Internal combustion engine

Abstract

To suppress a flow of a lubricant toward a combustion chamber during the reciprocation of a piston.SOLUTION: An internal combustion engine comprises a second pressure ring 42 attached to a ring groove 32 which is formed at an external peripheral face 30a of a piston 30 reciprocating in a cylinder 12, and an oil ring 43 attached to a ring groove 33 which is formed at a skirt part side from the ring groove 32 at the external periphery, and regulating an oil film of an inner wall face of the cylinder 12. The piston 30 has a recess 50 which is formed at a third land 36 located between the ring groove 32 and the ring groove 33 at the external peripheral face 30a. An outside diameter of a first portion 36a of the third land 36 at the second pressure ring 42 side from the recess 50 is larger than an outside diameter of a second portion 36b of the third land 36 at the oil ring 43 side from the recess 50.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] The following Patent Document 1 discloses a technology for providing a recess in the land between the ring groove in which the piston pressure ring is mounted and the ring groove in which the oil ring is mounted, in order to reduce the consumption of lubricating oil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-194222 A Summary of the Invention [Problem to be solved by the invention]

[0004] Lubricating oil that adheres to the inner wall surface of the cylinder or is left behind by the compression ring moves to the combustion chamber through the gap of the compression ring or the clearance between the compression ring and the ring groove and is consumed. However, the recess in Patent Document 1 is designed taking into consideration only the gap of the compression ring, so it cannot sufficiently prevent the lubricating oil from moving toward the combustion chamber through the clearance when the piston reciprocates.

[0005] The present invention has been made in consideration of these points, and has an object to suppress lubricating oil from flowing toward the combustion chamber when the piston reciprocates. [Means for solving the problem]

[0006] In one aspect of the present invention, an internal combustion engine is provided, comprising: a piston that reciprocates within a cylinder; a pressure ring mounted in a first groove formed on the outer peripheral surface of the piston; and an oil ring mounted in a second groove formed on the outer peripheral surface closer to the skirt portion than the first groove and regulating an oil film on the inner wall surface of the cylinder, wherein the piston has a recess formed in a land located between the first groove and the second groove on the outer peripheral surface, and the outer diameter of a first portion of the land closer to the pressure ring than the recess is larger than the outer diameter of a second portion of the land closer to the oil ring than the recess.

[0007] The recess may be formed on the outer circumferential surface so as to extend around the entire circumference in a circumferential direction.

[0008] The side surface of the recess on the oil ring side may be an inclined surface that is inclined such that the distance between the side surface and the opposing side surface of the recess increases with increasing distance from the bottom surface.

[0009] The depth of the recess may be greater than the radial width of the oil ring.

[0010] Also, the axial length of the first portion may be greater than the axial length of the second portion.

[0011] In addition, the first portion may include a protrusion protruding from an opposing surface facing the second portion toward the second portion, and the protrusion may be located at an outer end of the first portion in the radial direction of the piston.

[0012] The protruding portion may be located outwardly of the second portion in the radial direction.

[0013] The recesses may be formed in a plurality at predetermined intervals in the circumferential direction on the outer circumferential surface.

[0014] The pressure ring may have a gap, which is a gap between both ends in a circumferential direction, and the recess may be formed at the same position as the gap in the circumferential direction. Effect of the Invention

[0015] According to the present invention, it is possible to suppress lubricating oil from flowing toward the combustion chamber when the piston reciprocates. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine 1 according to one embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a piston 30. [Diagram 3] 2 is a schematic diagram showing a detailed configuration of a third land 36. FIG. [Figure 4] 1 is a schematic diagram showing the state of the lubricating oil in the ring groove 33 and the third land 36 when the piston 30 moves to the top dead center. FIG. [Diagram 5] 1 is a schematic diagram showing the state of the lubricating oil in the ring groove 33 and the third land 36 when the piston 30 moves to the bottom dead center. FIG. [Figure 6] 4 is a schematic diagram showing a joint 42a of the second compression ring 42. FIG. [Figure 7] 13 is a schematic diagram showing a third land 136 according to a first modified example. FIG. [Figure 8] 13 is a schematic diagram showing a third land 236 according to a second modified example. FIG. [Figure 9] 13 is a schematic diagram showing a third land 336 according to a third modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <Overview of the internal combustion engine> 1 is a schematic diagram showing the configuration of an internal combustion engine 1 according to one embodiment. Here, the internal combustion engine 1 is mounted on a vehicle such as a truck, but is not limited thereto and may be mounted on a ship, for example.

[0018] The internal combustion engine 1 is, for example, a diesel engine. The internal combustion engine 1 is a power source that generates power to run a vehicle by burning and expanding an intake fuel mixture in a combustion chamber 2. The internal combustion engine 1 has a cylinder block 10, a cylinder head 20, and a piston 30.

[0019] The cylinder block 10 has a cylinder 12 that houses a piston 30 so that the piston 30 can reciprocate, and a crankcase 16 that houses a crankshaft 45. An oil pan 18 that stores lubricating oil is attached to the crankcase 16.

[0020] The cylinder head 20 is provided on the upper part of the cylinder block 10. The cylinder head 20 has an injector 22, an intake port 23, an exhaust port 24, an intake valve 25, and an exhaust valve 26. The injector 22 injects fuel into a combustion chamber 2 defined by the top surface of the piston 30, the inner wall surface 13 of the cylinder 12, and the cylinder head 20. The intake port 23 is an intake port that introduces fresh air into the combustion chamber 2. The exhaust port 24 is an exhaust port that guides exhaust gas from the combustion chamber 2. The intake valve 25 introduces fresh air from the intake port 23 into the combustion chamber 2 by opening and closing. The exhaust valve 26 guides exhaust gas from the combustion chamber 2 to the exhaust port 24 by opening and closing.

[0021] The piston 30 reciprocates within the cylinder 12. When the piston 30 reciprocates between the top dead center and the bottom dead center, it slides on the inner wall surface 13 of the cylinder 12. Lubricating oil is supplied to the inner wall surface 13 to form an oil film. A plurality of annular piston rings are provided on the upper part of the outer circumferential surface 30a of the piston 30 to seal in the combustion gas and maintain the oil film at a predetermined thickness. A skirt portion 38 is provided on the lower part of the piston 30. The skirt portion 38 is a portion of the piston 30 below the piston pin 39.

[0022] 2 is a schematic diagram showing the piston 30. The piston 30 is provided with a first compression ring 41, a second compression ring 42, and an oil ring 43 as piston rings. Specifically, the first compression ring 41, the second compression ring 42, and the oil ring 43 are provided in this order from above the outer circumferential surface 30a of the piston 30.

[0023] The first compression ring 41 and the second compression ring 42 are rings for maintaining airtightness inside the cylinder 12. The first compression ring 41 and the second compression ring 42 have a sealing function to prevent combustion gas from leaking from the gap between the piston 30 and the cylinder 12.

[0024] The oil ring 43 regulates the oil film of the lubricating oil adhering to the inner wall surface 13 of the cylinder 12. Specifically, the oil ring 43 scrapes off the lubricating oil adhering to the inner wall surface 13 of the cylinder 12 and regulates the thickness to a predetermined thickness when the piston 30 reciprocates. The predetermined thickness is set to a thickness that does not cause seizure in the cylinder 12.

[0025] The outer peripheral surface 30a of the piston 30 is provided with ring grooves 31, 32, and 33. The ring groove 31, the ring groove 32, and the ring groove 33 are provided in this order on the outer peripheral surface 30a of the piston 30 from the top dead center side. In other words, the ring groove 33 is formed on the outer peripheral surface 30a closer to the skirt portion 38 than the ring grooves 31 and 32. The ring grooves 31, 32, and 33 are formed at predetermined intervals in the axial direction. The ring grooves 31, 32, and 33 are annular grooves formed to a predetermined depth along the outer peripheral surface 30a. A first pressure ring 41 is attached to the ring groove 31, a second pressure ring 42 is attached to the ring groove 32, and an oil ring 43 is attached to the ring groove 33. In this embodiment, the ring groove 32 corresponds to the first groove, and the ring groove 33 corresponds to the second groove.

[0026] On the outer peripheral surface 30a of the piston 30, a first land 34 is formed in a portion above the ring groove 31, a second land 35 is formed between the ring groove 31 and the ring groove 32, and a third land 36 is formed between the ring groove 32 and the ring groove 33. Each of the first land 34, the second land 35, and the third land 36 forms a part of the outer peripheral surface 30a of the piston 30.

[0027] Incidentally, the lubricating oil adhering to the inner wall surface 13 of the cylinder 12 moves to the combustion chamber 2 through the sliding surfaces and joints of the first compression ring 41 and the second compression ring 42 (collectively referred to as the compression rings here) or the clearances between the compression rings and the ring grooves 32, 33 during the reciprocating motion of the piston 30. The lubricating oil that moves to the combustion chamber 2 splashes into the combustion chamber 2 and evaporates or burns in the combustion chamber 2. In contrast, in this embodiment, a recess 50 is provided in the third land 36 in order to suppress the movement of the lubricating oil into the combustion chamber 2, which will be described in detail later.

[0028] <Detailed configuration of the recess 50> Fig. 3 is a schematic diagram showing a detailed configuration of the third land 36. For ease of explanation, the second pressure ring 42 and the oil ring 43 are not shown in Fig. 3.

[0029] A recess 50 is formed in a third land 36 located between the ring groove 32 and the ring groove 33 on the outer peripheral surface 30a of the piston 30. The recess 50 is provided in a central portion of the third land 36 in the axial direction of the piston 30. The recess 50 is formed on the outer peripheral surface 30a of the piston 30 so as to go around once in the circumferential direction.

[0030] Here, the length L1 of the recess 50 in the axial direction of the piston 30 is ½ of the axial length L2 of the third land 36. However, without being limited thereto, the length L1 of the recess 50 may be greater than ½ of the length L2 of the third land 36, or may be ¼ or greater of the length L2 of the third land 36. Note that the length L1 of the recess 50 may be less than ½ of the length L2 of the third land 36. Furthermore, the axial length L1 of the recess 50 is greater than the axial length (length L3 shown in FIG. 4) of the oil ring 43. Without being limited to the above, the length L1 of the recess 50 may be equal to or greater than ½ of the length L3 of the oil ring 43. The relationship between the depth L4 of the recess 50 and the axial length of the oil ring 43 is not limited to the above example.

[0031] Here, the depth L4 of the recess 50 is greater than the radial width (width L5 shown in FIG. 4) of the oil ring 43. Without being limited to the above, the depth L4 of the recess 50 may be equal to or greater than ½ of the width L5 of the oil ring 43. The relationship between the depth L4 of the recess 50 and the radial width of the oil ring 43 is not limited to the above example. Further, the depth L4 of the recess 50 is set to be a predetermined ratio with respect to the diameter of the piston 30. For example, the depth L4 of the recess 50 is 5% of the diameter of the piston 30. By providing the recess 50 with the above-mentioned length L1 and depth L4, a large amount of lubricating oil tends to temporarily remain in the recess 50.

[0032] The bottom surface 53 of the recess 50 is a curved surface with a predetermined curvature. In addition, of the upper surface 51 and the lower surface 52 which are both side surfaces connected to the bottom surface 53, the lower surface 52 is an inclined surface. The lower surface 52 on the oil ring 43 side is inclined so that the distance from the upper surface 51 increases as it moves away from the bottom surface 53. The inclination angle α of the lower surface 52 is, for example, 30 degrees. This makes it easier for the lubricating oil in the recess 50 to move along the lower surface 52.

[0033] The outer diameter of the first portion 36a of the third land 36 closer to the second compression ring 42 than the recess 50 is larger than the outer diameter of the second portion 36b of the third land 36 closer to the oil ring 43 than the recess 50. That is, the distance between the first portion 36a and the inner wall surface 13 of the cylinder 12 is smaller than the distance between the second portion 36b and the inner wall surface 13 (see FIG. 4). Therefore, the amount of lubricating oil that passes between the first portion 36a and the inner wall surface 13 and moves toward the ring groove 32 is reduced.

[0034] The axial length L6 of the first portion 36a is greater than the axial length L7 of the second portion 36b. In other words, the thickness of the first portion 36a is greater than the thickness of the second portion 36b. When the pressure in the combustion chamber increases, a force acts on the first portion 36a via the second compression ring 42, but by increasing the thickness of the first portion 36a, it becomes easier to ensure the strength of the first portion 36a to withstand the above-mentioned force.

[0035] Fig. 4 is a schematic diagram showing the state of the lubricating oil in the ring groove 33 and the third land 36 when the piston 30 moves (rises) to the top dead center. Fig. 5 is a schematic diagram showing the state of the lubricating oil in the ring groove 33 and the third land 36 when the piston 30 moves (descends) to the bottom dead center. In Figs. 4 and 5, the hatched parts indicate the position of the lubricating oil, and the dashed arrows indicate the flow of the lubricating oil.

[0036] 4, when the piston 30 rises, the lubricating oil adhering to the cylinder 12 above the third land 36 (in other words, the lubricating oil that has passed through the second compression ring 42) flows into the recess 50 of the third land 36. The lubricating oil that has flowed into the recess 50 temporarily remains therein. Since the lower surface 52 of the recess 50 is an inclined surface, the lubricating oil remaining in the recess 50 is easily moved toward the oil ring 43. The lubricating oil that has moved toward the oil ring 43 is scraped off by the oil ring 43 as the piston 30 rises, and flows into the ring groove 33. Since the lubricating oil temporarily remains in the recess 50, the amount of lubricating oil scraped off by the oil ring 43 increases when the piston 30 rises, and the amount of lubricating oil that flows into the ring groove 33 also increases. The lubricating oil in the ring groove 33 moves downward from the ring groove 33 as the piston 30 rises. As a result, the lubricating oil adhering to the cylinder 12 is easily made to a desired thickness, and the lubricating oil moving toward the combustion chamber 2 can be suppressed.

[0037] As shown in Fig. 5, when the piston 30 descends, the oil ring 43 scrapes off the lubricating oil adhering to the cylinder 12. The lubricating oil scraped off by the oil ring 43 flows into the ring groove 33. On the other hand, the lubricating oil not scraped off by the oil ring 43 flows into the recess 50 of the third land 36 above the ring groove 33. Specifically, the first portion 36a of the third land 36 scrapes off the lubricating oil not scraped off by the oil ring 43. The lubricating oil scraped off by the first portion 36a flows into the recess 50. In addition, since the bottom surface 53 and the lower side surface 52 in the recess 50 are curved, the lubricating oil that has flowed into the recess 50 can move more easily along the bottom surface 53 and the lower side surface 52. This increases the amount of lubricating oil flowing into the recess 50, so that the lubricating oil that has not been scraped off by the oil ring 43 can be easily collected in the recess 50. As a result, the lubricating oil can be prevented from moving above the third land 36 (to the ring groove 32).

[0038] By providing the recess 50, when the piston 30 moves to the bottom dead center, the lubricating oil that has not been scraped off by the oil ring 43 can be prevented from moving toward the second land 35 and the first land 34. This makes it possible to prevent the lubricating oil from moving to the combustion chamber 2 via the clearance between the ring groove 32 and the second compression ring 42 and the clearance between the ring groove 31 and the first compression ring 41 and being evaporated.

[0039] In the above description, the recess 50 is formed around the outer circumferential surface 30a of the piston 30, but this is not limited thereto. For example, a plurality of recesses 50 may be formed at predetermined intervals in the circumferential direction on the outer circumferential surface 30a. Even in this case, by providing the recess 50, it is possible to suppress the movement of the lubricating oil adhering to the cylinder 12 to the first land 34. It is preferable that the recess 50 is formed at the same position as the abutment 42a of the second compression ring 42 in the circumferential direction.

[0040] Fig. 6 is a schematic diagram showing the joint 42a of the second compression ring 42. The joint 42a of the second compression ring 42 is a gap (a gap) between the ends of the second compression ring 42, as shown in Fig. 6. Providing the joint 42a can suppress deformation of the second compression ring 42 due to thermal expansion. Note that the first compression ring 41 also has a joint identical to the joint 42a of the second compression ring 42.

[0041] If there is a joint 42a between the first compression ring 41 and the second compression ring 42, the thickness of the lubricating oil film may become larger only at the joint 42a, or the lubricating oil adhering to the cylinder 12 may easily pass through the joint 42a and flow toward the combustion chamber. In contrast, in this embodiment, the recess 50 is formed at the same position as the abutment 42a in the circumferential direction, so that when the piston 30 moves to the top dead center, the lubricating oil in the portion where the film thickness is large due to the abutment 42a tends to move into the recess 50, thereby making it possible to reduce the film thickness of the lubricating oil. On the other hand, when the piston 30 moves to the bottom dead center, the lubricating oil heading toward the abutment 42a is scraped off by the recess 50, so that less lubricating oil passes through the abutment 42a, and the lubricating oil heading toward the combustion chamber 2 can be suppressed.

[0042] <Modification> FIG. 7 is a schematic diagram showing a third land 136 according to a first modified example. In the first modified example, the configuration of the third land 136 is different from the configuration of the third land 36 described above, but the other configurations are similar. The configuration of the third land 136 will be described below.

[0043] The first portion 136a of the third land 136 includes a protruding portion 160 protruding from an opposing surface (upper side surface 151) opposing the second portion 136b toward the second portion 136b (specifically, the lower side surface 152). The protruding portion 160 is formed parallel to the axial direction of the piston 30. The cross-sectional shape of the protruding portion 160 is rectangular, but is not limited thereto, and may be a cross-sectional shape tapered toward the tip.

[0044] The protruding portion 160 is located at an outer end of the first portion 136a in the radial direction of the piston 30. Specifically, the protruding portion 160 is located outward of the second portion 136b in the radial direction. In other words, the distance between the protruding portion 160 and the cylinder 12 is smaller than the distance between the second portion 136b and the cylinder 12.

[0045] In the first modified example, by providing the protrusion 160 on the third land 136, the lubricating oil that the oil ring 43 was unable to scrape off when the piston 30 moved to the bottom dead center can be easily scraped off by the protrusion 160. As a result, the lubricating oil is easily collected in the recess 150, and the movement of the lubricating oil to the combustion chamber 2 can be suppressed.

[0046] 8 is a schematic diagram showing a third land 236 according to the second modification. In the third land 236 of the second modification, the shape of the upper surface 251 is different from that of the third land 36. A portion of the upper surface 251 of the third land 236 connected to the bottom surface 253 is curved so as to be concave upward. Since the upper surface 251 is curved, the lubricating oil flows more easily in the recess 250, and the amount of lubricating oil flowing into the recess 250 increases.

[0047] 9 is a schematic diagram showing a third land 336 according to the third modified example. In the recess 350 of the third land 336 of the third modified example, unlike the recess 50, the lower side 352 is not inclined, and the upper side 351 and the lower side 352 are parallel. On the other hand, the bottom surface 353 of the recess 350 is a large curved surface. Specifically, the bottom surface 353 is semicircular. In the third modified example, since the bottom surface 353 is a large curved surface, the lubricating oil flows easily in the recess 350, and the amount of lubricating oil flowing into the recess 350 increases.

[0048] In the above description, the piston 30 is provided with two pressure rings, the first pressure ring 41 and the second pressure ring 42, as the pressure rings mounted in the ring grooves on the outer circumferential surface 30a of the piston 30. However, this is not limited to this. For example, the piston 30 may be provided with one or three pressure rings on the outer circumferential surface 30a of the piston 30. In the above description, the recess 50 is provided only in the third land 36 among the first land 34, the second land 35, and the third land 36, but this is not limited to the above. For example, the recess 50 may be provided in the third land 36 and the second land 35, or may be provided only in the second land 35. When there are three compression rings, the recess 50 may be provided in the lower two second lands and the third land, and in the fourth land to which the oil ring 43 is attached.

[0049] <Effects of this embodiment> In the internal combustion engine 1 of the above-described embodiment, the recess 50 is formed in the third land 36 located between the ring groove 32 and the ring groove 33. The outer diameter of the first portion 36a of the third land 36 closer to the second compression ring 42 than the recess 50 is larger than the outer diameter of the second portion 36b closer to the oil ring 43 than the recess 50. By providing the recess 50 in the third land 36, when the piston 30 moves to the bottom dead center, the first portion 36a of the third land 36 scrapes off the lubricating oil that has not been scraped off by the oil ring 43, and the lubricating oil scraped off by the first portion 36a flows into the recess 50. This makes it possible to prevent the lubricating oil that has not been scraped off by the oil ring 43 from moving toward the second land 35 and the first land 34, thereby preventing the lubricating oil from moving to the combustion chamber 2 and being consumed.

[0050] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0051] 1. Internal combustion engine 12 cylinders 30 Piston 30a Outer surface 32 Ring groove 33 Ring groove 36 Land 3 36a Part 1 36b Part 2 38 Skirt Club 42 Second Pressure Ring 42a Aiguchi 43 Oil Ring 50 Recess 52 Lower side 160 Protrusion

Claims

1. A piston that reciprocates within a cylinder; a compression ring mounted in a first groove formed on an outer circumferential surface of the piston; an oil ring that is attached to a second groove that is formed on the outer circumferential surface closer to the skirt portion than the first groove and that regulates an oil film on an inner wall surface of the cylinder; Equipped with the piston has a recess formed in a land located between the first groove and the second groove on the outer circumferential surface, an outer diameter of a first portion of the land closer to the pressure ring than the recessed portion is larger than an outer diameter of a second portion of the land closer to the oil ring than the recessed portion; Internal combustion engine.

2. The recess is formed on the outer circumferential surface in a circumferential direction.

2. The internal combustion engine of claim 1.

3. The side surface of the recess on the oil ring side is an inclined surface that is inclined such that the distance between the side surface and the opposing side surface of the recess increases as the side surface is away from the bottom surface.

2. The internal combustion engine of claim 1.

4. The depth of the recess is greater than the radial width of the oil ring.

2. The internal combustion engine of claim 1.

5. The axial length of the first portion is greater than the axial length of the second portion.

2. The internal combustion engine of claim 1.

6. the first portion includes a protruding portion protruding from an opposing surface facing the second portion toward the second portion, The protrusion is located at an outer end of the first portion in a radial direction of the piston.

2. The internal combustion engine of claim 1.

7. The protruding portion is located outwardly of the second portion in the radial direction.

7. An internal combustion engine according to claim 6.

8. The recesses are formed in a plurality of portions at predetermined intervals in the circumferential direction on the outer circumferential surface.

2. The internal combustion engine of claim 1.

9. The compression ring has a gap between both ends in a circumferential direction, The recess is formed at the same position as the gap in the circumferential direction.

9. An internal combustion engine according to claim 8.

Images