Oil control ring and method for manufacturing oil control ring

Abstract

This oil control ring comprises a pair of side rails and a spacer expander that is disposed between the pair of side rails. Each of the side rails has an annular rail body portion including an outer peripheral surface, an inner peripheral surface, one side surface, and another side surface. The spacer expander has an annular spacer body portion including: a plurality of ear parts with which the inner peripheral surfaces of the side rails come into contact; and a plurality of rail contact parts which are provided further outward in the radial direction of the spacer expander than the ear parts, and which come into contact with the one side surfaces of the side rails. For at least one of the side rails, in a state in which the one side surface is in contact with the rail contact parts, the other side surface extends orthogonal to the axial direction of the spacer expander, and the inner peripheral surface is in contact with the ear parts, the value L / h1 is 11 / 20 to 15 / 20, said value being obtained by dividing the height L from the contact point between the inner peripheral surface and the ear parts to the other side surface by the axial width dimension h1 of the rail body portion.

Description

Oil Control Ring and Method for Manufacturing Oil Control Ring

[0001] The present disclosure relates to an oil control ring and a method for manufacturing an oil control ring.

[0002] Conventionally, as an oil control ring to be fitted into an oil ring groove of a piston of an internal combustion engine, a three-piece oil control ring including a pair of side rails and a spacer expander disposed between the pair of side rails is known (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2020-204349

[0004] As a measure for reducing oil consumption when using a three-piece oil control ring, for example, using a side rail with a devised cross-sectional shape of the outer circumferential surface to increase the surface pressure against the inner wall surface of a cylinder may improve oil scraping performance. However, when the cross-sectional shape of the outer circumferential surface is axially asymmetric, there are conceivable disadvantages such as the risk of incorrect assembly reversed in the axial direction, or an increase in friction caused by increased surface pressure. Therefore, there remains room for improvement to reduce oil consumption while suppressing these disadvantages.

[0005] An object of the present disclosure is to provide an oil control ring and a method for manufacturing an oil control ring that can reduce oil consumption by improving the side seal performance of side rails.

[0006] In order to solve the above problem, the present inventor has conducted intensive studies. As a result, the present inventor found that improving the side seal performance of the side rails to reduce oil consumption can suppress the above disadvantages caused by the cross-sectional shape of the outer circumferential surface of the side rail. The inventor further found that optimizing the moment acting on the side rail in a cross section perpendicular to the circumferential direction by utilizing the force generated when the lug portions of the spacer expander come into contact with the inner circumferential surface of the side rail can improve the side seal performance of the side rail.

[0007] An oil control ring according to one aspect of the present disclosure comprises a pair of side rails and a spacer expander disposed between the pair of side rails, wherein the side rails have an annular rail body portion including an outer circumferential surface, an inner circumferential surface, one side surface and the other side surface, and the spacer expander has an annular spacer body portion including a plurality of lugs that contact the inner circumferential surface of the side rail, and a plurality of rail contact portions provided radially outward of the spacer expander from the lugs and in contact with one side surface of the side rail, wherein for at least one of the side rails, one side surface is in contact with the rail contact portion, the other side surface extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lugs, and the value L / h1 obtained by dividing the height L from the contact point between the inner circumferential surface and the lugs to the other side surface by the axial width dimension h1 of the rail body portion is 11 / 20 or more and 15 / 20 or less.

[0008] When an oil control ring according to one aspect of this disclosure is incorporated into the oil ring groove of a piston of an internal combustion engine, one side of the side rail contacts the rail contact portion, and the other side of the side rail contacts the oil ring groove, thereby creating airtightness between one side of the side rail and the rail contact portion, and between the other side of the side rail and the oil ring groove, and thus providing side sealing performance. The lugs of the spacer expander contact the inner circumferential surface of the side rail and the force pushing against the inner circumferential surface causes a moment in the cross-section perpendicular to the circumferential direction to act on the side rail. The inventors have focused on the fact that the above-mentioned airtightness may change in accordance with this moment. As a result of diligent research, the inventors have found that by configuring the side rail so that, when one side surface of the side rail is in contact with the rail contact portion, the other side surface of the side rail extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lug portion, and the height L from the contact point between the inner circumferential surface and the lug portion to the other side surface is divided by the axial width dimension h1 of the rail body, the value L / h1 is 11 / 20 or more and 15 / 20 or less, the moment can be adjusted to be advantageous in reducing oil consumption. Therefore, according to one aspect of the present disclosure, it is possible to reduce oil consumption by improving the side sealing performance of the side rail.

[0009] In one embodiment, the side rail may have two sides that are substantially parallel, and the spacer expander may have a rail contact portion that contacts one side that is perpendicular to the axial direction of the spacer body. In this case, when the oil control ring is incorporated into the oil ring groove of the piston of the internal combustion engine, the contact area between one side of the side rail and the rail contact portion, and between the other side and the oil ring groove, tends to increase. Therefore, the side sealing performance is more easily achieved.

[0010] A method for manufacturing an oil control ring according to another aspect of the present disclosure is a method for manufacturing an oil control ring comprising a pair of side rails and a spacer expander disposed between the pair of side rails, comprising a configuration step of configuring a side rail having an annular rail body portion including an outer circumferential surface, an inner circumferential surface, one side surface and the other side surface, and a spacer expander having an annular spacer body portion including a plurality of lugs that the inner circumferential surface of the side rail contacts, and a plurality of rail contact portions provided radially outward of the spacer expander from the lugs and contacting one side surface of the side rail, wherein in the configuration step, for at least one of the side rails, one side surface is in contact with the rail contact portion, the other side surface extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lugs, and the value L / h1 obtained by dividing the height L from the contact point between the inner circumferential surface and the lugs to the other side surface by the axial width dimension h1 of the rail body portion is 11 / 20 or more and 15 / 20 or less.

[0011] In a method for manufacturing an oil control ring according to another aspect of the present disclosure, in the configuration step, the side rail and spacer expander are configured such that, for at least one of the side rails, one side surface is in contact with the rail contact portion, the other side surface extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lug portion, and the value L / h1 obtained by dividing the height L from the contact point between the inner circumferential surface and the lug portion to the other side surface by the axial width dimension h1 of the rail body portion is 11 / 20 or more and 15 / 20 or less. Here, when the oil control ring is incorporated into the oil ring groove of the piston of an internal combustion engine, one side surface of the side rail is in contact with the rail contact portion, and the other side surface of the side rail is in contact with the oil ring groove, thereby creating airtightness between one side surface of the side rail and the rail contact portion, and between the other side surface and the oil ring groove, and thus exhibiting side sealing performance. The lug portion of the spacer expander contacts the inner circumferential surface of the side rail and the force pushing against the inner circumferential surface causes a moment in the cross section perpendicular to the circumferential direction to act on the side rail. The inventors focused on the fact that the above-mentioned airtightness can change in accordance with this moment. As a result of diligent research, the inventors found that by configuring the side rail and spacer expander as described in the above configuration steps, the moment can be adjusted to one that is advantageous in reducing oil consumption. Therefore, according to the manufacturing method of the oil control ring according to other embodiments of this disclosure, it is possible to reduce oil consumption by improving the side sealing performance of the side rail.

[0012] In one embodiment, during the configuration step, the height X from the top of the lug to the contact point can be determined by observing the lug from the radially outer side of the spacer expander, and the height L can be determined by adding the height C from the top to the extension line of the other side to the height X. In this case, the height X can be easily determined by observing the lug from the radially outer side of the spacer expander.

[0013] In one embodiment, during the configuration step, the height Y from the rail contact portion to the contact point can be determined by observing the lugs from the radially outer side of the spacer expander, and the height L can be determined by subtracting the height Y from the axial width dimension h1 of the rail body. In this case, the height Y can be easily determined by observing the lugs from the radially outer side of the spacer expander.

[0014] According to various aspects of this disclosure, it is possible to reduce oil consumption by improving the side sealing performance of the side rails.

[0015] Figure 1 is a schematic cross-sectional view illustrating an oil control ring according to an embodiment. Figure 2 is a schematic plan view illustrating the spacer expander of Figure 1. Figure 3 is an enlarged perspective view of the area enclosed by the dashed line in Figure 2. Figure 4(a) is a diagram illustrating the moment generated by the oil control ring according to an embodiment. Figure 4(b) is a diagram illustrating the moment generated by the oil control ring according to the first comparative example. Figure 4(c) is a diagram illustrating the moment generated by the oil control ring according to the second comparative example. Figure 5 is a schematic cross-sectional view illustrating an example of an oil control ring. Figure 6 is a schematic diagram illustrating an example of a method for manufacturing an oil control ring. Figure 7 is a diagram illustrating an example of a method for observing the lugs. Figure 8 is a schematic cross-sectional view illustrating another example of an oil control ring. Figure 9 is a diagram illustrating another example of a method for observing the lugs. Figure 10 is a diagram illustrating the relationship between the value L / h1 and the LOC ratio.

[0016] Embodiments of this disclosure will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0017] Figure 1 is a schematic cross-sectional view illustrating an oil control ring according to an embodiment. Figure 2 is a schematic plan view illustrating the spacer expander of Figure 1. As shown in Figures 1 and 2, the oil control ring 1 is a piston ring used by being fitted into the oil ring groove 51 of the piston 50 of an internal combustion engine. The oil control ring 1 is a three-piece oil control ring comprising a pair of side rails 2 and 3 and a spacer expander 4 positioned between the pair of side rails 2 and 3.

[0018] The internal combustion engine is, for example, a four-stroke reciprocating engine. In Figure 1, the axial directions of the piston 50 and the cylinder bore 60 are assumed to coincide. In Figure 1, the upper side of the paper corresponds to the top dead center side of the piston 50 (the combustion chamber side of the internal combustion engine), and the lower side of the paper corresponds to the bottom dead center side of the piston 50 (the crankcase side of the internal combustion engine). The oil ring groove 51 is formed on the outer circumferential surface of the piston 50 so as to be recessed radially inward to a depth that can accommodate the oil control ring 1. The upper surface 51a and lower surface 51b of the oil ring groove 51 are, for example, planes that extend substantially perpendicular to the axial direction of the piston 50.

[0019] With respect to the side rails 2 and 3, spacer expander 4, piston 50, and cylinder bore 60, when assembled as shown in Figure 1, the "axial direction" corresponds to the direction "A" in Figure 1, the "radial outward direction" corresponds to the direction "OUT" in Figure 1, and the "radial inward direction" corresponds to the direction "IN" in Figure 1.

[0020] The side rails 2 and 3 each have annular rail body portions 20 and 30, respectively. The term "annular" here is not limited to a closed circle. The side rails 2 and 3 may also have joint portions. The material of the side rails 2 and 3 may be alloy steel such as steel with added Ni.

[0021] The rail body portion 20 includes an outer circumferential surface 21, an inner circumferential surface 22, a side surface 23 (one side surface), and a side surface 24 (the other side surface). The rail body portion 30 includes an outer circumferential surface 31, an inner circumferential surface 32, a side surface 33 (one side surface), and a side surface 34 (the other side surface). The cross-sectional shape of the side rails 2 and 3 is, for example, an arc shape in which the outer circumferential surfaces 21, 31 and the inner circumferential surfaces 22, 32 are curved symmetrically vertically.

[0022] The outer circumferential surfaces 21 and 31 are surfaces that contact the inner surface 61 of the cylinder bore 60. The side surfaces 23 and 33 are one axial surface of the rail body 20 and 30, and are the surface on the spacer expander 4 side. The side surfaces 24 and 34 are the other axial surface of the rail body 20 and 30, and are the surface on the oil ring groove 51 side.

[0023] In the side rail 2, the sides 23 and 24 may be substantially parallel. The sides 23 and 24 may extend substantially perpendicular to the axial direction of the side rail 2 (extending substantially parallel to the radial direction). Regarding the width (axial dimension) between the sides 23 and 24, when the rail body portion 20 is formed in an annular shape, a small change in wall thickness occurs between the inner and outer sides in the radial direction, and the axial width on the inner side may be slightly larger than the width on the outer side. Here, even with such a difference in width, it is assumed that the sides extend substantially perpendicular to the axial direction of the side rail 2 (extending substantially parallel to the radial direction).

[0024] In the side rail 3, the sides 33 and 34 may be substantially parallel. The sides 33 and 34 may extend substantially perpendicular to the axial direction of the side rail 3 (extending substantially parallel to the radial direction). Regarding the width between the sides 23 and 24, similar to the sides 23 and 24 described above, even if a difference in width occurs when forming the rail body 30 in an annular shape, it shall be assumed that the width extends substantially perpendicular to the axial direction of the side rail 2 (extending substantially parallel to the radial direction).

[0025] The spacer expander 4 has a joint portion 4c formed by, for example, two end faces 4a and 4b. The material of the spacer expander 4 may be an alloy steel such as stainless steel. The spacer expander 4 has an annular spacer body portion 40.

[0026] The spacer body 40 has a plurality of lugs 41, including contact surfaces 41a that contact the inner circumferential surfaces 22 and 32 of the side rails 2 and 3. The spacer body 40 also has a rail-facing surface 42 formed adjacent to the lugs 41, and a plurality of rail contact portions 43 that abut against the side surfaces 23 and 33 of the side rails 2 and 3, respectively.

[0027] The rail contact portion 43 is provided radially outward from the spacer body portion 40 compared to the lug portion 41. The rail contact portion 43 protrudes axially from the rail-facing surface 42. The side surfaces 23 and 33 face the rail-facing surface 42 and abut the rail contact portion 43, respectively, when the side rails 2 and 3 are combined with the spacer expander 4 and the side surfaces 24 and 34 extend perpendicular to the axial direction of the spacer body portion 40 (extending parallel to the radial direction).

[0028] The radial length of the rail contact portion 43 is, for example, less than half the radial length of the side rails 2 and 3. The rail contact portion 43 contacts the side surfaces 23 and 33 outside the radial center of the side rails 2 and 3.

[0029] In the spacer expander 4, the rail contact portion 43 that contacts each of the side surfaces 23 and 33 includes a surface perpendicular to the axial direction of the spacer body 40. Therefore, when each of the side surfaces 23 and 33 comes into close contact with the rail contact portion 43, the orientation of the side rails 2 and 3 becomes perpendicular to the axial direction of the spacer body 40. The side surfaces 24 and 34 also extend perpendicular to the axial direction of the spacer body 40.

[0030] Figure 3 is an enlarged perspective view of the area enclosed by the dashed line in Figure 2. As shown in Figures 1 and 3, the lugs 41 are formed higher than the rail contact portion 43 relative to the central portion in a cross-sectional view of the spacer body 40. The lugs 41 may be formed such that the radially inner ends of the spacer body 40 protrude in one or the other axial direction of the spacer expander 4.

[0031] The contact surface 41a of the ear portion 41 is the radially outer side surface of the ear portion 41. When viewed from the radially outer side, the contact surface 41a is a substantially band-shaped plane that curves along the shape of the ear portion 41 with a width corresponding to the thickness of the ear portion 41, for example. The contact surface 41a is a surface that is exposed when the ear portion 41 is formed, and does not need to have protrusions or recesses. When viewed from the circumferential direction of the spacer body portion 40, the contact surface 41a is an inclined surface that is inclined at a predetermined inclination angle θ with respect to the axial direction of the spacer expander 4.

[0032] The side sealing performance of side rails 2 and 3 will be described. Side sealing performance can be achieved in either side rail 2 or 3. Depending on the stroke state of the internal combustion engine, the reciprocating motion of the piston 50, etc., the side sealing performance achieved by one side rail 2 or 3 may exceed the performance achieved by the other. However, since side sealing performance is achieved by the same mechanism in either side rail 2 or 3, the following description will focus on the case where side rail 3 is sandwiched between the rail contact portion 43 and the oil ring groove 51, as a representative example of side rails 2 and 3.

[0033] Figure 4(a) is a diagram illustrating the moment generated by the oil control ring according to the embodiment. As an example, as shown in Figures 1 and 4(a), when the oil control ring 1, in which side rails 2 and 3 are combined with a spacer expander 4, is inserted into the cylinder bore 60, the tension of the spacer expander 4 causes the inner circumferential surface 32 of the side rail 3 to abut against the contact surface 41a of the lug portion 41. When the inner circumferential surface 32 abuts against the contact surface 41a, a force is applied to the side rail 3 radially outward and a force is applied to the lower surface 51b of the oil ring groove 51. A force from the contact surface 41a is applied to the side rail 3 such that at least the inner circumferential surface 32 side is in contact with the lower surface 51b of the oil ring groove 51. Then, as the side rail 3 is sandwiched between the rail contact portion 43 and the oil ring groove 51, the entire side surface 34 comes into contact with the lower surface 51b of the oil ring groove 51.

[0034] Here, for example, if a downward force is applied to the outer circumferential surface 31 due to sliding with the inner surface 61 of the cylinder bore 60 (not shown), the side rail 3 is subjected to forces from both the outer circumferential surface 31 and the inner circumferential surface 32 toward the lower surface 51b of the oil ring groove 51. Therefore, the side sealing performance is easily achieved.

[0035] However, if an upward force is applied to the outer circumferential surface 31 due to sliding with the inner surface 61 of the cylinder bore 60, for example, a moment M acts on the side rail 3 within a cross section perpendicular to the circumferential direction, as shown in Figure 4(a). Due to moment M, the outer circumferential surface 31 of the side rail 3 tries to move away from the lower surface 51b of the oil ring groove 51, while the inner circumferential surface 32 of the side rail 3 is pressed against the lower surface 51b of the oil ring groove 51. In other words, it can be considered that moment M affects the quality of the side sealing performance of the side rail 3.

[0036] Therefore, the oil control ring 1 is configured as shown in Figure 5, for example (configuration step for manufacturing the oil control ring). With respect to the side rail 3, the side surface 33 is in contact with the rail contact portion 43, the side surface 34 extends perpendicular to the axial direction of the spacer expander 4, and the inner circumferential surface 32 is in contact with the lug portion 41. The value L / h1 obtained by dividing the height L from the contact point 41b between the inner circumferential surface 32 and the lug portion 41 to the side surface 34 by the axial width dimension h1 of the rail body portion 30 is configured to be 11 / 20 or more and 15 / 20 or less. In other words, the oil control ring 1 is configured such that the cross-sectional shape of the inner circumferential surface 32 and the inclination angle θ of the contact surface 41a are such that the value L / h1 is 11 / 20 or more and 15 / 20 or less. The oil control ring 1 may also be configured such that the value L / h1 is 11 / 20 or more and 13 / 20 or less.

[0037] The height L can be determined, for example, as shown in Figures 5 to 7, by observing the lugs 41 from the radially outer side of the spacer expander 4 to find the height X from the top 41t of the lugs 41 to the contact point 41b, and then adding the height C from the top 41t to the extension line of the side surface 34 to the height X (configuration step). To observe the lugs 41, for example, a microscope is used to image the contact surface 41a through the rail contact portion 43, parallel to the radial direction of the spacer expander 4.

[0038] Contact marks 41c are generated on the contact surface 41a within a certain range due to contact with the inner circumferential surface 32 of the side rail 3. The contact marks 41c can be formed by performing a predetermined test run in order to determine the height L in the configuration step. The predetermined test run may be performed with the oil control ring 1, in which the side rails 2 and 3 are combined with the spacer expander 4, fitted into the oil ring groove 51, and its piston 50 inserted into the cylinder bore 60 or a test cylinder fixture.

[0039] The contact marks 41c are not always parallel to the direction perpendicular to the axial direction of the spacer expander 4, but rather oscillate within a cross-section perpendicular to the circumferential direction, resulting in a certain range of spread. Therefore, assuming a situation where the side rail 3 is parallel to the direction perpendicular to the axial direction of the spacer expander 4, a predetermined position within the contact marks 41c may be determined as the contact point 41b. In the example of Figure 7, the contact marks 41c can be assumed to be an elliptical region with a major axis in the circumferential direction, as shown by the dashed line. In this case, the position of the major axis of this elliptical region can be taken as the contact point 41b, and the length of the leg of the normal drawn from the top 41t to the major axis can be used as the height X. This predetermined position within the contact marks 41c corresponds to the orientation of the side rail 3 where the side surface 33 is in contact with the rail contact portion 43, the side surface 34 extends perpendicular to the axial direction of the spacer expander 4, and the inner circumferential surface 32 is in contact with the lug portion 41.

[0040] In the configuration step, for example, an oil control ring 1 is prototyped such that the value L / h1 is 11 / 20 or more and 15 / 20 or less. A test run is performed on the prototype oil control ring 1, and the value L / h1 is calculated based on the observations described above to confirm whether the value L / h1 is 11 / 20 or more and 15 / 20 or less. Based on this confirmation result, the oil control ring 1 can be constructed using the specifications of the oil control ring 1 that has been confirmed to have a value L / h1 of 11 / 20 or more and 15 / 20 or less.

[0041] Incidentally, at least the inner circumferential surface 32 side of the side surface 34 is in contact with the lower surface 51b of the oil ring groove 51. The lower surface 51b of the oil ring groove 51 is a surface perpendicular to the axial direction of the piston 50 in the portion that contacts the side surface 34. Therefore, when the oil control ring 1, in which the side rails 2 and 3 are combined with the spacer expander 4, is inserted into the cylinder bore 60, the side surface 34 extends perpendicular to the axial direction of the spacer expander 4 and is perpendicular to the axial direction of the piston 50. In this case, the height L can also be the distance from the contact point 41b between the inner circumferential surface 32 and the lug portion 41 to the lower surface 51b of the oil ring groove 51. The height C can also be the distance from the top portion 41t to the lower surface 51b of the oil ring groove 51.

[0042] As an alternative example, the height L may be determined by observing the lugs 41 from the radially outer side of the spacer expander 4 to find the height Y from the rail contact portion 43 to the contact point 41b, and then subtracting the height Y from the axial width dimension h1 of the rail body portion 30, as shown in Figures 8 and 9 (configuration step). To observe the lugs 41, the contact surface 41a is imaged through the rail contact portion 43 in the same manner as in the example of Figure 6 described above.

[0043] The position of the contact point 41b on the contact mark 41c may be determined as the position of the major axis of the elliptical region in the same manner as in the example of FIG. 7. In the example of FIG. 9, the position of the major axis of the elliptical region of the contact mark 41c is taken as the contact point 41b, and the length of the foot of the normal drawn from the top 43t of the rail contact portion 43 to the major axis can be used as the height Y. When the entire rail contact portion 43 is flat, the top 43t of the rail contact portion 43 may be at any position of the rail contact portion 43. Alternatively, when the rail contact portion 43 is slightly convex and both circumferential end portions are slightly lower, the top 43t of the rail contact portion 43 may be the position of the surface of the rail contact portion 43 that is orthogonal to the axial direction of the spacer main body portion 40 and contacts the side surface 33.

[0044] When the value L / h1 is within the above range, the moment M acting on the side rail 3 in the cross section orthogonal to the circumferential direction is considered to improve the side seal performance.

[0045] Specifically, first, as Comparative Example 1, among the forces applied from the contact surface 41a of the ear portion 41 to the inner peripheral surface 32 of the side rail 3, the component force directed toward the lower surface 51b of the oil ring groove 51 is smaller in the case of FIG. 4(b) where the value L / h1 is less than 11 / 20 than in the case of FIG. 4(a) where the value L / h1 is within the above range. It is considered that the component force directed toward the lower surface 51b of the oil ring groove 51 does not reach the force required to sufficiently press the inner peripheral surface 32 against the lower surface 51b of the oil ring groove 51, so that the side seal performance is likely to deteriorate. In addition, the moment M is smaller than that in the case of FIG. 4(a), so that in the side rail 3, the force that tends to separate the outer peripheral surface 31 side from the lower surface 51b of the oil ring groove 51 is more likely to be dominant than the force that presses the inner peripheral surface 32 side against the lower surface 51b of the oil ring groove 51. This is also considered to easily lower the side seal performance.

[0046] Next, as Comparative Example 2, of the force applied from the contact surface 41a of the lug portion 41 to the inner circumferential surface 32 of the side rail 3, the component force toward the lower surface 51b of the oil ring groove 51 is excessive in the case of Figure 4(c) where the value L / h1 exceeds 15 / 20, compared to the case of Figure 4(a) where the value L / h1 is within the above range. In this case, the force pressing the inner circumferential surface 32 against the lower surface 51b of the oil ring groove 51 is too strong, which may hinder the behavior of the side rail 3. Furthermore, the excess force exceeding the force required to sufficiently press the inner circumferential surface 32 against the lower surface 51b of the oil ring groove 51 results in a larger moment M compared to the case of Figure 4(a). This moment M may cause a force that tries to move the outer circumferential surface 31 away from the lower surface 51b of the oil ring groove 51, for example, with the point where the rail contact portion 43 contacts the side surface 33 as the fulcrum.

[0047] In contrast to these comparative examples 1 and 2, in the case of Figure 4(a) where the value L / h1 is within the above range, it is considered that the component force directed toward the lower surface 51b of the oil ring groove 51 causes the inner circumferential surface 32 to be pressed against the lower surface 51b of the oil ring groove 51, while the outer circumferential surface 31 side becomes less likely to separate from the lower surface 51b of the oil ring groove 51.

[0048] As explained above, when incorporated into an oil ring groove 51 of a piston 50 of an internal combustion engine, the side surface 33 of the side rail 3 is in contact with the rail contact portion 43, and the side surface 34 of the side rail 3 is in contact with the oil ring groove 51. This creates airtightness between the side surface 33 of the side rail 3 and the rail contact portion 43, as well as between the side surface 34 and the oil ring groove 51, thereby exhibiting side sealing performance. A moment M in a cross section perpendicular to the circumferential direction acts on the side rail 3 by the pressing force generated when the ear portion 41 of the spacer expander 4 contacts the inner peripheral surface 32 of the side rail 3. Focusing on the fact that the above-mentioned airtightness can change in accordance with this moment M, in a state where the side surface 33 of the side rail 3 is in contact with the rail contact portion 43, the side surface 34 of the side rail 3 extends orthogonally to the axial direction of the spacer expander 4, and the inner peripheral surface 32 is in contact with the ear portion 41, a value obtained by dividing the height L from the contact point 41b between the inner peripheral surface 32 and the ear portion 41 to the side surface 34 by the axial width dimension h1 of the rail main body portion 30, that is L / h1, is configured to be not less than 11 / 20 and not more than 15 / 20. It has been found that this allows the moment M to be adjusted to a value advantageous for reducing oil consumption. Therefore, according to the oil control ring 1 and the method for manufacturing an oil control ring according to the present embodiment, it is possible to reduce oil consumption by improving the side sealing performance of the side rail 3.

[0049] In the oil control ring 1, in the side rail 3, the side surface 33 and the side surface 34 are substantially parallel, and in the spacer expander 4, the rail contact portion 43 that contacts the side surface 33 is a surface orthogonal to the axial direction of the spacer main body portion 40. Accordingly, when the oil control ring 1 is incorporated into the oil ring groove 51 of the piston 50 of an internal combustion engine, the contact area between the side surface 33 of the side rail 3 and the rail contact portion 43, as well as the contact area between the side surface 34 and the oil ring groove 51, is easily increased, and the side sealing performance is easily exhibited.

[0050] In the manufacturing method of the oil control ring 1, in the configuration step, the height X from the top 41t of the lug 41 to the contact point 41b is determined by observing the lug 41 from the radially outer side of the spacer expander 4, and the height L is determined by adding the height C from the top 41t to the extension line of the side surface 34 to the height X. This makes it possible to easily determine the height X by observing the lug 41 from the radially outer side of the spacer expander 4.

[0051] In the manufacturing method of the oil control ring 1, in the configuration step, the height Y from the rail contact portion 43 to the contact point 41b is determined by observing the lug portion 41 from the radially outer side of the spacer expander 4, and the height L is determined by subtracting the height Y from the axial width dimension h1 of the rail body portion 30. This makes it easy to determine the height Y by observing the lug portion 41 from the radially outer side of the spacer expander 4.

[0052] Although embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments described above.

[0053] In the above embodiment, the side sealing performance was described using the side rail 3 as a representative example, but the side sealing performance for the side rail 2 is similar. It is sufficient that at least one of the side rails 2 or 3 is configured such that the value L / h1 is 11 / 20 or more and 15 / 20 or less.

[0054] In the above embodiment, the cross-sectional shape of the side rails 2 and 3 was an arc shape in which the outer circumferential surfaces 21 and 31 and the inner circumferential surfaces 22 and 32 were curved symmetrically vertically, but it is not limited to this. The cross-sectional shape of the outer circumferential surface and the cross-sectional shape of the inner circumferential surface of the side rail may be different from those of the side rails 2 and 3 in this embodiment. The cross-sectional shape of the outer circumferential surface and the cross-sectional shape of the inner circumferential surface of the side rail may be asymmetrical vertically, or may be a shape other than an arc shape, such as a tapered cross-section.

[0055] In the above embodiment, all ear portions 41 were substantially the same shape, but they do not necessarily have to be substantially the same shape.

[0056] In the above embodiment, the sides 23, 33 and sides 24, 34 of the side rails 2, 3 were substantially parallel, but they do not necessarily have to be parallel.

[0057] In the configuration steps of the above embodiment, the heights X and Y were determined by observing the lugs 41 from the radially outer side of the spacer expander 4, but the method is not limited to this. The contact point may be determined by simulation or the like, and the height L may be calculated.

[0058] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited to these examples.

[0059] (Examples) As shown in Table 1, the oil control rings 1 of Examples 1 to 11 were manufactured by following the procedure below. The contact surface 41a of the lug portion 41 was formed to be inclined at an inclination angle θ, and side rails 2 and 3 were prepared with an axial width dimension of h1 and a radial thickness of 1.7 mm for the rail body portions 20 and 30. The oil control ring 1, in which the side rails 2 and 3 were combined with the spacer expander 4, was fitted into the oil ring groove 51, and a predetermined test run was performed with the piston 50 inserted into the cylinder bore 60 or a test cylinder jig. The predetermined test run conditions were as described in the test run conditions below. After that, the height X from the top 41t of the lug portion 41 to the contact point 41b was determined by observing the lug portion 41 from the radial outside of the spacer expander 4, and the height L was determined by adding the height C from the top 41t to the extension line of the side surface 34 to the height X, and the value L / h1 was calculated. In the oil control rings 1 of Examples 1 to 11, it was confirmed that the value L / h1 was 11 / 20 or greater and 15 / 20 or less.

[0060] (Comparative Examples) As shown in Table 1, oil control rings for Comparative Examples 1 to 6 were manufactured. Except for the changes in the values ​​shown in Table 1, they were the same as oil control ring 1 of the Examples. For the oil control rings of Comparative Examples 1 to 6, it was confirmed that the value L / h1 was less than 11 / 20 or greater than 15 / 20.

[0061]

[0062] (Test Operation Conditions) Oil consumption (LOC) was evaluated in a real-world test using an in-line four-cylinder gasoline engine with the oil control rings of Examples 1 to 11 and Comparative Examples 1 to 6 installed in each cylinder. The operating conditions were 4000 rpm and a load of 200 N. To compare oil consumption performance, the tension of the spacer expander 4 was set to 20 N. The evaluation results of oil consumption are shown in Figure 10. The LOC ratio is the value expressed as a ratio of the LOC amounts of the other examples and comparative examples when the LOC amount of Comparative Example 1 is set to 1.0.

[0063] As shown in the evaluation results in Figure 10, the oil control ring 1 of Examples 1 to 11 had an LOC ratio of 0.85 or less, demonstrating a reduction in oil consumption compared to Comparative Examples 1 to 6. In particular, Examples 2 to 4 and 6, where the value L / h1 was 11 / 20 or more and 13 / 20 or less, had an LOC ratio of 0.76 or less, demonstrating an even greater reduction in oil consumption.

[0064] 1... Oil control ring, 2, 3... Side rails, 4... Spacer expander, 20, 30... Rail body, 21, 31... Outer circumference, 22, 32... Inner circumference, 23, 33... Side (one side), 24, 34... Side (other side), 40... Spacer body, 41... Ear, 41b... Contact point, 41c... Contact mark, 41t... Top, 43... Rail contact area.

Claims

1. An oil control ring comprising a pair of side rails and a spacer expander disposed between the pair of side rails, wherein the side rails have an annular rail body portion including an outer circumferential surface, an inner circumferential surface, one side surface and the other side surface, and the spacer expander has an annular spacer body portion including a plurality of lugs that contact the inner circumferential surface of the side rail, and a plurality of rail contact portions provided radially outward of the spacer expander from the lugs and in contact with the one side surface of the side rail, and in a state in which, for at least one of the side rails, the one side surface is in contact with the rail contact portion, the other side surface extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lugs, the value L / h1 obtained by dividing the height L from the contact point between the inner circumferential surface and the lugs to the other side surface by the axial width dimension h1 of the rail body portion is 11 / 20 or more and 15 / 20 or less.

2. The oil control ring according to claim 1, wherein in the side rail, one side and the other side are substantially parallel, and in the spacer expander, the rail contact portion that contacts the one side is a surface perpendicular to the axial direction of the spacer body.

3. A method for manufacturing an oil control ring comprising a pair of side rails and a spacer expander disposed between the pair of side rails, comprising the steps of constructing the side rails having an annular rail body portion including an outer circumferential surface, an inner circumferential surface, one side surface and the other side surface, and the spacer expander having an annular spacer body portion including a plurality of lugs that contact the inner circumferential surface of the side rail, and a plurality of rail contact portions provided radially outward of the spacer expander from the lugs and in contact with the one side surface of the side rail, A method for manufacturing an oil control ring, comprising the above configuration step, wherein, for at least one of the side rails, one side surface is in contact with the rail contact portion, the other side surface extends perpendicular to the axial direction of the spacer expander, and the inner circumferential surface is in contact with the lug portion, and the value L / h1 obtained by dividing the height L from the contact point between the inner circumferential surface and the lug portion to the other side surface by the axial width dimension h1 of the rail body portion is 11 / 20 or more and 15 / 20 or less.

4. The method for manufacturing an oil control ring according to claim 3, wherein in the configuration step, the height X from the top of the lug to the contact point is determined by observing the lug from the radially outer side of the spacer expander, and the height L is determined by adding the height C from the top to the extension line of the other side to the height X.

5. The method for manufacturing an oil control ring according to claim 3, wherein in the configuration step, the height Y from the rail contact portion to the contact point is determined by observing the lug portion from the radially outer side of the spacer expander, and the height L is determined by subtracting the height Y from the axial width dimension h1 of the rail body portion.

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