JP2011058373A - Combined oil ring for internal combustion engine, and assembly structure of the same - Google Patents

Abstract

An assembly structure of a combined oil ring for an internal combustion engine that reduces oil consumption in a low rotation and high negative pressure state is provided.
An oil ring main body 11 in which two upper and lower rail portions 1 and 2 projecting radially outward X1 are connected by a connecting portion 3, and an inner peripheral groove formed in the radially inner center of the connecting portion 3. 4 is an assembly structure 50 in which a combined oil ring 10 including a coil expander 12 disposed in a cylinder 4 and pressing and urging the oil ring body 11 radially outward X1 is mounted in a ring groove 21 and assembled in a cylinder. The tension ratio obtained by dividing the tension of the combined oil ring 10 by the cylinder inner diameter is in the range of 0.05 to 0.3 N / mm, and the chamfer 24 provided at the radially outer peripheral end of the lower surface of the ring groove or below It has a notch portion provided at the radially outer peripheral end portion of the lower surface of the side rail portion, and the radial contact length b2 between the ring groove lower surface 22 and the lower rail portion 1 is set to the ring groove upper surface 23 and the upper rail portion. Radial contact length b1 with 2 And 60 to 98 percent.
[Selection] Figure 1

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 peripheral surface 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.

  In an oil ring assembly structure in which the oil ring is mounted in the piston ring groove, the oil ring requires oil by increasing the tension (the force that expands the ring radially outward) relative to the pressure ring. A minimum amount of oil is supplied to the inner wall of the cylinder, and the excess oil is scraped off and collected (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).

  For example, as shown in Patent Document 1, a two-piece type oil ring includes a ring main body in which a pair of rail portions are integrally formed, and an axially centered inner side of the ring main body so that the ring main body is radially outside. And an oil ring in which the outer peripheral ends of the pair of rail portions are in sliding contact with the inner wall surface of the cylinder. In the assembly structure of the oil ring in which this two-piece type oil ring is installed in the ring groove of the piston, while the piston in the cylinder goes from the process center to the top dead center and returns to the process center, While the rail part contacts the ring groove upper surface and the upper rail part contacts the ring groove upper surface and slides, while the piston in the cylinder goes from the process center to the bottom dead center and returns to the process center Slides with the lower rail portion of the oil ring in contact with the lower surface of the ring groove and the lower rail portion in contact with the lower surface of the ring groove.

  In addition, the 2 piece type oil ring described in Patent Document 2 is shown for reference. In this two-piece type oil ring, the upper rail portion is constantly pressed against the upper surface of the ring groove, and the coil expander is always pressed against the lower surface of the ring groove. With such a configuration, the gap generated between the upper surface of the ring main body and the upper side surface of the ring groove is closed, and the oil rise generated through the gap is reduced.

JP-A 61-45172 JP 2002-30002 A

  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 conditions of lightening and low tension of these two-piece type oil rings, because the inertia force is small, the oil adhesion force As a result, the oil ring is seated on the lower surface of the ring groove during the intake / explosion stroke, which should normally be seated on the upper surface of the ring groove, and therefore tends to be higher than when operating under conditions of high to medium rotation and high negative pressure ( Although it is expected that the oil tends to be consumed easily, it has not been fully examined.

  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”) This is to provide an assembly structure of “combined oil ring”. Another object of the present invention is to provide a combined oil ring for an internal combustion engine that can reduce oil consumption in a low rotation and high negative pressure state.

  An assembly structure of a combined oil ring for an internal combustion engine according to the present invention for solving the above-described problems includes an oil ring body in which two upper and lower rail portions protruding radially outward are connected by a connecting portion, and the connecting portion of the connecting portion. Formed on the outer peripheral surface of the piston is a combined oil ring for an internal combustion engine, which is arranged in an inner peripheral groove formed in the radially inner center and comprises a coil expander that presses and urges the oil ring main body radially outward. In the assembled structure of the combined oil ring for an internal combustion engine that is mounted in the ring groove and assembled in the cylinder, the tension ratio obtained by dividing the tension of the combined oil ring by the cylinder inner diameter is 0.05 to 0.3 N / The chamfered portion provided at the radially outer peripheral end portion of the lower surface of the ring groove of the piston or the radially outer peripheral end portion of the lower surface of the lower rail portion of the oil ring body. The contact length in the radial direction between the lower surface of the ring groove and the lower rail portion is 60% to 98% of the contact length in the radial direction between the upper surface of the ring groove and the upper rail portion. %.

  In the assembled structure of the combined oil ring for an internal combustion engine according to the present invention, it is preferable that an axial width of the oil ring main body is 2 mm or less.

  The combined oil ring for an internal combustion engine according to the present invention for solving the above-described problems includes an oil ring body in which two upper and lower rail portions projecting radially outward are connected by a connecting portion, and a radially inner side of the connecting portion. For an internal combustion engine, which is arranged in an inner circumferential groove formed in the center and is composed of a coil expander that presses and urges the oil ring body radially outward, and is mounted in a ring groove formed on the outer circumferential surface of the piston In the combined oil ring, 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 in a range of 0.05 to 0.3 N / mm, and the ring groove of the two rail portions is The radial width of the lower rail portion in contact with the lower surface side is 60% to 98% of the radial width of the upper rail portion in contact with the upper surface side of the ring groove.

  In the combined oil ring for an internal combustion engine according to the present invention, it is preferable that an axial width of the oil ring main body is 2 mm or less.

(Function)
The assembly structure of the combined oil ring for an internal combustion engine according to the present invention in which the combined oil ring is attached to the ring groove of the piston and assembled in the cylinder can reduce oil consumption. The reason for this is as follows. That is, in a low speed range (for example, less than 2000 rpm / min) in a low rotation / high negative pressure state, a light weight and low tension are applied during the negative pressure action in the exhaust / compression stroke in which the piston in the cylinder moves toward the top dead center. The lower rail portion constituting the combined oil ring is attached to the lower surface of the ring groove via oil and is difficult to be separated. Therefore, the movement timing of the oil ring is delayed. As a result, the oil seal on the upper surface side at the time of negative pressure action becomes insufficient, causing excessive oil rise.

  In the assembly structure of the combined oil ring for an internal combustion engine according to the present invention, the chamfered portion provided at the radially outer peripheral end portion of the lower surface of the ring groove or the notch portion provided at the radially outer peripheral end portion of the lower surface of the lower rail portion. The radial contact length between the lower surface of the ring groove and the lower rail portion is as short as 60% to 98% of the radial contact length between the upper surface of the ring groove and the upper rail portion. Therefore, even in a low rotation / high negative pressure state, the difficulty of the lower rail portion being separated from the lower surface of the ring groove 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.

  Similarly, in the combined oil ring for an internal combustion engine according to the present invention, the radial width of the lower rail portion that easily sticks to the lower surface of the ring groove is shortened to 60% to 98% of the radial width of the upper rail portion. Even in a low rotation / high negative pressure state, it is possible to reduce the difficulty of the lower rail portion being separated from the lower surface of the ring groove. 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.

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

It is typical sectional drawing which shows 1st Example (assembled structure of a combination oil ring) of this invention. It is typical sectional drawing which shows 2nd Example (assembled structure of a combination oil ring) of this invention. It is typical sectional drawing which shows the 3rd-5th Example (assembled structure of a combination oil ring) of this invention. It is typical sectional drawing which shows the 6th, 7th Example (assembled structure of a combination oil ring) of this invention. 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 a typical sectional view showing the 8th example (combination oil ring) of the present invention. It is typical sectional drawing which shows the 9th Example (assembled structure of a combination oil ring) which mounted | wore the ring groove of the piston with the combination oil ring of 8th Example shown in FIG. 6, and was attached in the cylinder.

  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.

[Assembly structure of combination oil ring for internal combustion engine]
The combined oil ring assembly structure 50 for an internal combustion engine according to the present invention includes an internal combustion engine combined oil ring 10 mounted in a ring groove 21 formed on the outer peripheral surface of a piston 20 as shown in FIG. It is an assembly structure assembled in the cylinder 30.

  The combined oil ring 10 for an internal combustion engine is called a two-piece type oil ring. As shown in FIG. 1 and the like, two upper and lower rail portions 1 and 2 projecting radially outward X1 are connected by a connecting portion 3. An oil ring body 11 and a coil disposed in an inner circumferential groove 4 formed at the center or substantially the center of the radially inner X2 of the connecting portion 3 to press and urge the oil ring body 11 toward the radially outer X1. And an expander 12. In the present application, “center or substantially center” may be abbreviated as “center”.

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

  A pair of rail parts 1 and 2 are comprised in the aspect from which the outer peripheral ends 6 and 7 protrude in radial direction outward X1. Further, the pair of rail portions 1 and 2 are connected by a columnar connecting portion 3 (see also FIG. 5, also referred to as a web portion) orthogonal to the rail portions 1 and 2 extending in the radial direction X. As shown in FIG. 1 and the like, oil return holes 5 are provided in the connecting portion 3 at arbitrary intervals. 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 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 outer peripheral side tapered portions 16 and 17 on the outer side in the axial direction Y as necessary. These outer peripheral side taper parts 16 and 17 contact the inner wall surface 31 of the cylinder 30 in the aspect which made the outer peripheral ends 6 and 7 of the oil ring main body 11 thin.

  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. In the example of FIG. 1, the inner circumferential groove 4 is preferably formed in an arc larger than the diameter of the coil expander 12, but it does not necessarily have to be formed in such a form, and the diameter of the coil expander 12 Same as Further, the shape of the inner circumferential groove 4 may not be an arc, and may be a rectangular groove or a triangular groove. 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 is in contact with the inner circumferential groove 4 and presses and urges the oil ring body 11 radially outward X1 is held by the inner circumferential groove 4 at the center or substantially the center in the axial direction Y. In this respect, the aspect described in Patent Document 2 described above is greatly different. In the aspect of Patent Document 2, since the oil ring body is maintained in contact with the upper surface of the ring groove, it is difficult to scrape the oil that has risen to the third land.

  As described above, the coil expander 12 is disposed so as to contact the inner circumferential groove 4 formed at the center or substantially the center of the radially inner X2 of the oil ring body 11. As shown in the example of FIG. 5, the coil expander 12 is a coiled annular member that presses and urges the oil ring main body 11 radially outward X1.

  In addition, 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. 1). In the example, it is the direction extending up and down). Further, as shown in FIGS. 1 and 5, 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. “Directionally outward X1” means, for example, the side of the cylinder inner wall surface (outer peripheral edge direction) with which the outer peripheral ends 6 and 7 which are sliding surfaces of the combination oil ring 10 are in sliding contact. "" Is the central axis side of the oil ring on which the coil expander 12 constituting the combination oil ring 10 is disposed, for example.

  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, 10Cr steel, and 13Cr steel, can be mentioned.

  The maximum width h1 in the axial direction Y of the oil ring main body 11 constituting the combination oil ring 10 is preferably 2 mm or less. The combined oil ring 10 including the oil ring body 11 can realize light weight and low friction. The lower limit of h1 is not particularly limited, but can be 1.0 mm.

  The present invention is characterized in that the tension ratio of the combination oil ring 10 is in the range of 0.05 to 0.3 N / mm. The combination oil ring 10 having a tension ratio of 0.05 to 0.3 N / mm is preferable because friction is reduced and fuel efficiency is improved, and the range of 0.05 to 0.20 N / mm is particularly preferable.

  The “tension ratio” (N / mm) is a value obtained by dividing the tension of the combined oil ring 10 (that is, the force for expanding the ring radially outward) by the inner diameter (mm) of the cylinder. The measurement of can be obtained by measuring the tension with a tension measuring machine and then calculating.

  In the present invention, the “contact length b2” in which the lower surface 22 of the ring groove 21 included in the piston 20 and the lower rail portion 1 disposed on the lower surface 22 side abuts and seals the oil is the ring groove 21. This is characterized in that it is 60% to 98% of the “contact length b1” in which the upper surface 23 and the upper rail portion 2 disposed on the upper surface 23 side come into contact with each other to oil-seal.

  The contact length b2 is a width where the lower rail portion 1 and the ring groove lower surface 22 actually contact each other. In the example of FIG. 1 and the like, the inner peripheral end 8 of the lower rail portion 1 and the ring groove lower surface 22 is the length between the outer peripheral end portion 26 of 22. On the other hand, the contact length b1 is a width where the upper rail portion 2 and the ring groove upper surface 23 actually contact each other. In the example of FIG. 1 and the like, the inner peripheral end 9 of the upper rail portion 2 and the ring groove upper surface 23 It is the length between the outer peripheral end 27.

  In the first to fifth embodiments to be described later, as shown in FIGS. 1 to 3, the radial outer peripheral end of the lower surface 22 of the ring groove 21 and / or the radial outer peripheral end of the lower surface of the lower rail portion 1 are used. By providing the chamfered portion 24, the [contact length b2] is 60% to 98% of the [contact length b1].

  In the sixth and seventh embodiments, which will be described later, as shown in FIG. 4, the notch portion 29 is provided in the lower rail portion 1 facing the lower surface 22 of the ring groove 21, thereby reducing the [contact length b <b> 2]. It is characterized in that it is set to 60% to 98% of [contact length b1].

  In the eighth and ninth embodiments, which will be described later, by cutting the inner peripheral end 8 of the lower rail portion 1 to be shorter than the inner peripheral end 9 of the upper rail portion 2, the [contact length b2] is reduced. It is characterized in that it is set to 60% to 98% of [contact length b1]. In the seventh embodiment, the lower rail portion 1 facing the lower surface 22 of the ring groove 21 is provided with a notch 29, and the inner rail 8 of the lower rail portion 1 is cut and the upper rail portion 1 is cut. 2 is shorter than the inner peripheral end 9.

  The reason for setting [contact length b2] / [contact length b1] within the range of 60% to 98% is as follows.

  That is, it is preferable that the tension ratio of the combined oil ring 10 is as low as in the range of 0.05 to 0.3 N / mm because friction is reduced and fuel efficiency is improved. On the other hand, the function of scraping oil is reduced. There is a concern that oil consumption will increase. The present invention is characterized by the fact that the upper [abutment length b1], which mainly contributes to oil scraping, is not particularly improved and the lower [abutment length b2] is reduced in response to such concerns. There is.

  In a low speed range (for example, less than 2000 rpm) that is in a low rotation / high negative pressure state, the piston 20 in the cylinder 30 is light and has low tension during the negative pressure action during the exhaust / compression stroke in which the piston 20 moves toward top dead center. The lower rail portion 1 constituting the combined oil ring 10 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. As a result, the oil seal on the upper surface side at the time of negative pressure action becomes insufficient, causing excessive oil rise. In order to deal with such a problem, in the present invention, the “contact length b2” for oil sealing between the lower surface 22 of the ring groove 21 and the lower rail portion 1 that easily sticks to the lower surface 22 is set to the upper surface 23 of the ring groove 21 and the upper rail. It is shortened to be 60% to 98% of the “contact length b1” for oil sealing with the portion 2. By doing so, it is possible to reduce the difficulty of the lower rail portion 1 being separated from the lower surface 22 of the ring groove 21 even in a low rotation / high negative pressure state. As a result, the movement timing of the oil ring is reduced. Without delay, the oil seal on the upper surface side during negative pressure action can be optimized.

  A more preferable range is 60% to 75%. By setting it within this range, the oil consumption can be further reduced.

  The combination oil ring 10 and the assembly structure 50 of the present invention have the above characteristics in the tension ratio and [contact length b2] / [contact length b1]. Further, even when the combined oil ring 10 and its assembled structure 50 are reduced in tension in the range of 0.05 to 0.3 N / mm, the oil when the internal combustion engine is operated under conditions of low rotation and high negative pressure. Consumption can be reduced.

  In particular, by setting b2 / b1 in the range of 60% to 98% in the assembly structure 50 of the combination oil ring, and a2 / a1 in the range of 60% to 98% in the combination oil ring 10, Adhesive force with the lower surface 22 of the ring groove 21 with which the side rail portion 1 contacts can be reduced. The movement of the combined oil ring 10 largely depends on the friction between 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 of 30 is the main, and reciprocates in the axial direction. The force with which the lower rail portion 1 adheres to the lower surface 22 of the ring groove 21 is a force against the frictional force / inertial force. Therefore, in the present invention, by reducing the adhesion force by setting a2 / a1 or b2 / b1 within the above range, the direction of the friction is switched at the top dead center and the bottom dead center, and at the same time, the combined oil ring 10 is It becomes possible to separate from the ring groove. 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. In the following description of the first to ninth embodiments, common features are omitted unless otherwise noted.

[First and second embodiments]
1 and 2 are schematic sectional views showing first and second embodiments (an assembly structure of a combined oil ring for an internal combustion engine). In the first and second embodiments, the radial widths a1 and a2 of the rail portions 1 and 2 are the same length, and the radial width a2 is shorter than the radial width a1. Different from the example. In the first and second embodiments, by providing a chamfered portion 24 at the radially outer peripheral end portion of the lower surface 22 of the ring groove 21, the [contact length b2] is reduced to 60% of the [contact length b1]. It is characterized in that it is set to ~ 98%. Other points are as described above.

  The first embodiment of FIG. 1 is an example in which a chamfered portion 24 provided at the radially outer peripheral end portion of the lower surface 22 of the ring groove 21 has a step. Specifically, the outer peripheral end portion of the lower surface 22 of the ring groove 21 is illustrated. This is an example in which a chamfered portion 24 provided with an inclination is provided after being cut downward at a right angle from 26. In FIG. 1, reference numeral 28 denotes a skirt portion, and reference numeral c denotes a radial width from the outer peripheral end portion 26 of the lower surface 22 of the ring groove 21 to the skirt portion 28 of the piston 20.

  The second embodiment of FIG. 2 is an example in which the chamfered portion 24 of the first embodiment of FIG. 1 is reduced to increase the contact length b2. This is an example in which the radial width c ′ from the outer peripheral end portion 26 of the lower surface 22 of the ring groove 21 to the skirt portion 28 of the piston 20 is smaller than the radial width c of FIG. 1.

  In the first and second embodiments, for example, a1 and a2 are 2 mm, and the contact length b2 (the lower rail portion 1 of the lower rail portion 1) where the lower rail portion 1 and the lower surface 22 of the ring groove 21 actually contact each other is set. The length between the inner peripheral end 8 and the outer peripheral end portion 26 of the ring groove lower surface 22 is 1.2 mm in the first embodiment and 1.25 mm in the second embodiment, and the upper rail portion 2 and the upper surface 23 are The actual contact length b1 (the 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) was 1.36 mm.

  Further, in the actual mounting of the combined oil ring 10, at least 50% to 70% of the radial width a <b> 2 of the lower rail portion 1 is in contact with the lower surface 22 of the ring groove 21 in the radial direction. It is desirable to constitute the contact length b2 of X. The length ratio is represented by [{a2- (D2-D1) / 2} / a2 × 100] (%). A preferable range of the length ratio is 50% to 60%. In addition, the code | symbol D1 is a diameter between the outer peripheral edge parts of the lower surface of a ring groove, and code | symbol D2 is an internal diameter of a cylinder. As described above, the width in the radial direction of the oil ring body 11 is preferably 2 mm or less. For example, when a1 is 2 mm, a2 is 1.5 mm, D1 is 87.14 mm, and D2 is 88.5 mm The length b1 is preferably in the range of 1.0 to 1.4 mm.

[Third to fifth embodiments]
FIG. 3 is a schematic cross-sectional view showing third to fifth embodiments (an assembly structure of a combined oil ring for an internal combustion engine). The assembly structure 50 according to the third to fifth embodiments is also the same mode as the assembly structure 50 according to the first and second embodiments, and faces the radially outer peripheral end portion of the lower surface 22 of the ring groove 21. A feature is that the contact portion b2 is set to 60% to 98% of the [contact length b1] by providing the catch portion 24. The assembly structure 50 according to the third to fifth embodiments is a modification of the form of the chamfered portion 24. Other points are as described above.

  The third embodiment of FIG. 3A is an example in which the chamfered portion 24 is a rectangular step, and is an example in which a cut step is provided at a right angle from the outer peripheral end portion 26 of the lower surface 22 of the ring groove 21.

  The fourth embodiment of FIG. 3B is an example in which the chamfered portion 24 has a tapered slope, and has a tapered shape of 10 ° to 80 ° obliquely from the outer peripheral end portion 26 of the lower surface 22 of the ring groove 21. This is an example.

  The fifth embodiment of FIG. 3C is an example in which the chamfered portion 24 is a curved slope, and the radius of curvature is about 0.6 to 1.0 mm from the outer peripheral end portion 26 of the lower surface 22 of the ring groove 21. Or it is the example which provided the elliptical gentle curved surface.

[Sixth and seventh embodiments]
FIG. 4 is a schematic cross-sectional view showing a sixth and seventh embodiment (an assembly structure of a combined oil ring for an internal combustion engine). Among these, the sixth embodiment shown in FIG. 4A is the same as the first to fifth embodiments in that the radial widths a1 and a2 of the rail portions 1 and 2 are the same length. The first to fifth embodiments in which a recess (notch 29) is formed on the outer peripheral end 6 side of the lower rail portion 1 of the ring body 11 is provided with a chamfered portion at the radially outer peripheral end of the ring groove lower surface 22. It is different from the example. This is characterized in that [abutment length b2] is 60% to 98% of [abutment length b1].

  On the other hand, in the seventh embodiment shown in FIG. 4B, the radial width a2 of the lower rail portion 1 is shorter than the radial width a2 of the upper rail portion 2 as in the eighth and ninth embodiments described later. In addition, as in the sixth and seventh embodiments, by providing a recess (notch 29) at the radially outer peripheral end of the lower surface 22 of the ring groove 21, the [contact length b2] is set to [contact]. The length b1] is characterized by 60% to 98%.

[Eighth embodiment]
FIG. 6 is a schematic sectional view showing an eighth embodiment (combined oil ring for an internal combustion engine). The combined oil ring 10 has a radial width a2 of the lower rail portion 1 disposed on the lower surface side of the ring groove 21 included in the piston 20 of the two rail portions 11 and 12, and the upper surface side of the ring groove 21. It is characterized in that it is 60% to 98% of the radial width a <b> 1 of the upper rail portion 2 disposed at the position.

  In many cases, the rail portions 1 and 2 have tapered portions 16 and 17 on the outer peripheral side, but the tapered portions 16 and 17 are almost always formed with the same width in the upper and lower rail portions 1 and 2. Therefore, as shown in FIG. 6, regardless of the presence or absence of the tapered portions 16, 17, this eighth embodiment is sufficient if a2 / a1 is within the above range.

  In the case where the radial widths of the taper portions 16 and 17 are different between the upper and lower rail portions 1 and 2, the assembly oil ring 10 is mounted on the ring groove 21 of the piston 20 and then attached to the cylinder 30 as described above. Thus, [abutment length b2] / [abutment length b1] can be specified as a range of 60% to 98%. In the first to seventh embodiments described above, the contact length b1 and the contact length b2 after the assembly structure in the cylinder 30 are evaluated, but at the stage of the combination oil ring 10 before assembly. The dimensions of the contact length b1 and the contact length b2 cannot be accurately evaluated. Therefore, the “radial width b1 ′” and “radial width b2 ′” of the flat surfaces that can come into contact with the ring grooves 22 and 23, that is, the flat surfaces excluding the tapered portions 16 and 17 (which may or may not be present). And b2 ′ / b1 ′ may be defined as 60% to 98%.

  As an example, an oil made of 8Cr steel having a1 of 2.0 mm, a2 of 1.7 mm, taper portions 16 and 17 having a radial width of 0.2 mm, h1 of 2.0 mm, and a tension ratio of 0.28 N / mm. A ring main body 11 and a coil expander 12 made of 8Cr steel were produced.

[Ninth embodiment]
FIG. 7 shows a ninth embodiment (combined oil ring assembly structure 50 for an internal combustion engine) in which the combined oil ring 10 of the eighth embodiment is mounted in the ring groove 21 of the piston 20 and installed in the cylinder 30. It is typical sectional drawing.

  This assembly structure 50 uses the combination oil ring 10 of the eighth embodiment, that is, the lower rail disposed on the lower surface side of the ring groove 21 included in the piston 20 of the two rail portions 11 and 12. The combination oil ring 10 is characterized in that the radial width a2 of the portion 1 is 60% to 98% of the radial width a1 of the upper rail portion 2 disposed on the upper surface side of the ring groove 21. In the assembly structure 50 having the combined oil ring 10, the contact length b <b> 2 in the radial direction X between the lower surface 22 of the ring groove 21 of the piston 20 and the lower rail portion 1 is the upper surface of the ring groove 21. 23 and the upper rail portion 2 is 60% to 98% of the contact length b1 in the radial direction X.

[Oil consumption experiment]
The oil consumption experiment was conducted under the following experimental conditions by applying the first embodiment. In the experiment, an actual machine experiment of an in-line four-cylinder gasoline engine having a displacement of 2400 cc and a cylinder inner diameter D2 of 88.5 mm was performed, and a confirmation experiment of oil consumption was performed. The operating condition of the engine is light load motoring and a rotational speed of 2000 r. p. m. For 5 hours. In the evaluation, the oil consumption was evaluated by setting the absolute pressure of the intake pipe to 10 kPa and 20 kPa.

  A piston 20 having a diameter D1 between the outer peripheral ends of the lower surface of 87.14 mm was used. The piston ring combination was a first ring, a second ring, and an oil ring. The first ring is made of 13Cr steel, h1 is 1.0 mm, a1 is 2.7 mm, the outer peripheral shape is a barrel face, and the top and bottom surfaces are nitrided and the outer peripheral surface is PVD-treated. . As the second ring, a SWRH62B material defined in JIS G 3506 (1996), h1 of 1.0 mm, a1 of 2.7 mm, and outer peripheral surface shape having a taper undercut was used.

  As the oil ring, the two-piece type oil ring of the first embodiment was used. The oil ring main body 11 is made of 8Cr steel, h1 is 2.0 mm, and a1 is 2.0 mm. The coil expander 12 is made by processing a round wire of 8Cr steel having an outer diameter of 1.0 mm. The tension ratio was 0.28 N / mm in all the two-piece type oil rings of the first example.

  The dimensions of the two-piece type oil ring of the first embodiment are as follows: a1 is 2.0 mm (a1 = a2), b1 is 1.36 mm, b2 is 1.2 mm (b2 / b1 = 0.88), Further, the radial width c of the chamfered portion 24 of the ring groove 21 from the outer peripheral end portion 26 to the skirt portion 28 of the piston 20 was set to 0.55 mm.

  As a conventional example, the upper and lower rail portions 1 and 2 have the same length (a1 = a2 = 2.0 mm), and the contact lengths b1 and b2 in the radial direction X between the ring groove and the upper and lower rail portions 1 and 2 are as follows. The oil ring having the same length (b1 = b2 = 1.36 mm) was used instead of the combination oil ring of the first embodiment.

[result]
When the oil consumption when the intake pipe absolute pressure in the conventional assembly structure is 10 kPa is 100, the oil consumption when the intake pipe absolute pressure is 20 kPa in the conventional example is 40.9. However, the oil consumption in the assembly structure of the first example was 30.8 at an intake pipe absolute pressure of 10 kPa and 2.3 at 20 kPa. Therefore, it was confirmed that the combination oil ring constituting the assembly structure of the first embodiment suppresses oil consumption. Table 1 summarizes the results.

DESCRIPTION OF SYMBOLS 1 Lower rail part 2 Upper rail part 3 Connection part 4 Inner peripheral groove 5 Oil return hole 6,7 Outer peripheral end 8,9 Inner peripheral end 10 Combination oil ring for internal combustion engines 11 Oil ring main body 12 Coil expander 13 Internal space 16 , 17 Peripheral taper portion 20 Piston 21 Ring groove 22 Lower surface of ring groove 23 Upper surface of ring groove 24 Chamfered portion 25 Oil drain hole 26 Outer peripheral end portion of lower surface of ring groove 27 Outer peripheral end portion of upper surface of ring groove 28 Skirt portion 29 Notch 30 Cylinder 31 Inner wall surface of cylinder 50 Assembly structure of combination oil ring for internal combustion engine

a1 Radial width of the upper rail portion arranged on the upper surface side of the ring groove a2 Radial width of the lower rail portion arranged on the lower 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 upper surface of the ring groove and the upper rail portion b2 Radial contact length of the lower surface of the ring groove and the lower rail portion c, c ′ Radial width from the outer peripheral end of the ring groove lower surface to the piston skirt h1 Axial width of the oil ring body X Radial direction X1 Radial outward X2 Radial inward Y Axial direction D1 Outer peripheral end of the lower surface of the ring groove Diameter between D2 Inner diameter of cylinder

Claims (4)

An oil ring main body in which two upper and lower rail portions projecting radially outward are connected by a connecting portion, and an inner circumferential groove formed in the radially inner center of the connecting portion to place the oil ring main body in the radial direction. Assembling the combined oil ring for an internal combustion engine in which a combined oil ring for an internal combustion engine comprising a coil expander that presses and biases outward is mounted in a ring groove formed on the outer peripheral surface of the piston and assembled in the cylinder In structure
The tension ratio obtained by dividing the tension of the combined oil ring by the cylinder inner diameter is in the range of 0.05 to 0.3 N / mm,
A chamfered portion provided at the radially outer peripheral end portion of the lower surface of the ring groove of the piston, or a notch portion provided at a radially outer peripheral end portion of the lower surface of the lower ring portion of the oil ring body,
A radial contact length between the lower surface of the ring groove and the lower rail portion is 60% to 98% of a radial contact length between the upper surface of the ring groove and the upper rail portion. A combined oil ring assembly structure for an internal combustion engine.   The assembled structure of the combined oil ring for an internal combustion engine according to claim 1, wherein the axial width of the oil ring body is 2 mm or less. An oil ring main body in which two upper and lower rail portions projecting radially outward are connected by a connecting portion, and an inner circumferential groove formed in the radially inner center of the connecting portion to place the oil ring main body in the radial direction. In a combined oil ring for an internal combustion engine comprising a coil expander that presses and urges outward, and is mounted in a ring groove formed on the outer peripheral surface of the piston,
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 in the range of 0.05 to 0.3 N / mm,
Of the two rail portions, the radial width of the lower rail portion that contacts the lower surface side of the ring groove is 60% to 98% of the radial width of the upper rail portion that contacts the upper surface side of the ring groove. A combined oil ring for an internal combustion engine.   The combined oil ring for an internal combustion engine according to claim 3, wherein an axial width of the oil ring body is 2 mm or less.

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