JP2022187021A - Oil ring for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil ring for an internal combustion engine which enables reduction of swell occurring during manufacturing of the oil ring while securing oil consumption reduction effect to improve oil seal performance.

SOLUTION: An oil ring 1 for an internal combustion engine includes: an oil ring body 2 in which a cross sectional shape of the oil ring is a substantially I shape; and a coil expander 3 disposed at the inner periphery side of the oil ring body 2. The oil ring body 2 comprises: a first rail 5 and a second rail 6 which contact with a cylinder inner wall surface; and a web 4 including multiple oil return holes 7 for flowing oil scraped from the inner wall surface of a cylinder by the first rail 5 and the second rail 6 to a piston rear surface. A swell in at least one of a portion 2f which excludes an inner peripheral groove 2e and an oil return groove 2d at the inner periphery side of the oil ring body 2 and a slide surface 8A at the outer periphery side of the oil ring body 2 is 4.0 μm or less.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a two-piece oil ring for an internal combustion engine, which includes an oil ring body and a coil expander.

With the recent improvement in the performance of internal combustion engines (piston type reciprocating engines, etc.), oil rings used in automobile engines are also required to satisfy both reduced frictional force and reduced engine oil consumption. It is Therefore, various measures have been taken for the shape of the oil ring and the like. For example, in order to reduce the frictional force, an oil ring arranged in the cylinder bore has a low tension, and in order to improve oil consumption, a thin oil ring is used.

In general, there are two-piece oil rings and three-piece oil rings with different structures. The two-piece oil ring has high rigidity and is resistant to heat load, so it is mainly used for diesel engines.

The oil ring main body in this two-piece oil ring has a substantially I-shaped cross section, and consists of an upper rail (first rail) forming the upper part of the oil ring main body and a lower rail (first rail) forming the lower part of the oil ring main body. second rail) and a web connecting these rails. The web also has a plurality of oil return holes for allowing the oil scraped off from the inner wall surface of the cylinder by these rails to flow down to the back surface of the piston.
When the piston reciprocates, the outer peripheral sliding surfaces of the upper rail and the lower rail slide against the inner wall surface of the cylinder with an oil film interposed therebetween. An oil ring has the function of scraping off excess engine oil on the inner wall surface of the cylinder and the function of forming an appropriate oil film on the inner wall surface of the cylinder to prevent seizure of the piston. is essential.

By the way, in recent years, a wire rod manufacturer has manufactured a wire rod for an oil ring having a substantially I-shaped cross section, and then a piston ring manufacturer has performed coiling molding (winding processing) to form an oil ring main body of a two-piece oil ring. The most popular method of manufacturing is In this case, the oil return hole is generally already formed in the state of the oil ring wire.

For example, Patent Document 1 discloses a method of manufacturing a two-piece oil ring by forming an oil return hole in such a wire rod for an oil ring and then performing coiling molding. Further, Patent Document 2 discloses the pitch and length of the oil return holes provided in the oil ring main body of the two-piece oil ring. It was set to quickly release the oil scraped off by the oil ring to the back of the piston, but the oil seal performance required for the two-piece oil ring was not considered.

Japanese Patent Laid-Open No. 61-45172 WO2011/132679

However, in the oil ring wire having the oil return hole, there is a difference in rigidity between the portion where the oil return hole is formed and the portion where the oil return hole is not formed. Excessive waviness occurs on the outer peripheral sliding surface of the tip portion, which may impair the oil seal performance. More specifically, the outer peripheral sliding surface at the tip of the rail undulates in the radial direction of the oil ring main body, and when viewed from the axial direction of the oil ring main body, the outer peripheral sliding surface has a so-called petal shape. There was a possibility that the oil seal performance would be impaired due to the reduction in the roundness of the sliding surface.

Here, after the coiling molding (winding process), the outer peripheral sliding surface of the rail tip portion of the oil ring body is polished by barrel polishing or the like, so that the outer peripheral sliding surface of the rail tip portion of the oil ring body is rounded. It is conceivable to improve the oil seal performance by increasing the
However, in the oil ring, it is also required to reduce engine oil consumption by scraping off excess oil from the inner wall surface of the cylinder when the piston descends, while suppressing excessive oil scraping when the piston ascends. be done. Therefore, for the following reasons, it is not possible to adopt a method of polishing the outer peripheral sliding surface of the rail tip portion of the oil ring body by barrel polishing or the like to improve the oil sealing performance.

That is, in order to reduce the amount of oil consumption, the tip portions of the first rail and the second rail in the oil ring main body are arranged in a cross-sectional view taken along a plane parallel to the axial direction of the oil ring main body. A shape as shown in is used.

Specifically, in FIGS. 3A and 3B, the tip portion 8 includes a substantially flat first flat portion (outer peripheral sliding surface) 8A that contacts the inner wall surface 21 of the cylinder 20, and a first flat portion 8A. A first diameter-reduced portion 8B whose diameter is reduced along one of the axial directions (vertical direction in FIGS. 3A and 3B) of the oil ring body (upward in the drawings), and a first flat portion 8A from the oil ring body A second flat portion 8C whose diameter is reduced along the other axial direction (downward in the figure), and a second flat portion continuous with the first reduced diameter portion 8B and substantially perpendicular to the cylinder inner wall surface 21 8D, and a third flat portion 8E that is continuous with the second reduced diameter portion 8C and substantially perpendicular to the inner wall surface 21 of the cylinder. When one end of the first reduced diameter portion 8B is a and the other end is b, and one end of the second reduced diameter portion 8C is c and the other end is d, the distance ab between a and b is The angle θ _ab formed between a straight line longer than the distance cd between c and d and connecting a and b and a straight line parallel to the cylinder inner wall surface 21 is defined by the straight line connecting c and d and the cylinder inner wall surface 21 is smaller than the angle θ _cd formed with a straight line parallel to 21 .

The oil ring is attached to the piston so that the first reduced diameter portion 8B is located above the piston and the second reduced diameter portion 8C is located below the piston. When the piston is raised, the first diameter-reduced portion 8B having a long distance _ab and a small angle θab rides on the oil film of the engine oil, thereby suppressing the oil from being scraped up. On the other hand, when the piston descends, the second diameter-reduced portion 8C, which has a short distance _cd and a large angle θcd, scrapes excess oil from the inner wall surface of the cylinder, thereby efficiently storing the oil in the oil pan. can reduce oil consumption.

In addition, as shown in FIG. 3C, the distal end portion 8 does not have the second diameter-reduced portion 8C as shown in FIGS. Even with an oil ring having a flat portion 8E, the same effects as described above can be obtained by locating the first diameter-reduced portion 8B on the upper side of the piston.

Also, in order to similarly reduce oil consumption, the tip portions of the first rail and the second rail in the oil ring body are shown in FIG. Such a shape may be used.

That is, the front end portion 8 has a concave step 8F formed at a corner of the outer peripheral sliding surface 8A facing the web 4. As shown in FIG. By making the outer peripheral shape of the first rail 5 and the second rail 6 as shown in FIG. 4A, even if the oil ring is used for a long period of time, the outer peripheral sliding surfaces of the first rail 5 and the second rail 6 will not be damaged. The area of 8A is less likely to change, and the effect of suppressing an increase in oil consumption can be stably obtained for a long period of time. In addition, it is possible to improve and stabilize the function of scraping off excess oil from the inner wall surface of the cylinder and the function of controlling the thickness of the oil film on the inner wall surface of the cylinder. As a result, the internal combustion engine oil ring 1 can quickly drain the oil scraped off by itself to the oil drain hole provided on the back side of the oil ring, thereby reducing oil consumption.

In addition, the oil ring in which the tip portions of the first rail and the second rail in the oil ring body have a specific shape as described above is already in the state of the oil ring wire, and the portion that can become the tip portion of the rail after coiling molding. is processed into a predetermined shape. When the outer peripheral sliding surface of the oil ring main body is polished by barrel polishing or the like after the coiling is formed, the shape of the tip portion is greatly different between the portion that protrudes due to the undulations and the portion that does not. The contact width with the cylinder becomes uneven. As a result, the oil ring body has different oil scraping performance depending on the location in the circumferential direction.

The present invention has been made in view of the above-mentioned problems, and its object is to reduce waviness that occurs during the manufacture of an oil ring and improve oil seal performance while ensuring the effect of reducing oil consumption. To provide an oil ring for an internal combustion engine capable of

The present invention consists of the following configuration (1).
(1) An oil ring body having a substantially I-shaped cross section, and a coil expander disposed on the inner peripheral side of the oil ring body,
The oil ring body includes first and second rails that contact the inner wall surface of the cylinder, and a plurality of rails for causing oil scraped off from the inner wall surface of the cylinder by the first rail and the second rail to flow down to the back surface of the piston. a web with oil return holes,
At least one of a portion on the inner peripheral side of the oil ring body excluding the inner peripheral groove and the oil return groove and a portion on the outer peripheral side of the oil ring body excluding the sliding surface has undulation of 6.0 μm or less. An oil ring for an internal combustion engine characterized by:

Further, preferred embodiments of the present invention have the following configurations (2) to (13).
(2) The oil ring for an internal combustion engine according to (1), wherein the oil ring main body is formed by winding an oil ring wire formed with the oil return hole.
(3) The oil ring for an internal combustion engine according to (1) or (2), wherein the window angle _θw of the oil return hole in the oil ring main body is 10.0° or less.
(4) The oil ring for an internal combustion engine according to any one of (1) to (3), wherein the contact width between the sliding surface and the cylinder is 0.01 to 0.25 mm.
(5) Where C is the length of the oil return hole and E is the pitch of the oil return hole in the circumferential direction of the oil ring body, E/C≤3.8, (1) to (4) ), the internal combustion engine oil ring according to any one of .
(6) The oil ring for an internal combustion engine according to any one of (1) to (5), wherein the oil ring main body is made of steel.
(7) The oil ring for an internal combustion engine according to any one of (1) to (6), wherein the surface of the oil ring main body is subjected to nitriding treatment.
(8) Any one of (1) to (7), wherein the sliding surface of the oil ring body is coated with at least one of a PVD film, a DLC film, and a resin film as a hard film. The oil ring for an internal combustion engine according to .

(9) The oil ring for an internal combustion engine according to any one of (1) to (8), wherein recessed steps are formed at the corners of the sliding surface.
(10) The tip of the first rail and the tip of the second rail are
a substantially flat first flat portion abutting against the inner wall surface of the cylinder;
a first reduced-diameter portion having a reduced diameter along one of the axial directions of the oil ring body from the first flat portion;
a second flat portion continuous with the first reduced diameter portion;
A third flat portion continuous to the first flat portion via a second diameter-reduced portion whose diameter is reduced from the first flat portion along the other axial direction of the oil ring main body, or directly The oil ring for an internal combustion engine according to any one of (1) to (8), comprising:
(11) When the distal end portion includes the second reduced diameter portion,
In a cross-sectional view cut along a plane parallel to the axial direction of the oil ring body,
When one end of the first reduced diameter portion is a and the other end is b, and one end of the second reduced diameter portion is c and the other end is d,
The distance ab between the a and the b is longer than the distance cd between the c and the d, and
The angle θ _ab formed by the straight line connecting the a and the b and the straight line parallel to the inner wall surface of the cylinder is the angle between the straight line connecting the c and d and the straight line parallel to the inner wall surface of the cylinder. The oil ring for an internal combustion engine according to (10), which is smaller than _θcd .
(12) The internal combustion engine according to any one of (2) to (11), wherein C≧1.0 mm, where C is the length of the oil return hole in the circumferential direction of the oil ring body. for oil ring.
(13) The internal combustion engine according to any one of (2) to (12), wherein D is 0.3 mm, where D is the height of the oil return hole in the axial direction of the oil ring body. for oil ring.

According to the oil ring for an internal combustion engine of the present invention, it is possible to reduce the waviness that occurs during the manufacture of the oil ring and improve the oil seal performance while ensuring the effect of reducing oil consumption.

FIG. 1 is a perspective view of an internal combustion engine oil ring (two-piece oil ring) composed of an oil ring main body and a coil expander arranged on the inner peripheral side of the oil ring main body, according to an embodiment of the present invention. be. FIG. 2 is a cross-sectional view taken along a plane parallel to the axial direction of the piston for explaining the state in which the oil ring for an internal combustion engine according to the embodiment of the present invention is mounted in the oil ring groove of the piston. . FIG. 3A is a cross-sectional view showing an example in which the tip of the first rail or the second rail is cut along a plane parallel to the axial direction of the oil ring body. FIG. 3B is a cross-sectional view showing another example when the tip of the first rail or the second rail is cut along a plane parallel to the axial direction of the oil ring body. FIG. 3C is a cross-sectional view showing another example when the tip of the first rail or the second rail is cut along a plane parallel to the axial direction of the oil ring body. FIG. 4A is a cross-sectional view showing an example of the shape of the rail outer peripheral surface of the oil ring body when the oil ring body is cut along a plane parallel to the axial direction of the oil ring body. FIG. 4B is a cross-sectional view showing another example of the shape of the rail outer peripheral surface of the oil ring body when the oil ring body is cut along a plane parallel to the axial direction of the oil ring body. FIG. 5A is a front view of the oil ring body according to the embodiment of the present invention when viewed from the radially outer side of the oil ring body. FIG. 5B is a cross-sectional view taken along line II of FIG. 5A. FIG. 5C is a schematic diagram showing a range of angles from 45° to 315° clockwise from the abutment, with the abutment of the oil ring main body being 0°. FIG. 6 is a developed view showing an example of the result of measuring the ring circumferential direction with a roundness measuring machine. FIG. 7 is a cross-sectional view showing a method of measuring the inner peripheral side of the internal combustion engine oil ring. FIG. 8 is an enlarged view for explaining a method of measuring the inner peripheral side of the internal combustion engine oil ring. FIG. 9 is a cross-sectional view showing a method of measuring the outer peripheral side of an oil ring for an internal combustion engine. FIG. 10 is an enlarged view for explaining a method of measuring the outer peripheral side of the internal combustion engine oil ring. FIG. 11 is a front view of the oil ring main body as seen from the radially outer side, for explaining the shape of the oil return hole provided in the oil ring main body according to the embodiment of the present invention. FIG. 12 is a cross-sectional view taken along a plane parallel to the axial direction of the oil ring body for explaining the state in which the outer surface of the oil ring body according to the embodiment of the present invention is nitrided. FIG. 13 is a graph showing the correlation between the window angle and the amount of waviness based on the results of Test Example 2(d).

Hereinafter, an oil ring for an internal combustion engine according to an embodiment (this embodiment) of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below, and can be arbitrarily modified without departing from the gist of the present invention.

FIG. 1 is a perspective view of an internal combustion engine oil ring (two-piece oil ring) 1 including an oil ring body 2 according to the present embodiment and a coil expander 3 arranged on the inner peripheral side of the oil ring body 2 . . As shown in FIG. 1 , an internal combustion engine oil ring 1 includes an oil ring body 2 and a coil expander 3 . Further, the oil ring main body 2 is a ring having a substantially I-shaped cross section, and is provided with an abutment portion 2a. The oil ring main body 2 is constructed by integrating a first rail 5 on the upper side, a second rail 6 on the lower side, and a web 4 connecting these rails and positioned in the middle portion of the oil ring main body 2. ing.

The first rail 5 and the second rail 6 that constitute the oil ring main body 2 are formed in a substantially circular shape in the circumferential direction of the internal combustion engine oil ring 1 . The outer peripheral sliding surface 8A (see FIG. 2), which is the sliding surface on the outer peripheral side of each of the first rail 5 and the second rail 6, is in contact with the inner wall surface 21 (see FIG. 2) of the cylinder 20 and the oil film. and slides in the axial direction of the piston. Further, as shown in FIG. 1, the web 4 is substantially circular in the circumferential direction of the oil ring body 2 and has an oil return hole 7 formed through it in the radial direction. A plurality of them are arranged in the circumferential direction of the ring body 2 . Also, the coil expander 3 is a helical spring formed into an arc shape. Although not shown, the coil expander 3 uses a core wire for a joint in the abutment portion 2a of the coil expander 3 in order to connect the abutment portion 2a of the coil expander 3 to form an annular coil.

FIG. 2 is a cross-sectional view taken along a plane parallel to the axial direction of the piston 10 in order to explain how the internal combustion engine oil ring 1 according to the present embodiment is mounted in the oil ring groove 11 of the piston 10. FIG. be. As shown in FIG. 2, on the inner peripheral surface of the oil ring main body 2, a coil expander accommodation recess 2b is formed along the circumferential direction of the oil ring main body 2 by the first rail 5, the second rail 6 and the web 4. It is On the outer peripheral surface side of the oil ring main body 2, when viewed in a cross section cut along a plane parallel to the axial direction of the oil ring main body 2 by the first rail 5, the second rail 6 and the web 4, there is a recessed shape. An outer circumferential groove 2 c having a shape is formed along the circumferential direction of the oil ring body 2 .

Further, as shown in FIG. 2, the internal combustion engine oil ring 1 according to the present embodiment is provided with an inner peripheral groove 2e having an arcuate cross section on its inner peripheral side. The coil expander housing recess 2b has a substantially semicircular shape when viewed in a cross section taken along a plane parallel to the axial direction of the oil ring main body 2. As shown in FIG. Further, the coil expander 3 is housed in a substantially semicircular portion in a state of being wrapped when viewed in a cross section taken along a plane parallel to the axial direction of the oil ring main body 2 . Therefore, according to the oil ring 1 for an internal combustion engine according to the present embodiment, when the inner circumference of the oil ring body 2 is arc-shaped, a large contact area between the oil ring body 2 and the coil expander 3 can be ensured. Therefore, the pressing force against the inner wall surface 21 of the cylinder can be stabilized. Further, like the oil ring 1 for an internal combustion engine according to the present embodiment, by forming the inner periphery of the oil ring body 2 into an arc shape, the pressing force against the cylinder inner wall surface 21 in the circumferential direction of the oil ring body 2 is localized. It is less likely that significant variations will occur, and oil will be less likely to be left unscraped.

Here, a series of flow of the oil scraping function of the internal combustion engine oil ring 1 will be described with reference to FIG. 2 . First, when the piston 10 reciprocates in the cylinder 20, the outer peripheral sliding surface 8A of the first rail 5 and the second rail 6 provided in the oil ring main body 2 removes excess oil adhering to the inner wall surface 21 of the cylinder. scrape off. The scraped oil temporarily stays in the outer peripheral groove 2c of the oil ring main body 2, and then flows through the oil return hole 7 into the coil expander accommodation recess 2b. Subsequently, the oil that has flowed into the coil expander housing recess 2b flows down to the back surface of the piston 10 through the oil drain hole 12 provided in communication with the oil ring groove 11, and into the oil pan (not shown). returned.

According to the internal combustion engine oil ring 1 according to the present embodiment, in a series of flows in the oil scraping function of the internal combustion engine oil ring 1, scraped oil is passed through the oil return hole 7 into the coil expander accommodation recess. When flowing to 2b, obstruction of oil flow can be prevented. This is because by forming the oil return groove 2d between the oil ring body 2 and the coil expander 3, the oil return hole 7 formed in the oil ring body 2 is not blocked. That is, in the internal combustion engine oil ring 1 according to the present embodiment, even if the shape of the oil ring main body 2 on the side where the coil expander is arranged is substantially semicircular, the presence of the oil return groove 2d allows the internal combustion The oil scraped off by the engine oil ring 1 can be immediately released to the oil drain hole 12 provided on the rear side of the oil ring, and the oil consumption can be reduced.

Next, an example of the shapes of the tip portions 8 of the first rail 5 and the second rail 6 will be described with reference to FIGS. 3A to 3C. As described above, in an oil ring for an internal combustion engine, oil consumption is reduced by scraping off excess oil from the inner wall surface of the cylinder when the piston is lowered while suppressing oil from being scraped up when the piston is raised. It is required to let

Therefore, when the internal combustion engine oil ring 1 is attached to the piston 10, the tip portions 8 of the first rail 5 and the second rail 6 have different shapes on the piston upper side and the piston lower side. Specifically, in FIGS. 3A and 3B, the tip portion 8 includes a substantially flat first flat portion (outer peripheral sliding surface) 8A that contacts the inner wall surface 21 of the cylinder 20, and a first flat portion 8A. A first reduced diameter portion 8B whose diameter is reduced along one (upper in the figure) of the oil ring main body axial direction (vertical direction in FIG. 3A), and a first flat portion 8A from the oil ring main body axial direction A second reduced diameter portion 8C whose diameter is reduced along the other side (lower side in the figure), a second flat portion 8D that is continuous with the first reduced diameter portion 8B and is substantially perpendicular to the cylinder inner wall surface 21, A third flat portion 8E that is continuous with the second reduced diameter portion 8C and substantially perpendicular to the cylinder inner wall surface 21 is provided. When one end of the first reduced diameter portion 8B is a and the other end is b, and one end of the second reduced diameter portion 8C is c and the other end is d, the distance ab between a and b is The angle θ _ab formed between a straight line longer than the distance cd between c and d and connecting a and b and a straight line parallel to the cylinder inner wall surface 21 is defined by the straight line connecting c and d and the cylinder inner wall surface 21 is smaller than the angle θ _cd formed with a straight line parallel to 21 . The shapes of the tip portions 8 of the first rail 5 and the second rail 6 have the same shape.

The internal combustion engine oil ring 1 is attached to the piston 10 so that the first reduced diameter portion 8B is located above the piston and the second reduced diameter portion 8C is located below the piston. When the piston is raised, the first diameter-reduced portion 8B having a long distance _ab and a small angle θab rides on the oil film of the engine oil, thereby suppressing the oil from being scraped up. On the other hand, when the piston descends, the second diameter-reduced portion 8C, which has a short distance _cd and a large angle θcd, scrapes excess oil from the inner wall surface 21 of the cylinder, thereby efficiently feeding the oil pan. Oil consumption can be reduced by returning the oil.

In FIGS. 3A and 3B, the second diameter-reduced portion 8C is shown by a gentle curve, but the diameter is reduced along the other axial direction of the oil ring main body from the first flat portion 8A. If there is, it may be indicated by, for example, a straight line.

Moreover, as shown in FIG. 3C, the distal end portion 8 does not have the second diameter-reduced portion 8C as shown in FIGS. (that is, when the first flat portion 8A and the third flat portion 8E intersect at the intersection point e), the first reduced diameter portion 8B is located above the piston The same effect as above can be obtained by positioning as follows.

In this manner, the tip portions 8 of the first rail 5 and the second rail 6 have desired shapes respectively on the upper side and the lower side of the piston. That is, the tip portions 8 of the first rail 5 and the second rail 6 have a vertically asymmetrical shape (that is, asymmetrical with respect to the center in the thickness direction of the first rail 5 or the second rail 6). . As a result, it is possible to reduce oil consumption both when the piston is raised and when the piston is lowered.

Note that the above-described first flat portion 8A does not have to be exactly flat as long as it can come into contact with the inner wall surface 21 of the cylinder. Also, the first diameter-reduced portion 8B may be tapered (linear) as shown in FIG. It may have a gently curved surface. Furthermore, the second flat portion 8D and the third flat portion 8E may not be strictly perpendicular to the cylinder inner wall surface 21, and the second flat portion 8D and the third flat portion 8E may It is preferable that the angle formed by the straight line parallel to the wall surface 21 is 45 to 90°.
Further, as the shape of the tip portion 8 of the first rail 5 and the second rail 6, the shape as shown in FIG. 3A may be used for both rails, or the shape as shown in FIG. 3B may be used for both rails. , both rails may be shaped as shown in FIG. 3C. Alternatively, there may be a combination of rails having differently shaped tips 8, with one rail having the shape shown in FIG. 3A and the other rail having the shape shown in FIG. 3B. However, both the first rail 5 and the second rail 6 need to be configured so that the first diameter-reduced portion 8B is positioned above the piston.

Next, another example of the shapes of the tip portions 8 of the first rail 5 and the second rail 6 will be described with reference to FIG. 4A. The front end portion 8 has a concave step 8F formed at a corner of the outer peripheral sliding surface 8A facing the web 4. As shown in FIG. In this way, by forming the predetermined concave step 8F as the outer peripheral shape of the first rail 5 and the second rail 6, even if the oil ring is used for a long period of time, the outer peripheral shape of the first rail 5 and the second rail 6 will not be affected. The area of the sliding surface 8A is unlikely to change, and the effect of suppressing an increase in oil consumption can be stably obtained for a long period of time. In addition, it is possible to improve and stabilize the function of scraping off excess oil from the inner wall surface of the cylinder and the function of controlling the thickness of the oil film on the inner wall surface of the cylinder. As a result, the internal combustion engine oil ring 1 can quickly drain the oil scraped off by itself to the oil drain hole provided on the back side of the oil ring, thereby reducing oil consumption.

By forming the concave step 8F in the tip portion 8, the contact width X (see FIG. 4A) of the outer peripheral sliding surface 8A with the cylinder 20 can be set to, for example, about 0.01 to 0.25 mm. .

Thus, if the contact width X is smaller than 0.01 mm, the strength of the outer peripheral sliding surface 8A may be lowered, and the tip of the tip portion 8 may be chipped or otherwise damaged, which is not preferable. On the other hand, if the contact width X is larger than 0.25 mm, the sliding area of the outer peripheral sliding surface 8A becomes large, leading to an increase in friction and oil consumption, which is not preferable. Therefore, the contact width X is preferably 0.01 to 0.25 mm.

As a specific processing method for forming the recessed portion step 8F, various types of grinding or cutting may be appropriately selected. , which is preferable because the processing man-hours for grinding and cutting can be reduced.

Furthermore, it is preferable to form a surface treatment layer 8G at least in the vicinity of the outer peripheral sliding surface 8A (the portion surrounded by α in FIG. 4A). The surface treatment layer 8G may be subjected to any treatment as long as the hard surface treatment is performed so as to improve the hardness of the outer peripheral sliding surface 8A. For example, PVD coating, DLC coating, etc. , a nitriding layer, a composite treatment film in which a DLC film is applied on a PVD film, a resin film containing a solid lubricant (molybdenum disulfide, graphite, etc.) in polyamide-imide, and the like are preferably used. Incidentally, the thickness of the surface treatment layer 8G is preferably 1 to 30 μm.

As described above, even when the recessed portion 8F is formed in the tip portion 8, the tip portion 8 has desired different shapes on the upper side and the lower side of the piston, respectively, as described above. That is, the tip portions 8 of the first rail 5 and the second rail 6 are positioned symmetrically across the web 4 . In the case of such a shape, there is no risk of erroneously assembling upside down.

The shapes of the tip portions 8 of the first rail 5 and the second rail 6 are not limited to the shapes shown in FIGS. 3A to 3C and FIG. 4A. 8 may have a shape that does not have a concave step. Also in the shape shown in FIG. 4B, it is preferable to form the surface treatment layer 8G on the tip end portions 8 of the first rail 5 and the second rail 6 .

Next, the window angle _{.theta..sub.W} of the oil return hole 7 in the oil ring main body 2 and the waviness generated on the outer peripheral sliding surface 8A will be described in detail. In order to ensure the effect of reducing oil consumption, the present inventors coiled (wound) the oil ring wire, and then removed the outer peripheral sliding surface 8A of the rail tip portion 8 in the oil ring main body 2 from the barrel. In order to obtain an internal combustion engine oil ring capable of reducing waviness generated during manufacturing of the internal combustion engine oil ring 1 and improving the oil seal performance without polishing by polishing or the like, extensive studies have been made.
As a result, by setting the window angle _θW of the oil return hole 7 in the oil ring body 2 to a predetermined range, as defined below, the outer peripheral sliding surface 8A of the rail tip portion 8 in the oil ring body 2 can be It was found that the generated swell can be reduced.

In the oil ring 1 for an internal combustion engine according to this embodiment, it is preferable that the window angle θ _W of the oil return hole 7 in the oil ring body 2 is 10.0° or less. In order to more effectively reduce the undulation, the window angle θ _W is preferably 8.0° or less, preferably 7.0° or less, and further preferably 6.0° or less. is preferred.

Here, FIG. 5A is a front view of essential parts of the oil ring body 2 according to the present embodiment when viewed from the radially outer side of the oil ring body 2 . FIG. 5B is a cross-sectional view taken along line II of FIG. 5A. As shown in FIG. 5B, the window angle θ _W of the oil return hole 7 in the oil ring main body 2 is determined between the center point G (center of gravity) of the oil ring main body 2 and A straight line GE ₁ connecting one circumferential end E ₁ of the oil ring main body 2 in a certain oil return hole 7 , a center point G of the oil ring main body 2 and one end E ₂ of the oil ring main body 2 in the adjacent oil return hole 7 is defined by the angle formed by a straight line _GE2 connecting In other words, the center point G of the oil ring body 2, the straight line GE ₁ connecting _one end E1 of the pitch E in the circumferential direction of the web 4 in the oil return hole 7, the center point G of the oil ring body 2, It is also defined as an angle formed by a straight line _GE2 connecting the other end E2 of the pitch E in the circumferential direction of the web ₄ in the oil return hole 7 .

By setting the window angle θ _W to 10.0° or less, the pitch E in the circumferential direction of the web 4 in the oil return holes 7 is reduced, so that the concentration of stress in the oil ring body is alleviated and the strain is increased. , The difference in strain between the portion having the window (oil return hole 7) and the portion (web 4) having small strain and not having the oil return hole 7 is reduced, thereby reducing waviness generated in the oil ring body 2. can do.

The window angle _θW is determined by the cylinder bore diameter (the diameter of the oil ring main body 2 when the abutment 2a of the oil ring main body 2 is closed) and the pitch E of the oil return hole 7 in the circumferential direction of the web 4. is represented by the following formula.
Window angle θ _W = (360 x pitch E)/(π x cylinder bore diameter)

The waviness generated in at least one of the portion on the inner peripheral side of the oil ring main body 2 excluding the inner peripheral groove 2e and the portion on the outer peripheral side of the oil ring main body 2 excluding the sliding surface (outer peripheral sliding surface) 8A is 0 μm or less, preferably 4.0 μm or less, and preferably 3.0 μm or less. The smaller the waviness, the more the oil seal performance can be improved. For example, in order to reduce the waviness to 6.0 μm or less, the window angle θ _W should be set to 10.0° or less. Further, in order to reduce the waviness to 2.0 μm or less, the window angle θ _W should be set to 6.0° or less. Further, in order to further reduce the undulation, the window angle θ _W should be set to be smaller than 4.0°.

It should be noted that the undulation occurs in at least one of the portion on the inner peripheral side of the oil ring main body 2 excluding the inner peripheral groove 2e and the oil return groove 2d and the portion on the outer peripheral side of the oil ring main body 2 excluding the sliding surface 8A. , and is defined as an average value obtained by taking two consecutive three points of peak-and-valley amplitude adjacent in the circumferential direction. As for the circumferential direction, as shown in FIG. 5C, the angle from the ring abutment portion 2a is set within a range of 45° to 315° clockwise, with the abutment portion being 0°.

The undulation can be measured by measuring the inner or outer peripheral shape of the first rail 5 or the second rail 6 using a general roundness measuring instrument (details will be described later). Next, FIG. 6 is a developed view showing an example of the result of measuring the ring circumferential direction with a roundness measuring machine. In this developed view, the measured waviness is obtained by averaging three points (A, B, C and D, E, F) of three consecutive amplitude points of peaks and valleys adjacent in the circumferential direction. In consideration of followability to the cylinder, it is necessary to find and set the average peak-to-valley amplitude locally so that oil does not remain unscrewed. For roundness, even if the number is the same as waviness, the ring can follow the cylinder bore if it is a low-order deformation, but if it is a high-order deformation, it may not follow. Can not.

It should be noted that the outer peripheral sliding surface 8A of the first rail 5 or the second rail 6 may change its shape due to sliding friction with the inner wall surface of the cylinder after grinding or polishing, or after the internal combustion engine oil ring 1 is used. Therefore, at least one of a portion excluding the inner peripheral groove 2e and the oil return groove 2d on the inner peripheral side of the oil ring main body 2 and a portion excluding the sliding surface 8A on the outer peripheral side of the oil ring main body 2 . Since the inner peripheral surface is not ground or polished, and there is no sliding friction with the inner wall surface of the cylinder, there is no possibility that the shape will change even after use, and the outer peripheral surface of the first rail 5 or the second rail 6 and the Since the amount of waviness generated on the inner peripheral surface is almost the same, in determining whether or not the waviness generated at the time of manufacturing the oil ring satisfies a predetermined value or less, the inner peripheral groove 2e of the oil ring body 2 and the oil return groove are used. A site 2f other than 2d is measured (see FIGS. 2 and 4A).

Here, the method for measuring the inner peripheral shape or the outer peripheral shape of the oil ring main body 2 is as follows. First, a method for measuring the inner peripheral shape of the oil ring main body 2 will be described. As shown in FIG. 7, the coil expander 3 is attached to the oil ring main body 2, and assembled so that the outer peripheral sliding surface 8A of the rail tip portion of the oil ring main body 2 is in contact with the inner peripheral surface 40A of the circular gauge 40. . At this time, the tension of the coil expander 3 is preferably set to about 5N.

With the oil ring main body 2 attached to the circle gauge 40 in this way, as shown in FIG. The circle gauge 40 is rotated together with the oil ring main body 2 while being brought into contact with the portion 2f other than the groove 2d to measure the inner peripheral shape.

Next, a method for measuring the outer peripheral shape of the oil ring main body 2 will be described. As shown in FIG. 9, by assembling the oil ring main body 2 so that the outer peripheral sliding surface 8A of the rail tip portion of the oil ring main body 2 is in contact with the inner peripheral surface 40A of the circular gauge 40, the oil ring main body 2 is moved by the circular gauge 40. As shown in FIG. , the oil ring main body 2 is sandwiched between the upper and lower gauges 42, 42 from the axial direction (vertical direction in the figure). Subsequently, by removing the circle gauge 40, the outer peripheral side of the oil ring main body 2 is exposed. At this time, the tension of the coil expander 3 is preferably set to about 5 N so that the oil ring main body 2 does not fall off the upper and lower gauges 42, 42 due to the tension of the coil expander 3.

With the oil ring main body 2 sandwiched between the upper and lower gauges 42, 42, as shown in FIG. , polishing, etc., or the shape of the internal combustion engine oil ring 1 is not changed due to sliding friction with the inner wall surface of the cylinder after the oil ring 1 is used. It is rotated together with the main body 2 to measure the outer peripheral shape.

Next, other preferable conditions for the internal combustion engine oil ring 1 according to this embodiment will be described.
The oil return hole 7 provided in the web 4 constituting the oil ring body 2 has a length (opening width) C (width indicated by C in FIG. 11) in the circumferential direction of the oil ring body 2 of 1.0 mm or more. , more preferably 1.5 mm or more, and even more preferably 2.0 mm or more.
FIG. 11 is a front view of the oil ring main body 2 as seen from the outside in the radial direction, for explaining the shape of the oil return hole 7 provided in the oil ring main body 2 of this embodiment. 11, when the opening width C of the oil ring main body 2 according to this embodiment is smaller than 1.0 mm, the opening area of the oil return hole 7 is too small, so that the internal combustion engine oil ring 1 is scraped off. Oil cannot be quickly drained to the oil drain hole 12 provided on the back side of the internal combustion engine oil ring 1 .

Also, the opening width C is preferably 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.5 mm or less. If the opening width C is larger than 4.0 mm, the area of the oil return hole 7 is too large, and the strength of the oil ring main body 2 is reduced. You can't get durability. Furthermore, if the area of the oil return hole 7 is too large, the oil ring main body 2 is likely to be deformed during machining, resulting in deterioration of the oil scraping function.

The oil return hole 7 provided in the web 4 constituting the oil ring body 2 has a height (opening height) D (height indicated by D in FIG. 11) in the axial direction of the oil ring body 2 of 0.3 mm. It is preferably 0.4 mm or more, more preferably 0.4 mm or more.
If the opening height D is less than 0.3 mm, the opening area of the oil return hole 7 is too small. The oil cannot be discharged to the oil drain hole 12 provided in the .

Moreover, the opening height D is preferably 1.0 mm or less. If the opening height D is more than 1.0 mm, the area of the oil return hole 7 is too large, and the strength of the oil ring main body 2 is lowered, and the strength is sufficient when the internal combustion engine oil ring 1 is applied to an internal combustion engine. durability cannot be obtained. Furthermore, if the area of the oil return hole 7 is too large, the oil ring main body 2 is likely to be deformed during machining, resulting in deterioration of the oil scraping function.

Note that the shape of the oil return hole 7 is not limited to the one in which the sides corresponding to the opening height D at both ends of the rectangular shape are formed as arc-shaped sides having a constant radius of curvature R, as shown in FIG. For example, as long as the required characteristics of the oil ring are satisfied, various shapes such as a rectangle, a circle, an ellipse, and a shape with curved sides corresponding to the opening height D can be appropriately selected and used. .

Further, in the internal combustion engine oil ring 1 according to this embodiment, the axial width h1 of the oil ring main body 2 (the width indicated by h1 in FIG. 2) is preferably 1.0 mm to 4.0 mm.

Further, in the internal combustion engine oil ring 1 according to this embodiment, the radial width a1 (the width indicated by a1 in FIG. 2) of the oil ring main body 2 is preferably 1.5 mm to 3.0 mm.
Here, as shown in FIG. 2, if the radial width a1 of the oil ring main body 2 is smaller than 1.5 mm, there is a possibility that the ease of assembly to the piston will deteriorate. On the other hand, if the radial width a1 of the oil ring main body 2 is larger than 3.0 mm, the rigidity is high, and there is a risk that the followability will be poor.

Further, in the internal combustion engine oil ring 1 according to the present embodiment, the tension ratio to the cylinder bore diameter of the internal combustion engine oil ring 1 is preferably 0.05 N/mm to 0.7 N/mm.

The oil ring 1 for an internal combustion engine according to the present embodiment has a tension ratio (a value calculated by [oil ring tension (N)]/[cylinder bore diameter (mm)]) to a cylinder bore diameter (not shown) of 0.5. It is set to 05 N/mm to 0.5 N/mm. Here, when the tension ratio to the cylinder bore diameter is smaller than 0.05 N/mm, the pressing force of the outer peripheral sliding surface 8A of the rail tip portion 8 in the oil ring body 2 against the cylinder inner wall surface 21 becomes insufficient. In this case, the outer peripheral sliding surface 8A cannot sufficiently scrape off excess oil, resulting in an increase in oil consumption. Further, when the tension ratio to the cylinder bore diameter is greater than 0.5 N/mm, the pressing force of the outer peripheral sliding surface 8A against the cylinder inner wall surface 21 becomes too large, resulting in increased frictional force and reduced fuel consumption. put away. Generally, the frictional force between the cylinder and the oil ring tends to be proportional to the tension of the oil ring.

Further, in the internal combustion engine oil ring 1 according to the present embodiment, the pitch E of the oil return holes 7 provided in the web 4 constituting the oil ring body 2 in the circumferential direction of the web 4 (the pitch indicated by E in FIG. 11) is preferably 2.0 mm to 6.0 mm.

In FIG. 11 , E indicates the pitch of the oil return holes 7 provided in the web 4 forming the oil ring body 2 in the circumferential direction of the web 4 . The internal combustion engine oil ring 1 according to the present embodiment has a pitch E within the range of 2.0 mm to 6.0 mm, so that both durability and oil consumption performance of the internal combustion engine oil ring 1 are improved. can be done. Here, if the pitch E is less than 2.0 mm, the interval between the oil return holes 7 in the web 4 is too short, the strength of the oil ring main body 2 is lowered, and the durability of the internal combustion engine oil ring 1 is reduced. It will be inferior and is not preferable. If the pitch E exceeds 6.0 mm, the interval between the oil return holes 7 in the web 4 becomes too long, and the oil scraped off by the internal combustion engine oil ring 1 cannot escape to the back side of the piston. , leading to an increase in oil consumption.

In the oil ring 1 for an internal combustion engine according to the present embodiment, the pitch in the circumferential direction of the web 4 of the oil return holes 7 provided in the web 4 constituting the oil ring body 2 is E, and the circumferential direction of the web 4 of the oil return holes is is preferably E/C≦3.8, more preferably E/C≦3.0, and even more preferably E/C<2.0.

In FIG. 11, E indicates the pitch in the circumferential direction of the oil ring body 2 in the oil return hole 7, and C indicates the length in the circumferential direction of the oil ring body 2 in the oil return hole 7. there is In the oil ring 1 for an internal combustion engine according to this embodiment, the relationship "E/C" between the pitch E and the length C is 3.8 or less, so that the oil consumption performance can be improved.
Here, when the relationship "E/C" between the pitch E and the length C is more than 3.8, the interval between the oil return holes 7 in the web 4 is long, so that the internal combustion engine oil ring 1 is scraped. Dropped oil cannot escape to the back side of the piston, resulting in an increase in oil consumption.

Further, in the internal combustion engine oil ring 1 according to the present embodiment, it is preferable to set the thickness F of the nitride layer 30 to 150 μm or less when nitriding the outer surface of the oil ring main body 2 . By subjecting the oil ring body 2 to nitriding treatment, the outer surface can be hardened and the durability can be improved. This is because the oil ring main body 2 is required to have higher wear resistance due to the recent increase in speed and load of internal combustion engines for automobiles.
The oil ring main body 2 is mainly made of steel, and has a very hard nitrided layer 30 made of nitride that reacts with chromium or iron when the oil ring main body 2 is subjected to nitriding treatment. That is, by forming the nitride layer 30 on the surface of the oil ring body 2, the oil ring main body 2 has excellent wear resistance and scuff resistance against the cylinder, and can withstand use under more severe conditions. A ring 1 can be provided. However, if the entire base material of the oil ring main body 2 is nitrided by performing the nitriding treatment, the oil ring main body 2 becomes too hard and brittle, resulting in a reduction in breakage resistance. Therefore, when nitriding the oil ring main body 2 of the present embodiment, it is preferable to set the thickness F of the nitrided layer 30 to 150 μm or less.

FIG. 12 is a cross-sectional view of the state in which the outer surface of the oil ring body 2 of the present embodiment is nitrided, taken along a plane parallel to the axial direction of the oil ring body 2 . As shown in FIG. 12, a nitride layer 30 is formed on the outer surface of the oil ring body 2 . Here, the thickness F of the nitride layer 30 is preferably set to 150 μm or less.

Further, the durability of the internal combustion engine oil ring 1 affects the magnitude of the frictional force between the outer peripheral sliding surface 8A of the rail tip portion 8 in the oil ring body 2 and the inner wall surface 21 of the cylinder. , the magnitude of the tension of the internal combustion engine oil ring 1 is considered, but it is also affected by the combination of sliding metals. For example, if the sliding metal materials are chromium or aluminum, seizure is likely to occur.

Therefore, it is common to apply a coating having excellent wear resistance after considering the material of the metal. Similarly, the outer peripheral sliding surface 8A is preferably coated with a PVD film, a DLC film, or a resin film as a hard film, if necessary. In particular, it is also possible to form a film made of chromium nitride (Cr ₂ N, CrN) or an ion plating film made of a mixture of chromium nitride (Cr ₂ N, CrN) and chromium (Cr) from the viewpoint of wear resistance. In addition, the durability of the oil ring is also improved by forming a film such as a nitride (Cr-B-N) made of chromium-boron, DLC (hydrogen-free DLC, hydrogen-containing DLC, metal-containing DLC, etc.). can be improved.

The material of the oil ring main body 2 is not particularly limited and can be designed as appropriate. It is preferably equivalent to SUS410J1, SWRH77B, or SUS440B.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Test Example 1: When the rail tip has a shape as shown in FIG. 3B>
[(a) Examples 1 to 9 and Comparative Examples 1 to 2: when the cylinder bore diameter is 86 mm]
An in-line 4-cylinder diesel engine with a displacement of 2000cc and a cylinder bore diameter of 86mm was tested on an actual machine, and it was confirmed whether or not the amount of waviness generated in the main body of the oil ring would differ depending on the size of the window angle _θw of the oil return hole. did In addition, the difference in oil consumption due to the size of the opening width C of the oil return hole was also confirmed. The operating conditions of the engine were full load, 4000 rpm, and 8 hours.
Also, the combination of piston rings was a 1st ring, a 2nd ring, and an oil ring.

The 1st ring is made of martensitic stainless steel (equivalent to SUS410J1 according to JIS standards) having an axial width (h1) of 2.0 mm and a radial width (a1) of 3.1 mm, and is nitrided (thickness of the nitrided layer: 100 μm), the outer peripheral sliding surface was coated with a 20 μm-thick film of a mixture of chromium nitride and chromium by PVD method. The second ring was made of 10Cr steel and had an axial width (h1) of 1.5 mm and a radial width (a1) of 3.1 mm.

The martensitic stainless steel constituting the 1st ring contains carbon (C): 0.65% by mass, silicon (Si): 0.30% by mass, manganese (Mn): 0.30% by mass, chromium (Cr): 13.5% by mass, molybdenum (Mo): 0.30% by mass, phosphorus (P): 0.02% by mass, sulfur (S): 0.01% by mass, the balance being iron (Fe) and inevitable impurities and the PVD treatment is applied after the nitriding treatment.
The 10Cr steel constituting the 2nd ring is carbon (C): 0.50% by mass, silicon (Si): 0.21% by mass, manganese (Mn): 0.30% by mass, chromium (Cr): 10.1 % by mass, phosphorus (P): 0.02 mass %, sulfur (S): 0.01 mass %, and the balance being iron (Fe) and unavoidable impurities.

As the oil ring, the two-piece internal combustion engine oil ring described in the above embodiment was used. The oil rings used in Examples 1 to 9 and Comparative Examples 1 and 2 had an axial width (h1) of 2.00 mm and a radial width (a1) of 2.00 mm. made common.
Further, in the oil rings used in Examples 1 to 9 and Comparative Examples 1 and 2, as shown in FIG. Having a portion 8B, a second reduced diameter portion 8C, a second flat portion 8D and a third flat portion 8E, the distance ab is longer than the distance _cd , and the angle _θab is smaller than the angle θcd (distance ab = 96.8 µm, distance cd = 65.0 µm, angle θ _ab = 7.7°, angle θ _cd = 36.6°), and the first diameter-reduced portion 8B is located above the piston and the second 2 was attached to the piston so that the reduced diameter portion 8C of 2 was on the lower side of the piston. In all of Examples 1 to 9 and Comparative Examples 1 and 2, the tip of the first rail and the tip of the second rail had substantially the same shape.

Table 1 shows conditions for the opening width C (mm) of the oil return hole, the opening height D (mm) of the oil return hole, and the pitch E (mm) of the oil return hole shown in FIG. As shown in Table 1, the opening height D of the oil return holes is 0.55 mm in common, and the opening width C (mm) of the oil return holes and the pitch E (mm) of the oil return holes are the same as those of the examples and the comparative examples. Set different conditions for each.

The oil ring main body constituting the oil ring contains carbon (C): 0.65% by mass, silicon (Si): 0.40% by mass, manganese (Mn): 0.30% by mass, phosphorus (P): 0.01% by mass, sulfur (S): 0.01% by mass, chromium (Cr): 13.6% by mass, molybdenum (Mo): 0.3% by mass, the balance being iron (Fe) and inevitable impurities (equivalent to SUS410J1 according to JIS standards), and after nitriding, the outer peripheral sliding surface is coated with a 20 μm-thick film made of a mixture of chromium nitride and chromium by the PVD method. be. Further, the contact width X (distance ac between a and c in FIG. 3B) of the outer peripheral sliding surface 8A with the cylinder 20 was adjusted to 0.02 to 0.10 mm.
In addition, when the nitriding treatment was performed, as a result of confirming the nitride layer on the outer peripheral sliding surface (the layer indicated by F in FIG. 12) in the cross section in the oil ring axial direction, it was found that the nitriding layer had a thickness of 100 μm in the oil ring radial direction. It was confirmed that layers were formed. The coil expander has carbon (C): 0.55% by mass, silicon (Si): 1.41% by mass, manganese (Mn): 0.65% by mass, and chromium (Cr): 0.68% by mass. , Copper (Cu): 0.06% by mass, Phosphorus (P): 0.01% by mass, Sulfur (S): 0.01% by mass, and the balance being iron (Fe) and inevitable impurities (SWOSC- (equivalent to V material) was used.
Also, the material of the cylinder was plain cast iron.

In Examples 1 to 9 and Comparative Examples 1 and 2, oil consumption was checked using an oil ring having a tension ratio of 0.2 N/mm to the cylinder bore diameter. Table 1 shows the oil consumption ratio for each test as a relative ratio to the reference "100", which is the oil consumption of Comparative Example 1.
In addition, the waviness (μm) of the oil ring main body was measured using a roundness measuring instrument (product name: RONDCOM55B, manufactured by Tokyo Seimitsu Co., Ltd.). It was calculated by measuring the site 2f of. Table 1 also shows the measurement results of waviness.

[(b) Examples 10 to 13 and Comparative Examples 3 to 4: when the cylinder bore diameter is 70 mm]
An in-line four-cylinder diesel engine with a displacement of 1500 cc and a cylinder bore diameter of 70 mm was tested on an actual machine to confirm whether or not the amount of waviness generated in the main body of the oil ring would differ depending on the size of the window angle _θw of the oil return hole. did In addition, the difference in oil consumption due to the size of the opening width C of the oil return hole was also confirmed.

The oil rings used in Examples 10 to 13 and Comparative Examples 3 and 4 had an axial width (h1) of 2.00 mm and an oil ring radial width (a1) of 2.00 mm. used something.
Table 2 shows the conditions for the opening width C (mm) of the oil return holes, the opening height D (mm) of the oil return holes, and the pitch E (mm) of the oil return holes. As shown in Table 2, the opening height D of the oil return hole is 0.55 mm in common, and the opening width C (mm) of the oil return hole and the pitch E (mm) of the oil return hole are different from those of the examples and the comparison. Different conditions were set for each example.
Further, in Examples 10 to 13 and Comparative Examples 3 and 4, the oil ring main body was not subjected to nitriding treatment, and a mixture of chromium nitride and chromium having a film thickness of 20 μm was applied to the outer peripheral sliding surface by the PVD method. A product coated with a film consisting of was used. Further, the contact width X (distance ac between a and c in FIG. 3B) of the outer peripheral sliding surface 8A with the cylinder 20 was adjusted to 0.02 to 0.10 mm.
The test conditions other than those described above are the same as those in "Test Example 1(a): Examples 1 to 9 and Comparative Examples 1 to 2", so description thereof is omitted.

In Examples 10 to 13 and Comparative Examples 3 to 4, oil consumption was checked using an oil ring having a tension ratio to the cylinder bore diameter of 0.2 N/mm. Table 2 shows the oil consumption ratio for each test as a relative ratio to the reference "100", which is the oil consumption of Comparative Example 3.
Table 2 also shows the results of "waviness (μm)".

[(c) Examples 14 to 19 and Comparative Examples 5 to 6: when the cylinder bore diameter is 116 mm]
An in-line 6-cylinder diesel engine with a displacement of 10,000 cc and a cylinder bore diameter of 116 mm was tested on an actual machine, and it was confirmed whether or not the amount of waviness generated in the main body of the oil ring would differ depending on the size of the window angle _θw of the oil return hole. did In addition, the difference in oil consumption due to the size of the opening width C of the oil return hole was also confirmed.

The oil rings used in Examples 14 to 19 and Comparative Examples 5 to 6 had an axial width (h1) of 3.00 mm and a radial width (a1) of 2.35 mm. used something.
Table 3 shows the conditions for the opening width C (mm) of the oil return holes, the opening height D (mm) of the oil return holes, and the pitch E (mm) of the oil return holes. As shown in Table 3, the opening height D of the oil return hole is 0.70 mm or 0.55 mm, and the opening width C (mm) of the oil return hole and the pitch E (mm) of the oil return hole are Different conditions were set for each example and comparative example.
In Examples 14 to 19 and Comparative Examples 5 to 6, only the nitriding treatment was performed on the oil ring main body, and coating of a mixture of chromium nitride and chromium by the PVD method was not performed. The contact width X (distance ac between a and c in FIG. 3B) of the outer peripheral sliding surface 8A with the cylinder 20 was adjusted to 0.02 to 0.15 mm.
The test conditions other than those described above are the same as those in "Test Example 1(a): Examples 1 to 9 and Comparative Examples 1 to 2", so description thereof is omitted.

In Examples 13-15 and Comparative Examples 8-10, oil consumption was checked using an oil ring having a tension ratio to the cylinder bore diameter of 0.4 N/mm. Table 3 shows the oil consumption ratio for each test as a relative ratio to the reference "100", which is the oil consumption of Comparative Example 5.
Table 3 also shows the results of "waviness (μm)".

<Test Example 2: When the rail tip has a shape as shown in FIG. 4A>
[(d) Examples 20 to 40 and Comparative Examples 7 to 13: Measurement of final shapes in various oil rings]
As shown in Test Example 1, in the oil rings used in Examples 1 to 19 and Comparative Examples 1 to 6, the rail tip portion had a shape as shown in FIG. In the case of the oil ring having a concave step as shown in FIG. 4A, it was confirmed whether or not the amount of waviness generated in the oil ring main body would differ depending on the size of the window angle _θw of the oil return hole in the same manner as described above. did

In this test example, the final shape of an oil ring with a cylinder bore diameter of 64.0 to 147.0 mm was measured. As shown in Tables 4 and 5, the oil rings used in Examples 20 to 40 and Comparative Examples 7 to 13 were set under different conditions for each Example and Comparative Example.

In Examples 20 to 40 and Comparative Examples 7 to 13, the oil ring main body constituting the oil ring was composed of carbon (C): 0.70 mass%, silicon (Si): 0.25 mass%, manganese ( Mn): 0.30% by mass, phosphorus (P): 0.01% by mass, sulfur (S): 0.01% by mass, chromium (Cr): 8.05% by mass, the balance being iron (Fe) and unavoidable The composition of impurities (equivalent to 8Cr steel) was applied, the oil ring body was nitrided, and the outer peripheral sliding surface was coated with a film consisting of a mixture of chromium nitride and chromium with a thickness of 20 μm by the PVD method. used things. Further, the contact width X between the outer peripheral sliding surface 8A and the cylinder 20 shown in FIG. 4A was adjusted to 0.05 to 0.20 mm.

The results of "waviness (μm)" are also shown in Tables 4 and 5.

[(e) Examples 41 to 51 and Comparative Examples 14 to 17: Tests including measurement of oil consumption ratio] As in Examples 20 to 40 and Comparative Examples 7 to 13, the rail tip portion was as shown in FIG. It was confirmed whether or not the amount of waviness produced in the oil ring main body differs depending on the size of the window angle _θw of the oil return hole. Further, in this test example, the difference in oil consumption due to the size of the opening width C of the oil return hole was also confirmed.

In this test example, an actual test was conducted on an in-line four-cylinder diesel engine with an oil ring having a cylinder bore diameter of 83.0 mm or 95.0 mm. As shown in Table 6, the oil rings used in Examples 41 to 51 and Comparative Examples 14 to 17 were set under different conditions for each Example and Comparative Example.

In Examples 41 to 51 and Comparative Examples 14 to 17, as in Test Example 2(d), the oil ring main body constituting the oil ring was composed of carbon (C): 0.70% by mass, silicon (Si ): 0.25% by mass, manganese (Mn): 0.30% by mass, phosphorus (P): 0.01% by mass, sulfur (S): 0.01% by mass, chromium (Cr): 8.05% by mass %, and the balance being the composition of iron (Fe) and unavoidable impurities (equivalent to 8Cr steel). When the cylinder bore diameter was 95.0 mm, the oil ring main body was nitrided, and the outer peripheral sliding surface was coated with a 20 μm-thick film of a mixture of chromium nitride and chromium by the PVD method. used things. Further, when the cylinder bore diameter was 83.0 mm, the oil ring main body was not subjected to nitriding treatment, and was directly covered with a PVD film. Also when the cylinder bore diameter was 83.0 mm, a 20 μm-thick PVD film made of a mixture of chromium nitride and chromium was used. Furthermore, the contact width X between the outer peripheral sliding surface 8A and the cylinder 20 shown in FIG. 4A was adjusted to 0.05 to 0.20 mm.
The test conditions other than those described above are the same as those in "Test Example 1(a): Examples 1 to 9 and Comparative Examples 1 to 2", so description thereof is omitted.

In Examples 41 to 51 and Comparative Examples 14 to 17, when the cylinder bore diameter is 95.0 mm, an oil ring with a tension ratio to the cylinder bore diameter of 0.26 N/mm is used, and when the cylinder bore diameter is 83.0 mm. confirmed the oil consumption using an oil ring with a tension ratio of 0.2 N/mm to the cylinder bore diameter. Table 6 shows the oil consumption ratio for each test as a relative ratio to the reference "100" for the oil consumption of Comparative Example 14 or Comparative Example 16.
Table 6 also shows the results of "waviness (μm)".

<Comparison between Examples and Comparative Examples>
As shown in the results of Table 1 (Test Example 1(a): When the rail tip portion has a shape as shown in FIG. 3B and the cylinder bore diameter is 86 mm), Examples 1 to 9 show the amount of waviness. was 6.0 μm or less, which was a good result. Examples 1 to 8, which satisfy the window angle θ _w of 5.33° or less, have a swell amount of 2.0 μm or less, which is a better result, and satisfy the window angle θ _w of 4.0° or less. In Examples 2 to 8, the amount of waviness was 1.0 μm or less, and even better results were obtained.

On the other hand, in Comparative Examples 1 and 2, the amount of undulation was over 6.0 μm, so good results for the oil consumption ratio could not be obtained.

Subsequently, Table 2 (Test Example 1 (b): When the rail tip has a shape as shown in FIG. 3B and the cylinder bore diameter is 70 mm) and Table 3 (Test Example 1 (c): Rail tip 3B and the cylinder bore diameter is 116 mm), similar to the results in Table 1, when the waviness is 6.0 μm or less, the oil consumption ratio is good. Good results were obtained, but in the comparative example in which the amount of waviness exceeded 6.0 μm, good results were not obtained in terms of the oil consumption ratio.

Also, the results of Tables 4 and 5 (Test Example 2 (d): When the rail tip portion has a shape as shown in FIG. 4A and the final shape of various oil rings is measured) As shown in FIG. 13, there is a correlation between the window angle and the amount of waviness, and even if the shape of the oil ring is various, it can be seen that the amount of waviness decreases as the window angle decreases.

Furthermore, the results of Table 6 (Test Example 2 (e): In the case of a test in which the rail tip portion has a shape as shown in FIG. 4A and also includes measurement of the oil consumption ratio), Tables 1 to 1 Similar to the results in Table 3, when the amount of waviness was 6.0 μm or less, a good oil consumption ratio was obtained. no results were obtained.

From the above results, it was found that the oil ring for an internal combustion engine according to the present invention can improve the oil seal performance by setting the waviness amount within a predetermined range. It was also found that by setting the window angle of the oil return hole within a predetermined range, the oil scraped off by the oil ring for the internal combustion engine can be discharged to the oil drain hole, and the oil consumption can be reduced. rice field.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2018-184525) filed on September 28, 2018, the entirety of which is incorporated by reference.

1 Oil ring for internal combustion engine (2-piece oil ring)
2 Oil ring main body 2a Abutment 2b Coil expander accommodating recess 2c Outer peripheral groove 2d Oil return groove 2e Inner peripheral groove 2f Parts other than inner peripheral groove and oil return groove 3 Coil expander 4 Web 5 First rail 6 Second rail 7 Oil return hole 8 (rail) tip 8A Outer peripheral sliding surface (first flat portion, sliding surface)
8B First reduced diameter portion 8C Second reduced diameter portion 8D Second flat portion 8E Third flat portion 8F Recess step 8G Surface treatment layer 10 Piston 11 Oil ring groove 12 Oil drain hole 20 Cylinder 21 (cylinder) inside Wall surface 30 Nitride layer 40 Circle gauge 40A Circle gauge inner peripheral surface 41 Stylus 42 Upper and lower gauge C Opening width of oil return hole D Height of oil return hole opening E Pitch E of oil return hole ₁ In the circumferential direction of the web One end of the pitch E ₂ The other end of the pitch in the circumferential direction of the web F The thickness of the nitride layer G The center point (center of gravity) of the oil ring body 2
a1 Radial width of oil ring main body h1 Axial width of oil ring main body θ _w Window angle of oil return hole

Claims (14)

An oil ring body having a substantially I-shaped cross-sectional shape, and a coil expander arranged on the inner peripheral side of the oil ring body,
The oil ring body includes first and second rails that contact the inner wall surface of the cylinder, and a plurality of rails for causing oil scraped off from the inner wall surface of the cylinder by the first rail and the second rail to flow down to the back surface of the piston. a web with oil return holes,
At least one of a portion on the inner peripheral side of the oil ring body excluding the inner peripheral groove and the oil return groove and a portion on the outer peripheral side of the oil ring body excluding the sliding surface has undulation of 4.0 μm or less. An oil ring for an internal combustion engine characterized by: 2. The oil ring for an internal combustion engine according to claim 1, wherein said waviness is 2.0 [mu]m or less. 3. The oil ring for an internal combustion engine according to claim 1, wherein said oil ring main body is formed by winding an oil ring wire formed with said oil return hole. 2. The oil ring for an internal combustion engine according to claim 1, wherein a window angle θw of said oil return hole in said oil ring body is 8.0° or less. 3. The oil ring for an internal combustion engine according to claim 2, wherein a window angle θw of said oil return hole in said oil ring body is 6.0° or less. The oil ring for an internal combustion engine according to any one of claims 1 to 5, wherein a contact width between said sliding surface and said cylinder is 0.01 to 0.25 mm. Any one of claims 1 to 6, wherein E/C≤3.8, where C is the length of the oil return hole and E is the pitch of the oil return hole in the circumferential direction of the oil ring body. An oil ring for an internal combustion engine according to the above item. The oil ring for an internal combustion engine according to any one of claims 1 to 7, wherein said oil ring main body is made of steel. The oil ring for an internal combustion engine according to any one of claims 1 to 8, wherein the surface of said oil ring main body is subjected to nitriding treatment. The internal combustion engine according to any one of claims 1 to 9, wherein the sliding surface of the oil ring body is coated with at least one of a PVD film, a DLC film, and a resin film as a hard film. for oil ring. The oil ring for an internal combustion engine according to any one of claims 1 to 10, wherein recessed steps are formed at corners of said sliding surface. The tip of the first rail and the tip of the second rail are
a substantially flat first flat portion abutting against the inner wall surface of the cylinder;
a first reduced-diameter portion having a reduced diameter along one of the axial directions of the oil ring body from the first flat portion;
a second flat portion continuous with the first reduced diameter portion;
A third flat portion continuous to the first flat portion via a second diameter-reduced portion whose diameter is reduced from the first flat portion along the other axial direction of the oil ring main body, or directly The oil ring for an internal combustion engine according to any one of claims 1 to 10, comprising: 13. The oil ring for an internal combustion engine according to claim 3, wherein C≧1.0 mm, where C is the length of said oil return hole in the circumferential direction of said oil ring main body. 14. The oil ring for an internal combustion engine according to claim 3, wherein D≧0.3 mm, where D is the height of said oil return hole in the axial direction of said oil ring main body.

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