JP2020056371A - Piston for internal combustion engine - Google Patents

Abstract

To provide a piston for an internal combustion engine capable of efficiently converting kinetic energy of an oil with a reciprocal motion of the piston within a cylinder into kinetic energy which moves from an inflow port to an outflow port within an oil passage in the piston of an internal combustion engine.SOLUTION: The present invention relates to a piston for an internal combustion engine, and an oil passage 20b including an inflow port and an outflow port is formed in a circumferential direction of the piston. When a direction at a head side of the piston with respect to the oil passage 20b is defined as an upper direction and a direction at an opposite side is defined as a lower direction in a stroke direction of the piston, the piston for internal combustion engine comprises: a first recess 22b linearly extending from a lower part to an upper part so as to be tilted toward the side of the outflow port on a first oil guide surface M1 which is an inner side wall surface at an upper side of the oil passage in the stroke direction; and a second recess 24b linearly extending from an upper part to a lower part so as to be tilted toward the side of the outflow port on a second oil guide surface M2 which is an inner side sidewall surface at a lower side of the oil passage in the stroke direction.SELECTED DRAWING: Figure 7

Description

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

  2. Description of the Related Art In an internal combustion engine, a piston structure is known in which an oil passage through which oil flows is provided in order to cool the piston. Here, various methods have been proposed to improve the oil cooling effect in the oil passage of the piston.

  For example, in the piston for an internal combustion engine described in Patent Literature 1, as shown in FIG. 18, a cooling cavity 120 (corresponding to an oil passage) for flowing and cooling oil through a piston main body 110 (corresponding to a piston) is provided. . The cooling cavity 120 is provided so as to gradually increase in size (increase in cross-sectional area) from the opening (corresponding to the inlet) of the inlet passage 212 to the opening (corresponding to the outlet) of the outlet passage 214. The pressure loss of the oil flowing through the inside 120 is reduced, and the flow rate of the oil is increased.

  In addition, the cooling cavity 120 is inclined downward with respect to the direction in which the piston body 110 moves up and down from the opening side of the inlet passage 212 to the opening side of the outlet passage 214 with respect to the direction in which the piston body 110 moves up and down. The oil inside 120 is positively moved toward the outlet passage 214. Thereby, the flow rate of oil in the cooling cavity 120 of the piston main body 110 increases, and the cooling effect in the piston main body 110 is improved.

JP 2005-48650 A

  In the piston for an internal combustion engine described in Patent Literature 1, the oil in the cooling cavity 120 is not always filled in the cooling cavity 120 without gaps. Oil accumulates at the lower end in the cooling cavity 120 when the piston is moving upward, and accumulates at the upper end in the cooling cavity 120 when the piston is moving downward. That is, the oil in the cooling cavity 120 also moves between the upper end and the lower end in accordance with the vertical movement of the piston.

  The kinetic energy of the movement of the oil is the kinetic energy of the vertical movement in the cooling cavity 120, and is not used in Patent Literature 1 as the kinetic energy from the inlet passage 212 to the outlet passage 214 in the cooling cavity 120.

  When the oil moves from the upper end to the lower end in the cooling cavity 120, most of the kinetic energy obtained by the oil is lost due to collision with the lower end and agitation, and the oil accumulates at the lower end. Similarly, when the oil moves from the lower end to the upper end in the cooling cavity 120, most of the kinetic energy obtained by the oil is lost due to collision with the upper end and agitation, and the oil accumulates at the upper end (in the vertical direction). The kinetic energy is not used as kinetic energy from the entrance passage 212 to the exit passage 214.)

  In Patent Literature 1, when the piston is moving upward, the oil pressed against the lower end in the cooling cavity 120 is moved from the inlet passage 212 to the outlet passage 214 along the lower slope in the cooling cavity 120. In the direction toward.

  As described above, in Patent Document 1, the kinetic energy of the oil moving up and down in the cooling cavity 120 is not effectively used as the kinetic energy moving in the direction from the inlet passage 212 to the outlet passage 214. The oil in the cavity 120 cannot be moved more efficiently in the direction from the inlet passage 212 to the outlet passage 214.

  The present invention has been made in view of such a point, and in a piston of an internal combustion engine, kinetic energy of oil accompanying reciprocation in a cylinder of a piston moves from an inlet to an outlet in an oil passage. An object of the present invention is to provide a piston for an internal combustion engine that can efficiently convert kinetic energy.

  In order to solve the above problems, a first invention is a piston for an internal combustion engine, wherein an oil passage for circulating cooling oil is formed inside the piston, and the oil passage is provided with an oil passage. The piston has an inflow port for inflow and an outflow port for outflow, and is formed in a circumferential direction of the piston, and in a stroke direction for reciprocating the piston in a cylinder, a direction of the head side of the piston with respect to the oil passage in a stroke direction. When the upper direction is set to the upper direction and the opposite direction is set to the lower direction, the upper side in the stroke direction of the oil passage is divided into upper and lower sides by a plane passing through the center axis of the oil passage and orthogonal to the stroke direction. A first concave portion extending linearly from bottom to top so as to be inclined toward the outlet at least in a part of a first oil guide surface as a wall surface; Is a second oil guide that is a first convex portion and an inner wall surface that is a lower side in the stroke direction of the oil passage when the oil passage is vertically divided on a plane passing through the central axis of the oil passage and orthogonal to the stroke direction. A piston for an internal combustion engine, wherein at least one of a second concave portion or a second convex portion extending linearly from top to bottom so as to be inclined toward the outlet side is provided on at least a part of the surface. .

  A second invention of the present invention is the piston for an internal combustion engine according to the first invention, wherein the first concave portion or the first convex portion passes through the central axis of the oil passage and extends in the stroke direction. A radially inner surface of the piston in the first oil guide surface when divided by a cylindrical surface parallel to the cylinder surface, and a cylindrical surface parallel to the stroke direction passing through the central axis of the oil passage. The first oil guide surface is provided on the outer surface of the piston in the radial direction, and the second concave portion or the second convex portion passes through the central axis of the oil passage and extends in the stroke direction. A radially inner surface of the piston in the second oil guide surface when divided by a parallel cylindrical surface and a cylindrical surface parallel to the stroke direction passing through the central axis of the oil passage. A radial outer surface of said piston in said second oil guide face of the case, the provided is a piston for an internal combustion engine.

  According to a third aspect of the present invention, there is provided a piston for an internal combustion engine, wherein an oil passage through which cooling oil flows is formed inside the piston, and wherein the oil passage has an inlet through which oil flows. The piston is formed in the circumferential direction of the piston, and in a stroke direction for reciprocating the piston in a cylinder, a head-side direction of the piston with respect to the oil passage is an upward direction. When the opposite direction is the downward direction, the cross section of the oil passage orthogonal to the central axis of the oil passage is an ellipse, and the direction of the major axis of the ellipse is inclined with respect to the stroke direction. The strike of the oil passage when the oil passage is vertically divided by a conical surface passing through the center axis of the oil passage and having the major axis passing through the center axis and having a generatrix as a generating line. A first concave portion or a first convex portion extending linearly from bottom to top so as to be inclined toward the outflow port side on at least a part of a first oil guide surface which is an inner wall surface on the upper side in the work direction; A second oil guide surface that is an inner wall surface that is the lower side in the stroke direction of the oil passage when the oil passage is vertically divided by a conical surface having the major axis passing through the center axis as a generating line and passing through the center axis of the oil passage. A piston for an internal combustion engine, wherein at least a part of at least one of a second concave portion and a second convex portion extending linearly from top to bottom so as to be inclined toward the outlet side is provided.

  A fourth invention of the present invention is the piston for an internal combustion engine according to the third invention, wherein the first concave portion and the second concave portion, or the first convex portion and the second convex portion are continuous. This is a piston for an internal combustion engine, which is formed in a spiral shape and integrally formed.

  According to a fifth aspect of the present invention, there is provided the piston for an internal combustion engine according to the fourth aspect, wherein the first convex portion and the second convex portion are formed on a helical member separately from the piston. And wherein the spiral member is arranged in the oil passage.

  According to the first aspect, when the movement of the piston changes from upward stroke to downward stroke, the oil flows along the first concave portion or the first convex portion provided on the first oil guide surface, and flows through the oil passage. It is moved from the inlet to the outlet. When the movement of the piston changes from downward stroke to upward stroke, the oil flows along the second concave portion or the second convex portion provided on the second oil guide surface, and flows from the inlet to the outlet in the oil passage. Moved. As described above, the kinetic energy of the oil accompanying the reciprocating motion of the piston can be efficiently converted into the kinetic energy for moving in the oil passage from the inlet to the outlet, so that the oil moved from the inlet to the outlet. , The cooling efficiency of the piston can be improved.

  According to the second aspect, the first concave portion or the first convex portion is provided on both the radially inner surface and the radially outer surface of the piston in the first oil guide surface, and the second concave portion or the second concave portion is provided. The protrusion is provided on both the radially inner surface and the radially outer surface of the piston in the second oil guide surface. Accordingly, compared to the case where the first oil guide surface and the second oil guide surface are provided on only one of the radially inner surface and the radially outer surface, the oil accompanying the reciprocating motion of the piston is provided. Can be efficiently converted by the kinetic energy moving from the inlet to the outlet in the oil passage.

  According to the third invention, since most of the first oil guide surface and the second oil guide surface are formed on the surface having a small curvature along the major axis direction, the resistance force received from the surface is smaller than that of the surface having a large curvature. Since it can be made smaller, the kinetic energy of the oil can be efficiently converted by the kinetic energy moving from the inlet to the outlet when the oil is moved.

  According to the fourth aspect, the first concave portion and the second concave portion, or the first convex portion and the second convex portion are formed continuously and integrally on the inner wall surface of the oil passage. The oil is smoothly moved from the inlet to the outlet in the oil passage.

  According to the fifth aspect, the thermal conductivity of the material forming the first convex portion and the second convex portion is higher than the thermal conductivity of the material forming the oil passage (piston). Heat transfer to the first protrusion or the second protrusion and heat transfer from the first protrusion or the second protrusion to the oil can be promoted, and the cooling efficiency can be further improved.

It is a figure explaining the whole piston composition of a 1st embodiment. It is sectional drawing seen from the II-II direction in FIG. FIG. 3 is an enlarged schematic diagram illustrating details of a radially inner surface of an oil passage viewed from a direction III in FIG. 2. It is a schematic diagram of a section of an oil passage explaining movement of oil in an oil passage accompanying movement from the top to the bottom of a piston. FIG. 3 is an enlarged schematic diagram illustrating details of a radially outer surface of an oil passage viewed from a direction V in FIG. 2. It is a schematic diagram of a section of an oil passage explaining movement of oil in an oil passage accompanying movement of a piston from the bottom to the top. It is a perspective view explaining an oil passage of a 2nd embodiment. FIG. 8 is a diagram illustrating a cross section viewed from a direction VIII in FIG. It is a perspective view explaining an oil passage of a 3rd embodiment. It is a perspective view explaining another example of an oil passage of a 3rd embodiment. It is a perspective view explaining an oil passage of a 4th embodiment. It is a perspective view explaining an oil passage of a 5th embodiment. It is a perspective view explaining an oil passage of a 6th embodiment. It is a perspective view explaining an oil passage of a 7th embodiment. It is sectional drawing explaining the oil passage formed of the salt core in the piston. It is sectional drawing explaining the oil passage in case the 1st convex part and the 2nd convex part comprised by the spiral member are another members. FIG. 4 is a cross-sectional view illustrating an oil passage when the cross-section of the oil passage is not an ellipse or a circle. It is sectional drawing explaining the conventional piston for internal combustion engines.

● [Configuration and operation of the internal combustion engine piston (piston 10) of the first embodiment (FIGS. 1 to 6)]
The configuration and operation of an embodiment for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating the overall configuration of a piston for an internal combustion engine (hereinafter, piston 10) according to the first embodiment. FIG. 2 is a cross-sectional view as seen from the II-II direction in FIG.

  In the figure in which the X axis, the Y axis, and the Z axis are described, the X axis, the Y axis, and the Z axis are orthogonal to each other. As shown in FIG. 1, the X-axis direction is along the axial direction of the piston pin hole PH, and the Z-axis direction is the axial direction of the piston 10 from the skirt portion of the piston 10 toward the head H of the piston 10. is there. In the Y-axis direction, the direction from the axis JK of the piston 10 to the outlet 14 is defined as the Y-axis direction.

  In the stroke direction in which the piston 10 reciprocates in a cylinder (not shown), the direction of the head H of the piston 10 with respect to the oil passage 20a (20) is set to the upward direction (Z-axis direction), and the opposite direction. Is defined as a downward direction (a direction opposite to the Z-axis direction).

  As shown in FIG. 1, the piston 10 is a piston for an internal combustion engine, and an oil passage 20 a through which cooling oil flows is formed inside the piston 10.

  The oil passage 20 a has an inflow port 12 through which oil flows in and an outflow port 14 through which oil flows out, and is formed in the circumferential direction of the piston 10. A first recess 22a and a second recess 24a are provided on the inner wall surface of the oil passage 20a (see FIGS. 3 and 5). As shown in FIG. 2, the cross section of the oil passage 20a orthogonal to the central axis CK of the oil passage 20a is an ellipse, and the direction of the major axis LD of the ellipse is in the stroke direction (Z-axis direction). (See FIGS. 2, 4, and 6). As shown in FIG. 1, the oil that has flowed into the inflow port 12 flows through the oil passage 20 a in a path in each of the clockwise direction Dck and the counterclockwise direction Duk of the axis JK of the piston 10, It is discharged from the outlet 14.

● [Detailed description of movement of oil in oil passage 20a (FIGS. 2 to 6)]
The movement of the oil in the oil passage 20a associated with the vertical reciprocation of the piston 10 (see FIG. 1) will be described in detail with reference to FIGS.

  FIG. 3 is an enlarged schematic diagram illustrating details of a surface indicated by a region S1 viewed from the direction III in FIG. FIG. 4 is a schematic diagram of a cross section of the oil passage 20a for explaining the movement of oil in the oil passage 20a accompanying the movement of the piston 10 from above to below. Note that, in FIG. 3, an arrow Af indicates a direction from the inlet 12 to the outlet 14.

  As shown in FIG. 3, the first recess 22 a is formed in a part of the first oil guide surface ML <b> 1 (see FIG. 4) so as to extend linearly upward from below so as to be inclined toward the outlet 14. Are provided at predetermined intervals. The inclination and the predetermined interval are determined based on the shape of the first recess 22a, the cross section of the oil passage 20a, and the like.

  In FIG. 3, the first recess 22a is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20a. In the first concave portion 22a, a thin solid line indicates a bottom portion of the V-shaped groove, and a thick solid line indicates an open edge of the V-shaped groove.

  As shown in FIGS. 2 and 4, the first oil guide surface ML1 is vertically divided by a conical surface EM passing through the central axis CK of the oil passage 20a and having a major axis LD indicated by a dashed line passing through the central axis CK as a generating line. In this case, the inner wall surface is located on the upper side in the stroke direction of the oil passage 20a (the inner wall surface indicated by the region RL1 in the oil passage 20a). In FIG. 4, the first recess 22a and the second recess 24a are omitted for simplicity of description. The arrow APdn indicates a state in which the piston 10 reaches the uppermost position in the stroke direction from below and moves downward. A hatched portion in the oil passage 20a represents oil.

  As shown in FIG. 4, when the piston 10 moves upward from below in the stroke direction, the oil receives a downward inertial force and moves to the bottom of the oil passage 20a. When the piston 10 reaches the uppermost position in the stroke direction and starts moving downward, the oil moved to the bottom of the oil passage 20a receives an upward inertial force.

  When the oil receives an upward inertial force, the oil moves upward from the bottom of the oil passage 20a as shown by the arrow, and moves to the first oil guide surface ML1.

  The oil moved to the first oil guide surface ML1 receives an upward inertial force until the piston 10 reaches the lowest position in the stroke direction, and the direction indicated by the arrow AUp along the first concave portion 22a (see FIG. 3). Moved to

  In FIG. 3, for example, when the oil is moved by a distance Du along the first concave portion 22a under the upward inertia force, the oil is moved upward by a distance corresponding to the distance Dm1, and 12 is moved in the direction of the outlet 14 by a distance corresponding to the distance Df1.

  FIG. 5 is an enlarged schematic diagram illustrating details of a surface indicated by a region S2 viewed from the V direction in FIG. FIG. 6 is a schematic diagram of a cross section of the oil passage 20a illustrating the movement of oil in the oil passage 20a accompanying the movement of the piston 10 from below to above. In FIG. 5, an arrow Af indicates a direction from the inflow port 12 to the outflow port 14.

  As shown in FIG. 5, the second recess 24a is formed in a part of the second oil guide surface ML2 (see FIG. 6) so as to extend linearly from top to bottom so as to be inclined toward the outlet 14 side. Are provided at predetermined intervals. The inclination and the predetermined interval are determined based on the shape of the second concave portion 24a, the cross-sectional shape of the oil passage 20a, and the like.

  In FIG. 5, the second recess 24a is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20a. In the second recess 24a, a thin solid line indicates the bottom of the V-shaped groove, and a thick solid line indicates the edge of the V-shaped groove on the open side. When the piston 10 is manufactured by casting, the first concave portion 22a and the second concave portion 24a have, for example, convex shapes corresponding to the first concave portion 22a and the second concave portion 24a in a salt core for forming the oil passage 20a. It may be formed by providing a part.

  As shown in FIGS. 2 and 6, the second oil guide surface ML2 is vertically divided by a conical surface EM passing through the central axis CK of the oil passage 20a and having a major axis LD indicated by a dashed line passing through the central axis CK as a generating line. This is the inner wall surface on the lower side in the stroke direction of the oil passage 20a in the case of the above (the inner wall surface indicated by the region RL2 in the oil passage 20a). In FIG. 6, the first concave portion 22a and the second concave portion 24a are omitted for the sake of simplicity. The arrow APup indicates a state in which the piston 10 reaches the lowest position in the stroke direction from above and moves upward. A hatched portion in the oil passage 20a represents oil.

  When the piston 10 moves downward from above in the stroke direction, the oil receives an upward inertial force and moves to the ceiling of the oil passage 20a. When the piston 10 reaches the lowest position in the stroke direction and starts moving upward, the oil moved to the ceiling portion of the oil passage 20a receives a downward inertial force.

  When the oil receives a downward inertial force, the oil moves downward from the ceiling of the oil passage 20a as shown by the arrow, and moves to the second oil guide surface ML2.

  The oil moved to the second oil guide surface ML2 receives a downward inertial force until the piston 10 reaches the uppermost position in the stroke direction, and moves along the second recess 24a (see FIG. 5) in the direction indicated by the arrow Adn. Be moved.

  In FIG. 5, for example, when the oil is moved by the distance Dd along the second concave portion 24a under the downward inertial force, the oil is moved downward by the distance corresponding to the distance Dm2, and 12 is moved in the direction of the outlet 14 by a distance corresponding to the distance Df2.

  In the internal combustion engine piston of the first embodiment, when the piston 10 moves downward from above, the oil is moved a distance Df1 from the inlet 12 to the outlet 14 and the piston 10 moves upward from below. When it moves toward, the distance Df2 is moved from the inflow port 12 to the outflow port 14. In this manner, the kinetic energy of the oil accompanying the reciprocating motion of the piston 10 in the cylinder can be efficiently converted into the kinetic energy moving (distance Df1 + distance Df2) from the inlet 12 to the outlet 14 in the oil passage 20a. As a result, the amount of oil moving from the inlet 12 to the outlet 14 in the oil passage 20a increases, so that the amount of oil staying near the inlet 12 in the oil passage 20a decreases, and the movement of the piston 10 decreases. When the downward inertial force acts on the oil, the oil flowing backward from the inflow port 12 to the outside of the piston 10 is reduced, the oil flow rate passing through the oil passage 20a is improved, and the cooling efficiency of the piston is improved. it can.

  Further, the first oil guide surface ML1 and the second oil guide surface ML2 are formed on a surface having a small curvature along the major axis LD direction, and the resistance received from the surface can be made smaller than that of the surface having a large curvature. At this time, the kinetic energy of the oil can be efficiently converted by the kinetic energy moving from the inlet 12 to the outlet 14.

● [Configuration and operation of oil passage 20b in the second embodiment (FIGS. 7 and 8)]
The piston for an internal combustion engine according to the second embodiment is different from the piston according to the first embodiment in that the oil passage 20a (see FIG. 2) having an oval cross section is an oil passage 20b (20) having a circular cross section. I do. Hereinafter, differences between the oil passage 20b and the oil passage 20a will be described in detail.

  FIG. 7 is a perspective view illustrating an oil passage 20b according to the second embodiment, and shows an example of the oil passage in the area AA in FIG. 1 when the cross section is a circle. FIG. 8 is a diagram illustrating a cross section viewed from the VIII direction in FIG. In FIG. 7, an arrow Af indicates a direction from the inflow port 12 to the outflow port 14.

  As shown in FIGS. 7 and 8, the oil passage 20b is formed by a first oil guide surface M1 and a second oil guide surface M2. The first oil guide surface M1 is an inner wall surface on the upper side in the stroke direction of the oil passage when the oil passage 20b is vertically divided by a plane HM1 passing through the center axis CKa of the oil passage 20b and orthogonal to the stroke direction. The second oil guide surface M2 is an inner wall surface that is the lower side in the stroke direction of the oil passage 20b when divided vertically into a plane HM1 that passes through the central axis CKa of the oil passage 20b and is orthogonal to the stroke direction.

  As shown in FIG. 8, the first oil guide surface M1 includes a surface M1b (an inner wall surface indicated by a region R1b) and a surface M1a (an inner wall surface indicated by a region R1a). As shown in FIGS. 7 and 8, the surface M1b passes through the central axis CKa of the oil passage 20b, and is divided by a cylindrical surface HM2 parallel to the stroke direction. The piston 10 on the first oil guide surface M1 (see FIG. 1). ) Is the radially inner surface. The surface M1a is a radially outer surface of the piston 10 on the first oil guide surface M1 when divided by a cylindrical surface HM2 which passes through the central axis CKa of the oil passage 20b and is parallel to the stroke direction. As shown in FIG. 8, the second oil guide surface M2 includes a surface M2b (an inner wall surface indicated by a region R2b) and a surface M2a (an inner wall surface indicated by a region R2a). As shown in FIGS. 7 and 8, the surface M2b passes through the center axis CKa of the oil passage 20b and is divided by a cylindrical surface HM2 parallel to the stroke direction. The piston 10 on the second oil guide surface M2 (see FIG. 1). ) Is the radially inner surface. The surface M2a is a radially outer surface of the piston 10 in the second oil guide surface M2 when divided by a cylindrical surface HM2 which passes through the central axis CKa of the oil passage 20b and is parallel to the stroke direction.

  As shown in FIG. 7, the first recess 22b extends linearly upward from below so as to incline toward the outlet 14 in each of the surfaces M1a and M1b in the first oil guide surface M1. They are provided at predetermined intervals. Note that the inclination and the predetermined interval are determined based on the shape of the first recess 22b, the cross-sectional shape of the oil passage 20b, and the like.

  The second concave portions 24b are provided at predetermined intervals so as to extend linearly from top to bottom so as to be inclined toward the outlet 14 side in each of the surface M2a and the surface M2b in the second oil guide surface M2. I have. The inclination and the predetermined interval are determined based on the shape of the second recess 24b, the cross-sectional shape of the oil passage 20b, and the like.

  The first concave portion 22b and the second concave portion 24b are formed as V-shaped grooves on the inner wall surface of the oil passage 20b, for example. The second recess 24b is not limited to being provided in the oil passage 20b so as to face the first recess 22b along the direction in which the oil flows, and may be provided at positions not facing each other.

  In FIG. 7, when the movement of the piston 10 (see FIG. 1) changes from upward stroke to downward stroke, the oil moves along the first recess 22b in each of the surface M1a and the surface M1b (see FIG. 8) for a distance Du1a, Du1b. The respective distances are moved, and the respective distances Df1a and Df1b are moved from the inlet 12 to the outlet 14 respectively. Further, when the movement of the piston 10 changes from downward stroke to upward stroke, the oil is moved along the second recess 24b on each of the surfaces M2a and M2b (see FIG. 8) by the distances Dd2a and Dd2b, respectively. The respective distances Df2a and Df2b are moved from the inlet 12 to the outlet 14 respectively.

  In the piston for an internal combustion engine of the second embodiment, a first concave portion 22b is provided on the entire first oil guide surface M1 in the circumferential direction, and a second concave portion 24b is provided on the entire second oil guide surface M2 in the circumferential direction. Therefore, the oil can be more efficiently moved from the inlet 12 to the outlet 14.

● [Configuration and Operation of Oil Passage 20c and Oil Passage 20d in Third Embodiment (FIGS. 9 and 10)]
The piston for an internal combustion engine according to the third embodiment differs from the piston according to the second embodiment in that the first inner surface M1b and the second outer surface M2b of the piston 10 (see FIG. 1) and the first outer surface M1a and M2a respectively correspond to the first surface. The oil passage 20b having the concave portion 22b and the second concave portion 24b (see FIGS. 7 and 8) is formed on the radially inner surface M1b and the radially outer surface M1a of the piston 10 in the first oil guide surface M1. The difference is that the oil passage 20c (20) is provided with only the first recess 22c. Further, the piston for an internal combustion engine of the third embodiment is different from the oil passage 20b of the second embodiment in that a radially inner surface M2b and a radially outer surface M2a of the piston 10 in the second oil guide surface M2 are provided. Are different from each other in that they are oil passages 20d (20) in which only the second recess 24d is provided. Hereinafter, differences between the oil passage 20c and the oil passage 20d and the oil passage 20b will be described in detail.

  FIG. 9 is a perspective view illustrating an oil passage 20c according to the third embodiment, which is an oil passage in a region AA in FIG. An example in which only one recess 22c is formed is shown. FIG. 10 is a perspective view illustrating an oil passage 20d according to the third embodiment, which is an oil passage in an area AA in FIG. 1, the oil passage having a circular cross section, and the second oil guide surface M2. An example in which only the two concave portions 24d are formed is shown. The arrow Af indicates the direction from the inlet 12 to the outlet 14.

  As shown in FIG. 9, the oil passage 20c is formed by a first oil guide surface M1 and a second oil guide surface M2 (see FIG. 8). As shown in FIG. 10, the oil passage 20d is formed by a first oil guide surface M1 and a second oil guide surface M2 (see FIG. 8).

  As shown in FIG. 9, the first concave portion 22c has a linear shape from bottom to top so as to be inclined toward the outflow port 14 on each of the surface M1a and the surface M1b (see FIG. 8) in the first oil guide surface M1. Are provided at predetermined intervals so as to extend. Note that the inclination and the predetermined interval are determined based on the shape of the first recess 22c, the cross-sectional shape of the oil passage 20c, and the like.

  As shown in FIG. 10, the second concave portion 24d has a linear shape from top to bottom so as to be inclined toward the outflow port 14 on each of the surface M2a and the surface M2b (see FIG. 8) in the second oil guide surface M2. Are provided at predetermined intervals so as to extend. The inclination and the predetermined interval are determined based on the shape of the second recess 24d, the cross-sectional shape of the oil passage 20d, and the like.

  The first recess 22c is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20c. The second recess 24d is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20d.

  In FIG. 9, when the movement of the piston 10 (see FIG. 1) changes from upward stroke to downward stroke, the oil moves along the first concave portion 22c in each of the surface M1a and the surface M1b (see FIG. 8) for a distance Du1a, Du1b. They are moved by the respective distances, and are moved by the respective distances Df1a and Df1b from the inlet 12 to the outlet 14. In FIG. 10, when the movement of the piston 10 changes from downward stroke to upward stroke, the oil travels along the second recess 24d on each of the surfaces M2a and M2b (see FIG. 8), and the respective distances Dd2a and Dd2b. Are moved from the inflow port 12 to the outflow port 14 by the respective distances Df2a and Df2b.

  In the piston for an internal combustion engine according to the third embodiment, the first concave portion 22c is provided in the entire circumferential direction on the first oil guide surface M1, or the second concave portion 24d is provided in the entire circumferential direction on the second oil guide surface M2. Therefore, the configuration can be simpler than that of the second embodiment.

● [Configuration and Operation of Oil Passage 20e in Fourth Embodiment (FIG. 11)]
The piston for an internal combustion engine according to the fourth embodiment differs from the piston according to the second embodiment in that first and second radially inner surfaces M1b and M2b and first and second radially outer surfaces M1a and M2a of the piston 10 (see FIG. 1) are provided. The oil passage 20b in which each of the concave portion 22b and the second concave portion 24b is provided (see FIGS. 7 and 8) is provided on each of the first oil guide surface M1 and the second oil guide surface M2 on the radial outside of the piston 10. The difference is that the oil passage 20e (20) is provided with the first concave portion 22e and the second concave portion 24e only on the surfaces M1a and M2a. Hereinafter, differences between the oil passage 20e and the oil passage 20b will be described in detail.

  FIG. 11 is a perspective view illustrating an oil passage 20e according to the fourth embodiment, and shows an example of the oil passage in the area AA in FIG. 1 when the cross section is a circle. The arrow Af indicates the direction from the inlet 12 to the outlet 14.

  As shown in FIG. 11, the oil passage 20e is formed by a first oil guide surface M1 and a second oil guide surface M2 (see FIG. 8).

  As shown in FIG. 11, the first concave portion 22 e extends linearly from bottom to top so as to incline toward the outlet 14 on the surface M1 a (see FIG. 8) of the first oil guide surface M1. They are provided at predetermined intervals. Note that the inclination and the predetermined interval are determined based on the shape of the first recess 22e, the cross-sectional shape of the oil passage 20e, and the like.

  The second concave portions 24e are provided at predetermined intervals so as to extend linearly from top to bottom so as to be inclined toward the outlet 14 side on a surface M2a (see FIG. 8) of the second oil guide surface M2. I have. Note that the inclination and the predetermined interval are determined based on the shape of the second recess 24e, the cross-sectional shape of the oil passage 20e, and the like.

  The first recess 22e is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20e. The second recess 24e is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20e. The second recess 24e is not limited to being provided in the oil passage 20e so as to face the first recess 22e along the direction in which the oil flows, and may be provided at positions not facing each other. good.

  In FIG. 11, the oil is moved by the distance Du1a along the first concave portion 22e on the surface M1a (see FIG. 8) by moving the piston 10 (see FIG. 1) from the upper side to the lower side in the stroke direction. It is moved from the inlet 12 to the outlet 14 by a distance of Df1a. Further, the oil is moved by a distance Dd2a along the second recess 24e in the surface M2a (see FIG. 8) by moving the piston 10 from the lower side to the upper side in the stroke direction. To the outlet 14.

  In the piston for an internal combustion engine according to the fourth embodiment, a first concave portion 22e is provided on a radially outer surface M1a of the piston 10 on the first oil guide surface M1, and a diameter of the piston 10 on the second oil guide surface M2 is provided. Since the second concave portion 24e is provided on the surface M2a on the outer side in the direction (see FIG. 8), the configuration can be simpler than in the second embodiment.

● [Configuration and Operation of Oil Passage 20f in Fifth Embodiment (FIG. 12)]
The internal combustion engine piston according to the fifth embodiment is different from the second embodiment in that the radially inner surfaces M1b and M2b and the radially outer surfaces M1a and M2a of the piston 10 (see FIG. An oil passage 20b provided with each of the concave portion 22b and the second concave portion 24b is provided (see FIGS. 7 and 8), and a first concave portion 22f is provided on a radially outer surface M1a of the piston 10 in the first oil guide surface M1. The second oil guide surface M2 is different from the second oil guide surface M2 in that an oil passage 20f (20) is provided with a second recess 24f in a radially inner surface M2b. Hereinafter, differences between the oil passage 20f and the oil passage 20b will be described in detail.

  FIG. 12 is a perspective view illustrating an oil passage 20f according to the fifth embodiment, and shows an example of the oil passage in the area AA in FIG. 1 when the cross section is a circle. The arrow Af indicates the direction from the inlet 12 to the outlet 14.

  As shown in FIG. 12, the first concave portion 22f is linearly formed from the bottom to the top so as to incline toward the outlet 14 side on the radially outer surface M1a (see FIG. 8) of the first oil guide surface M1. They are provided at predetermined intervals so as to extend. Note that the inclination and the predetermined interval are determined based on the shape of the first recess 22f, the cross-sectional shape of the oil passage 20f, and the like.

  The second recess 24f has a predetermined interval so as to extend linearly from top to bottom so as to incline toward the outlet 14 side on a radially inner surface M2b (see FIG. 8) of the second oil guide surface M2. It is provided in. Note that the inclination and the predetermined interval are determined based on the shape of the second recess 24f, the cross section of the oil passage 20f, and the like.

  The first recess 22f is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20f. The second recess 24f is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20f. The second recess 24f is not limited to being provided in the oil passage 20f so as to face the first recess 22f along the direction in which the oil flows, and may be provided at positions not facing each other. good.

  In FIG. 12, when the movement of the piston 10 (see FIG. 1) changes from upward stroke to downward stroke, the oil is moved by the distance Du1a along the first recess 22f on the surface M1a (see FIG. 8), and the distance Df1a Is moved from the inlet 12 to the outlet 14. Further, when the movement of the piston 10 changes from downward stroke to upward stroke, the oil is moved by the distance Dd2b along the second concave portion 24e on the surface M2b (see FIG. 8), and is moved from the inlet 12 by the distance Df2b. It is moved toward the outlet 14.

  In the piston for an internal combustion engine according to the fifth embodiment, a first concave portion 22f is provided in a radially outer surface M1a of the piston 10 in the first oil guide surface M1, and a diameter of the piston 10 in the second oil guide surface M2 is provided. Since the second concave portion 24f is provided on the surface M2b on the inner side in the direction (see FIG. 8), the configuration can be simpler than in the second embodiment.

● [Configuration and Operation of Oil Passage 20g in Sixth Embodiment (FIG. 13)]
In the second, fourth and fifth embodiments, the piston for an internal combustion engine according to the sixth embodiment has the first concave portions (22b, 22e, 22f) of the first oil guide surface M1 and the second concave portions of the second oil guide surface M2. The two recesses (24b, 24e, 24f) are arranged so as to face each other (see FIGS. 7, 11, and 12), but differ from the sixth embodiment in that they are arranged at positions not facing each other. I do. Hereinafter, differences between the oil passage 20g and the oil passage 20b will be described in detail.

  FIG. 13 is a perspective view illustrating an oil passage 20g according to the sixth embodiment, and shows an example of the oil passage in the area AA in FIG. 1 when the cross section is a circle. The arrow Af indicates the direction from the inlet 12 to the outlet 14.

  The oil passage 20g according to the sixth embodiment is different from the oil passage 20b according to the second embodiment at a predetermined interval along the direction from the inlet 12 to the outlet 14 with the first recess 22g. The difference is that the two concave portions 24g are provided alternately. The predetermined intervals are determined based on the shapes of the first recess 22g and the second recess 24g, the cross-sectional shape of the oil passage 20g, and the like.

  The first recess 22g is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20g. The second recess 24g is formed, for example, as a V-shaped groove on the inner wall surface of the oil passage 20g.

  In FIG. 13, when the movement of the piston 10 (see FIG. 1) changes from upward stroke to downward stroke, the oil is moved along the first concave portion 22g by the respective distances Du1a and Du1b, and the oil is moved by the distances Df1a and Df1b. The respective distances are moved from the inlet 12 to the outlet 14, respectively. When the movement of the piston 10 changes from downward stroke to upward stroke, the oil is moved along the second recess 24g by the distances Dd2a and Dd2b, and flows from the inlet 12 through the distances Df2a and Df2b respectively. Each is moved toward the exit 14.

  In the piston for an internal combustion engine according to the sixth embodiment, the first concave portion 22g is provided in the entire circumferential direction on the first oil guide surface M1, or the second concave portion 24g is provided in the entire circumferential direction on the second oil guide surface M2. Since they are provided alternately at predetermined intervals, the number of the first concave portions 22b and the number of the second concave portions 24b (see FIG. 7) in the second embodiment are smaller, so that a simpler configuration can be achieved.

● [Configuration and Operation of Oil Passage 20h in Seventh Embodiment (FIG. 14)]
In the piston for an internal combustion engine according to the seventh embodiment, in the first embodiment, the oil passage 20a in which the first concave portion 22a and the second concave portion 24a are provided discontinuously is formed by the first convex portion 22h and the second convex portion. The difference is that the portion 24h is a continuous spiral oil passage 20h (20). Hereinafter, differences between the oil passage 20h and the oil passage 20a will be described in detail.

  FIG. 14 is a perspective view illustrating an oil passage 20h according to the seventh embodiment, which is an oil passage in a region AA in FIG. 1 and has an oval cross section (first embodiment). Another example is shown. The arrow Af indicates the direction from the inlet 12 to the outlet 14.

  As shown in FIG. 14, the oil passage 20h has a first oil guide surface ML1, which is an inner wall surface on the upper surface, and a second oil guide surface, which is an inner wall surface on the lower surface, similarly to the oil passage 20a of the first embodiment. ML2 (see FIGS. 4 and 6).

  The oil passage 20h is different from the oil passage 20a in that a first convex portion 22h and a second convex portion 24h are provided instead of the first concave portion 22a and the second concave portion 24a. Further, the first convex portion 22h and the second convex portion 24h are formed in a continuous spiral shape and are integrally formed as a convex portion 29. The convex portion 29 is formed, for example, by projecting in an inverted V-shape on the inner wall surface of the oil passage 20h. Alternatively, the protrusion 29 (the first protrusion 22h and the second protrusion 24h) is formed of a spiral member that is a separate member, and is disposed in the oil passage 20h.

  The first oil guide surface ML1 is a surface on the upper side in the stroke direction with respect to the long diameter LD, and the second oil guide surface ML2 is a surface on the lower side in the stroke direction with respect to the long diameter LD.

  The first convex portions 22h indicated by solid lines are provided at predetermined intervals so as to extend linearly from bottom to top so as to incline toward the outlet 14 side on the first oil guide surface ML1. The second convex portions 24h indicated by two-dot chain lines are provided at predetermined intervals so as to extend linearly from top to bottom so as to incline toward the outlet 14 side on the second oil guide surface ML2. Have been.

  In FIG. 14, when the movement of the piston 10 (see FIG. 1) changes from upward stroke to downward stroke, the oil is moved by a distance Du1s along the first convex portion 22h, and is moved by a distance Df1s to the inlet 12 respectively. To the outlet 14. When the movement of the piston 10 changes from downward stroke to upward stroke, the oil is moved along the second convex portion 24h by the distance Dd2s, and the oil is moved by the distance Df2s from the inlet 12 to the outlet 14 respectively. Be moved.

  In the piston for an internal combustion engine of the seventh embodiment, the first protrusion 22h and the second protrusion 24h are formed continuously and integrally on the inner wall surface of the oil passage 20h. The inside is smoothly moved from the inlet 12 to the outlet 14 (see FIG. 1). When the first protrusion 22h and the second protrusion 24h are formed as separate members and provided, the thermal conductivity of the material forming the first protrusion 22h and the second protrusion 24h is determined by the oil passage 20h (piston). 10) It can be higher than the thermal conductivity of the material forming the. Thereby, heat transfer from the piston 10 to the first protrusion 22h and the second protrusion 24h and heat transfer from the first protrusion 22h and the second protrusion 24h to the oil can be promoted, and cooling in the piston 10 can be promoted. Efficiency can be further improved.

● [Configuration of Oil Passage 20 in Other Embodiments (FIGS. 15 to 17)]
A configuration example of the oil passage 20 of another embodiment will be described with reference to FIGS.

  FIG. 15 is a cross-sectional view illustrating an oil passage 20m (20) formed by a salt core in the piston 10m (10). The first convex portion and the second convex portion are formed by providing concave portions corresponding to the first convex portion and the second convex portion in a salt core for forming the oil passage 20m in the production of the piston 10m by casting. Is done.

  FIG. 16 is a cross-sectional view illustrating the oil passage 20n (20) when the convex portion 29b (corresponding to the first convex portion and the second convex portion) formed of a spiral member is a separate member.

  The convex portion 29b is disposed in the oil passage 20n by enclosing the spiral member in the oil passage core and casting the piston 10n when manufacturing the piston 10n (10). The projection 29b has a right-handed spiral on the right side of the axis JK and a left-handed spiral on the left side of the axis JK on the paper surface of FIG.

  FIG. 17 is a cross-sectional view illustrating the oil passage 20p (20) in a case where the cross section of the oil passage in which the first convex portion and the second convex portion are formed is neither an ellipse nor a circle (substantially triangular in the example of FIG. 17). FIG. The cross section of the oil passage 20p in the piston 10p (10) may be, for example, a triangular shape arranged so that the bottom portion is downward. Further, the oil passage 20p having the above-mentioned cross section may be provided not in a piston formed of a divided member but in a piston formed integrally.

● [Effects of the present application]
As described above, the piston for an internal combustion engine according to the invention of the present application can efficiently convert the kinetic energy of oil accompanying the reciprocating motion of the piston in the cylinder into the kinetic energy for moving the oil from the inlet to the outlet in the oil passage. . As a result, the amount of oil that moves from the inlet to the outlet in the oil passage increases, so that the amount of oil remaining near the inlet 12 in the oil passage 20a decreases, and the oil moves with the movement of the piston 10. When the downward inertial force acts on the oil, the amount of oil flowing backward from the inflow port 12 to the outside of the piston decreases, the oil flow rate passing through the oil passage increases, and the cooling efficiency of the piston can be improved (FIG. 1). reference).

  The piston for an internal combustion engine of the present invention is not limited to the configuration, structure, and the like described in the present embodiment, and various changes, additions, and deletions can be made without changing the gist of the present invention.

  In the description of the embodiment, the cross section of the oil passage has been described as an ellipse or a circle. However, the cross section is not limited thereto, and may be any shape as long as at least one of the first oil guide surface and the second oil guide surface can be formed. . For example, a cross section of the oil passage may be a half circle or a half of an ellipse in a major axis or a minor axis.

  In the first to sixth embodiments (see FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 to FIG. 13), instead of the first concave portions (22a, 22b, 22c, 22e, 22f, 22g), You may provide a 1st convex part. A second convex portion may be provided instead of the second concave portion (24a, 24b, 24d, 24e, 24f, 24g). In this case, the first convex portion and the second convex portion may be formed by, for example, projecting in an inverted V-shape on the inner wall surface of the oil passage (20a, 20b, 20c, 20d, 20e, 20f, 20g). .

  Further, in the description of the embodiment, the first concave portion and the second concave portion have been described using the V-shaped grooves, but may have any shape provided in a concave shape on the inner wall surface of the oil passage. The first convex portion and the second convex portion are not limited to be formed by projecting in an inverted V-shape, and may be any shapes provided in a convex shape on the inner wall surface of the oil passage. The present invention is not limited to the combination of the first concave portion and the second concave portion, but may be a combination of the first concave portion and the second convex portion, a combination of the first convex portion and the second concave portion, or a combination of the first convex portion and the second convex portion. These combinations may be the same in the entire oil passage or may differ depending on the location.

  In the first to sixth embodiments (see FIGS. 3, 5, 7 and 9 to 13), the first concave portion (or the first convex portion) and the second concave portion (or the second convex portion) They may be provided at equal intervals or at different intervals. In the first to sixth embodiments, the first concave portion (or the first convex portion) and the second concave portion (or the second convex portion) have been described as an example in which a plurality of the first concave portions (or the second convex portions) are provided. 20b, 20c, 20d, 20e, 20f, and 20g), at least one is provided in each of the paths (see FIG. 1) in the clockwise direction Dck and the counterclockwise direction Duk of the axis JK of the piston 10 in each direction. I just want to. The predetermined interval at which the first concave portion (or the first convex portion) is provided and the predetermined interval at which the second concave portion (or the second convex portion) is provided may be the same or different.

  In the fourth embodiment (see FIG. 11), the first concave portion 22e is inclined toward the outlet 14 from the bottom to the top on the radially inner surface M1b (see FIG. 8) of the first oil guide surface M1. Thus, they may be provided at predetermined intervals. The second concave portion 24e extends linearly downward from above from the surface M2b (see FIG. 8) radially inside the second oil guide surface M2 of the oil passage 20e so as to incline toward the outlet 14 side. May be provided at predetermined intervals.

  In the fifth embodiment (see FIG. 12), the first concave portion 22f extends linearly upward from below so as to incline toward the outlet 14 side on the surface M1b (see FIG. 8) of the oil passage 20f. May be provided at predetermined intervals. The second concave portions 24f may be provided at predetermined intervals on the surface M2a (see FIG. 8) of the oil passage 20f so as to extend linearly from top to bottom so as to be inclined toward the outlet 14 side.

10, 10m piston (piston for internal combustion engine)
10n, 10p piston (piston for internal combustion engine)
12 Inlet 14 Outlet 20 Oil passage 20a, 20b, 20c Oil passage 20d, 20e, 20f Oil passage 20g, 20h Oil passage 22a, 22b, 22c First recess 22e, 22f First recess 22g First recess 22h First protrusion Part 24a, 24b Second concave part 24d, 24e, 24f Second concave part 24g Second concave part 24h Second convex part 29, 29b Convex part M1, ML1 First oil guiding surface M2, ML2 Second oil guiding surface M1a, M1b Surface M2a , M2b surface LD long diameter H head CK, CKa center axis JK axis Dck clockwise direction Duk counterclockwise direction EM conical surface HM1 plane HM2 cylindrical surface RL1, RL2 region R1a, R1b region R2a, R2b region S1, D2 region , Dm2, Df2 distance Du1a, Df1a distance Du b, DF1B distance Dd2a, Df2a distance Dd2b, Df2b distance Af arrow APdn, APup arrow PH piston pin hole 110 the piston body 120 cooling cavity 212 inlet passage 214 outlet passage

Claims (5)

A piston for an internal combustion engine,
An oil passage for circulating cooling oil is formed inside the piston,
The oil passage,
It has an inflow port for inflowing oil and an outflow port for outflow, and is formed in the circumferential direction of the piston,
In the stroke direction of reciprocating the piston in the cylinder, when the direction of the head side of the piston with respect to the oil passage is an upward direction, and the opposite direction is a downward direction,
The outflow port is provided on at least a part of a first oil guide surface, which is an inner wall surface on the stroke direction upper side of the oil passage when the oil passage is vertically divided on a plane passing through the center axis of the oil passage and orthogonal to the stroke direction. A first concave portion or a first convex portion linearly extending upward from below so as to incline toward the side,
At least a portion of a second oil guide surface, which is an inner wall surface on the stroke direction lower side of the oil passage when the oil passage is vertically divided on a plane orthogonal to the stroke direction, passing through the center axis of the oil passage. A second concave portion or a second convex portion extending linearly from top to bottom so as to be inclined toward the outlet side;
At least one of which is provided,
Piston for internal combustion engine. The piston for an internal combustion engine according to claim 1,
The first concave portion, or the first convex portion,
A radially inner surface of the piston in the first oil guide surface when divided by a cylindrical surface parallel to the stroke direction, passing through the central axis of the oil passage;
A radially outer surface of the piston in the first oil guide surface when divided by a cylindrical surface parallel to the stroke direction, passing through the central axis of the oil passage;
It is provided in,
The second concave portion, or the second convex portion,
A radially inner surface of the piston in the second oil guide surface when divided by a cylindrical surface parallel to the stroke direction, passing through the central axis of the oil passage;
A radially outer surface of the piston in the second oil guide surface when divided by a cylindrical surface parallel to the stroke direction, passing through the central axis of the oil passage;
Provided in the
Piston for internal combustion engine. A piston for an internal combustion engine,
An oil passage for circulating cooling oil is formed inside the piston,
The oil passage,
It has an inflow port for inflowing oil and an outflow port for outflow, and is formed in the circumferential direction of the piston,
In the stroke direction of reciprocating the piston in the cylinder, when the direction of the head side of the piston with respect to the oil passage is an upward direction, and the opposite direction is a downward direction,
The cross section of the oil passage orthogonal to the center axis of the oil passage is an oval, and the direction of the major axis of the oval is inclined with respect to the stroke direction,
A first oil guide surface that is an inner wall surface that is the upper side in the stroke direction of the oil passage when the oil passage is vertically divided by a conical surface having the major axis passing through the center axis and a base line passing through the center axis of the oil passage. A first concave portion or a first convex portion extending linearly from bottom to top so as to be inclined toward the outlet side at least in part;
A second oil guide surface that is an inner wall surface that is lower in the stroke direction of the oil passage when the oil passage is vertically divided by a conical surface that passes through the center axis of the oil passage and has the major axis passing through the center axis and that is a generating line; A second concave portion or a second convex portion extending linearly from top to bottom so as to be inclined toward the outlet side at least in part of the second concave portion or the second convex portion;
At least one of which is provided,
Piston for internal combustion engine. The piston for an internal combustion engine according to claim 3, wherein
The first concave portion and the second concave portion, or the first convex portion and the second convex portion,
It is formed as a continuous spiral and integrally formed,
Piston for internal combustion engine. The piston for an internal combustion engine according to claim 4, wherein
The first convex portion and the second convex portion are configured by a spiral member that is a separate member from the piston,
The spiral member is arranged in the oil passage,
Piston for internal combustion engine.

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