JPS5857625B2 - 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 that is integrally hung from the head of the piston is attached to the longitudinal axis of the head. Internal combustion engines of the type in which a piston pin is supported in the axial direction have been known for some time, and this type has the advantage that the displacement per cylinder can be increased 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. There are disadvantages such as increased frictional resistance when the piston slides, and the skirt itself inevitably becomes larger, resulting in an increase in the weight of the piston.

The present invention provides a piston which can eliminate the above-mentioned disadvantages, and which can effectively restrict the so-called oscillation movement around the piston pin while improving the surface contact between the piston skirt part and the cylinder part. The purpose is to

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. A piston, generally designated by the symbol P, is composed of a head portion H, a skirt portion S1, a pin boss portion B, and an outer wall portion W.

Their structures will be explained in detail below.

The head portion H has both end faces 1, 1 formed into symmetrical arcuate surfaces, and both end faces 2, 2 thereof are formed as symmetrical arc surfaces.
It is formed on a flat surface that smoothly connects with the other side, and its planar shape is oval-shaped.

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.

In the piston of the present invention, the skirt portion S connected to the head portion H exists only in a part thereof, that is, both side surfaces 2 of the head portion H that are flat or curved.
, skirt pieces 5 each extending downward from 2 in a gate shape,
5, both ends and the center of both sides are missing.

Therefore, the head portion H of the inner surface of the oval or elliptical cylinder hole of the piston P is in sliding contact with the cylinder wall 6 on its entire surface, but the skirt portion S has only the skirt portions I and pieces 5 on both sides of the cylinder wall 6. sliding into contact with.

The pin boss part B consists of two pairs of pin bosses 7.7 and 8,8 which are vertically symmetrically hung from the head part 1 at intervals in the longitudinal direction.
．． One piston pin 9 is supported by 7, 8, and 8.

The pin bosses 7, 7 and 8, 8 of each village are located inward from both end surfaces 1, 1 of the head portion H, and these pin bosses 7.
The small ends of connecting rods 10, 10 are connected to the piston pin 9 between 7 and 8, 8, respectively.

The outer wall W extends integrally from the bisbons 7.7 and 8.8 of each village to form a closed frame shape in cross section, and extends below the bisbons 7.7 and 8,8 of each village. It surrounds the connecting rod 10, and both sides thereof constitute the skirt portion S.

The two closed frame-shaped outer wall parts W, W are integrally connected by a connecting wall 11 extending from the head part H.

When the piston P configured as described above is fitted into an oval-shaped or oval-shaped cylinder Cy hole having the same planar shape as this, its head portion H will come into sliding contact with the cylinder wall 6 of the cylinder Cy hole. The skirt portion S is in sliding contact with the skirt pieces 5, 5 which constitute the skirt portion S, and slides back and forth within the cylinder Cy hole under the explosion pressure within the combustion chamber.

By the way, in general, the skirt portion of the piston is used to guide the piston correctly into the cylinder hole when the piston reciprocates, to prevent the piston from swinging around the piston pin, and to prevent explosions caused by the piston. The main role of the skirt is to transmit pressure or inertia force as effectively as possible to the connecting rod through the piston pin. The skirt part plays its original role by absorbing and stopping the side pressure, that is, the moment around the piston pin when the piston is about to oscillate, whereas both end surfaces on the side perpendicular to the axis of the piston pin are relatively skirt-like. Therefore, in the present invention, by providing the skirt portion S, that is, the skirt piece 5 only on both sides along the axis of the pinton pin 9, the intended function of the skirt portion S is not impaired. The weight of the skirt portion S is reduced as much as possible without causing any discomfort, and the contact area of the skirt portion S, that is, the skirt piece 5, with the cylinder wall 6 is reduced to reduce the frictional resistance between the piston P and the cylinder wall 6. In other words, viscous resistance can be reduced.

In addition, the screw P has great strength by providing an outer wall portion W that is vertically disposed from the head portion H inwardly from both longitudinal end surfaces 1, 1 of the head portion H,
It is less likely to be deformed even when subjected to explosive force, and the explosive force or inertial force acting on the piston P can be effectively transmitted to the connecting rod 10.

By forming a small gap between the connecting wall 11 and the piston pin 9, lubricating oil flows into this small gap and the pin boss 7
．． 8 and the piston pin 9 can be well lubricated.

As described above, according to the present invention, a head having an oval or elliptical planar shape has both end faces made of circular arc surfaces and both side faces made of flat or curved surfaces that are smoothly connected to the both end faces. 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; A pin boss part that is integrally hung down only from both sides of the head part and at the center in the longitudinal direction of the head part; The piston is composed of a skirt portion lacking a portion; and an outer wall portion formed integrally with the pin boss portion and recessed inward from both end surfaces of the head portion. Any attempt to oscillate around the piston pin can be effectively prevented by contact between the skirt portion along the length direction of the piston pin and the inner surface of the cylinder hole, and furthermore, the downward movement of both arcuate end surfaces of the head portion can be effectively prevented. Since there is no skirt part in the piston, the contact area of the skirt part with the inner surface of the cylinder hole is reduced compared to a case where the skirt part is formed to have the same shape as the head part, that is, an oval or elliptical cross section. This can reduce the friction loss of the piston, and can also contribute to reducing the weight of the piston.

In particular, since each of the skirt portions lacks the center portion in the longitudinal direction of the head length, that is, the longitudinal direction of the piston pin, the contact area of the skirt portion with the inner surface of the cylinder hole is further reduced, resulting in the aforementioned friction loss. The piston weight reduction effect can be further enhanced, and the surface contact of the skirt portion against the inner surface of the cylinder hole can be improved, thereby preventing uneven friction and rattling of the contact surfaces.

Furthermore, in the case where the skirt part is suspended from both sides along the length direction of the piston pin of the head part having an oval or elliptical planar shape as in the present invention, the piston has a neck around the piston pin during reciprocating movement. When the swinging movement is attempted, the moment acts on the skirt portion almost uniformly along the length direction of the piston pin, that is, without being biased toward the center, so as mentioned above, the center portion of the skirt portion is omitted. Even if the piston is tilted, the skirt portions at both ends of the missing portion can stably receive the moment and effectively restrict the swinging motion of the piston, resulting in disadvantages such as uneven friction between the piston and the cylinder hole due to the swinging motion. can be prevented from occurring.

In addition, the outer wall part, which is recessed inward from both end faces of the head part and is provided integrally with the pin boss, not only compensates for the decrease in the strength of the piston itself due to the reduction of the skirt part as described above, but also increases the overall strength of the piston. can be increased.

Furthermore, by extending the outer wall portion below the pin boss, the strength of the piston can be further increased.

[Brief explanation of the drawing]

FIG. 1 is a partially longitudinal side view of the piston of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a bottom view thereof. B...Pin boss part, H...Head part,
S...Skirt part, W...Outer wall part, 1
...End face, 2...Side surface, G;...
・Piston pin.

Claims (1)

[Scope of Claims] 1. A head portion having an oval or elliptical planar shape and having both end surfaces formed of circular arc surfaces and both side surfaces formed of flat or curved surfaces smoothly connected to the both end surfaces; A pin boss part that is integrally hung from the head part and supports the piston pin in the longitudinal direction of the head part; and a pin boss part that is integrally hung from only both sides of the head part, and is missing a central part in the longitudinal direction of the head part; A piston for an internal combustion engine, comprising: a skirt portion; and an outer wall portion formed integrally with the pin boss portion and recessed inward from both end surfaces of the head portion. 2. The piston for an internal combustion engine according to claim 1, wherein the outer wall portion extends below the pin boss portion.