JP2573591Y2 - 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.

[0002]

2. Description of the Related Art In a piston for an internal combustion engine, a piston body is constituted by a crown portion and a skirt portion, and a pin boss portion having a piston pin hole is formed in the skirt portion. On the opposite side of the pin boss portion from the crown portion side, it is necessary to have strength enough to withstand the inertia force of the piston body itself, and if an oil hole communicating with the piston pin hole is formed there, It is necessary to pay attention to the stress concentration around the oil hole. Conventionally, in order to alleviate the stress concentration, a chamfer is formed on the opposite side of the oil hole from the piston pin hole side (for example, Japanese Utility Model Application Laid-Open No. 60-5).
No. 4750).

[0003]

However, in the piston for an internal combustion engine described above, the other side of the crown portion side of the pin boss portion is cut in order to adjust the mass of the piston body. All or a part of the chamfered portion may be lost, and the effect of reducing stress concentration may be lost or reduced.

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 surely alleviate the stress concentration generated in the pin boss portion even when the mass adjustment is performed.

[0005]

In order to achieve the above object, a piston for an internal combustion engine according to the present invention comprises a piston body having a crown portion and a skirt portion, and a piston pin hole is formed in the skirt portion. A pin boss portion is formed, and the opposite side of the pin boss portion from the crown portion side is formed larger by the mass adjustment margin of the piston body, while the piston pin hole is formed on the opposite side of the pin boss portion from the crown portion side. An oil hole communicating with the oil hole is formed, the piston pin hole side of the oil hole is formed in a small diameter portion, the opposite side to the piston pin hole side is formed in a large diameter portion, and a chamfered portion is formed in an inner surface continuous portion of the oil hole. The position and the size of the chamfered portion are set such that at least a part of the chamfered portion remains when the piston body is cut to the maximum amount of the mass adjustment allowance.

[0006]

With the above arrangement, the mass adjustment of the piston body is
This is performed by cutting the opposite side of the pin boss from the crown.

When the above-mentioned mass adjustment is stopped in the range of the large diameter portion of the oil hole, all the chamfered portions remain, so that the stress concentration around the oil hole in the pin boss portion is reduced.

Further, since the opposite side of the oil hole from the piston pin hole side is a large diameter portion and not a chamfered portion,
The mass adjustment allowance is not reduced more than necessary, and since a sufficient thickness is secured on the opposite side of the pin boss portion from the crown portion side, it is not necessary to form a chamfered portion in the opening of the oil hole. .

Even when the above-described mass adjustment reaches the chamfered portion, a part of the chamfered portion remains, so that stress concentration around the oil hole in the pin boss portion is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front sectional view of a piston for an internal combustion engine in which a piston pin is not mounted in a direction perpendicular to the piston pin hole, with a left half omitted, FIG. 2 is an enlarged view of FIG. 1 showing a main part of the piston, FIG. 3 is a diagram showing the relationship between the amount of mass adjustment from the opposite end of the pin boss portion on the crown portion side and the maximum value of the generated stress.

The piston body 1 comprises a crown 1A and a skirt 1B. A pin boss portion 2 is formed in the skirt portion 1B, and a piston pin hole 3 is formed in the pin boss portion 2. The opposite side of the pin boss portion 2 on the side of the crown portion 1A is formed to be larger by an adjustment allowance (the maximum amount L in the shaded portion shown in FIGS. 1 and 2) for adjusting the variation in the mass of the piston body 1. I have.

An oil hole 4 extending in the direction of the center line of the piston body 1 and communicating with the piston pin hole 3 is formed on the opposite side of the pin boss portion 2 from the crown portion 1A side. The piston pin hole 3 side of the small diameter portion 4a
On the other hand, the opposite side of the piston pin hole 3 is formed in the large diameter portion 4b. C0.2 is provided on the inner surface continuous portion of the oil hole 4.
The above chamfered portion 5 is formed. The position and the size of the chamfered portion 5 are such that when the piston body 1 is cut to the maximum amount L of the adjustment allowance, as shown in FIG. 2, half or more of the axial length t of the chamfered portion 5 remains. Is set to The large diameter portion 4b is formed in a straight or tapered cylindrical locate hole.

In the above configuration, the mass adjustment of the piston body 1 is performed by cutting the pin boss 2 on the side opposite to the crown 1A.

When the mass adjustment is stopped in the range of the large diameter portion 4b of the oil hole 4, all the chamfered portions 5 remain, so that the stress concentration around the oil hole 4 in the pin boss portion 2 is reduced.

Further, since the large diameter portion 4b on the opposite side of the oil hole 4 from the piston pin hole 3 side is not a chamfered portion, the mass adjustment margin is not reduced more than necessary.
This is an extremely excellent point, as can be seen from the fact that, when a continuous chamfered portion is formed in the chamfered portion 5 instead of the large-diameter portion 4b, the mass adjustment margin is extremely reduced.

Further, since a sufficient thickness is secured on the opposite side of the pin boss portion 2 from the crown portion 1A side, the oil hole 4
It is not necessary to form a chamfered portion in the opening.

Even when the above-described mass adjustment reaches the chamfered portion 5, a part of the chamfered portion 5 remains.
, The stress concentration around the oil hole 4 is reduced.

[0019]

As described above, according to the present invention, a piston body is constituted by a crown portion and a skirt portion, and a pin boss portion having a piston pin hole is formed in the skirt portion.
An oil hole communicating with the piston pin hole is formed on the opposite side of the crown portion side of the pin boss portion from the crown portion side of the pin boss portion while being formed larger by the mass adjustment allowance of the piston body. Forming a small diameter portion on the piston pin hole side of the oil hole and a large diameter portion on the opposite side to the piston pin hole side, forming a chamfered portion on the inner surface continuous portion of the oil hole, Since the size is set so that at least a part of the chamfered portion remains when the piston body is cut to the maximum amount of the mass adjustment allowance, by cutting the opposite side of the pin boss portion from the crown portion side. The mass adjustment of the piston body can be easily performed.

Further, since at least a part of the chamfered portion can be left by the above-described mass adjustment, stress concentration around the oil hole in the pin boss portion can be surely alleviated. In addition, the large diameter portion of the oil hole minimizes the reduction of the mass adjustment allowance, preventing the trouble of the mass adjustment, and ensuring a sufficient thickness on the opposite side of the crown portion side of the pin boss portion. it can. Therefore, sufficient strength is secured on the opposite side of the pin boss from the crown.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a piston for an internal combustion engine according to an embodiment of the present invention in a state where a piston pin is not mounted and viewed from a direction perpendicular to a piston pin hole, with a left half omitted.

FIG. 2 is an enlarged view of FIG. 1 showing a main part of the piston.

FIG. 3 is a diagram showing the relationship between the amount of mass adjustment from the end of the pin boss portion on the side opposite to the crown portion and the maximum value of the generated stress.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston main body 1A Crown part 1B Skirt part 2 Pin boss part 3 Piston pin hole 4 Oil hole 4a Small diameter part 4b Large diameter part 5 Chamfered part L Maximum amount of mass adjustment allowance

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02F 3/00 F02F 3/22 F01M 1/06

Claims (1)

(57) [Scope of request for utility model registration] 1. A piston body comprising a crown portion and a skirt portion, a pin boss portion having a piston pin hole formed in the skirt portion, and a pin boss portion opposite to the crown portion side is provided with the pin boss portion. On the other hand, on the opposite side of the crown portion side of the pin boss portion, an oil hole communicating with the piston pin hole is formed, while the piston pin hole side of the oil hole is formed on the small diameter portion, The other side of the piston pin hole side is formed in a large diameter portion, and a chamfered portion is formed in the inner surface continuous portion of the oil hole, and the position and size of the chamfered portion are determined by adjusting the piston body to the mass adjustment allowance. A piston for an internal combustion engine, characterized in that at least a part of a chamfered portion is left when cutting to a maximum amount.