JPS5857626B2 - Piston for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for an internal combustion engine that has an oval or elliptical planar shape.

Generally, an oval or elliptical cylinder hole is formed in the cylinder block, a piston having the same planar shape is slid into the cylinder hole, and a pin boss part integrally hung on the piston head is inserted in the longitudinal direction of the head. Internal combustion engines of the type in which a piston pin is supported have been known for some time, and this engine has the advantage of increasing the displacement per cylinder without increasing the size of the engine.

By the way, if the skirt portion of the piston used in this type of internal combustion engine is formed to have the same shape as the head portion, that is, to have an oval or elliptical cross section, the contact area between the skirt portion and the cylinder hole will inevitably increase. Frictional resistance increases when the piston slides, the skirt itself inevitably becomes larger, and reinforcement with ribs is required to maintain its rigidity, which increases the weight of the piston. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a piston which can eliminate the above-mentioned disadvantages and can effectively restrict the so-called oscillation movement around the piston pin.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. First, the structure of the piston, which is indicated by the symbol P as a whole in FIGS. 1 to 4, will be explained.
has both end surfaces 1, 1 formed as symmetrical arcuate surfaces, and both side surfaces 2, 2 formed as flat surfaces that smoothly connect with said both end surfaces 1, 1, and its planar shape is oval-shaped. ing.

Further, the both side surfaces 2, 2 may be formed into curved surfaces that smoothly connect with the both end surfaces 1, 1 made of circular arc surfaces,
In this case, the shape of the head portion H becomes an ellipse.

A piston ring groove 3 and an oil ring groove 4 are formed on the outer circumferential surface of the head portion H, and a piston ring and an oil ring are fitted into these grooves 3 and 4, respectively, as usual.

left and right skirt portions S consisting of substantially arcuate surfaces having the same radius as the circular arc surfaces from both end surfaces 1, 1 consisting of circular arc surfaces of the head portion H;
The inner sides of these skirt parts S, S, which face each other, are integrally hung from the head part H on the inner side of the downward extension line of both side surfaces 2, 2 of the head part H. The left and right skirts are connected together by a connecting outer wall 5゜5.
The parts S and S are reinforced.

The skirt portions S and S are generally circular 2 in plan view.
It has a structure in which two pistons are connected by connecting outer walls 5, 5.

Two pairs of pin bosses 6.6' and 7,7' are spaced from the inner surface of the clay wall of the head portion H in the longitudinal direction of the piston P.
are integrally installed vertically, and these pin bosses 6, 6' and 7
, 7' supports one piston pin 8 in the longitudinal direction of the piston P, and the skirt portions S, S have flat notches 9 at portions corresponding to both end surfaces of the piston pin 8.

Of the pin bosses 6, 6' and 7, 7' forming each village, the pin boss 6' located on the inside, ? ' are connected and reinforced by an intermediate connecting wall 10, and roughly between the pin bosses 6, 6', 7, 7' of each village and the earthen wall of the head part H are reinforced by reinforcing walls 11, 11', respectively. There is.

In FIGS. 1 and 2, 12 is a snap ring for preventing the piston pin 8 from coming off, and 13 is an oil hole.

FIG. 5 shows a vertical cross-sectional view of the piston P constructed as described above installed in the engine body. The piston P is slidably fitted therein, and a small end 17 of a connecting rod 16 is connected to the piston pin 8 between the pin bosses 6, 6' and 7, 7' of each village. Its large end 18 is connected to a crank pin 20 of a crankshaft 19 in the same way as in a normal engine.

Incidentally, each crank pin 20 is connected to a large end 18' of another connecting rod 16', and this rod 16'
Although not shown, the small end of the cylinder block 14 is connected to a piston of another cylinder block arranged in a V-shape in parallel with the cylinder block 14.

In FIG. 5, 21 is a combustion chamber, and 22 is a spark plug.

In Fig. 5, the spark plug 2 is connected like a normal internal combustion engine.
When the compressed air-fuel mixture in the combustion chamber 21 is ignited and combusted by the electric spark 2, the piston P is lowered by the explosive energy and the engine is operated. Since only the semicircular arc portions of the skirt portions S and S contact the inner surface of the cylinder hole 15, the contact area between them is reduced as much as possible, and the frictional resistance generated therebetween can be reduced.

In addition, the left and right skirt parts S, S themselves form a well-curved surface and have a certain degree of rigidity. 5
Since the left and right skirt parts S and S themselves have the necessary and sufficient strength without being reinforced with ribs, etc., the skirt parts S and S have elasticity in the diametrical direction. Since this can be expected to some extent, the skirt portions S, S can be brought into good contact with the inner surface of the cylinder hole.

As described above, according to the present invention, the planar shape is formed into an oval or elliptical shape by having both end faces made of circular arc surfaces and both side faces made of flat or curved surfaces that are smoothly connected to both end faces. a head portion; a pin boss portion that is integrally hung from the head portion and supports a piston pin in the longitudinal direction of the head portion; a connecting outer wall that integrally connects the opposing inner sides of the left and right skirt portions inwardly from a downward extension line of both side surfaces of the head portion; Since the piston is constructed, the skirt part as a whole has a structure in which two pistons with a circular planar shape are integrally connected by a connecting outer wall, and the overall strength is extremely high, and the skirt part is specially reinforced with reinforcing ribs etc. This is advantageous in terms of reducing the weight of the piston.

Moreover, since there is no skirt portion below both side surfaces of the head portion that are flat or curved, that is, both side surfaces along the length direction of the piston pin, the skirt portion may have the same shape as the head portion, that is, an oval cross section, or Compared to the elliptical shape, the contact area of the skirt part with the inner surface of the cylinder hole can be significantly reduced, significantly reducing friction loss when the piston slides, and furthermore, it can further reduce the weight of the piston. can contribute.

Generally speaking, pistons tend to oscillate around the piston pin during reciprocating motion, but in the present invention, the left and right skirts, which are made of highly arcuate surfaces, have a tendency to swing along the diameter line perpendicular to the length direction of the piston pin. The above moment can be stably received or stopped at or near the moment, and the piston can be smoothly reciprocated without swinging, and the left and right skirts can be moved more or less in the diametrical direction. Since they exhibit elasticity, these skirt portions can be brought into good contact with the inner surface of the cylinder hole.

[Brief explanation of drawings]

Fig. 1 is a partially longitudinal side view of the piston of the present invention, Fig. 2 is a cross-sectional bottom view taken along the line ■-■ in Fig. 1, Fig. 3 is a cross-sectional view taken along the line I--I of Fig. 1, and Fig. 4 is a piston of the present invention. FIG. 1 is a partially cutaway end view taken in the direction of arrow Z in FIG. H...Head part, S...Skirt part,
1...End face, 2...Side surface, 5...
・Connected outer wall.

Claims (1)

[Claims] 1. A head portion having an oval or elliptical planar shape, having both end surfaces made of circular arc surfaces, and both side surfaces made of flat or curved surfaces that are smoothly connected to both end surfaces; a pin boss part that is integrally hung down from the head part and supports the piston pin in the longitudinal direction of the head part; and left and right skirt parts that hang down from both end faces of the head part and are made of superior arc surfaces having the same radius as the arc surfaces. A piston for an internal combustion engine, comprising at least: a connecting outer wall that integrally connects the opposing inner sides of the left and right skirt portions inwardly from the downward extension lines of both side surfaces of the head portion.