JPH0979376A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston for an internal combustion engine to simply settle scuffing by improving lubricity of a piston, to which scuffing occurs, through simple constitution. SOLUTION: In a piston for an internal combustion engine wherein, in an internal combustion engine having a piston being reciprocated, oil drain holes 58 and 60 are formed in the oil ring mounting place (an oil ring groove part 54) of the piston or the periphery thereof, the oil drain holes 58 and 60 of the piston in the same position in the axial direction of the piston are formed in the same bore. In the number of the oil drain holes 58 and 60 on the respective sides with a piston pin nipped therebetween, the number of the oil drain holes on the side 50SA wherein a scuffing countermeasure is taken is decreased to a value lower than that on the side 50SB wherein no scuffing countermeasure is taken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine, which is applied to a piston of an internal combustion engine and improves scuff resistance of a piston skirt portion.

[0002]

2. Description of the Related Art FIG. 3 shows a cross section of a cylinder portion of a conventional four-cycle engine 10. In the case of FIG. 3, the oil pan and the cylinder head are omitted. 4 is a detailed sectional view of the piston 22, FIG. 5 is a sectional view taken along the line AA of FIG. 4, and FIG. 6 is a side view of the piston 22.

In the engine 10 shown in FIG. 3, the crankshaft 14 rotates in the crank chamber 12, and the large end 18a of the connecting rod 18 is rotatably connected to the crankpin 16 of the crankshaft 14. To be done.
A piston 22 is rotatably connected to the small end 18b of the connecting rod 18 by a piston pin 20. The piston 22 is inserted in a cylinder (for example, a cylinder liner) 24, and the piston 22 moves up and down while sliding on the inner wall 24a of the cylinder 24 due to combustion of fuel.
The outer circumference of the cylinder 24 is surrounded by a cylinder block 26, and the lower portion of the cylinder block 26 is a crankcase 28 that surrounds the crank chamber 12. In FIG. 3, reference numeral 30 is a water jacket space portion on the outer peripheral portion of the cylinder 24.

In the above engine 10, the vertical movement of the piston 22 due to combustion of fuel is transmitted from the piston pin 20 to the crank pin 16 via the connecting rod 18. In this case, the large end portion 18a of the connecting rod 18 in the crank chamber 12 is rotated by the crank pin 16 around the central axis 14a of the crankshaft 14, and the piston 22
The up-and-down movement of the crankshaft is converted into the rotational movement of the crankshaft 14.

As shown in FIGS. 3, 4 and 6, two compression rings (1st (first) compression ring, 2nd (second) compression ring) are provided on the upper outer peripheral surface of the piston 22.
Compression ring groove portions 36a and 36b for mounting the oil rings 32a and 32b and the oil ring 34 and an oil ring groove portion 38 are formed, respectively. The compression ring 32 includes a piston 22 and a cylinder 24 inner wall 24.
It is also referred to as a pressure ring that maintains airtightness between a and transfers heat to the cylinder 24. The oil ring 34 is
The oil on the inner wall 24a of the cylinder 24 is scraped off to form a uniform oil film.

Here, as shown in FIGS. 3 to 6, oil drain holes 40 and 4 penetrating the piston inner peripheral portion 22a are provided in the oil ring groove portion 38 and below the oil ring groove portion 38.
A plurality of 2 are drilled. The inner diameters φA of the plurality of oil drain holes 40 are formed to have the same diameter, and the inner diameters φB of the plurality of oil drain holes 42 are also formed to have the same diameter. However, each hole 40
The inner diameters of 42 and 42 are different (φA ≠ φB).

The oil drain holes 40 and 42 are provided for returning the oil scraped off by the oil ring 34 from the oil on the wall surface of the cylinder 24 into the crank chamber 28 from the piston inner peripheral portion 22a. This is primarily aimed at reducing oil ingress into the combustion chamber and reducing oil consumption. Regarding the oil hole
No. and Jitsukaihei 3-61142 are proposed.

A skirt portion 22b is formed from the central portion to the lower portion of the piston 22, and as shown in FIG.
The length is short below the pin boss 44 into which the piston pin 20 is fitted, and is long at the side surface of the piston pin 20 in the vertical direction. A rib 22 for guiding the oil, which has entered from the oil drain holes 40 and 42, toward the center of the cylinder 24 and dropping it into the crank chamber 12 is provided on the piston inner peripheral portion 22a so as not to adhere to the cylinder inner wall 24a.
c is formed.

[0009]

By the way, the piston 2
Scuffing may occur between the second skirt portion 22b and the inner wall of the cylinder 24a. The causes of this scuffing are considered to be the bore deformation of the cylinder 24 due to heat load, the thermal deformation of the piston 22, the improper piston profile (skirt shape), the swinging behavior of the piston 22, and the cylinder 24.
Due to excessive lateral pressure between the piston and piston 22, insufficient lubrication, etc.
The skirt portion 22b locally exhibits metal contact, leading to scuffing. Further, the location where scuffing occurs generally occurs on either one of both side surfaces of the skirt portion 22b of the piston.

On the other hand, the diameter of the oil drain hole is changed or the shape of the oil drain hole is changed in order to improve the lubricity by reducing the amount of oil returned in the portion where the scuffing is likely to occur (see the above-mentioned actual opening 64). -44347, technology such as Sankaihei 3-61142).

However, in order to change the hole diameter and shape of the oil drain hole, it is necessary to change tools such as a drill and a milling cutter, and even if an NC (numerical control) machine tool is used, it is necessary to manage the tools. Therefore, in any case, the processing takes time and the cost increases. Furthermore, even if it is attempted to form the oil drain hole by casting at the time of casting, it is unlikely that it is difficult to form a mold for the oil drain hole, and even if it is possible, the cost increase must be extremely large. .

The present invention has been made in view of the above-mentioned conventional problems, and provides a piston for an internal combustion engine capable of easily solving scuffing by improving the lubricity of a site where scuffing occurs. Is an issue.

[0013]

The present invention has the following constitution in order to solve the above problems. The invention of claim 1 is an internal combustion engine in which a piston reciprocates, and in an internal combustion engine piston in which an oil drain hole is provided at or around an oil ring mounting location of the piston, the oil drain hole of the piston is provided in the piston axial direction. It is characterized in that the same position is formed with the same inner diameter, and the number of oil drain holes on each side sandwiching the piston pin is smaller on the side that takes scuffing measures than on the side that does not take scuffing measures. And a piston structure for an internal combustion engine.

According to the first aspect of the invention, since the oil drain holes of the piston are formed at the same position in the axial direction of the piston and have the same inner diameter, at least the oil drain holes at the same position are formed by a single type drill or the like. It can be done with tools. Therefore, in one piston, it is not necessary to change the tool required when the inner diameter of the oil drain hole is changed or the shape of the oil drain hole is changed, and the tool management is simple. The number of oil drain holes on each side of the piston pin is smaller on the side that does not take scuffing measures than on the side that does not take scuffing measures.Therefore, setting the number of oil drain holes is extremely important. Scuffing measures can be taken easily with a simple method.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 are explanatory views of a piston of an internal combustion engine according to an embodiment of the present invention.
The vertical cross-sectional view of the engine is substantially the same as that shown in FIG. 3, and the vertical cross-sectional view of the piston is substantially the same as that shown in FIG. 1 is a sectional view of the piston 50 taken along the line I-I in FIG. 2, and FIG.
0 side view is shown respectively.

As shown in FIG. 1, the internal combustion engine according to the embodiment is an internal combustion engine in which a piston 50 reciprocates, and the piston 50 has a bottom portion of an oil ring groove portion 54 where an oil ring (not shown) is mounted or. An oil drain hole is provided around it. Specifically, the oil drain hole 58 penetrating from the bottom of the oil ring groove 54 toward the piston inner peripheral portion 50a, and the upper end of the skirt portion 56 of the piston 50 below the groove portion 54 to the piston inner peripheral portion 50a.
A plurality of oil drain holes 60 are formed, each penetrating toward a and obliquely downward. The piston 5
The zero piston pin 52 is offset by a minute distance α to the exhaust side (50SA described later).

The piston 50 has a plurality of oil drain holes 58 and 60, and the diameters φC and φD of the oil drain holes 58 and 60 at the same position in the axial direction of the piston 50 (a plurality of oil drain holes 58 and a plurality of oil drains 60) are set. Each has the same inner diameter. The diameter of the oil drain hole 58 is φ
C and the hole diameter φD of the oil drain hole 60 have the same diameter (φC =
Both φD) and different diameters (φC ≠ φD) can be set according to the conditions. Further, the piston 50 is provided with oil drain holes 58 and 60 on respective sides sandwiching a piston pin (pin axis is indicated by reference numeral PS) 52. The side where scuffing has occurred or is likely to occur in the actual machine is the side 50SA for which scuffing measures are taken, and the opposite side is the side 50SB for which scuffing measures are not taken, and a plurality of oil drain holes 58 and 60 are formed on those sides, respectively. Has been done.

As shown in FIG. 1, on the side where scuffing occurs or the side where scuffing may occur, for example, the exhaust side after combustion, which has a high temperature, is discharged and the oil becomes a high temperature and is easily exhausted. (Ex side), and it is preferable to set this as the side 50SA that takes measures against scuffing. On the other side, intake air of a relatively low temperature is introduced, and the temperature of the oil becomes low and it is hard to be consumed.
There is a side) and there is no scuffing countermeasure here 50
It is preferably SB.

No matter how many holes the oil drain holes 58 and 60 have, the side 5 that does not take measures against scuffing
The number of holes on the side 50SA on which the countermeasure is taken is smaller than that of 0SB. As an example, as shown in FIG. 1, regarding the number of holes on the side 50SA for which the scuffing measures are taken, an oil drain hole 58 in the oil ring groove 54 is provided.
Is four, and the number of oil drain holes 60 at the upper end of the skirt is three. At the same time, regarding the number of holes on the side 50SB where no scuffing is taken, the number of oil drain holes 58 in the oil ring groove portion 54 is 5, and the number of oil drain holes 60 at the upper end of the skirt portion is 4.

As described above, according to this embodiment, since the oil drain holes 58 and 60 of the piston 50 are formed to have the same inner diameter, the oil drain holes 58 and 6 are formed.
The formation of 0 can be performed with a single kind of tool such as a drill. Therefore, in one piston 50, the inner diameters (φC and φD) of the oil drain holes 58 and 60 were changed to the same position in the axial direction of the piston 50, or the shapes of the oil drain holes 58 and 60 were changed. In addition to the need for changing the tool that is necessary in some cases, the tool can be managed easily.

The number of oil drain holes 58 and 60 on the respective sides 50SA and 50SB sandwiching the piston pin 52 is the same as the side 50S on which scuffing measures are not taken.
Since the side 50SA on which the countermeasure is taken is formed to be smaller than that on B, the countermeasure against scuffing can be easily performed by an extremely simple method of setting the number of holes of the oil drain holes 58 and 60. Thus, the lubricity between the piston 50 on the scuffing countermeasure side and the inner wall surface of the cylinder 24 is improved, and a simple scuffing countermeasure is provided.

On the other hand, on the other hand, there is a risk of increasing the oil consumption, so the side 50S that takes scuffing measures.
The oil drain holes 58 and 60 on the opposite side 50SB of A are the same in number and hole diameter as the conventional one (see FIG. 5 for comparison).

In the embodiment described above, as an example, in the engine shown in FIG. 3, the configuration of the oil drain holes shown in FIGS. 1 and 2 is shown, but the inner diameter and the number of the oil drain holes are not limited to this. The number of oil drain holes can be appropriately selected as long as the scuffing countermeasure side is less than the opposite side. Further, the scuffing countermeasure side is not limited to the exhaust side, and can be selected by taking into consideration the state of the actual machine.

[0024]

As described above, according to the present invention, the oil drain hole can be formed by a single type of tool such as a drill. Therefore, in one piston, it is not necessary to change the tool required when the inner diameter of the oil drain hole is changed or the shape of the oil drain hole is changed, and the tool management is simple. Therefore, the work of processing the oil drain hole is simplified, and the work load and the manufacturing cost can be reduced. The number of oil drain holes on each side of the piston pin is smaller on the side that does not take scuffing measures than on the side that does not take scuffing measures.Therefore, setting the number of oil drain holes is extremely important. Scuffing measures can be taken easily with a simple method. In this way, lubricity is improved on the side that has taken scuffing measures.

[Brief description of drawings]

FIG. 1 is an explanatory view of a piston of an internal combustion engine according to an embodiment of the present invention, which is a cross-sectional view taken along the line I-I of FIG.

FIG. 2 is a side view of the piston of FIG.

FIG. 3 is an example of a vertical sectional view of an engine.

FIG. 4 is an example of a vertical sectional view of a piston.

5 is a cross-sectional view taken along the line AA of FIG. 4, showing an example of an oil drain hole of a conventional piston.

FIG. 6 is a side view of a conventional piston.

[Explanation of symbols]

 50 Piston 50a Piston inner circumference 50SA Piston scuffing prevention side 50SB Piston scuffing prevention side 54 Oil ring groove 56 Piston skirt 58 Oil drain hole 60 Oil drain hole

Claims (1)

[Claims] 1. A piston for an internal combustion engine in which a piston reciprocates, and an oil drain hole is provided at or around an oil ring mounting position of the piston, and the oil drain hole of the piston is located at the same position in the axial direction of the piston. Characterized in that the number of oil drain holes on each side sandwiching the piston pin is smaller on the side that does not take scuffing measures than on the side that does not take scuffing measures. Piston for internal combustion engine.