JPH08512Y2 - Internal combustion engine pistons - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a piston of an internal combustion engine having a concave combustion chamber at the top of the piston, and the center of the combustion chamber is offset from the center of the piston. Is.

[Conventional technology]

The problem that the amount of oil supplied to the piston portion in an internal combustion engine increases over time has been a problem in the past, and in order to reduce this oil consumption, the piston ring was improved. Or, the shape of the piston is devised.

The reason for the deterioration of the oil consumption over time is that the oil passes through the sliding surface between the top ring 2 and the liner 3 of the piston 1 shown in FIG. As a result, the hard carbon 5 rises and is exposed to a high temperature without being burned, and as a result, the hard carbon 5 adheres to the top land portion 7.

The hard carbon 5 adhering to the top land 7 scrapes up the oil adhering to the liner 3 during the upward stroke of the piston 1, so that the oil consumption increases, and further the hard carbon 5 gradually increases. Therefore, there is a problem that the oil consumption gradually increases, and the deterioration of the oil consumption over time becomes large.

In order to reduce the amount of hard carbon 5 attached to the top land portion 7 of the piston 1, the diameter of the top land portion 7 from the skirt portion of the piston 1 is conventionally 0.1 mm with respect to the skirt portion. It has been adopted to reduce the size by about 0.15 mm. The reduction of the diameter of the top land portion 7 of the piston 1 is called "cutback".

Although the amount of hard carbon 5 generated can be reduced by performing such a cutback,
There is an adverse effect that the waste volume of the combustion chamber increases and engine performance deteriorates.

On the other hand, the general shape of the profile of the top land portion 7 is orthogonal to the piston pin axis center in consideration of thermal expansion in the piston pin axis XX direction, which has low piston rigidity as shown in FIG. The diameter l'in the axial direction and the diameter L'in the axial direction of the piston pin are set so that L '<l'.

However, in the piston 1 which receives high heat in the top land portion 7, the carbonized oil adheres to the top land portion 7 and becomes the hard carbon 5 as shown in FIG. 8, and the piston 1 with respect to the piston pin axis XX. When the top land portion 7 collides with the liner 3 by falling in the direction Y-Y at a right angle, the hard carbon 5 is sandwiched between the piston 1 and the liner 3 and hardened on the surface of the top land portion 7.

The hard carbon 5 thus hardened eventually forms a layer, and it becomes one of the factors that abrade the liner 3 and deteriorate the oil consumption.

Therefore, it is conceivable to solve the above problem by reducing the dimension in the right-angled direction YY gradually, but by reducing the dimension in the right-angled direction YY, the waste in the combustion chamber 4 is reduced. However, there is a problem in that the volume of the engine increases and the engine performance is adversely affected.

On the other hand, in order to solve the above-mentioned problem, the actual construction of a piston in which the top land of the piston is partially shaved off from both side edges in the direction perpendicular to the piston pin axis center line
As shown in FIG. 5 and the device of the publication, the piston pin axis XX direction, the diameter L, and the diameter 1 in the direction Y-Y orthogonal thereto are
The profile shape of the top land portion 7 with L> l has been put to practical use. However, as shown in FIGS. 6 and 7, when the piston 1 has a concave combustion chamber 4 at the top, the outer periphery of the combustion chamber 4 shown by the arrow A approaches the outer periphery of the piston 1. Locally expands to cause local wear of the liner 3. This local wear causes deterioration of oil consumption over time. Therefore, if the top land portion 7 is cut back as in the conventional case, the diameter 1 in the right-angled direction YY in FIG. Becomes worse, which is especially fatal for an institution with insufficient performance.

[Problems to be Solved by the Invention] The present invention has been made in order to solve the above-mentioned conventional problems, and reduces the diameter of the top land portion with respect to the piston skirt portion, so-called cutback amount as much as possible. A piston for an internal combustion engine that can be made smaller to prevent the engine performance from deteriorating due to an increase in the dead volume of the combustion chamber, reduce the amount of hard carbon adhered to the top land, and reduce the local wear of the liner. It is intended to be provided.

[Means for solving the problem]

As means for solving the above-mentioned problems, the piston of the internal combustion engine of the present invention is a piston of an internal combustion engine in which the center of the combustion chamber is offset from the center of the piston, and the shape of the top land portion is the center of the piston. The combustion chamber is formed so as to have an elliptical shape having a minor axis in a direction connecting a portion closest to the outer periphery of the piston and a major axis in a direction orthogonal to the direction.

〔Example〕

An embodiment of a piston of an internal combustion engine of the present invention will be described below with reference to the drawings.

The piston 1 of the embodiment shown in FIGS. 1 and 2 is formed by offsetting the center M of the concave combustion chamber 4 from the center N of the piston 1, as in FIGS. 6 and 7. And the combustion chamber 4 is arranged with an inclination of an angle θ with respect to a direction Y-Y perpendicular to the piston pin axis XX.

With such an arrangement, the combustion chamber 4 is provided on the outer circumference of the piston 1.
In the portion where the outer periphery of the above is closest, that is, in the top land portion 7 indicated by the arrow A, the temperature becomes higher due to the approach of the combustion chamber 4 as compared with other portions, and the thermal expansion also increases accordingly.

Therefore, as shown in FIG. 1, the profile of the top land portion 7 is adjusted to the position of the combustion chamber 4, and the cutback of the portion indicated by the arrow A is made large. In performing this cutback, the direction connecting the center N of the piston 1 and the portion where the outer periphery of the combustion chamber 4 comes closest to the outer periphery of the piston 1 (the portion indicated by arrow A) is defined as the minor axis, and the direction orthogonal to this direction is defined. The top land portion 7 was formed to have an elliptical shape with a long diameter.

In the conventional example shown in FIG. 5, the profile of the top land portion 7 had to be l-2α, but in this embodiment, l-l "and the cutback can be reduced,
Local wear of the liner can be prevented without increasing the waste volume of the combustion chamber 4 by that amount. Therefore, when the engine is operating, the liner 3 and the top land portion 7 do not increase the total cutback amount more than necessary.
The gap between and is uniformed, and the amount of hard carbon 5 attached to the top land portion 7 can be reduced.

The relationship between the oil replenishment amount and the operating time when the cutback amount of the piston 1 in this embodiment is 0.74 mm and the eccentricity of the center of the top land portion 7 eccentric from the center N of the piston 1 is 0.04 mm Is shown by the solid line in FIG. The cut-back amount is 1.0 mm, and the oil supply amount of the conventional piston 1 in which the center of the top land portion 7 is not eccentric from the center N of the piston 1 is shown by a broken line.

It has been confirmed that the piston 1 of this embodiment requires a smaller amount of oil supply than the conventional piston 1 although the cutback amount is smaller than that of the conventional piston 1.

It should be noted that such a profile shape is used for the top land portion 7
In addition, it may be applied to the second and third lands.

[Effect of device]

As described above, in the piston of the internal combustion engine of the present invention, in the piston of the internal combustion engine in which the center of the combustion chamber is offset from the center of the piston, the shape of the top land portion is the center of the piston and the outer periphery of the combustion chamber. Is formed in an elliptical shape having a minor axis in a direction connecting a portion closest to the outer circumference of the piston and a major axis in a direction orthogonal to this direction.

Therefore, the direction that connects the center of the piston and the part where the outer periphery of the combustion chamber comes closest to the outer periphery of the piston has a short diameter, so that the cutback amount of the topland part where the combustion chamber comes closest can be maximized. Therefore, since the cutback amount of the portion where the thermal expansion is maximized is the maximum and the top land portion in the major axis direction in which the cutback amount is the minimum or zero does not have a dead volume, this dead volume causes The deterioration of engine performance can be reduced as much as possible.

In addition, this eliminates the need for making a larger cutback than is necessary with the conventional piston, so that the oil rise can be reduced and the amount of hard carbon generated by the deterioration of the oil is reduced. be able to.

Furthermore, since local abrasion of the liner due to the hard carbon can be reduced, deterioration of oil consumption over time can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view in which a combustion chamber for explaining a profile of a top land portion of a piston in one embodiment of the present invention is omitted,
FIG. 2 is a side view of FIG. 1, and FIG. 3 is a diagram comparing the oil consumption amounts of the piston of FIG. 1 and a conventional piston. FIG. 4 and FIG. 5 are plan views in which the combustion chamber for explaining the profile of the top land portion of different conventional pistons is omitted, and FIG. 6 is a plan view of the piston of FIG.
The drawing is a side view of the main part of FIG. FIG. 8 is a sectional side view of a main part for explaining the oil rise of the conventional piston. 1 ... Piston, 4 ... Combustion chamber, 7 ... Topland, M ... Center of combustion chamber, N ... Center of piston.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16J 1/00

Claims (1)

[Scope of utility model registration request] 1. A piston of an internal combustion engine in which the center of the combustion chamber is offset from the center of the piston, the shape of the top land is defined as the center of the piston, and the portion where the outer periphery of the combustion chamber is closest to the outer periphery of the piston. The direction of tying is short,
A piston for an internal combustion engine formed into an elliptical shape having a major axis in a direction orthogonal to this direction.