JPH1078130A - Internal combustion engine piston - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide a piston of an internal combustion engine that is reduced in weight while ensuring piston strength. SOLUTION: A piston 10 of an internal combustion engine having a pair of pin boss portions 28 forming a piston pin hole 34 and a pair of side walls 36, 38 located on opposite sides with respect to the piston pin hole on a piston head bottom wall surface 26. At the time of the engine explosion stroke, a reinforcing bridging wall 40 for bridging the side wall 36 having a larger pressing force received from the cylinder wall of the engine body and the lower portion of the pin boss portion is formed. No reinforcing bridging wall is formed between the side wall 38 receiving the smaller pressing force and the lower portion of the pin boss portion, and the outer peripheral surface 44 of the lower portion of the pin boss portion having no reinforcing bridging wall is formed by the piston pin. A substantially cylindrical wall was formed with respect to the center of the hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston for an internal combustion engine.

[0002]

2. Description of the Related Art An elliptical outer peripheral wall extending downward from a bottom wall surface of a piston head is provided, a space for receiving a leading end of a connecting rod is formed in the outer peripheral wall, and a hole for inserting a piston pin is formed in the outer peripheral wall. A provided piston of an internal combustion engine is known. Further, a piston of an internal combustion engine that meets the demand for weight reduction is disclosed in, for example, Japanese Utility Model Laid-Open No. 6-49742. Here, weight reduction is achieved by further providing holes on both sides of the piston pin insertion hole. That is, the piston includes a pair of pin bosses forming a piston pin insertion hole, and a pair of side walls having arcuate outer wall surfaces symmetrically located on opposite sides with respect to a center axis of the piston pin insertion hole. A structure is provided on the bottom wall surface of the head, and further includes a reinforcing bridging wall extending from a lower portion of the pin boss portion to both outer peripheral walls. The piston receives a pressing force from the cylinder inner wall surface when sliding in the cylinder of the engine body. However, since the piston has a reinforcing bridging wall extending to both outer peripheral walls, the outer periphery can withstand the pressing force. Wall strength is ensured.

[0003]

However, there is room for further improvement in the above-mentioned piston in order to reduce the weight. An object of the present invention is to provide a piston of an internal combustion engine that is reduced in weight while ensuring the strength of the piston.

[0004]

According to the first aspect of the present invention, a pair of pin bosses forming a piston pin hole and a pair of side walls located on opposite sides with respect to the piston pin hole are formed on the piston head bottom. In the piston of the internal combustion engine provided on the wall surface, a reinforcing bridging wall for bridging the lower side of the pin boss portion and the side wall having a larger pressing force received from the cylinder wall of the engine body during the engine explosion stroke is formed, An outer peripheral surface of the lower portion of the pin boss portion where the reinforcing bridge wall is not provided without forming a reinforcing bridge wall between the side wall having a smaller pressing force received from the cylinder wall surface of the engine body and the lower portion of the pin boss portion. Is a substantially cylindrical wall with respect to the center of the piston pin hole. According to a second aspect of the present invention, in the piston of the internal combustion engine according to the first aspect, a rib extending from a bottom wall surface of the piston head to a lower portion of the side wall is provided on an inner wall surface of the side wall having the smaller pressing force.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows the piston of the present invention during an engine explosion stroke. In FIG. 1, 10 is a piston of the present invention, 12 is a connecting rod connected to the piston 10, 14 is an engine body, 16 is a cylinder formed on the engine body 14 to house the piston 10 and the connecting rod 12, 18 is an intake port, 20 is an intake valve arranged at the intake port 18, 22 is an exhaust port, 24 is an exhaust port 22
It is an exhaust valve arranged in. FIG. 2 shows a piston 1 of the present invention.
0 is a bottom view, and FIG. 3 is a sectional view taken along line AA of FIG. The piston 10 of the present invention has a pair of pin bosses 28 extending downward from the bottom wall surface 26 of the piston head. The pin boss portions 28 are symmetrically located on opposite sides with respect to the central vertical plane P2 of the piston head 30.
The pin boss portion 28 has an opening 32 for a piston pin hole, and the piston pin hole 3 extends in a direction perpendicular to the central vertical plane P2.
4 is formed. Further, the piston 10 of the present invention has a pair of side walls 36 and 38 having an arc-shaped outer wall surface extending downward from the peripheral bottom wall surface of the piston head 30. These side walls 36, 38 are located symmetrically opposite one another with respect to the central axis of the piston pin hole 34 and slide within the cylinder 16 of the engine during engine operation. Further, the piston 10 has a reinforcing bridging wall 40 extending from a lower portion of each pin boss portion 28 to a portion of one side wall 36 corresponding to each pin boss portion 28.
That is, the reinforcing bridge wall 40 bridges the lower portion of the pin boss portion 28 and one side wall (hereinafter, a bridge side wall) 36. On the inner wall surface of the other side wall (hereinafter, rib side wall) 38, a reinforcing rib 4 is provided.
2 are provided. The outer peripheral surface 44 facing the rib side wall 38, that is, the lower part of the pin boss portion 28 where the reinforcing bridging wall 40 is not provided is a cylindrical wall surface with respect to the center of the piston pin hole opening 32. In other words, according to the present invention, the piston pin hole 34 is formed in the oval outer peripheral wall extending downward from the piston head bottom wall surface 26, and one of the outer peripheral wall portions adjacent to the piston pin hole 34 is formed. The outer peripheral wall portion is hollowed out while leaving the reinforcing bridge wall 40, and the outer peripheral wall portion on the other side is hollowed out without leaving the reinforcing bridge wall.
Further, of the outer peripheral wall portion defining the piston pin hole 34, the lower outer peripheral surface of the outer peripheral wall portion where the reinforcing bridge wall is not formed has a smooth surface, that is, a cylindrical shape with respect to the center axis of the piston pin hole 34. It will be a wall. In FIG. 2, 4
Reference numeral 6 denotes a plurality of oil holes for introducing lubricating oil into the pin boss 28 and the piston head 30. FIG. 4 shows FIG.
FIG. 3 is a cross-sectional view taken along line BB of FIG. Piston head 30
A substantially arc-shaped side wall reinforcing rib 42 which is concave with respect to the inner wall surface of the rib side wall 38 is provided with a predetermined thickness. The ribs 42 extend from both ends of a connection portion between the piston head bottom wall surface 26 and the rib side wall 38 to a central portion below the rib side wall 38. When the rib is provided on the rib side wall according to the present invention, both ends of the rib are connected to a connection portion between the piston head having relatively high strength and the rib side wall, and a portion of the rib side wall where the pressing force is most applied from the cylinder inner wall surface is formed. It is important to pass at least a part. Therefore, in addition to the semicircular arc shape as in this embodiment, a V-shaped or U-shaped one is also possible. However, in order to reduce the weight, a rib having a semicircular shape as in the present embodiment is preferable as a rib which is present in the shortest distance and in the vicinity of the portion where the pressing force is most applied and has no portion with a small radius of curvature.

Next, the operation of the present invention will be described. As described above, FIG. 1 shows the piston 10 during the engine explosion stroke, and FIG. 5 shows the piston 1 during the engine compression stroke.
0 is shown. The piston 10 of the present invention is arranged such that the bridging side wall is located on the opposite side of the crankpin with respect to the plane P1 including the crankshaft when the crankpin rotates from the top dead center of the explosion or the top dead center of the intake. In the engine explosion stroke shown in FIG. 1, an axial force is applied to the piston head by an explosion in the cylinder. However, since the connecting rod which receives this force tilts with respect to the piston head axis with the rotation of the crankshaft, the force is divided into a force in the longitudinal direction of the connecting rod and a force in a direction perpendicular to the piston head axis. Therefore, a pressing force is applied to the bridge side wall 36 as a reaction force from the cylinder inner wall surface 48. Conversely, during the engine exhaust stroke shown in FIG.
A pressing force is applied to the rib side wall 38 from the cylinder inner wall surface 48. FIG. 6 shows the pressing force applied to the bridge side wall 36 and the rib side wall 38 during each engine operation stroke. The solid line in FIG. 6 indicates the pressing force applied to the bridging side wall 36, and the dotted line indicates the pressing force applied to the rib side wall 38. A pressing force is applied to the bridging side wall 36 in the intake stroke and the explosion stroke, and a pressing force is applied to the rib side wall 38 in the compression stroke and the exhaust stroke. As shown in FIG. 6, the pressing force applied to the bridging side wall 36 and the rib side wall 38 is not equal, and the pressing force applied to the bridging side wall 36 in the engine explosion stroke is the largest. That is, the bridging side wall 36 is disposed so as to receive a larger pressing force from the cylinder wall surface of the engine body during the engine explosion stroke. In the present invention, since the reinforcing bridging wall 40 is provided between the bridging side wall 36 to which the greatest pressing force is applied and the lower part of the pin boss portion 28, the strength of the bridging side wall 36 is such that it can withstand the large pressing force. It has become. On the other hand, by not providing the reinforcing bridging wall 40 on the rib side wall 38 which receives a relatively small pressing force, the weight of the piston 10 is reduced. Further, a rib 42 is provided on the rib side wall 38 to reinforce the rib side wall 38 against a small pressing force. However, the rib may not be provided depending on the pressing force received by the rib side wall or the structure of the piston itself.

When the piston 10 slides up and down in the cylinder 16 during operation of the engine, the piston pin 5
A force is applied to the pin boss 28 from zero. In the present invention, the outer peripheral surface 44 below the pin boss portion 28 where the reinforcing bridging wall 40 is not formed is a cylindrical wall surface with respect to the center of the piston pin hole 34. Generally, if a member has a portion with a small radius of curvature, stress concentrates on that portion, which causes breakage. However, in the present invention, since there is no portion with a small radius of curvature of the wall surface, such as a protrusion or a dent, on the outer peripheral surface of the lower portion of the pin boss portion, concentration of stress on the lower portion of the pin boss portion is suppressed. Furthermore, in the present application, since the reinforcing bridge wall is provided on the bridge side wall, the weight of the piston portion on the bridge side wall side of the plane P1 including the crankshaft is heavier than the weight of the piston portion on the rib side wall side. Piston is flat P at top dead center of explosion
When the piston is completely symmetrical with respect to 1 and the longitudinal axis of the connecting rod is on the plane P1, the explosion force does not act in the direction of rotating the crankshaft, so that the piston is difficult to descend from the top dead center. Accordingly, the effect of the explosive force on the piston head differs between the left and right sides of the plane P1, so that the piston easily descends from the top dead center of the explosion.

[0008]

According to the first aspect of the present invention, a reinforcing bridging wall for bridging the lower side of the pin boss portion and the side wall having a larger pressing force received from the cylinder wall surface of the engine body during the engine explosion stroke is formed. As a result, the strength of the side wall receiving the large pressing force is secured, and a reinforcing bridge wall is formed between the side wall receiving the small pressing force from the cylinder wall of the engine body and the lower portion of the pin boss during the engine explosion stroke. Therefore, the formation of the reinforcing bridge wall, which is unnecessary because the pressing force received is small, is omitted, so that the piston is further reduced in weight, and the lower portion of the pin boss portion without the reinforcing bridge wall is provided. By making the outer peripheral surface a substantially cylindrical wall surface with respect to the center of the piston pin hole, stress concentration is avoided because a small-diameter wall surface does not exist on the outer peripheral surface below the pin boss portion, and the strength of the pin boss portion is also ensured. Door can be. According to the second aspect of the present invention, a rib extending from the bottom surface of the piston head to the lower portion of the side wall is provided on the inner wall surface of the side wall having the smaller pressing force, thereby minimizing the weight applied to the piston. In addition, the strength of the side wall can be increased.

[Brief description of the drawings]

FIG. 1 is an engine sectional view showing a piston of the present invention during an engine explosion stroke.

FIG. 2 is a bottom view of the piston of the present invention.

FIG. 3 is a sectional view of the piston taken along line AA of FIG. 2;

FIG. 4 is a sectional view of the piston taken along line BB in FIG. 2;

FIG. 5 is an engine sectional view showing the piston of the present invention during an engine compression stroke.

FIG. 6 is a diagram showing a pressing force applied to a side wall in each engine stroke.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Piston 14 ... Engine main body 26 ... Piston head bottom wall surface 28 ... Pin boss part 30 ... Piston head 34 ... Piston pin hole 36 ... Bridge side wall 38 ... Rib side wall 40 ... Reinforcement bridge wall 42 ... Rib 44 ... Pin boss lower part Outer peripheral surface

Claims (2)

[Claims] 1. A piston of an internal combustion engine having a pair of pin boss portions forming a piston pin hole and a pair of side walls located on opposite sides with respect to the piston pin hole on a bottom wall surface of a piston head. Forming a reinforcing bridging wall bridging the side wall with the larger pressing force received from the cylinder wall of the engine body and the lower part of the pin boss,
A pin boss portion in which no reinforcing bridge wall is formed between the side wall of the engine body having a smaller pressing force received during the engine explosion stroke and the lower portion of the pin boss portion, and the reinforcing bridge wall is not provided. An internal combustion engine piston, wherein a lower outer peripheral surface is a substantially cylindrical wall surface with respect to the center of the piston pin hole. 2. The piston of an internal combustion engine according to claim 1, wherein a rib extending from a bottom wall surface of the piston head to a lower portion of the side wall is provided on an inner wall surface of the side wall having the smaller pressing force.