JP2010222985A - Piston ring and internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring suppressing friction with a piston on which the piston ring is adopted under a condition where lubricating oil is used while securing sealing performances with a groove wall of the piston on which the piston ring is adopted, and to provide an internal combustion engine including the piston ring, securing required sealing performances, and reducing friction between the piston ring and a cylinder bore by improving following properties of the piston ring to a cylinder inner surface. <P>SOLUTION: The piston ring 10 is used under the condition where lubricating oil L is used, and a notch part 82 for accelerating formation of oil film between the piston ring 10 and a lower groove face 50A of the piston 30 on which the piston ring 10 is adopted is formed at an angular corner section of the inner circumference surface 10B and a lower surface 10A which are in low pressure side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a piston ring and an internal combustion engine provided with the piston ring.

  There is known a technique for preventing aluminum adhesion of the piston ring or realizing low friction by forming a coating on the upper and lower surfaces of the piston ring (see, for example, Patent Documents 1 to 3). In addition, a technique is known in which a radially inward force and an outward force acting on a piston ring due to gas pressure cancel each other (see, for example, Patent Document 4).

JP 2003-307154 A JP 2006-138329 A JP 2006-22666 A JP 2008-14214 A

  However, when used under lubricating oil conditions, the friction between the piston ring and the piston ring groove is dominated by the influence of the oil film formation state rather than the boundary friction coefficient between these sliding elements and the solid friction coefficient. It becomes the target. Therefore, there is still room for improvement with respect to the friction reduction between the piston ring and the piston ring groove under the use conditions of the lubricating oil as compared with the conventional techniques of Patent Documents 1 to 3. Moreover, in the prior art described in Patent Document 4, there is room for improvement from the viewpoint of the sealing performance of the piston ring.

  In consideration of the above facts, the present invention provides a piston ring that can suppress friction with a piston that is applied under conditions using a lubricating oil while ensuring sealing performance with the applied piston groove wall. The purpose is to obtain. In addition, the present invention provides an internal combustion engine that includes the above-described piston ring, ensures required sealing performance, and improves the followability of the piston ring to the inner surface of the cylinder to reduce the friction between the piston ring and the cylinder bore. Is the purpose.

  The piston ring according to the first aspect of the invention is used under a condition using lubricating oil, and promotes oil film formation between the groove wall of the applied piston at the corner on the low pressure side and the inner peripheral side. A notch is formed for this purpose.

  In the piston ring according to the first aspect, a notch is formed at the corner on the low-pressure side, that is, the side that is pressed against the groove wall facing the high-pressure side of the piston and on the inner peripheral side. For this reason, in this piston ring, when moving inward in the radial direction, the solid contact friction is suppressed by the oil film pressure based on the wedge effect of the lubricating oil that has entered the notch, that is, the minute gap, or has entered the notch. The pressing force (friction drag) on the groove wall is reduced by the fluid pressure from the high pressure side, and the radial friction against the piston is reduced. Thereby, the followability of the piston ring to the cylinder bore is improved, and the friction loss between the piston ring and the cylinder bore is reduced. In addition, since the notch is provided on the inner peripheral side of the piston ring, the piston ring is pressed against the groove wall of the piston in other parts such as the radial intermediate part and the outer peripheral part, and sealability with the groove wall of the piston Can be secured.

  Thus, in the piston ring according to the first aspect, it is possible to suppress the friction with the piston applied under the condition using the lubricating oil while ensuring the sealing performance with the applied piston groove wall. In addition, this piston ring is applicable to an internal combustion engine, an external combustion engine, a reciprocating compressor, etc., for example.

  A piston ring according to a second aspect of the present invention is the piston ring according to the first aspect, wherein three or more notches are formed along the circumferential direction.

  In the piston ring according to claim 2, since three or more cutout portions are provided along the circumferential direction, in other words, a non-formed portion of the cutout portion is located between the cutout portions adjacent to each other in the circumferential direction. Therefore, when the pressure from the high pressure side is received, the posture is stabilized by contacting (adjacent) the groove wall in the above-described three or more non-formed portions. For this reason, it is suppressed that the dimension of a notch part changes in each part of the circumferential direction resulting from the twist of a piston ring, etc., and said friction reduction effect can be acquired stably.

  A piston ring according to a third aspect of the present invention is the piston ring according to the second aspect, wherein the non-formed portion of the notch portion is arranged at at least one of both circumferential end portions forming the joint.

  In the piston ring according to the third aspect, since the non-formed portion of the notch portion is arranged on at least one side in the circumferential direction with respect to the joint, the posture is more stably stabilized when receiving pressure from the high pressure side. For this reason, it becomes possible to acquire the above-mentioned friction reduction effect more stably.

  The piston ring according to a fourth aspect of the present invention is the piston ring according to any one of the first to third aspects, wherein the notch has a smaller dimension in the ring thickness direction than a dimension in the ring radial direction. Has been.

  In the piston ring according to the fourth aspect, the projected area on the inner peripheral side (groove bottom) is sufficiently smaller than the projected area on the groove wall on the low pressure side of the piston. For this reason, formation of the oil film that causes the oil film pressure of the lubricating oil to be generated in the piston ring thickness direction (toward the high-pressure side in the piston axial direction) is promoted.

  A piston ring according to a fifth aspect of the present invention is the piston ring according to the fourth aspect, wherein a tapered surface having a gradient of 1/1000 to 1/10 is formed by the notch.

  6. The piston ring according to claim 5, wherein the oil film of the lubricating oil is formed on the tapered surface having a gradient in which the ratio of the dimension in the thickness direction facing the inner peripheral side to the dimension in the radial direction facing the low pressure side is 1/1000 to 1/10. Pressure mainly acts. Thereby, the oil film pressure does not suddenly change in the radial direction (piston ring width direction), and a stable oil film can be formed.

  A piston ring according to a sixth aspect of the present invention is the piston ring according to the fourth aspect, wherein a surface facing the groove wall is formed in a curved shape that protrudes most toward the groove wall at a substantially central portion in a ring radial direction. Thus, the notch is formed on the inner peripheral side with respect to the central portion in the radial direction.

  In the piston ring of the sixth aspect, the substantially central portion in the width direction of the piston ring protrudes most into the groove wall on the low pressure side of the piston, and the inner peripheral side with respect to this portion is a wedge-shaped notch. This piston ring rolls so that the contact position with the groove wall changes in the width direction in a cross-sectional view at a right angle in the circumferential direction, thereby allowing a seal with the piston groove wall (substantially linear contact state) while allowing deformation in the ring torsional direction. ) Can be secured.

  The piston ring according to a seventh aspect of the present invention is the piston ring according to the fourth aspect, wherein the notch is formed as a recess recessed stepwise with respect to the surface facing the groove wall.

  In the piston ring according to the seventh aspect, the oil film pressure mainly acts on the step portion (boundary portion) between the general surface on the low pressure side and the surface facing the low pressure side of the recess. This oil film can suppress friction with the piston.

  The piston ring according to an eighth aspect of the present invention is the piston ring according to any one of the first to seventh aspects, wherein a dimension in the ring thickness direction at the notch is 1 μm or more and 0.1 mm or less. Yes.

  In the piston ring according to claim 8, since the dimension in the oil film thickness direction is 0.1 mm or less, the wedge effect of the lubricating oil is likely to be favorably generated as it moves inward in the radial direction, and the groove wall of the piston The formation of a good oil film that can reduce the friction is promoted.

  The internal combustion engine according to claim 9 has a cylinder and a plurality of ring grooves arranged in parallel in the axial direction, and is provided in the cylinder so as to be capable of reciprocating in the axial direction, thereby forming the combustion chamber with the cylinder. A piston, and a piston ring according to any one of claims 1 to 8, which is mounted in a ring groove arranged closest to the combustion chamber in the piston.

  In the internal combustion engine according to claim 9, the compression stroke / expansion stroke of the piston ring attached to the ring groove located closest to the combustion chamber side, that is, the high pressure side of the piston is compared with those attached to the other ring grooves. Thus, it is pressed against the ring groove of the piston with high pressure from the combustion chamber side. Here, since the piston ring according to any one of claims 1 to 8 is attached to the ring groove, the friction between the ring groove and the piston ring is small. For this reason, in this internal combustion engine, the piston ring follows the cylinder inner surface (shape variation) well, and the required sealing performance is ensured.

  Thus, in the internal combustion engine according to claim 9, the piston ring is provided to ensure the required sealing performance, improve the followability of the piston ring to the cylinder inner surface, and reduce the friction between the piston ring and the cylinder bore. be able to.

  As described above, the piston ring according to the present invention can suppress the friction with the piston applied under the condition using the lubricating oil while ensuring the sealing performance with the applied piston groove wall. Has an excellent effect.

  Further, the internal combustion engine according to the present invention includes the above-described piston ring, and can ensure the required sealing performance, improve the followability of the piston ring to the cylinder inner surface, and reduce the friction between the piston ring and the cylinder bore. It has an excellent effect.

It is a figure which shows the piston ring which concerns on the 1st Embodiment of this invention, Comprising: (A) is a circumferential direction orthogonal cross-sectional view, (B) is a bottom view. It is a figure for demonstrating the friction reduction effect of the piston ring which concerns on the 1st Embodiment of this invention, Comprising: (A) is sectional drawing in case a lubricating oil is filled into a notch part, (B) is a notch It is sectional drawing in case the lubricating oil is not filled in the part. 1 is a schematic cross-sectional view of an engine to which a piston ring according to a first embodiment of the present invention is applied. It is a diagram which shows the experimental result of the friction reduction effect at the time of using the piston ring which concerns on the 1st Embodiment of this invention, comparing with a comparative example. It is a diagram which shows the analysis result of the friction reduction effect at the time of using the piston ring which concerns on the 1st Embodiment of this invention, comparing with a comparative example. It is a figure which shows typically the cylinder used for the experiment and analysis for showing the friction reduction effect at the time of using the piston ring which concerns on the 1st Embodiment of this invention, Comprising: (A) is a cylinder which considered the deformation | transformation (B) is a perspective view of the cylinder which does not consider deformation. It is a figure for demonstrating the dimension setting basis of the notch part of the piston ring which concerns on the 1st Embodiment of this invention, Comprising: (A) is sectional drawing which shows the model of a piston ring, (B) is an oil film force and an oil film It is a diagram which shows the relationship between a thickness coefficient and an oil film width coefficient. FIG. 6 is a cross-sectional view perpendicular to the circumferential direction of a piston ring according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view perpendicular to the circumferential direction of a piston ring according to a third embodiment of the present invention. It is a bottom view of the piston ring which concerns on the 4th Embodiment of this invention. It is a bottom view of the piston ring which concerns on the 5th Embodiment of this invention. It is a bottom view of the piston ring which concerns on the 6th Embodiment of this invention.

  A piston ring 10 and an engine 11 as an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. First, the general overall configuration of the engine 11 will be described, and then the piston ring 10 will be described.

(Schematic overall configuration of the engine)
FIG. 3 shows a cross-sectional view along a plane orthogonal to the axis of the crankshaft 12 in the engine 11. As shown in this figure, the engine 11 includes a cylinder block 14, an oil pan 16 joined to the lower part of the cylinder block 14, a cylinder head 18 joined to the upper part of the cylinder block 14, and an upper part of the cylinder head 18. The cylinder head cover 20 is joined.

  The lower part of the cylinder block 14 and the oil pan 16 constitute a crankcase 24 in which a crank chamber 22 in which the crankshaft 12 is accommodated is formed. A piston 30 disposed in the cylinder 28 of the cylinder block 14 so as to be displaceable in the axial direction of the cylinder 28 is connected to the crankshaft 12 of the engine 11 via a connecting rod 26.

  A combustion chamber C in which fuel is combusted is formed by the piston 30, the cylinder 28 of the cylinder block 14, and the cylinder head 18. A cooling water passage 14 </ b> A for circulating engine cooling water is formed on the side of the cylinder 28 in the cylinder block 14.

  The inner surface of the cylinder 28 of the cylinder block 14 and the piston 30 are sealed with piston rings 10, 32, and 33. In this embodiment, the piston ring 10 is a top ring of a compression ring, the piston ring 32 is a second ring of the compression ring, and the piston ring 33 is an oil ring.

  The cylinder head 18 is provided with an intake port 34 for introducing a mixture of gasoline and air into the cylinder 28 and an exhaust port 36 for discharging combustion exhaust gas (exhaust gas) from the cylinder 28. The intake port 34 is opened and closed by an intake valve 38 at a portion communicating with the cylinder 28. The intake valve 38 is driven by an intake cam 44 of a valve operating system 42 through a valve stem 38A protruding into a cylinder head chamber 40 formed by the cylinder head 18 and the cylinder head cover 20.

  Similarly, the exhaust port 36 is configured to be opened and closed by an exhaust valve 46 at a portion communicating with the cylinder 28. The exhaust valve 46 is driven by an exhaust cam 48 of the valve operating system 42 via a valve stem 46A protruding into the cylinder head chamber 40. The intake cam 44 and the exhaust cam 48 are rotated in synchronization with the driving force of the crankshaft 12 transmitted via a timing sprocket, a timing chain, etc. (not shown).

  In the engine 11, the lubricating oil L in the oil pan 16 is supplied to the crankshaft 12, the piston 30, the connecting rod 26, and the valve train 42 by an oil pump (not shown) so that each sliding portion is lubricated. It has become. Lubricating oil used for lubricating each sliding portion (lubricated portion) is returned to the oil pan 16 by gravity or the like.

  In this embodiment, the engine 11 is a row type engine in which a plurality of cylinders 28 are formed in a cylinder block 14.

(Structure of piston ring)
1B shows a bottom view of the piston ring 10, and FIG. 1A shows a cross-sectional view perpendicular to the circumferential direction of the piston ring 10. As shown in FIG. In addition, the arrow R shown in the drawing indicates the radial direction of the piston 30 that substantially matches the width direction of the piston ring 10, and the arrow T indicates the thickness direction of the piston ring 10.

  As shown in FIG. 1 (B), the piston ring 10 has an abutment 52 at one place in the circumferential direction, and is formed in a substantially C shape when viewed in the axial direction of the piston 30. The shape of the joint 52 can be selected as appropriate. The piston ring 10 is mounted in a ring groove 50 formed in the piston 30 as shown in FIG.

  In this state, the piston ring 10 is pressed against the inner surface of the cylinder 28 of the cylinder block 14 by its own restoring force. That is, the piston ring 10 is kept pressed against the cylinder 28 as the piston 30 reciprocates with respect to the cylinder 28 of the cylinder block 14. In other words, it is possible to follow the deformation of the cylinder 28 as will be described later. Note that, as shown in FIG. 2A, an oil film Fsl of lubricating oil is formed between the cylinder 28 and the piston ring 10.

  1A and 1B, the surface of the piston ring 10 facing the combustion chamber C side, that is, the side opposite to the high-pressure side when mounted on the ring groove 50 (hereinafter referred to as the lower surface for convenience). Notches 54 are formed at the corners of 10A and the inner peripheral surface 10B. That is, the notch 54 opposes the lower groove wall 50A facing the lower surface 10A of the piston ring 10 in the ring groove 50 (facing the combustion chamber C side), and the inner peripheral surface 10B of the piston ring 10 in the ring groove 50 ( It is formed so as to open toward both sides of the groove bottom 50B (facing radially outward).

  More specifically, as shown in FIG. 1 (A), the notch 54 in this embodiment has a lower groove wall 50A and a groove bottom 50B at the corners of the lower surface 10A and the inner peripheral surface 10B of the piston ring 10. The taper surface 10C which faces both is formed. The tapered surface 10 </ b> C can also be grasped as the bottom surface of the notch 54. The taper surface 10C is set so that the width W1 projected onto the lower groove wall 50A is sufficiently larger than the height H projected onto the groove bottom 50B (W1 >> H) in a cross-sectional view perpendicular to the circumferential direction. . In this embodiment, the ratio of the height H to the width W1 (H / W1) that is 0.001 mm ≦ H ≦ 0.1 mm and the gradient of the tapered surface 10C is in the range of 1/1000 to 1/10. , Approximately 1/200.

The setting of the height H will be supplemented with reference to FIGS. 7A and 7B. As shown in FIG. 7A, the distance (oil film thickness) in the direction of arrow T between the lower surface 10A of the piston ring 10 and the lower groove wall 50A is h0, the height of the notch 54 (tapered surface 10C) with respect to h0. When the ratio of H is K (H = K × h0) and the ratio of the width W1 to the sum of the width W1 and the width W2 is λ (W1 = λ × (W1 + W2)), the oil film pressure Pf generated in the wedge-shaped oil film Fpl The resultant force (oil film force) P is
P λ λ ² ln (1 + K) / K ² + A / B
However, A = Kλ (1-λ ² ) -2λ ² {(2 / K) +3 (1-λ)}
B = 4 + 2 (4-3λ) K + 4 (1-λ) K ²
It is said. The resultant force P is plotted with respect to K and λ as shown in FIG. 7B (see A. Cameron “Principles of lubrication” Longman 1966 Chapter 6-7 p. 143). It can be seen from FIG. 7B that a large oil film pressure Pf is obtained when λ is in the range of 1/2 to 4/5 and K is in the range of 1.0 to 2.0.

  Here, in this embodiment, the distance between the lower surface 10A and the lower groove wall 50A, that is, the minimum oil film thickness h0 is unknown, but in reality, when the lower surface 10A and the lower groove wall 50A start to contact each other. It is estimated that the average gap, that is, the sum of the surface roughness of the lower surface 10A and the lower groove wall 50A is about 1 to 5 μm. Further, h0 in a state where the lower surface 10A is lifted from the lower groove wall 50A by the oil film pressure is estimated to be about 20 μm. Therefore, since the gap height H of the notch 54 is K = 1.0 to 2.0 as described above, it is approximately 1 to 10 μm (median value is approximately 5 μm) at the start of the contact, up to the oil film formation state. In consideration, it is about 1 to 40 μm. Further, according to FIG. 7B, since a sufficient oil film pressure generation effect is recognized up to about K = 5, in this embodiment, the gap height H of the notch 54 is 1 to 100 μm (optimum value 5 μm). It was. When the width W1≈1 mm (= 1000 μm) is converted into the slope (H / W1) of the tapered surface 10C, 1/1000 to 1/10 (optimum value 1/200) is obtained as described above.

  In the piston ring 10, the width W1 of the tapered surface 10C is such that the portion of the lower surface 10A where the tapered surface 10C is not formed is opposed to the lower groove wall 50A of the ring groove 50 (overlapping in the radial direction). , And is set so as to ensure a predetermined width or more. In this embodiment, a setting that satisfies the wrap width W2 ≧ 1 mm is employed. The total width W of the piston ring 10 is 2 to 4 mm.

  The cutout 54 described above is formed over the entire length in the circumferential direction of the lower surface 10A of the piston ring 10 (excluding the joint 52), as shown in FIG.

  As described above, the piston ring 10 that is the top ring is mounted in the ring groove 50 located closest to the combustion chamber C in the piston 30 as shown in FIG. As shown in FIGS. 2 (A) and 2 (B), there is a lubricating oil between the lower surface 10A of the piston ring 10 (at least the portion of the wrap width W2) and the lower groove wall 50A of the ring groove 50 in the piston 30. An L oil film Fpl is formed. FIG. 2 schematically shows a state in the intake stroke.

  The other piston rings 32 and 33 (particularly, the piston ring 32 which is a compression ring) constituting the engine 11 may be configured in the same manner as the piston ring 10, but in this embodiment, the configuration does not include the notch 54. Has been. The piston rings 32 and 33 are independently attached to ring grooves (not shown) formed closer to the crank chamber 22 than the ring groove 50.

  Next, the operation of the first embodiment will be described.

  In the engine 11 configured as described above, for example, the reciprocating linear motion of the piston 30 is converted into the rotational motion of the crankshaft 12 by repeating the suction stroke, the compression stroke, the expansion stroke, and the exhaust stroke in this order. Occurs. In addition, the intake cam 44 and the exhaust cam 48 are driven to rotate by the rotation of the crankshaft 12, and the intake valve 38 and the exhaust valve 46 are driven to maintain the intake stroke, compression stroke, expansion stroke, and exhaust stroke.

  During the operation of the engine 11, the cylinder 28 is usually deformed so that its inner diameter is larger than that of the crank chamber 22 side, which is relatively low pressure on the combustion chamber C side. Further, in the engine 11 that is a row type engine, the circumferential deformation is caused by the assembly fastening force of the cylinder block 14. The piston ring 10 is displaced relative to the piston 30 (ring groove 50) in a direction perpendicular to the axis, that is, in a substantially radial direction so as to follow the cylinder 28 deformed as described above.

  When the frictional force accompanying the relative displacement between the piston ring and the piston 30 is large, the relative displacement of the piston ring with respect to the piston 30, that is, the follow-up operation of the piston ring with respect to the inner surface of the cylinder 28 (cylinder bore) deformed as described above is restricted. Cheap. In particular, in the compression stroke and the expansion stroke, the piston ring as the top ring attached to the ring groove 50 of the piston 30 is relatively displaced in the ring groove 50 following the inner surface of the cylinder 28 deformed as described above. The lower surface is strongly pressed against the lower groove wall 50A side of the ring groove 50 by the pressure Pc of the combustion chamber C acting on the upper surface (see FIGS. 2A and 2B). As a result, the frictional drag is increased, and a problem that the follow-up operation of the piston ring to the cylinder 28 (relative displacement inward in the radial direction) is easily caused by friction.

  Here, since the piston ring 10 is provided with the notches 54 at the corners of the lower surface 10A and the inner peripheral surface 10B, in other words, the tapered surface 10C is formed by providing the notches 54. Therefore, friction in the radial direction with respect to the piston 30 is reduced.

  That is, as shown in FIG. 2A, when the piston ring 10 is relatively displaced radially inward with respect to the piston 30 in an expansion stroke or the like in a state where the notch 54 is filled with the lubricating oil L, fluid lubrication ( The oil film pressure Pf is generated by the wedge effect, and the piston ring 10 is lifted (floated) to the combustion chamber C side. As a result, the solid contact friction between the lower surface 10A of the piston ring 10 and the lower groove wall 50A of the ring groove 50 is suppressed, and the viscous friction (shear) component of the lubricating oil L becomes dominant, that is, the friction coefficient A reduction effect is obtained, and friction in the radial direction of the piston ring 10 with respect to the piston 30 is reduced.

  On the other hand, as shown in FIG. 2B, when the lubricating oil L is not filled in the notch portion 54, the pressure Pc of the combustion chamber C in the compression stroke or the expansion stroke acts around the tapered surface 10C. . For this reason, the pressing force to the lower groove wall 50A applied to the piston ring 10 is canceled based on the pressure Pc of the combustion chamber C acting on the upper surface 10D by the area projected from the taper surface 10C in the axial direction, that is, the frictional drag. This reduces the friction of the piston ring 10 against the piston 30 in the radial direction.

  As described above, the piston ring 10 has good followability with respect to the inner surface of the cylinder 28 because friction due to relative change in the radial direction with the applied piston 30 is reduced under the condition using the lubricating oil L. . In particular, in the piston ring 10, the notch portion 54 is continuously formed over the entire length, so that a friction reducing effect can be obtained at each portion in the circumferential direction of the cylinder 28. On the other hand, the non-formed portion of the tapered surface 10C on the lower surface 10A of the piston ring 10 has a wrap width W2 with respect to the lower groove wall 50A of a predetermined width or more, so that the lower groove wall of the piston ring 10 and the lower groove wall of the piston 30 are secured. Gas sealing performance between 50A is also ensured.

  In the engine 11 to which the above-described piston ring 10 is applied, the required sealing performance between the cylinder 28 and the piston 30 can be ensured by ensuring the followability of the piston ring 10 with respect to the cylinder 28, and the bottom surface. In the configuration in which the cutouts 54 are provided at the corners of 10A and the inner peripheral surface 10B, the gas sealing property between the lower surface 10A and the lower groove wall 50A is also ensured as described above. That is, the engine 11 can obtain a required sealing performance by applying the piston ring 10.

  Further, in the piston ring 10, the friction reducing effect can be realized as described above by simple machining such as forming the notch portions 54 at the corners of the lower surface 10A and the inner peripheral surface 10B.

  Next, the friction reduction effect of the piston ring 10 will be supplemented with reference to the experimental results shown in FIG. 4 and the analysis results shown in FIG. The experiment measured the relationship between the crank angle and the instantaneous friction torque between the piston ring 10 and the cylinder 28 using a rapid compression / expansion device. The analysis was performed by the piston ring behavior-lubricated coupled analysis CAE. The relationship between the angle and the instantaneous friction torque between the piston ring 10 and the cylinder 28 is analyzed.

  FIG. 6A shows a deformed cylinder 28 (corresponding model) having an inner diameter enlarged on the combustion chamber C side than on the crank chamber 22 side, which was used in the above experiments and analyses. The cylinder 28 has a radius difference ΔR between the minimum diameter portion and the maximum diameter portion of approximately 50 μm. FIG. 6B shows a perfect circular cylinder 28 (equivalent model) used for comparison with a constant inner diameter over the entire length.

  As shown in FIG. 4, when the deformation cylinder 28 is used and when the perfect circle cylinder 28 is used, a normal piston ring (corresponding to one having no notch portion 54) according to the comparative example is used for the top ring. Compared to the configuration, the piston ring 10 (corresponding to the configuration in which the friction coefficient is reduced compared to the comparative example by setting the lubrication conditions, etc.) is used for the top ring, the instantaneous friction torque is significantly increased in the expansion stroke. It can be seen that it is reduced. In the compression stroke, although no significant difference is observed in the deformation cylinder 28, it is understood that the instantaneous friction torque is reduced by using the piston ring 10 in the perfect circle cylinder 28.

  Further, as shown in FIG. 5, when the deforming cylinder 28 is used or when the perfect circular cylinder 28 is used, the normal piston ring (corresponding to the one not having the notch portion 54) according to the comparative example is used as the top ring. Compared to the configuration used, the configuration using the piston ring 10 (corresponding to the comparative example with a smaller friction coefficient compared to the comparative example) for the top ring significantly reduces the instantaneous friction torque in the expansion stroke. I understand. In this respect, it can be said that this analysis result agrees well with the experimental result. In this analysis, in the case of a perfect cylinder, no significant difference was found between the normal piston ring (corresponding to the one not having the notch 54) and the piston ring 10.

  As described above, by reducing the friction in the radial direction of the piston ring with respect to the piston 30, that is, by adopting the piston ring 10 having the notch portion 54 as the piston ring, the piston ring 10 can be obtained in an environment using the lubricating oil L. The friction between the piston 30 and the piston 30 is effectively suppressed. As a result, the followability to the cylinder 28 is improved, and the friction loss between the piston ring 10 and the cylinder 28 is reduced by both experiments and numerical analysis. It was confirmed.

  That is, in this embodiment, since the friction between the lower surface of the piston ring 10 and the ring groove 50 is reduced, the followability of the piston ring 10 to the cylinder 28 is improved, and in addition to ensuring the sealing performance, the piston ring 10 The friction between the cylinder 28 and the cylinder 28 can also be reduced. In particular, in the upper deformation bore shown in FIG. 6 (A), the piston ring tends to deform in the direction of being compressed in the ring groove during the expansion stroke. Here, the piston ring lower surface, the ring groove, When the friction is large, the above deformation is restrained, the attrition between the piston ring and the cylinder becomes strong, and the friction between the piston ring and the cylinder becomes large. On the other hand, in the engine 11 according to the embodiment of the present invention, since the friction between the lower surface of the piston ring 10 and the ring groove 50 is reduced, the deformation in the direction in which the piston ring 10 is compressed in the ring groove 50. , And the attack strength between the piston ring 10 and the cylinder 28 is lowered to an appropriate level. As a result, in the engine 11, friction between the piston ring 10 and the cylinder 28 during the expansion stroke is reduced.

  Thus, in the piston ring 10 according to the first embodiment, the lubricating oil L is supplied while ensuring the sealing performance with the ring groove 50 of the applied piston 30 and the sealing performance between the piston 30 and the cylinder 28. Friction with the piston 30 can be suppressed under the conditions used. In addition, the engine 11 includes the piston ring 10 to ensure the required sealing performance and improve the followability of the piston ring 10 to the inner surface of the cylinder 28 to reduce friction between the piston ring 10 and the cylinder bore 28. can do.

  Further, in the piston ring 10, since the notch 54 forms a gently tapered surface 10C (the bottom surface of the notch 54 is the tapered surface 10C), there is no sudden change in the oil film pressure Pf in the radial direction. A stable oil film can be formed.

  Next, another embodiment of the present invention will be described. Note that components / portions that are basically the same as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof may be omitted, and illustration may be omitted.

(Second Embodiment)
FIG. 8 shows a piston ring 60 according to the second embodiment in a circumferential cross-sectional view corresponding to FIG. 1 (A). As shown in this figure, the lower surface 60A of the piston ring 60 facing the lower groove wall 50A of the ring groove 50 is a curved surface (barrel shape) that protrudes toward the lower groove wall 50A. In this embodiment, the lower surface 60 </ b> A of the piston ring 60 is a top portion 60 </ b> B whose substantially central portion in the width direction protrudes most toward the lower groove wall 50 </ b> A. The top portion 60B is set (arranged) located in a range that overlaps the lower groove wall 50A on the lower surface 60A in the radial direction.

  The piston ring 60 has a substantially linear contact with the lower groove wall 50A of the piston 30 (the linear narrow width portion is the closest part to the lower groove wall 50A), so that the seal between the piston ring 60 and the lower groove wall 50A is obtained. It is designed to ensure sex. For example, even if the piston ring 60 is twisted with the reciprocating motion of the piston 30 with respect to the cylinder 28, the width direction contact (closest approach) portion to the lower groove wall 50 </ b> A at each portion in the circumferential direction is partially different in the circumferential direction. By rolling in a cross-sectional view so as to be different from a part of the above, the line contact state with respect to the lower groove wall 50A as a whole (almost the entire circumference) is maintained.

  In the piston ring 60 described above, a space located on the inner peripheral side with respect to the top portion 60B of the lower surface 60A, more precisely, a space located on the inner peripheral side with respect to the line contact (closest approach) portion to the lower groove wall 50A is notched. Part 62 is provided. Accordingly, in the piston ring 60, the portion of the lower surface 60A located on the inner peripheral surface 60C side with respect to the top portion 60B, more precisely, the portion on the inner peripheral surface 60C side with respect to the line contact (closest) portion to the lower groove wall 50A. The portion is a pressure receiving surface 60D (surface corresponding to the tapered surface 10C) that receives the oil film pressure Pf or the pressure Pc of the combustion chamber C.

  In this embodiment, the pressure receiving surface 60D has a width W3 projected onto the lower groove wall 50A sufficiently larger than the height H projected onto the groove bottom 50B (W3 >> H) in the circumferential cross-sectional view. It is set. In this embodiment, 0.001 mm ≦ H ≦ 0.1 mm. Further, in the piston ring 60, the width W3 of the pressure receiving surface 60D has a ratio (H / W3) to the height H in the range of 1/1000 to 1/10, and is approximately 1/200. . The total width W of the piston ring 60 is 2 to 4 mm.

  The notch 62 described above is formed over the entire circumferential length of the lower surface 60 </ b> A (portion excluding the joint 52) of the piston ring 60. The other structure in the piston ring 60 is the same as the corresponding structure of the piston ring 10 including a portion not shown.

  And also in the piston ring 60 according to the second embodiment, when the lubricating oil L is filled in the notch 62, the friction coefficient reduction effect is obtained by the pressure receiving surface 60D receiving the oil film pressure Pf, When the notch 62 is not filled with the lubricating oil L, an effect of reducing the friction coefficient is obtained by the pressure receiving surface 60D receiving the pressure Pc of the combustion chamber C. Therefore, even with the piston ring 60 and the engine 11 including the piston ring 60, the same effect can be obtained basically by the same operation as the piston ring 10 and the engine 11 according to the first embodiment.

  Further, since the piston ring 60 is configured to seal between the lower groove wall 50A of the ring groove 50 in a line contact state over substantially the entire circumference, the piston ring 60 is compared with a configuration sealed in a surface contact state. Even when the ring is twisted or the like, the sealing performance between the ring groove 50 and the lower groove wall 50A is easily secured. Further, in the piston ring 60, since the notch 62 forms a gently curved pressure receiving surface 60D (the bottom surface of the notch 62 is the pressure receiving surface 60D), a sudden change portion of the oil film pressure Pf is generated in the radial direction. And a stable oil film can be formed.

(Third embodiment)
FIG. 9 shows a piston ring 70 according to the third embodiment in a circumferential cross-sectional view corresponding to FIG. 1 (A). As shown in this figure, a notch 72 is formed at the corner of the piston ring 70 between the lower surface 70A facing the lower groove wall 50A of the ring groove 50 and the inner peripheral surface 70B facing the groove bottom 50B. Yes.

  That is, the notch 72 faces the lower groove wall 50A facing the lower surface 70A of the piston ring 70 in the ring groove 50 (facing the combustion chamber C side) and the inner peripheral surface 70B of the piston ring 70 in the ring groove 50 ( It is formed so as to open toward both sides of the groove bottom 50B (facing radially outward).

  More specifically, the notch 72 in this embodiment forms a downward surface 70C facing the lower groove wall 50A at the corner between the lower surface 70A and the inner peripheral surface 70B of the piston ring 70. The downward surface 70C is set so that the width W4 projected onto the lower groove wall 50A is sufficiently larger than the height H projected onto the groove bottom 50B (W4 >> H) in a cross-sectional view perpendicular to the circumferential direction. . In this embodiment, the ratio of the height H to the width W4 (H / W4) that is 0.001 mm ≦ H ≦ 0.1 mm and the gradient of the downward surface 70C is in the range of 1/1000 to 1/10. , Approximately 1/200.

  Further, in the piston ring 70, the width W4 of the downward surface 70C is such that the portion of the lower surface 70A where the downward surface 70C is not formed is opposed to the lower groove wall 50A of the ring groove 50 (overlapping in the radial direction). , And is set so as to ensure a predetermined width or more. In this embodiment, a setting that satisfies the wrap width W5 ≧ 1 mm is employed. The total width W of the piston ring 70 is 2 to 4 mm.

  The cutout 72 described above is formed over the entire length in the circumferential direction of the lower surface 70A (portion excluding the joint 52) of the piston ring 70, as shown in FIG. Other configurations of the piston ring 70 are the same as the corresponding configurations of the piston ring 10 including portions not shown.

  And even in the piston ring 70 according to the third embodiment, when the notch 72 is filled with the lubricating oil L, the friction coefficient reduction effect is obtained by the downward surface 70C receiving the oil film pressure Pf, When the lubricating oil L is not filled in the notch 62, the friction coefficient reduction effect is obtained by the downward surface 70C receiving the pressure Pc of the combustion chamber C. Therefore, the piston ring 70 and the engine 11 equipped with the piston ring 70 also basically have the piston according to the first embodiment except for the operational effect of the notched portion 54 forming the gently tapered surface 10C. The same effect can be obtained by the same operation as the ring 10 and the engine 11. 80

(Fourth embodiment)
FIG. 10 shows a piston ring 80 according to the fourth embodiment in a bottom view corresponding to FIG. As shown in this figure, the piston ring 80 is elongated in the circumferential direction of the piston ring 80 and spaced apart from the circumferential direction of the piston ring 80 in place of the notch 54 formed over the substantially entire length of the piston ring 10. The piston ring 10 is different from the piston ring 10 according to the first embodiment in that it has four notches 82 arranged.

  The non-processed part (the non-formed part of the notch part 82) between the notch parts 82 adjacent in the circumferential direction on the lower surface 80A of the piston ring 80 is referred to as a seat part 84. The two cutouts 82 separated in the circumferential direction at the joint 52 are set so that the sum of the circumferences is substantially equal to the circumference of the other two cutouts 82. It is also possible to capture. Thereby, in the piston ring 80, the three seat parts 84 are arrange | positioned in the circumferential direction at substantially equal intervals (at intervals of about 120 degrees).

  In the piston ring 80, the circumferential length of the seat portion 84 is set to be sufficiently shorter than the circumferential length of the notch portion 82. The circumferential length of the seat portion 84 is set as a lower limit value within a range in which the posture of the piston ring 80 is stabilized by seating (contacting) the lower groove wall 50A of the ring groove 50 in each seat portion 84. . The cross-sectional shape of the notch portion 82 in this embodiment is the same as the cross-sectional shape of the notch portion 54 according to the first embodiment. That is, the piston ring 80 has a tapered surface 80 </ b> C that can be grasped as a bottom surface of the notch 82 at the corner between the lower surface 80 </ b> A and the inner peripheral surface 80 </ b> B. Other configurations of the piston ring 80 are the same as the corresponding configurations of the piston ring 10 including a portion not shown.

  Therefore, the piston ring 80 according to the fourth embodiment can basically obtain the same effect by the same operation as the piston ring 10 according to the first embodiment. Further, the engine 11 including the piston ring 70 can basically obtain the same effect by the same operation as that of the engine 11 according to the first embodiment.

  Further, in the present piston ring 80, since three or more seats 84 are arranged at substantially equal intervals in the circumferential direction, when the pressure Pc on the combustion chamber C side is received, first the ring in the three seats 84 is provided. The posture is stabilized by contacting the lower groove wall 50A of the groove 50 (adjacent to the oil film). For this reason, the piston ring 80 is restrained from changing (differentiating) the dimensions of the tapered surface 80C (such as the oil film pressure Pf and the pressure receiving area of the pressure Pc) due to its torsion and the like in each part in the circumferential direction. The above-described friction reduction effect can be stably obtained.

(Fifth embodiment)
FIG. 11 shows a piston ring 90 according to the fifth embodiment in a bottom view corresponding to FIGS. 1 (B) and 10. As shown in this figure, the piston ring 90 is different from the piston ring 10 according to the fourth embodiment in that the seat portion 84 is disposed adjacent to the joint 52 in the circumferential direction.

  Specifically, in the piston ring 90, three cutout portions 82 having the same peripheral length are arranged apart from each other in the circumferential direction, and the abutment 52 is located between the two cutout portions 82. And in the piston ring 90, the non-formation part of the notch part 82, ie, the seat part 84, is provided in the both sides of the circumferential direction with respect to the joint 52, respectively.

  When the pair of seats 84 sandwiching the joint 52 in the circumferential direction is regarded as one seat 84, the piston ring 90 grasps that a total of three seats 84 are arranged at substantially equal intervals in the circumferential direction. Can do. Further, it may be considered that four seats 84 are arranged at unequal intervals in the circumferential direction. Other configurations of the piston ring 90 are the same as the corresponding configurations of the piston ring 80, including a portion not shown (the lower surface 80A, the inner peripheral surface 80B, the lower surface 90A corresponding to the tapered surface 80C, the inner periphery Surface 90B and tapered surface 90C).

  Therefore, the piston ring 90 according to the fifth embodiment can basically obtain the same effect by the same operation as the piston ring 80 according to the fourth embodiment. Further, the engine 11 including the piston ring 90 can basically obtain the same effect by the same operation as that of the engine 11 according to the fourth embodiment.

  Moreover, in the piston ring 90, since the seat part 84 is arrange | positioned adjacent to the abutment 52, in other words, the seat part 84 is arrange | positioned in the vicinity of the part which the piston ring 90 tends to produce comparatively fluttering. Therefore, the posture is further stabilized when the pressure Pc on the combustion chamber C side is received. In particular, the posture of the piston ring 90 in which 84 is disposed adjacent to both sides in the circumferential direction of the joint 52 is further stabilized when receiving the pressure Pc on the combustion chamber C side. As a result, the piston ring 90 is restrained from changing the dimension of the tapered surface 90C at each portion in the circumferential direction due to its twist or the like, and the above-described friction reduction effect can be obtained more stably.

(Sixth embodiment)
FIG. 12 shows a piston ring 100 according to the sixth embodiment in a bottom view corresponding to FIG. As shown in this figure, the piston ring 100 is common to 90 according to the fifth embodiment in that the seat portion 84 is disposed adjacent to the joint 52 in the circumferential direction. The piston ring 90 is different from the piston ring 90 provided with a total of three seat portions 84 (which can be regarded as four as described above) in that the portion 84 is provided.

  Specifically, in the piston ring 100, a pair of seats 84 adjacent to each other at short intervals in the circumferential direction are provided in three pairs (total of six) so as to be substantially equally spaced in the circumferential direction. Like the piston ring 90, the pair of seats 84 among the three pairs are arranged so as to sandwich the joint 52 in the circumferential direction. A notch 82 having a short circumference is formed between the two pairs of seats 84 excluding this pair. The other configurations of the piston ring 100 are the same as the corresponding configurations of the piston rings 80 and 90, including portions not shown (the lower surface 100A corresponding to the lower surface 80A, the inner peripheral surface 80B, and the tapered surface 80C of the piston ring 80, An inner peripheral surface 100B and a tapered surface 100C).

  Therefore, even with the piston ring 100 according to the sixth embodiment, basically the same effect can be obtained by the same operation as the piston rings 80 and 90 according to the fourth and fifth embodiments. Further, the engine 11 including the piston ring 100 can basically obtain the same effect by the same operation as the engine 11 according to the first embodiment.

  In addition, since the piston ring 100 is provided with a total of three pairs of seat portions 84 which are separated in the circumferential direction to form a pair, for example, while reducing the total circumferential length of each seat portion 84 as compared with the piston ring 90, for example. It is possible to obtain equivalent posture (sitting) stability.

  In the fourth to sixth embodiments described above, the example in which the seat portion 84 is provided between the notches 82 adjacent to each other in the circumferential direction is shown. However, the present invention is not limited to this, and for example, the third portion The seat 84 may be provided between the notches 72 in the embodiment.

  In the fifth to sixth embodiments described above, the example in which the seat portions 84 are disposed adjacent to both sides in the circumferential direction with respect to the joint 52 has been described. However, the present invention is not limited thereto, and for example, the joint The seat portion 84 may be adjacently arranged only on one circumferential side of the 52.

  Furthermore, in the above-described fourth to sixth embodiments, an example in which three (three pairs) seats 84 are arranged apart from each other in the circumferential direction has been shown, but the present invention is not limited to this, for example, Alternatively, a configuration may be adopted in which four or more seat portions 84 are provided at regular intervals or at irregular intervals apart from each other in the circumferential direction.

  Furthermore, in each of the above-described embodiments, an example in which the piston rings 10, 60, and 70 are applied to the engine 11 that is an internal combustion engine has been described. However, the present invention is not limited to this, and for example, an external combustion engine or a reciprocating engine. The piston rings 10, 60, 70, 80, 90, 100 may be applied to a dynamic (reciprocating) compressor or the like.

10 piston ring 10C taper surface 11 engine (internal combustion engine)
30 Piston 50 Ring groove 50A Lower groove wall 54 Notch 60/70/80/90/100 Piston ring 62/72/82 Notch 84 Seat (not-formed part of notch)

Claims (9)

  Piston ring which is used under conditions using lubricating oil and has a notch for promoting oil film formation between the groove wall of the applied piston at the corner on the low pressure side and on the inner peripheral side .   The piston ring according to claim 1, wherein three or more notches are formed along a circumferential direction.   The piston ring according to claim 2, wherein a non-formed portion of the notch portion is disposed at at least one of both circumferential end portions forming a joint.   The piston ring according to any one of claims 1 to 3, wherein the notch has a dimension in the ring thickness direction smaller than a dimension in the ring radial direction.   The piston ring according to claim 4, wherein a tapered surface having a gradient of 1/1000 to 1/10 is formed by the notch.   The surface facing the groove wall is formed in a curved shape that protrudes most toward the groove wall in a substantially central portion in the ring radial direction, so that the cutout portion is formed on the inner peripheral side with respect to the central portion in the radial direction. The piston ring according to claim 4.   The piston ring according to claim 4, wherein the notch is formed as a recess recessed stepwise with respect to the surface facing the groove wall.   The piston ring according to any one of claims 1 to 7, wherein a dimension of the cutout portion in a ring thickness direction is 1 µm or more and 0.1 mm or less. A cylinder,
A piston having a plurality of ring grooves arranged in parallel in the axial direction, provided in the cylinder so as to be capable of reciprocating in the axial direction, and forming the combustion chamber with the cylinder;
The piston ring according to any one of claims 1 to 8, wherein the piston ring is mounted in a ring groove arranged closest to the combustion chamber in the piston.
Internal combustion engine equipped with.

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