WO2015198434A1

WO2015198434A1 - Piston for internal combustion engine

Info

Publication number: WO2015198434A1
Application number: PCT/JP2014/066938
Authority: WO
Inventors: 理晴葛西; 洋孝赤松
Original assignee: 日産自動車株式会社
Priority date: 2014-06-26
Filing date: 2014-06-26
Publication date: 2015-12-30

Abstract

The present invention is a piston for an internal combustion engine (1) that comprises: a piston body (11); an oil ring groove (115) formed on the outer peripheral surface of a crown portion (111) of the piston body; a cooling channel (17) formed along the circumferential direction of the piston body in the interior of the piston body; and drain holes (2) that connect the concave surface of the oil cylinder groove to the inner surface of the piston body; and introduces, from an inlet passage (17A) in the cooling channel, a cooling oil that is injected toward the inner surface of the piston body from the lower portion of the internal combustion engine cylinder and discharges the cooling oil out of an outlet passage (17B), wherein the drain holes (2) are provided in a position avoiding the inlet passage (17A) and the outlet passage (17B).

Description

Piston for internal combustion engine

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

In a conventional internal combustion engine, cooling oil is sprayed from the lower part of the cylinder toward the inner surface of the piston, thereby cooling the piston. In this type of internal combustion engine, the injected cooling oil collides with the inner surface of the piston and enters the oil draining hole while flowing down along the inner surface, and flows back through the oil draining hole and the oil ring groove. May burn. In order to prevent this problem, an oil gallery communicating with the bottom of the oil ring groove of the piston via the oil drain hole is formed inside the piston, and oil relief holes provided at both ends of the oil gallery are formed on the piston. A piston is known which is opened on the inner surface at a position where it does not interfere with the cooling oil injected by the oil jet nozzle (see “oil gallery 16” in FIGS. 1 to 3 of Patent Document 1).

Japanese Utility Model Publication No. 63-96221

However, as in the conventional piston, in order to form an oil gallery in the piston along the oil ring groove, it is necessary to increase the thickness of the piston accordingly. is there.

The problem to be solved by the present invention is to provide a piston for an internal combustion engine that suppresses entry of cooling oil into a combustion chamber while reducing the weight.

The present invention provides a drain hole that communicates the oil ring groove and the inner surface of the piston body at a position that avoids the inlet channel and the outlet channel of the cooling channel formed along the circumferential direction of the piston body. Solve the above problems.

According to the present invention, the drain hole is provided at a position avoiding the inlet and outlet passages of the cooling oil injected from the lower part of the cylinder of the internal combustion engine toward the inner surface of the piston body. It is possible to suppress the reverse flow of the holes. Therefore, it is not necessary to form a flow path such as an oil gallery inside the piston body, and the thickness of the piston can be reduced by that much, so the cooling oil can enter the combustion chamber while reducing the weight of the piston. Can be suppressed.

It is sectional drawing which shows one Embodiment of the internal combustion engine to which the piston which concerns on this invention is applied. It is a perspective view which shows the piston main body which concerns on this invention. It is a longitudinal cross-sectional view of the piston of FIG. It is sectional drawing which follows the IIIB-IIIB line | wire of FIG. 3B. It is sectional drawing which expands and shows the IV section of FIG. 3A. FIG. 5 is a transverse sectional view (cross section taken along line VV in FIG. 4) showing the first embodiment of the piston according to the present invention. FIG. 5 is a transverse sectional view (a section taken along line VV in FIG. 4) showing a second embodiment of the piston according to the present invention. FIG. 5 is a transverse sectional view (a section taken along line VV in FIG. 4) showing a third embodiment of the piston according to the present invention. FIG. 6 is a transverse cross-sectional view (cross section taken along line VV in FIG. 4) showing a fourth embodiment of the piston according to the present invention. FIG. 6 is a transverse sectional view (cross section taken along line VV in FIG. 4) showing a fifth embodiment of the piston according to the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of an internal combustion engine 3 to which a piston 1 according to the present invention is applied. The internal combustion engine exemplified below is a gasoline engine and is of a type in which fuel is injected into an intake port and an air-fuel mixture with intake air is introduced into a combustion chamber. The piston 1 of the present invention burns fuel. Various internal combustion engines, such as so-called direct injection gasoline engines that directly inject into the chamber, compression self-ignition (HCCI) gasoline engines, engines that switch between compression self-ignition combustion and spark ignition combustion (SI), or diesel engines Can be applied to. In short, as will be described later, the piston 1 of the present invention is applicable to any internal combustion engine that injects cooling oil (also engine lubricating oil) upward from the lower portion of the cylinder 31A toward the inner surface (also referred to as the back surface) of the piston body 11. Can be applied.

The internal combustion engine 3 of this example includes a cylinder block 31 and a cylinder head 33 fastened to the upper surface of the cylinder block 10. A cylinder 31A is formed inside the cylinder block 31, and the piston body 11 is fitted into the cylinder 31A so as to be capable of reciprocating. The piston body 11 and the upper end of the connecting rod 12 are connected by a piston pin 13 so as to be swingable, and the lower end of the connecting rod 12 is connected to a crank arm 32A of the crankshaft 32. Thereby, the reciprocating motion of the piston body 11 due to the combustion stroke is converted into the rotational motion of the crankshaft 32, and the output of this rotational motion becomes the travel drive source of the vehicle. 1 shows one cylinder 31A of the internal combustion engine 3. For example, in the case of a four-cylinder in-line engine, the pair of cylinders 31A and the piston 1 (piston main body 11, connecting rod 12, and piston pin 13) shown in FIG. 4 are provided in the direction perpendicular to the paper surface of FIG. 1 (the axial direction of the crankshaft 32).

The cylinder head 33 is formed with a recess 33A that forms a combustion chamber, which ignites an intake valve 34A that opens and closes the intake port 34, an exhaust valve 35A that opens and closes the exhaust port 35, and a mixture of fuel and air. A spark plug 36 is provided. In the case of the direct injection type engine or the type of engine that switches between compression self-ignition combustion (HCCI) and spark ignition combustion (SI) described above, a fuel injection valve is provided in the vicinity of the spark plug 36, and a diesel engine or a compression self-ignition engine is provided. In the case of an ignition type gasoline engine, a fuel injection valve is provided instead of the spark plug 36.

An oil pan 37 is attached to the lower surface of the cylinder block 31 to store lubricating oil for the internal combustion engine. This lubricating oil is guided to an oil supply path 37B formed inside the cylinder block 31 by an oil pump 37A, and from the oil jet nozzle 37C provided one by one in the lower part of each cylinder block 31, Sprayed on the inner surface (back surface). The lubricating oil injected from the oil jet nozzle 37C has a function of ensuring the lubricity between the piston main body 11 and the cylinder 31A, and also has a function of cooling the piston main body 11 that becomes high temperature by combustion. Therefore, in this specification, lubricating oil is also called cooling oil. The cooling oil injected from the oil jet 37C is injected toward an opening at the lower end of an inlet flow path 17A of the cooling channel 17 described later. Is dropped and collected in the oil pan 37.

Next, the structure of the piston body 11 of this example will be described. FIG. 2 shows the appearance of the piston main body 11 of this example, FIG. 3A shows a vertical cross section of the piston main body 11 of this example, and FIG. 3B shows a cross section of the piston main body 11 of this example. In the piston main body 11 of this example, as shown in these drawings, a crown portion 111 having a crown surface 111A constituting the bottom surface of the combustion chamber and a skirt portion 112 that stabilizes the behavior during reciprocating motion are integrated. Structure. Here, as a method of integrating the crown portion 111 and the skirt portion 112, they can be integrally formed at the time of manufacture, or can be formed into a two-part structure coupled to each other by the piston pin 20.

A top ring groove 113, a second ring groove 114, and an oil ring groove 115 are formed on the outer periphery of the crown portion 111 of the piston body 11 in order from the top. As shown in FIGS. 1 and 2, a top ring is attached to the top ring groove 113, a second ring is attached to the second ring groove 114, and an oil ring is attached to the oil ring groove 115.

A pair of piston pin bosses 18 extending in parallel downward is provided on the inner surface of the crown portion 111, and a piston pin hole 18A is formed in each. The piston pin 13 is fitted into the piston pin hole 18A, whereby the piston main body 11 and the connecting rod 12 are coupled so as to be swingable. As will be described in detail later, the pair of

piston pin bosses

18, 18 hangs parallel to the axial direction of the crankshaft 32 with a predetermined interval, and the piston pin 13 is fitted along the axial direction of the crankshaft 32.

The inner surface (back surface) of the crown portion 111 is formed in a concave shape so as to make the thickness as thin as possible from the viewpoint of weight reduction. Between the inner surface of the crown portion 111 and the top ring groove 113, the second ring groove 114, and the oil ring groove 115, the central axis of the piston main body 11 in a plan view as viewed from the position facing the piston crown surface 111A. An annular cooling channel 17 extending around is formed.

The cooling channel 17 takes in and circulates the cooling oil sprayed from the oil jet nozzle 37C to the inner surface of the piston body 11, and forcibly focuses the center portion of the crown surface 111A and the top ring groove 113 in the piston body 11 in particular. Cooling. Therefore, in order to introduce and lead out the main part of the cooling oil injected from the oil jet nozzle 37C to the inner surface of the piston body 11 to the cooling channel 17, the crown part 111 has a cross-sectional view as shown in FIG. An inlet passage 17A and an outlet passage 17B for cooling oil extending along the axial direction of the piston 1 are formed. The lower end of the inlet channel 17 A opens into the cooling oil injection center region R in the inner surface of the piston body 11, and the upper end communicates with the cooling channel 17. The lower end of the outlet channel 17 B opens at a position other than the cooling oil injection center region R on the inner surface of the piston body 11, and the upper end communicates with the cooling channel 17.

A part of the cooling oil injected from the oil jet nozzle 37C toward the inlet channel 17A on the inner surface of the piston main body 11 is taken into the cooling channel 17 from the inlet channel 17A and circulates, and the outlet channel 17B. To the oil pan 37. Then, the cooling oil circulates through the cooling channel 17 so that mainly the central portion of the crown surface 111A of the piston body 11 and the top ring groove 113 are forcibly cooled.

Here, if the cooling oil sprayed from the oil jet nozzle 37C, including the atomized cooling oil, is overviewed, it will be sprayed to the inner surface of the piston body 11 as a whole. However, since the cooling oil injected from the oil jet nozzle 37C is injected with a predetermined injection pattern width defined by the oil jet nozzle 37C, the term “injection center region R” in this specification refers to the oil jet nozzle. It means the area of the inner surface directed by 37C, and the area where the injection amount of the injected cooling oil is most concentrated.

The cooling channel 17 shown in FIGS. 3A and 3B is circular in cross section, but may be oval or rectangular. In addition, if the passage cross-sectional area of the cooling channel 17 is increased, there is a risk that the fuel consumption may be reduced due to an increase in the amount of cooling oil.

Although the details will be described later, the piston 1 according to the present invention is not only applied to the internal combustion engine 3 having the cooling channel 17 but can also be applied to the internal combustion engine 3 without the cooling channel 17. This will be described in detail in the embodiment shown in FIG. Moreover, the cooling channel 17 is not limited to what was formed continuously over the perimeter of the piston main body 11, and you may comprise it by a discontinuous channel | path. This will be described in detail in the embodiment shown in FIG.

Further, the setting positions of the inlet channel 17A and the outlet channel 17B in the cooling channel 17 are such that the inlet channel 17A is the cooling oil injection center region R and the outlet channel 17B is out of the cooling oil injection center region R. If it is a position (particularly a position where a large amount of cooling oil injected from the oil jet nozzle 37C does not enter), the relative position with respect to the piston body 11 and the internal combustion engine 3 is not particularly limited. However, the setting position of the oil jet nozzle 37C is in the vicinity of the connecting rod 12 and the crankshaft 32 below the cylinder 31A as shown in FIG. Therefore, the position where the cooling oil is appropriately injected toward the inner surface of the piston body 11 while avoiding interference with these is selected. In that sense, the inlet flow path 17A and the outlet flow path in the cooling channel 17 are selected. The relative position of the set position of 17B with respect to the piston body 11 and the internal combustion engine 3 may be limited.

Particularly, the piston 1 of this example has a drain hole 2 that linearly connects the concave surface of the oil ring groove 115 and the inner surface of the piston body 11 as shown in the enlarged sectional view of FIG. One end (the right end in FIG. 4) of the drain hole 2 in this example opens in the concave surface of the oil ring groove 115, and the other end (the left end in FIG. 4) opens in the inner surface of the piston body 11. One end of the drain hole 2 may be opened on at least one of the three surfaces constituting the concave surface of the oil ring groove 115. Further, the drain hole 2 shown in FIG. 4 is inclined downward toward the center of the piston body 11 (same in the embodiment of FIGS. 5 to 9), but may be horizontal.

The piston main body 11 of the embodiment shown in FIGS. 5 to 8 is a piston main body 11 provided with a cooling channel 17, an inlet channel 17A and an outlet channel 17B, and the drain hole 2 thereof is shown in FIGS. As shown, the cooling channel 17 is provided at a position avoiding the inlet channel 17A and the outlet channel 17B. Moreover, the piston main body 11 of the embodiment shown in FIG. 9 is the piston main body 11 in which the cooling channel 17 is not provided, and its drain hole 2 is formed from the lower part of the cylinder 31A as shown in FIG. It is provided at a position avoiding the injection center region R of the cooling oil injected toward the inner surface. 3A and 3B, the illustration of the drain hole 2 according to the present invention is omitted. Hereinafter, embodiments of the drain hole 2 according to the present invention will be described.

<< First Embodiment >>
FIG. 5 is a cross-sectional view (cross section taken along the line VV in FIG. 4) showing the first embodiment of the piston 1 according to the present invention. The cooling channel 17 of this example is formed in an annular passage that is continuous over the entire circumference of the crown portion 111, and an inlet channel 17 A and an outlet channel 17 B are provided at point-symmetrical positions with respect to the center of the piston body 11. . In the illustrated example, the inlet channel 17A is provided in the first quadrant of the XY coordinate plane when the axis of the crankshaft 13 is the Y axis and the axis orthogonal thereto is the X axis, and the outlet channel is provided in the third quadrant. 17B is provided. And the injection center area | region R of the cooling oil from the oil jet nozzle 37C is set to the 1st quadrant containing 17 A of inlet flow paths so that it may show in figure.

With respect to the layout of the cooling channel 17, the inlet channel 17A, and the outlet channel 17B, the drain hole 2 in this example is a position that avoids the inlet channel 17A and the outlet channel 17B of the cooling channel 17. , Two in the second quadrant of the same XY coordinate plane and two in the fourth quadrant are provided. The four drain holes 2 in this example are all formed toward the center of the piston main body 11, and two of the four drain holes 2 facing each other are pointed with respect to the center of the piston main body 11. It is provided at a symmetrical position.

<< Second Embodiment >>
FIG. 6 is a cross-sectional view (cross section taken along the line VV in FIG. 4) showing a second embodiment of the piston 1 according to the present invention. The cooling channel 17 of the present example is an example configured similarly to the above-described first embodiment. That is, the cooling channel 17 of this example is formed in an annular passage that is continuous over the entire circumference of the crown portion 111, and the inlet channel 17 A and the outlet channel 17 B are provided at positions that are point-symmetric with respect to the center of the piston body 11. ing. In the illustrated example, the inlet channel 17A is provided in the first quadrant of the XY coordinate plane when the axis of the crankshaft 13 is the Y axis and the axis orthogonal thereto is the X axis, and the outlet channel is provided in the third quadrant. 17B is provided. And the injection center area | region R of the cooling oil from the oil jet nozzle 37C is set to the 1st quadrant containing 17 A of inlet flow paths so that it may show in figure.

With respect to the layout of the cooling channel 17, the inlet channel 17A, and the outlet channel 17B, the drain hole 2 in this example is a position that avoids the inlet channel 17A and the outlet channel 17B of the cooling channel 17. A total of four are provided in each of the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant of the XY coordinate plane. The four drain holes 2 in this example are all formed toward the center of the piston main body 11, and two of the four drain holes 2 facing each other are pointed with respect to the center of the piston main body 11. It is provided at a symmetrical position.

<< Third Embodiment >>
FIG. 7 is a cross-sectional view (cross section taken along the line VV in FIG. 4) showing a third embodiment of the piston 1 according to the present invention. The cooling channel 17 of this example is an example configured differently from the first embodiment and the second example described above. That is, the cooling channel 17 of the present example is formed in an annular shape along the entire circumference of the crown portion 111, but is a non-communication passage where both ends are not in communication. An inlet channel 17A and an outlet channel 17B are provided at both ends of the cooling channel 17, respectively. In the illustrated example, the inlet channel 17A is provided in the first quadrant of the XY coordinate plane when the axis of the crankshaft 13 is the Y axis and the axis orthogonal thereto is the X axis, and the outlet channel is provided in the fourth quadrant. 17B is provided. And the injection center area | region R of the cooling oil from the oil jet nozzle 37C is set to the 1st quadrant containing 17 A of inlet flow paths so that it may show in figure. When the cooling channel 17 is a discontinuous passage, it is preferable that the positions of both ends be as close as possible from the viewpoint of cooling performance, but the piston 1 of the present invention is particularly limited to the shape of the cooling channel 17. Not. Therefore, the non-communication cooling channel 17 which has the inlet flow path 17A and the outlet flow path 17B in the position which faces like 1st Embodiment and 2nd Embodiment mentioned above may be sufficient.

With respect to the layout of the cooling channel 17, the inlet channel 17A, and the outlet channel 17B, the drain hole 2 in this example is a position that avoids the inlet channel 17A and the outlet channel 17B of the cooling channel 17. A total of four are provided in each of the second quadrant and the third quadrant of the XY coordinate plane. That is, when the inlet channel 17A and the outlet channel 17B of the cooling channel 17 are provided on the right side surface in the axial direction of the crankshaft 32 passing through the center of the piston body 11, all the drain holes 2 in this example are formed. It is provided on the left side. Note that the four drain holes 2 of this example are all formed toward the center of the piston body 11.

<< 4th Embodiment >>
FIG. 8 is a transverse sectional view (cross section taken along line VV in FIG. 4) showing a fourth embodiment of the piston 1 according to the present invention. The cooling channel 17 of the present example is an example configured similarly to the above-described first embodiment. That is, the cooling channel 17 of this example is formed in an annular passage that is continuous over the entire circumference of the crown portion 111, and the inlet channel 17 A and the outlet channel 17 B are provided at positions that are point-symmetric with respect to the center of the piston body 11. ing. In the illustrated example, the inlet channel 17A is provided in the first quadrant of the XY coordinate plane when the axis of the crankshaft 13 is the Y axis and the axis orthogonal thereto is the X axis, and the outlet channel is provided in the third quadrant. 17B is provided. And the injection center area | region R of the cooling oil from the oil jet nozzle 37C is set to the 1st quadrant containing 17 A of inlet flow paths so that it may show in figure.

With respect to the layout of the cooling channel 17, the inlet channel 17A, and the outlet channel 17B, the drain hole 2 in this example is a position that avoids the inlet channel 17A and the outlet channel 17B of the cooling channel 17. A total of four are provided in each of the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant of the XY coordinate plane. In addition, the drain hole 2 of this example is provided in the point-symmetrical position with respect to the center of the piston main body 11 in the two drain holes 2 which face each other out of these four. However, the four drain holes 2 of this example are different from the first to third embodiments described above and the fifth embodiment to be described later, and are all formed with an inclination of an angle θ with respect to the center of the piston body 11, and these The four inclined directions are such that the lower end opening of the drain hole 2 is away from the inlet channel 17A and the outlet channel 17B.

<< 5th Embodiment >>
FIG. 9 is a cross-sectional view (cross section taken along line VV in FIG. 4) showing a fifth embodiment of the piston 1 according to the present invention. The piston body 11 of this example is not provided with the cooling channel 17 shown in the first to fourth embodiments. That is, the crown portion 111 is surrounded by a crown surface 111A that forms a combustion chamber of the internal combustion engine, a cylindrical side surface in which piston ring grooves 113 to 115 including oil ring grooves are formed, and an inner surface of the piston body 11. The portions other than the drain hole 2 are solid. The reason why the crown portion 111 is configured in a solid state is to reduce the weight of the piston 1, and the effect is increased when the thickness of the crown portion 111 is made extremely thin. However, if the thickness of the crown portion 111 is made extremely thin, the space for forming the cooling channel 17 as described above cannot be secured, but if the thickness of the crown portion 111 of the piston main body 11 is made thin, the heat capacity is reduced accordingly. As compared with the piston main body 11 having a larger wall thickness, a relatively small cooling amount is sufficient. Therefore, as shown in the figure, the injection center region R (mainly included in the first quadrant) of the cooling oil injected from the oil jet nozzle 37C is larger than the injection center region R of the first to fourth embodiments described above. It is set.

With respect to the piston body 11 having such a structure without the cooling channel 17, the drain hole 2 of this example is a position avoiding the injection center region R of the cooling oil and is 1 in the second quadrant of the XY coordinate plane. There are four in total, one on the X axis at the boundary between the second quadrant and the third quadrant, and one each in the third quadrant and the fourth quadrant. Note that the four drain holes 2 of this example are all formed toward the center of the piston body 11. Further, one of the four drain holes 2 facing each other is provided at a point-symmetrical position with respect to the center of the piston body 11.

Although the four drain holes 2 are provided in the first to fifth embodiments described above, the number of the drain holes 2 is not limited to four, and may be less than or more than this. Further, when the drain holes 2 are provided to be inclined with respect to the center of the piston body 11 as in the fourth embodiment, it is not necessary to incline all the drain holes 2, and some of the drain holes 2 are inclined. The other drain holes 2 may be formed toward the center of the piston body 11.

<< Operation and Effect of Embodiment >>
Returning to FIG. 4, when the above-described drain hole 2 is provided in the crown portion 111 of the piston body 11, a part of the lubricating oil (that is, cooling oil) adhering to the side surface of the cylinder 31 A due to the vertical movement of the piston body 11 is The oil is scraped off by the ring 16, passes through the oil ring 16, passes through the drain hole 2 from the opening of the oil ring groove 115 of the drain hole 2, and then drops into the cylinder 31 A from the opening on the inner surface of the piston body 11. Collected in bread 37. At this time, as shown in FIG. 4, the drain hole of this example is inclined downward toward the center of the piston main body 11, so that the fall due to its own weight is further promoted.

Further, the drain hole 2 of this example is provided at a position avoiding the inlet channel 17A and the outlet channel 17B of the cooling channel 17 in the first to fourth embodiments. Since it is provided at a position that avoids the injection center region R, it is possible to prevent the cooling oil injected from the lower part of the cylinder 31 A toward the inner surface of the piston body 11 from flowing back through the drain hole 2. Further, by suppressing the backflow, it is advantageous because the lubricating oil passes through the drain hole 2 and further smoothly circulates the lubricating oil (cooling oil).

That is, the inlet channel 17A of the cooling channel 17 is the injection center region R where the cooling oil injected from the oil jet nozzle 37C is most concentrated. Therefore, if the drain hole 2 is provided here, the injected cooling oil directly flows. In addition to flowing into the drain hole 2, a large amount of cooling oil adhering to the inner surface around the inlet channel 17 A flows into the drain hole 2 as the piston body 11 moves up and down at high speed. It becomes.

On the other hand, the cooling fluid that has flowed through the cooling channel 17 is discharged from the outlet channel 17B even at a position that avoids the injection center region R where the cooling oil injected from the oil jet nozzle 37C is most concentrated. Therefore, a large amount of cooling oil also adheres to the inner surface around the outlet channel 17B. Therefore, this large amount of cooling oil flows into the drain hole 2 as the piston body 11 moves up and down at a high speed, which also causes backflow.

However, in the piston 1 of this example, since the drain hole 2 is provided at a position avoiding the injection center region R or the inlet flow path 17A and the outlet flow path 17B that cause the reverse flow, the X shown by the one-dot chain line in FIG. It is possible to suppress the cooling oil from reaching the combustion chamber by following the path of the line. As a result, abnormal combustion due to mixing of the cooling oil with the combustion air-fuel mixture can be suppressed. Further, since the backflow of the cooling oil can be suppressed in this way, it is not necessary to form a flow path such as an oil gallery inside the piston main body 11 as in the conventional technique described above. Therefore, since the thickness of the piston can be reduced by that much, the intrusion of the cooling oil into the combustion chamber can be suppressed while reducing the weight of the piston.

On the other hand, since the drain hole 2 of this example extends linearly between the concave surface of the oil ring groove 115 and the inner surface of the piston body 11, a part of the cooling oil adhering to the side surface of the cylinder 31A is The oil can be smoothly dropped from the opening on the inner surface of the piston main body 11 without being retained in the drain hole 2.

Further, as in the first embodiment, four drain holes 2 are defined as the second quadrant with respect to the cooling channel 17 in which the inlet channel 17A is provided in the first quadrant and the outlet channel 17B is provided in the third quadrant. By providing it in the fourth quadrant, it is possible to better away from both the inlet channel 17A through which the cooling oil is injected and the outlet channel 17B through which the cooling oil is dropped. Moreover, since the four drain holes 2 are not biased with respect to the entire circumference of the cylinder 31A, the cooling oil can be discharged uniformly.

Further, as in the second embodiment, four drain holes 2 are formed in the first quadrant with respect to the cooling channel 17 in which the inlet channel 17A is provided in the first quadrant and the outlet channel 17B is provided in the third quadrant. By providing each in the second quadrant, the third quadrant, and the fourth quadrant, while keeping away from both the inlet flow path 17A where the cooling oil is injected and the outlet flow path 17B where the cooling oil drops, the cylinder 31A Since the four drain holes 2 are not biased with respect to the entire circumference than the drain holes 2 of the first embodiment, the cooling oil can be discharged more uniformly.

Further, as in the third embodiment, four drain holes 2 are defined as the second quadrant with respect to the cooling channel 17 in which the inlet channel 17A is provided in the first quadrant and the outlet channel 17B is provided in the fourth quadrant. By concentrating in the fourth quadrant, it is possible to be farthest from both the inlet flow path 17A where the cooling oil is injected and the outlet flow path 17B where the cooling oil drops.

Further, as in the fourth embodiment, four drain holes 2 are formed in the first quadrant with respect to the cooling channel 17 in which the inlet channel 17A is provided in the first quadrant and the outlet channel 17B is provided in the third quadrant. It is provided in each of the second quadrant, the third quadrant, and the fourth quadrant, and is inclined with respect to the center so that both the inlet flow path 17A from which the cooling oil is injected and the outlet flow path 17B from which the cooling oil is dropped. Further, the four drain holes 2 are not biased with respect to the entire circumference of the cylinder 31A while being away from each other, so that the cooling oil can be discharged more uniformly. In addition, since the drain hole 2 of 4th Embodiment inclines only angle (theta), the opening position of the lower end of the drain hole 2 is compared with the opening position of the lower end of the drain hole 2 of 2nd Embodiment. 17A and the outlet channel 17B are further away from each other.

Further, as in the fifth embodiment, when the cooling channel 17 is not provided and the cooling oil injection center region R is relatively large, four drain holes 2 are provided between the second quadrant and the fourth quadrant. , It can be better away from the main area where the cooling oil is injected. Moreover, since the thickness of the piston body 11 can be made thinner if the cooling channel 17 is not provided, the backflow of the cooling oil can be suppressed, and the weight can be better reduced. Further, since the four drain holes 2 are not so biased with respect to the entire circumference of the cylinder 31A, the cooling oil can be discharged uniformly.

DESCRIPTION OF SYMBOLS 1 ... Piston 11 ... Piston main body 111 ... Crown part 111A ... Crown surface 112 ... Skirt part 113 ... Top ring groove 114 ... Second ring groove 115 ... Oil ring groove 12 ... Connecting rod 13 ... Piston pin 14 ... Top ring 15 ... Second ring DESCRIPTION OF SYMBOLS 16 ... Oil ring 17 ... Cooling channel 17A ... Inlet flow path 17B ... Outlet flow path 18 ... Piston pin boss 18A ... Piston pin hole 2 ... Drain hole R ... Cooling oil injection center area 3 ... Internal combustion engine 31 ... Cylinder block 31A ... Cylinder 32 ... Crankshaft 32A ... Crank arm 33 ... Cylinder head 33A ... Recess 34 ... Intake port 34A ... Intake valve 35 ... Exhaust port 35A ... Exhaust valve 36 ... Spark plug 37 ... Oil pan 37A ... Oil pump 37B ... Oil supply Road 37C ... Oil jet nozzle

Claims

A piston body;
An oil ring groove formed on the outer peripheral surface of the crown portion of the piston body;
Inside the piston body, a cooling channel formed along the circumferential direction of the piston body,
A drain hole communicating the concave surface of the oil ring groove and the inner surface of the piston body,
In the piston for an internal combustion engine that introduces the cooling oil injected from the lower part of the cylinder of the internal combustion engine toward the inner surface of the piston body from the inlet channel of the cooling channel and discharges it from the outlet channel,
The piston for an internal combustion engine, wherein the drain hole is provided at a position avoiding the inlet channel and the outlet channel.
The piston for an internal combustion engine according to claim 1,
One end of the inlet channel opens into the cooling oil injection center region on the inner surface of the piston body, and the other end communicates with the cooling channel.
The outlet channel is a piston for an internal combustion engine having one end opened to a position other than the injection center region on the inner surface of the piston body, and the other end communicating with the cooling channel.
The piston for an internal combustion engine according to claim 1 or 2,
The piston for an internal combustion engine, wherein the inlet channel and the outlet channel are provided on one side from a center line in a plan view of the piston body, and the drain hole is provided on the other side from the center line.
A piston body;
An oil ring groove formed on the outer peripheral surface of the crown portion of the piston body;
A drain hole communicating the concave surface of the oil ring groove and the inner surface of the piston body,
In the piston for an internal combustion engine in which cooling oil is injected from the lower part of the cylinder of the internal combustion engine to the inner surface of the piston body,
The crown portion is surrounded by a crown surface forming a combustion chamber of an internal combustion engine, a side surface on which a piston ring groove including the oil ring groove is formed, and an inner surface of the piston body, and a portion other than the drain hole Is considered solid,
The drain hole is a piston for an internal combustion engine provided at a position avoiding an injection center region where the cooling oil is injected.
The internal combustion engine piston according to any one of claims 1 to 4,
The drain hole is a piston for an internal combustion engine that extends linearly between a concave surface of the oil ring groove and an inner surface of the piston body.
The internal combustion engine piston according to any one of claims 1 to 5,
The said drain hole is a piston for internal combustion engines containing at least a pair of drain hole which opposes along the radial direction of the said piston main body.
The internal combustion engine piston according to any one of claims 1 to 6,
The internal combustion engine piston, wherein the drain hole includes at least a pair of drain holes provided point-symmetrically with respect to the center of the piston body.
The internal combustion engine piston according to any one of claims 1 to 7,
The drain hole is an internal combustion engine piston formed along a radial direction of the piston body.
The internal combustion engine piston according to any one of claims 1 to 7,
The drain hole is a piston for an internal combustion engine formed to be inclined with respect to the radial direction of the piston body.
The internal combustion engine piston according to any one of claims 1 to 9,
The piston for an internal combustion engine, wherein the drain hole is formed to be inclined downward from the oil ring groove toward the inner surface of the piston body.