JP7364720B2 - Internal combustion engine and piston - Google Patents

Description

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

The piston of an internal combustion engine has a top land. The top land is the portion between the top of the piston and the top ring of the piston (see also Patent Document 1).

The top land of Patent Document 1 includes a first diameter-reduced step portion and a second diameter-reduced step portion. The second diameter-reducing step portion is located above the first diameter-reducing step portion and has a smaller diameter than the first diameter-reducing step portion. The first diameter-reducing step portion and the second diameter-reducing step portion form a step portion. According to Patent Document 1, since the top land has a stepped portion, flame propagates easily to the stepped portion.

Japanese Patent Application Publication No. 2015-81583

A piston with a stepped top land has the following problems. A small gap is left between the inner wall of the cylinder and the stepped top land in the radial direction of the piston. Fuel gas tends to stay in this gap. That is, there is a problem in that it is difficult to both easily propagate the flame to the top land and promote the flow of the fuel gas.

The present invention aims to solve the above-mentioned problems.

A first aspect of the present invention has a top portion, a mounting portion to which a top ring is attached, and a top land portion between the top portion and the mounting portion, which reciprocates inside a cylinder into which fuel gas is introduced. An internal combustion engine including a moving piston, wherein the top land portion includes a first portion separated from an inner side wall of the cylinder by a first distance when the piston is at a top dead center position; a second portion located between the first portion and the side wall when the piston is at the top dead center position; The internal combustion engine is provided with a rib located in a gap between the side wall and the second portion when the engine is at the top dead center position.

A second aspect of the present invention has a top portion, a mounting portion to which a top ring is attached, and a top land portion between the top portion and the mounting portion, and the top land portion reciprocates inside the cylinder into which fuel gas is introduced. The top land portion is a moving piston, and the top land portion includes a first portion having a first radial length, and a second radial length located between the top portion and the first portion and shorter than the first radial length. and a rib extending from the second portion toward an inner side wall of the cylinder.

According to the present invention, it is possible to promote the flow of fuel gas within the cylinder while easily propagating the flame to the top land portion.

FIG. 1 is a schematic configuration diagram of an internal combustion engine according to an embodiment. FIG. 2 is a diagram showing the upper portion of the piston. FIG. 3 is an enlarged view of frame III in FIG. FIG. 4 is a perspective view showing the upper part of the piston. FIG. 5 is a plan view showing the arrangement of two ribs. FIG. 6 is a perspective view illustrating the flow of fuel gas that has entered the gap. FIG. 7 is a diagram showing an internal combustion engine according to modification example 1.

[Embodiment]
FIG. 1 is a schematic configuration diagram of an internal combustion engine 10 according to an embodiment.

Note that in this embodiment, the direction indicated by the arrow DU in FIG. 1 will be described as being upward. Further, the direction indicated by the arrow DD in FIG. 1 will be explained as being downward.

Internal combustion engine 10 is a single-cylinder, four-stroke engine. Internal combustion engine 10 includes a cylinder 12, a piston 14, an intake valve 16, a spark plug 18, and an exhaust valve 20. Cylinder 12 and piston 14 form a combustion chamber 22 .

The cylinder 12 is a cylindrical member. The cylinder 12 has an inner side wall 12s. Further, the cylinder 12 is formed with an intake port 24 and an exhaust port 26.

The intake port 24 is an opening for intake of fuel gas FG into the combustion chamber 22. The fuel gas FG is a mixture of air and fuel such as gasoline. The intake port 24 is connected to an intake pipe 28. The intake port 24 is opened and closed by the intake valve 16.

The arrow DO in FIG. 1 illustrates the intake direction of the fuel gas FG. The arrow DO is parallel to the opening direction of the intake port 24, for example.

The exhaust port 26 is an opening for exhausting exhaust gas EG from the combustion chamber 22. The exhaust port 26 is connected to an exhaust pipe 30. The exhaust port 26 is opened and closed by the exhaust valve 20.

The piston 14 is a substantially cylindrical member disposed inside the cylinder 12 (see also FIG. 4). The piston 14 reciprocates inside the cylinder 12. For purposes of illustration, the piston 14 of this embodiment performs reciprocating motion in the up and down direction. The uppermost position of the reciprocating range of the piston 14 is the top dead center position. Further, the lowest position within the reciprocating range of the piston 14 is the bottom dead center position.

Note that the reciprocating motion of the piston 14 is caused by the intake valve 16, the spark plug 18, and the It is linked to the operation of the exhaust valve 20 and the like.

(1) When the intake valve 16 opens the intake port 24, the fuel gas FG is supplied to the combustion chamber 22. The piston 14 is moved downward from the top dead center position by being pressurized by the fuel gas FG in the combustion chamber 22. The intake valve 16 closes the intake port 24 when the piston 14 is located near the bottom dead center position.

(2) After the intake port 24 is closed, the piston 14 moves upward from the bottom dead center position. The fuel gas FG in the combustion chamber 22 is compressed by the piston 14 moving upward. The spark plug 18 generates a spark within the combustion chamber 22 in conjunction with the piston 14 reaching near the top dead center position.

(3) The compressed fuel gas FG is ignited by the spark generated by the spark plug 18. The ignited fuel gas FG burns to generate a flame and changes into exhaust gas EG. The piston 14 moves downward again in response to combustion of the fuel gas FG. The exhaust valve 20 opens the exhaust port 26 in conjunction with the piston 14 reaching near the bottom dead center position again.

(4) While the exhaust port 26 is open, the piston 14 moves upward again toward the top dead center position. As the piston 14 moves upward, the exhaust gas EG in the combustion chamber 22 is discharged to the outside of the combustion chamber 22 through the exhaust port 26. The exhaust valve 20 closes the exhaust port 26 when the piston 14 is located near the top dead center position.

After (4) above, the cycle of (1) to (4) is repeated again. Note that the internal combustion engine 10 is equipped with an interlocking mechanism that interlocks the operations of the intake valve 16, the spark plug 18, the exhaust valve 20, etc. with the reciprocating motion of the piston 14. This interlocking mechanism includes, for example, a crankshaft, a push rod, a cam, and the like. However, a detailed explanation of the interlocking mechanism will be omitted.

FIG. 2 is a diagram showing the upper portion of the piston 14.

The piston 14 has a top portion 32, a mounting portion 34, a top ring (piston ring) 36, and a top land portion 38.

The attachment portion 34 is a portion of the piston 14 to which the top ring 36 is attached. The attachment portion 34 is, for example, a groove into which the top ring 36 is fitted. In this case, the attachment portion (groove portion) 34 is formed on the outer circumference of the piston 14 along the circumferential direction (CD) of the piston 14 (see also FIG. 4).

The top ring 36 attached to the attachment part 34 prevents the fuel gas FG or the exhaust gas EG from leaking below the top ring 36 inside the cylinder 12 .

Note that a piston ring other than the top ring 36 may be attached to the piston 14 below the top ring 36. Piston rings other than the top ring 36 include a second ring, an oil ring, and the like. However, a detailed explanation of the second ring, oil ring, etc. will be omitted in this embodiment.

The top land portion 38 is a portion of the piston 14 between the top portion 32 and the attachment portion 34 (top ring 36).

A gap G is formed between the top land portion 38 and the inner side wall 12s of the cylinder 12. By forming the gap G, the possibility that the top land portion 38 and the side wall 12s rub against each other due to the reciprocating movement of the piston 14 is reduced.

However, the fuel gas FG may enter the gap G in some cases. If the flame does not propagate to the fuel gas FG that has entered the gap G, the fuel gas FG within the gap G will not burn. As a result, the amount of fuel gas FG that is not combusted despite being supplied to the combustion chamber 22 increases.

Based on this, the top land portion 38 includes a first portion 381 and a second portion 382. The first portion 381 is a portion of the top land portion 38 that has a first diameter D1. The second portion 382 is a portion having a second diameter length D2 that is shorter than the first diameter length D1 (D2<D1). The second portion 382 is located above the first portion 381. The first portion 381 and the second portion 382 are concentric (see center point 14c in FIG. 5).

FIG. 3 is an enlarged view of frame III in FIG.

The gap G has a first region R1 and a second region R2. The first region R1 is a region of the gap G formed by the first portion 381 and the side wall 12s. The second region R2 is a region of the gap G formed by the second portion 382 and the side wall 12s.

In the first region R1, the first portion 381 and the side wall 12s are separated by a first distance L1. In the second region R2, the second portion 382 and the side wall 12s are separated by a second distance L2. The second distance L2 is longer than the first distance L1 (L2>L1).

The wide space between the second portion 382 and the side wall 12s makes it easier for the flame generated by the spark plug 18 in (3) above to propagate into the gap G. As a result, the fuel gas FG within the gap G becomes easier to burn.

However, as the distance between the second portion 382 and the side wall 12s widens, the volume of the gap G may increase. As the volume of the gap G increases, the volume of the combustion chamber 22 increases. As the volume of the combustion chamber 22 increases, the compression ratio of the fuel gas FG compressed in the above-mentioned (2) may deteriorate.

In this respect, according to this embodiment, the first region R1 of the gap G is formed to be relatively narrow. This suppresses an increase in the volume of the gap G. In other words, an increase in the volume of the combustion chamber 22 is suppressed. Therefore, according to the present embodiment, a reduction in the compression ratio of the fuel gas FG is suppressed.

Note that it is preferable that the outer circumferential portion 38s of the top land portion 38 extends in parallel in the vertical direction except for a step portion at the boundary between the first portion 381 and the second portion 382. In this case, it is easier to suppress an increase in the volume of the combustion chamber 22 than when the top land portion 38 has a tapered shape that tapers upward. In other words, it is possible to further suppress a decrease in the compression ratio of the fuel gas FG. Further, since the outer circumferential portion 38s of the top land portion 38 extends in parallel in the vertical direction, the flame can easily propagate downward within the gap G. In other words, the combustion gas that has entered the gap G is more easily combusted.

It is preferable that at least the outer circumferential portion 38s of the second portion 382 extends in parallel in the vertical direction. Thereby, an increase in the volume of the second region R2 is at least suppressed. Further, since the outer circumferential portion 38s of the second portion 382 extends in parallel in the vertical direction, the flame can easily propagate downward at least within the second region R2.

FIG. 4 is a perspective view showing the upper part of the piston 14.

Note that the arrow CD indicates the circumferential direction of the piston 14. Arrow RD indicates the radial direction of the piston 14.

Piston 14 further has two ribs 40. Each of the two ribs 40 is a protrusion located within the second region R2 of the gap G. The two ribs 40 protrude from the second portion 382 in the radial direction of the piston 14 (side wall 12s).

However, at least one of the two ribs 40 may protrude radially from the side wall 12s toward the second portion 382. The rib 40 protruding from the side wall 12s is arranged so as to be located within the second region R2 of the gap G when the piston 14 is at the top dead center position.

The two ribs 40 protrude in the radial direction with a length L3 that is shorter than the second distance L2 (L3<L2). Therefore, each of the two ribs 40 does not interfere with the side wall 12s. Therefore, each of the two ribs 40 does not inhibit the reciprocating movement of the piston 14.

Each of the two ribs 40 illustrated in FIG. 4 does not protrude further than the first portion 381 in the radial direction (L3≦L2−L1). However, at least one of the two ribs 40 may protrude further than the first portion 381 in the radial direction within the range of L3<L2.

Each of the two ribs 40 enters the gap G and collides with the fuel gas FG flowing in the circumferential direction along R2. The fuel gas FG within the gap G collides with the rib 40 and is rolled up upward (see also FIG. 6).

The fuel gas FG moves from within the gap G to a position closer to the spark plug 18 by being rolled up. That is, the two ribs 40 arranged in the gap G flow the fuel gas FG that enters the gap G between (1) and (2) above to a place in the combustion chamber 22 where it is easier to burn. let As a result, in the above (3), combustion of the fuel gas FG in the combustion chamber 22 is promoted.

Preferably, the circumferential width of each of the two ribs 40 tapers upward. For example, each of the two ribs 40 has both sides 40s in the circumferential direction. It is preferable that the side portions 40s are inclined so that the ribs 40 taper upward. Thereby, the fuel gas FG that collided with the rib 40 in the circumferential direction can be more reliably rolled up along both sides 40s of the rib 40 in the circumferential direction. As a result, each of the two ribs 40 can further promote the flow of the fuel gas FG within the cylinder 12, thereby promoting combustion of the fuel gas FG. Note that the both side portions 40s may be curved so that the circumferential width of the rib 40 tapers upward.

FIG. 5 is a plan view showing the arrangement of two ribs.

As described below, the two ribs 40 are arranged so as to sandwich an imaginary straight line LV passing through the center of the cylinder 12 and a predetermined part of the side wall 12s in a vertical plan view inside the cylinder 12. It is preferable that the

The center of the cylinder 12 includes, for example, the center point 14c of the piston 14.

A predetermined portion of the side wall 12s is a portion with which the main flow of the fuel gas FG flowing from the intake port 24 is expected to collide. The predetermined portion of the side wall 12s is predicted based on, for example, experiments.

In order to illustrate a predetermined portion of the side wall 12s in this embodiment, a straight line LDO and a point PDO are shown in FIG.

Straight line LDO is a straight line extending parallel to the intake direction of fuel gas FG (arrow DO in FIG. 1). The fuel gas FG is expected to flow into the combustion chamber 22 roughly along the straight line LDO, for example.

Point PDO is the intersection of straight line LDO and side wall 12s. The main flow of the fuel gas FG is expected to collide with a portion of the side wall 12s, including, for example, the point PDO. The part including this point PDO is, for example, the aforementioned predetermined part.

According to the example shown in FIG. 5, the virtual straight line LV passes through the center point 14c and the point PDO in plan view. One rib 40 is arranged on one side of the virtual straight line LV. Another rib 40 is arranged on the other side of the virtual straight line LV.

FIG. 6 is a perspective view illustrating the flow of the fuel gas FG that has entered the gap G.

After colliding with the side wall 12s, a part of the main flow of the fuel gas FG taken into the combustion chamber 22 flows downward and enters the gap G (arrow A). The fuel gas FG that has entered the gap G flows along the circumferential direction within the gap G (arrow B). The fuel gas FG flowing along the circumferential direction within the gap G collides with at least one of the two ribs 40 arranged to sandwich the virtual straight line LV. As a result, the fuel gas FG that has collided with the rib 40 is rolled up upward as described above (arrow C).

In this way, by arranging the two ribs 40 so as to sandwich the virtual straight line LV, the fuel gas FG flowing along the circumferential direction within the gap G can be more reliably rolled up. As a result, the flow of the fuel gas FG within the cylinder 12 is promoted between (1) and (2) above, so that the combustion of the fuel gas FG in the above (3) can be promoted.

It is more preferable that the two ribs 40 sandwiching the virtual straight line LV are arranged at equal distances (see L4 in FIG. 5) from a predetermined part (point PDO) in the circumferential direction. Thereby, the amount of fuel gas FG rolled up by the two ribs 40 can be made uniform.

In each of the two ribs 40, each of the side portions 40s has an upper end (first end) 40u and a lower end (second end) 40l. The lower end 40l is located below the upper end 40u and contacts the first portion 381. In each of the two ribs 40, it is more preferable that each upper end 40u of both side parts 40s is located between lower ends 40l of both side parts 40s in the circumferential direction (see also FIGS. 4 and 5). Thereby, each of the two ribs 40 can also wind up the fuel gas FG flowing in the gap G on the opposite side of the point PDO with the rib 40 in between. As a result, the flow of the fuel gas FG within the cylinder 12 is further promoted.

As described above, according to the present embodiment, the flame can be easily propagated to the top land portion 38 while the flow of gas within the cylinder 12 can be promoted.

Note that one method for making it easier to burn the fuel gas FG in the gap G is to make the vertical thickness of the top land portion 38 as short as possible.

However, if the thickness of the top land portion 38 is insufficient, the top land portion 38 will be strongly heated by the heat of the combustion chamber 22. The top land portion 38 expands significantly when it is strongly heated. Furthermore, if the thickness of the top land portion 38 is insufficient, the attachment portion 34 will be easily deformed, for example, when the combustion pressure of the fuel gas FG is applied to the top land portion 38 in (3) above. The expansion of the top land portion 38 or the deformation of the attachment portion 34 causes strong friction between the top ring 36 and the attachment portion 34 into which the top ring 36 is fitted. As a result, there is a problem in that the top ring 36 and the attachment portion 34 into which the top ring 36 is fitted wear out more quickly.

In this respect, according to the present embodiment, it is not necessary to design the thickness of the top land portion 38 to be short, at least from the viewpoint of making it easier to burn the fuel gas FG within the gap G. Therefore, according to the present embodiment, it is possible to reduce the amount of fuel gas FG that is not combusted even though it is supplied to the combustion chamber 22, and to suppress the wear rate of the attachment portion 34 at the same time.

Further, as another method for making it easier to burn the fuel gas FG within the gap G, there is a method of narrowing the gap G. However, as described above, the piston 14 thermally expands. Therefore, by narrowing the gap G, there is a greater possibility that the side wall 12s of the cylinder 12 will be bitten by the top land portion 38.

In this respect, according to this embodiment, there is no need to narrow the gap G. Therefore, according to the present embodiment, it is possible to reduce the amount of fuel gas FG that is not combusted even though it is supplied to the combustion chamber 22, and to suppress galling of the top land portion 38.

[Modified example]
Modifications of the above embodiment will be described below. However, descriptions that overlap with the above embodiments will be omitted as much as possible in the following description. Components already described in the above embodiments are given the same reference numerals as in the above embodiments, unless otherwise specified.

(Modification 1)
FIG. 7 is a diagram showing an internal combustion engine 101 (10) according to modification example 1.

Instead of the piston 14, the side wall 12s may have a stepped shape. In this case, the top land portion 38 does not have to be stepped. That is, the top land portion 38 may be formed flat between the lower end (attachment portion 34) of the first portion 381 and the upper end (top portion 32) of the second portion 382.

All the ribs 40 are provided in a portion of the side wall 12s that forms the second region R2 of the gap G together with the second portion 382 when the piston 14 is at the top dead center position.

(Modification 2)
The number of ribs 40 provided in internal combustion engine 10 is not limited to two. The number of ribs 40 provided in the internal combustion engine 10 may be one, or three or more. When three or more ribs 40 are provided in the internal combustion engine 10, the three or more ribs 40 include two ribs 40 that are the same distance (L4) from a predetermined part (PDO) of the side wall 12s in the circumferential direction. It is preferable to include it.

(Modification 3)
The internal combustion engine 10 may be transformed into a multi-cylinder engine including a plurality of cylinders 12. Further, the internal combustion engine 10 may be modified into an engine other than a four-stroke engine. Furthermore, the internal combustion engine 10 may be modified to an engine with three or more valves.

(Combination of multiple variations)
The plurality of modifications described above may be combined as appropriate within the scope of consistency.

[Invention obtained from embodiment]
Inventions that can be understood from the above embodiments and modifications will be described below.

<First invention>
The first invention includes a top portion (32), a mounting portion (34) to which a top ring (36) is attached, and a top land portion (38) between the top portion (32) and the mounting portion (34). An internal combustion engine (10) comprising a piston (14) that reciprocates inside a cylinder (12) into which fuel gas (FG) is introduced, the top land portion (38) being connected to the piston ( 14) is at the top dead center position, the first portion (381) is separated from the inner side wall (12s) of the cylinder (12) by a first distance (L1), and the top portion (32) and the first portion (381), and when the piston (14) is at the top dead center position, the side wall (12s) at a second distance (L2) that is longer than the first distance (L1). a second portion (382) that is separated, and is located in a gap (G) between the side wall (12s) and the second portion (382) when the piston (14) is at the top dead center position. An internal combustion engine (10) is provided with ribs (40).

Thereby, the flame can be easily propagated to the top land portion, and the flow of fuel gas within the cylinder can be promoted.

The top land portion (38) has a step shape in which a first radial length (D1) of the first portion (381) is longer than a second radial length (D2) of the second portion (382), and A rib (40) may extend from said second portion (382) towards said side wall (12s). This allows flame to enter the gap even while the piston reciprocates within the cylinder, thereby further reducing the amount of fuel gas that is supplied to the combustion chamber but does not burn.

The second portion (382) may extend from the top (32) parallel to the direction of the reciprocating movement. Thereby, flame propagates easily in the direction of reciprocating motion within the gap, and increases in the volume of the combustion chamber are suppressed.

The cylinder (12) has an intake port (24) that takes in the fuel gas (FG), and the fuel gas (FG) is supplied from the intake port (24) inside the cylinder (12). The air is drawn in so as to flow toward a predetermined area including a part of the side wall (12s), and the rib (40) connects the part of the side wall (12s) and the center of the cylinder (12) with the air. At least one of them may be disposed on one side and the other side of a virtual straight line (LV) passing through in plan view in the direction of reciprocating motion. Thereby, the fuel gas flowing within the gap can be more reliably rolled up by the ribs.

The plurality of ribs (40) may include two ribs (40) having equal distances from the part of the side wall (12s) in the circumferential direction of the piston (14). Thereby, the amount of fuel gas rolled up by the two ribs can be made uniform.

The rib (40) may have a shape in which the width in the circumferential direction of the piston (14) tapers away from the first portion (381). This makes it easier for fuel gas that collides with the ribs to be blown up.

The rib (40) is inclined or curved in the circumferential direction of the piston (14) so that the width of the rib (40) in the circumferential direction of the piston (14) tapers away from the first portion (381). , each of the two sides (40s) having a first end (40u) and a first portion (381 ), and the first ends (40u) of the both sides (40s) are close to the first ends (40l) of the both sides (40s) in the circumferential direction of the piston (14). It may be located between the two ends (40l). Thereby, the ribs can more reliably wind up fuel gas no matter which direction in the circumferential direction it approaches.

<Second invention>
A second invention includes a top portion (32), a mounting portion (34) to which a top ring (36) is attached, and a top land portion (38) between the top portion (32) and the mounting portion (34). a piston (14) that reciprocates inside a cylinder (12) into which fuel gas (FG) is introduced, the top land portion (38) having a first radial length (D1); a second portion located between the top portion (32) and the first portion (381) and having a second diameter length (D2) shorter than the first diameter length (D1); (382), and is provided with a rib (40) extending from the second portion (382) toward the inner side wall (12s) of the cylinder (12).

Thereby, the flame can be easily propagated to the top land portion, and the flow of fuel gas within the cylinder can be promoted.

DESCRIPTION OF SYMBOLS 10, 101... Internal combustion engine 12... Cylinder 12s... Inner side wall of cylinder 14... Piston 24... Intake port 32... Top part 34... Mounting part (groove part) 36... Top ring 38... Top land part 40... Rib 40l... Lower end (first 2 ends) 40s...Both sides 40u...Upper end (first end) 381...First portion 382...Second portion D1...First diameter length D2...Second diameter length FG...Fuel gas G...Gap L1...First distance L2 ...Second distance LV...Virtual straight line

Claims (6)

It has a top portion (32), a mounting portion (34) to which a top ring (36) is attached, and a top land portion (38) between the top portion (32) and the mounting portion (34). An internal combustion engine (10) comprising a piston (14) that reciprocates inside a cylinder (12) into which (FG) is introduced,
The top land portion (38) is
a first portion (381) that is separated from the inner side wall (12s) of the cylinder (12) by a first distance (L1) when the piston (14) is at the top dead center position;
a second distance (L1) that is located between the top portion (32) and the first portion (381) and is longer than the first distance (L1) when the piston (14) is at the top dead center position; a second portion (382) that separates from the side wall (12s) at L2);
has
A rib (40) is provided that is located in a gap (G) between the side wall (12s) and the second portion (382) when the piston (14) is at the top dead center position ,
The rib (40) has a shape in which the width in the circumferential direction of the piston (14) tapers away from the first portion (381),
The rib (40) is inclined or curved in the circumferential direction of the piston (14) so that the width of the rib (40) in the circumferential direction of the piston (14) tapers away from the first portion (381). having both sides (40s) of
Each of the side portions (40s) has a first end (40u) and a second end (40l) closer to the first portion (381) than the first end (40u) with respect to the direction of the reciprocating motion. , has
The first ends (40u) of the both side portions (40s) are located between the second ends (40l) of the both side portions (40s) in the circumferential direction of the piston (14). 10). An internal combustion engine (10) according to claim 1, comprising:
The top land portion (38) has a step shape in which a first radial length (D1) of the first portion (381) is longer than a second radial length (D2) of the second portion (382),
The rib (40) extends from the second portion (382) toward the side wall (12s) of the internal combustion engine (10). The internal combustion engine (10) according to claim 2,
The second portion (382) of the internal combustion engine (10) extends from the top (32) parallel to the direction of the reciprocating motion. The internal combustion engine (10) according to any one of claims 1 to 3,
The cylinder (12) has an intake port (24) that takes in the fuel gas (FG),
The fuel gas (FG) is sucked into the cylinder (12) so as to flow from the intake port (24) toward a predetermined area including a part of the side wall (12s),
The rib (40) is located on one side of an imaginary straight line (LV) that passes through the part of the side wall (12s) and the center of the cylinder (12) in a plan view in the direction of the reciprocating motion. at least one internal combustion engine (10) disposed on the other side. The internal combustion engine (10) according to claim 4,
An internal combustion engine (10), wherein the plurality of ribs (40) include two ribs (40) that are equal in distance from the part of the side wall (12s) in the circumferential direction of the piston (14). It has a top portion (32), a mounting portion (34) to which a top ring (36) is attached, and a top land portion (38) between the top portion (32) and the mounting portion (34). A piston (14) that reciprocates inside a cylinder (12) into which (FG) is introduced,
The top land portion (38) is
a first portion (381) having a first diameter length (D1);
a second portion (382) located between the top portion (32) and the first portion (381) and having a second radial length (D2) shorter than the first radial length (D1);
has
a rib (40) extending from the second portion (382) toward the inner side wall (12s) of the cylinder (12) ;
The rib (40) has a shape in which the width in the circumferential direction of the piston (14) tapers away from the first portion (381),
The rib (40) is inclined or curved in the circumferential direction of the piston (14) so that the width of the rib (40) in the circumferential direction of the piston (14) tapers away from the first portion (381). having both sides (40s) of
Each of the side portions (40s) has a first end (40u) and a second end (40l) closer to the first portion (381) than the first end (40u) with respect to the direction of the reciprocating motion. , has
The first ends (40u) of the both sides (40s) are located between the second ends (40l) of the both sides (40s) in the circumferential direction of the piston (14). ).

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