oil control ring

Abstract

An oil control ring has a ring-shaped main body portion having an inner peripheral surface and an outer peripheral surface, and one side surface and another side surface which are substantially orthogonal to the inner peripheral surface, and a spiral expander fitted along the inner peripheral surface. In the oil control ring, the main body portion has a pair of ring-shaped first and second track portions and a column portion connecting the first and second track portions. The outer peripheral surfaces of the first and second track portions have protruding surfaces which protrude convexly toward respective radial outer sides. The protruding surfaces are circular arc surfaces having a radius of curvature of 0.30 mm or less in a sliding contact region including an apex which is a radially outermost point of the first or second track portion.

Description

Technical Field

[0001] This disclosure relates to oil control rings used in internal combustion engines. Background Technology

[0002] As an oil control ring used in internal combustion engines such as automobiles, for example, Patent Document 1 describes a two-piece oil ring, which is configured such that the outer peripheral surfaces of the upper and lower track portions have a sliding surface that slides on the inner peripheral surface of the cylinder and a conical surface disposed on the combustion chamber side (the upper surface side of the oil ring) of the sliding surface and gradually narrows toward the combustion chamber side.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 9-144881 Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] In the aforementioned conventional oil rings, to reduce oil consumption, a conical surface is incorporated to reduce the area of ​​the sliding surface that slides on the inner circumference of the cylinder. This increases the contact pressure between the sliding surface and the inner circumference of the cylinder, promoting oil scraping during piston descent. During piston ascent, the sliding surface crosses the oil film formed between the conical surface and the inner circumference of the cylinder, thereby suppressing oil splashing. However, in the aforementioned conventional oil rings, the cross-sectional shape of the sliding contact area, including the portion sliding against the inner circumference of the cylinder and its vicinity, is asymmetrical, requiring management of both sides, thus impacting manufacturing costs.

[0006] The purpose of this disclosure is to provide an oil control ring that simplifies the cross-sectional shape of the outer peripheral surfaces of the first and second track sections and reduces oil consumption.

[0007] Methods for solving problems

[0008] To address the aforementioned issues, the inventors conducted repeated and in-depth research. As a result, they discovered a structure on the outer peripheral surface of the oil control ring that enables a reduction in oil consumption and achieves vertical symmetry, at least in the sliding contact area.

[0009] One aspect of the oil control ring disclosed herein comprises: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and another side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, the outer circumferential surface of the first track portion and the second track portion having a protruding surface with a cross-sectional shape that convexly protrudes towards their respective radially outward, the protruding surface being an arc surface with a radius of curvature of less than 0.30 mm in a sliding contact area including a vertex, the vertex being the radially outermost point of the first track portion or the second track portion.

[0010] In one aspect of the oil control ring disclosed herein, the outer peripheral surfaces of the first and second track portions have protruding surfaces with a cross-sectional shape that convexly protrudes radially outward. The protruding surface is an arcuate surface with a radius of curvature of 0.30 mm or less in the sliding contact region including its vertex, which is the outermost radial point of the first or second track portion. With this structure, at least a portion of the protruding surface forming the arcuate surface forms a sliding contact region symmetrical axially with respect to the vertex. Thus, by forming a cross-sectional shape that is symmetrical vertically at least in the sliding contact region, the cross-sectional shape is simplified. The sliding contact region allows for sufficient oil scraping. Therefore, oil consumption can be reduced. Thus, the cross-sectional shape of the outer peripheral surfaces of the first and second track portions can be simplified, and oil consumption can be reduced.

[0011] Another embodiment of the oil control ring disclosed herein comprises: an annular body portion having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the body portion has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, the outer circumferential surface of the first track portion and the second track portion having a protruding surface with a cross-sectional shape that convexly protrudes towards their respective radially outward, at least a portion of the protruding surface being located on an imaginary convex surface passing through a vertex and a pair of points, the vertex being the radially outermost point of the first track portion or the second track portion, the pair of points being 0.05 mm away from the vertex axially to both sides and located radially inward with a predetermined drop of 0.0045 mm or more.

[0012] In another embodiment of the oil control ring disclosed herein, the outer peripheral surfaces of the first and second track portions have protruding surfaces with a cross-sectional shape that convexly protrudes radially outward from their respective sides. At least a portion of the protruding surface lies on an imaginary convex surface passing through a vertex and a pair of points, which are respectively 0.05 mm away from the vertex on both sides axially and located radially inward with a predetermined drop of 0.0045 mm or more. According to this structure, at least a portion of the protruding surface along the imaginary convex surface forms a sliding contact area symmetrical about the axial direction with respect to the vertex. Thus, by forming a vertically symmetrical cross-sectional shape at least in the sliding contact area, the cross-sectional shape is simplified. The sliding contact area allows for sufficient oil scraping. Therefore, oil consumption can be reduced. Therefore, the cross-sectional shape of the outer peripheral surfaces of the first and second track portions can be simplified, and oil consumption can be reduced.

[0013] In one embodiment, the vertex may be located at the axial center of the outer peripheral surfaces of the first and second track portions. With this structure, not only the sliding contact area, but also the outer peripheral surfaces of the first and second track portions are symmetrical vertically as a whole. Therefore, it is possible to prevent the reverse assembly of the oil control rings from occurring in advance.

[0014] In one embodiment, the outer peripheral surfaces of the first and second track portions may include: a first arcuate surface with a vertex; a pair of inclined surfaces, which are conical surfaces tilted at a predetermined angle relative to the radial direction; and a second arcuate surface connecting the protruding surface to the inclined surfaces, wherein the radius of curvature of the first arcuate surface is greater than the radius of curvature of the second arcuate surface. With this structure, the portion of the first or second track portion near the oil control ring becomes a non-sharp shape. Therefore, defects that may occur in the case of a sharp shape can be suppressed in advance.

[0015] In one embodiment, the ratio of the radius of curvature R1 of the first arc surface to the radius of curvature R2 of the second arc surface, R2 / R1, may be 0.1 or more and 0.6 or less.

[0016] Another aspect of the oil control ring disclosed herein comprises: an annular main body having an inner circumferential surface and an outer circumferential surface, and one side and another side substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, the outer circumferential surface of the first track portion and the second track portion having a protruding surface with a cross-sectional shape convexly projecting toward their respective radially outward, the protruding surface including a sliding contact area, the sliding contact area having: a pair of partially arcuate surfaces respectively disposed on one side and the other side; and a flat portion extending parallel to the axial direction in a manner connecting the pair of partially arcuate surfaces, the pair of partially arcuate surfaces being a portion of an arcuate surface with a radius of curvature of less than 0.30 mm at both ends of the axial direction of the sliding contact area, the sliding contact area having a cross-sectional shape symmetrical about vertically with respect to an imaginary vertex, the imaginary vertex being the imaginary radially outermost point of the arcuate surface.

[0017] In another embodiment of the oil control ring disclosed herein, the outer peripheral surfaces of the first and second track portions have protruding surfaces with cross-sectional shapes that convex outwards towards their respective radial directions. The protruding surfaces include sliding contact areas, which have: a pair of partially arcuate surfaces respectively disposed on one side and the other side; and a flat portion extending parallel to the axial direction in a manner connecting the pair of partially arcuate surfaces. The pair of partially arcuate surfaces are portions of arcuate surfaces with a radius of curvature of 0.30 mm or less at both ends of the axial direction of the sliding contact area. The sliding contact area has a cross-sectional shape that is vertically symmetrical with respect to an imaginary vertex, which is the imaginary radially outermost point of the arcuate surface. According to this structure, the flat portion in the protruding surface and the pair of partially arcuate surfaces on the upper and lower sides of the flat portion form a sliding contact area that is axially symmetrical with respect to an imaginary vertex. Thus, by forming a vertically symmetrical cross-sectional shape at least in the sliding contact area, the cross-sectional shape is simplified. The sliding contact area can effectively scrape off oil. Therefore, oil consumption can be reduced. Therefore, it is possible to simplify the cross-sectional shape of the outer peripheral surfaces of the first and second track sections and reduce oil consumption.

[0018] In one embodiment, the axial dimension of the flat portion may be greater than 0 mm and less than 0.100 mm.

[0019] Invention Effects

[0020] According to the various oil control rings disclosed herein, the cross-sectional shape of the outer peripheral surfaces of the first and second track portions can be simplified, and oil consumption can be reduced. Attached Figure Description

[0021] Figure 1 This is a perspective view of an example of the oil control ring in the implementation method. Figure 2yes Figure 1 An exploded 3D view of the oil control ring. Figure 3 yes Figure 2 A top view of the main body of the oil ring. Figure 4 It is along Figure 3 A cross-sectional view along line IV-IV. Figure 5 yes Figure 4 Enlarged view of the main part of the cross section (enlarged view of the outer periphery of the first track section). Figure 6 (a) is Figure 5 An enlarged sectional view of the sliding contact section of the cross-section. Figure 6 (b) is the equivalent of the oil ring body part in the modified example. Figure 6 (a) Enlarged sectional view. Figure 7 It means having Figure 6 (b) is a figure showing the simulation results of the control ring in section (b). Detailed Implementation

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, in the following description, the same or equivalent elements will be referred to by the same reference numerals, and repeated descriptions will be omitted.

[0023] Figure 1 This is a perspective view of an example of the oil control ring in the implementation method. Figure 2 yes Figure 1 An exploded 3D view of the oil control ring. Figure 3 yes Figure 2 A top view of the main body of the oil ring. Figure 4 It is along Figure 3 A sectional view along line IV-IV. Furthermore, in the following description, the cross-sectional shape refers to the cross-sectional shape along the central axis containing the control ring.

[0024] like Figure 1 , Figure 2 and Figure 3 As shown, the oil control ring 1 has an annular main body 2 and an annular spiral expansion ring 3 assembled along the inner circumferential surface 2a of the main body 2. The oil control ring 1 is a so-called two-piece oil ring. An opening 4 is formed in the main body 2.

[0025] The oil control ring 1 is used, for example, by assembling into an annular groove provided on the outer circumferential surface of the piston in an internal combustion engine of a car. The main body 2 abuts against the inner circumferential surface of the cylinder with a substantially constant surface pressure through the tangential tension of the helical expansion ring 3. Figure 2 As shown, the spiral expansion ring 3 is a spring-like component formed in a ring shape. The spiral expansion ring 3 is formed, for example, from wire such as oil-quenched spring steel.

[0026] The main body 2 is formed, for example, from cast iron or steel containing various metallic elements, to have the strength, heat resistance, and elasticity required for the application. Surface modification, such as based on a hard chromium plating layer, a chromium nitride layer, a PVD layer, or an iron nitride layer, is performed on the outer peripheral surface 2b of the main body 2 (the outer peripheral surfaces of the first track section 7 and the second track section 8) to improve the wear resistance of the main body 2.

[0027] like Figure 1 , Figure 2 and Figure 4 As shown, the main body 2 has a pair of first track sections 7 and second track sections 8 and a column section 13, wherein the column section 13 connects the first track section 7 and the second track section 8.

[0028] like Figure 4 As shown, the inner circumferential surface 2a of the main body 2 is a curved surface recessed towards the column 13 to accommodate the spiral expansion ring 3. The main body 2 has a pair of side surfaces 2c (one side surface) and 2d (the other side surface) that are approximately orthogonal to a pair of end faces (inner circumferential surfaces) 2e radially inward of the inner circumferential surface 2a. In the following description, the direction connecting the inner circumferential surface 2a and the outer circumferential surface 2b is defined as the thickness direction of the oil control ring 1. The direction connecting the side surfaces 2c and 2d is defined as the width direction of the oil control ring 1. The radial direction of the oil control ring 1 is the same as the thickness direction.

[0029] The width h1 of the main body 2 is, for example, 1.0 mm or more and 5.0 mm or less. The thickness a1 of the main body 2 is, for example, 1.0 mm or more and 5.0 mm or less. The outer diameter R0 of the main body 2 (nominal diameter d1, refer to...) Figure 3 For example, the dimensions are 60mm or more and 400mm or less. The dimensions of the main body 2 can be measured using a contact or non-contact shape measuring device. The shape measuring device includes a surface roughness measuring device.

[0030] A pair of first track portions 7 and second track portions 8 are positioned opposite each other axially across a pillar portion 13 in the oil control ring 1. The pillar portion 13 connects the central portions of the first track portions 7 and second track portions 8 in the thickness direction. The first track portion 7 is disposed on the side 2c side of the pillar portion 13, extending radially inward and outward relative to the pillar portion 13. The second track portion 8 is disposed on the side 2d side of the pillar portion 13, extending radially inward and outward relative to the pillar portion 13. The pillar portion 13 is formed to be thinner than the first track portions 7 and second track portions 8 in the thickness direction. Thus, the main body portion 2 has a generally H-shaped cross-sectional shape. The first track portions 7 and second track portions 8 are integrally formed with the pillar portion 13.

[0031] like Figure 1 , Figure 2As shown, a plurality of oil passage holes 14 are arranged circumferentially along the central portion of the column portion 13 in the width direction. The cross-sectional shape of each of the plurality of oil passage holes 14 along the circumferential direction is, for example, approximately elliptical. Figure 4 As shown, the oil passage 14 is located at the axial center of the column portion 13. The oil passage 14 extends radially through the column portion 13.

[0032] Multiple oil passages 14 are formed, for example, by cutting or laser-based perforation. Oil for lubricating the inner circumferential surface of the cylinder is supplied to the inner circumferential surface of the cylinder through these multiple oil passages 14 from the inner circumferential side of the column portion 13 to the outer circumferential side. Oil on the inner circumferential surface of the cylinder returns, for example, to an oil pan, from the outer circumferential side of the column portion 13 to the inner circumferential side through these multiple oil passages 14.

[0033] like Figures 1-3 As shown, the opening 4 is a portion of the main body 2 that has been cut off, and is formed by a pair of opposing opening ends 5 and 6. The pair of opening ends 5 and 6 are the free ends of the main body 2. The gap of the opening 4 (opening gap s1) is, for example, set so that it will not come into contact with the oil control ring 1 when it is heated and thermally expands. When the oil control ring 1 is used, the opening 4 functions as a buffer against the thermal expansion of the main body 2 caused by the temperature difference between the oil control ring 1 and the cylinder.

[0034] In this oil control ring 1, for example, when the piston moves towards top dead center, oil is applied to the inner circumferential surface of the cylinder by the first track portion 7 and the second track portion 8 to form an oil film. For example, when the piston moves towards bottom dead center, the oil control ring 1 scrapes off any remaining oil from the inner circumferential surface of the cylinder by the first track portion 7 and the second track portion 8. Thus, it is possible to form an oil film of appropriate thickness on the inner circumferential surface of the cylinder.

[0035] Next, the outer peripheral surface 2b of the main body 2 will be described in detail. For example... Figure 4 As shown, the outer peripheral surface 2b of the main body 2 includes the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8. Here, the second track portion 8 is symmetrical to the first track portion 7 in the axial direction with respect to the center of the width direction of the main body 2. Therefore, the structure of the first track portion 7 will be described as representative, and repeated descriptions of the second track portion 8 will be omitted.

[0036] The outer peripheral surface 7a of the first track section 7 has a protruding surface 10, an inclined surface 7c, and an inclined surface 7d. The protruding surface 10 is a cross-sectional shape that protrudes radially outward. The inclined surfaces 7c and 7d are conical surfaces inclined at predetermined angles θ1 and θ2 relative to the radial direction, respectively. The inclined surface 7c connects the protruding surface 10 to the side surface 2c via a connecting portion 7b. The inclined surface 7d connects the protruding surface 10 to the column portion 13. The predetermined angles θ1 and θ2 may be, for example, 10° or more and 35° or less. The cross-sectional shape and degree of protrusion of the protruding surface 10 are specified to facilitate the formation of an oil film on the inner peripheral surface of the cylinder. The predetermined angles θ1 and θ2 may be equal to each other or different from each other.

[0037] Figure 5 yes Figure 4 Enlarged view of the main part of the cross section (enlarged view of the outer peripheral surface 7a of the first track section 7). Figure 6 (a) is Figure 5 An enlarged cross-sectional view of the sliding contact portion in the cross-section. (See example...) Figure 5 and Figure 6 As shown in (a), the protruding surface 10 (the outer peripheral surface 7a of the first track portion 7) includes a first arc surface 11, a pair of inclined surfaces 7c and 7d, and a pair of second arc surfaces 12 connecting the first arc surface 11 with the inclined surfaces 7c and 7d. As an example, the protruding surface 10 is composed of three curved regions, namely the first arc surface 11 and the pair of second arc surfaces 12. In other words, it becomes a symmetrical barrel shape symmetrical in the width direction A with the first arc surface 11, which includes the outermost point (vertex 10a) of the outer peripheral surface 7a of the first track portion 7, as the boundary.

[0038] The sliding contact area 15 (first arc surface 11) includes a sliding contact portion that slides in contact with the inner circumferential surface of the cylinder and a sliding contact periphery portion within a certain range on both sides of the sliding contact portion in the axial direction. This certain range corresponds to the range of the actual contact width Lh1 between the first track portion 7 and the inner circumferential surface of the cylinder. This certain range, for example, coincides with the range from the end 11a on the top dead center side of the first arc surface 11 to the end 11b on the bottom dead center side. This certain range may also be a portion of the range from the end 11a on the top dead center side to the end 11b on the bottom dead center side of the first arc surface 11. The actual contact width Lh1 may be 0.010 mm or more and 0.15 mm or less. For example, the actual contact width Lh1 can be set to 0.10 mm.

[0039] The first arc surface 11 includes a vertex 10a, which is the outermost radial point of the first track portion 7. The vertex 10a corresponds to a sliding contact portion that slides in contact with the inner circumferential surface of the cylinder. The sliding contact periphery portion in the first arc surface 11, between the vertex 10a and the end portion 11a and between the vertex 10a and the end portion 11b, corresponds to a sliding contact periphery located on both sides of the axial direction, separated by the sliding contact portion.

[0040] Within the vertex 10a and a certain range, the protruding surface 10 includes a sliding contact region 15. The sliding contact region 15 is a portion of the outer peripheral surface 7a of the first track portion 7 that facilitates the formation of an oil film on the inner peripheral surface of the cylinder. The sliding contact region 15 is a portion that facilitates the formation of an oil film. Generally, for portions that facilitate the formation of an oil film, there is a tendency for the cross-sectional shape to become complex, for example, if repeated analysis is performed. By simplifying the cross-sectional shape of the sliding contact region 15, manufacturing costs can be easily suppressed. Therefore, the sliding contact region 15 has a cross-sectional shape that is axially symmetrical (vertically symmetrical) with respect to the vertex 10a. Figure 5 and Figure 6 In example (a), the sliding contact area 15 coincides with the extent of the first arc surface 11. Alternatively, the sliding contact area 15 may be a portion of the first arc surface 11 and be an axially symmetrical extent with respect to the vertex 10a.

[0041] exist Figure 5 and Figure 6 In example (a), vertex 10a is located at the axial center of the outer peripheral surface 7a of the first track portion 7. That is, the first track portion 7 has a cross-sectional shape that is symmetrical about the axial direction with respect to vertex 10a.

[0042] The first arc surface 11 is an arc surface with a radius of curvature R1 of 0.30 mm or less. The radius of curvature R1 can also be 0.050 mm or more. The radius of curvature R1 can also be 0.076 mm or more and 0.276 mm or less. The first arc surface 11 forms a sliding contact region 15 that is axially symmetrical with respect to the vertex 10a.

[0043] The radius of curvature R1 of the first arc surface 11 is greater than the radii of curvature R2 and R3 of the second arc surface 12. For example, the ratios R2 / R1 and R3 / R1 of the radius of curvature R1 of the first arc surface 11 to the radii of curvature R2 and R3 of the second arc surface 12 are greater than or equal to 0.1 and less than or equal to 0.6. The radii of curvature R2 and R3 of the second arc surface 12 are, for example, equal to each other. The radii of curvature R2 and R3 of the second arc surface 12 may also be different from each other.

[0044] The axial dimension (outer circumferential surface width Lh0) of the protruding surface 10 is, for example, 0.10 mm or more and 0.30 mm or less. The axial dimension of the protruding surface 10 is equivalent to the axial dimension from the boundary between the inclined surface 7c and the protruding surface 10 to the boundary between the inclined surface 7d and the protruding surface 10. The radial dimension D2 from the vertex 10a to the boundary between the inclined surface 7c (or inclined surface 7d) and the protruding surface 10 can also be 0.0045 mm or more and 0.0150 mm or less.

[0045] Alternatively, at least a portion of the protruding surface 10 (here, the first arcuate surface 11) lies on an imaginary convex surface 16 passing through vertex 10a and end points 11a, 11b, which are a pair of points. The end points 11a, 11b are points located radially inward from vertex 10a, 0.05 mm away axially from each side, with a specified drop D1. The drop D1 is 0.0045 mm or more. The drop D1 can also be 0.0150 mm or less. The drop D1 can also be 0.0075 mm or more and 0.0100 mm or less.

[0046] Example

[0047] The invention is illustrated in more detail by way of the following examples, but the invention is not limited to these examples.

[0048] (Example 1)

[0049] As shown in Table 1, the oil control ring 1 of Embodiment 1 was manufactured in the following order. First, a main body 2 was manufactured with a first arc surface 11 provided on the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8. The main body 2 was manufactured using hard steel wire (equivalent to SWRH77B) as per JIS standards, which was rolled and drawn. The width of the main body 2 was set to 3.0 mm. The thickness of the main body 2 was set to 2.5 mm. The actual contact width Lh1 was set to 0.04 mm. The tension was set to 12.48 N. The first arc surface 11 is an arc surface with a vertex 10a at the center and a radius of curvature R1 of 0.30 mm. The width of the first track portion 7 and the second track portion 8 was set to 0.25 mm. To compare oil consumption performance, the surface pressure of the oil control ring 1 was set to 2.6 MPa (calculated surface pressure width = Lh1). After side processing and opening processing of the main body 2, a hard carbon film (DLC film) is formed on the outer peripheral surface 2b of the main body 2 by PVD as a hard film.

[0050] (Example 2)

[0051] The oil control ring 1 of Example 2 is manufactured. Except that the actual contact width Lh1 is set to 0.05 mm and the tension is set to 15.60 N, it is the same as the oil control ring 1 of Example 1.

[0052] (Comparative Example 1)

[0053] An oil control ring of Comparative Example 1 was manufactured, having a sliding contact surface along the axial direction and a conical surface as the outer peripheral surface of the main body of the oil control ring. The angle of the conical surface relative to the axial direction was set to 9°. Except for the shape of the outer peripheral surface of the main body, it was manufactured in the same order as in Example 1. The contact width between the sliding contact surface and the inner peripheral surface of the cylinder was 0.18 mm.

[0054] [Table 1]

[0055] Fuel consumption (LOC) was evaluated in a real-world test using fuel control rings from Examples 1 and 2 and Comparative Example 1 fitted to each cylinder of an inline six-cylinder diesel engine. Operating conditions were 2000 rpm and two load modes (100% load and 50% load). The evaluation results of fuel consumption are shown in Table 2. The LOC improvement rate is expressed as a percentage (%), representing the LOC values ​​of Examples 1 and 2 when the LOC value of Comparative Example 1 is set to 100%.

[0056] [Table 2]

[0057] According to the evaluation results in Table 2, the oil control ring 1 of Examples 1 and 2, compared with Comparative Example 1, showed an improvement of approximately 20% in LOC (full load) and approximately 40% in LOC (medium load). As a result, the first arc surface 11 forms a sliding contact area 15 that facilitates the formation of an oil film on the inner circumferential surface of the cylinder. The first arc surface 11 forms an arc surface with a radius of curvature R1 whose axial dimension (actual contact width Lh1) is the chord length. It can be seen that although the cross-sectional shape of the first arc surface 11 is simplified, it effectively scrapes oil off the inner circumferential surface of the cylinder during piston descent.

[0058] As explained above, according to one aspect of the oil control ring 1 of this disclosure, the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8 have protruding surfaces 10 with cross-sectional shapes that convex outwards towards their respective radial directions. The protruding surface 10 is an arcuate surface with a radius of curvature of 0.30 mm or less in the sliding contact area 15 including the vertex 10a, which is the radially outermost point of the first track portion 7 or the second track portion 8. With this structure, at least a portion (the first arcuate surface 11) of the protruding surface 10 forming the arcuate surface forms a sliding contact area 15 that is axially symmetrical with respect to the vertex 10a. Thus, by forming a cross-sectional shape that is vertically symmetrical at least in the sliding contact area 15, the cross-sectional shape is simplified. Oil can be sufficiently scraped off using the sliding contact area 15. Therefore, a reduction in oil consumption can be achieved. Therefore, the cross-sectional shapes of the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8 can be simplified, and a reduction in oil consumption can be achieved.

[0059] According to another embodiment of the oil control ring 1 of this disclosure, the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8 have protruding surfaces 10 with cross-sectional shapes that convexly project outwards towards their respective radial directions. At least a portion (the first arcuate surface 11) of the protruding surface 10 is located on an imaginary convex surface 16 passing through the vertex 10a and the ends 11a, 11b, with a drop of 0.0045 mm or more. The ends 11a, 11b are a pair of points located radially inwards from the vertex 10a, each 0.05 mm away from the axial direction on both sides, with a predetermined drop. With this structure, at least a portion of the protruding surface 10 forms a sliding contact region 15 that is axially symmetrical with respect to the vertex 10a. Thus, by forming an upper and lower symmetrical cross-sectional shape at least in the sliding contact region 15, the cross-sectional shape is simplified. Oil can be sufficiently scraped off using the sliding contact region 15. Therefore, a reduction in oil consumption can be achieved. Therefore, the cross-sectional shape of the outer peripheral surface 7a of the first track section 7 and the outer peripheral surface 8a of the second track section 8 can be simplified, and the oil consumption can be reduced.

[0060] Vertex 10a is located at the central portion of the axial direction of the outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8. With this structure, not only the sliding contact area 15, but also the outer peripheral surfaces 7a of the first track portion 7 and 8a of the second track portion 8 are symmetrical vertically as a whole. Therefore, it is possible to prevent the reverse assembly of the oil control ring 1 from occurring in advance.

[0061] The outer peripheral surface 7a of the first track portion 7 and the outer peripheral surface 8a of the second track portion 8 include: a first arc surface 11, including a vertex 10a; a pair of inclined surfaces 7c and 7d, which are conical surfaces inclined at a predetermined angle relative to the radial direction; and a second arc surface 12, connecting the protruding surface 10 to the inclined surfaces 7c and 7d. The radius of curvature R1 of the first arc surface 11 is greater than the radius of curvature R2 and R3 of the second arc surface 12. According to this structure, the portions of the first track portion 7 and the second track portion 8 near the oil control ring 1, on the side surface 2c or side surface 2d, become non-sharp. Therefore, defects that could occur in the case of a sharp shape can be suppressed in advance.

[0062] [Variation Example]

[0063] The embodiments of this disclosure have been described above, but this disclosure is not limited to the embodiments described above. This disclosure can be implemented in various ways, with various modifications and improvements based on the knowledge of those skilled in the art, as exemplified by the embodiments described above.

[0064] exist Figure 5 and Figure 6In example (a), the sliding contact area 15 is consistent with the range of the first arc surface 11, and the entire sliding contact area 15 becomes an arc surface with a radius of curvature R1 of 0.30 mm or less, but it is not limited to this example. The sliding contact area may also include a flat portion extending parallel to the axial direction. Figure 6 (b) is about the oil control ring 1M of the modified example, which is equivalent to Figure 6 (a) Enlarged sectional view.

[0065] like Figure 4 and Figure 6 As shown in (b), in the outer peripheral surface 7Ma of the first track portion 7M in the modified example, the protruding surface 10M includes a sliding contact area 15M, which has a pair of partially arcuate surfaces 11c and 11f and a flat portion 17, the flat portion 17 connecting the pair of partially arcuate surfaces 11c and 11f. The cross-sectional shape of the first track portion 7M is, for example, a shape in which the outer peripheral surface 7a is cut out within a predetermined range (flat portion 17) that is symmetrical about the vertex 10a in the above-described outer peripheral surface 7a of the first track portion 7.

[0066] A pair of partially arcuate surfaces 11c and 11f are respectively disposed on side 2c (one side) and side 2d (the other side). The end of the partially arcuate surface 11c on side 2c coincides with the end of the first arcuate surface 11 on side 2c, which is end 11a. The end of the partially arcuate surface 11f on side 2d coincides with the end of the first arcuate surface 11 on side 2d, which is end 11b. The pair of partially arcuate surfaces 11c and 11f are respectively equivalent to a portion of the upper and lower end sides of the first arcuate surface 11. That is, the pair of partially arcuate surfaces 11c and 11f are portions of the first arcuate surface 11 whose radius of curvature is less than 0.30 mm at both ends, i.e., ends 11a and 11b, in the width direction A (axial direction) of the sliding contact area 15M.

[0067] A pair of partially circular arc surfaces 11c and 11f are vertically symmetrical with respect to an imaginary vertex 10x. The imaginary vertex 10x is the imaginary radially outermost point of the first circular arc surface 11 passing through the ends 11a and 11b. The imaginary vertex 10x is an imaginary vertex equivalent to the aforementioned vertex 10a. Unlike the aforementioned first circular arc surface 11, the pair of partially circular arc surfaces 11c and 11f do not actually contain vertex 10a; therefore, the imaginary vertex 10x can be defined here as an imaginary vertex equivalent to vertex 10a.

[0068] Flat part 17 is Figure 6(b) The portion with a straight cross-section. The flat portion 17 extends parallel to the width direction A in such a way that it connects a pair of partially arcuate surfaces 11c and 11f. The end of the flat portion 17 on the side 2c side coincides with the end of the side 2d side of the partially arcuate surface 11c, forming the top portion 11d. The end of the flat portion 17 on the side 2d side coincides with the end of the side 2c side of the partially arcuate surface 11f, forming the top portion 11e. The flat portion 17 extends from the top portion 11d to the top portion 11e within a predetermined range of vertical symmetry with respect to the imaginary vertex 10x. Therefore, the pair of partially arcuate surfaces 11c and 11f and the flat portion 17 are vertically symmetrical with respect to the imaginary vertex 10x. That is, the sliding contact area 15M has a cross-sectional shape that is vertically symmetrical with respect to the imaginary radial outermost point of the first arcuate surface 11, i.e., the imaginary vertex 10x.

[0069] The sliding contact area 15M includes a sliding contact portion that slides in contact with the inner circumferential surface of the cylinder and a sliding contact peripheral portion within a certain range on both sides of the sliding contact portion in the axial direction. The flat portion 17 corresponds to the sliding contact portion that slides in contact with the inner circumferential surface of the cylinder. The area between the top end portion 11d and the end end portion 11a and the area between the top end portion 11e and the end end portion 11b corresponds to the area including the sliding contact peripheral portion within a certain range on both sides of the sliding contact portion in the axial direction. Within the flat portion 17 and within this certain range, the protruding surface 10M includes the sliding contact area 15M, which is the portion of the outer circumferential surface 7Ma of the first track portion 7M that helps to form an oil film on the inner circumferential surface of the cylinder.

[0070] The axial dimension of the flat portion 17 from the top end 11d to the top end 11e, i.e., the width Lh2 of the flat portion 17, can be greater than 0 mm and less than 0.100 mm. The width Lh2 of the flat portion 17 can also be greater than 0 mm and less than 0.085 mm. The width Lh2 of the flat portion 17 can also be greater than 0 mm and less than 0.070 mm.

[0071] Specifically, Figure 7 It means having Figure 6 (b) is a figure showing the simulation results of the control ring 1M in section (b). Figure 7 The horizontal axis represents the width of the flat portion, Lh². The vertical axis represents the average minimum oil film thickness during the piston's downward stroke in the internal combustion engine. The units for both the horizontal and vertical axes are μm. Figure 7 In the section on the oil control ring 1M, simulation results are shown to confirm the effect of reducing oil consumption. As part of the simulation, in... Figure 7 In the example, the oil film thickness of the oil control ring 1M and the inner circumferential surface of the cylinder was theoretically calculated using Patir & Cheng's average Reynolds equation. In the simulation, the oil control ring 1 of the specifications used in the above-described embodiment 1 was provided with a flat portion 17, and the width Lh2 of the flat portion 17 was calculated by varying several values.

[0072] exist Figure 7 The calculation results for the flat portion width Lh22 of 0 μm (dashed circle), 70 μm (0.070 mm), 85 μm (0.085 mm), 100 μm (0.100 mm) (dashed circle), 120 μm (0.120 mm) (dashed circle), and 150 μm (0.150 mm) (dashed circle) are plotted. The solid circle corresponds to Example 3. As a comparative example, the calculation results for the plotting of a straight-shaped oil control ring with its outer peripheral surface parallel to the axial direction (straight line) and the plotting of a conical-shaped oil control ring with its outer peripheral surface inclined to the axial direction (conical) are plotted in [the diagram]. Figure 7 In the context of oil film thickness, the average minimum oil film thickness during the piston's downward stroke in an internal combustion engine is calculated. For example... Figure 7 As shown, it can be seen that within a range where the width Lh2 of the flat portion is less than 100 μm (0.100 mm), a smaller oil film thickness can be obtained compared to the calculated results for the straight and conical shapes in the comparative example. It can also be seen that within a range where the width Lh22 of the flat portion is less than 85 μm (0.085 mm), a smaller oil film thickness can be obtained than the case where the width Lh2 of the flat portion is 100 μm (0.100 mm). Furthermore, it can be seen that within a range where the width Lh2 of the flat portion is less than 70 μm (0.070 mm), a smaller oil film thickness can be obtained than the case where the width Lh2 of the flat portion is 85 μm (0.085 mm).

[0073] Thus, according to the oil control ring 1M, the outer peripheral surface 7Ma of the first track portion 7M (and the outer peripheral surface of the second track portion as well) has a protruding surface 10M with a cross-sectional shape that convexly protrudes radially outward. The protruding surface 10M includes a sliding contact area 15M, which has a pair of partially arcuate surfaces 11c and 11f respectively disposed on the side 2c (one side) and the side 2d (the other side), and a flat portion 17 extending parallel to the width direction A in a manner that connects the pair of partially arcuate surfaces 11c and 11f. The pair of partially arcuate surfaces 11c and 11f are part of a first arcuate surface 11 with a radius of curvature of 0.30 mm or less at both ends 11a and 11b in the width direction A (axial direction) of the sliding contact area 15M. The sliding contact area 15M has a cross-sectional shape that is vertically symmetrical with respect to the imaginary radial outermost point, i.e., the imaginary vertex 10x, of the first arcuate surface 11. According to this structure, the flat portion 17 in the protruding surface 10M and a pair of partially arcuate surfaces 11c and 11f on the upper and lower sides of the flat portion 17 form a sliding contact region 15M that is symmetrical in the width direction A with respect to the imaginary vertex 10x. Thus, by setting the cross-sectional shape to be symmetrical at least in the sliding contact region 15M, the cross-sectional shape is simplified. Oil can be sufficiently scraped off through the sliding contact region 15M. Therefore, oil consumption can be reduced. Therefore, the cross-sectional shape of the outer peripheral surface 7Ma of the first track portion 7M and the second track portion can be simplified, and oil consumption can be reduced.

[0074] In the above embodiment, the imaginary convex surface 16 coincides with the arc surface of the radius of curvature R1, but is not limited to this example. For example, at least a portion of the protruding surface 10 may also be located on the imaginary convex surface 16, which has a polygonal cross-section such as a vertex 10a and a pair of points.

[0075] In the above embodiment, the actual contact width Lh1 of the first arc surface 11, which is part of the protruding surface 10, is 0.10 mm, but it can also be less than 0.10 mm as in the embodiment. That is, the pair of positions that are 0.05 mm away from each side of the vertex 10a in the axial direction, which define the drop of the imaginary convex surface 16, can also be the positional relationship of the protruding surface 10 located on the imaginary convex surface 16. In such a case, the drop can be calculated with a similar idea. For example, at least a portion of the protruding surface 10 can be located on the imaginary convex surface 16 passing through the vertex 10a and a pair of points that are 0.01 mm away from each side of the vertex 10a in the axial direction and are located radially inward with a defined drop of 0.0009 mm or more.

[0076] In the above embodiment, the vertex 10a is located at the axial center of the outer peripheral surface 7a of the first track portion 7, but it is not limited to this example. For example, at least the sliding contact area 15 may have a cross-sectional shape that is symmetrical about the vertex 10a in the axial direction, and the first track portion 7 and the second track portion 8 may each be asymmetrical about the vertex 10a in the axial direction as a whole.

[0077] In the above embodiment, the protruding surface 10 has a second arcuate surface 12 connecting the protruding surface 10 to the inclined surfaces 7c and 7d, but it is not limited to this example. For example, instead of the second arcuate surface 12, it may be a polygonal cross-sectional shape or a straight conical surface.

[0078] Furthermore, the constituent elements of various methods disclosed herein are described below.

[0079] <Invention 1> An oil-controlling ring comprises: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, wherein the outer circumferential surface of the first track portion and the second track portion has a protruding surface with a cross-sectional shape that convexly protrudes towards their respective radially outward, the protruding surface being an arc surface with a radius of curvature of less than 0.30 mm in a sliding contact region including a vertex, the vertex being the radially outermost point of the first track portion or the second track portion.

[0080] <Invention 2> An oil control ring comprises: an annular main body having an inner circumferential surface, an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, the outer circumferential surface of the first track portion and the second track portion including a protruding surface with a cross-sectional shape convexly projecting toward their respective radially outward, at least a portion of the protruding surface being located on an imaginary convex surface passing through a vertex and a pair of points, the vertex being the radially outermost point of the first track portion or the second track portion, the pair of points being 0.05 mm away from the vertex axially to both sides and located radially inward with a predetermined drop of 0.0045 mm or more.

[0081] <Invention 3> According to the oil control ring described in invention 1 or 2, the vertex is located at the axial center of the outer peripheral surfaces of the first track portion and the second track portion, respectively.

[0082] <Invention 4> According to any one of the inventions 1 to 3, the outer peripheral surfaces of the first track portion and the second track portion include: a first arc surface including the vertex; a pair of inclined surfaces, which are conical surfaces inclined at a predetermined angle relative to the radial direction; and a second arc surface connecting the protruding surface to the inclined surfaces, wherein the radius of curvature of the first arc surface is greater than the radius of curvature of the second arc surface.

[0083] <Invention 5> According to the oil control ring described in Invention 4, the ratio of the radius of curvature R1 of the first arc surface to the radius of curvature R2 of the second arc surface, R2 / R1, is 0.1 or more and 0.6 or less.

[0084] <Invention 6> An oil-controlling ring comprises: an annular main body having an inner circumferential surface and an outer circumferential surface, and one side and another side substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein the main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portion and the second track portion, the outer circumferential surfaces of the first track portion and the second track portion having protruding surfaces with a cross-sectional shape convexly projecting outward toward their respective radial directions, the protruding surfaces including a sliding contact area, the sliding contact area having: a pair of partially arcuate surfaces respectively disposed on the one side and the other side; and a flat portion extending parallel to the axial direction in a manner connecting the pair of partially arcuate surfaces, the pair of partially arcuate surfaces being portions of arcuate surfaces with a radius of curvature of less than 0.30 mm at both ends of the axial direction of the sliding contact area, the sliding contact area having a cross-sectional shape symmetrical about vertically with respect to an imaginary vertex, the imaginary vertex being the imaginary outermost point of the arcuate surface.

[0085] <Invention 7> According to the oil control ring described in Invention 6, the axial dimension of the flat portion is greater than 0 mm and less than 0.100 mm.

[0086] Label Explanation 1, 1M… Oil control ring, 2… Main body, 2a… Inner circumferential surface, 2b… Outer circumferential surface, 2c… Side surface (one side), 2d… Side surface (the other side), 3… Spiral expansion ring, 7, 7M… First track section, 8… Second track section, 7a, 8a… Outer circumferential surface, 7c… Inclined surface, 7d… Inclined surface, 10, 10M… Protruding surface, 10a… Vertex, 10x… Imaginary vertex, 11… First arc surface, 11c, 11f… Partial arc surface, 12… Second arc surface, 13… Column section, 15, 15M… Sliding contact area, D1… Drop, R1, R2, R3… Radius of curvature.

Claims

1. An oil-controlling ring, comprising: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a helical expansion ring assembled along the inner circumferential surface, wherein, The main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portions and the second track portions. The outer peripheral surfaces of the first track portion and the second track portion have protruding surfaces with a cross-sectional shape that convex outwards towards their respective radial directions. The protruding surface is an arc surface with a radius of curvature of less than 0.30 mm in the sliding contact area including the vertex, and the vertex is the outermost radial point of the first track portion or the second track portion. The second track portion is symmetrical to the first track portion in the axial direction with respect to the center of the width direction of the main body portion. The vertex is located at the center of the respective axial direction of the outer peripheral surfaces of the first track portion and the second track portion.

2. An oil-controlling ring, comprising: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein, The main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portions and the second track portions. The outer peripheral surfaces of the first track portion and the second track portion include protruding surfaces with a cross-sectional shape that convex outwards towards their respective radial directions. At least a portion of the protruding surface lies on an imaginary convex surface passing through a vertex and a pair of points, the vertex being the radially outermost point of the first or second track portion, and the pair of points being radially inner, each 0.05 mm away from the vertex and with a predetermined drop. The drop is greater than 0.0045mm. The second track portion is symmetrical to the first track portion in the axial direction with respect to the center of the width direction of the main body portion. The vertex is located at the center of the respective axial direction of the outer peripheral surfaces of the first track portion and the second track portion.

3. An oil-controlling ring, comprising: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein, The main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portions and the second track portions. The outer peripheral surfaces of the first track portion and the second track portion have protruding surfaces with a cross-sectional shape that convex outwards towards their respective radial directions. The protruding surface is an arc surface with a radius of curvature of less than 0.30 mm in the sliding contact area including the vertex, and the vertex is the outermost radial point of the first track portion or the second track portion. The outer peripheral surfaces of the first track portion and the second track portion include: a first arc surface containing the vertex; a pair of inclined surfaces, which are conical surfaces inclined at a predetermined angle relative to the radial direction; and a second arc surface connecting the protruding surface to the inclined surfaces. The radius of curvature of the first arc surface is greater than the radius of curvature of the second arc surface. The vertex is located at the center of the respective axial direction of the outer peripheral surfaces of the first track portion and the second track portion.

4. An oil-controlling ring, comprising: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a spiral expansion ring assembled along the inner circumferential surface, wherein, The main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portions and the second track portions. The outer peripheral surfaces of the first track portion and the second track portion include protruding surfaces with a cross-sectional shape that convex outwards towards their respective radial directions. At least a portion of the protruding surface lies on an imaginary convex surface passing through a vertex and a pair of points, the vertex being the radially outermost point of the first or second track portion, and the pair of points being radially inner, each 0.05 mm away from the vertex and with a predetermined drop. The drop is greater than 0.0045mm. The outer peripheral surfaces of the first track portion and the second track portion include: a first arc surface containing the vertex; a pair of inclined surfaces, which are conical surfaces inclined at a predetermined angle relative to the radial direction; and a second arc surface connecting the protruding surface to the inclined surfaces. The radius of curvature of the first arc surface is greater than the radius of curvature of the second arc surface. The vertex is located at the center of the respective axial direction of the outer peripheral surfaces of the first track portion and the second track portion.

5. The oil control ring according to claim 3 or 4, wherein, The ratio of the radius of curvature R1 of the first arc surface to the radius of curvature R2 of the second arc surface, R2 / R1, is greater than 0.1 and less than 0.

6.

6. An oil-controlling ring, comprising: an annular main body having an inner circumferential surface and an outer circumferential surface, and a side surface and a side surface substantially orthogonal to the inner circumferential surface; and a helical expansion ring assembled along the inner circumferential surface, wherein, The main body has: a pair of annular first track portions and a second track portion; and a column portion connecting the first track portions and the second track portions. The outer peripheral surfaces of the first track portion and the second track portion have protruding surfaces with a cross-sectional shape that convex outwards towards their respective radial directions. The protruding surface includes a sliding contact area, the sliding contact area having: a pair of partially arcuate surfaces respectively disposed on one side and the other side; and a flat portion extending parallel to the axial direction in a manner connecting the pair of partially arcuate surfaces. The pair of said partial arc surfaces are portions of arc surfaces with a radius of curvature of less than 0.30 mm at both ends of the axial direction of the sliding contact area. The sliding contact area has a cross-sectional shape that is symmetrical about its top and bottom relative to an imaginary vertex, which is the imaginary outermost radial point of the arc surface. The second track portion is symmetrical to the first track portion in the axial direction with respect to the width direction of the main body portion.

7. The oil control ring according to claim 6, wherein, The axial dimension of the flat portion is greater than 0 mm and less than 0.100 mm.

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