JP2006275002A - Piston for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve lubricity of the sliding surface of a skirt section of a piston for an internal combustion engine. <P>SOLUTION: The piston refers to a cylindrical piston of an internal combustion engine which is provided so as to freely make reciprocating motion in the cylinder, forming a combustion chamber. The piston is characterized by that at least two recesses are formed in different sliding directions on the sliding surface of the skirt section to slide relative to the inside-perimeter surface of the cylinder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

 The present invention relates to a piston for an internal combustion engine, and relates to a piston in which a concave portion is formed on a sliding surface of a skirt portion.

In reciprocating internal combustion engines, friction has been reduced by improving the lubricity between the inner circumferential surface of the cylinder and the side surface of the piston, thereby preventing seizure and improving the efficiency of the internal combustion engine. In Japanese Patent Laid-Open No. 10-122365, a concave portion having an extremely shallow depth of about 20 μm is formed adjacent to a piston ring groove provided on the piston crown side, so that the contact area with the inner peripheral surface of the cylinder is increased. There is disclosed a technique for optimizing and preventing seizure and causing the recess to function as an introduction passage for lubricating oil (engine oil) to form an oil film between the cylinder inner peripheral surface.
Japanese Patent Laid-Open No. 10-123365

  In the technology disclosed in Patent Document 1, in the combustion cycle, when the piston is raised, the recess functions as an introduction passage for the lubricating oil from the piston ring groove. Therefore, the sliding portion on the side surface of the skirt portion of the piston and the inner peripheral surface of the cylinder It is effective for oil film formation during

  However, generally, even when the piston is pushed down and lowered during the explosion / expansion stroke of the combustion cycle, it is important to form a sufficient oil film for smooth operation of the piston. That is, it is considered that the recess adjacent to the piston ring groove disclosed in Patent Document 1 does not have sufficient lubrication performance when the piston is lowered.

  The present invention has been made in view of the above technical background. In an internal combustion engine piston, a sufficient oil film is provided between a sliding surface on a side surface of the piston and an inner peripheral surface of the cylinder in the piston ascending and descending steps. It is a technical problem to provide a piston that prevents seizure and reduces friction and improves engine efficiency.

  The first technical means taken in order to solve the above technical problem is a cylindrical piston of the internal combustion engine which is provided in the cylinder of the internal combustion engine so as to be reciprocable and forms a combustion chamber in the cylinder. Then, at least two recesses are formed at different positions in the sliding direction on the sliding surface of the skirt portion that slides with respect to the inner peripheral surface of the cylinder.

  In addition to the first technical means, the second technical means taken in order to solve the above technical problem is that the concave portion is located closer to the combustion chamber side than the center in the sliding direction of the sliding surface. They are respectively provided on the opposite side of the combustion chamber, and are provided in the center in the circumferential direction of the sliding surface.

  In addition to the second technical means, the third technical means taken to solve the technical problem described above further includes a plurality of concave portions on both sides in the circumferential direction of the concave portion and on the center side in the sliding direction. It is to have established.

 The fourth technical means taken in order to solve the above technical problem is that, in addition to the first to third technical means, the concave portion has a shape whose central portion is deepest.

 According to the invention of claim 1, since at least two recesses are formed at different positions on the sliding surface of the piston skirt, each recess receives lubricating oil (engine oil) when the piston is raised and lowered. The oil can be temporarily stored and supplied to the sliding surface along with the stroke of the piston, and an oil film can be formed between the sliding surface and the inner circumferential surface of the cylinder.

 According to the invention of claim 2, at least the recess is provided on the combustion chamber side and the opposite side of the combustion chamber with respect to the center of the sliding surface in the sliding direction. When a reciprocating stroke is performed, one concave portion provided on the stroke direction side temporarily stores and supplies lubricating oil (engine oil), so that an oil film is stably formed when the piston is raised and lowered. Can do. In addition, when the connecting rod strokes the piston, a concave force is placed at the center in the circumferential direction of the sliding surface where the lack of lubricating oil is most likely to occur due to the pressing force acting in the direction perpendicular to the stroke direction. Therefore, stable oil film formation is achieved even in the central portion in the circumferential direction.

  According to the invention of claim 3, in addition to the concave portion arranged in the central portion in the circumferential direction, the concave portion is arranged on both end sides thereof, so that the depth of one concave portion is not deepened more than necessary. A recess can be formed over the entire circumference of the sliding surface to improve the lubricity.

  According to the invention of claim 4, by forming the shape of the recess with the central portion of the recess as the deepest, the storage amount of the lubricating oil is improved while the area of the recess in the sliding surface is reduced, and the sliding surface The image sticking can be prevented while maintaining a large area.

  Hereinafter, a first embodiment of a piston for an internal combustion engine of the present invention will be described with reference to the drawings. FIG. 1 shows a front view of a piston for an internal combustion engine of the present invention. FIG. 2 is a side view of the piston for an internal combustion engine of the present invention (a view taken along arrow A in FIG. 1).

  The piston 1 reciprocates (strokes) in a cylinder of an engine (not shown), and a combustion chamber is formed by the crown surface 2 and the inner periphery of the cylinder. Three ring grooves 5, 6, and 7 are formed on the outer periphery of the piston 1, and a top ring, a second ring, and an oil ring (not shown) are respectively mounted from the crown surface 2 side. A pin hole 4 is formed in the piston 1, and the piston 1 is connected to a crankshaft (not shown) via a connecting rod (not shown) by a pin (not shown) inserted and fixed in the pin hole 4. The The crankshaft is rotated by the reciprocating motion of the piston 1 (vertical motion in FIG. 1). When the piston 1 moves up and down, the skirt portion 3 formed longer than the other parts in the stroke direction has a sliding surface 10 that slides on the inner circumferential surface of the cylinder 1 so that the piston 1 moves up and down. Act as a guide. Further, the cross section perpendicular to the sliding direction of the piston 1 is cylindrical at the upper part of the piston including the ring groove, and the diameters La and Lb shown in FIG. 1 and FIG. It has an elliptical shape of Lb.

  FIG. 2 shows a side view of the piston 1 as viewed in the direction of arrow A in FIG. A plurality of recesses 11a, 11b, 11c, 12a, 12b, and 12c are formed on the sliding surface 10 of the piston 1 with respect to the cylinder inner peripheral surface. Each of these recesses has the deepest shape (depth: 20 to 50 μm) at the center, and the opening area within the sliding surface 10 is kept small, thereby ensuring a large sliding area. The seizure is prevented and the amount of lubricating oil (engine oil) stored is increased. Further, as described above, since the sliding surface 10 has an elliptical cross section of the piston 1, the radius of curvature is the smallest at the center of the sliding surface 10 in the circumferential direction.

  The concave portion 11a and the concave portion 12a having an elliptical opening are formed on the sliding surface 10 at a substantially central portion in the circumferential direction, and on the combustion chamber side of the sliding surface 10 in the piston stroke direction (see FIG. 2) and on the opposite side of the combustion chamber (lower side in FIG. 2). According to the arrangement of the recesses 11a and 12a, when the piston is lifted, the sliding surface 10 of the piston 1 slides with the inner peripheral surface of the cylinder, and at the substantially central portion in the circumferential direction where lubricating oil shortage is most likely to occur. In the early stage of sliding when the upper part of the piston 1 starts sliding, the lubricating oil is supplied from the recess 11a to promote oil film formation, and as a result, seizure can be prevented and frictional force can be reduced. Further, during the expansion stroke after combustion in the combustion cycle, even when the piston 1 descends, the amount of lubricating oil from the recess 12a disposed at the lower portion of the sliding surface 10 is reduced in a state where the lubricating oil is small on the inner circumferential surface of the cylinder. Supply is performed, and seizure can be prevented and frictional force can be reduced.

  Further, the concave portions 11b and 11c and the concave portions 12b and 12c having an elliptical opening are formed at both ends of the concave portion 11a and the concave portion 12a with respect to the vertical movement direction from the center of the sliding surface 10 in the vertical movement direction. The elliptical long axis of the opening is formed to be vertical. According to this, since the concave portion for lubrication can be formed over the entire circumference of the sliding surface 10, the entire sliding surface 10 can be protected from seizure.

  FIG. 3 shows a second embodiment of the present invention. The second embodiment is the same as the first embodiment except that the long axes of the concave portions 111b and 111c having an elliptical opening are inclined by θ1, and the long axes of the concave portions 112b and 112c are inclined by θ2. Specifically, the outer circumferential portions of the concave portions 111b and 111c are inclined upward, and the outer circumferential portions of the concave portions 112b and 112c are inclined downward. According to this configuration, when the piston 1 is raised, the lubricating oil flows out in the direction of the arrow (solid line), and the formation of an oil film is promoted at the central portion where the radius of curvature is the smallest and lubrication is likely to occur. Further, when the piston 1 is lowered, the lubricating oil flows out in the direction of the arrow (broken line), and seizure is prevented.

The front view of the piston for internal combustion engines which concerns on this invention. The side view of the piston for internal combustion engines which concerns on this invention. (A view in FIG. 1) Side view of a piston for an internal combustion engine according to a second embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piston 2 ... Crown surface 3 ... Skirt part 4 ... Pin hole 5 ... Ring groove 6 ... Ring groove 7 ... Ring groove 10 ... Sliding surface 11a, 11b, 11c, 111a, 111b, 111c ... recess 12a, 12b, 12c, 112a, 112b, 112c ... recess

Claims (4)

A cylindrical piston of an internal combustion engine that is provided in a cylinder of the internal combustion engine so as to be reciprocally movable and forms a combustion chamber in the cylinder,
A piston for an internal combustion engine, wherein at least two concave portions are formed at different positions in a sliding direction on a sliding surface of a skirt portion that slides with respect to an inner peripheral surface of the cylinder.   The recess is provided on each of the combustion chamber side and the opposite side of the combustion chamber from the center of the sliding surface in the sliding direction, and is provided in a central portion in the circumferential direction of the sliding surface. The piston for an internal combustion engine according to claim 1, wherein the piston is an internal combustion engine.   The piston for an internal combustion engine according to claim 2, wherein a plurality of recesses are further provided on both sides in the circumferential direction of the recess and on the center side in the sliding direction.   The piston for an internal combustion engine according to any one of claims 1 to 3, wherein the concave portion has a deepest central portion.

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