JP2572365Y2 - Piston for internal combustion engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION This invention relates to a piston for an internal combustion engine of an automobile or the like.

[0002]

2. Description of the Related Art Conventionally, there has been a piston for an internal combustion engine described in, for example, Japanese Utility Model Laid-Open Publication No. 62-145962. In this internal combustion engine piston, as shown in FIG.
A top ring 13 is formed by engraving a top ring groove 12 on the outer peripheral surface of a crown portion 11 constituting the piston body 10, and the top land 13 has at least one concave groove which is enlarged and opened on the outer peripheral side. 14 are provided around. The unburned gas flowing between the top land 13 and the cylinder bore 15 during operation of the engine is accumulated in the concave groove 14 so as to prevent the unburned gas from flowing to the top ring groove 12 as much as possible.

[0003]

An invention is, however, the in the conventional piston for an internal combustion engine, grooves 14 are formed in isosceles trapezoid cross-section, the side 14 _1, 1 of the concave groove 14
4 ₂ and the edge portion 16 to the connecting portion of the top land 13 is formed. Therefore, during engine operation, the edge portion 1
6 becomes a heat spot, and the heat makes the top land 1
Unburned gas existing between the cylinder bore 3 and the cylinder bore 15 or in the concave groove 14 is spontaneously ignited and knocking occurs. Edge portion 1 that causes damage to top land 13 due to this knocking
6, causing the defect that the concave groove 14 does not function.

The present invention has been made to solve the above-mentioned problem, and has as its object to provide a piston for an internal combustion engine that can reliably store unburned gas without forming a heat spot.

[0005]

In order to achieve the above object, the present invention defines a top land by engraving a top ring groove on the outer peripheral surface of a crown portion of a piston body. In a piston for an internal combustion engine provided with a concave groove which is enlarged and opened on the outer peripheral side, a side portion of the concave groove on the combustion chamber side is formed so as to be more inclined than a side portion on the top ring groove side, while the concave groove is formed. A convex arc portion is formed in a continuous portion between the side portion and the top land.

[0006]

According to the above construction, since the edge portion serving as a heat spot is eliminated, the unburned gas flowing between the top land and the cylinder bore does not ignite.

The unburned gas smoothly enters the groove along the combustion chamber side of the groove and accumulates, and the amount of unburned gas flowing to the top ring groove is reduced.

Even if knocking occurs, the side of the concave groove on the side of the top ring groove rises with a smaller inclination than the side of the combustion chamber, so that the generated combustion gas flows into the top land and the cylinder bore. After entering into the groove along the side of the groove on the combustion chamber side, a swirling flow is formed that returns to the combustion chamber side, and the combustion gas hardly flows to the top ring groove side.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a front view showing a piston for an internal combustion engine, FIG. 1B is an enlarged sectional view showing a top land of the piston in FIG. 1A, and FIG.

An annular top ring groove 2 is formed in the outer peripheral portion of the crown portion 1 constituting the piston main body, and thereby a top land 3 is defined.

At least one recessed groove 4 is formed at least on the thrust side of the top land 3 so as to open toward the outer periphery.
(One in the embodiment) is provided around. The concave groove 4 is substantially V-shaped with a depth d and an opening width of W ₁ + W ₂ ,
Is formed to a not-shown combustion chamber side portion 4 ₁ and the top ring groove 2 side portion 4 ₂ Togatotsu arcuate bottom 4 ₃ are formed on the concave arcuate, the side through the bottom portion 4 ₃ part ₄ 1, _{4 2} are smoothly continuously provided. Further, convex arcuate portion 4 ₄ is formed on the connecting portion of the side 4 ₁ and the top land 3 of the combustion chamber side, the connecting portion of the side 4 ₂ and the top lands 3 of the top ring groove 2 side convex arcuate portion 4 ₅ is formed on. Side 4 ₁ of the combustion chamber side is formed to be inclined larger than the sides 4 ₂ of the top ring groove 2 side.

More specifically, the dimensions of each part of the concave groove 4 are set as follows.

[0014] the radius of curvature _{R 1} of the side _{4 1} of the combustion chamber side is 1.
0 or more and 2.5 or less, the radius of curvature _{R 2} of the side _{4 2} of the top ring groove 2 side 1.5 or 3.0 or less, the radius of curvature _R 1, _{R 2} is a _R 2 _{<R 1} cage, convex arcuate portion _{4 4}
Is formed with a radius of curvature R ₁ on the side 4 ₁ and concentric combustion chamber side, convex arcuate portion 4 ₅ is formed by a radius of curvature R ₂ the sides 4 ₂ concentric with the top ring groove 2 side. Further, the bottom _{4 3}
The radius of curvature _{R 3} of 0.7 or less 0.3 or more, the depth d from the top land 3 deepest site of the bottom _{4 3} has a 1.4 or less 0.7 or more. Furthermore, 2.0 or less in the opening width is 1.0 or more, the bottom 4 size W ₁ of the combustion chamber side when the bisecting the opening width at the center of curvature position of the ₃ dimensions W ₂ plus 0 top ring groove 2 side .1.

[0015] Incidentally, in this embodiment, by forming the sides 4 ₁ of the combustion chamber side of the groove 4 in a convex arc shape, this and the top land 3 the convex arcuate portion 4 ₄ identical curvature radii concentrically of one to be formed in the connecting portion, to form the sides 4 ₂ of the top ring groove 2 side in a convex arc shape, this same curvature concentric radius of convex arcuate portion 4
₅ was formed on the connecting portion between the top land 3, to form the sides 4 ₁ and the top ring groove 2 side portion 4 ₂ of the combustion chamber side in a straight line, which so as to connect the top land 3 It goes without saying that the convex arc-shaped portions 4 ₄ , 4 ₅ may be formed in a continuous portion between the top grooves 3 and 4 ₁ , 4 ₂ of the concave groove 4.

In the above configuration, during operation of the engine, as shown in FIG. 2, the top land 3 of the piston main body that slides in the cylinder bore 5 by receiving the combustion gas pressure on the crown surface 1a of the crown portion 1 and the cylinder bore 5 are connected to each other. Even if the unburned gas flows in between, the unburned gas flowing between the top land 3 and the cylinder bore 5 will not spontaneously ignite because the concave groove 4 has no edge portion serving as a heat spot.

The unburned gas is supplied to the side 4 of the groove 4 on the combustion chamber side.
₁ smoothly enters and accumulates in the concave groove 4 and the amount flowing toward the top ring groove 2 decreases.

Even in the case of an engine or the like having a high output and a high compression ratio, knocking occurs even when unburned gas is spontaneously ignited between the top land 3 and the cylinder bore 5 or in the concave groove 4 to cause knocking. in generated combustion gas is entering the concave groove 4 along the sides 4 ₁ of the combustion chamber side of the groove 4 between the top land 3 and the cylinder bore 5, the top ring groove 2 side of the groove 4 since side 4 ₂ is up standing inclined less than the side 4 ₁ of the combustion chamber side, because the flow of the combustion gas as shown by arrow in FIG. 3 the swirling flow back to the combustion chamber side, It becomes difficult for the combustion gas to flow to the top ring groove 2 side.

[0019]

[Effect of the Invention] As described above, this invention defines a top land by engraving a top ring groove on the outer peripheral surface of the crown portion of the piston body, and forms a concave groove on the top land that expands outward on the outer peripheral side. In the peripherally provided piston for an internal combustion engine, a side portion of the groove on the combustion chamber side is formed so as to be more inclined than a side portion on the side of the top ring groove, and a side portion of the groove and the top land are continuously provided. Since the convex arc portion is formed in the portion and the edge portion serving as a heat spot is eliminated, the unburned gas flowing between the top land and the cylinder bore can be reliably prevented from spontaneously igniting. Further, the unburned gas flowing between the top land and the cylinder bore is guided by the side of the concave groove on the combustion chamber side and accumulated in the concave groove, so that the amount of unburned gas flowing to the top ring groove side can be reduced. . Further, even if knocking occurs, the side of the concave groove on the top ring groove side rises with a smaller inclination than the side on the combustion chamber side, so that the generated combustion gas is discharged to the top land. After entering the groove along the side of the combustion chamber side of the groove from between the and the cylinder bore, a swirl flow is formed to return to the combustion chamber side, and the combustion gas flows to the top ring groove side. It can be difficult. Therefore, the occurrence of knocking can be prevented, and the concave groove can be made to function sufficiently, thereby eliminating the possibility of the top land being broken, seizing of the top ring, and abrasion of the top ring groove.

[Brief description of the drawings]

FIG. 1 is a front view showing an internal combustion engine piston according to an embodiment of the present invention. (2) It is an expanded sectional view showing the top land in the piston of (1).

FIG. 2 is an operation explanatory view of a piston shown in FIG. 1;

FIG. 3 is a sectional view corresponding to FIG. 1 (2) showing a top land in a conventional piston for an internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Crown part 2 Top ring groove 3 Top land 4 Depression groove 4 ₁ Side part on the combustion chamber side 4 ₂ Side part on the top ring groove side 4 ₃ Bottom part 4 ₄ , 4 ₅ Convex arc-shaped part

Claims (1)

(57) [Scope of request for utility model registration] 1. A piston for an internal combustion engine in which a top land is defined by engraving a top ring groove on an outer peripheral surface of a crown portion of a piston body, and a concave groove is formed on the top land so as to expand toward the outer peripheral side. In the above, the side portion of the groove on the combustion chamber side is formed so as to be more inclined than the side portion of the top ring groove side, while a convex arc portion is formed on a continuous portion between the side portion of the groove and the top land. A piston for an internal combustion engine, characterized in that: