR gas may be expanded and cooled in the combustion chamber during an intake stroke or the like, and condensed water may be generated from the EGR gas.

  In recent years, in order to reduce the NOx emission amount even more effectively, the EGR gas amount is increased by cooling the EGR gas to be recirculated into the combustion chamber by using an EGR cooler or the like. Condensed water is more likely to be generated from EGR gas, and there is a high possibility that EGR gas condensed water will adhere to the combustion chamber wall (particularly, the inner wall of the cylinder liner having a low temperature).

  Here, since the EGR gas contains sulfur in the fuel, the condensed water contains sulfuric acid. Therefore, if the condensed water containing sulfuric acid adheres to or stays on the inner wall of the combustion chamber of the internal combustion engine, etc. There is a risk of causing corrosion or damage to the cylinder liner made of cast iron or the like.

  That is, as shown in FIG. 6, the condensed water containing sulfuric acid generated in the combustion chamber may adhere to the inner wall of the cylinder liner 3 in the vicinity of the top dead center of the piston 1.

  Then, the adhering sulfuric acid in the condensed water corrodes the inner wall of the cylinder liner 3 as shown in FIG. 7 in the vicinity of the top ring (piston ring) 2 (A portion in FIG. 6). ) Is generated (see FIG. 7A).

  Thereafter, when the corrosion further progresses, as shown in FIG. 7 (B), the cementite exposed to the inner wall surface of the cylinder liner 3 receives the combustion pressure from the back surface and comes into contact with the cylinder liner 3 at a high surface pressure. 2 and scraped off from the base material of the cylinder liner.

  Since the fallen cementite has very hard and brittle characteristics, as shown in FIG. 7C, the inner wall of the cylinder liner 3 and the top ring 2 or other piston ring (second ring, oil ring, etc.) It acts like abrasive powder by being crushed between them, and promotes the wear of the inner wall surface of the cylinder liner 3 and the sliding surface of the piston ring surface.

  As a result, as shown in FIG. 7D, the wear on the inner wall surface of the cylinder liner 3, particularly in the vicinity of the top ring, increases, thereby increasing the risk of increasing oil consumption and blow-by. It is assumed that the engine life and reliability may be impaired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cylinder liner that has a simple and low-cost configuration and has excellent corrosion resistance against sulfuric acid and thus excellent wear resistance.

Therefore, the cylinder liner according to the present invention is
A cylinder liner that inserts and holds a piston that reciprocates linearly through a piston ring,
A material having high corrosion resistance is applied to a range including at least a contact portion with a top ring which is a piston ring at a piston top dead center position on an inner wall surface of the cylinder liner in a reciprocating linear motion direction of the piston.

  In the present invention, the material having high corrosion resistance is an iron-based material containing a large amount of Cr.

  In the present invention, the application of the material having high corrosion resistance to the cylinder liner can be characterized by thermal spraying.

  In the present invention, the lower end of the application range of the highly corrosion-resistant material to the inner wall surface of the cylinder liner in the reciprocating linear motion direction of the piston is higher than the upper end of the ring groove of the piston ring closest to the top ring at the piston top dead center position. It can be characterized by being set to be located on the dead center side.

  Here, the lower end and the lower side correspond to the piston bottom dead center side end and the piston bottom dead center side, and the upper end and the upper side correspond to the piston top dead center side and the piston top dead center side (this specification) It is the same in the whole).

Further, in the present invention, the lower end of the application range of the highly corrosion-resistant material to the inner wall surface of the cylinder liner in the reciprocating linear motion direction of the piston is in contact with the cylinder liner of the oil ring that is the piston ring at the piston top dead center position. It is characterized in that it is set between the upper end of the part and the lower end of the ring groove of the piston ring nearest to the oil ring.

  According to the present invention, it is possible to provide a cylinder liner that has a simple and low-cost configuration but has excellent corrosion resistance against sulfuric acid and thus excellent wear resistance.

It is sectional drawing (sectional drawing which took the cross section in the plane parallel to a piston sliding direction) which shows the structural example of the cylinder liner of one Embodiment which concerns on this invention. It is sectional drawing (sectional drawing which took the cross section in the plane parallel to a piston sliding direction) which shows an example of the application range in the piston reciprocating linear motion direction of the hard film applied to the inner wall surface of the cylinder liner which concerns on embodiment same as the above. is there. Sectional drawing which shows another example of the application range in the piston reciprocating linear motion direction of the hard film applied to the inner wall surface of the cylinder liner according to the same embodiment as above (sectional view taken in a plane parallel to the piston sliding direction) ). It is a table | surface which shows an example of the component of the hard film | membrane applied to the inner wall surface of the cylinder liner which concerns on embodiment same as the above. It is a time chart which shows the frictional force change in the piston position of the piston which is inserted and hold | maintained at the cylinder liner, and reciprocates linearly. It is sectional drawing explaining the mode of the attack to the cylinder liner of the condensed water containing a sulfuric acid. It is the figure which extracted and expanded the A section of FIG. 6, and is an expanded sectional view explaining the mechanism of abrasion.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As a result of repeating various studies and experiments, the present inventors have found a cylinder liner having excellent wear resistance and corrosion resistance.

  That is, as described with reference to FIGS. 6 and 7, the wear of the cylinder liner starts from the contact position of the top ring 2 near the piston top dead center and spreads to the sliding portion in the piston bottom dead center direction. There is.

  For this reason, it is possible to suppress wear by forming a layer having high corrosion resistance in a portion where wear from the contact position of the top ring 2 at the piston top dead center position toward the bottom dead center direction is relatively large. Conceivable.

  That is, as shown in FIG. 7A, the inventor generates condensed water from the EGR gas in the expansion stroke, and the condensed water containing sulfuric acid is near the position of the top ring 2 near the top dead center of the piston. Corrosion occurs by adhering to the inner wall surface of the cylinder liner 3, and when this corrosion progresses, the cementite is exposed to the inner wall surface of the cylinder liner as shown in FIG. 7B, and this becomes abrasive powder. As shown in FIG. 7B, the present inventors have elucidated the mechanism of promoting the wear of the inner wall surface of the cylinder liner, and the present inventor has suppressed the initial corrosion due to sulfuric acid (see FIG. 7A). If it can be done, the fallout of cementite or the like (see FIG. 7B) can be suppressed, and further, the promotion of wear as shown in FIGS. 7C and 7D can be suppressed. Cylinder cylinder Near the contact position of the top ring 2 in the vicinity of the piston top dead center of the inner wall surface of the burner, it was decided to form a highly corrosion-resistant layer.

  That is, in the present embodiment, for example, as shown in FIG. 1, a material 20 having high corrosion resistance against sulfuric acid is applied to the inner wall surface of the cylinder liner 10 near the top ring 2 contact position near the top dead center of the piston 1. Applied.

  As the material 20 having high corrosion resistance against sulfuric acid, an iron-based hard coating containing a large amount of Cr can be employed. For example, a hard coating is formed by a technique such as PVD, CVD, ion plating, sputtering, or thermal spraying. Can do.

  In the present embodiment, this highly corrosion-resistant material (hard coating) 20 can be applied over the entire circumference in the circumferential direction of the inner wall surface of the cylinder liner 10.

  Further, as a range in the reciprocating linear motion direction of the piston to which the material (hard coating) 20 having high corrosion resistance against sulfuric acid is applied, as shown in FIG. 1, the contact portion with the top ring 2 in the vicinity of the top dead center of the piston 1 Can be included.

  For example, as shown in FIG. 2, the top dead center side upper end of the range (piston reciprocating linear motion direction) to which the highly corrosion-resistant material (hard coating) 20 is applied is the top ring 2 at the top dead center position of the piston 1. The bottom dead center side lower end extends to the second land of the piston 1 and can be set to be above the upper end of the ring groove of the second ring 4 at the top dead center position of the piston 1.

  As a result, the top ring 2 at the top dead center position of the piston 1 suppresses the possibility that the hard coating 20 is peeled off by attacking the boundary between the upper end of the hard coating 20 and the base material of the cylinder liner 10. can do.

  Further, at the top dead center position of the piston 1, the second ring 4 suppresses the possibility that the hard coating 20 is peeled off by attacking the boundary near the lower end side between the hard coating 20 and the base material of the cylinder liner 10. can do.

  Further, the bottom dead center side lower end of the range in which the material having high corrosion resistance (piston reciprocating linear motion direction) is applied is contacted with the cylinder liner 10 of the oil ring 5 at the top dead center position of the piston 1 as shown in FIG. It can be set between the uppermost end of the contact portion and the lower end of the ring groove of the piston ring (top ring 2, second ring 4 or third ring) closest to the oil ring 5. Note that the second ring 4 and the third ring may be omitted. In some cases, the piston ring closest to the oil ring 5 may be a 4th ring or the like.

  As a result, at the top dead center position of the piston 1, the piston ring (top ring 2, second ring 4 or third ring) immediately adjacent to the oil ring 5 and other oil rings 5 is bonded to the hard coating 20 and the base material of the cylinder liner 10. It is possible to suppress the possibility that the hard coating 20 is peeled off by attacking the boundary near the lower end side.

  In consideration of the complexity of the manufacturing process such as masking, the upper end of the range in which the highly corrosion-resistant material (hard coating) 20 is applied (in the direction of the reciprocating linear motion of the piston) extends to or near the upper end of the cylinder liner 10. It is also possible to have a configuration that exists.

  In addition, the bottom dead center side lower end of the range (the piston reciprocating linear motion direction) in which the high corrosion resistance material (hard coating) 20 is applied can be extended below the lower end of the ring groove of the oil ring 5.

Here, an example of the material (component) of the material (hard coating, eg, thermal spray coating) 20 having high corrosion resistance is shown in FIG.
As shown in FIG. 4, the component values of the hard coating (for example, thermal spray coating) are Mn = ˜0.5 (wt%), Ni = ˜0.3 (wt%), Cr = 25-30 (wt%) ), Mo = 3.5 to 4.5 (wt%), Fe = remainder.

  In addition, as hardness of a hard coating (film | membrane), it can be set as about 800Hv-1000Hv, for example.

  In addition, in order to prepare the inner wall surface of the cylinder liner 10 after applying a hard coating by thermal spraying or sputtering, a cutting process or a honing process may be performed.

  By the way, when a hard film is formed by thermal spraying, sputtering or other methods, a large number of minute irregularities are formed on the inner wall surface of the cylinder liner 10, and these minute irregularities function as an oil reservoir. Lubrication properties are improved.

  Therefore, it is possible to improve the corrosion resistance against sulfuric acid by forming a hard film, and at the same time, it is possible to improve the initial familiarity characteristics and to suppress long-term wear.

  As described above, in the present embodiment, a material having high corrosion resistance against sulfuric acid is applied to the range (region) including the contact portion of the top ring 2 at the piston top dead center position on the inner wall surface of the cylinder liner 10 (coating or the like). As shown in FIG. 7 (B), the condensed water containing sulfuric acid generated in the expansion process can withstand the attack by sulfuric acid (see FIG. 7 (A)). As shown in FIG. 7 (C) and FIG. 7 (D), the cementite and the like are exposed to the inner wall surface of the cylinder liner and fall off. Occurrence of a phenomenon such as acceleration can be suppressed, and wear of the inner wall surface of the cylinder liner 10 can be reduced over a long period of time.

  In the present embodiment, as shown in FIGS. 1 to 3, the contact portion of the top ring 2 at the piston top dead center position on the inner wall surface of the cylinder liner 10 is included in the reciprocating linear motion direction of the piston. The range is made of a material that has high corrosion resistance to sulfuric acid, so that the application range is narrowed to reduce product costs, manufacturing time, etc., while effectively preventing the fall off of cementite and the like in the early stages of wear. Thus, wear can be reduced over a long period of time.

  Furthermore, in the present embodiment, the lower end of the range including the abutting portion of the top ring 2 at the piston top dead center position on the inner wall surface of the cylinder liner 10 in the direction of the reciprocating linear motion of the piston to which a material having high corrosion resistance against sulfuric acid is applied. However, since the piston ring does not overlap with the contact position (top dead center position) with the inner wall surface of the cylinder liner 10 of each piston ring, the sliding speed becomes zero and the piston top dead center position with poor lubrication characteristics The possibility that the piston ring attacks the boundary between the material having high corrosion resistance and the base material of the cylinder liner and peeling of the material having high corrosion resistance to sulfuric acid can be effectively suppressed.

  Since the piston speed is 0 near the top dead center of the piston, oil film formation cannot be satisfactorily performed in fluid lubrication, so that the lubrication characteristics are extremely strict, such as the occurrence of boundary lubrication or solid contact locally. Therefore, as shown in FIG. 5, the frictional force becomes the maximum, and it becomes severe against the wear of the cylinder liner. In particular, since a high combustion pressure acts on the back surface of the top ring, the contact surface pressure is the highest in the piston ring, so that the lubrication characteristics and wear characteristics are severe (see FIG. 7D, etc.).

  By the way, the material of the base material of the cylinder liner 10 according to the present embodiment can be a conventional cast iron material, for example, flake graphite cast iron (grey cast iron).

  Further, the cylinder liner 10 according to the present embodiment can be employed as a cylinder liner of an internal combustion engine, but is not limited to this, and is not limited to other uses, and various It can be used for various purposes according to the purpose and request.

  In addition, the internal combustion engine in which the cylinder liner made of cast iron according to the present embodiment is used is not limited to a diesel combustion engine, and can be an internal combustion engine that uses gasoline or other fuels. Regardless, it can be any mobile / stationary internal combustion engine.

  Furthermore, the cylinder liner 10 according to the present embodiment can be used as a cylinder liner of an external combustion engine.

  The cylinder liner 10 according to the present embodiment can also be used as a cylinder liner such as an air compressor that does not involve combustion.

  Further, the cylinder liner 10 according to the present embodiment is not limited to the cylinder liner, and when the piston is directly fitted into the cylinder block without using the cylinder liner, the same processing is applied to the inner wall surface of the cylinder bore. It is also possible to apply.

  The embodiment according to the present invention described above is merely an example for explaining the present invention, and various modifications can be made without departing from the gist of the present invention.

1 piston 2 top ring (piston ring)
4 Second ring (piston ring)
5 Oil ring (piston ring)
10 Cylinder liner 20 Material with high corrosion resistance (hard coating, hard coating)

Claims (5)

A cylinder liner that inserts and holds a piston that reciprocates linearly through a piston ring,
A cylinder in which a material having high corrosion resistance is applied to a range including at least a contact portion with a top ring which is a piston ring at a piston top dead center position on an inner wall surface of the cylinder liner in a reciprocating linear motion direction of the piston. Liner.   The cylinder liner according to claim 1, wherein the material having high corrosion resistance is an iron-based material containing a large amount of Cr. The cylinder liner according to claim 1 or 2, wherein the application of the material having high corrosion resistance to the cylinder liner is thermal spraying.
Suitable hot water is   The lower end of the application range of the highly corrosion-resistant material on the inner wall surface of the cylinder liner in the reciprocating linear motion direction of the piston is closer to the piston top dead center side than the upper end of the ring groove of the piston ring closest to the top ring at the piston top dead center position. The cylinder liner according to any one of claims 1 to 3, wherein the cylinder liner is set to be positioned. The lower end of the range of application of the highly corrosion-resistant material to the inner wall surface of the cylinder liner in the direction of reciprocating linear motion of the piston is the upper end of the abutting portion of the oil ring that is the piston ring at the piston top dead center position, The cylinder liner according to any one of claims 1 to 3, wherein the cylinder liner is set between a lower end of a ring groove of a piston ring nearest to the oil ring.

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