Cylinder liner and marine internal combustion engine

Abstract

To suppress an outflow of a lubricant from a scavenging port.SOLUTION: A cylinder liner 14 is equipped with a plurality of scavenging ports 14a, and a plurality of oil holding grooves 14c that is provided on an inner wall portion 14b on the upper side of the plurality of scavenging ports 14a, and is disposed while aligning in a circumferential direction so as to correspond to the scavenging ports 14a. The plurality of scavenging ports 14a circulates air sucked from a cylinder jacket 13 so as to swirl in a predetermined rotating direction D1 that is either one direction in the circumferential direction. The plurality of oil holding grooves 14c is provided while the adjacent oil holding grooves 14c are parted from each other, and extends in the rotating direction D1 as it goes upward along a center axis C so as to linearly extend along the circulation of swirls.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a cylinder liner and a marine internal combustion engine including the cylinder liner. [Background technology]

[0002] For example, Patent Document 1 discloses a cylinder liner with grooves for oil retention. Specifically, the cylinder liner disclosed in Patent Document 1 has wavy grooves for oil retention below the oil feed hole and above the scavenging port (scavenging hole) on the inner surface of the cylinder liner.

[0003] According to the above-mentioned Patent Document 1, the lubricating oil supplied to the inner surface of the cylinder liner through the oil feed hole is scraped downward by the reciprocating movement of the piston. This lubricating oil is stored in the groove without leaking to the outside through the scavenging port. The lubricating oil stored in the groove is then scraped upward by the piston and is also diffused in the circumferential direction along the groove. This makes it possible to reduce the amount of lubricating oil that leaks to the outside through the scavenging port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 61-5346 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the oil retention groove (oil retention groove) is configured to be filled with lubricating oil as in Patent Document 1, the lubricating oil in the groove must be scraped out and replaced, for example, for each cycle, which is inconvenient in terms of preventing the leakage of the lubricating oil.

[0006] The technology disclosed herein has been made in consideration of the above-mentioned points, and has an object to suppress the outflow of lubricating oil from the scavenging port. [Means for solving the problem]

[0007] In devising the configuration of the oil retaining groove, the inventors of the present application focused on the horizontal vortex-like air flow (swirl flow) that flows inside the cylinder liner, and arrived at the present disclosure.

[0008] Specifically, a first aspect of the present disclosure relates to a cylindrical cylinder liner configured to suck air from a cylinder jacket as a piston reciprocates, the cylinder liner including a plurality of scavenging ports arranged side by side along a circumferential direction, and a plurality of oil grooves provided in an inner wall portion above the plurality of scavenging ports and arranged side by side along a circumferential direction so as to correspond to each of the plurality of scavenging ports.

[0009] According to the first aspect, each of the plurality of scavenging ports, when viewed in a cross section perpendicular to the central axis of the piston, causes the air sucked from the cylinder jacket to flow in a swirling manner in a predetermined rotational direction, which is one of the circumferential directions, and the plurality of oil retention grooves are arranged in a state in which adjacent oil retention grooves are separated from each other, and each extends in the rotational direction as it moves upward along the central axis so as to extend linearly along the vortex flow.

[0010] According to the first aspect, each oil groove is formed to extend in an oblique direction that is a combination of an upward direction and a rotational direction so as to extend along the flow of the vortex. By forming the oil groove in this manner, it is possible to promote the scraping out of the lubricating oil from the oil groove by the swirl flow. Since the swirl flow occurs for each cycle, it is possible to replace the lubricating oil in conjunction with the progression of the cycle.

[0011] Furthermore, by intentionally separating the oil retention grooves without connecting them to each other, it becomes possible to effectively scrape out the lubricating oil upwards without guiding the lubricating oil from one oil retention groove to the other oil retention groove adjacent to it.

[0012] By promoting the scraping out of the oil groove, it is possible to keep the oil groove empty when the oil groove is to be activated, such as when the oil is scraped downward from the inner wall of the cylinder liner, thereby preventing the oil from leaking out.

[0013] A second aspect of the present disclosure relates to a cylindrical cylinder liner configured to suck air from a cylinder jacket as a piston reciprocates, the cylinder liner including a plurality of scavenging ports arranged in a line along a circumferential direction, and a plurality of oil grooves provided above the plurality of scavenging ports and arranged in a line along a circumferential direction corresponding to each of the plurality of scavenging ports.

[0014] According to the second aspect, when viewed in a cross section perpendicular to the central axis of the piston, each of the plurality of scavenging ports causes the air sucked from the cylinder jacket to flow in a swirling manner in a predetermined rotational direction, which is one of the circumferential directions, and each of the plurality of oil retention grooves extends in the rotational direction as it heads upward along the central axis so as to extend linearly along the flow of the vortex, and further includes a plurality of second oil retention grooves that extend in the rotational direction or in the opposite direction to the rotational direction as they head upward along the central axis so as to connect adjacent oil retention grooves among the plurality of oil retention grooves, and the inclination of the second oil retention grooves with respect to the central axis is steeper than the inclination of the oil retention grooves.

[0015] According to the second aspect, each oil groove is formed to extend in an oblique direction obtained by combining an upward direction and a rotation direction or an opposite direction so as to extend along the flow of the vortex. By forming the oil groove in this manner, it becomes possible to promote the scraping out of the lubricating oil from the oil groove by the swirl flow. Since the swirl flow occurs for each cycle, it becomes possible to replace the lubricating oil in conjunction with the progress of the cycle.

[0016] Furthermore, when connecting oil retention grooves to each other, by connecting them via a second oil retention groove that is steeper than the first oil retention groove, the dimension of the oil retention groove in the circumferential direction and therefore the dimension of the oil retention groove in the oblique direction can be relatively long. By relatively longing the dimension of the oil retention groove for scooping out the lubricating oil by the swirl flow, between the oil retention groove and the second oil retention groove, it is advantageous in promoting the scooping out of the lubricating oil.

[0017] By promoting the scraping out of the oil groove, it is possible to keep the oil groove empty when the oil groove is to be activated, such as when the oil is scraped downward from the inner wall of the cylinder liner, thereby preventing the oil from leaking out.

[0018] According to a third aspect of the present disclosure, each lower end portion of the plurality of oil retaining grooves may be disposed between adjacent ones of the plurality of scavenging ports in a circumferential direction.

[0019] According to the third aspect, when the lubricating oil flows down from the lower end of each oil retaining groove, the lubricating oil can be guided between the scavenging ports, which is advantageous in suppressing the outflow of the lubricating oil from the scavenging ports.

[0020] According to a fourth aspect of the present disclosure, each lower end portion of the plurality of oil retaining grooves may be disposed at a middle position between the adjacent scavenging ports in a circumferential direction.

[0021] According to the fourth aspect, it is advantageous in suppressing outflow of lubricating oil from the scavenging port.

[0022] According to a fifth aspect of the present disclosure, upper ends of the plurality of oil retaining grooves may be disposed between the adjacent scavenging ports in the circumferential direction.

[0023] According to the fifth aspect, when the lubricating oil scooped out from the upper end of each oil retaining groove flows downward, the lubricating oil can be guided between the scavenging ports, which is advantageous in suppressing the outflow of the lubricating oil from the scavenging ports.

[0024] Furthermore, according to a sixth aspect of the present disclosure, the upper end portion of the oil retention groove located upstream in the rotational direction and the lower end portion of the oil retention groove located downstream in the rotational direction are arranged to be aligned along the axial direction.

[0025] According to the sixth aspect, when the lubricating oil scooped out from the oil retention groove located on the upstream side flows downward, the lubricating oil can be received by the oil retention groove located on the downstream side, which is advantageous in suppressing the outflow of the lubricating oil from the scavenging port.

[0026] According to a seventh aspect of the present disclosure, an axial dimension of each of the plurality of oil retention grooves may be longer than a circumferential dimension of the oil retention groove.

[0027] According to the seventh aspect, it is advantageous to configure the swirl flow and each oil retaining groove as parallel as possible.

[0028] Furthermore, according to an eighth aspect of the present disclosure, each of the plurality of oil retention grooves, when viewed in a longitudinal section along an inclination direction relative to the central axis, may have a depth of at least the upper half in the inclination direction that gradually becomes shallower going upward.

[0029] According to the eighth aspect, it is advantageous for the lubricating oil to be scooped out from the oil retaining groove by the swirl flow.

[0030] A ninth aspect of the present disclosure relates to a marine internal combustion engine including the cylinder liner. Effect of the Invention

[0031] As described above, according to the present disclosure, it is possible to suppress the outflow of lubricating oil from the scavenging port. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a marine internal combustion engine. [Diagram 2] FIG. 2 is a vertical cross-sectional view illustrating the structure of a cylinder liner. [Diagram 3] FIG. 3 is a cross-sectional view illustrating the structure of a cylinder liner. [Figure 4] FIG. 4 is a schematic view illustrating an oil-retaining groove in the first embodiment. [Diagram 5] FIG. 5 is a vertical cross-sectional view illustrating the structure of the oil-retaining groove. [Figure 6] FIG. 6 is a view corresponding to FIG. 4 illustrating the second embodiment. [Figure 7] FIG. 7 is a view corresponding to FIG. 4 and showing a modified example of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description is an example. Fig. 1 is a schematic diagram illustrating the configuration of a marine internal combustion engine (hereinafter, also simply referred to as "engine 1").

[0034] In this specification, as embodiments of the engine 1, a first embodiment having a cylinder liner 14 with special technical features and a second embodiment having cylinder liners 114, 214 with corresponding special technical features will be described in order.

[0035] First embodiment The engine 1 according to the first embodiment is an in-line multi-cylinder diesel engine having a plurality of cylinders 16. This engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine, and is installed on large ships such as tankers, container ships, and car carriers.

[0036] The engine 1 installed on a ship is used as a main engine for propelling the ship. To this end, the output shaft of the engine 1 is connected to a propeller (not shown) of the ship via a propeller shaft (not shown). When the engine 1 is operated, its output is transmitted to the propeller, propelling the ship.

[0037] In particular, the engine 1 according to the present disclosure is configured as a so-called crosshead type internal combustion engine in order to realize a long stroke. That is, in this engine 1, a piston rod 22 that supports a piston 21 from below and a connecting rod 24 that is connected to a crankshaft 23 are connected by a crosshead 25.

[0038] (1)Main configuration The main parts of the engine 1 will be described below.

[0039] As shown in Fig. 1, the engine 1 includes a base plate 11 located below, a frame 12 provided on the base plate 11, and a cylinder jacket 13 provided on the frame 12. The base plate 11, the frame 12, and the cylinder jacket 13 are fastened together by a plurality of tie bolts and nuts extending in the vertical direction. The engine 1 also includes a cylinder 16 provided in the cylinder jacket 13, a piston 21 provided in the cylinder 16, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating movement of the piston 21.

[0040] The base plate 11 constitutes the crankcase of the engine 1, and houses a crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of a connecting rod 24 is connected to the crankshaft 23 via a crank 27.

[0041] The frame 12 houses a pair of guide plates 28, the connecting rod 24, and a crosshead 25. Of these, the pair of guide plates 28 are made of a pair of plate-shaped members provided along the piston axial direction, and are arranged at an interval in the width direction of the engine 1 (the left-right direction on the paper surface of FIG. 1). The connecting rod 24 is arranged between the pair of guide plates 28 with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via the crosshead 25.

[0042] Specifically, the crosshead 25 is disposed between a pair of guide plates 28, and slides up and down along each of the guide plates 28. That is, the pair of guide plates 28 are configured to guide the sliding of the crosshead 25. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 so as to move up and down integrally therewith, and is connected to the connecting rod 24 so as to rotate the connecting rod 24 about the upper end of the connecting rod 24 as a fulcrum.

[0043] The cylinder jacket 13 supports a cylinder liner 14 as an inner cylinder. The cylinder liner 14 is formed in a cylindrical shape and is inserted into the cylinder jacket 13. The internal space of the cylinder jacket 13 communicates with the internal space of the cylinder liner 14. The above-mentioned piston 21 is disposed inside the cylinder liner 14. This piston 21 reciprocates up and down along the inner wall of the cylinder liner 14. In addition, a cylinder cover 15 is fixed to the top of the cylinder liner 14. The cylinder cover 15, together with the cylinder liner 14, constitutes a cylinder 16.

[0044] In addition, the cylinder cover 15 is provided with an exhaust valve 18 that is operated by a valve train (not shown). The exhaust valve 18, together with a cylinder 16 formed by the cylinder liner 14 and the cylinder cover 15, and the top surface of a piston 21, defines a combustion chamber 17. The exhaust valve 18 opens and closes between the combustion chamber 17 and an exhaust pipe 19. The exhaust pipe 19 has an exhaust port that communicates with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

[0045] Further, the cylinder cover 15 is provided with a fuel injection valve 31 for supplying fuel to the combustion chamber 17. The fuel injection valve 31 injects diesel fuel into the combustion chamber 17.

[0046] Furthermore, the engine 1 according to this embodiment is provided with a fuel pump 32 that pressure-feeds diesel fuel to the fuel injection valve 31. As shown in Fig. 1, the fuel pump 32 is laid out in the vicinity of the cylinder 16, and is fluidly connected to the fuel injection valve 31 via a fuel injection pipe (not shown).

[0047] An exhaust manifold 41 is also disposed near the cylinder 16. This exhaust manifold 41 is connected to the combustion chamber 17 via the exhaust pipe 19. The exhaust manifold 41 receives exhaust gas from the combustion chamber 17 through the exhaust pipe 19, temporarily stores the received exhaust gas, and converts the dynamic pressure of the exhaust gas into static pressure.

[0048] The engine 1 further includes a turbocharger 42 that supercharges a combustion gas such as air, and a scavenging trunk 43 that temporarily stores the combustion gas compressed by the turbocharger 42. The turbocharger 42 rotates a compressor (not shown) together with a turbine (not shown) by utilizing the pressure of the exhaust gas, and the combustion gas is compressed by the compressor. The scavenging trunk 43 is provided so as to communicate with the internal space of the cylinder jacket 13. The combustion gas compressed by the turbocharger 42 (hereinafter also referred to as "compressed gas") flows from the scavenging trunk 43 into the internal space of the cylinder jacket 13, and is fed from the internal space to the internal space of the cylinder liner 14 (the space surrounded by the inner wall portion 14b of the cylinder liner 14) through the scavenging port 14a.

[0049] When the engine 1 is in operation, diesel fuel is supplied into the combustion chamber 17 from the fuel injection valve 31, and compressed gas is supplied from the scavenging trunk 43 through the cylinder jacket 13, etc. As a result, in the combustion chamber 17, the diesel fuel is combusted by the compressed gas.

[0050] The energy generated by the diesel fuel causes the piston 21 to reciprocate up and down along the cylinder liner 14. At this time, when the exhaust valve 18 operates to open the combustion chamber 17, exhaust gas generated by combustion is pushed out into the exhaust pipe 19. In addition, as the piston 21 reciprocates along the cylinder liner 14, compressed gas (air) is sucked from the cylinder jacket 13 into the cylinder liner 14, and the piston 21 pushes this in, introducing new compressed gas into the combustion chamber 17. By repeating these processes, the combustion of diesel fuel and scavenging of the cylinder 16 are repeatedly performed.

[0051] Furthermore, when the piston 21 reciprocates due to combustion, the piston rod 22 reciprocates up and down together with the piston 21. This causes the crosshead 25 connected to the piston rod 22 to reciprocate up and down. This crosshead 25 allows the connecting rod 24 to rotate, and rotates the connecting rod 24 around the connection point with the crosshead 25 as a fulcrum. Then, the crank 27 connected to the lower end of the connecting rod 24 performs crank motion, and the crankshaft 23 rotates in response to this crank motion. In this way, the crankshaft 23 converts the reciprocating movement of the piston 21 into rotational motion, and rotates the propeller of the ship together with the propeller shaft. This propels the ship.

[0052] Incidentally, lubricating oil is supplied to the inner wall portion 14b of the cylinder liner 14 through one or more oil holes (not shown) in order to lubricate the inner wall portion 14b and the piston 21. However, when the piston 21 descends, the lubricating oil is scraped downward, and as a result, there is a possibility that the lubricating oil will flow out through the scavenging port 14a described below.

[0053] Therefore, in this embodiment, the inner wall portion 14b of the cylinder liner 14 is provided with a plurality of oil grooves 14c for preventing the outflow of lubricating oil and ensuring lubrication for the reciprocating movement of the piston 21.

[0054] Among the configurations of the cylinder liner 14, the configurations related to the oil grooves 14c will be described in detail below.

[0055] (2) Cylinder liner configuration Fig. 2 is a vertical cross-sectional view illustrating the structure of the cylinder liner 14. Fig. 3 is a horizontal cross-sectional view illustrating the structure of the cylinder liner 14. Fig. 4 is a schematic diagram illustrating the inner wall portion 14b of the cylinder liner 14. Fig. 5 is a vertical cross-sectional view illustrating the structure of the oil groove 14c. Here, Fig. 3 corresponds to the III-III cross section in Fig. 2, and Fig. 5 corresponds to the VV cross section in Fig. 4.

[0056] In the following description, the direction along the central axis C of the cylinder liner 14 and the piston 21 illustrated in Fig. 2 is defined as the "axial direction," and the direction extending radially from this central axis C is defined as the "radial direction." Additionally, the clockwise and counterclockwise directions around this central axis C are defined as the "circumferential direction."

[0057] The axial direction is equal to the moving direction of the piston 21 described above, and can also be referred to as the "upward / downward direction." In addition, the direction along the axial direction from a scavenging port 14a to a combustion chamber 17 described below may be referred to as the "upward direction," and the opposite direction may be referred to as the "downward direction."

[0058] The radial direction is perpendicular to the moving direction of the piston 21. In addition, one side closer to the central axis C in the radial direction may be referred to as the "inner side," and the other side farther away from the central axis C may be referred to as the "outer side."

[0059] The cylinder liner 14 functions as an inner cylinder that guides the reciprocating movement of the piston 21. Specifically, as shown in Fig. 2, the cylinder liner 14 is formed in a cylindrical shape that extends in the up-down direction.

[0060] As shown in Figs. 2 and 3, the cylinder liner 14 has a plurality of scavenging ports 14a provided in the lower part of the cylinder liner 14, an inner wall portion 14b that defines the internal space of the cylinder liner 14, and a plurality of oil retaining grooves 14c provided in the inner wall portion 14b.

[0061] Among these, the multiple scavenging ports 14a are arranged in a line along the circumferential direction. Each scavenging port 14a is formed as a scavenging hole penetrating the inner wall portion 14b of the cylinder liner 14.

[0062] In addition, in the vertical direction, each scavenging port 14a is disposed in a portion of the cylinder liner 14 that is inserted into the cylinder jacket 13 (a portion corresponding to a lower portion of the cylinder liner 14). Although not shown in the figure, each scavenging port 14a is disposed so as to be located above the piston 21 that is located at the bottom dead center.

[0063] 3, each of the scavenging ports 14a causes the air sucked from the cylinder jacket 13 to flow in a swirling manner in a predetermined rotational direction D1, which is one of the circumferential directions, when viewed in a cross section perpendicular to the central axis C. In the illustrated example, the rotational direction D1 is equal to the clockwise direction about the central axis C. To achieve such a flow, each scavenging port 14a is inclined so as to move in a clockwise direction in the circumferential direction from the outer side to the inner side in the radial direction.

[0064] The rotation direction D1 is not limited to the clockwise direction as shown in the figure. The rotation direction D1 may be a counterclockwise direction around the central axis C. In this case, the inclination direction of each scavenging port 14a will be inclined toward the counterclockwise direction in the circumferential direction as it moves from the outside to the inside in the radial direction (the inclination will be inclined toward the opposite direction to the example).

[0065] Each scavenging port 14 a is opened when the piston 21 is located near the bottom dead center, and communicates the scavenging trunk 43 with the combustion chamber 17 via the cylinder jacket 13 and the cylinder liner 14 .

[0066] When each scavenging port 14a is opened, the air sucked into the cylinder liner 14 flows in a swirling manner in the rotational direction D1 as shown by the arrow A1 in Fig. 3. The swirling air becomes a swirl flow around the central axis C as shown by the arrow A in Fig. 2 and flows toward the combustion chamber 17.

[0067] The inner wall portion 14b guides the reciprocating movement of the piston 21. Specifically, as shown in Fig. 2, the inner wall portion 14b according to this embodiment is formed in a cylindrical shape having a central axis coaxial with the central axis C of the piston 21 and extending in the up-down direction.

[0068] Here, among the inner wall portions 14b extending in the vertical direction, the inner wall portion 14b located above the plurality of scavenging ports 14a has a plurality of oil retaining grooves 14c arranged side by side in the circumferential direction so as to correspond to each of the scavenging ports 14a.

[0069] Specifically, the oil grooves 14c are formed in the same number as the scavenging ports 14a. Each oil groove 14c is disposed above the corresponding scavenging port 14a.

[0070] Furthermore, the multiple oil retention grooves 14c in the first embodiment are arranged in a state in which adjacent oil retention grooves 14c are separated from each other, and each extends in the rotational direction D1 as it moves upward along the central axis C so as to extend along the vortex flow.

[0071] Specifically, the oil grooves 14c are formed so that adjacent oil grooves 14c are not connected to each other, as shown in Fig. 4. Each oil groove 14c extends in the circumferential direction in the rotation direction D1 described above (in other words, in a diagonal direction combining the upward direction and the rotation direction D1) as it moves upward in the vertical direction so as to extend along the swirl flow. Each oil groove 14c extends straight along this diagonal direction.

[0072] Further, each lower end 142 of the plurality of oil retaining grooves 14c is disposed between adjacent scavenging ports 14a (specifically, at the middle position between adjacent scavenging ports 14a) in the circumferential direction. That is, as shown by the dashed line extending in the vertical direction of the paper in FIG. 4, a straight line extending from each lower end 142 along the axial direction does not intersect with the opening of each scavenging port 14a.

[0073] Similarly, each upper end 141 of the multiple oil retaining grooves 14c is disposed between adjacent scavenging ports 14a (specifically, at the middle position between adjacent scavenging ports 14a) in the circumferential direction. That is, as shown by the dashed line extending in the vertical direction of the paper in Fig. 4, a straight line extending from each upper end 141 along the axial direction does not intersect with the opening of each scavenging port 14a.

[0074] By disposing both the lower end 142 and the upper end 141 of each oil retention groove 14c between the adjacent scavenging ports 14a, the dimension W1 of each oil retention groove 14c in the circumferential direction is longer than the dimension W2 of each scavenging port 14a in the same direction.

[0075] Also, as shown in Figure 4, of adjacent oil retention grooves 14c, the upper end 141 of the oil retention groove 14c located on the upstream side in the rotational direction D1 (right side of the paper in Figure 4) and the lower end 142 of the oil retention groove 14c located on the downstream side in the rotational direction D1 (left side of the paper in Figure 4) are arranged to be aligned along the axial direction.

[0076] As shown in Fig. 4, the dimension H1 in the axial direction of each of the oil retention grooves 14c is longer than the dimension W1 in the circumferential direction of the oil retention groove 14c. As a result of this configuration, the inclination angle θ of each oil retention groove 14c is an acute angle. Furthermore, the dimension H1 in the axial direction of each oil retention groove 14c is longer than the distance H2 between the oil retention groove 14c and the scavenging port 14a in the axial direction. Specifically, the inclination angle θ is preferably within a range of 10° to 45°.

[0077] Also, as shown in Fig. 5, when each of the oil grooves 14c is viewed in a vertical section (vertical section shown in Fig. 5) along a direction inclined to the central axis C (specifically, a diagonal direction obtained by combining the upward direction and the rotation direction D1), the depth of the upper half in the direction of inclination gradually becomes shallower toward the top. Specifically, the depth of each oil groove 14c is maximum at a portion located below the midpoint between the lower end 142 and the upper end 141 (portion b located above the lower end 142 by dimension H4), and then gradually becomes shallower from that portion toward the upper end 141. The dimension H3 of the portion that gradually becomes shallower in this way is configured to be longer than the aforementioned dimension H4.

[0078] (3) Engine lubrication performance As described above, according to the first embodiment, each oil groove 14c is formed to extend in a diagonal direction obtained by combining the upward direction and the rotation direction D1 so as to extend linearly along the vortex flow (the flow direction of the swirl flow). By forming the oil grooves in this manner, it becomes possible to scrape out the lubricating oil from the oil grooves 14c by the swirl flow. Since the swirl flow occurs for each cycle, it becomes possible to replace the lubricating oil in conjunction with the progress of the cycle.

[0079] Furthermore, as shown in FIG. 4, by intentionally separating the oil retention grooves 14c without connecting them to each other, it becomes possible to effectively scrape out the lubricating oil upward from one oil retention groove 14c without guiding the lubricating oil from the other oil retention groove 14c adjacent to it.

[0080] By promoting the scraping out of the oil groove 14c, it is possible to keep the oil groove 14c empty when the oil groove 14c should be functioning, such as when the lubricating oil is scraped downward from the inner wall portion 14b of the cylinder liner 14. This makes it possible to suppress the outflow of the lubricating oil.

[0081] 4, by disposing the lower end 142 of each oil retaining groove 14c between adjacent scavenging ports 14a in the circumferential direction (particularly, at the middle position of the scavenging ports 14a), when the lubricating oil flows down from each lower end 142, the lubricating oil can be guided between the scavenging ports 14a. This is advantageous in suppressing the outflow of the lubricating oil from the scavenging ports 14a.

[0082] 4, by disposing each upper end 141 of each oil retaining groove 14c between adjacent scavenging ports 14a in the circumferential direction (particularly, at the middle position of the scavenging ports 14a), when the lubricating oil scooped out from each upper end 141 flows downward, the lubricating oil can be guided between the scavenging ports 14a. This is advantageous in suppressing the outflow of the lubricating oil from the scavenging ports 14a.

[0083] 4, by arranging the upper end 141 of the oil retention groove 14c located on the upstream side (right side of the drawing) in the rotation direction D1 and the lower end 142 of the oil retention groove 14c located on the downstream side (left side of the drawing) in the rotation direction D1 in line along the axial direction, when the lubricating oil scooped out from the oil retention groove 14c located on the upstream side flows downward, the lubricating oil can be received by the oil retention groove 14c located on the downstream side. This is advantageous in suppressing the outflow of the lubricating oil from the scavenging port 14a.

[0084] Furthermore, as shown in FIG. 4, by making the axial dimension H1 of each oil retention groove 14c longer than the circumferential dimension W1 of the oil retention groove 14c, the inclination angle θ is made acute, which is advantageous in configuring the swirl flow and each oil retention groove 14c as parallel as possible.

[0085] Furthermore, as shown in FIG. 5, by configuring each oil retaining groove 14c so that it becomes gradually shallower toward the top, it becomes advantageous for the lubricating oil to be scooped out of the oil retaining groove 14c by the swirl flow.

[0086] Second Embodiment Next, a second embodiment of the engine 1 will be described.

[0087] (1) Oil groove according to the second embodiment Fig. 6 is a view corresponding to Fig. 4 illustrating a second embodiment. The engine 1 and the cylinder liner 114 according to the second embodiment are configured similarly to the first embodiment except for the oil groove. Therefore, in the following description, only the configuration related to the oil groove will be described.

[0088] Similar to the first embodiment, the multiple oil-retaining grooves 114c according to the second embodiment extend in the rotational direction D1 as they move upward along the central axis C so as to extend along the vortex flow.

[0089] Specifically, the oil grooves 114c extend in the circumferential direction in the rotation direction D1 described above (in other words, in a diagonal direction obtained by combining the upward direction and the rotation direction D1) so as to extend along the swirl flow. Each oil groove 114c extends straight along this diagonal direction.

[0090] Furthermore, the cylinder liner 114 of the second embodiment further includes a plurality of second oil retention grooves 114d extending in the opposite direction to the rotational direction D1 as they extend upward along the central axis C so as to connect adjacent oil retention grooves 114c among the plurality of oil retention grooves 114c.

[0091] That is, in the second embodiment, the oil retention grooves 114c adjacent to each other in the circumferential direction are connected via the second oil retention groove 114d. The second oil retention groove 114d extends linearly to connect the upper end 1141 of the oil retention groove 114c located on the upstream side (right side of the paper) in the rotation direction D1 to the lower end 1142 of the oil retention groove 114c located on the downstream side (left side of the paper) in the rotation direction D1. Each second oil retention groove 114d extends straight along a second oblique direction (in other words, an oblique direction obtained by combining an upward direction and a direction opposite to the rotation direction D1) that is oriented in the circumferential direction.

[0092] The second oil-retaining groove 114d has a slope (second slope angle) θ2 that is steeper than the slope (first slope angle) θ1 of the oil-retaining groove 114c with respect to the central axis C. Specifically, the first slope angle θ1 is preferably within a range of 10° to 45°.

[0093] Note that the first inclination angle θ1 here refers to one of the acute angles formed by an extension line extending obliquely from oil retaining groove 114c and a straight line extending along the axial direction (central axis C).

[0094] Similarly, the second inclination angle θ2 refers to the acute angle between an extension line extending from the second oil groove 114d along the second diagonal direction and a straight line extending along the axial direction (central axis C).

[0095] Specifically, in the second embodiment, the dimension of oil retention groove 114c in the axial direction is substantially equal to the dimension of second oil retention groove 114d, while the dimension of oil retention groove 114c in the circumferential direction is longer than the dimension of second oil retention groove 114d (the dimension of second oil retention groove 114d is shorter than the dimension of oil retention groove 114c).

[0096] Similarly to the first embodiment, each lower end 1142 of the oil retaining grooves 114c is disposed between adjacent scavenging ports 114a (specifically, at the middle position between adjacent scavenging ports 114a) in the circumferential direction. That is, a straight line extending from each lower end 1142 along the axial direction does not intersect with the opening of each scavenging port 114a.

[0097] Similarly to the first embodiment, the axial dimension of each of the oil retention grooves 114c is longer than the circumferential dimension of the oil retention groove 114c. As a result of this configuration, the first inclination angle θ1 of each oil retention groove 114c becomes an acute angle. Furthermore, the axial dimension of each oil retention groove 114c is configured to be longer than the distance between the oil retention groove 114c and the scavenging port 114a in the axial direction.

[0098] Although not shown, similarly to the first embodiment, when each of the oil grooves 114c is viewed in a vertical section along an inclination direction relative to the central axis C (specifically, an oblique direction combining the upward direction and the rotational direction D1), the depth of the upper half in the inclination direction gradually becomes shallower toward the top. Specifically, the depth of each oil groove 114c is maximum at a portion located below the midpoint between the lower end 1142 and the upper end 1141, and then gradually becomes shallower from that portion toward the upper end 1141.

[0099] Thus, according to the second embodiment, each oil groove 114c is formed to extend in a second oblique direction that is a combination of an upward direction and a direction opposite to the rotation direction D1 so as to extend linearly along the vortex flow (the flow direction of the swirl flow). By forming it in this way, it becomes possible to scrape out the lubricating oil from the oil groove 114c by the swirl flow. Since the swirl flow occurs for each cycle, it becomes possible to replace the lubricating oil in conjunction with the progression of the cycle.

[0100] Furthermore, when oil retention grooves 114c are connected to each other, by connecting them via second oil retention groove 114d that is steeper than oil retention groove 114c, the dimension of oil retention groove 114c in the circumferential direction and therefore the dimension of oil retention groove 114c in the oblique direction can be made longer than second oil retention groove 114d. Of oil retention groove 114c and second oil retention groove 114d, making the dimension of oil retention groove 114c for scraping out lubricating oil by a swirl flow relatively longer is advantageous in promoting the scraping out of lubricating oil.

[0101] By promoting the scraping out of the lubricating oil from the oil groove 114c, it becomes possible to keep the oil groove 114c empty when the oil groove 114c should be functioning, such as when the lubricating oil is scraped downward from the inner wall portion 114b of the cylinder liner 114. This makes it possible to suppress the outflow of the lubricating oil.

[0102] In addition, the second oil retention groove 114d is steeper than the oil retention groove 114c, and therefore the lubricating oil can flow down more quickly. As shown in Fig. 6, by disposing the lower end of the second oil retention groove 114d (specifically, the portion that coincides with the lower end 1142 of the oil retention groove 114c) between the adjacent scavenging ports 114a, it is possible to suppress the outflow of the lubricating oil that has flowed down from the second oil retention groove 114d from the scavenging ports 114a.

[0103] (2) Modification of the Second Embodiment In the second embodiment, the multiple second oil grooves 114d are configured to extend in the opposite direction to the rotational direction D1 as they extend upward along the central axis C, but the second embodiment is not limited to such a configuration.

[0104] Fig. 7 is a view showing a modification of the second embodiment, corresponding to Fig. 4. As shown in Fig. 7, a cylinder liner 214 according to this modification includes an oil groove 214c similar to the configuration example shown in Fig. 6.

[0105] The cylinder liner 214 according to the modified example further includes a plurality of second oil retention grooves 214d extending in the rotational direction D1 as they extend upward along the central axis C so as to connect adjacent oil retention grooves 214c among the plurality of oil retention grooves 214c.

[0106] That is, in this modified example, the oil retention grooves 214c adjacent in the circumferential direction are configured to be connected via the second oil retention groove 214d. The second oil retention groove 214d extends linearly to connect the upper end 2141 of the oil retention groove 214c located on the upstream side (right side of the paper) in the rotation direction D1 to the lower end 2142 of the oil retention groove 214c located on the downstream side (left side of the paper) in the rotation direction D1. Each second oil retention groove 214d extends straight along an oblique direction in the circumferential direction (in other words, an oblique direction obtained by combining the upward direction and the rotation direction D1).

[0107] The inclination (second inclination angle) θ4 of the second oil-retaining groove 214d with respect to the central axis C is configured to be steeper than the inclination (first inclination angle) θ3 of the oil-retaining groove 114c, as in the example shown in Fig. 6. Specifically, the first inclination angle θ3 is preferably within a range of 10° to 45°.

[0108] Specifically, in this modification, similarly to the second embodiment, the dimension of oil retention groove 214c in the axial direction is substantially equal to the dimension of second oil retention groove 214d, while the dimension of oil retention groove 214c in the circumferential direction is longer than the dimension of second oil retention groove 214d (the dimension of second oil retention groove 214d in the circumferential direction is shorter than the dimension of oil retention groove 214c).

[0109] Similarly to the first embodiment, each lower end 2142 of the oil grooves 214c is disposed between adjacent scavenging ports 214a (specifically, at the middle position between adjacent scavenging ports 214a) in the circumferential direction. That is, a straight line extending from each lower end 2142 along the axial direction does not intersect with the opening of each scavenging port 214a.

[0110] Similarly to the first embodiment, each upper end 2141 of the oil retaining grooves 214c is disposed between adjacent scavenging ports 214a (specifically, at the middle position between adjacent scavenging ports 214a) in the circumferential direction. That is, a straight line extending from each upper end 2141 along the axial direction does not intersect with the opening of each scavenging port 214a.

[0111] Thus, according to this modification, each oil groove 214c is formed to extend in a diagonal direction that is a combination of the upward direction and the rotation direction D1 so as to extend linearly along the vortex flow (the flow direction of the swirl flow). By forming it in this way, it becomes possible to scrape out the lubricating oil from the oil groove 214c by the swirl flow. Since the swirl flow occurs for each cycle, it becomes possible to replace the lubricating oil in conjunction with the progress of the cycle.

[0112] Furthermore, when the oil retention grooves 214c are connected to each other, by connecting them via the second oil retention groove 214d that is steeper than the first oil retention groove 214c, the dimension of the oil retention groove 214c in the circumferential direction, and therefore the dimension of the oil retention groove 214c in the oblique direction, can be made longer than the second oil retention groove 214d. Of the oil retention groove 214c and the second oil retention groove 214d, making the dimension of the oil retention groove 214c for scraping out the lubricating oil by the swirl flow relatively longer is advantageous in promoting the scraping out of the lubricating oil.

[0113] By promoting the scraping out of the lubricating oil from the oil retaining groove 214c, it becomes possible to keep the oil retaining groove 214c empty when the oil retaining groove 214c should be functioning, such as when the lubricating oil is scraped downward from the inner wall portion 214b of the cylinder liner 214. This makes it possible to suppress the outflow of the lubricating oil.

[0114] In addition, the second oil retention groove 214d is steeper than the oil retention groove 214c, and therefore the lubricant can flow down more quickly. As shown in Fig. 7, the lower end of the second oil retention groove 214d (specifically, the portion that coincides with the lower end 2142 of the oil retention groove 214c) is disposed between the adjacent scavenging ports 214a, so that the lubricant that has flowed down from the second oil retention groove 114d can be prevented from flowing out of the scavenging ports 214a. [Explanation of symbols]

[0115] 1. Engine (Marine internal combustion engine) 13 Cylinder jacket 14,114,214 Cylinder Liner 14a, 114a, 214a scavenging ports 14b,114b,214b Inner wall part 14c,114c,214c Oil retaining groove 141,1141,2141 Upper end of oil groove 142,1142,2142 Lower end of oil groove 14d, 214d Second oil groove 21 Piston D1 Rotation direction

Claims

1. A cylindrical cylinder liner configured to draw air from a cylinder jacket as a piston reciprocates, If a direction extending along the central axis of the piston is defined as an axial direction, and a direction extending in an arc shape along the inner wall portion of the cylinder liner when viewed in a cross section perpendicular to the central axis is defined as a circumferential direction, A plurality of scavenging ports arranged side by side along the circumferential direction; A plurality of oil retaining grooves are provided on an inner wall portion above the plurality of scavenging ports and arranged in a line along the circumferential direction so as to correspond to each of the plurality of scavenging ports. Each of the plurality of scavenging ports, when viewed in a cross section perpendicular to the central axis, causes the air sucked from the cylinder jacket to flow in a vortex in a predetermined rotational direction which is one of the directions in the circumferential direction, The plurality of oil retention grooves are provided in a state in which adjacent oil retention grooves are separated from each other, and each of the oil retention grooves extends in the rotational direction as it moves upward along the central axis so as to extend linearly along the flow of the vortex, When the inner wall portion is expanded on a plane extending along the axial direction and the circumferential direction and viewed in plan, the dimension of each of the plurality of oil retention grooves in the axial direction is longer than the dimension of each of the plurality of oil retention grooves in the circumferential direction. A cylinder liner characterized by:

2. A cylindrical cylinder liner configured to draw air from a cylinder jacket as a piston reciprocates, If a direction extending along the central axis of the piston is defined as an axial direction, and a direction extending in an arc shape along the inner wall portion of the cylinder liner when viewed in a cross section perpendicular to the central axis is defined as a circumferential direction, A plurality of scavenging ports arranged side by side along the circumferential direction; A plurality of oil retaining grooves are provided above the plurality of scavenging ports and arranged in a line along the circumferential direction so as to correspond to each of the plurality of scavenging ports, Each of the plurality of scavenging ports, when viewed in a cross section perpendicular to the central axis, causes the air sucked from the cylinder jacket to flow in a swirling manner in a predetermined rotational direction which is any one direction in the circumferential direction, Each of the plurality of oil grooves extends in the rotational direction as it moves upward along the central axis so as to extend linearly along the flow of the vortex, Further provided are a plurality of second oil retention grooves extending in the rotational direction or in a direction opposite to the rotational direction as they extend upward along the central axis so as to connect adjacent oil retention grooves among the plurality of oil retention grooves, The inclination of the second oil retention groove with respect to the central axis is steeper than the inclination of the first oil retention groove. A cylinder liner characterized by:

3. 3. The cylinder liner according to claim 1 or 2, Each lower end of the plurality of oil retaining grooves is disposed between adjacent ones of the plurality of scavenging ports in the circumferential direction. A cylinder liner characterized by:

4. 4. The cylinder liner according to claim 3, The lower end portions of the plurality of oil retaining grooves are disposed at intermediate positions between the adjacent scavenging ports in the circumferential direction. A cylinder liner characterized by:

5. The cylinder liner according to any one of claims 1 to 4, The upper end portions of the plurality of oil retaining grooves are disposed between the adjacent scavenging ports in the circumferential direction. A cylinder liner characterized by:

6. The cylinder liner according to any one of claims 1 to 5, Among the adjacent oil retention grooves, an upper end portion of the oil retention groove located on the upstream side in the rotation direction and a lower end portion of the oil retention groove located on the downstream side in the rotation direction are arranged to be aligned along the axial direction. A cylinder liner characterized by:

7. 3. The cylinder liner according to claim 2, The dimension of each of the plurality of oil retention grooves in the axial direction is longer than the dimension of the oil retention groove in the circumferential direction. A cylinder liner characterized by:

8. A cylinder liner according to any one of claims 1 to 7, When viewed in a vertical cross section along a direction inclined to the central axis, each of the plurality of oil retaining grooves has a depth of at least an upper half in the direction inclined, which depth gradually becomes shallower toward the top. A cylinder liner characterized by:

9. A cylinder liner according to any one of claims 1 to 8. A marine internal combustion engine characterized by:

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