JP2011075092A - Combined oil ring for internal combustion engine, and assembling structure thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combined oil ring capable of reducing oil consumption in a low speed and high negative pressure state, and to provide fitting structure thereof. <P>SOLUTION: The combined oil ring 10 provided in the periphery of a piston and to be installed in a ring groove includes: an oil ring body 11 formed by connecting two of an upper and a lower rail parts 1 and 2, of which outer peripheral ends 6 and 7 protrude outward X1 in the radial direction, in a connection part 3; and a coil expander 12 arranged in an inner peripheral groove 4 in a central part inside in the radial direction of the connection part 3 to push the oil ring body 11 for energization outward in the radial direction. In this oil ring 10, a tension ratio is set at 0.05-0.3 N/mm, a radial directional width a1 of the oil ring body 11 is 0.7-0.9 times the axial directional width h1, depth d1 of the inner groove 4 formed by inner peripheral ends 8 and 9 of the rail parts 1 and 2 and the radial directional bottom part 4' is 0.35-0.50 times the radial directional width a1, and the diameter d2 of the coil expander 12 is less than twice the depth d1 of the inner peripheral groove 4. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a combined oil ring for an internal combustion engine and an assembly structure thereof, and more particularly to a combined oil ring for an internal combustion engine and an assembly structure thereof that can reduce oil consumption in a low rotation and high negative pressure state.

  Generally, in an internal combustion engine, a plurality of cylinders are provided, and a piston is supported by each cylinder so as to be movable up and down. A plurality of ring grooves are provided on the outer periphery of the piston, and a piston ring is mounted in the ring groove. Such piston rings include a pressure ring such as a top ring and a second ring mounted on the upper side, and an oil ring mounted on the lower side of the pressure ring. The pressure ring has a gas sealing function and a heat transfer function, while the oil ring forms a suitable oil film on the cylinder inner wall surface, and therefore, functions to scrape off excess oil adhering to the cylinder inner wall surface. And has a function of maintaining oil sealability.

  The oil ring increases the tension (the force that expands the ring radially outward) with respect to the pressure ring, thereby supplying the required minimum amount of oil to the cylinder inner wall surface and scraping off excess oil. Has the function of collecting (oil control function). Various forms such as a two-piece type oil ring and a three-piece type oil ring are known as the oil ring (for example, Patent Documents 1 and 2).

  As shown in Patent Document 1 and Patent Document 2, the two-piece type oil ring is a ring main body in which a pair of rail portions are integrally formed, and is arranged at the center in the axial direction on the inner side of the ring main body. An oil ring is composed of a coil expander that urges radially outward, and the outer peripheral ends of the pair of rail portions are in sliding contact with the inner wall surface of the cylinder. In this two-piece type oil ring, while the piston in the cylinder moves toward the bottom dead center, the upper rail portion slides in contact with the upper surface of the ring groove, while the piston in the cylinder While moving toward the top dead center, the lower rail portion slides in contact with the lower surface of the ring groove.

  In addition, the two-piece type oil ring shown in Patent Document 1 and Patent Document 2 has not been studied at all for an increase in oil consumption that occurs when the internal combustion engine is operated under low rotation and high negative pressure conditions.

JP-A 61-45172 Japanese Patent Laid-Open No. 4-95664

  In recent years, due to the demand for low friction, two-piece type oil rings are becoming lighter and tend to be lower in tension. The oil consumption when operating the internal combustion engine under the conditions of low rotation and high negative pressure under the light weight and low tension situation of these two-piece type oil rings is because the inertia force applied to the piston ring is small. Due to the influence of oil adhesion, the oil ring should be seated on the lower surface of the ring groove during the intake / explosion stroke, which should be seated on the upper surface of the ring groove, compared to when operating under high to medium rotation and high negative pressure conditions. Is expected to increase (prone to consume oil). However, there was not enough consideration on this point.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a two-piece type oil ring for an internal combustion engine that can reduce oil consumption in a low rotation and high negative pressure state (hereinafter, referred to as “oil ring”). It is referred to as “combined oil ring for internal combustion engine”) and an assembly structure thereof.

  The combined oil ring for an internal combustion engine according to the present invention for solving the above-described problems includes an oil ring main body in which two upper and lower rail portions whose outer peripheral ends project radially outward are connected by a connecting portion, and the diameter of the connecting portion. An internal combustion engine that is disposed in an inner circumferential groove formed in the center in the direction and is a coil expander that presses and urges the oil ring body radially outward, and is mounted in a ring groove provided on the outer periphery of the piston. In the combined oil ring for engines, (1) a tension ratio obtained by dividing the tension of the combined oil ring by the inner diameter of the cylinder to which the piston is assembled is 0.05 N / mm or more and 0.3 N / mm or less, and (2) the oil The ring body has a radial width not less than 0.7 times and not more than 0.9 times the axial width, and (3) the inner portion configured by an inner peripheral end of the rail portion and a radial bottom portion of the inner peripheral groove. The depth of the circumferential groove Or less 0.50 times 0.35 times more Ki径 width, (4) the diameter of the coil expander is less than 2 times the depth of the inner peripheral groove, characterized in that.

  An assembly structure of a combined oil ring for an internal combustion engine according to the present invention for solving the above-described problem is a cylinder in which the combined oil ring for an internal combustion engine according to the present invention is mounted in a ring groove provided on the outer periphery of a piston. It is characterized by being assembled inside.

  In the assembly structure of the combined oil ring for an internal combustion engine according to the present invention, the radial width of the oil ring body is a1, the diameter between the outer peripheral ends of the lower surface of the ring groove is D1, and the inner diameter of the cylinder is D2. [{A1- (D2-D1) / 2} / a1 × 100] (%) is 50% or more and 75% or less.

  According to the combined oil ring for an internal combustion engine and the assembled structure thereof according to the present invention, oil consumption can be reduced in a low rotation and high negative pressure state.

It is a typical perspective view which shows the typical example of the combination oil ring for internal combustion engines which concerns on this invention. It is typical sectional drawing which shows the representative example of the combination oil ring for internal combustion engines which concerns on this invention. FIG. 3 is a schematic cross-sectional view showing an assembly structure in which the combined oil ring for an internal combustion engine shown in FIG. 2 is attached to a ring groove provided on the outer periphery of a piston and attached to a cylinder inner wall surface. FIG. 6 is a schematic cross-sectional view showing another embodiment of the combined oil ring for an internal combustion engine according to the present invention. It is typical sectional drawing which shows the oil ring main body of the combination oil ring for internal combustion engines used in Comparative Examples 5 and 6. In Experimental example 1, it is an experimental result which shows the oil consumption with respect to the radial direction width | variety of an oil ring main body.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description and drawings as long as the technical features are included.

(Basic configuration)
The combined oil ring 10 for an internal combustion engine according to the present invention is called a two-piece type oil ring. As shown in FIG. 1 and FIG. An oil ring main body 11 in which the rail portions 1 and 2 are connected by the connecting portion 3 and the oil ring main body 11 disposed in the inner circumferential groove 4 formed at the center or substantially the center of the radially inner X2 of the connection portion 3. And a coil expander 12 that presses and urges the outer side in the radial direction X1.

  The oil ring main body 11 has an annular shape having an abutment (not shown), and has outer peripheral ends 6 and 7 that slide on the inner wall surface 31 (see FIG. 3) of the cylinder 30 on the radially outer side X1. A pair of rail portions 1 and 2 are provided so as to face each other in the axial direction Y.

  As shown in FIG. 2, the pair of rail portions 1 and 2 is configured such that the radial widths a <b> 1 and a <b> 2 are the same length and the outer peripheral ends 6 and 7 protrude outward in the radial direction X <b> 1. In the present application, since the radial widths a1 and a2 of the upper and lower rail portions 1 and 2 are the same, they are hereinafter referred to as “radial width a1”.

  Further, the pair of rail portions 1 and 2 are connected by a columnar connecting portion 3 (see FIG. 1, also referred to as a web portion) orthogonal to the rail portions 1 and 2 extending in the radial direction X. As shown in FIGS. 1 and 2, oil return holes 5 are provided in the connecting portion 3 at arbitrary intervals. Note that the oil that has passed through the oil return hole 5 from the internal space 13 during sliding is discharged from an oil drain hole 25 (see FIG. 3) provided in the ring groove 21 of the piston 20.

  The outer peripheral ends 6 and 7 of the pair of rail portions 1 and 2 may have tapered portions 16 and 17 on the outer side in the axial direction Y as necessary. The tapered portions 16 and 17 are brought into contact with the inner wall surface 31 of the cylinder 30 in a manner in which the outer peripheral ends 6 and 7 of the oil ring main body 11 are narrowed. In most cases, the tapered portions 16 and 17 are formed with the same width in the upper and lower rail portions 1 and 2. The flat surfaces that can come into contact with the lower surface 22 and the upper surface 23 of the ring groove 21 are evaluated by the radial widths b1 'and b2' of the flat surfaces excluding the tapered portions 16 and 17 (see FIG. 2).

  An inner circumferential groove 4 is formed at the center or substantially the center of the radially inward X2 of the oil ring body 11. The inner circumferential groove 4 is preferably formed with a radius of curvature larger than the diameter of the coil expander 12. Such an inner circumferential groove 4 is provided at the center or substantially the center in the axial direction Y on the radially inner side X2 of the oil ring main body 11. The coil expander 12 that contacts the inner circumferential groove 4 and presses and urges the oil ring main body 11 straight outward in the radial direction X1 is stably seated at the center or substantially the center in the axial direction Y by the inner circumferential groove 4. Well held.

  As described above, the coil expander 12 is disposed so as to be in contact with the radial bottom 4 ′ of the inner circumferential groove 4 formed at the center or substantially the center of the radially inner X 2 of the oil ring body 11. The coil expander 12 is a coiled annular member, and presses and urges the oil ring body 11 straight outward in the radial direction X1.

  The “axis” in the axial direction is the central axis (virtual center) of the combined oil ring 10 having an annular shape, and the “axial direction Y” is the direction in which the central axis extends (in FIG. 2). In the example, it is the direction extending up and down). The “radial direction X” is a radial direction when viewed from the central axis (virtual center) of the combined oil ring 10 having an annular shape, and “radially outward X1” is, for example, a combination It is the side (outer peripheral edge direction) of the cylinder inner wall surface where the outer peripheral ends 6 and 7 which are sliding surfaces of the oil ring 10 are in sliding contact, and “radially inward X2” means, for example, the combined oil ring 10 This is the central axis side of the oil ring in which the coil expander 12 is arranged.

  The material of the oil ring main body 11 constituting the combination oil ring 10 and the material of the coil expander 12 are not particularly limited, and various types can be adopted. As an example, steel materials, such as 8Cr steel and 10Cr steel, or cast iron materials can be mentioned.

  Further, it is preferable that the radial width a1 and the axial width h1 of the oil ring main body 11 are both 2 mm or less. The combined oil ring 10 including the oil ring body 11 can realize light weight and low friction. It is preferable that a1 is 1 mm to 2 mm and h1 is 1 mm to 2 mm.

(Relationship between each component)
In the present invention, (1) the tension ratio obtained by dividing the tension of the combined oil ring 10 by the cylinder inner diameter D2 to which the piston 20 is assembled is 0.05 N / mm or more and 0.3 N / mm or less, and (2) the oil ring main body 11 has a radial width a1 of 0.7 to 0.9 times the axial width h1, and (3) the inner peripheral ends 8 and 9 of the rail portions 1 and 2 and the radial bottom portion of the inner peripheral groove 4. 4 'is a depth d1 of the inner circumferential groove 4 that is not less than 0.35 times and not more than 0.50 times the radial width a1, and (4) the diameter d2 of the coil expander is the inner circumference. The groove 4 is configured to be less than twice the depth d1. In addition, (2)-(4) can be expressed as follows.

  The combined oil ring 10 for an internal combustion engine of the present invention having such characteristics and the assembled structure 50 in which the combined oil ring 10 for an internal combustion engine of the present invention is mounted in the ring groove 21 of the piston 20 and assembled in the cylinder 30 are: Oil consumption can be reduced. The reason will be described below.

  (1) The tension ratio of the combination oil ring 10 is 0.05 N / mm or more and 0.3 N / mm or less.

  The combination oil ring 10 having a tension ratio of 0.05 N / mm or more and 0.3 N / mm or less is preferable because friction is reduced and fuel efficiency is improved, and 0.05 N / mm or more and 0.20 N / mm or less is particularly preferable. If the tension ratio is less than 0.05 N / mm, the tension may be too weak and the oil seal function may be insufficient. On the other hand, if the tension ratio exceeds 0.3 N / mm, the effect of low friction becomes insufficient.

  The “tension ratio” (N / mm) is the tension of the combined oil ring 10 (the oil ring body 11 with the coil expander 12 attached) (that is, the force that expands the ring radially outward). The value divided by the inner diameter (mm) of the cylinder can be obtained by measuring the tension with a tension measuring instrument and then calculating it.

  (2) The radial width a1 of the oil ring body 11 is not less than 0.7 times and not more than 0.9 times the axial width h1.

  In a general two-piece type oil ring in a low-speed region (for example, less than 2000 rpm) that is in a low rotation and high negative pressure state, the negative pressure of the exhaust and compression stroke in which the piston 20 in the cylinder 30 moves toward the top dead center. When the pressure is applied, the lower rail portion 1 constituting the combination oil ring 10 that is light and has a low tension sticks to the lower surface 22 of the ring groove 21 via oil and is difficult to separate. Therefore, the movement timing of the oil ring tends to be delayed. The delay of the timing makes the oil seal on the upper surface side insufficient at the time of negative pressure action, and causes excessive oil rise.

  However, in the present invention, the radial width a1 of the lower rail portion 1 that tends to stick to the lower surface 22 of the ring groove 21 is set to be 0.7 to 0.9 times the axial width h1 of the oil ring body 11. Even in a low-speed range where the rotation is low and high negative pressure, the difficulty of separating the lower rail portion 1 from the lower surface 22 of the ring groove 21 can be reduced. As a result, the movement timing of the oil ring is not delayed, and the oil seal on the upper surface side during the negative pressure action can be optimized.

  On the other hand, when the radial width a1 of the upper and lower rail portions 1 and 2 exceeds 0.9 times the axial width h1 of the oil ring main body 11, the negative pressure action in which the piston 20 in the cylinder 30 moves toward the top dead center. At times, it is easy to stick to the lower surface 22 of the ring groove 21, and the movement timing is delayed. Therefore, the oil that has risen passes through the gap between the upper rail portion 2 and the upper surface 23 of the ring groove 21, so that the oil can easily rise. In the present invention, the radial width a1 of the upper and lower rail portions 1 and 2 is also 0.7 times or more and 0.9 times or less of the axial width h1 of the oil ring body 11, so that the oil that has risen on the upper surface side of the oil ring Since sealing is performed, it is easy to guide the oil drain hole 25 from within the ring groove 21. As a result, oil consumption can be further suppressed.

  Further, it is preferable that the tension ratio of the combination oil ring 10 is as low as 0.05 N / mm or more and 0.3 N / mm or less because friction is reduced and fuel efficiency is improved. , 2 has a function of scraping oil by reducing the radial width a1 when the axial width h1 of the oil ring body 11 is 0.7 times or more and 0.9 times or less. There is a concern that oil consumption will increase as it falls. In response to such a concern, the oil expander body is configured so that the coil expander 12 is deeply and stably mounted so as to come into contact with the radial bottom 4 ′ of the inner circumferential groove 4 by the configuration of the above formulas 2 and 3. 11 is pressed and urged stably in the radially outward direction X1 without vertical movement.

  When the radial width a1 of the oil ring main body 11 is less than 0.7 times the axial width h1, the absolute radial width a1 is small, and the contact length b1 with the upper and lower surfaces 22 and 23 of the ring groove 21 is reduced. , B2 (see FIG. 3) are shortened, and the oil seal function becomes insufficient. On the other hand, when the radial width a1 of the oil ring main body 11 exceeds 0.9 times the axial width h1, the lower rail portion 1 moves to the lower surface 22 of the ring groove 21 in a low-speed region that is in a low rotation and high negative pressure state. The oil seal on the upper surface side during the negative pressure operation cannot be optimized due to the delay in the movement timing of the oil ring.

  As shown in FIG. 3, the contact length b <b> 1 is a width in which the lower rail portion 1 and the lower surface 22 are actually in contact, and the inner peripheral end 8 of the lower rail portion 1 and the ring groove lower surface 22. This is the length between the outer peripheral end 26. On the other hand, the contact length b2 is a width where the upper rail portion 2 and the upper surface 23 actually contact each other, and is a length between the inner peripheral end 9 of the upper rail portion 2 and the outer peripheral end portion 27 of the ring groove upper surface 23. That's it.

  (3) The depth d1 of the inner peripheral groove 4 constituted by the inner peripheral ends 8 and 9 of the rail parts 1 and 2 and the radial bottom part 4 ′ of the inner peripheral groove 4 is the radial width a1 of the oil ring body 11. 0.35 times or more and 0.50 times or less.

  Since the depth d1 of the inner circumferential groove 4 is set to be 0.35 times or more and 0.50 times or less of the radial width a1 of the oil ring body 11, the oil whose radial width a1 is shorter than the axial width h1. Appropriate tension can be applied to the ring body 11, and the capacity of the internal space 13 inside the outer peripheral ends 6, 7 of the upper and lower rail portions 1, 2 is reduced, so that oil can be supplied from the oil return hole 5. Suppressing smooth discharge to the inner circumferential groove 4 of the oil ring main body 11 can be suppressed. As a result, the oil seal function can be maintained.

  If d1 / a1 is less than 0.35, the coil expander 12 having a small diameter must be selected in order to satisfactorily and stably assemble the coil expander 12 to the inner circumferential groove 4. Therefore, the tension that presses and urges the oil ring body 11 radially outward X1 becomes small, and the oil seal function cannot be satisfied. On the other hand, if d1 / a1 exceeds 0.50, the connecting portion 3 is positioned on the radially outward X1 side. The capacity of the space 13 is reduced. Therefore, since the oil is easily filled in the internal space 13, the oil is likely to rise from the sliding surface of the upper rail portion 2, and as a result, the oil consumption increases.

  (4) The diameter d2 of the coil expander 12 disposed in the inner circumferential groove 4 is less than twice the depth d1 of the inner circumferential groove 4.

  The fact that d2 is less than twice d1 (d2 / d1 <2) means that the coil expander 12 is disposed in such a manner that it is embedded in the inner circumferential groove by more than half. The oil ring body 11 is pressed and urged radially outward X1. Furthermore, since the inner circumferential groove 4 is formed with a radius of curvature larger than the diameter d 1 of the coil expander 12, the coil expander 12 is arranged in contact with the radial bottom 4 ′ of the inner circumferential groove 4. Such a mounting mode of the coil expander 12 in the inner circumferential groove 4 can press and urge the oil ring main body 11 straight and stably outward in the radial direction X1, and can enhance the oil seal function. In other words, since the coil expander 12 is deeply and stably mounted so as to come into contact with the radial bottom 4 ′ of the inner circumferential groove 4, the oil ring body 11 is stably pressed against the radially outward X1 without any vertical movement. Energized. Therefore, even in the upper rail portion 2 having a short radial width a2, the oil seal function is not deteriorated.

  When d2 exceeds twice d1, the inner peripheral groove 4 becomes shallow, and the coil expander 12 cannot be stably assembled. As a result, the oil ring body 11 that presses and urges radially outward X1 is likely to be up and down, and the oil seal function at the upper and lower rail portions 1 and 2 of the oil ring body 11 with a short radial width a2 is reduced. Will do.

  The lower limit value of d2 / d1 is about 1.0. When the lower limit is less than 1.0, the assembling property is deteriorated.

  (5) Further, as shown in FIG. 3, in the assembly structure 50 in which the combined oil ring 10 of the present invention is mounted in the ring groove 21 of the piston 20 and assembled in the cylinder 30, the lower surface 22 of the ring groove 21. When the diameter between the outer peripheral end portions 26, 26 is D1, and the inner diameter of the cylinder 30 is D2, [{a1- (D2-D1) / 2} / a1 × 100] (%) is (50)% Above (75)%.

  By setting [{a1- (D2-D1) / 2} / a1 × 100] (%) to (50)% or more and (75)% or less, the upper and lower rail portions 1 and 2 and the upper and lower surfaces 22 of the ring groove 21 , 23 can be held at a constant length, so that the oil seal function can be maintained.

  If the ratio is less than 50%, the contact lengths b1 and b2 are short, so that a sufficient oil seal function cannot be exhibited, and the assemblability is deteriorated. On the other hand, when the ratio exceeds 75%, the oil consumption increases in the high negative pressure region.

  As described above, the combination oil ring 10 and the assembly structure thereof according to the present invention have the above features (1) to (4) to (5), so that the weight is reduced due to the demand for low friction, and further 0.05 N / mm or more is 0. Even with the combination oil ring 10 having a tension reduced to 3 N / mm or less, the oil consumption when the internal combustion engine is operated under the conditions of low rotation and high negative pressure can be reduced.

  The movement of the combined oil ring 10 greatly depends on the friction (frictional force) between the cylinder 30 and the inner wall surface 31 of the cylinder 30 and the inertial force of the combined oil ring 10 itself. Friction with the inner wall surface 31 is the main, and the combined oil ring 10 moves in the axial direction. The force that the lower rail portion 1 adheres to the lower surface 22 of the ring groove 21 is a force that opposes the movement of the combination oil ring 10. The present invention configured as described above can move the combined oil ring 10 at the same time as the direction of the friction is switched between the top dead center and the bottom dead center. Furthermore, even if the upper rail portion 2 is shortened to the same length as the lower rail portion 1, the coil expander 12 is stably mounted in the inner circumferential groove 4, so that the oil ring main body 11 is moved radially outward. It is possible to stably press and bias X1 without up and down movement. As a result, the oil seal on the upper surface side during the negative pressure action can be optimized.

  Hereinafter, embodiments of the present invention will be described. Each embodiment has the following specific features while having at least the common features described above.

[Examples 1 to 5, Comparative Examples 1 to 4]
The radial widths a1 and a2 of the oil ring body 11, the axial width h1, the depth d1 of the inner circumferential groove 4, the diameter d1 of the coil expander 12, and the tension ratio of the combined oil ring 10 are the dimensions shown in Table 1. The combined oil rings 10 of Examples 1 to 5 and Comparative Examples 1 to 4 thus configured were produced. The assembled oil ring 10 thus produced was mounted in the ring groove 21 of the piston 20 and mounted in the cylinder 30 to constitute an assembly structure 50. The oil ring main body 11 having the form shown in FIGS. 6A and 6B is used in Comparative Examples 3 and 4.

  The oil consumption experiment of each example was conducted. In the experiment, a cylinder 30 having an inner diameter D2 of 88.5 mm and a piston 20 having a diameter D1 between the outer peripheral ends of the lower surface of 87.4 mm were used. The intake pipe absolute pressure at 1000 rpm was 10 kPa for 8 hours, and the oil consumption in the assembly structure 50 was evaluated. The evaluation results are also shown in Table 1.

  As shown in Table 1, in the combination oil rings of Examples 1 to 5 as compared with the conventional example, the oil consumption ratio was reduced by 30% or more, and it was found that the oil consumption was very effective. Moreover, about Comparative Examples 1-3, since it was not able to assemble | attach when attaching to a ring groove, it was set as "x". About the comparative example 4, although assembly | attachment property was good, it turned out that an oil consumption ratio becomes a result worse than a prior art example, and deteriorates oil consumption.

[Examples 6 and 7]
4A and 4B are schematic cross-sectional views showing another embodiment of the present invention. These forms are devised to improve the formability of forming the oil ring main body 11 having a reduced radial width a1 into a ring shape, or to supplement the strength, but the effects of the present invention described above. Play.

  The combined oil ring 10 shown in FIG. 4 (A) has a tapered wall extending radially outward X1 of the connecting portion 3 from the upper and lower edges of the oil return hole 5 toward the outer peripheral ends 6 and 7 of the rail portions 1 and 2. The thick portion 15 is provided uniformly in the annular direction.

  The combined oil ring 10 shown in FIG. 4 (B) has an arcuate protrusion 19 that is raised in the center in the annular direction on the radially outward X1 of the connecting portion 3. In addition, the oil return hole 5 is provided so that the connection part 3 and its protrusion 19 may be penetrated at arbitrary intervals as described above.

[Experimental Example 1]
FIG. 5 is an experimental result showing the oil consumption with respect to the radial width a <b> 1 of the oil ring main body 11. The experiment used an oil ring main body 11 based on the dimensions of Example 1 described above, with the radial width a1 and the inner circumferential groove depth d1 varied. In addition, the radial width a1 is prepared in four types: 2 mm (conventional example), 1.7 mm (examples 1, 4, 5), 1.5 mm (example 2), and 1.4 mm (example 3). Experimented. In the experiment, a cylinder 30 having an inner diameter D2 of 88.5 mm was used. An experiment was conducted with the absolute pressure of the intake pipe at 1000 rpm being 10 kPa and 15 kPa, and the oil consumption in the assembly structure 50 was evaluated. The oil consumption was performed under the same conditions as in Examples 1 to 5 above.

  As shown in FIG. 5, in the low rotation / high negative pressure region, it was found that the smaller the radial width a1, the smaller the oil consumption, and the more effective the oil consumption.

DESCRIPTION OF SYMBOLS 1 Lower rail part 2 Upper rail part 3 Connection part 4 Inner peripheral groove 4 'Radial bottom part of inner peripheral groove 5 Oil return hole 6,7 Outer peripheral end 8,9 Inner peripheral end 10 Combination oil ring 11 Oil ring main body 12 Coil Expander 13 Internal space 15 Tapered thick part 16, 17 Tapered part 19 Arc shaped protrusion 20 Piston 21 Ring groove 22 Lower surface of ring groove 23 Upper surface of ring groove 25 Oil drain hole 26 Outer peripheral end of lower surface of ring groove Part 27 Outer peripheral edge part of upper surface of ring groove 30 Cylinder 31 Inner wall surface of cylinder 50 Assembly structure of combination oil ring

a1 Radial width of the lower rail portion arranged on the lower surface side of the ring groove a2 Radial width of the upper rail portion arranged on the upper surface side of the ring groove b1 ′ Radial width of the flat surface of the a1 b2 ′ a2 B1 Radial width of the flat surface b1 Radial contact length between the lower surface of the ring groove and the lower rail portion b2 Radial contact length between the upper surface of the ring groove and the upper rail portion h1 Oil ring body Width in the axial direction X Radial direction X1 Radial outward X2 Radial inward Y Axial direction d1 Inner groove depth d2 Coil expander diameter D1 Diameter between the outer peripheral ends of the lower surface of the ring groove D2 Cylinder inner diameter

Claims (3)

An oil ring main body in which two upper and lower rail portions whose outer peripheral ends protrude radially outward are connected by a connecting portion, and the oil ring main body disposed in an inner peripheral groove formed in the radially inner center of the connecting portion. A combined oil ring for an internal combustion engine that is mounted in a ring groove provided on the outer periphery of the piston.
(1) The tension ratio obtained by dividing the tension of the combined oil ring by the inner diameter of the cylinder to which the piston is assembled is 0.05 N / mm or more and 0.3 N / mm or less,
(2) The radial width of the oil ring body is 0.7 times or more and 0.9 times or less of the axial width,
(3) The depth of the inner circumferential groove formed by the inner circumferential end of the rail portion and the radial bottom portion of the inner circumferential groove is 0.35 to 0.50 times the radial width,
(4) A combined oil ring for an internal combustion engine, wherein the diameter of the coil expander is less than twice the depth of the inner circumferential groove.   A combined oil ring for an internal combustion engine according to claim 1, wherein the combined oil ring for an internal combustion engine is mounted in a ring groove provided on the outer periphery of the piston and assembled in a cylinder.   When the radial width of the oil ring body is a1, the diameter between the outer peripheral ends of the lower surface of the ring groove is D1, and the inner diameter of the cylinder is D2, [{a1- (D2-D1) / 2} / A1 × 100] (%) is an assembly structure of a combined oil ring for an internal combustion engine according to claim 2, wherein 50% or more and 75% or less.

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