JP2009257478A - Piston ring structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve both of a function of not scraping up oil in the up stroke of a piston and a function of scraping down the oil in the downstroke of the piston. <P>SOLUTION: A piston ring is constituted by an outer ring 16 received by a ring groove provided on a piston 3, and a plate expander 17, and a friction material 18 with a high coefficient of friction is applied to a part where a bottom surface 13a of the ring groove and the plate expander are abutted with each other. The hysteresis due to the influence of the friction material is generated in tension variation of the expander between the up stroke and the downstroke of the piston. Therefore, the outer ring is energized by increase of the tension of the expander and the oil scraping down performance is enhanced during the downstroke of the piston, and the oil is prevented from being scraped up by reduction of the tension of the expander compared to the time of the downstroke during the up stroke of the piston, and flow-in of the oil to a combustion chamber is reduced, and an oil consumption amount is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston ring structure for an internal combustion engine.

Conventionally, a piston of an internal combustion engine is provided with a pressure ring (piston ring) that seals between the inner peripheral surface of the cylinder. The piston ring is required to have a function of passing oil (lubricating oil) between the piston ring and the cylinder inner peripheral surface when the piston is raised, and scraping off the oil on the cylinder inner peripheral surface when the piston is lowered. For example, a plate expander made of a spring material that urges the piston ring toward the cylinder inner peripheral surface is provided in a ring groove that is open in the cylinder outer peripheral surface and continuously formed in the circumferential direction. Some have achieved the above functions by setting the tension of the plate expander and the like, and the like (for example, see Patent Document 1).
JP-A-62-233567

  In order to achieve the function of passing oil (do not rake up) during the piston ascending stroke and scraping the oil during the piston descending stroke, the expander tension is set to low tension on the ascending side and high tension on the descending side. Although it is desirable, the final setting is based on the balance between oil consumption and friction. For this reason, there is a problem that it is difficult to improve the compatibility between the function of not scooping up the oil during the piston lifting stroke and the function of scraping off the oil during the piston lowering stroke.

  In order to solve such a problem and realize the improvement of both the function of not scooping up the oil during the piston lifting stroke and the function of scraping the oil during the piston lowering stroke, in the present invention, A cylinder (2) of an internal combustion engine, a piston (3) reciprocating in the axial direction in the cylinder (2), and a ring formed continuously in the circumferential direction on the outer peripheral surface (3a) of the piston (3) A piston ring structure of an internal combustion engine having a groove (13) and a piston ring (2) provided in the ring groove (13), wherein the piston ring (22) is an inner periphery of the cylinder (2). An outer ring (16) received in the ring groove (13) so as to be in sliding contact with the surface (2a), and the ring for biasing the outer ring (16) toward the inner peripheral surface (2a) of the cylinder Groove (13 An expander (17) made of a spring material disposed radially inward of the outer ring (16), and the inner peripheral surface (2a) of the cylinder is moved away from the combustion chamber (11) in the axial direction. A friction material (18) having a high friction coefficient is applied to a portion where at least one of the ring groove (13) and the outer ring (16) and the expander (17) are in contact with each other. It was supposed to be.

  In particular, the friction material (18) is preferably made of a material whose friction coefficient can be freely set.

  Thus, according to the first aspect of the present invention, the expander tension acts on the diameter-expanding side that urges the outer ring to the cylinder inner peripheral surface, and the diameter of the cylinder inner peripheral surface with respect to the outer ring in the reciprocating motion of the piston. In the piston lowering stroke, the outer ring is deformed to the reduced diameter side, the expander is also deformed to the contracted side, and the expander is slidably contacted with the bottom surface of the ring groove. The direction in which the frictional force acts is the direction that increases the tension of the expander against the outer ring. On the other hand, the expander deforms to the expansion side due to the outer ring expansion side deformation in the piston ascending stroke, and in this case, the direction of the frictional force is reversed, and the expander's tension against the outer ring is reduced. Direction. In this way, hysteresis occurs in the expander tension between the piston ascending stroke and the descending stroke, so that during the piston descending stroke, the expander tension increases, so that the oil scraping ability by the outer ring is improved and the oil recovery rate is increased. In addition, it is possible to prevent the oil from being scooped up by reducing the tension of the expander during the upward stroke of the piston, and to improve the fuel consumption by reducing the friction.

  In particular, according to claim 2, the tension difference of the expander between the piston lowering stroke and the lifting stroke can be appropriately set by setting the friction coefficient of the friction material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a main part of an internal combustion engine to which a piston structure according to the present invention is applied. In the illustrated internal combustion engine, a cylinder 2 is formed in a cylinder block 1, and a piston 3 is slidably received on an inner peripheral surface 2 a of the cylinder 2. An upper end portion of a connecting rod 5 is connected to the piston 3 via a piston pin 4, and a lower end portion of the connecting rod 5 is connected to a crankshaft 7 via a crank pin 6. The cylinder inner peripheral surface 2a is formed by a cylinder liner (not shown).

  A crankcase 8 is coupled to the lower side of the cylinder block 1, and a crank chamber 9 for accommodating the crankshaft 7 is defined by the crankcase 8 and a lower portion of the cylinder block 1. An oil pan 10 that receives oil that has dropped from above is provided on the lower side of the crankcase 8.

  FIG. 2 is an enlarged vertical cross-sectional view of a main part showing a piston ring 22 (second ring) mounted second from the combustion chamber 11 side in the plurality of piston rings mounted on the piston 3. As shown in FIG. 2, the outer peripheral surface 3a of the piston 3 is provided with a ring groove 13 that opens radially outward and is continuously formed in the circumferential direction. A known shaped outer ring 16 is received. The ring groove 13 is formed a predetermined length deeper inward in the radial direction than the width in the longitudinal section of the outer ring 16, and a bottom surface 13 a that is the deepest inner portion in the radial direction of the ring groove 13 and an inner peripheral surface of the outer ring 16. Between them, a plate expander 17 in which a plate-like spring material is formed in a polygonal C-shape is disposed. In this way, the piston ring 22 is configured.

  In addition, the outer peripheral surface shape of the outer ring 13 is formed as a tapered surface that faces a slope on the rising side of the piston 3. As a result, the oil (lubricating oil) adhering to the cylinder inner peripheral surface 2a is not raked up during the ascending stroke of the piston 3, and the oil scraping force is exerted during the descending stroke of the piston 3. Oil consumption can be reduced by reducing oil inflow into the chamber 11.

  Furthermore, the cylinder inner peripheral surface 2a of the internal combustion engine to which the present invention is applied is formed in an inverted truncated cone shape whose inner diameter gradually decreases as the distance from the combustion chamber 11 side located on the ascending side of the piston 3 increases. (R1> R2 in FIG. 1). Thereby, as shown in FIG. 2, the inclination angle of the cylinder inner peripheral surface 2a with respect to the outer peripheral surface 3a of the cylindrical piston 3 is an angle θ that opens to the piston ascending side. Note that the inverted frustoconical shape of the cylinder inner peripheral surface 2a includes the case where the combustion chamber 11 side expands due to thermal deformation because the combustion chamber 11 becomes the hottest during operation of the internal combustion engine. In that case, when the internal combustion engine is stopped, it does not have to be an inverted truncated cone shape, and may be formed into a true cylindrical shape by processing.

  3 is a cross-sectional view taken along line III-III in FIG. As described above, the inner peripheral surface of each side portion 17a between the vertices in the polygon of the polygonal C-shaped plate expander 17 comes into contact with the bottom surface 12a of the ring groove 12, and becomes each vertex in the polygon. The portion is in contact with the inner peripheral surface of the outer ring 16. The plate expander 17 is divided at a part in the circumferential direction, and is formed so as to generate a spring urging force on the radially outwardly expanding side. Further, the outer ring 16 also has a C-shaped ring shape that is divided at a part in the circumferential direction, and is formed so as to be capable of expanding and contracting in the radial direction.

  In the piston ring structure configured as described above, the inner diameter of the cylinder inner peripheral surface 2a corresponding to the outer ring 16 is reduced by the reciprocating motion of the piston 3 so that the diameter is reduced when the piston is lowered and the diameter is increased when the piston is raised. Become. Therefore, when the piston descends, the outer ring 16 is reduced in diameter, and the deformation of the outer ring 16 causes the plate expander 17 to be deformed in the direction of contraction under pressure in the reduced diameter direction. When the piston is lifted, the outer ring 16 is expanded in diameter by the restoring force, thereby reducing the pressure from the outer ring 16 side, so that the plate expander 17 is also deformed in the direction of expanding by the spring restoring force.

  According to the present invention, the ring groove 13 and the plate expander 17 are in contact with each other, that is, as shown exaggeratedly in FIG. 4, the inner peripheral surface of each side portion 17 a of the plate expander 17 and the ring groove 13. A friction material 18 having a high coefficient of friction is applied between the bottom surface 13a and the bottom surface 13a. The friction material 18 is preferably a ceramic coating material such as DLC (Diamond like Carbon). The DLC is usually used as a low friction material, but since the friction coefficient can be set freely, a DLC having a high friction coefficient (high friction) is used.

  By using the DLC having a high friction coefficient, as shown in FIG. 5, the tension (spring urging force) of the plate expander 17 can be changed with hysteresis between the upward stroke and the downward stroke of the piston 3. . As described above, when the plate expander 17 is deformed in the direction of expansion as indicated by the two-dot chain line arrow U in FIG. 4, the side portion 17 a comes to be separated from the bottom surface 13 a so that friction occurs. The acting direction of the frictional force by the material 18 is the direction shown by the two-dot chain line arrow Fu, and the tension for urging the outer ring 16 by the plate expander 17 is reduced. As a result, the tension gradually decreases from the bottom dead center to the top dead center, which is shown as “up stroke” in FIG.

  In this ascending stroke, the tension of the plate expander 17 is weak, the force for urging the outer ring 16 is weakened, and the pressing force of the outer ring 16 against the cylinder inner peripheral surface 2a is also weakened. As a result, the action of scooping up the oil is weakened, the oil (lubricating oil) adhering to the cylinder inner peripheral surface 2a is not scooped up, the oil inflow into the combustion chamber 11 can be reduced, and the oil consumption can be reduced.

  On the other hand, when the plate expander 17 is deformed in the shrinking direction as shown by the solid line arrow D in FIG. 4, the friction member 18 is in a direction in which the side portion 17a comes into contact with the bottom surface 13a. The direction in which the frictional force acts is the direction indicated by the solid arrow Fu, and the force to push back against the deformation in the direction in which the plate expander 17 contracts increases, and the outer ring 16 is energized by the plate expander 17. Tension is increased. As a result, the tension gradually increases from the top dead center to the bottom dead center shown as “down stroke” in FIG. Then, hysteresis occurs between tension changes between the “up stroke” and the “down stroke”.

  In this downward stroke, since the hysteresis component is increased in the tension of the plate expander 17, the force for urging the outer ring 16 becomes stronger than when there is no hysteresis, and the outer ring 16 is pressed against the cylinder inner peripheral surface 2a. Strength is increased. As a result, the oil scraping force in the downward stroke is increased, the oil scraping force is exerted in the downward stroke of the piston 3, and the oil inflow into the combustion chamber 11 can be reduced to reduce the oil consumption.

  The compression amount of the plate expander 17 is the minimum value Cmin at the top dead center and the maximum value Cmax at the bottom dead center. When there is no hysteresis, the jump in tension does not occur at the maximum value Cmax and the minimum value Cmin of the compression amount. In the present invention, however, the friction material 18 causes a change with hysteresis as shown in FIG. It becomes.

  Thus, it is possible to prevent the oil from being scraped up during the piston ascending stroke, and it is easy to scrape off the oil during the piston descending stroke, and the oil remains on the cylinder inner peripheral surface 2a during the expansion stroke or is necessary when the piston 3 is raised. It is possible to prevent the oil from being carried as described above, and the oil consumption can be reduced. Furthermore, since the urging force against the outer ring 16 during the upward stroke of the piston 3 can be weakened, fuel consumption can be improved by reducing friction.

  The location where the friction material 18 is applied is not limited to the portion where the bottom surface 13a and the side portion 17a are in contact with each other, but can be applied to both the inner and outer peripheral surfaces of the plate expander 17 or on the inner peripheral surface of the outer ring 16. It may be applied or a combination thereof.

  In the illustrated example, one plate expander 17 is provided. However, as shown in FIG. 6, two plate expanders 17 and 19 may be provided. Thereby, the friction material 18 can be apply | coated between both plate expanders 17 and 19, and the hysteresis effect by the friction material 18 can be improved further. Further, a single plate expander having a friction material by frictional force between the plate expanders 17 and 19 or between the plate expander 17 and the bottom surface 13a can be obtained by the friction force between them (in the above embodiment). Frictional force effect equivalent to that of (form) can be obtained.

  The piston ring structure of the internal combustion engine according to the present invention has the effect of improving the oil scraping ability and preventing the oil from being scraped up, such as an outboard motor having a crankshaft as a vertical direction. It can also be applied to marine propulsion engine.

It is sectional drawing which shows the principal part of the internal combustion engine to which the piston structure by this invention is applied. It is a principal part expansion longitudinal cross-sectional view which shows a piston ring. It is sectional drawing which shows the plate expander and outer ring seen along the arrow III-III line of FIG. It is a figure which expands and shows the principal part of FIG. It is a figure explaining the hysteresis effect | action of a plate expander. It is a figure which shows the structure which made the expander double.

Explanation of symbols

2 Cylinder 2a Cylinder inner peripheral surface (inner peripheral surface)
3 piston 3a outer peripheral surface 13 ring groove 16 outer ring 17 plate expander (expander)
18 Friction material 22 Piston ring

Claims (2)

A cylinder of an internal combustion engine, a piston that reciprocates in the axial direction within the cylinder, a ring groove formed continuously in the circumferential direction on the outer peripheral surface of the piston, and a piston ring provided in the ring groove A piston ring structure for an internal combustion engine,
The outer ring received in the ring groove so that the piston ring is in sliding contact with the inner peripheral surface of the cylinder, and the outer ring of the ring groove to urge the outer ring toward the inner peripheral surface side of the cylinder And an expander made of a spring material arranged radially inward of
The inner peripheral surface of the cylinder is formed such that the inner diameter gradually decreases as the distance from the combustion chamber increases in the axial direction,
A piston ring structure for an internal combustion engine, wherein a friction material having a high friction coefficient is applied to a portion where at least one of the ring groove and the outer ring and the expander are in contact with each other.   The piston ring structure for an internal combustion engine according to claim 1, wherein the friction material is made of a material whose friction coefficient can be freely set.

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