WO2015125832A1

WO2015125832A1 - Piston ring

Info

Publication number: WO2015125832A1
Application number: PCT/JP2015/054468
Authority: WO
Inventors: 規靖加藤; 佐藤　大介
Original assignee: 株式会社リケン
Priority date: 2014-02-19
Filing date: 2015-02-18
Publication date: 2015-08-27
Also published as: JP5860571B1; JPWO2015125832A1

Abstract

Provided is a piston ring with which abrasion resistance of the outer peripheral surface can be ensured, and the formation of cylinder scratches and scuffs can be inhibited. In this piston ring (1), a hard coating (11) is formed on the outer peripheral surface (2d) of a main body part (2), and abrasion resistance to a bore inner-peripheral surface (21a) is ensured. Furthermore, on the hard coating (11), a rough surface (12) having a greater surface roughness than other sections of the hard coating (11) is formed along the peripheral direction of the main body part (2), and is unevenly positioned towards a side surface (2b) side of the main body part (2). The rough surface (12) has an affinity with oil (23) which is higher than that of the other sections of the hard coating (11), and functions as an oil pocket (P). As a result, the oil (23) thickly accumulates in the oil pocket (P) when the piston rises, and, when the piston descends, the piston ring (1) scrapes down the bore inner-peripheral surface (21a) of a cylinder (21) while the oil (23) is in a thickly accumulated state, and thus the formation of scratches and scuffs on the bore inner-peripheral surface (21a) can be inhibited.

Description

piston ring

The present invention relates to a piston ring used in an internal combustion engine.

A piston ring used in an internal combustion engine such as an automobile is provided, for example, in a ring groove on the outer peripheral surface of the piston, and has a function of suppressing oil on the cylinder inner wall from entering the combustion chamber from the crank chamber side (oil-up). Yes. As a piston ring having such a function, for example, there is a piston ring described in Patent Document 1. This conventional piston ring is a semi-inlaid piston ring in which a hard film such as a Cr—N system formed by the PVD method is formed on the outer peripheral surface of the piston ring (sliding surface with the cylinder inner wall). In the outer peripheral surface, the region where the hard coating is not formed is in a state offset to the inside of the region where the hard coating is formed.

JP 2009-287730 A

When the hard coating as described above is formed on the outer peripheral surface of the piston ring, the wear resistance to the inner peripheral surface of the bore can be improved, but scratches and scuffs are generated on the inner peripheral surface of the cylinder due to its hardness. It is conceivable to let you. Therefore, there is a demand for a technique capable of simultaneously ensuring the wear resistance of the piston ring and protecting the inner peripheral surface of the cylinder bore.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a piston ring that can ensure the wear resistance of the outer peripheral surface and suppress the occurrence of cylinder scratches and scuffing.

In order to solve the above-described problems, a piston ring according to the present invention is a piston ring that includes an annular main body portion, and an outer peripheral surface of the main body portion serves as a sliding surface with the cylinder. A hard coating with a high hardness is coated, and the hard coating is unevenly distributed on one surface side in the width direction of the main body and has a rough surface having a surface roughness larger than that of other portions of the hard coating. It is formed along the direction.

In this piston ring, a hard film is formed on the outer peripheral surface of the main body, and wear resistance to the inner peripheral surface of the bore is ensured. In addition, the hard coating has a rough surface that is unevenly distributed on one surface side in the width direction of the main body and has a surface roughness larger than that of other portions of the hard coating along the circumferential direction of the main body. This rough surface has a higher affinity with oil than other portions of the hard coating, and functions as an oil pocket in which oil accumulates. For this reason, when the piston ring is attached to the piston groove with the one side of the main body as the bottom side, the oil accumulates thickly in the oil pocket when the piston rises and the oil accumulates thickly when the piston descends. Since the bore inner circumferential surface is scraped, the bore inner circumferential surface is protected by oil, and the occurrence of cylinder scratches and scuffing can be suppressed.

Moreover, it is preferable that the main body is exposed at the end on the one surface side in the width direction of the main body on the outer peripheral surface. The above-described rough oil pocket can be suitably applied to a so-called semi-inlaid piston ring.

Further, it is preferable that the rough surface is formed at a constant interval from the boundary portion between the main body portion and the hard coating. In this case, since the oil pool by the oil pocket can be formed at the boundary portion between the main body portion and the hard coating, it is possible to suppress the occurrence of cylinder scratches and scuffing due to simultaneous contact between the main body portion and the hard coating having different hardnesses.

The width of the rough surface is preferably 1/4 to 4 times the width of the main body exposed at the end. By setting the width of the rough surface to ¼ or more of the width of the main body exposed at the end, cylinder scratches and scuffing can be prevented. Further, by setting the width of the rough surface to be four times or less the width of the main body exposed at the end, it is possible to prevent the rough surface from reaching the sliding surface with the cylinder and wearing the bore inner peripheral surface. .

The width of the rough surface is preferably 1/12 to 1/3 of the width of the main body. By setting the width of the rough surface to 1/12 or more of the width of the main body, it is possible to prevent the occurrence of cylinder scratches and scuffing. Further, by setting the width of the rough surface to 1/3 or less of the width of the main body, it is possible to prevent the rough surface from reaching the sliding surface with the cylinder and wearing the bore inner peripheral surface.

Further, it is preferable that the surface roughness of the rough surface is greater than 1 and less than or equal to 10 times the surface roughness of other portions of the hard coating. By making the surface roughness of the rough surface larger than 1 times the surface roughness of other portions of the hard coating, the function as an oil pocket can be effectively produced. In addition, by reducing the surface roughness of the rough surface to 10 times or less of the surface roughness of other parts of the hard coating, the deterioration of oil consumption and the increase of friction due to the increased oil film thickness at the time of scraping are suppressed. it can.

According to the piston ring according to the present invention, the wear resistance of the outer peripheral surface can be ensured and the occurrence of cylinder scratches and scuffing can be suppressed.

It is a perspective view which shows one Embodiment of the piston ring which concerns on this invention. It is sectional drawing of the radial direction of the piston ring shown in FIG. It is a principal part enlarged view of the outer peripheral surface of the piston ring shown in FIG. It is a figure which shows the effect | action of the piston ring at the time of a piston raise. It is a figure which shows the effect | action of the piston ring at the time of piston lowering. It is a figure explaining a reciprocating motion abrasion test.

Hereinafter, preferred embodiments of the piston ring according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a piston ring according to the present invention. A piston ring 1 shown in FIG. 1 is configured as a top ring provided in a ring groove on an outer peripheral surface of a piston in an internal combustion engine of an automobile, for example. In the piston ring 1, the outer peripheral surface 2d slides with respect to the inner peripheral surface of the bore so that the oil on the inner wall of the cylinder can be prevented from entering the combustion chamber side from the crank chamber side (oil-up). It has become.

The piston ring 1 includes an annular main body 2 and a joint portion 3 formed in a part of the main body 2. The main body 2 has a long side in the thickness direction and a short side in the width direction due to the side surface 2a and the side surface 2b that are end surfaces in the width direction and the inner peripheral surface 2c and the outer peripheral surface 2d that are end surfaces in the thickness direction. The cross section is substantially rectangular. The main body 2 is formed of, for example, cast iron or steel containing a plurality of metal elements with sufficient strength, heat resistance, and elasticity. The surface of the main body 2 may be subjected to surface modification by, for example, a hard chromium plating layer, a chromium nitride layer, or an iron nitride layer. By forming such a surface modification layer on at least the side surface 2b, the wear resistance of the main body 2 against the ring groove of the piston can be improved.

The joint part 3 is formed by parting the main body part 2. The abutment portion 3 functions as a relief portion for thermal expansion of the main body portion 2 due to a temperature difference between the piston ring 1 and the cylinder when the piston ring 1 is used. In the present embodiment, the abutment end surface 3a is illustrated as a right angle abutment formed at right angles to the inner peripheral surface 2c and the outer peripheral surface 2d, but the abutment end surface 3a is inclined with respect to the inner peripheral surface 2c and the outer peripheral surface 2d. Or a stepped joint formed so that the side surface 2a of one joint end surface 3a and the side surface 2b side of the other joint end surface protrude toward each other. Good.

Next, the outer peripheral surface 2d of the main body 2 described above will be described in more detail. FIG. 2 is a sectional view of the piston ring 1 in the radial direction. FIG. 3 is an enlarged view of a main part of the outer peripheral surface of the piston ring.

The outer peripheral surface 2d is a surface that becomes a sliding surface that slides with respect to the inner peripheral surface of the bore of the cylinder when the piston ring 1 is attached to the ring groove of the piston. As shown in FIG. 2, the outer peripheral surface 2d has a gently curved shape (barrel face shape) toward the outer side so that the vicinity of the center line A in the width direction protrudes most.

On the surface of the outer peripheral surface 2d, a hard film 11 having a hardness higher than that of the main body 2 is formed as shown in FIG. 2 from the viewpoint of ensuring wear resistance and scuff resistance. For the hard coating 11, for example, a coating using a physical vapor deposition (PVD) method is used. More specifically, the hard coating 11 is an ion plating film formed of at least one of Ti and Cr and at least one of C, N, and O. Examples of such a film include a Ti—N film, a Ti—CN film, a Cr—N film, a Cr—CN film, and a Cr—O—N film. Among these, when importance is attached to wear resistance and scuff resistance, it is preferable to use a Cr—N film. In addition, a DLC (diamond-like carbon) film may be used.

In the present embodiment, the hard coating 11 is a semi-inlaid type, and is formed on the outer peripheral surface 2d so as to cover a region excluding the end on the side surface 2b side. That is, in the outer peripheral surface 2d, the base material of the main body 2 is exposed with a predetermined width at the end portion on the side surface 2b side, and the remaining region is covered with the hard coating 11 until reaching the end portion on the side surface 2a side. It has become. The base material does not necessarily have to be nitrided. Further, the hard film 11 is formed with a rough surface 12 having a surface roughness larger than that of other portions of the hard film 11. The surface roughness of the rough surface 12 is greater than 1 time and less than or equal to 10 times the surface roughness of other portions of the hard coating 11.

As shown in FIG. 3, the rough surface 12 is unevenly distributed on the side surface 2 b side of the outer peripheral surface 2 d from the center line A, and has a certain distance from the boundary portion D between the hard coating 11 and the exposed portion of the main body 2. The portion 2 extends in the circumferential direction. The width W1 of the rough surface 12 is about 1/12 to 1/3 of the width W2 of the main body 2. The width W1 of the rough surface 12 is about 1/4 to 4 times the width W3 of the main body exposed at the end on the side surface 2b side of the outer peripheral surface 2d. The rough surface 12 may extend continuously along the circumferential direction of the main body 2 or may be partially broken. Moreover, the width | variety of the rough surface 12 may become a uniform width | variety in the circumferential direction of the main-body part 2, and one part width may differ from the width | variety of another part. Although the enlarged shape of the rough surface 12 is not specifically limited, For example, you may be formed by the countless fine recessed part. The surface roughness of the rough surface 12 can be defined by, for example, Ra (arithmetic average roughness) or Rz (maximum height). The surface roughness can be managed by controlling various parameters including Ra or Rz.

The rough surface 12 functions as an oil pocket P in which oil accumulates because the affinity with the oil is higher than that of the other portions of the hard coating 11. For this reason, when the piston ring 1 is attached to the piston groove with the side surface 2b side of the main body 2 being the bottom surface side (crank chamber side), as shown in FIG. An oil reservoir 24 is formed between the portion near the oil pocket P and the bore inner peripheral surface 21a. When the piston descends, the outer peripheral surface 2d of the piston ring 1 scrapes the bore inner peripheral surface 21a of the cylinder 21 in a state where the oil 23 is thickly accumulated in the oil pocket P as shown in FIG. Thereby, when the outer peripheral surface 2d slides on the bore inner peripheral surface 21a, the bore inner peripheral surface 21a is protected by a sufficient amount of oil 23 in the oil reservoir 24, so that the bore inner peripheral surface 21a is not damaged. Scuffing can be suppressed.

The hard coating 11 of the piston ring 1 is a semi-inlaid type provided so that the main body 2 is exposed at the end on the side surface 2b side on the outer peripheral surface 2d. The rough surface 12 is formed on the hard coating 11 with a certain distance from the boundary portion D between the main body 2 and the hard coating 11. In this way, by making the hard coating 11 a semi-inlaid type, the sharp portion at the end of the outer peripheral surface 2d (the intersection of the outer peripheral surface 2d and the side surface 2b and its periphery) is covered with the hard coating 11 in the bore. It is possible to avoid hitting the inner peripheral surface 21a and to prevent the hard coating 11 from being cracked or chipped. Further, since the oil reservoir 24 by the oil pocket P can be formed corresponding to the boundary portion D between the main body 2 and the hard coating 11, the main body 2 and the hard coating 11 having different hardnesses simultaneously hit the bore inner peripheral surface 21a. The occurrence of scratches and scuffs can be prevented.

Further, the width W1 of the rough surface 12 is 1/12 to 1/3 of the width W2 of the main body 2, and further, 1/4 to 4 of the width W3 of the main body 2 exposed at the end. It has doubled. By setting it to be equal to or more than the lower limit of the range, it is possible to prevent the occurrence of cylinder scratches and scuffing. In addition, by setting it to be equal to or less than the upper limit of the range, it is possible to prevent the rough surface 12 from reaching the sliding surface with the cylinder 21 and wearing the bore inner peripheral surface 21a.

Moreover, the surface roughness of the rough surface 12 is larger than 1 times and 10 times or less of the surface roughness of the other part of the hard film 11. By making the surface roughness of the rough surface 12 larger than one time the surface roughness of other portions of the hard coating 11, the function as the oil pocket P can be effectively produced. In addition, by making the surface roughness of the rough surface 12 10 times or less than the surface roughness of the other part of the hard coating 11, the oil consumption is increased and the friction is increased due to the increased oil film thickness at the time of scraping. Can be suppressed.

The hard coating 11 and the rough surface 12 on the outer peripheral surface 2d of the piston ring 1 described above can be formed by the following processes, for example. First, a barrel face shape and an inlaid projection (a portion corresponding to an exposed portion of the main body 2 on the outer peripheral surface 2d) are formed in advance on the outer peripheral portion of the main body 2. At this time, the depth and width W1 of the oil pocket P are determined based on the depth of the valley formed by the inlaid protrusion and the barrel face portion. As a method for forming these shapes, a known technique such as cutting, grinding, lapping, and polishing is selected as appropriate. Next, the hard film 11 is formed on the outer peripheral surface 2d by the PVD method. The surface roughness of the oil pocket P is determined by the base material roughness (surface roughness of the outer peripheral surface 2d) before the formation of the hard coating 11, and before the hard coating 11 is applied to the outer peripheral surface 2d, shot blasting and wet honing are performed. It can be adjusted by appropriately selecting a known technique such as acid treatment. The base material nitriding layer under the hard coating 11 may or may not be present. After the hard coating 11 is formed, the inlaid protrusions on the outer peripheral surface 2d are removed, and the outer peripheral surface 2d is barrel face lapped, so that the hard coating 11 and the rough surface 12 shown in FIGS. 2d can be formed. For removal of the inlaid protrusion and barrel face finishing, a known technique such as lapping or polishing is appropriately selected.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the piston ring 1 in which the outer peripheral surface 2d has a barrel face shape is illustrated. However, in the present invention, the outer peripheral surface 2d is a flat surface and is orthogonal to the side surfaces 2a and 2b of the main body 2. Piston with a straight face shape, a tapered face shape in which the outer peripheral surface 2d is a flat surface and inclined with respect to the side surfaces 2a and 2b of the main body 2, and an eccentric barrel face shape in which the barrel face shape apex of the outer peripheral surface 2d is eccentric to the side surface 2b It can also be applied to rings. Further, for example, in the above embodiment, the semi-inlaid type hard coating 11 in which the base material of the main body 2 is exposed at the end of the outer peripheral surface 2d on the side surface 2b side is illustrated. However, in the present invention, the entire outer peripheral surface 2d is hard. Even a full face type covered with the film 11 is applicable.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Examples 1 to 9)
The piston rings of Examples 1 to 9 were manufactured by the following procedure. Except for the matters shown in Table 1, the production methods and specifications of the piston rings of Examples 1 to 9 were the same. First, a piston ring (top ring) in which the barrel face part and the protrusion part are located on the outer peripheral surface was formed. The material of the piston ring was JIS standard SUS440B. The dimensions of the piston ring were about 80 mm in diameter, about 3.0 mm in thickness, and about 1.2 mm in width. The surface of the piston ring was nitrided with gas to form a nitrided layer having a thickness of about 10 μm to 20 μm.

Next, shot blasting was performed on a part of the outer peripheral surface of the piston ring to form a region having a large surface roughness on the outer peripheral surface extending in the circumferential direction. The region having a large surface roughness on the outer peripheral surface was formed in the barrel face portion having a certain distance from the boundary between the barrel face portion and the protruding portion. After the formation of the region, a semi-inlaid type hard coating composed of chromium nitride was formed on the barrel face portion by ion plating. After forming the hard coating, the protrusions on the outer peripheral surface were removed. And the outer peripheral surface was barrel face-wrapped. Thereby, a barrel face type piston ring provided with a hard film having a rough surface was prepared. The rough surface was formed on a region where the surface roughness of the barrel face portion was large. Table 1 shows the width W1 of the rough surface, the width W2 of the main body, and the width W3 of the main body exposed at the end on the side surface side of the outer peripheral surface in each example. In each embodiment, the ratio (W1 / W3) of the width W1 of the rough surface to the width W3 of the main body exposed at the end on the side surface side of the outer peripheral surface and the width of the rough surface with respect to the width W2 of the main body. The ratio of W1 (W1 / W2) is also shown in Table 1.

(Comparative Example 1)
Barrel face type piston rings were prepared in the same manner as in Examples 1 to 9, except that shot blasting was not performed on a part of the barrel face portion of the piston ring. For this reason, the rough surface is not formed in the hard film of the piston ring in Comparative Example 1. In Comparative Example 1, the width W2 of the main body and the width W3 of the main body exposed at the end on the side surface side of the outer peripheral surface are shown in Table 1.

(Surface roughness)
For each of the hard coatings of Examples 1 to 9, the surface roughness Ra and Rz of the portion where the rough surface was formed and the portion where the rough surface was not formed were measured. The surface roughness Ra and Rz were measured based on the method described in JIS B 0601 2001 using a surface roughness / contour measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 1800D). The measurement conditions for the surface roughness were a cut-off value of 0.8 mm, an evaluation length of 4.0 mm, a measurement speed of 0.3 mm / s, and a tip radius of a 60 ° conical stylus of 2 μm. The measurement direction of the surface roughness was the circumferential direction on the outer peripheral surface of the piston ring. The surface roughness of each part of the hard coatings of Examples 1 to 9 was measured at five points, and the average value of each part was calculated. In Examples 1 to 9, Ra (α) or Rz (α) is the average value of the surface roughness of the portion where the rough surface is formed, and the average value of the surface roughness of the portion where the rough surface is not formed. Ra (β) or Rz (β) was used. Table 1 shows Ra (α) / Ra (β) and Rz (α) / Rz (β) in Examples 1 to 9, respectively.

(Oil consumption)
The piston rings of Examples 1 to 9 and Comparative Example 1 were respectively installed in the piston top ring grooves in a gasoline engine with a displacement of 2.4 L and an in-line 4-cylinder. The oil consumption was measured for each of the examples and the comparative examples when the gasoline engine was operated for a predetermined time under the conditions of 6800 rpm and full load (WOT: Wide Open Throttle). In Examples 1 to 9 and Comparative Example 1, the second ring and the oil ring were used as a common ring. The oil consumption was calculated by measuring the amount of oil stored before the gasoline engine operation and the amount of oil stored after the gasoline engine operation. Table 1 shows the oil consumption amounts of the other examples and Comparative Example 1 when the oil consumption amount of Example 9 is 100%.

(Reciprocating wear test)
In order to evaluate the sliding characteristics of the piston ring and the cylinder bore used in Examples 1 to 9 and Comparative Example 1, a reciprocating wear test described below was performed. FIG. 6 is a diagram for explaining the reciprocating wear test. As shown in FIG. 6, in the reciprocating wear test, a test piece 31 made of the same material as the cylinder bore, a sample 32 formed by cutting out a part of the piston ring of each example or comparative example 1, and lubricating oil The oil supply part 33 to supply was used. The test piece 31 is fixed to be drivable along a certain direction, and a surface 31 a of the test piece 31 facing the sample 32 is recessed along the shape of the sample 32. A constant load is applied to the sample 32 along a direction perpendicular to the surface 31a of the test piece 31, and the sample 32 is pressed against and fixed to the surface 31a. The surface of the sample 32 corresponding to the outer peripheral surface of the piston ring is in contact with the surface 31 a of the test piece 31. The oil supply unit 33 is arranged to supply the lubricating oil onto the surface 31 a of the test piece 31.

In the reciprocating wear test, the test piece 31 was reciprocated for 10 hours along the direction of the arrow shown in FIG. 6 with a stroke of 100 mm and an average moving speed of 2.0 m / s at a test temperature of 120 ° C. Made it work. At this time, the sample 32 was pressed against the surface 31a of the test piece 31 with a load of 200N, and the lubricating oil was dropped from the oil supply unit 33 onto the surface 31a. The dripping amount of the lubricating oil was 0.15 ml / min. After the reciprocating operation of the test piece 31 was completed, the wear amount of each test piece 31 was measured and the state of the surface 31a was confirmed. Table 1 shows the wear amounts of the other examples and Comparative Example 1 when the wear amount of the test piece 31 of Example 8 is 100%. Table 1 also shows the results of confirming the state of the surface 31a of Examples 1 to 9 and Comparative Example 1. Here, the state of the surface 31a of the test piece 31 is determined by checking the presence or absence of scratches with the naked eye, and “A” indicates that no scratch is confirmed on the surface 31a, and “B” indicates that the scratch is confirmed on the surface 31a. B ".

As shown in Table 1, in Examples 1 to 9, no scratch was confirmed on the surface 31a of the test piece 31. On the other hand, in Comparative Example 1, scratches were confirmed on the surface 31 a of the test piece 31. That is, when the rough surface is formed on the hard coating of the piston rings of Examples 1 to 9, it is considered that the generation of cylinder scratches and scuffing can be suppressed. However, for example, when the width W1 is significantly shorter than the width W3 (for example, when W1 / W3 is less than 0.25), or when the width W1 is significantly shorter than the width W2 (for example, W1 / W2 is In the case of less than 0.08), the portion occupied by the rough surface in the hard coating is small, and the effect of the rough surface is not sufficiently exerted, so that it is considered that the possibility of cylinder scratches increases.

The piston ring according to one embodiment of the present invention can be used as, for example, a piston ring of an automobile engine.

DESCRIPTION OF SYMBOLS 1 ... Piston ring, 2 ... Main body part, 2b ... Side surface (one surface), 2d ... Outer peripheral surface, 11 ... Hard film, 12 ... Rough surface, D ... Border part, W1 ... Rough surface width, W2 ... Main body part width , W3: The width of the main body exposed at the end of the outer peripheral surface.

Claims

A piston ring comprising an annular main body, the outer peripheral surface of the main body being a sliding surface with the cylinder,
The outer peripheral surface is coated with a hard film having a higher hardness than the main body,
The hard coating is a piston having a rough surface that is unevenly distributed on one surface side in the width direction of the main body and has a larger surface roughness than other portions of the hard coating along the circumferential direction of the main body. ring.
The piston ring according to claim 1, wherein, on the outer peripheral surface, the main body portion is exposed at an end portion on one surface side in the width direction of the main body portion.
3. The piston ring according to claim 2, wherein the rough surface is formed at a constant interval from a boundary portion between the main body portion and the hard coating.
4. The piston ring according to claim 2, wherein a width of the rough surface is 1/4 to 4 times a width of the main body exposed at the end.
5. The piston ring according to claim 1, wherein a width of the rough surface is 1/12 to 1/3 of a width of the main body.
The piston ring according to any one of claims 1 to 5, wherein the surface roughness of the rough surface is greater than 1 time and less than or equal to 10 times the surface roughness of other portions of the hard coating.