JPS61277851A - Piston for internal-combustion engine - Google Patents

Abstract

PURPOSE:To suppress the quantity of oil entering into combustion chamber by making an oil return path having downwardly squeezed cross-section at the lower portion of oil return recess formed in the sideface in axial direction of piston pin. CONSTITUTION:A recess 11 for returning the oil scratched by an oil ring into oil pan is formed in the sideface of the skirt section 6 of piston 4 in axial direction of piston pin. Said recess 11 is constructed with an upper oil sump 12 and lower oil return paths 13, 13 where the oil sump 12 has the inclined sidefaces 12a, 12a to be restricted downward while the oil return path 13 has the inclined sidefaces 13a, 13a to be retricted downward where the bottom face facing against the sleeve will be narrower downwardly. Since the cross-section is restricted downward, oil will never rise from below the skirt section 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piston for an internal combustion engine, particularly one having a feature of oil return.

(Prior art) In internal combustion engines such as gasoline engines, a piston is slidably disposed on the inner peripheral surface of a cylinder sleeve, and the sliding motion of the piston is transmitted to the crankshaft via a connecting rod. I have to.

When the piston slides on the inner surface of the sleeve, an oil film is interposed between the inner surface of the sleeve and the outer surface of the piston in order to prevent seizure between the sleeve and piston and ensure smooth sliding. There is. This oil is supplied from the oil pan or the like below the piston, but if a large amount adheres to the inner circumferential surface of the sleeve, a large amount of oil will be burned out in the combustion chamber, which is undesirable in terms of oil consumption. Therefore, in the past, an oil ring was fitted in addition to the compression ring on the outer periphery of the piston head, and this oil ring scraped off the oil on the inner circumferential surface of the sleeve, and the scraped oil was formed in a small part on the skirt. It is guided inside the skirt part through the hole and dropped into the oil pan below.

(Problems to be Solved by the Invention) The conventional oil return structure described above has a problem in that oil scraped from the inner peripheral surface of the sleeve is difficult to return smoothly to the oil pan or the like.

That is, since the oil scraped off by the oil ring is guided downward through an extremely narrow portion, pressure from below may cause the oil to flow backwards and a portion of it may enter the combustion chamber. Particularly in the high-speed range of high-output engines with long strokes, increased oil consumption is a problem.
(Means for solving the problem) In order to solve the above problem, the present invention forms a recess (including a window) for oil return on the axial side surface of the piston pin of the piston skirt, and An oil return passage is provided in the lower part, and the cross-sectional area of this oil return passage is gradually narrowed toward the lower end of the skirt.

(Function) The oil scraped off by the oil ring goes along the outer peripheral surface of the skirt portion and enters the recess, and the oil that has entered the recess falls downward from the oil return passage.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view of the main part of an engine to which the piston according to the present invention is applied, FIG. 2 is a front view of the piston, and FIG.
The sectional view taken along the line A-A in the figure, and FIG. 4 is a side view of the piston.

The engine (1) has a sleeve (3) integrally provided in the cylinder part (2a) of the cylinder blower (2), and the piston (4) according to the present invention can freely slide on the inner peripheral surface of the sleeve (3). It is located in

The piston (4) is attached to the small end of the connecting rod (6) via a piston pin (15).
) is connected to a crankshaft (not shown). The piston (4) consists of an upper head part (5) and a lower skirt part (8), and the outer peripheral surface of the head part (5) has a groove (?) into which a compression ring (7) is fitted. 8), (8) and a groove (10) into which an oil ring (9) is fitted are formed.

Further, a recess (11) is formed on the axial side surface of the piston pin (15) of the skirt portion (6) for returning oil scraped off by the oil ring (8) to the oil pan or the like. This recess (11) corresponds to the upper oil reservoir (12).
and lower oil return passages (13), (13), and the oil reservoir (12) has side surfaces (12a), (12a).
) is an inclined surface that narrows downward, and the bottom surface (12b)
is a downwardly inclined surface as shown in Fig. 3, and the oil flowing into the oil reservoir (12) flows through the oil return passage (13).
, (13).

On the other hand, the oil return passages (13), (13) are formed as a pair on the left and right sides around the axis of the piston pin (15), and the upper end portions are continuous with the oil reservoir portion (12), and the lower end portions are connected to the bottom of the skirt portion (6). Both side surfaces (13a) and (+3a) of each oil return passage (13) that are continuous with the end surface are sloped surfaces that are narrowed downward, and the surface (13b) that faces the sleeve (3).
is an inclined surface whose depth gradually becomes shallower toward the bottom, and the entire depth of the oil return passageway (13) is the same as that of the oil reservoir section (13).
As a result of the depth being shallower than 2), the cross-sectional area of the oil return passage is gradually narrowed down, making it easier for the oil in the oil reservoir (12) to return. In addition, the oil return passage (
13) A part (6c) of the skirt portion (6) is left as is between (13) and (13).

On the other hand, the skirt portion (6) has a slightly elliptical shape as a whole, and its major axis direction is perpendicular to the axis of the piston pin (15), and its minor axis direction is a direction that coincides with the axis of the piston pin (15). , a clearance is formed between the side surface of the skirt portion where the recess (11) is formed and the inner peripheral surface of the sleeve (3), and the side surface of the skirt portion where the recess (11) is not formed is in close contact with the inner peripheral surface of the sleeve (3). That's what I do. In this way, by bringing the side surface perpendicular to the axis of the piston pin (15) into close contact with the inner peripheral surface of the sleeve (3), it is possible to prevent fluttering when the engine is driven. ) By forming a slight clearance between the oil ring (8) and the inner peripheral surface, the oil scraped off by the oil ring (8) can easily flow into the recess (11).

In particular, in this embodiment, as shown in FIG. 5, the major axis and minor axis of the ellipse are different from the upper part to the lower part of the skirt part (6). That is, Fig. 5 (a), (b), (
C) and (A) in Figure 2 respectively.

It is a figure showing the relationship between the outer diameter dimension of the skirt part (6) and the sleeve (3) corresponding to the positions (b) and (c), and the major axis of the ellipse at each position is (a+) and (a2).

(a3), if the short axis is (bθ, (bz), (bz), al < a2 = a2, bl < b2 < b
The dimensions are set to satisfy the relationship of i. Therefore, the second
The sleeve (
3) The clearance with the inner peripheral surface is small and other parts (6b
) with the inner circumferential surface of the sleeve (3) becomes somewhat larger, and oil flows along the surface of the portion (8b) into the oil reservoir (12) of the recess (11) as shown by the arrow.

The oil that has flowed into the oil reservoir (12) flows down the oil return passages (13) and (+3) and falls into the oil pan or the like.

(Effects of the Invention) As described above, according to the present invention, by forming a recess for oil return, oil can be returned more easily than in the past. Since the area is narrowed downward, oil does not rise from below the skirt, and the amount of oil entering the combustion chamber can be suppressed, resulting in extremely low oil consumption.

In addition, since the oil return passage is branched and a part of the skirt remains between them, it is possible to effectively prevent the piston from swinging in the axial direction of the piston pin when the engine is running. In addition, the major and minor axes of this ellipse are made so that the upper part of the skirt part is smaller than the lower part, which has many effects such as preventing piston fluttering and allowing oil to return smoothly. demonstrate.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of the main part of an engine to which the piston according to the present invention is applied, FIG. 2 is a front view of the piston, and FIG.
Figure 4 is a side view of the piston;
Figures (A) to (C) are diagrams showing the relationship between the shapes of the upper, middle, and lower parts of the skirt portion and the sleeve. In the drawings, (2) is the cylinder block, (3) is the sleeve, (4) is the piston, (8) is the skirt, (9) is the oil ring, (11) is the recess, and (12) is the oil reservoir. , (13) is an oil return passage. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Part 2 1) Patent Attorney Kuni Ohashi Part 1 Patent Attorney Yuyuki Koyama Patent Attorney No 1)
Shigeru Figure 1

Claims (3)

[Claims] (1) A recess for oil return is formed on the axial side surface of the piston pin in the skirt portion below the oil ring fitting groove formed on the outer periphery of the piston, and an oil return communicating with the lower end is formed at the bottom of this recess. A piston for an internal combustion engine, characterized in that a passage is formed, and the cross-sectional area of the oil return passage is gradually narrowed toward the lower end of the skirt. (2) The piston for an internal combustion engine according to claim 1, wherein the oil return passage is formed to branch left and right with respect to the piston pin. (3) The skirt portion of the piston has an elliptical shape with its major axis extending in a direction perpendicular to the axis of the piston pin, and the major axis of the upper part of the skirt portion is smaller than the major axis of the lower part of the skirt portion;
3. A piston for an internal combustion engine according to claim 1, wherein the short diameter of the upper part of the skirt part is smaller than the short diameter of the lower part of the skirt part.