Piston of internal combustion engine

Abstract

To provide a piston 1 of an internal combustion engine capable of reducing sliding resistance on an anti-thrust side while holding lubricant at a center portion of a skirt part on a thrust side.SOLUTION: A piston of an internal combustion engine has skirt parts on a thrust side and an anti-thrust side, and comprises a plurality of first grooves arranged in a first region located at the centers of the skirt parts on the thrust side and the anti-thrust side and extending in a direction intersecting a sliding direction of the piston. The first region on the thrust side is wider than the first region on the anti-thrust side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to pistons for internal combustion engines. [Background technology]

[0002] Conventionally, there is known a piston for an internal combustion engine having a patterned design formed on the skirt portion (see, for example, Patent Document 1). The piston for the internal combustion engine in Patent Document 1 has a first guide groove and a second guide groove that are inclined from the center of the skirt portion on the thrust side and the anti-thrust side toward the ends in the width direction. The first guide groove and the second guide groove are formed by a coating applied to the skirt portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-223164 Summary of the Invention [Problem to be solved by the invention]

[0004] The piston of the internal combustion engine in Patent Document 1 guides the lubricating oil between the piston and cylinder into the first and second guide grooves, allowing the lubricating oil to flow to the center of the skirt. However, Patent Document 1 does not disclose a structure for maintaining the oil film in the center of the skirt. The center of the skirt on the thrust side receives the least amount of lubricating oil near top dead center, but this is also the start of the expansion stroke, so the skirt is subjected to a large load. Therefore, it is preferable for the center of the skirt on the thrust side to continue to retain lubricating oil. Meanwhile, the load received from the cylinder on the anti-thrust side is smaller than that on the thrust side. For this reason, it is preferable for the lubricating oil to flow along the surface of the skirt, reducing the sliding resistance of the piston.

[0005] An object of the present disclosure is to provide a piston for an internal combustion engine that can retain lubricating oil in the center portion of the skirt portion on the thrust side while reducing sliding resistance on the anti-thrust side. [Means for solving the problem]

[0006] The piston of an internal combustion engine according to the present disclosure is a piston of an internal combustion engine having skirt portions on a thrust side and an anti-thrust side, and is provided with a plurality of first grooves arranged in a first region located at the center of the skirt portions on the thrust side and the anti-thrust side and extending in a direction intersecting the sliding direction of the piston, and the first region on the thrust side is wider than the first region on the anti-thrust side. [Effects of the Invention]

[0007] In this internal combustion engine piston, the first grooves arranged in the first regions on the thrust side and anti-thrust side retain lubricating oil. However, because the first grooves extend in a direction intersecting the sliding direction, the lubricating oil does not flow easily, resulting in sliding resistance. By making the first region wider on the thrust side compared to the anti-thrust side, it is easier to retain lubricating oil than on the anti-thrust side. By reducing the first region on the anti-thrust side compared to the thrust side, sliding resistance is reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 illustrates a piston of an internal combustion engine according to one embodiment of the present disclosure. [Figure 2] FIG. 1 illustrates a thrust side of a piston according to one embodiment of the present disclosure. [Figure 3] FIG. 1 illustrates a non-thrust side of a piston according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. In the drawings, the sliding direction of an internal combustion engine E is indicated as P, the intake side as IN, the exhaust side as EX, the front side as FS, and the rear side as BS. In this embodiment, an example will be described in which a cylinder 2 (described later) is arranged vertically and a piston 1 slides vertically. However, the cylinder 2 may be arranged at an angle relative to the vertical direction, as in a V-type engine, for example. Furthermore, the cylinder 2 may be arranged horizontally, as in a horizontally opposed engine, for example.

[0010] As shown in FIG. 1, a piston 1 of an internal combustion engine E slides inside a cylinder 2. In this embodiment, the internal combustion engine E is a four-stroke reciprocating engine. The internal combustion engine E takes in air through an intake passage 3, burns the air in a combustion chamber 4, and discharges the exhaust gas into an exhaust passage 5. The piston 1 compresses the air-fuel mixture while rising to top dead center during the compression stroke. During the expansion stroke, the piston 1 rotates a crankshaft 6 clockwise while receiving combustion pressure. Therefore, the exhaust side EX of the piston 1 is the thrust side, and the intake side IN is the anti-thrust side.

[0011] As shown in Figures 2 and 3, the piston 1 has a top land 10, a second land 11, a third land 12, and a skirt portion 13. The piston 1 is arranged in the following order from the top dead center side in the sliding direction P: the top land 10, the second land 11, the third land 12, and the skirt portion 13. Ring grooves 14 are arranged between the top land 10 and the second land 11 and between the second land 11 and the third land 12, and piston rings (not shown) that come into contact with the cylinder 2 are arranged in the ring grooves. The piston rings slide while coming into contact with the cylinder 2, and prevent the combustion pressure in the combustion chamber 4 from leaking into the crankcase 7 (see Figure 1).

[0012] An oil ring groove 15 is disposed between the third land 12 and the skirt portion 13. The oil ring groove 15 is located on the top dead center side of the skirt portion 13 in the sliding direction P of the piston, and an oil ring is inserted into the oil ring groove 15. The oil ring slides in contact with the cylinder 2, sealing the gap between the cylinder 2 and the piston 1. As shown in FIG. 3, an oil hole 16 is disposed on the anti-thrust side of the oil ring groove 15, supplying lubricating oil (oil) toward the skirt portion 13. An oil hole 16 may also be disposed on the thrust side. In this embodiment, four oil holes 16 are disposed: two near the center of the piston 1 in the front-to-rear direction (near the center on the anti-thrust side) and one each on either side at a distance. The oil holes 16 discharge the lubricating oil scraped out by the oil ring.

[0013] The skirt portion 13 has the function of adjusting the posture of the piston 1 while contacting the cylinder 2. As shown in FIG. 2, the skirt portion 13 moves toward the bottom dead center in the sliding direction P during the expansion stroke. Therefore, lubricating oil flows on the surface of the skirt portion 13 from the bottom dead center toward the top dead center in the sliding direction P. As shown in FIG. 3, the skirt portion 13 moves toward the top dead center in the sliding direction P during the compression stroke. Therefore, lubricating oil flows on the surface of the skirt portion 13 from the top dead center toward the bottom dead center in the sliding direction P.

[0014] As shown in FIG. 2, the piston 1 includes a first groove 20, a second groove 21, a third groove 22, a fourth groove 23, and a contact surface 24 on the thrust side. As shown in FIG. 3, the piston 1 includes a first groove 20, a second groove 21, and a third groove 22 on the anti-thrust side. As shown in FIGS. 2 and 3, the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 are each a plurality of recesses formed by recessing the surface of the skirt portion 13. In this embodiment, the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 are each formed into an elliptical shape with a maximum length of 200 micrometers in the longitudinal direction and a maximum length of approximately 40 micrometers in the lateral direction. Furthermore, in this embodiment, the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 are each formed by laser processing the skirt portion 13.

[0015] First, the thrust side groove will be explained using FIG.

[0016] The first groove 20 is disposed in the first region S1. The first groove 20 extends in a direction intersecting the sliding direction P of the piston 1. In this embodiment, the longitudinal direction of the ellipse of the first groove 20 is oriented in the front-to-rear direction (a direction perpendicular to the sliding direction P). The first region S1 is disposed near the center of the skirt portion in the front-to-rear direction. In the first region S1 on the thrust side, the piston 1 hits the cylinder 2 hard, and the skirt portion 13 receives a high load from the cylinder 2. For this reason, the lubricating oil between the skirt portion 13 and the cylinder 2 easily escapes, and the oil film is easily broken. By making the first groove 20 an ellipse whose longitudinal direction extends in the front-to-rear direction, the lubricating oil is less likely to escape from the first groove 20, and the lubricating oil is easily retained.

[0017] The second groove 21 is disposed in the second region S2. The second region S2 is located closer to the end of the skirt portion 13 in the front-rear direction and closer to the end of the skirt portion 13 on the bottom dead center side in the sliding direction P than the first region. The second groove 21 is formed such that the top dead center side of the second groove 21 is inclined in a direction intersecting the sliding direction P as it approaches the first region S1. In this embodiment, the top dead center side of the second groove 21 is inclined toward the first region S1 as it approaches the first region S1, thereby inclining the second groove 21 in the front-rear direction. That is, the thrust-side second groove 21 extends closer to the oil ring groove 15 on the top surface side of the piston 1 as it approaches the first region S1. By inclining the second groove 21 in this direction, the second groove 21 directs lubricating oil entering from the bottom dead center side toward the first region S1. As a result, it is possible to prevent the lubricating oil in the first region S1 from escaping from the first groove 20 and being interrupted.

[0018] The third groove 22 is disposed in the third region S3. The third region S3 is located closer to the end of the skirt portion 13 in the front-to-rear direction than the second region S2. The third groove 22 extends along the sliding direction P of the piston 1. In this embodiment, the longitudinal direction of the ellipse of the third groove 22 faces the sliding direction P. By forming the third groove 22 in this way, the lubricating oil can easily flow from the bottom dead center side to the top dead center side in the sliding direction P. As a result, sliding resistance is reduced in the third region S3.

[0019] The fourth groove 23 is disposed in the fourth region S4. The fourth region S4 is located along the oil ring groove 15. The fourth groove 23 extends in the sliding direction of the piston. In this embodiment, the first row of fourth grooves 23 along the oil ring groove 15 has the longitudinal direction of the ellipse oriented in the sliding direction P. The second row of fourth grooves 23, which is disposed on the bottom dead center side of the first row of fourth grooves 23, is formed so that its bottom dead center side faces the first region S1. In other words, the second row of fourth grooves 23 is inclined so that the bottom dead center side of the longitudinal direction of the ellipse approaches the center of the skirt portion 13 as it approaches the center of the skirt portion 13. The fourth groove 23 directs the lubricating oil scraped out by the oil ring toward the bottom dead center side while in contact with the cylinder 2 toward the first region S1.

[0020] The contact surface 24 is provided between the first region S1 and the second region S2. The contact surface 24 is the portion of the skirt portion 13 that receives the greatest load from the cylinder 2. For this reason, the first groove 20 and the second groove 21 are not located on the contact surface 24. This makes it easier to distribute the load that the skirt portion 13 receives from the cylinder 2.

[0021] The ratio of the total area of ​​the first grooves 20 to the area of ​​the skirt portion 13 in the first region S1 on the thrust side (hereinafter referred to as the area ratio in the specification) is approximately 5 to 10 percent. The area ratios of the second region S2, the third region S3, and the fourth region S4 on the thrust side are approximately 10 to 20 percent. Therefore, the first region S1 has a larger surface area of ​​the skirt portion 13 that comes into contact with the cylinder 2 than the second region S2, the third region S3, and the fourth region S4. This makes it easier for the skirt portion 13 to distribute the load that it receives from the cylinder 2.

[0022] Next, the groove on the anti-thrust side will be described with reference to FIG.

[0023] The first groove 20 on the anti-thrust side is disposed in the first region S1 on the anti-thrust side. The first groove 20 extends in a direction intersecting the sliding direction P of the piston 1. In this embodiment, the longitudinal direction of the ellipse of the first groove 20 is oriented in the front-to-rear direction (the direction perpendicular to the sliding direction P). This makes it difficult for lubricating oil to escape from the first groove 20, and the piston 1 can easily retain the lubricating oil.

[0024] The second groove 21 on the anti-thrust side is disposed in the second region S2. The second region S2 is located closer to the end of the skirt portion 13 in the front-rear direction than the first region S1. In this embodiment, the second region S2 on the anti-thrust side is disposed adjacent to the first region S1 at the front and rear. The second groove 21 is formed so that the bottom dead center side of the second groove 21 is inclined in a direction intersecting the sliding direction P as it approaches the first region S1. In this embodiment, the second grooves 21 on the front and rear of the first region S1 are inclined so that the bottom dead center side of the second groove 21 approaches the first region S1 as it approaches the first region S1. In other words, the second grooves 21 on the front and rear of the first region S1 on the anti-thrust side extend closer to the oil ring groove 15 on the top surface side of the piston as they move away from the first region S1. By inclining the second groove 21 in this direction, the second groove 21 on the anti-thrust side directs lubricating oil entering from the top dead center side toward the first region S1. As a result, the lubricating oil in the first region S1 can be prevented from escaping from the first groove 20 and being cut off.

[0025] The third groove 22 on the anti-thrust side is disposed in the third region S3. The third region S3 is located closer to the end of the skirt portion 13 in the front-to-rear direction than the second region S2 and closer to the end of the first region S1 on the bottom dead center side. The third groove 22 extends along the sliding direction P of the piston 1. In this embodiment, the longitudinal direction of the ellipse of the third groove 22 is oriented in the sliding direction P.

[0026] The first region S1 on the thrust side is wider than the first region S1 on the anti-thrust side. Furthermore, the third region S3 on the anti-thrust side is wider than the third region S3 on the thrust side. The load that the skirt portion 13 receives from the cylinder 2 is lower on the anti-thrust side than on the thrust side. Therefore, the anti-thrust side is more likely to retain lubricating oil in the first region S1 than on the thrust side. Therefore, on the anti-thrust side, the area of ​​the first region S1 is smaller than on the thrust side, and the third region S3 is larger than on the thrust side. This allows the sliding resistance on the anti-thrust side of this piston 1 to be reduced.

[0027] The area ratio of the first region S1 on the anti-thrust side is approximately 5 to 10 percent. The area ratios of the second region S2 and the third region S3 on the anti-thrust side are approximately 10 to 20 percent. Therefore, the area ratio of the first region S1 on the anti-thrust side and the area ratio of the first region S1 on the thrust side are in the same range. Furthermore, the area ratios of the second region S2 and the third region S3 on the anti-thrust side and the area ratios of the second region S2 and the third region S3 on the thrust side are in the same range. However, because the load is greater on the thrust side, the area of ​​the high-load region itself is larger on the thrust side. Therefore, the total area value of the first grooves 20 is greater on the thrust side than on the anti-thrust side.

[0028] The oil holes 16 are arranged on the top dead center side of the first region S1 and the second region S2 on the anti-thrust side. In this embodiment, two oil holes 16 are arranged on the top dead center side of the first region S1, and one oil hole 16 is arranged on each of the top dead center sides of the front and rear second regions S2. This allows the lubricating oil discharged from the oil holes 16 to flow directly to the first region S1 or to flow to the first region S1 via the second region S2. This makes it easier to retain the lubricating oil in the first region S1 on the anti-thrust side.

[0029] As described above, the present disclosure provides a piston 1 for an internal combustion engine that can retain lubricating oil in the central portion of the skirt portion 13 on the thrust side while reducing sliding resistance on the anti-thrust side.

[0030] <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0031] (a) In the above embodiment, the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 are each formed by laser processing the skirt portion 13, but the present disclosure is not limited to this. The first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 may be formed, for example, by coating. Examples of coating agents include molybdenum-based resins and diamond-like carbon.

[0032] (b) In the above embodiment, the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 are each an elliptical shape with a maximum longitudinal length of 200 micrometers and a maximum lateral length of approximately 40 micrometers, but the present disclosure is not limited to this. The size and shape of the first groove 20, the second groove 21, the third groove 22, and the fourth groove 23 may be changed as appropriate.

[0033] (c) In the above embodiment, two oil holes 16 are disposed on the top dead center side of the first region S1, but the present disclosure is not limited to this. For example, one oil hole 16 may be disposed in the front-to-rear center portion on the top dead center side of the first region S1. Alternatively, in addition to the two oil holes 16 disposed on the top dead center side of the first region S1 in the above embodiment, one oil hole 16 may be disposed in the front-to-rear center portion, for a total of three oil holes. [Explanation of symbols]

[0034] E: Internal combustion engine, 1: Piston 13: Skirt, 14: Ring groove, 15: Oil ring groove, 16: Oil hole 20: First groove, 21: Second groove, 22: Third groove, 23: Fourth groove, 24: Contact surface S1: 1st area, S2: 2nd area, S3: 3rd area, S4: 4th area

Claims

1. A piston for an internal combustion engine having skirt portions on a thrust side and an anti-thrust side, a plurality of first grooves disposed in a first region located at a center of the skirt portion on the thrust side and the anti-thrust side, the first grooves extending in a direction intersecting a sliding direction of the piston; The first region on the thrust side is wider than the first region on the anti-thrust side. Piston of an internal combustion engine.

2. a plurality of second grooves disposed in a second region located closer to an end of the skirt portion than the first region, the second grooves extending obliquely in a direction intersecting the sliding direction of the piston; Equipped with the second groove on the thrust side extends closer to the top surface of the piston as it moves toward the first region, The second groove on the anti-thrust side extends closer to the top surface side of the piston as it moves away from the first region.

2. The piston of claim 1 for an internal combustion engine.

3. a plurality of third grooves disposed in a third region located closer to an end of the skirt portion than the first region and extending along the sliding direction of the piston; the third region on the anti-thrust side is wider than the third region on the thrust side; 2. The piston of claim 1 for an internal combustion engine.

4. an oil hole, which is arranged on a top dead center side of the first groove on the anti-thrust side in the sliding direction of the piston, and through which oil is supplied; A piston for an internal combustion engine according to any one of claims 1 to 3.

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