JP2001214804A - Piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston capable of generating a flow of conbustion gas for lowering oil collected in a land, and having a large capacity for collecting the oil in a limited land. SOLUTION: In a second land 9 under a top ring groove 14, annular grooves which have a larger diameter with closing to an oil ring are formed so as to make the land in a step shape. By these annular grooves, a flow of conbustion gas for lowering oil collected in the second land 9 can be generated in the same way as a wedge annular groove, and a large capacity for collecting the oil can be ensured in the limited second land 9. Consequently, a piston 6 capable of suppressing friction at low degree and reducing the amount of oil consumed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine, and more particularly to a piston having an improved land under a top ring groove.

[0002]

2. Description of the Related Art A piston of an internal combustion engine is provided with two pressure rings, a top ring and a second ring, on its outer peripheral surface, and an oil ring is mounted below the pressure ring. It is airtight and prevents oil from leaking into the combustion chamber. In recent years, in order to reduce the size of the engine or reduce the friction loss, the number of pistons having a two-ring configuration in which one pressure ring and one oil ring form a ring has been increasing.

Generally, in a piston having a two-ring configuration, it is difficult to suppress the rise of oil into the combustion chamber (oil consumption) and the blow-by of combustion gas (blow-by gas). Further, in order to reduce friction, the tension of each ring must be reduced, and it becomes more severe to reduce oil consumption. A high-top ring piston as shown in FIG. 8 is known as a piston capable of reducing oil consumption even in such a two-ring type piston (utility model registration No. 25797).
No. 40). This high top ring piston
By devising the shape of the second land 2 of the piston 1, an annular groove 4 having a substantially wedge-shaped cross section is formed near the top ring groove 3, increasing in size in the radial direction and decreasing in size as going downward. Oil flowing upward along the piston 1 accumulates in the annular groove 4. That is, the oil goes to the groove bottom along the linear inclination of the annular groove 4 and is blocked from going to the groove bottom wall 5 in the radial direction, so that it is difficult to move upward. On the other hand, when the combustion gas leaking from the pressure ring blows through from above, the oil stored in the second land 2 falls downward by the flow of the combustion gas along the linearly inclined wall, and returns to the oil pan.

[0004]

However, in the conventional high top ring piston, the annular groove 4 having a wedge-shaped cross section is formed in the limited space of the second land 2, so that the space in which the oil accumulates is reduced. There was a limit to obtaining a sufficiently large size, and the rise of oil could not be sufficiently prevented. If the wedge-shaped cut is increased in order to increase the oil storage amount, a problem occurs in that the strength of the piston below the top ring groove 3 becomes insufficient.

Accordingly, the present invention provides a piston that can generate a flow of combustion gas that can lower oil stored in a land, and that can increase the volume of oil stored in a limited land. The purpose is to provide.

[0006]

Hereinafter, the present invention will be described. In order to solve the above-mentioned problems, the present inventor has conducted intensive research on how to obtain a shape effect substantially similar to that of a conventional wedge-shaped annular groove, and how to secure a space for storing oil in a limited land. Stacked. As a result, by forming an annular groove whose diameter becomes larger as approaching the oil ring so as to be stepwise on the land, the same shape effect as the conventional wedge-shaped annular groove can be obtained, and the volume for storing oil is increased. I learned that it can be increased.

That is, according to the present invention, there is provided a piston according to the present invention, wherein an annular groove whose diameter increases as approaching the oil ring is formed in the land under the top ring groove so that the land has a stepped shape. Solved the problem. Here, the land is a gap (second land) between the piston and the cylinder between the top ring and the oil ring in the case of a two-piece ring, and the top ring in the case of a three-piece ring. A gap (second land) between the piston and the cylinder between the second ring and / or a gap (third land) between the piston and the cylinder between the second ring and the oil ring.

According to the present invention, it is possible to generate a flow of combustion gas capable of lowering the oil stored in the land downward substantially in the same manner as the wedge-shaped annular groove, and to store the oil in a limited land. The volume can be increased. As a result, a piston that can achieve both low friction and reduced oil consumption can be obtained.

Further, the invention is characterized in that a cross section of the outer peripheral surface of the land is substantially straight and substantially parallel to the center line of the piston.

According to the present invention, a large amount of oil can be stored in the land.

Further, the present invention is characterized in that a cross section of the side surface and the outer peripheral surface of the land is connected by a curved line.

According to the present invention, the flow of the combustion gas in the land can be made smooth.

Further, the present invention is characterized in that a total of two rings including one pressure ring and one oil ring are mounted on the piston.

The present invention can be suitably used for such a two-piece ring in which combustion gas is easily blown through.

[0015]

1 and 2 show a first embodiment of the present invention.
3 shows a piston 6 in the embodiment. This piston 6
, A total of two rings including a top ring 7 as one pressure ring and one oil ring 10 are mounted. An annular groove is formed in a gap 9 (hereinafter referred to as a second land 9) between the piston 6 between the top ring 7 and the oil ring 10 and the cylinder 8 so that the piston 6 has a stepped shape. The diameter of this annular groove increases as it approaches the oil ring 10. Two or more steps, in this embodiment, two steps, are formed in the piston 6 by the annular groove. The cross-sectional shape of the outer peripheral surfaces 11a, 11b, 11c of the piston 6 forming the stairs is straight and substantially parallel to the center line of the piston 6. On the other hand, the cross-sectional shape of the side surfaces 12a and 12b of the piston 6 forming the stairs is
The straight line is substantially orthogonal to the center line of the piston 6. Then, the side surfaces 12a, 12b and the outer peripheral surfaces 11a, 11b, 11c
Has a larger diameter toward the lower side of the piston 6. That is, the outer peripheral surface has the minimum diameter at the portion 11c in the figure, has the next larger diameter at 11b, and has a larger diameter at 11a. The diameter of 11a is equal to or less than the diameter of the portion 13 immediately below the top ring groove. In the portion 13 immediately below the top ring groove, the outer diameter of the piston 6 is the largest, and the cross section of the outer peripheral surface is parallel to the center line of the piston 6. The outer peripheral surfaces 11a, 11b, 11
The corner where c intersects the side surfaces 12a and 12b may be chamfered as needed.

FIG. 3 compares the volume of the second land 9 between the case where the step-shaped annular groove is formed and the case where the wedge-shaped annular groove 15 is formed. Wedge-shaped annular groove 15
The dimension increases in the radial direction near the top ring groove 14, and the dimension decreases as it goes downward. The inclination of the step-shaped annular groove substantially coincides with the inclination of the wedge-shaped annular groove 15. Then, the outer peripheral surface 11b and the side surface 12b forming the stairs
Is substantially located on the wedge-shaped annular groove 15.

As shown in FIG. 3, when the annular groove is formed in a step shape, the second land 9 is formed in comparison with the case where the annular groove is formed in a wedge shape.
Can be enlarged only by the portion of S in the figure,
The second land 9 can have a volume. As a result, it is possible to increase the volume of storing the oil in the limited second land 9. In addition, in a manner similar to the wedge-shaped annular groove 15, a flow of combustion gas that can lower the oil stored in the second land 9 can be generated. Can be returned to bread. Also, since the pressure fluctuation in the second land 9 is reduced, the top ring 7
And the behavior of the top ring 7 is improved. As a result, a piston that can achieve both reduced oil consumption and low friction is obtained. Further, the present invention is effective even when the abutment of the top ring 7 is narrowed to reduce blow-by gas. In this case, reduction of oil consumption, reduction of friction and reduction of blow-by gas are at the same time.

FIG. 4 shows a comparison of oil consumption between the case where the annular groove is formed in a wedge shape (wedge type) and the case where the annular groove is formed in a step shape (step shape). As shown in this figure, the wedge-shaped oil consumption is 9.8 in the NLD with 7,500 revolutions.
g / h, 13.3 g / h at 7500 rpm full load, whereas the stepped oil consumption is 9.5 g / h at 7500 rpm NLD and 12.0 g / h at 7500 rpm full load. Becomes NL for staircase shape
D, The oil consumption is reduced in the case of full load. Oil consumption is closely related to the amount of oil stored in Second Land. It can be seen that the step shape having a large oil storage amount reduces the oil consumption and improves the sealing performance.

FIG. 5 shows a piston 16 according to a second embodiment of the present invention. The second land 17 of this piston 16
Unlike the piston of the first embodiment, an annular groove is formed so that the piston 16 has a three-step shape. The diameter of this annular groove increases as it approaches the oil ring. The cross-sectional shape of the outer peripheral surfaces 18a, 18b, 18c, 18d of the piston 16 forming the steps is straight and substantially parallel to the center line of the piston 16. On the other hand, the side surfaces 19a, 19b, 19c of the piston 16 forming the stairs
Has a straight line and is substantially perpendicular to the center line of the piston.
In addition, immediately below the top ring groove 20, the outer diameter of the piston 16 is the largest, and the cross section of the outer peripheral surface is parallel to the center line of the piston. The inclination of the step-shaped annular groove substantially coincides with the inclination of the wedge-shaped annular groove.

FIG. 6 shows a piston 22 according to a third embodiment of the present invention. The piston 22 of this embodiment includes:
The configuration is substantially the same as that of the piston 6 of the first embodiment, except that the cross-sectional shapes of the side surfaces 23a and 23b and the outer peripheral surfaces 24a, 24b and 24c of the piston forming the steps are connected by an arc-shaped curve 26. This point is different from the piston of the first embodiment. That is, the outer peripheral surfaces 24a, 24b,
The corner where 24c intersects the side surfaces 23a and 23b is cut,
Or it is fleshed out and formed in an arc shape. Thus, the side surfaces 23a, 23b and the outer peripheral surfaces 24a, 24b,
By connecting the cross-sectional shapes 24c with the arc-shaped curve 26, the flow of the combustion gas can be made smooth without causing useless vortices in the flow of the combustion gas leaking from the combustion chamber.

FIG. 7 shows a piston 27 according to a fourth embodiment of the present invention. The piston 27 of this embodiment also
The configuration is substantially the same as that of the piston 6 of the first embodiment, except that the side surface 29a and the outer peripheral surface 28 at the first stage of the stairs are used.
The point that the cross-sectional shape of b is connected by a gentle arc-shaped curve 30 is different from the piston 6 of the first embodiment. In other words, the corner where the outer peripheral surface 28b and the side surface 29a of the first stage intersect is fleshed out over a wide range and is formed in a gentle arc shape. Piston 27 of this embodiment
However, the flow of the leak gas can be made smooth.

In each of the embodiments described above, the piston having a two-ring configuration has been described. However, the present invention is not limited to the two-ring configuration, but includes two pressure rings and one oil ring. The present invention can also be applied to a three-ring configuration, and has substantially the same operation and effect as the above-described two-ring ring piston.

[0023]

As described above, according to the present invention,
In the land under the top ring groove, an annular groove whose diameter increases as approaching the oil ring is formed so that the land has a step-like shape, so that the oil stored in the land is substantially similar to the wedge-shaped annular groove. A flow of combustion gas can be generated that can be lowered downward, and a space for storing oil in a limited land can be increased. As a result, a piston that can achieve both low friction and reduced oil consumption can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a piston according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a piston in the second land of FIG. 1;

FIG. 3 is a diagram showing a comparison between a wedge-shaped annular groove and a step-shaped annular groove.

FIG. 4 is a graph comparing oil consumption when the annular groove is formed in a wedge shape and when the annular groove is formed in a step shape.

FIG. 5 is a sectional view showing a piston according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing a piston according to a third embodiment of the present invention.

FIG. 7 is a sectional view showing a piston according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view showing a conventional piston.

[Explanation of symbols]

6, 16, 22, 27 Piston 7 Top ring (pressure ring) 9, 17 Second land (land) 10 Oil ring 14, 20 Top ring groove 11a, 11b, 11c, 18a, 18b, 18c, 1
8d, 24a, 24b, 24c, 28a, 28b, 28
c Outer peripheral surface 12a, 12b, 19a, 19b, 19c, 23a, 2
3b, 29a, 29b Side 26, 30 Curve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kasahara 300 Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. (72) Yukio Tateishi 2-6-1 Honcho Nishi, Yono-shi, Saitama Japan Piston Ring Co., Ltd. Inside the Yono Plant (72) Inventor Sakyo 5-6-1 Nishi, Honmachi, Yono-shi, Saitama Japan Piston Ring Co., Ltd. Inside the Yono Plant F-term (reference) 3J044 AA12 AA14 BC06 CA14 DA09

Claims (4)

[Claims] 1. A piston, wherein an annular groove whose diameter increases as approaching an oil ring is formed in a land below the top ring groove so that the land has a stepped shape. 2. A cross section of an outer peripheral surface of the step-like land,
The piston according to claim 1, wherein the piston is substantially straight and substantially parallel to a center line of the piston. 3. The piston according to claim 1, wherein an outer peripheral surface and a cross section of a side surface of the step-like land are connected by a curved line. 4. The piston according to claim 1, wherein a total of two rings including one pressure ring and one oil ring are mounted on the piston.