Piston ring set

Abstract

A piston ring group on one side surface, which is inserted into a cylinder bore of an internal combustion engine, is provided with: a top ring having an annular main body section including an inner peripheral surface, an outer peripheral surface, one side surface and the other side surface substantially orthogonal to the inner peripheral surface, and first and second open end sections facing each other to form an opening; the oil ring has a pair of rails facing each other, the opening flow area of the top ring is 0.1 mm2 or less, and the outer circumference followability coefficient of the oil ring is 0.3 or more.

Description

Technical Field

[0001] The present disclosure relates to piston ring sets. Background Art

[0002] A piston ring assembly used in internal combustion engines, such as automobiles, is mounted in a ring groove on the outer circumferential surface of a piston. Mounted in the ring groove, the piston ring assembly slides against the inner wall of the cylinder bore. This assembly maintains an airtight seal between the combustion chamber and the crankcase, reducing oil consumption. A known example of such a piston ring assembly is that described in Patent Document 1.

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2013-231481 Summary of the Invention

[0004] Problems to be solved by the invention

[0005] To improve the fuel economy of internal combustion engines, it is necessary to reduce blowby gas leaking into the crankcase. However, as blowby gas is reduced, oil consumption and friction increase, making it difficult to effectively reduce all of these factors. One aspect of the present disclosure provides a piston ring assembly that can reduce blowby gas, oil consumption, and friction.

[0006] Means for solving problems

[0007] A piston ring assembly according to one aspect of the present disclosure includes a top ring and an oil ring, and is inserted into a cylinder bore of an internal combustion engine while being mounted on a piston. The top ring has an annular main body portion, the annular main body portion including an inner peripheral surface, an outer peripheral surface, a first side surface and a second side surface substantially orthogonal to the inner peripheral surface, and a first opening end portion and a second opening end portion facing each other to form an opening portion. The oil ring has a pair of rails facing each other, and the opening flow area of ​​the top ring is 0.1 mm 2 Hereinafter, the outer periphery followability coefficient of the oil ring is 0.3 or more.

[0008] In this piston ring set, the top ring has an opening flow area of ​​0.1mm 2 Below, and the outer periphery followability coefficient of the oil ring is 0.3 or above. The flow area through the opening is 0.1mm 2This reduces blowby. However, as blowby decreases, the amount of oil blown off by the blowby decreases. Consequently, there is a tendency for excess oil adhering to the inner surface of the cylinder bore to increase, and friction on the top ring to also increase. Since the oil ring's outer circumference followability coefficient is 0.3 or greater, the oil ring follows the inner surface of the cylinder bore well. Therefore, excess oil adhering to the inner surface of the cylinder bore caused by the top ring is effectively scraped off by the oil ring. Therefore, when using the piston ring assembly comprising both the top ring and the oil ring, the reduction in oil consumption due to the oil ring exceeds the increase in oil consumption due to the top ring. In other words, using the piston ring assembly can reduce blowby, oil consumption, and friction. In particular, friction with the piston ring assembly comprising both the top ring and the oil ring can be reduced to the same extent as friction with the piston ring assembly comprising the oil ring.

[0009] Effects of the Invention

[0010] According to one aspect of the present disclosure, it is possible to provide a piston ring set capable of reducing blowby gas, oil consumption, and friction, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a perspective view of a piston ring assembly according to an embodiment. Figure 2 It is a cross-sectional view of the oil ring according to the embodiment. Figure 3 (a) is a cross-sectional view showing an example of a barrel-shaped track. Figure 3 (b) is a cross-sectional view showing an example of a track having a tapered surface shape. Figure 3 (c) is a cross-sectional view showing an example of the bullet surface shape. Figure 4 This is an enlarged schematic diagram of the main part showing blowby gas leaking from the top ring. Figure 5 (a) is an enlarged schematic diagram of the main part of an example of the opening of the top ring. Figure 5 (b) is an enlarged schematic diagram of a main part of an example of a chamfered portion of the outer peripheral lower surface of the top ring. Figure 6 (a) to (c) are graphs showing the experimental results of the comparative example. Figure 6 (d) is a graph showing the experimental results of Examples. Figure 7 (a) and (b) are graphs showing the experimental results of Examples. Figure 8 (a) is a graph showing the experimental results of the comparative example. Figure 8 (b) to (d) are graphs showing the experimental results of Examples. Figure 9(a) and (b) are graphs showing the experimental results of the comparative example. Figure 9 (c) to (f) are graphs showing the experimental results of Examples. DETAILED DESCRIPTION

[0012] [Summary of Embodiments of the Present Disclosure]

[0013] First, an overview of the embodiments of the present disclosure will be described.

[0014] (1) A piston ring assembly comprising a top ring and an oil ring, which is inserted into a cylinder bore of an internal combustion engine while being mounted on a piston, wherein the top ring has an annular main body portion, the annular main body portion including an inner peripheral surface, an outer peripheral surface, a first side surface and a second side surface substantially orthogonal to the inner peripheral surface, and a first opening end portion and a second opening end portion facing each other to form an opening portion, the oil ring has a pair of rails facing each other, and the opening flow area of ​​the top ring is 0.1 mm 2 Hereinafter, the outer periphery followability coefficient of the oil ring is 0.3 or more.

[0015] (2) The piston ring set according to (1), wherein the outer periphery followability coefficient of the oil ring is 0.8 or less.

[0016] (3) The piston ring assembly according to (1) or (2), wherein the main body is provided with a first opening chamfered surface, a second opening chamfered surface, and an outer peripheral lower surface chamfered surface, the first opening chamfered surface being located between the first opening end and the outer peripheral surface, the second opening chamfered surface being located between the second opening end and the outer peripheral surface, and the outer peripheral lower surface chamfered surface being located between one of the first side surface and the second side surface and the outer peripheral surface, When the top ring and the oil ring are inserted into the cylinder hole in a state where they are mounted on the piston, A first opening chamfered portion is formed between the inner surface of the cylinder hole and the first opening chamfered surface, a second opening chamfered portion is formed between the inner surface and the second opening chamfered surface, and an outer peripheral lower surface chamfered portion is formed between the inner surface and the outer peripheral lower surface chamfered surface. When the gap between the first opening end and the second opening end is s1, the gap between the outer surface of the piston and the inner surface of the cylinder bore is g1, the correction coefficient based on the inner diameter of the cylinder bore is f, the size of the first opening chamfer is C1, the size of the second opening chamfer is C2, and the size of the outer peripheral lower surface chamfer is C3, the opening flow area is expressed as s1×g1×f+C1+C2+2×C3. When the tension of the oil ring is Ft, the inner diameter of the cylinder bore is d1, the thickness of each of the pair of rails along the radial direction of the cylinder bore is a1, the elastic modulus of the material constituting each of the pair of rails is E, and the width of each of the pair of rails along the axial direction of the cylinder bore is h12, the outer peripheral followability coefficient is expressed as 3 / 2×Ft×(d1-a1). 2 / (E×h12×a1 3 ).

[0017] (4) The piston ring set according to (3), wherein a dimension of the outer peripheral lower surface chamfered portion in the radial direction is smaller than a dimension of the outer peripheral lower surface chamfered portion in the axial direction.

[0018] (5) A piston ring assembly according to any one of (1) to (4), wherein the piston ring assembly further comprises a second ring, the second ring having an annular second main body portion, the second main body portion including a third opening end portion and a fourth opening end portion facing each other to form a second opening portion, and the ratio of the gap between the third opening end portion and the fourth opening end portion to the gap between the first opening end portion and the second opening end portion is 1.8 or less.

[0019] (6) The piston ring set according to any one of (1) to (5), wherein each outer peripheral surface of the pair of raceways has either a tapered surface shape or a bullet surface shape.

[0020] [Examples of Embodiments of the Present Disclosure]

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted as appropriate.

[0022] Figure 1 It is a perspective view of a piston ring assembly according to an embodiment. Figure 1 The top ring 10, second ring 20, and oil ring 30 shown in the figure constitute a piston ring set 1. The piston ring set 1 is assembled into a ring groove on the outer circumferential surface of a piston in, for example, an automotive internal combustion engine. Once assembled on the piston, the piston ring set 1 is inserted into the cylinder bore of the internal combustion engine. By sliding against the inner wall of the cylinder bore, the piston ring set 1 provides a gas seal between the combustion chamber and the crankcase, and reduces oil consumption.

[0023] The top ring 10 has an annular main body 11. The main body 11 includes a side surface (first side surface) 11a, a side surface (second side surface) 11b, an inner peripheral surface 11c, an outer peripheral surface 11d, an opening end (first opening end) 13, and an opening end (second opening end) 14. The side surfaces 11a and 11b are substantially perpendicular to the inner peripheral surface 11c. Figure 1 In the example shown, side surface 11a is the upper surface of main body 11, and side surface 11b is the lower surface of main body 11. Open end portions 13 and 14 face each other to form opening 15. In the following description, the direction connecting side surface 11a and side surface 11b is referred to as the width direction of top ring 10, and the direction connecting inner circumferential surface 11c and outer circumferential surface 11d is referred to as the thickness direction of top ring 10. The width direction of top ring 10 corresponds to the axial direction D1 of the cylinder bore into which piston ring assembly 1 is inserted. The thickness direction of top ring 10 corresponds to the radial direction D2 of the cylinder bore into which piston ring assembly 1 is inserted. The direction in which main body 11 extends annularly corresponds to the circumferential direction D3 of the cylinder bore.

[0024] The main body 11 has a substantially rectangular cross-section with its long sides in the thickness direction and its short sides in the width direction. The main body 11 is formed using, for example, cast iron or steel containing multiple metal elements to have sufficient strength, heat resistance, and elasticity.

[0025] The surface of the main body 11 may also be modified to form a hard film. The hard film is, for example, a physical vapor deposition film (PVD film) formed using a physical vapor deposition method (PVD method). This allows for the formation of a hard film with sufficient hardness. The hard film is an ion-plated film or a diamond-like carbon film containing at least one of titanium (Ti) and chromium (Cr) and at least one of carbon (C), nitrogen (N), and oxygen. Specific examples include titanium nitride films, chromium nitride films, titanium carbonitride films, chromium carbonitride films, chromium oxynitride films, chromium films, or titanium films. From the perspectives of wear resistance and scratch resistance, the hard film may also be a chromium nitride film. The hard film may also be a laminate, for example, containing a chromium nitride film and a diamond-like carbon film.

[0026] The opening 15 is a gap formed by partially cutting off the main body 11. The opening ends 13 and 14 are free ends of the main body 11. The size of the opening 15 is represented by the gap s1 between the opening ends 13 and 14 when the top ring 10 is inserted into the cylinder bore at room temperature.

[0027] The second ring 20 has an annular main body 21. The main body 21 includes a side surface 21a, a side surface 21b, an inner peripheral surface 21c, an outer peripheral surface 21d, an opening end (third opening end) 23, and an opening end (fourth opening end) 24. The side surfaces 21a and 21b are substantially orthogonal to the inner peripheral surface 21c. Figure 1In the example shown, side surface 21a is the upper surface of the main body 21, and side surface 21b is the lower surface of the main body 21. Opening ends 23 and 24 face each other, forming an opening (second opening) 25. The main body 21 may be formed of the same material as the top ring 10. Similarly to the top ring 10, the surface of the main body 21 may be modified to form a hard film.

[0028] The opening 25 is a gap formed by partially cutting off the main body 21. The open ends 23 and 24 are free ends of the main body 21. The dimension of the opening 25 is represented by the gap s2 between the openings 23 and 24 when the second ring 20 is inserted into the cylinder bore at room temperature. Hereinafter, the ratio of gap s2 to gap s1 (s2 / s1) is referred to as the "S1 ratio." In this embodiment, the S1 ratio is 1.8 or less. Alternatively, the S1 ratio may be 1.5 or less. Alternatively, the S1 ratio may be 1.4 or less.

[0029] The oil ring 30 includes a pair of opposing rails 31 and a spacer expander 32. The rails 31 serve as side rails for the oil ring 30. The spacer expander 32 is positioned between the rails 31. In this embodiment, the rails 31 and the spacer expander 32 form a three-piece oil ring 30. Furthermore, each rail 31 has an opening.

[0030] Figure 2 It is a cross-sectional view of the oil ring according to the embodiment. Figure 2 : shows the structure of the oil ring 30 in a cross section perpendicular to the circumferential direction D3. Figure 2 As shown, each track 31 has a side surface 31a, a side surface 31b, an inner peripheral surface 31c, and an outer peripheral surface 31d. The side surface 31a and the side surface 31b constitute the two ends of each track 31 in the axial direction D1. Figure 2 In the example shown in FIG, the side surface 31a is the surface facing outward, and the side surface 31b is the surface facing the spacer outer expander 32. Each rail 31 may be formed of the same material as the top ring 10. Details of the shape of the outer peripheral surface 31d will be described later.

[0031] The outer circumference following coefficient k of the oil ring 30 is expressed by the following mathematical formula. k=3 / 2×Ft×(d1-a1) 2 / (E×h12×a1 3 )

[0032] Ft is the tension of the oil ring 30. The tension Ft of the oil ring 30 is not particularly limited. From the perspective of reducing friction, the tension Ft can be less than 20N, less than 15N, or less than 12N. d1 is the inner diameter of the cylinder hole into which the oil ring 30 is inserted. a1 is the thickness of each track 31 along the radial direction D2. E is the elastic modulus of the material constituting each track 31. h12 is the width of each track 31 along the axial direction D1. The peripheral tracking coefficient k of the oil ring 30 is greater than 0.3. The peripheral tracking coefficient k of the oil ring 30 can be greater than 0.4, or greater than 0.5. In the present embodiment, the peripheral tracking coefficient k of the oil ring 30 is greater than 0.3 and less than 0.8.

[0033] By setting the peripheral tracking coefficient k to 0.8 or less, an increase in oil consumption due to deformation of the rail 31 is minimized. To achieve both reduced tension Ft and improved peripheral tracking coefficient k, the thickness a1 can be 1.65 mm or less, or 1.50 mm or less. There is no particular lower limit for the thickness a1. To ensure the rigidity of the rail 31, the lower limit of the thickness a1 can be 1.30 mm or greater.

[0034] Figure 3 (a) to (c) are cross-sectional views showing details of the shape of the outer peripheral surface 31d. Each rail 31 may have a barrel shape. Figure 3 (a) is a cross-sectional view showing an example of a barrel-shaped track. Figure 3 As shown in (a), the outer peripheral surface 31d includes a sliding surface B1 having a first radius of curvature and a pair of edge surfaces B2 having a second radius of curvature. The sliding surface B1 is curved so as to protrude toward the cylinder bore into which the oil supply ring 30 is inserted. The sliding surface B1 is sandwiched between the pair of edge surfaces B2 in the axial direction D1. One edge surface B2 is located between the side surface 31a and the sliding surface B1, connecting the side surface 31a and the sliding surface B1. The other edge surface B2 is located between the side surface 31b and the sliding surface B1, connecting the side surface 31b and the sliding surface B1. The first radius of curvature is smaller than the second radius of curvature. The length of the sliding surface B1 along the axial direction D1 is denoted as b1. The length of the sliding surface B1 along the radial direction D2 is denoted as b2. In the barrel-shaped outer peripheral surface 31d, the shape can be symmetrical or asymmetrical with respect to the centerline of the rail 31 in the axial direction D1.

[0035] Each rail 31 may have a tapered shape. Figure 3 (b) is a cross-sectional view showing an example of a track having a conical surface shape. Figure 3As shown in (b), the outer peripheral surface 31d includes an inclined surface T1 and a sliding surface T2 that extend linearly in a manner inclined relative to the axial direction D1. The inclined surface T1 is inclined so as to protrude toward the cylinder hole into which the oil supply ring 30 is inserted as the distance from the side surface 31b decreases. The sliding surface T2 is curved so as to protrude toward the cylinder hole into which the oil supply ring 30 is inserted. The inclination of the inclined surface T1 relative to the axial direction D1 is represented by t1. The length of the sliding surface T2 along the radial direction D2 is represented by t2. The length between the most protruding part of the sliding surface T2 and the side surface 31b along the axial direction D1 is represented by t3. In the tapered surface shape, the shape of the outer peripheral surface 31d is asymmetrical with respect to the center line in the axial direction D1 of the rail 31.

[0036] Each rail 31 may also have a bullet-shaped surface. Figure 3 (c) is a cross-sectional view showing an example of a track having a bullet surface shape. Figure 3 As shown in (c), the outer peripheral surface 31d includes a sliding surface BT1 having a third radius of curvature and a pair of linearly extending edge surfaces BT2. The sliding surface BT1 is curved to protrude toward the cylinder bore into which the oil supply ring 30 is inserted. The sliding surface BT1 is sandwiched between the pair of edge surfaces BT2 in the axial direction D1. The pair of edge surfaces BT2 connect the side surfaces 31a and 31b to the sliding surface BT1. The length of the sliding surface BT1 along the axial direction D1 is denoted as bt1. The length of the sliding surface BT1 along the radial direction D2 is denoted as bt2.

[0037] Figure 4 This is an enlarged schematic diagram of the main part showing blowby gas leaking from the top ring. Figure 5 (a) is an enlarged schematic diagram of the main part of an example of the opening of the top ring. Figure 5 (b) is an enlarged schematic diagram of the main part of an example of the chamfered portion of the outer peripheral lower surface of the top ring. Figure 4 and Figure 5 As shown, the main body portion 11 includes chamfered surfaces 13a, 14a and a chamfered surface 11e.

[0038] The chamfered surface 13a is located between the opening end 13 and the outer peripheral surface 11d and connects the opening end 13 and the outer peripheral surface 11d (a first opening chamfered surface). The chamfered surface 13a is formed by chamfering the corner formed by the opening end 13 and the outer peripheral surface 11d. An opening chamfered portion (a first opening chamfered portion) 16 is formed between the chamfered surface 13a and the inner surface 3a of the cylinder bore 3. The opening chamfered portion 16 is a gap corresponding to the portion removed from the main body 11 by chamfering the corner formed by the opening end 13 and the outer peripheral surface 11d. The chamfered surface 14a is located between the opening end 14 and the outer peripheral surface 11d and connects the opening end 14 and the outer peripheral surface 11d (a second opening chamfered surface). The chamfered surface 14a is formed by chamfering the corner formed by the opening end 14 and the outer peripheral surface 11d. The opening chamfer 17 is a gap corresponding to the portion removed from the main body 11 by chamfering the corner formed by the opening end 14 and the outer peripheral surface 11d. An opening chamfer (second opening chamfer) 17 is formed between the chamfered surface 14a and the inner surface 3a of the cylinder bore 3. The area of ​​the opening chamfer 16 as viewed along the axial direction D1 is denoted by C1. The area of ​​the opening chamfer 17 as viewed along the axial direction D1 is denoted by C2. The areas C1 and C2 can be measured or obtained by known methods.

[0039] like Figure 4 As shown in the embodiment, the chamfered surfaces 13a and 14a are surfaces formed by chamfering the corners formed by the opening ends 13 and 14 and the outer peripheral surface 11d at 45 degrees. Therefore, if the chamfering dimension of the chamfered surface 13a is x, the area C1 is expressed as C1=x 2 Similarly, if the chamfer dimension of the chamfered surface 14a is y, the area C2 is expressed as C2=y 2 / 2.

[0040] The chamfered surface 11e is a surface (outer peripheral lower surface chamfered surface) located between the side surface 11b and the outer peripheral surface 11d and connecting the side surface 11b and the outer peripheral surface 11d. The chamfered surface 11e is a surface formed by chamfering the corner formed by the outer peripheral surface 11d and the side surface 11b. An outer peripheral lower surface chamfered portion 18 is formed between the chamfered surface 11e and the inner surface 3a of the cylinder hole 3. The outer peripheral lower surface chamfered portion 18 is a gap equivalent to the portion removed from the main body 11 by chamfering the corner formed by the side surface 11b and the outer peripheral surface 11d. The area of ​​the outer peripheral lower surface chamfered portion 18 observed along the circumferential direction D3 is expressed as C3. The chamfered surface 11e is a surface formed by chamfering the corner formed by the outer peripheral surface 11d and the side surface 11b at an arbitrary angle (for example, 45 degrees), or a surface formed by R-chamfering the corner. As Figure 5As shown in (b), in this embodiment, the chamfered surface 11e is formed by chamfering the corner formed by the outer peripheral surface 11d and the side surface 11b at an arbitrary angle. In this case, if the dimension of the chamfered surface 11e along the axial direction D1 is zh and the dimension of the chamfered surface 11e along the radial direction D2 is za, the area C3 is expressed as C3 = zh × za / 2.

[0041] The dimension za of the outer lower chamfered portion 18 along the radial direction D2 may be smaller than the dimension zh of the outer lower chamfered portion 18 along the axial direction D1. When dimension za is smaller than dimension zh, excessive oil is less likely to intrude into the sliding surface B1. As a result, the oil scraping performance of the top ring 10 is improved. Dimension za may be less than 0.12 mm, less than 0.09 mm, or less than 0.06 mm. The lower limit of dimension za is not particularly limited. To prevent cracking of the hard film, dimension za may be greater than 0.02 mm. Even when the chamfered surface 11e is an R-chamfered surface, dimension za may be smaller than dimension zh.

[0042] like Figure 4 As shown, blowby gas G leaking from the top ring 10 passes through at least one of the opening 15, the opening chamfers 16 and 17, and the outer circumferential lower surface chamfer 18. The blowby gas G passing through the outer circumferential lower surface chamfer 18 includes blowby gas G1 passing through the outer circumferential lower surface chamfer 18a adjacent to the opening end 13, and blowby gas G2 passing through the outer circumferential lower surface chamfer 18b adjacent to the opening end 14. In this embodiment, the area of ​​the outer circumferential lower surface chamfer 18a and the area of ​​the outer circumferential lower surface chamfer 18b, as viewed along the circumferential direction D3, are each equal to area C3. Alternatively, the area of ​​the outer circumferential lower surface chamfer 18a and the area of ​​the outer circumferential lower surface chamfer 18b, as viewed along the circumferential direction D3, may differ.

[0043] The flow rate of blowby gas G varies depending on the opening flow area I. The opening flow area I is calculated based on the opening 15, opening chamfered portions 16 and 17, and outer circumferential lower surface chamfered portions 18a and 18b of the top ring 10, which is inserted into the cylinder bore 3 while mounted on the piston 2. The opening flow area I is the sum of the area of ​​the opening 15 as viewed along the axial direction D1, the area C1 of the opening chamfered portion 16 as viewed along the axial direction D1, the area C2 of the opening chamfered portion 17 as viewed along the axial direction D1, the area C3 of the outer circumferential lower surface chamfered portion 18a adjacent to the opening end 13, and the area C3 of the outer circumferential lower surface chamfered portion 18b adjacent to the opening end 14 as viewed along the circumferential direction D3.

[0044] like Figure 5As shown in (a), the gap between the outer surface 2a of the piston 2, to which the top ring 10 is attached, and the inner surface 3a of the cylinder bore 3, into which the top ring 10 is inserted, is represented by g1. Specifically, g1 is the value of (the inner diameter of the cylinder bore 3 - the diameter of the upper end of the second land of the piston 2) / 2. g1 can also be determined within a range of 0.05 mm to 0.5 mm.

[0045] In the present embodiment, the area of ​​the opening 15 when the top ring 10 is inserted into the cylinder hole 3 while being mounted on the piston 2 and viewed along the axial direction D1 is expressed as s1×g1. In this case, the gap s1 between the opening ends 13 and 14 is proportional to the diameter of the top ring 10, so a correction coefficient f is introduced. The correction coefficient f is the ratio of the inner diameter of the cylinder hole serving as a reference to the inner diameter of the cylinder hole 3 into which the top ring 10 is inserted. If the inner diameter of the cylinder hole serving as a reference under the correction coefficient f is set to X and the inner diameter of the cylinder hole 3 is set to Y, the correction coefficient f is expressed as f=X / Y. In the present embodiment, the inner diameter of the cylinder hole serving as a reference is set to φ80. Therefore, the correction coefficient f is expressed as f=80 / Y. The area of ​​the opening 15 into which the correction coefficient f is introduced is expressed as s1×g1×f. Therefore, the opening flow area I is expressed by the following mathematical formula. In the present embodiment, the opening flow area I of the top ring 10 is 0.1 mm 2 The opening flow area I of the top ring 10 may also be 0.07 mm 2 Below. The opening flow area I can be 0.05mm 2 Below, can also be 0.03mm 2 the following.

[0046] I=s1×g1×f+C1+C2+2×C3

[0047] When the area C31 of the outer peripheral lower surface chamfered portion 18a viewed along the circumferential direction D3 is different from the area C32 of the outer peripheral lower surface chamfered portion 18b viewed along the circumferential direction D3, 2×C3 is replaced by the sum of C31 and C32.

[0048] In the piston ring set 1 described above, the opening flow area of ​​the top ring 10 is 0.1 mm 2 Below, and the outer periphery followability coefficient of the oil ring 30 is 0.3 or more. The flow area through the opening is 0.1mm 2This reduces blowby gas G. However, as blowby gas G decreases, the amount of oil blown off by the blowby gas G decreases. Consequently, excess oil adhering to the inner surface 3a of the cylinder bore 3 tends to increase, and friction on the top ring 10 also tends to increase. The oil ring 30 has an outer circumference followability coefficient of 0.3 or greater, allowing the oil ring 30 to follow the inner surface 3a of the cylinder bore 3 well. Consequently, excess oil adhering to the inner surface 3a of the cylinder bore 3 caused by the top ring 10 is effectively scraped off by the oil ring 30. Consequently, when using a piston ring set 1 that includes both the top ring 10 and the oil ring 30, the reduction in oil consumption due to the oil ring 30 exceeds the increase in oil consumption due to the top ring 10. In other words, using the piston ring set 1 can reduce blowby gas G, oil consumption, and friction. In particular, friction in the piston ring set 1 that includes both the top ring 10 and the oil ring 30 can be reduced to the same degree as friction in the piston ring set that includes the oil ring 30.

[0049] In the case of a large opening flow area (greater than 0.1mm 2 In a piston ring set consisting of a top ring with a small opening clearance (0.1 mm), the S1 ratio decreases. In this case, the pressure of the second land increases due to blowby gas G, which can cause the top ring to vibrate. When the top ring vibrates, the amount of blowby gas G, oil consumption, and friction increase. 2 The combination of a top ring 10 (with an S1 ratio of 1.8 or less) and a second ring 20 having a small opening gap achieves a synergistic effect in suppressing chatter vibration of the top ring 10, even when the S1 ratio is 1.8 or less. As a result, the piston ring set 1 can effectively reduce the amount of blowby gas, oil consumption, and friction.

[0050] The present disclosure has been described in detail above based on its embodiments. However, the present disclosure is not limited to the above embodiments. Various modifications can be made to the present disclosure without departing from the scope of the present disclosure.

[0051] The oil rings are not limited to three. Two oil rings are also possible. The peripheral followability coefficient of the two oil rings is calculated based on the cross-sectional shape of the two oil rings. The opening chamfer and the outer peripheral lower surface chamfer are not limited to C-chamfers. The opening chamfer and the outer peripheral lower surface chamfer may each be R-chamfers. The S1 ratio is not limited to 1.8 or less.

[0052] The outer circumferential surface of the top ring may have a barrel-shaped, eccentric barrel-shaped, or conical shape. The cross-sectional shape of the second ring may have a scraper, balanced scraper, rapier, or balanced rapier shape. The outer circumferential surface of the second ring may have a conical, barrel-shaped, or eccentric barrel-shaped shape. The outer circumferential surface of the oil ring track may have a conical, barrel-shaped, eccentric barrel-shaped, or bullet-shaped shape. The oil ring may also have a barrel-shaped outer circumferential surface with a surface pressure of 0.35 MPa or greater.

[0053] Example

[0054] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to these examples.

[0055] Figures 6 to 9 The figures show the experimental results of the comparative examples or the examples respectively. Figures 6 to 9 The figures show oil consumption, blowby gas volume, and friction levels for internal combustion engines using various piston ring sets from the comparative example and the embodiment. The cylinder bore inner diameter of the engine was φ73. Oil consumption was measured under various operating conditions: "Low Speed, High Load" and "Pattern Conditions." In "Low Speed, High Load," oil consumption was measured under operating conditions (for example, 1000-2000 rpm at 100% load) during acceleration from a stop (idling) and on a slope. In "Pattern Conditions," oil consumption was measured under operating conditions assuming urban operation, repeating a cycle of engine stopping, idling, acceleration, deceleration, constant speed, acceleration, and deceleration.

[0056] exist Figures 6 to 9 In the experimental results of the comparative examples and examples shown respectively, the oil consumption (grams) per hour is measured as "Low-speed, high-load oil consumption [g / hr]" and "Model-condition oil consumption [g / hr]", the amount of blowby gas (liters) per minute is measured as "Low-speed, high-load blowby gas [L / min]", and the friction level (watts) is measured as "Model-condition friction [W]". The experimental results of the comparative examples and examples are shown in Figure 6 The relative evaluation values ​​for Comparative Example 1 shown in (a) are used as a benchmark. Specifically, the experimental results for "Low-Speed, High-Load Oil Consumption," "Mode-Condition Oil Consumption," "Low-Speed, High-Load Blow-Blow-On Gas," and "Mode-Condition Friction" in Comparative Example 1 are set to 1.00. The magnitudes of the experimental results for the Comparative Examples and Examples are expressed as a ratio relative to the experimental result for Comparative Example 1, which is 1.00.

[0057] exist Figures 6 to 9In the experimental results of the comparative examples and embodiments shown respectively, "low-speed high-load oil consumption" is represented by graph A located at the left end, "mode-condition oil consumption" is represented by graph B located second from the left end, "low-speed high-load blowby gas" is represented by graph C located third from the left end, and "mode-condition friction" is represented by graph D located fourth from the left end.

[0058] (Comparative Example 1)

[0059] In Comparative Example 1, the following piston ring set was used.

[0060] [Top ring E1] Material and surface treatment: steel + chromium nitride film Shape: Thickness 2.30mm × Width 1.00mm Tension: 3.0N Outer surface: barrel shape Cross-sectional shape: rectangular + inner bevel Opening gap: 0.25mm Opening chamfer: 0.15mm Chamfer of the lower peripheral surface (axial): 0.15mm Outer circumference lower surface chamfer (radial): 0.15mm Opening flow area: 0.113mm 2 [Calculation example: s1×g1×f+C1+C2+C3×2=0.25×0.25×80 / 73+0.15 2 / 2+0.15 2 / 2+0.15 2 / 2×2=0.113mm 2 ]

[0061] [Second Ring E1] Material and surface treatment: Steel + chemical conversion treatment Shape: Thickness 2.30mm × Width 1.00mm Tension: 2.5N Outer surface: tapered shape Cross-section shape: scraper Opening gap: 0.40mm

[0062] [Oil ring E1] Shape: Thickness 2.55mm × Width 2.00mm Tension: 15N Ear angle: 20° Track shape: Thickness 2.00mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Rail elastic modulus: 196GPa (196000N / mm 2 ) Track outer surface: barrel shape Sliding surface shape: b1=0.15, b2=0.014 Peripheral tracking coefficient 0.2 [Calculation example: 3 / 2×Ft×(d1-a1) 2 / (E×h12×a1 3 ) = 3 / 2 × 15 × (73-2.00) 2 / (196000×0.35×2.00 3 )≈0.20]

[0063] The split clearance can be measured by inserting a gap gauge into the split clearance while the piston ring assembly is inserted into the cylinder bore. The split chamfer and the outer lower surface chamfer can be measured based on the contour of the chamfered portion. The contour can be measured manually or using image processing software. Tension can be measured using a manual tensiometer or an automatic tensiometer. The rail shape (thickness x width) can be measured using a micrometer. The rail elastic modulus can be measured using the material's inherent value or through a tensile test of the metal.

[0064] Also like Figure 6 As shown in (a), the experimental results of Comparative Example 1 (low-speed, high-load oil consumption, model-condition oil consumption, low-speed, high-load blowby gas, and model-condition friction) are calculated as a reference of 1.00. The ear angle refers to the angle between the ear of the oil ring's spacer expander and the cylinder bore's axial direction. This ear is the end of the spacer expander that faces each rail in the cylinder bore's radial direction.

[0065] (Comparative Example 2)

[0066] In Comparative Example 2, the top ring is different from the structure of the piston ring set of Comparative Example 1. In Comparative Example 2, the following top ring is used.

[0067] [Top ring E2] Material and surface treatment: steel + chromium nitride film Shape: Thickness 2.30mm × Width 1.00mm Tension: 3.0N Outer surface: barrel shape Cross-sectional shape: rectangular + inner bevel Opening gap: 0.18mm Opening chamfer: 0.10mm Chamfer of the lower peripheral surface (axial): 0.10mm Outer lower surface chamfer (radial): 0.08mm Opening flow area: 0.067mm 2

[0068] The experimental results in Comparative Example 2 are as follows: Figure 6 as shown in (b). Low rotation and high load oil consumption: 1.10 Mode condition oil consumption: 0.85 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 1.00

[0069] (Comparative Example 3)

[0070] In Comparative Example 3, the oil ring is different from the structure of the piston ring set of Comparative Example 1. In Comparative Example 3, the following oil ring is used.

[0071] [Oil ring E2] Shape: Thickness 2.20mm × Width 2.00mm Tension: 15N Ear angle: 20° Track shape: Thickness 1.60mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Track outer surface: barrel shape Sliding surface shape: b1=0.15, b2=0.014 Peripheral tracking coefficient 0.4

[0072] The experimental results in Comparative Example 3 are as follows: Figure 6 As shown in (c). Low rotation and high load oil consumption: 0.70 Mode condition oil consumption: 0.85 Low rotation and high load blowby gas: 1.00 Mode Condition Friction: 0.85

[0073] (Example 1)

[0074] In Example 1, the top ring E2, the second ring E1, and the oil ring E2 are used as the piston ring set.

[0075] The experimental results in Example 1 are as follows: Figure 6 as shown in (d). Low rotation and high load oil consumption: 0.80 Mode condition oil consumption: 0.70 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.85

[0076] In Example 1, the opening flow area of ​​the top ring E2 is 0.1 mm 2 Below, and the outer periphery followability coefficient of the oil ring E2 is 0.3 or more. The opening flow area through the top ring E2 is 0.1mm 2 As a result, blowby can be reduced. With an outer periphery followability coefficient of 0.3 or greater, the oil ring E2 follows the inner surface of the cylinder bore well. Consequently, excess oil deposited on the inner surface of the cylinder bore by the top ring E2 is effectively scraped off by the oil ring E2. Consequently, when using the piston ring set of Example 1, the reduction in oil consumption due to the oil ring E2 exceeds the increase in oil consumption due to the top ring E2. In other words, using the piston ring set of Example 1 can reduce blowby, oil consumption, and friction. In particular, the friction of the piston ring set of Example 1, which includes both the top ring E2 and the oil ring E2, can be reduced to the same degree as that of the piston ring set of Comparative Example 3, which also includes the oil ring E2.

[0077] (Example 2)

[0078] In Example 2, the oil ring is different from the structure of the piston ring set of Example 1. In Example 2, the following oil ring is used.

[0079] [Oil Ring E3] Shape: Thickness 2.20mm × Width 2.00mm Tension: 15N Ear angle: 20° Track shape: Thickness 1.60mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Track outer surface: conical shape Sliding surface shape: t1=5.5°, t2=0.014, t3=0.075 Peripheral tracking coefficient 0.4

[0080] The experimental results in Example 2 are as follows: Figure 7 As shown in (a). Low rotation and high load oil consumption: 0.70 Mode condition oil consumption: 0.60 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.70

[0081] In Example 2, the outer peripheral surface of the oil ring has a tapered shape, thereby reducing oil consumption and friction compared to Example 1.

[0082] (Example 3)

[0083] In Example 3, the oil ring is different from the structure of the piston ring set of Example 1. In Example 3, the following oil ring is used.

[0084] [Oil Ring E4] Shape: Thickness 2.20mm × Width 2.00mm Tension: 15N Ear angle: 20° Track shape: Thickness 1.60mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Track outer surface: bullet shape Sliding surface shape: bt1=0.08, bt2=0.011 Peripheral tracking coefficient 0.4

[0085] The experimental results in Example 3 are as follows: Figure 7 as shown in (b). Low rotation and high load oil consumption: 0.60 Mode condition oil consumption: 0.65 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.75

[0086] In Example 3, the outer peripheral surface of the oil ring has a bullet-shaped surface, thereby reducing oil consumption and friction compared to Example 1.

[0087] (Comparative Example 4)

[0088] In Comparative Example 4, a piston ring set including a top ring E1 , a second ring E2 described below, and an oil ring E1 was used.

[0089] [Second Ring E2] Material and surface treatment: Steel + chemical conversion treatment Shape: Thickness 2.30mm × Width 1.00mm Tension: 2.5N Outer surface: tapered shape Cross-section shape: scraper Opening gap: 0.25mm

[0090] The experimental results in Comparative Example 4 are as follows: Figure 8 As shown in (a). Low rotation and high load oil consumption: 1.25 Mode condition oil consumption: 0.80 Low rotation and high load blowby gas: 1.15 Mode Condition Friction: 1.10

[0091] (Example 4)

[0092] In Example 4, a top ring E2, a second ring E2, and an oil ring E2 are used as the piston ring set.

[0093] The experimental results in Example 4 are as follows: Figure 8 as shown in (b).

[0094] Low rotation and high load oil consumption: 0.80 Mode condition oil consumption: 0.50 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.82

[0095] (Example 5)

[0096] In Example 5, the oil ring is different from the structure of the piston ring set of Example 4. In Example 5, the oil ring E3 is used.

[0097] The experimental results in Example 5 are as follows: Figure 8 As shown in (c). Low rotation and high load oil consumption: 0.70 Mode condition oil consumption: 0.40 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.67

[0098] (Example 6)

[0099] In Example 6, the oil ring is different from the structure of the piston ring set of Example 4. In Example 6, the oil ring E4 is used.

[0100] The experimental results in Example 6 are as follows: Figure 8 as shown in (d). Low rotation and high load oil consumption: 0.60 Mode condition oil consumption: 0.45 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.72

[0101] Compared with Comparative Example 1, in Comparative Example 4, low-speed high-load oil consumption, low-speed high-load blowby gas and mode condition friction are increased. The piston ring set of Comparative Example 4 is composed of a ring having a diameter greater than 0.1 mm. 2 Opening flow area (0.113mm 2) and a second ring E2 with an opening gap of less than 0.4 mm (0.25 mm). Therefore, the S1 ratio is less than 1.8 (s2 / s1 = 1.0). Therefore, it is speculated that the reason why the experimental results of Comparative Example 4 deteriorate compared to those of Comparative Example 1 is that under low rotation and high load conditions, the pressure of the second land increases due to blowby gas G, causing flutter in the top ring E1.

[0102] Each piston ring set of Examples 4 to 6 is composed of a ring having a ratio of 0.1 mm 2 Small opening flow area (0.069mm 2 ) and a second ring E2 with an opening gap smaller than 0.4 mm (0.25 mm). In Examples 4-6, even with an S1 ratio less than 1.8 (s2 / s1 ≈ 1.39), blowby, oil consumption, and friction were reduced compared to Comparative Example 4 or Comparative Example 1. The improved experimental results in Examples 4-6 compared to Comparative Example 4 or Comparative Example 1 are presumably due to the synergistic effect of the combination of the top ring E2 and the second ring E2 in suppressing flutter vibrations of the top ring E2.

[0103] (Comparative Example 5)

[0104] In Comparative Example 5, the oil ring is different from the structure of the piston ring set of Comparative Example 1. In Comparative Example 5, the following oil ring is used.

[0105] [Oil Ring E5] Shape: Thickness 2.20mm × Width 2.00mm Tension: 20N Ear angle: 20° Track shape: Thickness 1.60mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Track outer surface: barrel shape Sliding surface shape: b1=0.15, b2=0.014 Peripheral follow-up coefficient 0.54

[0106] The experimental results in Comparative Example 5 are as follows: Figure 9 As shown in (a). Low rotation and high load oil consumption: 0.55 Mode condition oil consumption: 0.70 Low rotation and high load blowby gas: 1.00 Mode Condition Friction: 0.95

[0107] (Comparative Example 6)

[0108] In Comparative Example 6, the oil ring is different from the structure of the piston ring set of Comparative Example 1. In Comparative Example 6, the following oil ring is used.

[0109] [Oil Ring E6] Shape: Thickness 2.20mm × Width 2.00mm Tension: 12N Ear angle: 20° Track shape: Thickness 1.35mm × Width 0.35mm Track material and surface treatment: steel + chromium nitride film Track outer surface: barrel shape Sliding surface shape: b1=0.15, b2=0.014 Peripheral follow-up coefficient 0.54

[0110] The experimental results in Comparative Example 6 are as follows: Figure 9 as shown in (b). Low rotation and high load oil consumption: 0.60 Mode condition oil consumption: 0.75 Low rotation and high load blowby gas: 1.00 Mode Condition Friction: 0.70

[0111] (Example 7)

[0112] In Example 7, the top ring E2, the second ring E1, and the oil ring E5 are used as the piston ring set.

[0113] The experimental results in Example 7 are as follows: Figure 9 As shown in (c). Low rotation and high load oil consumption: 0.65 Mode condition oil consumption: 0.55 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.95

[0114] (Example 8)

[0115] In Example 8, the top ring E2, the second ring E1, and the oil ring E6 are used as the piston ring set.

[0116] The experimental results in Example 8 are as follows: Figure 9 As shown in (d). Low rotation and high load oil consumption: 0.70 Mode condition oil consumption: 0.60 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.70

[0117] (Example 9)

[0118] exist Figure 9 In Example 9 shown in (e), a top ring E2, a second ring E2, and an oil ring E5 are used as the piston ring set.

[0119] The experimental results in Example 9 are shown below. Low rotation and high load oil consumption: 0.65 Mode condition oil consumption: 0.35 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.92

[0120] (Example 10)

[0121] In Example 10, the top ring E2, the second ring E2, and the oil ring E6 are used as the piston ring set.

[0122] The experimental results in Example 10 are as follows: Figure 9 As shown in (f). Low rotation and high load oil consumption: 0.70 Mode condition oil consumption: 0.40 Low rotation and high load blowby gas: 0.65 Mode Condition Friction: 0.67

[0123] In Example 7, the use of the oil ring E5, which has a tension of 20 N and a peripheral followability coefficient of 0.54, reduced oil consumption compared to Example 1. In Example 9, the use of the oil ring E5 reduced oil consumption compared to Example 4. In Example 8, the use of the oil ring E6, which has a tension of 12 N and a peripheral followability coefficient of 0.54, reduced oil consumption and friction compared to Example 1. In Example 10, the use of the oil ring E6 reduced oil consumption and friction compared to Example 4.

[0124] Label Description

[0125] 1…piston ring assembly; 2…piston; 2a…outer surface; 11d, 21d, 31d…outer circumferential surface; 3…cylinder bore; 3a…inner surface; 10…top ring; 11, 21…body; 11a…side surface (first side surface); 11b…side surface (second side surface); 11c, 21c, 31c…inner circumferential surface; 11e…outer circumferential lower chamfered surface; 13…opening end (first opening end); 13a…opening chamfered surface (first opening chamfered surface); 14…opening end (second opening end); 14a…opening chamfered surface (second opening chamfered surface); 15…opening portion; 16…opening chamfered portion (first opening chamfered portion); 17…opening chamfered portion (second opening chamfered portion); 18, 18a, 18b…outer peripheral lower surface chamfered portion; 20…second ring; 23…opening end portion (third opening end portion); 24…opening end portion (fourth opening end portion); 25…opening portion; 30…oil ring; 31…track; D1…axial direction; D2…radial direction.

Claims

1. A piston ring set comprising a top ring and an oil ring, which is inserted into a cylinder bore of an internal combustion engine while being mounted on a piston, wherein: The top ring has an annular main body, the annular main body including an inner peripheral surface, an outer peripheral surface, a first side surface and a second side surface substantially orthogonal to the inner peripheral surface, and a first opening end portion and a second opening end portion facing each other to form an opening portion. The oil ring has a pair of tracks facing each other. The opening flow area of ​​the top ring is 0.1mm 2 the following, The oil ring has an outer periphery followability coefficient of 0.3 or greater.

2. The piston ring set according to claim 1, wherein: The oil ring has an outer periphery followability coefficient of 0.8 or less.

3. The piston ring set according to claim 1, wherein: The main body is provided with a first opening chamfered surface, a second opening chamfered surface and a peripheral lower surface chamfered surface, the first opening chamfered surface is located between the first opening end and the peripheral surface, the second opening chamfered surface is located between the second opening end and the peripheral surface, and the peripheral lower surface chamfered surface is located between one of the first side surface and the second side surface and the peripheral surface. When the top ring and the oil ring are inserted into the cylinder hole in a state where they are mounted on the piston, A first opening chamfered portion is formed between the inner surface of the cylinder hole and the first opening chamfered surface, a second opening chamfered portion is formed between the inner surface and the second opening chamfered surface, and an outer peripheral lower surface chamfered portion is formed between the inner surface and the outer peripheral lower surface chamfered surface. When the gap between the first opening end and the second opening end is s1, the gap between the outer surface of the piston and the inner surface of the cylinder hole is g1, the correction coefficient based on the inner diameter of the cylinder hole is f, the size of the first opening chamfer is C1, the size of the second opening chamfer is C2, and the size of the outer peripheral lower surface chamfer is C3, the opening flow area is expressed as s1×g1×f+C1+C2+2×C3. When the tension of the oil ring is Ft, the inner diameter of the cylinder bore is d1, the thickness of each of the pair of rails along the radial direction of the cylinder bore is a1, the elastic modulus of the material constituting each of the pair of rails is E, and the width of each of the pair of rails along the axial direction of the cylinder bore is h12, the peripheral followability coefficient is expressed as 3 / 2×Ft×(d1-a1) 2 / (E×h12×a1 3 ).

4. The piston ring set according to claim 3, wherein: A dimension of the outer peripheral lower surface chamfered portion along the radial direction is smaller than a dimension of the outer peripheral lower surface chamfered portion along the axial direction.

5. The piston ring set according to any one of claims 1 to 4, wherein: The piston ring set also includes a second ring, The second ring has an annular second main body, the second main body including a third opening end and a fourth opening end facing each other to form a second opening. A ratio of a gap between the third opening end and the fourth opening end to a gap between the first opening end and the second opening end is 1.8 or less.

6. The piston ring set according to any one of claims 1 to 4, wherein: Each outer peripheral surface of the pair of rails has either a tapered surface shape or a bullet surface shape.

Images