oil control ring

Abstract

The oil control ring is a three-piece oil control ring having a pair of side rails and a spacer expander ring disposed between the pair of side rails. The spacer expander ring has a plurality of ears including an abutting surface that abuts an inner peripheral surface of the side rails, the Rz in a prescribed initial break-in state is 2.5 μm or less at the inner peripheral surface of the side rails, the Rz in the prescribed initial break-in state is 2.0 μm or less at the abutting surface of the ears, the side rails are composed of alloy steel, the Ni content of the side rails is 0.05 wt% or more and 0.60 wt% or less, the spacer expander ring is composed of alloy steel, and the Ni content of the spacer expander ring is 2.9 wt% or more and 16.1 wt% or less.

Description

Technical Field

[0001] This disclosure relates to oil control rings. Background Technology

[0002] In the past, in a three-piece oil control ring having a pair of side rails and a spacer ring disposed between the pair of side rails, the independent rotation of the side rails relative to the spacer ring could be a cause of increased oil consumption. For example, in the combined oil ring described in Patent Document 1, the inner circumferential surfaces of the two side rails are sandblasted with a surface roughness of 3~20 μmRz to prevent the side rails from rotating independently relative to the spacer ring.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-132840 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the aforementioned prior art, the surface roughness of the inner circumferential surface of the side rail increases due to sandblasting, which easily leads to increased wear on the lug of the spacer ring that abuts against the inner circumferential surface of the side rail. As a result, for example, it may cause a decrease in the tension of the oil control ring.

[0008] The purpose of this disclosure is to provide an oil control ring that can simultaneously suppress the individual rotation of the side rail relative to the spacer outer expansion ring and suppress wear between the inner circumferential surface of the side rail and the ear of the spacer outer expansion ring.

[0009] Methods for solving problems

[0010] One aspect of this disclosure is a three-piece oil control ring comprising a pair of side rails and a spacer outer expansion ring, wherein the spacer outer expansion ring is disposed between the pair of side rails, and the spacer outer expansion ring has a plurality of lugs, the plurality of lugs including a contact surface abutting against the inner circumferential surface of the side rails, wherein the Rz of the inner circumferential surface of the side rails under a specified initial break-in condition is less than 2.5 μm, and the Rz of the contact surface of the lugs under a specified initial break-in condition is less than 2.0 μm, the side rails are made of alloy steel, and the Ni content of the side rails is more than 0.05 wt% and less than 0.60 wt%, the spacer outer expansion ring is made of alloy steel, and the Ni content of the spacer outer expansion ring is more than 2.9 wt% and less than 16.1 wt%.

[0011] According to one aspect of the oil control ring disclosed herein, an oil control ring that satisfies all four conditions—a Ni content of 0.05 wt% or more and 0.60 wt% or less, a Ni content of 2.9 wt% or more and 16.1 wt% or less, an Rz of 2.5 μm or less at the inner circumferential surface of the side rail under a specified initial break-in condition, and an Rz of 2.0 μm or less at the abutment surface of the ear under a specified initial break-in condition—is less likely to experience independent rotation of the side rail relative to the outer circumferential ring. Furthermore, according to the oil control ring that satisfies all four conditions, compared to increasing the roughness of the inner circumferential surface of the side rail through processes such as sandblasting, it is easier to suppress increased wear on the ear of the outer circumferential ring abutting the inner circumferential surface of the side rail. Therefore, the oil control ring according to one aspect of the present disclosure can simultaneously suppress independent rotation of the side rail relative to the outer circumferential ring and suppress wear between the inner circumferential surface of the side rail and the ear of the outer circumferential ring.

[0012] In one embodiment, the Rpk value under a specified initial break-in condition may be less than the Rvk value under a specified initial break-in condition on the inner circumferential surface of the side rail. Alternatively, the Rpk value under a specified initial break-in condition may be greater than the Rvk value under a specified initial break-in condition on the abutment surface of the ear. Alternatively, the Rpk value under a specified initial break-in condition may be 0.51 μm or less and the Rvk value under a specified initial break-in condition may be 0.76 μm or less on the inner circumferential surface of the side rail, and the Rpk value under a specified initial break-in condition may be 0.75 μm or less and the Rvk value under a specified initial break-in condition may be 0.50 μm or less on the abutment surface of the ear. In this case, through the interaction of the height of the convex portion corresponding to Rpk on the inner circumferential surface of the side rail and the depth of the concave portion corresponding to Rvk on the ear, and the interaction of the depth of the concave portion corresponding to Rvk on the inner circumferential surface of the side rail and the height of the convex portion corresponding to Rpk on the ear, a meshing effect is generated, increasing the frictional force. This makes it easier to suppress the independent rotation of the side rail relative to the spacer ring and to easily reduce Rz on the inner circumferential surface of the side rail.

[0013] In one embodiment, the Ni content of the side rail may be 0.26 wt% or more and 0.49 wt% or less, and the Ni content of the spacer outer expansion ring may be 6.5 wt% or more and 11.1 wt% or less.

[0014] In one embodiment, the hardness of the base material of the side rail may be HV250 or higher and 620 or lower. Alternatively, the hardness of the base material of the side rail may be HV450 or higher and 620 or lower.

[0015] In one embodiment, the inclination angle of the contact surface of the ear may be 15° or more and 25° or less. Alternatively, the width of the contact surface of the ear may be 0.5 mm or more and 1.2 mm or less.

[0016] Invention Effects

[0017] According to one aspect of the oil control ring disclosed herein, it is possible to simultaneously suppress the individual rotation of the side rail relative to the spacer outer expansion ring and suppress wear between the inner circumferential surface of the side rail and the ear of the spacer outer expansion ring. Attached Figure Description

[0018] Figure 1 This is a top view showing the spaced outer expansion ring used in the oil control ring of the embodiment.

[0019] Figure 2 yes Figure 1 An enlarged 3D view of the area enclosed by dotted lines.

[0020] Figure 3 This is a cross-sectional view of the oil control ring installed in the piston groove.

[0021] Figure 4 This is a schematic diagram of a device used to evaluate the individual rotation of the side rails relative to the spacer ring. Detailed Implementation

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0023] Figure 1 This is a top view showing the spaced outer expansion ring used in the oil control ring of the embodiment. Figure 2 yes Figure 1 An enlarged 3D view of the area enclosed by a single-dotted line. Figure 3 This is a cross-sectional view of the oil control ring installed in the piston groove. Figure 3 Corresponding to along Figure 2 The cross section of the III-III line of the spaced outer expansion ring.

[0024] like Figures 1-3 As shown, the oil control ring 50 is a piston ring used to install in the groove Pa of the piston P. The oil control ring 50 is a three-piece oil control ring having a pair of side rails 1 and 2 and a spacer outer expansion ring 10 disposed between the pair of side rails 1 and 2. The side rails 1 and 2 are annular and have inner circumferential surfaces 1a and 2a. It should be noted that "annular" here does not necessarily mean a closed circle, and the side rails 1 and 2 may also have a joint. The cross-sectional shape of the side rails 1 and 2 is, for example, an arcuate surface shape in which the inner circumferential surfaces 1a and 2a are symmetrically curved vertically. The outer circumferential surface shape and the inner circumferential surface shape of the side rails may also be different from the side rails 1 and 2 of this embodiment, for example, they may not have to be. Figure 3The cross-sectional shape is symmetrical as shown. The outer peripheral surfaces of side rails 1 and 2 are in contact with the inner surface Ba of cylinder bore B.

[0025] The spacer outer expansion ring 10 is annular, for example, having a mortise portion 10c formed by two end faces 10a and 10b. The spacer outer expansion ring 10 has multiple ears 5, each ear including an abutting surface 5a that abuts against the inner circumferential surfaces 1a and 2a of the side rails 1 and 2. The spacer outer expansion ring 10 has multiple rail face portions 7 facing the side surfaces 1b and 2b of the side rails 1 and 2, respectively. The rail face portions 7 are formed at a position adjacent to and on the outer periphery of the ears 5. The ears 5 are formed to be higher than the rail face portions 7. The spacer outer expansion ring 10 has an opening 5h formed by the ears 5 and the rail face portions 7. When the side rails 1 and 2 are combined with the spacer outer expansion ring 10, the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 abut against the abutting surfaces 5a of the ears 5, and the rail face portions 7 face the side surfaces 1b and 2b of the side rails 1 and 2.

[0026] like Figure 2 As shown, the spacer outer expansion ring 10 has, for example, a shape in which peaks 10M and valleys 10V alternately connect when placed on a worktable. For example, the peaks 10M located in the spacer outer expansion ring 10 ( Figure 2 The upper part of the ear 5 and the valley part 10V (in the middle) Figure 2 The ear portion 5 (located on the lower side of the middle) has essentially the same shape. Similarly, the peak portion 10M located on the outer expansion ring 10 ( Figure 2 The upper side of the track surface 7 and the valley 10V (in the middle) Figure 2 The lower side of the track surface 7 is essentially the same shape. Therefore, if the spacer ring 10 placed on the worktable is turned upside down, Figure 2 The peak 10M shown becomes the valley 10V, and the valley 10V becomes the peak 10M.

[0027] The side rails 1 and 2 and the spacer outer expansion ring 10 will be described in detail. Hereinafter, the ear 5 and the abutment surface 5a of the peak 10M of the spacer outer expansion ring 10 will be described, while the description of the ear 5 and the abutment surface 5a of the valley 10V will be omitted.

[0028] Side rails 1 and 2 are made of alloy steel. The alloy steel is, for example, steel with added Ni. The lower limit of the Ni content in side rails 1 and 2 is set to a value that can suppress individual rotation of side rails 1 and 2 relative to the spacer outer expansion ring 10. The upper limit of the Ni content in side rails 1 and 2 can also be set, for example, to take into account the effect on the machinability of side rails 1 and 2. The upper limit of the Ni content in side rails 1 and 2 can also be set to take into account the cost of Ni.

[0029] Specifically, the Ni content of side rails 1 and 2 is 0.05 wt% or more and 0.60 wt% or less. The Ni content of side rails 1 and 2 can also be 0.26 wt% or more and 0.49 wt% or less. The Ni content of side rails 1 and 2 can be 0.10 wt% or more, 0.25 wt% or more, 0.26 wt% or more, or 0.30 wt% or more. The Ni content of side rails 1 and 2 can be 0.55 wt% or less, 0.49 wt% or less, 0.45 wt% or less, or 0.40 wt% or less.

[0030] The hardness of the base material of side rails 1 and 2 can be HV250 or higher and 620 or lower. Alternatively, the hardness can be HV450 or higher and 620 or lower. Or, the hardness can be HV500 or higher and 620 or lower. By setting these ranges for the hardness of the base material of side rails 1 and 2, wear on the inner circumferential surfaces 1a and 2a of side rails 1 and 2 can be suppressed, as can wear on the lugs 5 that abut against the inner circumferential surfaces 1a and 2a. Furthermore, considering the risk of breakage of side rails 1 and 2, the upper limit of the base material hardness can also be HV620. By suppressing wear on the inner circumferential surfaces 1a and 2a of side rails 1 and 2, the tension reduction of the oil control ring 50 is easily suppressed, and the deterioration of oil consumption is easily suppressed. It should be noted that side rails 1 and 2 can undergo surface treatments such as nitriding, or Parker treatment for rust prevention, or remain untreated.

[0031] The spacer expansion ring 10 is made of alloy steel. The alloy steel can be, for example, stainless steel with a Ni content of 8.0 wt% or more and 10.5 wt% or less. The Ni content of the spacer expansion ring 10 can also be 2.9 wt% or more and 16.1 wt% or less. Alternatively, the Ni content of the spacer expansion ring 10 can be 6.5 wt% or more and 11.1 wt% or less. The upper limit of the Ni content of the spacer expansion ring 10 can be set, for example, to take into account the influence on the machinability of the spacer expansion ring 10. The upper limit of the Ni content of the spacer expansion ring 10 can also be set to take into account the cost due to Ni. The spacer expansion ring 10 can be manufactured, for example, by stamping (bending and punching) a sheet of alloy steel. In the spacer expansion ring 10, for example, the surface treatment is set to untreated. Surface treatments such as nitriding can also be applied to the lugs 5 of the spacer expansion ring 10. If the wear of the lugs 5 is suppressed by nitriding, the tension reduction of the oil control ring 50 is easily suppressed.

[0032] In the spacer outer expansion ring 10, the abutment surface 5a of the ear 5 is a generally rectangular plane extending radially intersecting the spacer outer expansion ring 10. For example, no protrusions or recesses are provided on the abutment surface 5a. The abutment surface 5a is an inclined surface inclined at a predetermined angle relative to the axial direction of the spacer outer expansion ring 10. The inclination angle of the abutment surface 5a can be, for example, 15° or more and 25° or less, or 18° or more and 22° or less. By inclining the abutment surface 5a at this angle, it is easy to suppress the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10. When the inclination angle of the abutment surface 5a is within the above range, for example, when the oil control ring 50 is installed in the groove Pa of the piston P, the side of the side rails 1 and 2 opposite to the side surfaces 1b and 2b is easily pressed against the upper or lower surface of the groove Pa. Therefore, friction is generated between the side surface opposite to the side surfaces 1b and 2b and the upper or lower surface of the groove Pa, easily suppressing the individual rotation of the side rails 1 and 2. If the inclination angle of the contact surface 5a is less than the lower limit of the aforementioned range, the aforementioned friction is unlikely to occur. To properly utilize the function of the oil control ring 50, the upper limit of the aforementioned range of inclination angles of the contact surface 5a can also be set to a value that makes it difficult for the side rails 1 and 2 to mount the upper surface of the upper ear portion 5 or the lower surface of the lower ear portion 5. The width of the contact surface 5a can, for example, be 0.5 mm or more and 1.2 mm or less, 0.55 mm or more and 1.0 mm or less, or 0.6 mm or more and 0.8 mm or less. The width of the contact surface 5a refers to the dimension of the contact surface 5a along a direction orthogonal to the radial direction of the spacer outer expansion ring 10 (the circumferential direction of the spacer outer expansion ring 10 or along the tangential direction of that circumferential direction). By making the width of the contact surface 5a of the ear portion 5 0.5 mm or more, the retention of the side rails 1 and 2 is less likely to be reduced. By making the width of the contact surface 5a of the ear 5 less than 1.2 mm, the reduction of the surface pressure applied to the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 is suppressed, and individual rotation is easily suppressed.

[0033] From the viewpoint of suppressing the individual rotation of the side rails 1 and 2 relative to the spacer ring 10, the roughness of the inner circumferential surfaces 1a and 2a and the roughness of the contact surface 5a of the ear 5 are configured to be within a certain range under a specified initial running-in condition.

[0034] The specified initial break-in state refers to the state in which the surface roughness of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the contact surface 5a of the ear 5 stabilizes after a certain degree of sliding during the initial use of the oil control ring 50. The specified initial break-in state can be, for example, the state after the engine equipped with the oil control ring 50 has actually undergone a specified break-in operation, or the state after a test using a device simulating engine break-in operation. The specified initial break-in state generally does not mean the unused state of the oil control ring 50 immediately after manufacturing, but it may include the unused state of the oil control ring 50 if, for example, the manufacturer defines the state of surface roughness stabilization after the aforementioned certain degree of sliding as an "unused state." As a state of surface roughness stabilization after a certain degree of sliding, for example, in the case of Parker treatment for rust prevention, it can also refer to the state where the surface roughness becomes the roughness of the base material after Parker treatment wear. As an example, it can also be the state after the evaluation test shown in the "Evaluation of Individual Rotation and Tension Reduction" in the embodiments described later.

[0035] On the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the Rz under the specified initial running-in condition is 2.5 μm or less. Rz is determined using a stylus-type surface roughness tester to measure the maximum height Rz of the roughness curve specified in JIS B0601:2001. On the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the Rz under the specified initial running-in condition can be 2.0 μm or less, 1.75 μm or less, or 1.5 μm or less. Such Rz on the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 is considered small compared to cases where the roughness of the inner circumferential surfaces of the side rails is increased, for example, through sandblasting. Therefore, wear on the lug 5 of the spacer ring 10, which abuts against the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, is easily suppressed.

[0036] On the inner circumferential surfaces 1a and 2a of side rails 1 and 2, Rpk under the specified initial break-in condition is less than Rvk under the specified initial break-in condition. Rpk is the height of the protruding peak (height of the convex part) Rpk as specified in JIS B0671-2:2002, measured using a stylus-type surface roughness testing machine. Rvk is the height of the protruding valley (depth of the concave part) Rvk as specified in JIS B0671-2:2002, measured using a stylus-type surface roughness testing machine.

[0037] On the inner circumferential surfaces 1a and 2a of side rails 1 and 2, the Rpk value under the specified initial running-in condition can be 0.55 μm or less, 0.45 μm or less, or 0.30 μm or less. From the viewpoint of preventing wear, the Rvk value on the inner circumferential surfaces 1a and 2a of side rails 1 and 2 under the specified initial running-in condition can be 0.80 μm or less, 0.70 μm or less, or 0.55 μm or less. From the viewpoint of suppressing the individual rotation of side rails 1 and 2 relative to the spacer outer expansion ring 10, the Rvk value on the inner circumferential surfaces 1a and 2a of side rails 1 and 2 under the specified initial running-in condition can also be 0.01 μm or more. From the viewpoint of suppressing the individual rotation of side rails 1 and 2 relative to the spacer outer expansion ring 10, the ratio Rvk / Rpk of the inner circumferential surfaces 1a and 2a of side rails 1 and 2 can be 1.25 or more, 1.45 or more, or 1.75 or more. As an example, on the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the specified Rpk under the initial running-in condition is less than 0.51 μm, and the specified Rvk under the initial running-in condition is less than 0.76 μm.

[0038] On the contact surface 5a of the ear portion 5 of the spacer outer expansion ring 10, the specified initial break-in condition Rz is 2.0 μm or less. On the contact surface 5a of the ear portion 5, the specified initial break-in condition Rz can be 1.75 μm or less, 1.5 μm or less, or 1.25 μm or less.

[0039] On the contact surface 5a of the ear portion 5, the Rpk value under the specified initial break-in condition is greater than the Rvk value under the specified initial break-in condition. From the viewpoint of preventing wear, the Rpk value under the specified initial break-in condition on the contact surface 5a of the ear portion 5 can be 0.75 μm or less, 0.60 μm or less, 0.55 μm or less, or 0.50 μm or less. From the viewpoint of suppressing the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10, the Rpk value under the specified initial break-in condition can also be 0.01 μm or more. On the contact surface 5a of the ear portion 5, the Rvk value under the specified initial break-in condition can be 0.50 μm or less, 0.30 μm or less, or 0.20 μm or less. From the viewpoint of suppressing the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10, the ratio Rpk / Rvk of the contact surface 5a of the ear portion 5 can be 1.3 or more, 1.6 or more, or 1.8 or more. As an example, the Rpk of the contact surface 5a of the ear portion 5 under the specified initial break-in condition is 0.75 μm or less, and the Rvk under the specified initial break-in condition is 0.50 μm or less.

[0040] However, in a three-piece oil control ring system, a set of oil control rings is formed by a pair of side rails clamping a spacer outer expansion ring. Normally, the three oil control rings are mounted in the piston groove, and within this groove, they can rotate circumferentially as a single set of oil control rings. However, depending on the combination of the side rail material, the surface treatment of the side rails, and the surface treatment of the spacer outer expansion ring, sometimes the side rails may rotate independently relative to the spacer outer expansion ring (independent rotation). If independent rotation of the side rails relative to the spacer outer expansion ring occurs, the circumferential positions of the mating portions of the upper and lower pairs of side rails may sometimes align. In this case, engine oil tends to rise into the combustion chamber, and oil consumption may sometimes increase.

[0041] Regarding this, the oil control ring 50 of this embodiment satisfies all of the following four conditions: the Ni content of the side rails 1 and 2 is 0.05wt% or more and 0.60wt% or less; the Ni content of the spacer outer expansion ring 10 is 2.9wt% or more and 16.1wt% or less; the Rz at the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 under the specified initial running-in condition is 2.5μm or less; and the Rz at the abutment surface 5a of the ear portion 5 under the specified initial running-in condition is 2.0μm or less. Compared with an oil control ring that does not satisfy at least one of the above four conditions, the oil control ring 50 is less likely to cause individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10. In addition, according to the oil control ring 50, compared with increasing the roughness of the inner circumferential surface of the side rails, for example by sandblasting, it is easier to suppress the increase of wear on the ear portion 5 of the spacer outer expansion ring 10 that abuts against the inner circumferential surfaces 1a and 2a of the side rails 1 and 2. Therefore, according to the oil control ring 50, it is possible to simultaneously suppress the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10 and suppress the wear of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 with the ear portion 5 of the spacer outer expansion ring 10.

[0042] On the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the Rpk under the specified initial break-in condition is less than the Rvk under the specified initial break-in condition. On the abutting surface 5a of the ear portion 5, the Rpk under the specified initial break-in condition is greater than the Rvk under the specified initial break-in condition. On the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the Rpk under the specified initial break-in condition is 0.51 μm or less, and the Rvk under the specified initial break-in condition is 0.76 μm or less. On the abutting surface 5a of the ear portion 5, the Rpk under the specified initial break-in condition is 0.75 μm or less, and the Rvk under the specified initial break-in condition is 0.50 μm or less. According to this structure, through the interaction of the height of the protrusion corresponding to Rpk of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the depth of the concave portion corresponding to Rvk of the abutment surface 5a of the ear 5, and the interaction of the depth of the concave portion corresponding to Rvk of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the height of the protrusion corresponding to Rpk of the abutment surface 5a of the ear 5, a mutual meshing effect is generated, and the frictional force is increased. This suppresses the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10, and easily reduces Rz of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2. Furthermore, the ratio Rvk / Rpk of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 can be 1.25 or more, 1.45 or more, or 1.75 or more. By increasing the Rvk / Rpk ratio of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2, the aforementioned meshing effect is easily achieved. Furthermore, the ratio Rpk / Rvk of the abutment surface 5a of the ear 5 can be 1.3 or higher, 1.6 or higher, or 1.8 or higher. By increasing the Rpk / Rvk ratio of the abutment surface 5a of the ear 5, the aforementioned meshing effect is easily achieved.

[0043] Furthermore, by adding Ni to the side rails 1 and 2, the affinity between the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the contact surface 5a of the ear 5 can be improved. Affinity refers to the effect that the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the contact surface 5a of the ear 5 are less likely to slide due to the presence of a certain amount of Ni in the side rails 1 and 2 and the spacer outer expansion ring 10 (the so-called homogeneous alloy effect). With this improved affinity, it is expected that the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the contact surface 5a of the ear 5 will be broken in earlier in the initial use of the oil control ring 50. In addition to the increased friction caused by the aforementioned mutual meshing, the earlier break-in of the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 and the contact surface 5a of the ear 5 makes it easier to suppress the individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10.

[0044] The Ni content of side rails 1 and 2 can also be 0.26 wt% or more and 0.49 wt% or less. The Ni content of the spacer outer expansion ring 10 can also be 6.5 wt% or more and 11.1 wt% or less. By setting the Ni content to such a level, the improved affinity described above can be further expected.

[0045] The hardness of the base material of side rails 1 and 2 can also be HV250 or higher and 620 or lower. Alternatively, the hardness of the base material of side rails 1 and 2 can be HV450 or higher and 620 or lower. By setting the hardness of the base material of side rails 1 and 2 within such a range, wear on the inner circumferential surfaces 1a and 2a of side rails 1 and 2 can be suppressed, as can wear on the ear portion 5 that abuts against the inner circumferential surfaces 1a and 2a.

[0046] The inclination angle of the contact surface 5a of the ear 5 can be 15° or more and 25° or less, or 18° or more and 22° or less. Furthermore, the width of the contact surface 5a of the ear 5 can be 0.5 mm or more and 1.2 mm or less, 0.55 mm or more and 1.0 mm or less, or 0.6 mm or more and 0.8 mm or less. By making the width of the contact surface 5a of the ear 5 0.5 mm or more, the retention of the side rails 1 and 2 is less likely to decrease. By making the width of the contact surface 5a of the ear 5 1.2 mm or less, the reduction of surface pressure applied to the inner circumferential surfaces 1a and 2a of the side rails 1 and 2 is suppressed, and individual rotation is easily suppressed. With this structure of the contact surface 5a, it is possible to reliably suppress individual rotation of the side rails 1 and 2 relative to the spacer outer expansion ring 10.

[0047] The embodiments of this disclosure have been described in detail above, but this disclosure is not limited to the above embodiments.

[0048] In the above embodiment, the cross-sectional shape of the side rails 1 and 2 is an arc surface shape with the inner circumferential surfaces 1a and 2a curved symmetrically from top to bottom, but it is not limited to this. The inner circumferential surfaces 1a and 2a can also be asymmetrical from top to bottom, or they can be shapes other than arc surfaces such as conical cross-sections, and can be set to conventionally known shapes.

[0049] In the above embodiments, all the ear parts 5 are substantially the same shape, but they do not necessarily have to be substantially the same shape.

[0050] Example

[0051] (Examples 1-8)

[0052] Prepare a spacer expansion ring made of Ni-added steel and a pair of side rails made of Ni-added steel. An oil control ring (nominal diameter: 80.5 mm, combined width: 2.0 mm, combined thickness: 2.25 mm) was manufactured to meet all four of the following conditions: The Ni content of the side rails is 0.05 wt% or more and 0.60 wt% or less; the Ni content of the spacer expansion ring is 2.9 wt% or more and 16.1 wt% or less; the inner circumferential surface Rz of the side rails under the specified initial break-in condition is 2.5 μm or less; and the contact surface of the ear portion under the specified initial break-in condition has an Rz of 2.0 μm or less. Using a stylus-type surface roughness testing machine, the maximum height Rz of the roughness curve specified in JIS B0601:2001, the height of the protruding peak (height of the convex portion) Rpk specified in JIS B0671-2:2002, and the height of the protruding valley (depth of the concave portion) Rvk specified in JIS B0671-2:2002 were measured. However, due to the short measurable portion, the measurement was performed using an evaluation length of 0.4 mm instead of the specified evaluation length. In the oil control rings of Examples 1 to 8, the Ni content of the side rails, the hardness HV of the base material of the side rails, the Rz, Rpk, and Rvk of the inner circumferential surface are shown in Table 1. In the oil control rings of Examples 1 to 8, the Ni content of the spacer outer expansion ring, the hardness HV of the base material of the spacer outer expansion ring, the Rz, Rpk, and Rvk of the abutment surface of the ear are shown in Table 1.

[0053] (Comparative Examples 1-5)

[0054] An oil control ring (nominal diameter: 80.5 mm, combined width: 2.0 mm, combined thickness: 2.25 mm) was fabricated using Ni-added steel spacer expansion rings and a pair of Ni-added steel side rails, but did not meet at least one of the following four conditions: The Ni content of the side rails was 0.05 wt% or more and 0.60 wt% or less; the Ni content of the spacer expansion ring was 2.9 wt% or more and 16.1 wt% or less; the inner circumferential surface Rz of the side rails under the specified initial running-in condition was 2.5 μm or less; and the abutment surface of the ear portion under the specified initial running-in condition had an Rz of 2.0 μm or less. Rz, Rpk, and Rvk were measured using a stylus-type surface roughness tester. However, due to the short measurable portion, the measurement was performed using an evaluation length of 0.4 mm instead of the specified evaluation length. In the oil control rings of Comparative Examples 1-5, the Ni content of the side rails, the hardness HV of the base material of the side rails, the Rz, Rpk, and Rvk of the inner circumferential surface are shown in Table 1. In the oil control rings of Comparative Examples 1-5, the Ni content of the spacer outer expansion ring, the hardness HV of the base material of the spacer outer expansion ring, the Rz, Rpk, and Rvk of the abutment surface of the ear are shown in Table 1.

[0055] <Evaluation of individual rotation and tension reduction>

[0056] use Figure 4 The apparatus shown is used to evaluate the individual rotation of the side rails relative to the spacer ring. Figure 4 The illustrated device 100 is used to mount an oil control ring on a bracket (simulated piston) 102 having a simulated oil ring groove 101, and to perform a swaying motion within a cylinder (simulated cylinder) 103 around a fulcrum 105 provided on a support 104, thereby evaluating the individual rotation of the side rail. Furthermore, the central axis of the bracket 102 is offset from the central axis of the cylinder 103. This allows for evaluation under more stringent conditions compared to the case where the central axes are not offset.

[0057] In the experiment, the oil control ring was first installed on the bracket 102 by assembling the upper and lower side rails, which were offset 30° from the joint of the outer expansion ring relative to the joint of the spacer outer expansion ring. The experiment was conducted by rotating the side rails at a speed of 10 reciprocating movements per second for 10 minutes, with the oscillation angle α ranging from 0.5° to 7.5° in increments of 0.5°. The ability to prevent individual rotation of the side rails was evaluated based on the magnitude of the oscillation angle caused by the individual rotation of the side rails. It was determined that the larger the oscillation angle caused by the individual rotation of the side rails, the easier it was to suppress the individual rotation of the side rails relative to the outer expansion ring. The results of the evaluation experiment are shown in Table 1.

[0058] [Table 1]

[0059] As shown in Table 1, in the oil control rings of Examples 2, 4, 6-8, the yaw angle α caused by the individual rotation of the side rail is 7.0° or more (Judgment A). In the oil control rings of Examples 1, 3, and 5, the yaw angle α caused by the individual rotation of the side rail is 5.5° or more and less than 7.0° (Judgment B). In Examples 1-8, the tension reduction (tension reduction rate) of the oil control ring is 6% or less. In particular, in Examples 6 and 8, the tension reduction rate of the oil control ring is 3%. In addition, the tension reduction rate is (ring tension before test - ring tension after test) / ring tension before test × 100 (%). Here, the term "test" in "before test" and "after test" refers to the evaluation test shown in the "Evaluation of Individual Rotation and Tension Reduction" of this example.

[0060] On the other hand, in the oil control rings of Comparative Examples 1-4, the head-shaking angle α caused by the independent rotation of the side rail was less than 5.5° (judgment C). In the oil control ring of Comparative Example 5, the head-shaking angle α caused by the independent rotation of the side rail was 7.5°, but the tension reduction rate of the oil control ring was 11%. The Rz of the side rail of the oil control ring of Comparative Example 5 was as large as 5.53, so it was considered unfavorable for suppressing wear between the inner circumferential surface of the side rail and the ear of the spacer outer expansion ring. Therefore, compared with the oil control rings of Comparative Examples 1-5, the oil control rings of Examples 1-8 can simultaneously suppress the independent rotation of the side rail relative to the spacer outer expansion ring and suppress wear between the inner circumferential surface of the side rail and the ear of the spacer outer expansion ring.

[0061] Furthermore, the constituent elements of various methods disclosed herein are described below. [1]

[0063] An oil control ring is a three-piece oil control ring comprising a pair of side rails and a spacer outer expansion ring, wherein the spacer outer expansion ring is disposed between the pair of side rails. The spacer ring has multiple lugs, each lug including an abutting surface that abuts against the inner circumferential surface of the side rail. On the inner circumferential surface of the side rail, the specified initial break-in condition has an Rz of less than 2.5 μm. On the contact surface of the ear, the Rz under the specified initial break-in condition is less than 2.0 μm. The side rail is made of alloy steel, and the Ni content of the side rail is above 0.05wt% and below 0.60wt%. The spacer outer expansion ring is made of alloy steel, and the Ni content of the spacer outer expansion ring is more than 2.9 wt% and less than 16.1 wt%. [2]

[0065] According to the oil control ring described in [1], Rpk in the specified initial break-in state is less than Rvk in the specified initial break-in state on the inner circumferential surface of the side rail. [3]

[0067] According to the oil control ring described in [1] or [2], wherein, on the abutting surface of the ear, Rpk under the specified initial break-in condition is greater than Rvk under the specified initial break-in condition. [4]

[0069] According to the oil control ring described in [3], on the inner circumferential surface of the side rail, the Rpk under the specified initial break-in condition is less than 0.51 μm, and the Rvk under the specified initial break-in condition is less than 0.76 μm. On the contact surface of the ear, the Rpk under the specified initial break-in condition is less than 0.75 μm, and the Rvk under the specified initial break-in condition is less than 0.50 μm. [5]

[0071] According to any one of [1] to [4], the oil control ring, wherein the Ni content of the side rail is 0.26wt% or more and 0.49wt% or less, The Ni content of the spacer ring is 6.5 wt% or more and 11.1 wt% or less. [6]

[0073] According to any one of [1] to [5], the oil control ring wherein the hardness of the base material of the side rail is above HV250 and below 620. [7]

[0075] According to the oil control ring described in [6], the hardness of the base material of the side rail is above HV450 and below 620. [8]

[0077] According to any one of [1] to [7], the oil control ring wherein the inclination angle of the abutting surface of the ear is 15° or more and 25° or less. [9]

[0079] According to any one of [1] to [8], the width of the abutting surface of the ear is 0.5 mm or more and 1.2 mm or less.

[0080] Industrial applicability

[0081] According to this disclosure, an oil control ring is provided, which can simultaneously suppress the individual rotation of the side rail relative to the spacer outer expansion ring and suppress the wear between the inner circumferential surface of the side rail and the ear of the spacer outer expansion ring.

[0082] Label Explanation

[0083] 1, 2…side rails, 1a, 2a…inner circumferential surfaces, 5…ear, 5a…abutment surface, 10…spaced outer expansion ring, 50…oil control ring.

Claims

1. An oil control ring, comprising three oil control rings having a pair of side rails and a spacer outer expansion ring, wherein the spacer outer expansion ring is disposed between the pair of side rails, wherein, The spacer ring has multiple lugs, each lug including an abutting surface that abuts against the inner circumferential surface of the side rail. On the inner circumferential surface of the side rail, the specified initial break-in condition has an Rz of less than 2.5 μm. On the contact surface of the ear, the Rz under the specified initial break-in condition is less than 2.0 μm. The side rail is made of alloy steel, and the Ni content of the side rail is above 0.05wt% and below 0.60wt%. The spacer outer expansion ring is made of alloy steel, and the Ni content of the spacer outer expansion ring is more than 2.9 wt% and less than 16.1 wt%.

2. The oil control ring according to claim 1, wherein, On the inner circumferential surface of the side rail, Rpk under the specified initial break-in condition is less than Rvk under the specified initial break-in condition.

3. The oil control ring according to claim 1 or 2, wherein, On the contact surface of the ear, Rpk under the specified initial break-in condition is greater than Rvk under the specified initial break-in condition.

4. The oil control ring according to claim 3, wherein, The inner circumferential surface of the side rail has an Rpk of less than 0.51 μm and an Rvk of less than 0.76 μm under the specified initial break-in conditions. The contact surface of the ear portion has an Rpk of less than 0.75 μm and an Rvk of less than 0.50 μm under the specified initial break-in condition.

5. The oil control ring according to claim 1 or 2, wherein, The Ni content of the side rail is above 0.26wt% and below 0.49wt%. The Ni content of the spacer ring is 6.5 wt% or more and 11.1 wt% or less.

6. The oil control ring according to claim 1 or 2, wherein, The base material of the side rail has a hardness of HV250 or higher and 620 or lower.

7. The oil control ring according to claim 6, wherein, The base material of the side rail has a hardness of HV450 or higher and 620 or lower.

8. The oil control ring according to claim 1 or 2, wherein, The angle of inclination of the contact surface of the ear is more than 15° and less than 25°.

9. The oil control ring according to claim 1 or 2, wherein, The width of the contact surface of the ear is 0.5 mm or more and 1.2 mm or less.

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