JP2018132084A - Piston ring and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a piston ring excellent in gas sealability and chipping resistance of a hard film, and a method for producing the same.
A chamfering shape is imparted only to a hard coating 3 at an outer peripheral edge 6 of an opposing end surface 5 of a joint 4 of a piston ring coated with a hard coating.
[Selection] Figure 2 (a)

Description

  The present invention relates to a piston ring for an internal combustion engine coated with a hard coating and a method for manufacturing the same, and more particularly to a piston ring excellent in gas sealing properties and chipping resistance of a hard coating and a method for manufacturing the same.

  In recent years, the operating environment of piston rings has become more severe due to higher combustion temperatures and increased surface pressure loads associated with higher engine output and compliance with exhaust gas regulations. Therefore, in particular, in a diesel engine, as shown in Patent Document 1, for example, various sprayed piston rings having excellent wear resistance and scuff resistance are used. In general, as shown in Patent Document 2, in the piston ring, the outer peripheral sliding surface is polished into a barrel surface shape to reduce the friction loss by improving the oil film generation function. Further, as shown in Patent Document 3, In order to reduce blow-by gas as much as possible, a gas-tight special joint is used.

  The corners including the edge of the piston ring are ideally sharp as defined in Non-Patent Document 1, but the presence of burrs and jagged shapes are not recognized. So it is generally allowed to chamfer. The chamfering process is also applied to the outer periphery of the joint of the piston ring coated with a hard coating. Until now, the hard coating was formed after chamfering the outer periphery of the joint of the piston ring base material. Therefore, as shown in FIG. 7 or FIG. 8, it had a hard coating (23) following the shape of the piston ring base material (22).

  However, in addition to the mechanical stress generated in the hard coating by sliding between the piston ring outer peripheral surface and the cylinder inner peripheral surface, a large load is applied to the joint portion due to the passage of combustion gas. Therefore, even if chamfering is performed on the outer periphery of the joint as described above, the hard coating is likely to chip or peel off, and the actual situation is that the countermeasure has been taken by increasing the amount of chamfering. It was.

  On the other hand, the amount of chamfering at the outer periphery of the joint is related to the amount of blow-by gas, and it is desirable to reduce the amount of chamfering as much as possible in order to reduce blow-by gas. However, if the chamfering amount is reduced, the load is increased and the hard coating is likely to be chipped, which is not preferable. That is, in relation to the chamfering amount at the joint end, the gas sealing property and the chipping resistance of the hard coating tend to conflict with each other, and it is difficult to achieve both at a high level.

JP 2013-108174 A Japanese Utility Model Publication No.57-196238 JP-A-10-238630

International Standard, ISO 6621-5: 2005 (E), Internal combustion engines-Piston rings, Part 5: Quality requirements, page 4

  This invention makes it a subject to provide the piston ring excellent in gas-sealing property and the chipping resistance of a hard film in view of said situation. Furthermore, it is an object to provide a manufacturing method thereof.

  FIG. 8 is a circumferential partial cross-sectional view showing an abutting end when a conventional piston ring (21) coated with a hard coating is mounted on a piston and incorporated in a cylinder (30). As a result of studying the situation so far that the hard coating (23) is likely to be chipped or peeled off even when chamfering is performed on the outer peripheral edge of the joint, the inventor has found that the hard coating (23) is facing the joint facing end surface ( 25, 25), the stress field due to the friction force due to the reciprocating motion in the cylinder (30) and the stress field due to the passage of the combustion gas through the joint gap are formed at the outer peripheral edge of the cylinder (30). Creates a stress singular field that becomes the starting point for chipping and delamination due to material and shape discontinuities, and therefore, the stress singular field is the greatest weak spot of hard coatings. I came to the idea that For example, in a hard coating that follows the shape of the piston ring base material, there are stress singularities at the outer edge of the joint at the edges (a, b) of the coating surface and the edges (c, d) of the base material / film interface. Existing.

  Based on the above considerations, the present inventors have intensively studied to solve the above-mentioned problems. By eliminating the chamfering of the piston ring base material at the outer peripheral edge and adding a chamfered shape only to the hard coating, the chipping and peeling of the hard coating at the outer peripheral edge of the joint are suppressed, and the chamfering amount is also reduced. The present invention was completed by successfully obtaining a piston ring excellent in chipping resistance and gas sealability of a hard coating.

  That is, the piston ring of the present invention is an annular piston ring having a hard coating on at least an outer peripheral sliding surface, the piston ring has a joint, and the opposite end surface of the joint is chamfered only on the hard coating. An outer peripheral edge having The chamfered shape is preferably a round chamfer. Moreover, it is preferable that the said chamfering shape is a chamfering, and the chamfering angle θ of the chamfering is 10 to 60 ° from the opposed end surface.

  Moreover, it is preferable that the said joint is a gas tight type joint in which the convex part which protrudes in the circumferential direction is formed in one joint end, and the recessed part which can accept the said convex part is formed in the other joint end. Furthermore, in the gas tight type joint, it is preferable that the facing end surface is a mating surface of the convex portion and the concave portion.

  The hard coating is preferably a sprayed coating.

  The method for manufacturing a piston ring according to the present invention is a method for manufacturing an annular piston ring having a hard film on at least an outer peripheral sliding surface, and forms a joint in a piston ring base material made of cast iron or steel. And the said hard film is formed in the outer peripheral surface of the said piston ring base material in the state which pinched | interposed the separator between the opposing end surfaces of the said opening. Preferably, the outer peripheral edge of the opposed end surface of the piston ring base material is not chamfered, and after forming the hard coating, only the hard coating on the outer peripheral edge of the opposed end surface is chamfered. Is preferred.

  Moreover, it is preferable to form a thermal spray coating as the hard coating.

  The separator preferably protrudes from the outer peripheral surface of the piston ring base material in a direction perpendicular to the axis of the piston ring base material, and the thermal spray material is sprayed perpendicularly to the axis as the hard coating. preferable. In that case, it is preferable not to chamfer the hard coating on the outer peripheral edge of the opposed end surface.

  The abutment is a gas tight type abutment in which a protrusion protruding in the circumferential direction is formed at one abutment end, and a recess capable of receiving the protrusion is formed at the other abutment end. Is preferably a mating surface of the convex portion and the concave portion.

  Since the piston ring of the present invention is chamfered only on the hard coating on the outer peripheral edge of the joint, the number of stress singular fields formed by the chamfered corners is reduced, and the chip resistance of the hard coating is improved. . Further, since the chamfering amount is reduced by chamfering only the hard film, blow-by gas can be reduced and gas sealing performance can be improved.

It is a fragmentary perspective view containing the joint end part of the piston ring of this invention. It is the circumferential direction fragmentary sectional view which showed an example of the abutment edge part of the piston ring of this invention. It is the circumferential direction fragmentary sectional view which showed another example of the abutment edge part of the piston ring of this invention. It is the circumferential direction fragmentary sectional view which showed another example of the joint end part of the piston ring of this invention. It is the figure which showed an example of the gas tight type joint. FIG. 4 is a partial cross-sectional view in the circumferential direction of the gastight type joint of FIG. 3, showing an opposing end face having a mating surface of a convex part and a concave part in a direction perpendicular to the axis. FIG. 5 is an example of a first manufacturing method of the piston ring of the present invention, and is a circumferential partial cross-sectional view showing a joint end portion in which a hard film is formed with a separator interposed between the joint facing end surfaces (not protruding from the outer peripheral surface). . FIG. 7 is an example of a second manufacturing method of the piston ring of the present invention, and is a circumferential partial cross-sectional view showing a joint end portion in which a hard film is formed by sandwiching a separator (projecting from the outer peripheral surface) between the joint facing end surfaces. . It is an example of the manufacturing method of the conventional piston ring, and is the circumferential direction fragmentary sectional view which shows the abutment edge part which formed the hard film in the piston ring base material which has a chamfering shape in the outer periphery of the abutment opposing end surface. It is the circumferential direction fragmentary sectional view which showed the joint end part when a conventional piston ring is mounted | worn with a piston and was integrated in the cylinder.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a piston ring (1) according to the present invention, in which a hard coating (3) is formed on the outer peripheral surface of the piston ring base material (2), and is opposed to the abutment facing end face with an abutment gap ( 4 ). On the outer periphery (6) of (5, 5), only the hard coating (3) is chamfered. As an embodiment of the outer periphery of the joint, FIG. 2 (a) shows an example of round chamfering, FIG. 2 (b) shows an example of chamfering over the entire thickness of the hard coating (3), FIG. 2 (c) Shows an example of chamfering up to a part of the thickness of the hard coating (3).

  Here, focusing on the stress singular field, in FIGS. 2 (a) and 2 (b), there are stress singular fields in a and d, and in FIG. 2 (c) there are stress singular fields in a, b and d. Exists. In particular, since the edge portion c at the base material / film interface in FIG. 8 does not exist, expansion of the generated stress is avoided and chip resistance of the hard film is improved. Further, when the chamfering amount is reduced, the number of stress singular fields increases to three, or the stress singular fields a and b or b and d are close to each other and the hard film is likely to be chipped. In that sense, it is preferable to chamfer over the entire thickness of the hard coating.

  As the chamfered shape, round chamfering or square chamfering is generally used, but round chamfering is preferable. In the case of chamfering, it is preferable that the chamfering angle θ is 10 to 60 ° from the abutting facing end surface. 25 to 50 ° is more preferable, and 30 to 45 ° is more preferable.

  FIG. 3 shows a gastight-type special joint used in the piston ring of the present invention when airtightness is particularly required. The special joint in Fig. 3 is also called the double step joint. In the gas tight type joint, a convex part (10) protruding in the circumferential direction is formed at one joint end, and a concave part (11) capable of receiving the convex part (10) is formed at the other joint end. The mating surface (12) of the convex portion (10) and the concave portion (11) of this gas tight type joint becomes a severe stress environment that directly contacts and collides when the piston reciprocates. It is important to improve the chipping resistance of the hard film.

  In the piston ring manufacturing method of the present invention, an outer periphery of the piston ring base material is formed in a state in which a joint is formed in a piston ring base material made of cast iron or steel, and a separator is sandwiched between opposed end surfaces of the joint. A hard film is formed on the surface.

  In the first manufacturing method of the piston ring of the present invention, as shown in FIG. 5, the outer peripheral edge of the piston ring base material is not chamfered, and the separator sandwiched between the opposed end faces is a piston ring base material. A hard film is formed in a state where it does not protrude from the outer peripheral surface. After the hard coating is formed, chamfering as shown in FIGS. 2 (a) to 2 (c) is performed only on the hard coating on the outer periphery of the joint.

  In the second manufacturing method of the piston ring of the present invention, as shown in FIG. 6, the outer peripheral edge of the piston ring base material is not chamfered, and the separator sandwiched between the opposed end faces is a piston ring base material. A hard film is formed in a state of protruding from the outer peripheral surface. The degree of protrusion of the separator is preferably protruded even after the hard film is formed.

  When a hard coating is formed by protruding the separator from the outer peripheral surface, particularly when a thermal spray coating is formed as the hard coating, the quality of the hard coating near the separator depends on the spraying direction of the thermal spray material. In the mass production process of a normal sprayed piston ring, a plurality of piston rings are stacked in a cylindrical shape and set on a jig, and while rotating the jig, the spray gun or cylindrical piston ring is moved in the axial direction, Thermal spray material is sprayed on the surface. In order to make the hard coatings on both sides of the separator have the same quality, it is preferable that the spraying direction of the sprayed material is perpendicular to the axis of the piston ring base material.

  As a result of observing the structure in the vicinity of the separator with respect to the hard coating obtained by spraying the thermal spray material parallel to the separator surface, that is, perpendicular to the axis of the piston ring base material, The knowledge that a lot of structure is formed was obtained. In fact, as shown in Fig. 6, the hard film (3 ', 3') near the separator has many pores, so when the separator is removed, the hard film (3 ', 3') in that part collapses and becomes hard The film end has a slope shape, that is, a chamfered shape. Therefore, in the second manufacturing method of the piston ring of the present invention, it is not necessary to chamfer the hard coating. Of course, it is needless to say that finishing chamfering may be performed to adjust the chamfering shape.

1, 21 Piston ring of the present invention
2, 22 Piston ring base material
3, 23 Hard coating
4, 24 gap
5, 25 Opposite end face
6, 26 Outer peripheral edge
10 Convex
11 Recess
12 Abutment surface
13 Spacer
30 cylinders

Claims (14)

  An annular piston ring having a hard coating on at least an outer peripheral sliding surface, wherein the piston ring has a joint, and an opposite end surface of the joint includes an outer peripheral edge having a chamfered shape only on the hard coating. Piston ring.   2. The piston ring according to claim 1, wherein the chamfered shape is a round chamfer.   2. The piston ring according to claim 1, wherein the chamfered shape is a chamfered chamfer, and a chamfered angle θ of the chamfered chamfer is 10 to 60 ° from the opposed end surface.   The piston ring according to any one of claims 1 to 3, wherein the abutment is formed with a convex portion projecting in a circumferential direction at one abutment end, and can accept the convex portion at the other abutment end. A piston ring characterized in that it is a gas tight type abutment formed.   5. The piston ring according to claim 4, wherein the opposed end surface is a mating surface of the convex portion and the concave portion.   6. The piston ring according to claim 1, wherein the hard coating is a thermal spray coating.   A method for producing an annular piston ring having a hard coating on at least an outer peripheral sliding surface, wherein a joint is formed in a piston ring base material made of cast iron or steel, and a separator is provided between opposed end surfaces of the joint. The manufacturing method of a piston ring, wherein the hard coating is formed on an outer peripheral surface of the piston ring base material in a sandwiched state.   8. The method for manufacturing a piston ring according to claim 7, wherein chamfering is not performed on an outer peripheral edge of the opposed end surface of the piston ring base material.   9. The method of manufacturing a piston ring according to claim 7, wherein after the hard coating is formed, only the hard coating on the outer peripheral edge of the opposed end surface is chamfered. .   10. The method for manufacturing a piston ring according to claim 7, wherein a thermal spray coating is formed as the hard coating.   8. The method of manufacturing a piston ring according to claim 7, wherein the separator protrudes from the outer peripheral surface of the piston ring base material in a direction perpendicular to the axis of the piston ring base material. Method.   12. The method for manufacturing a piston ring according to claim 11, wherein a thermal spray material is sprayed perpendicularly to the axis as the hard coating.   13. The method for manufacturing a thermal spray piston ring according to claim 12, wherein the hard coating on the outer peripheral edge of the opposed end surface is not chamfered.   14. The manufacturing method of a piston ring according to claim 7, wherein the joint is formed with a protrusion protruding in the circumferential direction at one end of the joint, and the protrusion is received at the other end of the joint. A method for producing a piston ring, characterized in that it is a gas tight type joint in which possible concave portions are formed, and the opposing end surface is a mating surface of the convex portions and the concave portions.

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