JP6480709B2 - Piston ring and engine including the piston ring - Google Patents

Description

  The present disclosure relates to a piston ring and an engine including the piston ring.

  For example, a marine two-cycle engine includes a cylinder and a crankcase, and a piston is disposed in the cylinder so as to be able to reciprocate, and a crankshaft is rotatably disposed in the crankcase. The piston and the crankshaft are connected to each other via a piston rod, a crosshead, and a connecting rod, and the crankshaft is rotationally driven by the reciprocating motion of the piston.

  The piston ring is mounted in a piston ring groove formed on the outer periphery of the piston. The piston ring is elastic and slidably contacts the inner peripheral surface of the cylinder with an appropriate surface pressure. This piston ring suppresses the pressure in the combustion chamber formed by the piston, the cylinder inner circumferential surface and the cylinder head from leaking through the gap between the piston outer circumferential surface and the cylinder inner circumferential surface.

  The piston ring has a ring shape, and has a discontinuous portion called a joint portion in a part in the circumferential direction. The joint portion of the gas tight type piston ring has a concave portion provided on one end side in the circumferential direction of the piston ring and a convex portion provided on the other end side. The outer diameter of the piston ring is larger than the diameter of the inner peripheral surface of the cylinder. When the piston ring is disposed in the cylinder with the piston ring attached to the piston, the outer diameter of the piston ring is fitted so that the concave portion and the convex portion overlap each other. The concave portion and the convex portion have a radially outer surface (outer peripheral surface) located on the radially outer side of the piston ring, and these outer peripheral surfaces are in sliding contact with the cylinder inner peripheral surface.

  As this type of gas tight piston ring, for example, Patent Document 1 discloses a piston ring capable of preventing a breakage accident at the joint portion by cutting out a part of the joint portion of the piston ring. . Specifically, in the piston ring of Patent Document 1, the moment in the reciprocating direction acting on the joint portion is reduced by cutting out a part of the joint portion, and the fracture resistance at the base portion of the joint portion is reduced. improves.

Japanese Utility Model Publication No. 3-53006

In the gas tight type piston ring, there is a problem that the outer peripheral surface of the convex portion slidably contacting the inner peripheral surface of the cylinder is easily damaged in the vicinity of the tip of the concave portion.
In view of the above circumstances, at least one embodiment of the present invention aims to provide a gas-tight piston ring with improved durability and an engine including the piston ring.

In order to achieve the above object, the present inventors have intensively studied and obtained the following knowledge regarding the mechanism of damage to the outer peripheral surface of the recess in the gas tight type piston ring.
During engine operation, the piston ring is heated by the combustion gas and becomes hot. At this time, since the outer peripheral side of the piston ring is in sliding contact with the relatively low temperature inner peripheral surface of the cylinder, the temperature on the inner peripheral side of the piston ring is higher than the temperature on the outer peripheral side. Due to the temperature difference between the inner and outer peripheral sides of the piston ring, the amount of thermal expansion of the piston ring is greater on the inner peripheral side than on the outer peripheral side. As a result, in the gas tight piston ring, the joint portion is thermally deformed so as to swell radially outward of the piston ring.

Due to such thermal deformation, the contact surface pressure between the radially outer surface (outer peripheral surface) of the concave portion (first tongue portion) and the convex portion (second tongue portion) constituting the joint portion and the inner peripheral surface of the cylinder is increased. For this reason, uneven wear tends to occur on the inner peripheral surface of the cylinder in the vicinity of the joint portion.
In particular, when the piston is located in the vicinity of the top dead center, the relative speed of the piston with respect to the inner peripheral surface of the cylinder becomes zero, and an oil film is easily cut between the piston ring and the inner peripheral surface of the cylinder. Since the explosion and the pressure and temperature of the combustion chamber increase, the sliding condition between the piston ring and the cylinder inner peripheral surface becomes severe. For this reason, the vicinity of the top dead center of the cylinder inner peripheral surface is unevenly worn so as to spread toward the cylinder head. That is, the vicinity of the top dead center of the cylinder inner peripheral surface is unevenly worn so as to be inclined with respect to the cylinder axis.

  The piston ring is fitted into the piston ring groove with a gap, and when the cylinder inner peripheral surface is inclined due to wear in this way, the piston ring falls down corresponding to the inclination. That is, the outer peripheral surface of the piston ring is inclined along the inner peripheral surface of the cylinder.

  When the piston ring is thermally deformed, the tip angle at which the tip surface and the outer peripheral surface of the first tongue portion intersect strongly comes into contact with the inner peripheral surface of the cylinder. In particular, when the piston ring falls due to uneven wear of the cylinder inner peripheral surface, the outer peripheral surface of the first tongue portion comes into stronger contact with the cylinder inner peripheral surface. When the tip angle of the first tongue hits the cylinder inner peripheral surface locally in this manner, the cylinder inner peripheral surface is greatly dented and affected by the second tongue in the vicinity of the tip angle of the first tongue. A gap is formed between the outer peripheral surface of the part and the inner peripheral surface of the cylinder.

In particular, when the outer diameter of the piston ring is enlarged due to wear of the cylinder inner peripheral surface, and the circumferential distance between the tip angle of the first tongue and the tip angle of the second tongue is short, the first tongue The second tongue cannot be deformed so as to block the recess of the cylinder inner peripheral surface formed by the tip angle of the portion, and between the cylinder inner peripheral surface and the second tongue near the tip angle of the first tongue. The gap becomes larger. Then, high-temperature and high-pressure combustion gas blows through the large gap at a high speed, and the outer peripheral surface of the second tongue portion is damaged.
On the contrary, the tip angle of the second tongue portion may be in strong contact with the inner peripheral surface of the cylinder, and a large gap may be generated between the outer peripheral surface of the first tongue portion and the inner peripheral surface of the cylinder. In this case, high-temperature and high-pressure combustion gas blows through the large gap at a high speed, and the outer peripheral surface of the first tongue portion is damaged.

The present inventors who have obtained knowledge about the mechanism of damage to the outer peripheral surface of the recess described above have further studied and have come up with the present invention.
(1) The piston ring according to at least one embodiment of the present invention is:
A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in at least one of the first tongue, the second tongue, and the main body,
Each of the first tongue portion and the second tongue portion has a tip corner portion located on the outer side in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of the portion including the tip corner portion of the first tongue portion or the second tongue portion with respect to a moment around an axis parallel to the axis.

  According to the configuration (1), since the rigidity of the portion including the tip corner portion of the first tongue portion or the second tongue portion is reduced by the at least one slit, the contact of the tip corner portion with the inner peripheral surface of the cylinder is reduced. The pressure is reduced. For this reason, generation | occurrence | production of a big dent in the cylinder internal peripheral surface in the front-end | tip corner part vicinity is prevented, and a big clearance gap generate | occur | produces between the outer surface of a 2nd tongue part or a 1st tongue part, and a cylinder internal peripheral surface. Is prevented. As a result, combustion gas is prevented from being blown out, and damage to the outer surface of the second tongue portion or the first tongue portion is suppressed.

(2) In some embodiments, in the configuration (1),
The first tongue portion is located on the inner side in the radial direction and has an inner peripheral wall portion having a portion facing the second tongue portion, and protrudes radially outward from the inner peripheral wall portion, and the second tongue portion, A seal wall portion facing in the axial direction,
The at least one slit includes a circumferential slit formed in the seal wall,
The circumferential slit extends along the circumferential direction from the tip of the seal wall portion in the circumferential direction, and divides the tip side of the seal wall portion into two regions adjacent in the radial direction.

  According to the configuration (2), the circumferential slit formed in the seal wall portion reliably reduces the rigidity of the first tongue portion including the tip corner portion with a simple configuration.

(3) In some embodiments, in the configuration (2),
A through hole penetrating the seal wall portion in the axial direction;
The through hole expands the width of the end of the slit located on the main body side in the circumferential direction.

According to the configuration (3), since the width of the end portion of the slit is enlarged by the through hole formed in the seal wall portion, the stress concentration in the vicinity of the peripheral end portion of the slit is alleviated. For this reason, it is possible to prevent breakage of the portion with reduced rigidity while reducing the rigidity of the portion of the first tongue portion including the tip corner portion.
Moreover, the rigidity of the part of the 1st tongue part containing a front-end | tip corner part can be further reduced because the width | variety of the terminal part of a slit was expanded. Alternatively, if the rigidity is the same, the slit length in the circumferential direction can be shortened by increasing the width of the end portion of the slit. If the length of the slit can be shortened, the outer diameter of the piston ring expands due to wear on the inner peripheral surface of the cylinder, and the length of the region where the first tongue and the second tongue overlap each other is shortened. However, it is possible to reliably prevent the combustion gas from leaking through the slit.

(4) In some embodiments, in the configuration (2) or (3),
Regarding the portion including the tip corner portion of the first tongue, the Young's modulus is E, the cross-sectional secondary moment about the axis parallel to the axis is I, and the moment acting around the axis parallel to the axis is M. Sometimes, the length in the circumferential direction and the position in the radial direction of the circumferential slit are determined so that M / EI falls within the range of 0.00012644 or more and 0.00316097 or less.

  According to the configuration (4), since the M / EI is 0.00012644 or more and 0.00316097 or less, the portion including the tip corner portion of the first tongue portion is easily deformed with respect to the moment, and in the vicinity of the tip corner portion. It is possible to reliably prevent the occurrence of a large dent on the cylinder inner peripheral surface.

(5) In some embodiments, in any one of the configurations (2) to (4),
The distance from the outer surface of the seal wall portion to the circumferential slit in the radial direction is 7 mm or less.
According to the said structure (5), the distance from the outer surface of a seal wall part to the circumferential slit is 7 mm or less, and the rigidity of the part containing the front-end | tip corner part of a said 1st tongue part can fully be reduced. .

(6) In some embodiments, in any one of the configurations (2) to (5),
The circumferential slit has a length of 15 mm or less in the circumferential direction.
According to the configuration (6), since the length of the circumferential slit in the circumferential direction is 15 mm or less, the slit is longer than the length of the region where the first tongue and the second tongue overlap each other. Can be made sufficiently short. For this reason, even if the outer diameter of the piston ring expands due to wear on the inner peripheral surface of the cylinder and the length of the region where the first tongue and the second tongue overlap each other becomes shorter, the combustion gas through the slits Can be reliably prevented.

(7) In some embodiments, in any one of the configurations (1) to (6),
The at least one slit includes a radial slit formed on at least one of the one end side in the circumferential direction of the main body and the first tongue,
The radial slit extends along the radially outer side from the one end side in the circumferential direction of the main body or the radially inner side of the first tongue.

  According to the configuration (7), the radial slit formed in at least one of the one end side and the first tongue portion of the main body portion can be configured with a simple configuration of the portion of the first tongue portion including the tip corner portion. The rigidity is reliably reduced.

(8) In some embodiments, in any one of the configurations (1) to (7),
According to the said structure (8), the rigidity of the part of the 2nd tongue part containing a front-end | tip corner part is reliably reduced by a simple structure by the 2nd circumferential direction slit formed in the 2nd tongue part. The

(9) In some embodiments, in any one of the configurations (1) to (8),
The at least one slit includes a second radial slit formed in at least one of the other end side and the second tongue portion of the main body portion,
The second radial slit extends along the radial direction from the inner surface of the main body portion on the other end side or the radial direction of the second tongue portion.

  According to the configuration (9), the second tongue including the tip corner portion can be simply configured by the second radial slit formed in at least one of the other end side of the main body portion and the second tongue portion. The rigidity of the portion is reliably reduced.

(10) An engine according to at least one embodiment of the present invention includes:
A cylinder,
A piston capable of reciprocating in the cylinder and forming a combustion chamber in the cylinder;
A piston ring according to any one of (1) to (9) mounted on the piston is provided.

  According to the configuration (10), since the piston ring has excellent durability, the engine also has excellent durability.

  According to at least one embodiment of the present invention, a gas tight type piston ring with improved durability and an engine including the piston ring are provided.

1 is a cross-sectional view schematically showing a configuration of an engine according to an embodiment of the present invention. It is sectional drawing which expands and shows roughly the cylinder jacket vicinity in FIG. FIG. 3 is a perspective view schematically showing a piston ring in FIG. 2. FIG. 4 is an enlarged plan view schematically showing a region IV in FIG. 3 together with a cylinder. It is a perspective view showing roughly the 1st tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 1st tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 1st tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 1st tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 1st tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 2nd tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 2nd tongue part of the piston ring concerning some embodiments. It is a perspective view showing roughly the 2nd tongue part of the piston ring concerning some embodiments. It is a top view which shows roughly the front end surface of the 1st tongue part of FIG. 5 when it sees along the circumferential direction. It is a top view which shows roughly the front end surface of the 1st tongue part in which the slit is not formed. It is a figure for demonstrating the moment which acts with respect to the beam-shaped member of a one end fixed other end support structure. It is a figure for demonstrating the relationship between a curvature radius, a Young's modulus, and a cross-sectional secondary moment when a moment acts on a beam-shaped member. It is a graph which shows the relationship between the length of a slit, and M / EI.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an engine 1 according to an embodiment of the present invention. The engine 1 is, for example, a marine two-cycle large diesel engine. The engine 1 includes a base plate 2 positioned below, a frame 3 provided on the base plate 2, and a cylinder jacket 4 provided on the frame 3. The base plate 2, the frame 3, and the cylinder jacket 4 are connected to each other by a plurality of tie bolts 5 extending in the vertical direction.

The bottom of the base plate 2 is closed by the bottom plate 6, and the upper part of the frame 3 is closed by the bottom wall of the cylinder jacket 4. The base plate 2 and the bottom plate 6 form a crank chamber, and a crank shaft 8 is disposed in the crank chamber.
The base plate 2 rotatably supports the journal portion 9 of the crankshaft 8, and the lower end portion of the connecting rod 11 is connected to the crankpin 10 of the crankshaft 8. The upper end portion of the connecting rod 11 is connected to the lower end portion of the piston rod 13 via the cross head 12. On both sides of the cross head 12, a sliding plate 14 extending in the vertical direction is provided, and the vertical movement of the cross head 12 is guided by the sliding plate 14.

  The piston rod 13 extends vertically through a seal hole provided in the bottom wall of the cylinder jacket 4. The cylinder jacket 4 is fitted with the lower end side of a cylinder (cylinder liner) 15, and the upper end side of the piston rod 13 is inserted into the cylinder liner 15. A piston 16 is fixed to an upper end portion of the piston rod 13, and the piston 16 can reciprocate in the cylinder liner 15 in the vertical direction.

FIG. 2 is an enlarged cross-sectional view schematically showing the vicinity of the cylinder jacket 4.
As shown in FIG. 2, a cylinder cover (cylinder head) 17 is disposed on the cylinder liner 15, and the cylinder cover 17 is covered with the cylinder jacket 4 by a cover bolt 18 with the upper end side of the cylinder liner 15 being sandwiched. It is concluded to.
The cylinder cover 17, the cylinder liner 15, and the piston 16 form a combustion chamber 19 on the upper end side of the cylinder liner 15. The cylinder cover 17 is provided with an exhaust port 20 that opens to the combustion chamber 19, and the exhaust port 20 is opened and closed by an exhaust valve 21. A fuel injection valve 22 is attached to the cylinder cover 17.

  A scavenging port 23 that can communicate with the combustion chamber 19 when the piston 16 is located near the bottom dead center is formed on the lower end side of the cylinder liner 15, and the scavenging port 23 is surrounded inside the cylinder jacket 4. A scavenging chamber 24 is formed as described above. A gland packing 25 is disposed between the seal hole in the bottom wall of the cylinder jacket 4 and the piston rod 13, and the space between the scavenging chamber 24 and the frame 3 is sealed by the gland packing 25.

  Referring again to FIG. 1, a turbocharger 26 is provided on a frame supported by the frame 3 and the cylinder jacket 4 in order to send compressed air into the scavenging chamber 24. The turbocharger 26 includes a compressor 27 and a turbine 28 that are coaxially connected to each other. The discharge port of the compressor 27 and the scavenging chamber 24 communicate with each other via an air conduit 29 and a scavenging trunk chamber 30. Inside the air conduit 29, a water-cooled air cooler 31 for cooling the compressed air discharged from the compressor 27 and a water droplet separator 32 for removing water droplets from the cooled air are arranged. . In addition, a backflow prevention door 33 is disposed at a connection portion between the air conduit 29 and the scavenging trunk chamber 30.

On the other hand, the exhaust port 20 is connected to an exhaust static pressure pipe 34, and the exhaust static pressure pipe 34 is connected to the inlet of the turbine 28. The dynamic pressure of the exhaust gas discharged from the combustion chamber 19 is converted into a static pressure by the exhaust static pressure pipe 34, and the turbine 28 is driven by the static pressure of the exhaust gas and outputs torque. The compressor 27 is driven by the torque output from the turbine 28 and compresses and discharges air.
For example, when the engine 1 has six cylinders, six cylinder liners 15 and pistons 16 are provided, and six combustion chambers 19 are connected to one exhaust static pressure pipe 34. The turbines 28 of the two turbochargers 26 are connected to one exhaust static pressure pipe 34.

  The engine 1 described above is a uniflow type two-cycle engine, and a scavenging (supplying) process, a compression process, a combustion process, and an expansion process are performed while the piston 16 makes one reciprocation. Specifically, when the piston 16 comes near the bottom dead center, the combustion chamber 19 and the scavenging port 23 communicate with each other, compressed air (cleaning air) is supplied from the scavenging port 23 into the combustion chamber 19, and the exhaust port 20. The combustion gas is discharged from. While the piston 16 is moving up, air is compressed in the combustion chamber 19 and fuel is injected into the combustion chamber 19, and the fuel is combusted when the piston 16 comes close to top dead center. Thereafter, while the piston 16 is descending, the combustion gas expands, and before the piston 16 reaches the vicinity of the bottom dead center, the exhaust port 20 is opened and the discharge of the combustion gas is started. Thereafter, the ascent process is repeated again.

  In the engine 1 described above, a plurality of piston rings 40 are mounted on the outer periphery of the piston 16 as shown in FIG. Specifically, a plurality of piston ring grooves 41 are formed in the outer peripheral portion of the piston 16, and each piston ring 40 is fitted in the piston ring groove 41. The axis of the piston ring 40 coincides with the axis CL of the cylinder liner 15 and the piston 16.

  The piston ring 40 protrudes outward from the outer peripheral surface of the piston 16 in the radial direction of the piston 16, and has an outer peripheral surface that is in sliding contact with the inner peripheral surface (cylinder inner peripheral surface) 42 of the cylinder liner 15. Therefore, the gap between the cylinder inner peripheral surface 42 and the outer peripheral surface of the piston 16 is closed by the piston ring 40, and the piston ring 40 can prevent the combustion gas from leaking from the combustion chamber 19.

  FIG. 3 is a perspective view schematically showing the piston ring 40. As shown in FIG. 3, the piston ring 40 includes a main body portion 44, and a first tongue portion 48 and a second tongue portion 50 that form a joint portion 46. The main body 44 extends along a circumferential direction around the axis CL (hereinafter also simply referred to as a circumferential direction). In the following, the direction along the axis CL is also simply referred to as the axial direction, and the radial direction of the piston ring 40, that is, the radial direction of the main body 44 is also simply referred to as the radial direction.

FIG. 4 is a plan view schematically showing the region IV in FIG. 3 together with the cylinder liner 15 in an enlarged manner. As shown in FIG. 4, the first tongue portion 48 extends from the one end surface 52 of the main body portion 44 toward the other end surface 54 in the circumferential direction. The first tongue portion 48 includes an inner peripheral wall portion 56 and a seal wall portion 58 that are integral with each other.
The inner peripheral wall portion 56 forms the radially inner side of the first tongue portion 48, and the seal wall portion 58 protrudes outward in the radial direction from the axial combustion chamber 19 side of the inner peripheral wall portion 56. The inner peripheral wall portion 56 and the seal wall portion 58 have an L-shaped cross-sectional shape in a cross section orthogonal to the circumferential direction, and form a fitting recess 60 extending along the circumferential direction. In the first tongue portion 48, the fitting recess 60 is located on the radially outer side and on the cross head 12 side (frame 3) side in the axial direction.

  The second tongue portion 50 extends from the other end surface 54 of the main body portion 44 in the circumferential direction, and the sectional shape of the second tongue portion 50 is formed in a rectangular shape in the circumferential cross section. The second tongue 50 has a radial inner surface facing the radially outer surface of the inner peripheral wall 56 on the axial combustion chamber 19 side, and an axial direction facing the side surface of the seal wall 58 on the axial frame 3 side. It has a side surface on the combustion chamber 19 side. In a state where the piston ring 40 is mounted on the piston 16, the first tongue 48 and the second tongue 50 form a gas tight joint 46 by fitting the second tongue 50 into the fitting recess 60. To do. In the joint portion 46, the outer peripheral surface of the piston ring 40 is formed by the radially outer surface 64 of the first tongue portion 48 and the radially outer surface 66 of the second tongue portion 50.

  More specifically, the radially outer surface 64 of the first tongue portion 48 is located outside in the radial direction of the main body portion 44 and faces outward in the radial direction. The radially outer surface 64 of the first tongue 48 extends along the circumferential direction, and is opposed to the cylinder inner circumferential surface 42 when the piston ring 40 is attached to the piston 16. Hereinafter, the radially outer surface 64 of the first tongue portion 48 is also referred to as an outer peripheral surface 64. The outer peripheral surface 64 of the first tongue portion 48 is the outer surface of the seal wall portion 58.

  Similarly, the radially outer surface 66 of the second tongue portion 50 is located outside in the radial direction of the main body portion 44 and faces radially outward. The radially outer surface 66 of the second tongue 50 extends along the circumferential direction, and is opposed to the cylinder inner circumferential surface 42 when the piston ring 40 is mounted on the piston 16. Hereinafter, the radially outer surface 66 of the second tongue 50 is also referred to as an outer peripheral surface 66.

  In a state where the second tongue portion 50 is fitted in the fitting recess 60 of the first tongue portion 48, the circumferential front end surface 68 of the first tongue portion 48 faces the other end surface 54 of the main body portion 44 with a gap. The distal end surface 70 in the circumferential direction of the second tongue 50 faces the one end surface 52 of the main body 44 with a gap. Even if the piston ring 40 is heated and expanded by the combustion gas and expands in the circumferential direction due to these gaps, the expansion in the circumferential direction can be absorbed.

By providing such a gap between the one end surface 52 of the main body portion 44 and the circumferential front end surface 70 of the second tongue portion 50, the first tongue portion 48 and the second tongue portion 50 are provided in the joint portion 46. There is a non-overlapping region S1 that does not overlap in the axial direction in the vicinity of the root of the first tongue 48. Similarly, by providing a gap between the circumferential front end surface 68 of the first tongue portion 48 and the other end surface 54 of the main body portion 44, the first tongue portion 48 and the second tongue portion 50 are provided in the joint portion 46. There is a non-overlapping region S <b> 2 that does not overlap in the axial direction in the vicinity of the root of the second tongue 50. On the other hand, in the abutment portion 46, an overlapping region S3 where the first tongue portion 48 and the second tongue portion 50 overlap in the axial direction exists between the two non-overlapping regions S1 and S2.
For example, the initial length along the circumferential direction of the overlapping region S3 is 1% or more and 4% or less of the initial inner diameter of the cylinder liner 15 that is the sliding object of the piston ring 40.

5 to 9 are perspective views schematically showing the first tongue portion 48 of the piston ring 40 according to some embodiments. 10 to 12 are perspective views schematically showing the second tongue portion 50 of the piston ring 40 according to some embodiments.
As shown in FIGS. 5 to 12, the first tongue portion 48 and the second tongue portion 50 are respectively provided with tip corner portions 72 and 74 that are located outside in the radial direction and located on the tip side in the circumferential direction. Have. At the tip corner portion 72 of the first tongue portion 48, the tip surface 68 and the outer surface 64 intersect. Similarly, the front end surface 70 and the outer surface 66 intersect at the front end corner portion 74 of the second tongue 50. The tip surfaces 68 and 70 and the outer surfaces 64 and 66 do not need to intersect at right angles, and may intersect via curved surfaces. That is, the tip corner portions 72 and 74 may be subjected to R processing.

  As shown in FIGS. 5 to 12, in some embodiments, the piston ring 40 is formed on at least one of the first tongue 48, the second tongue 50, and the main body 44. One slit 76 (76A to 76G) is provided. The slit 76 can be formed by, for example, cutting. The slit 76 reduces the rigidity of the portion including the tip corner portion 72 of the first tongue portion 48 or the portion including the tip corner portion 74 of the second tongue portion 50 with respect to the moment around the axis parallel to the axis CL. ing.

  According to this configuration, the rigidity of the portion including the tip corner portion 72 of the first tongue portion 48 or the portion including the tip corner portion 74 of the second tongue portion 50 is reduced by the at least one slit 76. The contact pressure of the tip corner portion 72 or 74 with respect to the cylinder inner peripheral surface 42 is reduced. For this reason, it is prevented that a large dent is generated in the cylinder inner peripheral surface 42 in the vicinity of the tip corner portion 72 or 74, and the outer surface 66 of the second tongue 50 or the outer surface 64 of the first tongue 48 and the inner periphery of the cylinder. Generation of a large gap between the surface 42 is prevented. As a result, the combustion gas is prevented from being blown out, and damage to the outer surface 66 of the second tongue 50 or the outer surface 64 of the first tongue 48 is suppressed.

In some embodiments, as shown in FIGS. 5 and 6, the at least one slit 76 includes a circumferential slit 76 </ b> A formed in the seal wall 58. The circumferential slit 76A extends along the circumferential direction from the distal end side of the seal wall portion 58 in the circumferential direction, and divides the distal end side of the seal wall portion 58 into two regions adjacent in the radial direction.
For example, the circumferential slit 76 </ b> A penetrates the seal wall portion 58 in the axial direction, opens on both sides of the seal wall portion 58 in the axial direction, and opens on the distal end surface 68.

According to this configuration, the circumferential slit 76A formed in the seal wall portion 58 reliably reduces the rigidity of the first tongue portion 48 including the tip corner portion 72 with a simple configuration.
Here, the rigidity reduction by the slit 76 will be described in detail. FIG. 13 is a plan view schematically showing the distal end surface 68 of the first tongue portion 48 of FIG. 5 when viewed along the circumferential direction. Similarly, FIG. 14 is a plan view schematically showing the distal end surface 68 of the first tongue portion 48 where the slit 76 is not formed. FIG. 15 is a diagram for explaining the moment M acting on the beam-like member having the one-end fixed other-end support structure. FIG. 16 is a diagram for explaining the relationship among the radius of curvature ρ, the Young's modulus E, and the cross-sectional secondary moment I when the moment M acts on the beam-shaped member.

As shown in FIG. 13, the distal end side of the first tongue portion 48 is divided into a radially outer portion 80 and a radially inner portion 82 by the slit 76 </ b> A. The radial outer portion 80 including the tip corner portion 72 of the first tongue portion 48 is hatched, and the cross-sectional secondary moment I of the radial outer portion 80 is determined by the size of the hatched region. The
When the slit 76A is not formed, as shown in FIG. 14, the cross-sectional secondary moment I of the first tongue 48 is determined by the size of the hatched region.

  On the other hand, the moment acting on the radially outer portion 80 can be calculated in the same manner as in the case of the beam-like member of the one-end fixed other-end support structure because the tip corner portion 72 abuts on the cylinder inner peripheral surface 42. . As shown in FIG. 15, a moment M acts on the beam-shaped member having the one-end fixed other-end support structure when a load is applied uniformly in the longitudinal direction of the member. When a certain moment M acts on the member, as shown in FIG. 16, the member is bent and deformed at a curvature (1 / ρ = E / MI) determined in accordance with the sectional secondary moment I and Young's modulus E of the member. To do.

  As apparent from a comparison between FIG. 13 and FIG. 14, with respect to the axial direction, the cross-sectional secondary moment I of the radially outer portion 80 defined by the slit 76A is that of the first tongue portion 48 where the slit 76A is not formed. It is smaller than the sectional moment I. For this reason, when the gas pressure acts radially outward with respect to the wall surface of the slit 76A, the radially outer portion 80 can be greatly deformed. As a result, the contact pressure between the tip corner portion 72 and the cylinder inner peripheral surface 42 is reduced.

  In some embodiments, as shown in FIG. 6, the piston ring 40 further includes a through hole 78 </ b> A that penetrates the seal wall 58 in the axial direction. The through hole 78A is integrally connected to the slit 76A, and the radial width of the end portion of the slit 76A located on one end side of the main body 44 in the circumferential direction is enlarged by the through hole 78A.

  According to this configuration, since the width of the end portion of the slit 76A is enlarged by the through hole 78A formed in the seal wall portion 58, the stress concentration in the vicinity of the peripheral end portion of the slit 76A is alleviated. For this reason, breakage of the portion with reduced rigidity is prevented while reducing the rigidity of the portion of the first tongue portion 48 including the tip corner portion 72.

  Moreover, the rigidity of the part of the 1st tongue part 48 containing the front-end | tip corner part 72 can further be reduced because the width | variety of the terminal part of the slit 76A was expanded. Alternatively, if the rigidity is the same, the length L of the slit 76A in the circumferential direction can be shortened by increasing the width of the end portion of the slit 76A. If the length of the slit 76A can be shortened, the outer diameter of the piston ring 40 increases due to wear of the cylinder inner circumferential surface 42, and the first tongue 48 and the second tongue 50 overlap each other. Even if the length of the region S3 is shortened, combustion gas leakage through the slit 76A can be reliably prevented.

  In some embodiments, as shown in FIGS. 7 to 12, the piston ring 40 has a through-hole 78 (which penetrates any one of the first tongue 48, the second tongue, and the main body 44 in the axial direction. 78B, 78C, 78D, 78E, 78F, 78G). The through hole 78 (78B, 78C, 78D, 78E, 78F, 78G) is integrally connected to the slit 76 (76B, 76C, 76D, 76E, 76F, 78G). The width has been expanded.

According to this configuration, the width of the end portion of the slit 76 (76B, 76C, 76D, 76E, 76F, 76G) is expanded by the through hole 78 (78B, 78C, 78D, 78E, 78F, 78G). The stress concentration in the vicinity of the peripheral end of the slit 76 (76B, 76C, 76D, 76E, 76F, 76G) is alleviated. For this reason, breakage of the portion with reduced rigidity is prevented while reducing the rigidity of the portion including the tip corner portion 72 of the first tongue portion 48 or the portion including the tip corner portion 74 of the second tongue portion 50.
Moreover, the width | variety of the termination | terminus part of the slit 76 (76B, 76C, 76D, 76E, 76F, 76G) is expanded, and the part including the front-end | tip corner part 72 of the 1st tongue part 48, or the front-end | tip of the 2nd tongue part 50 The rigidity of the portion including the corner portion 74 can be further reduced.

In some embodiments, with respect to the portion including the tip corner portion 72 of the first tongue 48, the Young's modulus is E, the cross-sectional second moment about the axis parallel to the axis CL is I, and the axis around the axis CL is parallel. When the moment acting on M is M, M / EI, that is, the length L in the circumferential direction and the position in the radial direction so that the curvature falls within the range of 0.00012644 or more and 0.00316097 or less. Has been determined.
Here, FIG. 17 is a graph showing the relationship between the length L of the slit 76A and M / EI. If M / EI is 0.00012644 or more and 0.00316097 or less, the radially outer portion 80 including the tip corner portion 72 of the first tongue portion 48 is easily deformed with respect to the moment, and the cylinder inner periphery in the vicinity of the tip corner portion 72 is obtained. It is possible to reliably prevent a large dent from occurring on the surface 42.

In some embodiments, the distance from the outer surface 64 of the seal wall 58 to the circumferential slit 76A in the radial direction, that is, the width h of the radial outer portion 80 is equal to the width W of the distal end surface 68 in the radial direction. 28% or less.
According to this configuration, the distance from the outer surface 64 of the seal wall 58 to the circumferential slit 76A, that is, the width h of the radially outer portion 80 is the width W in the radial direction of the first tongue portion 48 or the tip surface 68. The rigidity of the portion including the tip corner portion 72 of the first tongue portion 48 can be sufficiently reduced.
The shorter the distance from the outer surface 64 of the seal wall 58 to the circumferential slit 76A, the better. However, in consideration of workability, the distance from the outer surface 64 of the seal wall 58 to the circumferential slit 76A is For example, it is set to 2% or more of the width W in the radial direction of the first tongue 48 or the tip surface 68.

In some embodiments, the distance from the outer surface 64 of the seal wall 58 to the circumferential slit 76A in the radial direction, that is, the width h of the radial outer portion 80 is 7 mm or less.
According to this configuration, the distance from the outer surface 64 of the seal wall portion 58 to the circumferential slit 76A is 7 mm or less, and the rigidity of the portion including the tip corner portion 72 of the first tongue portion 48 can be sufficiently reduced. it can.
The shorter the distance from the outer surface 64 of the seal wall portion 58 to the circumferential slit 76A, the better. However, in consideration of workability, the distance is set to 0.5 mm or more, for example.

In some embodiments, the length L of the circumferential slit 76A in the circumferential direction is 34% or less of the initial length along the circumferential direction of the overlapping region S3.
According to this configuration, since the length L of the circumferential slit 76A in the circumferential direction is 34% or less of the initial length along the circumferential direction of the overlapping region S3, the first tongue 48 and the second The length of the slit 76A can be made sufficiently shorter than the length of the overlapping region S3 where the tongue 50 overlaps each other. For this reason, the outer diameter of the piston ring 40 is expanded due to wear of the cylinder inner peripheral surface 42, and the length of the overlapping region S3 where the first tongue 48 and the second tongue 50 overlap each other is shortened. In addition, it is possible to reliably prevent the combustion gas from leaking through the slit 76A.
In the circumferential direction, the length L of the circumferential slit 76A is set to, for example, 13% or more of the initial length along the circumferential direction of the overlapping region S3.

In some embodiments, the length L of the circumferential slit 76A in the circumferential direction is 15 mm or less.
According to this configuration, since the length L of the circumferential slit 76A in the circumferential direction is 15 mm or less, the length of the overlapping region S3 in which the first tongue portion 48 and the second tongue portion 50 overlap each other. In comparison with the above, the length of the slit 76A can be made sufficiently short. For this reason, the outer diameter of the piston ring 40 is expanded due to wear of the cylinder inner peripheral surface 42, and the length of the overlapping region S3 where the first tongue 48 and the second tongue 50 overlap each other is shortened. In addition, it is possible to reliably prevent the combustion gas from leaking through the slit 76A.
Note that the length L of the circumferential slit 76A in the circumferential direction is set to, for example, 6 mm or more.

In some embodiments, as shown in FIGS. 7 to 9, the at least one slit 76 is a radial slit 76 </ b> B formed on one end side of the main body 44 and at least one of the first tongue 48. 76C, 76D included. The radial slits 76 </ b> B, 76 </ b> C, 76 </ b> D extend along the radial direction from one end side of the main body 44 or the inner side surface in the radial direction of the first tongue portion 48.
For example, the radial slits 76 </ b> B, 76 </ b> C, and 76 </ b> D penetrate the one end side of the main body portion 44 or the inner peripheral wall portion 56 of the first tongue portion 48 in the axial direction, and the one end side of the main body portion 44 or the inside of the first tongue portion 48. Openings are made on both sides in the axial direction of the peripheral wall portion 56. The radial slits 76 </ b> B, 76 </ b> C, 76 </ b> D are opened on the inner side surface (inner peripheral surface) of the main body 44 or the inner side surface (inner peripheral surface) of the inner peripheral wall portion 56 of the first tongue portion 48.
According to this configuration, the first corner portion 72 including the tip corner portion 72 can be easily configured by the radial slits 76B, 76C, and 76D formed on at least one of the one end side of the main body portion 44 and the first tongue portion 48. The rigidity of the tongue portion 48 is reliably reduced.
The one end side of the main body 44 refers to a range within 45 degrees from the one end surface 52 of the main body 44 in the initial state in which the piston ring 40 is disposed in the cylinder liner 15.

  In some embodiments, as shown in FIG. 9, by providing a plurality of slits 76 (76C, 76D) in parallel, the rigidity can be reliably reduced even if the length of each slit 76 is short. .

In some embodiments, as shown in FIG. 10, the at least one slit 76 includes a second circumferential slit 76 </ b> E formed in the second tongue 50. The second circumferential slit 76E extends along the circumferential direction from the tip of the second tongue 50 in the circumferential direction, and divides the tip side of the second tongue 50 into two regions adjacent in the radial direction. Yes.
According to this configuration, the rigidity of the portion of the second tongue portion 50 including the tip corner portion 74 is reliably reduced with a simple configuration by the second circumferential slit 76E formed in the second tongue portion 50. The

In some embodiments, as shown in FIGS. 11 and 12, at least one slit 76 has a second diameter formed on at least one of the other end side of the main body portion 44 and the second tongue portion 50. Direction slits 76F and 76G are included. The second radial slits 76 </ b> F and 76 </ b> G extend along the radial direction from the other end side of the main body 44 or the inner side surface in the radial direction of the second tongue portion 50.
For example, the second radial slits 76F and 76G penetrate the other end side of the main body portion 44 or the second tongue portion 50 in the axial direction, and the other end side of the main body portion 44 or both axial direction sides of the second tongue portion 50. Open at. The second radial slits 76 </ b> F and 76 </ b> G are opened on the inner surface (inner peripheral surface) of the main body 44 or the inner surface (inner peripheral surface) of the second tongue 50.

According to this configuration, the distal end corner portion 74 is included with a simple configuration by the second radial slits 76F and 76G formed on at least one of the other end side of the main body portion 44 and the second tongue portion 50. The rigidity of the second tongue portion 50 is reliably reduced.
The other end side of the main body 44 refers to a range within 45 degrees from the other end surface 54 of the main body 44 in the initial state in which the piston ring 40 is disposed in the cylinder liner 15. .

The present invention is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.
For example, the number of slits 76 is not limited to one, and a circumferential slit, a second circumferential slit, a radial slit, and a second radial slit may be used in appropriate combination.
The circumferential slit may extend obliquely with respect to the circumferential direction, and the radial slit may extend obliquely with respect to the radial direction.
The piston ring 40 is suitable for a top ring disposed closest to the combustion chamber 19 when a plurality of piston rings are attached to the piston 16, but is applicable to other than the top ring.
Further, the engine 1 to which the piston ring 40 is applied is preferably a marine two-cycle large diesel engine, but may be another engine.

DESCRIPTION OF SYMBOLS 1 Engine 2 Base plate 3 Frame 4 Cylinder jacket 5 Tie bolt 6 Oil pan 8 Crank shaft 9 Journal part 10 Crank pin 11 Connecting rod 12 Crosshead 13 Piston rod 14 Sliding plate 15 Cylinder 16 Piston 17 Cylinder cover 18 Cover bolt 19 Combustion chamber 20 Exhaust port 21 Exhaust valve 22 Fuel injection valve 23 Scavenging port 24 Scavenging chamber 25 Gland packing 26 Turbocharger 27 Compressor 28 Turbine 29 Air conduit 30 Scavenging trunk chamber 31 Water cooler 32 Drop separator 33 Backflow prevention door 34 Exhaust static pressure tube 40 Piston ring 41 Piston ring groove 42 Cylinder inner peripheral surface 44 Main body portion 46 Joint portion 48 First tongue portion 50 Second tongue portion 52 One end surface 54 Other end surface 56 Inner peripheral wall portion 58 Seal wall portion 60 Fitting recess 64 Outer side surface (outer periphery) surface)
66 Outside surface (outer peripheral surface)
68 Tip surface 70 Tip surface 72 Tip corner portion 74 Tip corner portion 76 Slit 78 Through hole 80 Radial outer portion 82 Radial inner portion CL Axes S1, S2 Non-overlapping region S3 Overlapping region

Claims (7)

A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in the first tongue ,
The first tongue portion has a tip corner portion located outside in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of the portion including the tip corner portion of the first tongue with respect to a moment around an axis parallel to the axis ,
The first tongue portion is located on the inner side in the radial direction and has an inner peripheral wall portion having a portion facing the second tongue portion, and protrudes radially outward from the inner peripheral wall portion, and the second tongue portion, A seal wall portion facing in the axial direction,
The at least one slit includes a circumferential slit formed in the seal wall,
The circumferential slit extends along the circumferential direction from the distal end of the seal wall portion in the circumferential direction, and divides the distal end side of the seal wall portion into two regions adjacent in the radial direction. ,
Regarding the portion including the tip corner portion of the first tongue, the Young's modulus is E, the cross-sectional secondary moment about the axis parallel to the axis is I, and the moment acting around the axis parallel to the axis is M. Sometimes, the circumferential length and the radial position of the circumferential slit are determined so that M / EI falls within the range of 0.00012644 or more and 0.00316097 or less. Piston ring characterized by that. A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in the first tongue ,
The first tongue portion has a tip corner portion located outside in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of the portion including the tip corner portion of the first tongue with respect to a moment around an axis parallel to the axis ,
The first tongue portion is located on the inner side in the radial direction and has an inner peripheral wall portion having a portion facing the second tongue portion, and protrudes radially outward from the inner peripheral wall portion, and the second tongue portion, A seal wall portion facing in the axial direction,
The at least one slit includes a circumferential slit formed in the seal wall,
The circumferential slit extends along the circumferential direction from the distal end of the seal wall portion in the circumferential direction, and divides the distal end side of the seal wall portion into two regions adjacent in the radial direction. ,
A piston ring, wherein a distance from an outer surface of the seal wall portion to the circumferential slit in the radial direction is 7 mm or less . A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in the first tongue ,
The first tongue portion has a tip corner portion located outside in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of the portion including the tip corner portion of the first tongue with respect to a moment around an axis parallel to the axis ,
The first tongue portion is located on the inner side in the radial direction and has an inner peripheral wall portion having a portion facing the second tongue portion, and protrudes radially outward from the inner peripheral wall portion, and the second tongue portion, A seal wall portion facing in the axial direction,
The at least one slit includes a circumferential slit formed in the seal wall,
The circumferential slit extends along the circumferential direction from the distal end of the seal wall portion in the circumferential direction, and divides the distal end side of the seal wall portion into two regions adjacent in the radial direction. ,
The piston ring, wherein the circumferential slit has a length of 15 mm or less in the circumferential direction . A through hole penetrating the seal wall portion in the axial direction;
The piston ring according to any one of claims 1 to 3, wherein a width of a terminal portion of the slit located on the main body side in the circumferential direction is enlarged by the through hole. A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in at least one of the first tongue and the main body,
The first tongue portion has a tip corner portion located outside in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of the portion including the tip corner portion of the first tongue with respect to a moment around an axis parallel to the axis ,
The at least one slit includes a radial slit formed on at least one of the one end side in the circumferential direction of the main body and the first tongue,
The radial slit extends from the one end portion side in the circumferential direction of the main body portion or the radial inner side of the first tongue portion along the radial outer side. piston ring. A main body extending along a circumferential direction around the axial direction;
A fitting recess extending from the one end portion to the other end portion at one end portion in the circumferential direction of the main body portion and extending along the circumferential direction to one side in the axial direction on the radially outer side of the main body portion. A first tongue formed with;
A second tongue that extends from the other end portion to the one end portion at the other end portion in the circumferential direction of the main body portion and forms an abutment portion together with the first tongue portion by fitting into the fitting recess. And
And at least one slit formed in at least one of the second tongue and the main body,
The second tongue portion has a tip corner portion located on the outer side in the radial direction and located on the tip side in the circumferential direction,
The slit reduces the rigidity of a portion including the tip corner portion of the second tongue portion with respect to a moment around an axis parallel to the axis ,
The at least one slit includes a second radial slit formed in at least one of the other end side and the second tongue portion of the main body portion,
The second radial slit extends from the inner surface of the other end side of the main body portion or the second tongue portion in the radial direction along the radial direction. Piston ring to do. A cylinder,
A piston capable of reciprocating in the cylinder and forming a combustion chamber in the cylinder;
An engine comprising the piston ring according to any one of claims 1 to 6 , which is attached to the piston.

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