JPH11159397A - Piston of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently carry out a cooling by lubricating oil. SOLUTION: The piston 11 comprises a head part 13 of approximately disk- shaped having ring grooves 16 to which a piston ring is attached, a skirt part 15 provided under the head part 13, and a pair of pin boss parts 14 provided inside the head part 13 and the skirt part 15 and having a piston pin hole 20 to which a piston pin is inserted and pin boss rib part 21. A guide groove 27 for selectively leading lubricating oil J to a pin boss rib corner part 22 at which a back surface of the heat part 13 and the pin boss rib part 21 cross to each other is provided on an inner wall surface of a lower end part of the skirt part 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston which reciprocates in a cylinder bore with the combustion of an internal combustion engine, and more particularly to an improvement in a cooling structure of the piston.

[0002]

2. Description of the Related Art As is well known, the piston of an internal combustion engine is
A substantially disk-shaped head portion having a ring groove for mounting a piston ring, a skirt portion provided below the head portion, and provided inside the head portion and the skirt portion, and a piston pin is provided. A pair of pin bosses having a piston pin hole to be inserted and a pin boss rib are provided. Generally, such a piston is required to have a rigidity basically capable of withstanding high-speed motion and thermal deformation and to be lightweight so as to ensure high-speed motion performance.

In this type of piston, the top surface of the head portion forms a part of a combustion chamber, and the piston becomes high temperature under the influence of heat generated in the combustion chamber. And cannot be cooled directly by the outside air. Therefore, conventionally, in order to reduce the temperature, lubricating oil is sprayed onto the inner surface of the piston by an oil jet nozzle or the like, and heat is taken away by the lubricating oil on the inner surface to cool the piston.

[0004]

As described above, although the lubricating oil can be cooled for a while by spraying the lubricating oil,
With the piston structure described above, the exact cooling effect is not always obtained. That is, in the structure of the piston, there is a bias in a portion where the temperature or the stress becomes high, and in particular, a pin boss rib corner portion where the back surface of the head portion and the pin boss rib portion intersect is exposed to a high temperature. Is a part where heat is difficult to escape and is hard to cool, and is a part where various stresses are concentrated.

However, even if the lubricating oil is sprayed on the inner surface of the piston in the above-described manner, the lubricating oil is not always supplied actively to the pin boss rib corners and the like, in particular, to the parts requiring cooling. As a result, the piston cannot be cooled efficiently, for example, the cooling of the portion having a high temperature or high stress is insufficient, or the cooling of the entire piston is uneven.

The present invention has been made in view of such circumstances, and has as its object to provide a cooling structure for more efficiently cooling with lubricating oil and maintain its stable function for a long period of time. It is an object of the present invention to provide a piston of an internal combustion engine that can perform the above.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a substantially disk-shaped head portion having a ring groove in which a piston ring is mounted, and the head portion thereof And a pair of pin boss portions provided inside the head portion and the skirt portion and having a piston pin hole and a pin boss rib portion through which a piston pin is inserted. A lubricating oil guide means for guiding lubricating oil to a pin boss rib corner portion where the back surface of the head portion intersects with the pin boss rib portion on the inner wall surface of the skirt portion. That is the gist.

According to the first aspect of the present invention, when the piston reciprocating in the cylinder bore descends,
Since the lubricating oil supplied to the skirt is guided to the pin boss rib corner by the lubricating oil guiding means, the lubricating oil surely contacts the pin boss rib corner. Thereafter, the lubricating oil is supplied so as to spread over the entire inner surface of the piston, and at the same time comes into contact with the entire inner surface of the piston. In the part where the lubricating oil is in contact,
The heat is removed by the lubricating oil and thereby cooled.
In this way, the lubricating oil is actively supplied to the corners of the pin boss ribs where the temperature and stress are high, and then supplied entirely to the inner surface. To be increased.

According to a second aspect of the present invention, in the piston for an internal combustion engine according to the first aspect, the lubricating oil guiding means is a guide groove formed in an inner wall surface of a lower end portion of the skirt portion. This is the gist.

According to the second aspect of the invention, the lubricating oil supplied to the skirt portion is reliably guided to the pin boss rib corner portion by the guide groove. For this reason,
The pin boss rib corner can be reliably cooled.

Further, in the invention according to claim 3, in the piston of the internal combustion engine according to claim 1, the lubricating oil guide means is a projection formed on an inner wall surface of the skirt portion. It is a gist.

According to the third aspect of the present invention, the lubricating oil supplied to the skirt is reliably guided to the pin boss rib corner by the projection. For this reason,
The pin boss rib corner can be reliably cooled.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a front view showing a piston 11 according to the first embodiment, and FIG. 1B is a bottom view of the piston 11 schematically showing a flow of a lubricating oil J. . FIG. 2 is an operation view showing a state in which the piston 11 and the like according to the first embodiment are assembled in the cylinder bore 12.

As shown in FIGS. 1 (a), 1 (b) and 2, the piston 11 has a substantially disk-shaped head portion 1.
3, a pair of pin bosses 14 provided on the inner wall surface of the head 13, and a skirt 15 provided below the head 13. This piston 11
For example, it is formed of a lightweight metal material such as an aluminum alloy and excellent in thermal conductivity and the like, and has a predetermined rigidity.

Here, three ring grooves 16 extending in the circumferential direction are formed on the outer periphery of the head portion 13.
Each ring groove 16 is provided with a piston ring 17 (FIG. 2). More specifically, the piston ring 17 includes two compression rings 17a, 1
7b and one oil ring 17c. Compression rings 17a and 17b are mounted on the two ring grooves 16 located at the uppermost and central parts, respectively, and an oil ring 17c is mounted on the ring groove 16 located at the lowermost part. The oil return hole 1 is provided in the ring groove 16 in which the oil ring 17c is mounted.
8 (FIG. 1) are provided. The compression rings 17a and 17b are for preventing gas leakage during the compression stroke and the explosion process, and the oil ring 17c is for scraping off excess lubricating oil J adhering to the inner wall surface of the cylinder bore 12. It is.

The pin boss 14 has a piston pin hole 20 and a pin boss rib 21 through which the piston pin 19 (FIG. 2) is inserted. The piston pin 19 is mounted by being inserted into the piston pin hole 20. The pin boss ribs 21 serve to reinforce the pin bosses 14.
On the other hand, the corner where the back surface of the head portion 13 intersects the pin boss portion 14 is a pin boss rib corner portion 22.
It has become. The pin boss rib corner portion 22 is an area where excessive stress is applied and various loads are exposed to high temperatures. The pin boss rib corner 22
Corresponds to the dotted pattern portion shown in each of FIGS. 1 and 2.

Further, the skirt portion 15 is formed as shown in FIG.
Alternatively, as shown in FIG. 2, it is formed to extend downward below the head portion 13. As shown in FIG. 2, the piston 11 configured as described above is connected to a connecting rod 24 connected to a crankshaft 23 which is an output shaft thereof, for example, in an automobile engine.
It is connected via a piston pin 19. In this connection state, the piston 11 is assembled in a cylinder bore 12 provided in the engine, and reciprocates in the cylinder bore 12 during operation of the engine. The oil jet nozzle 25 provided on the connecting rod 24
Oil passage 2 of crankshaft 23 during engine operation
The lubricating oil J, which is fed to the cylinder 6, is injected toward the inner surface of the piston 11 and the inside of the cylinder bore 12.
In this case, the lubricating oil J injected toward the inner surface of the piston 11 is blown upward from below the skirt portion 15. Therefore, in the present embodiment, the following structure is further employed in order to enhance the cooling effect of the piston 11 by the sprayed lubricating oil J.

That is, as shown in FIGS. 1 (a) and 1 (b), in the piston 11 according to the present embodiment, a guide groove 27 as a lubricating oil guide is provided on the inner wall surface of the lower end of the skirt portion 15. Has formed. More specifically, the guide groove 27 is formed in the skirt portion 15 as shown in FIG.
The lubricating oil J is selectively guided to the pin boss rib corner portion 22 as the piston 11 descends, as shown in FIG.

The operation and effect of this embodiment will be described below. In the present embodiment, the guide groove 27 is formed on the inner wall surface at the lower end of the skirt 15 in order to selectively guide the lubricating oil J to the pin boss rib corner 22. Therefore, as shown in FIGS. 1B and 2, when the piston 11 reciprocating in the cylinder bore 12 descends, the piston 11 is gathered by the skirt portion 15 or
The lubricating oil J sprayed by the oil jet nozzle 25 flows in the direction of the arrow along the guide groove 27 and is intensively guided to the pin boss rib corner 22. The lubricating oil J thus guided comes into reliable contact with the pin boss rib corner 22. afterwards,
The lubricating oil J flows so as to spread entirely on the inner surface of the piston 11 and simultaneously contacts the entire inner surface. Then, at the portion where the lubricating oil J contacts, the lubricating oil J
Heat is taken away, and thereby cooled.
As described above, after the lubricating oil J is actively supplied to the pin boss rib corner portions 22 having high temperature and high stress,
Since the entire surface is supplied to the inner surface, the cooling of the piston 11 by the lubricating oil J can be performed very efficiently. The pin boss rib corner 22
Is an excessive part of the load exposed to high temperature while various stresses are concentrated, and thus the pin boss rib corner 22 is reliably cooled, thereby suppressing the occurrence of cracks and the like due to a decrease in the strength. You can also.

In the present embodiment, since the pin boss rib corner 22 can be efficiently cooled by the lubricating oil J, it is not necessary to increase the thickness of the head 13 and the like of the piston 11. Therefore, the weight of the piston 11 can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. However, in the configuration and the like of the present embodiment, portions that are the same as those in the above-described first embodiment are given the same reference numerals, and descriptions thereof are omitted. The description will focus on the differences from the first embodiment.

FIG. 3A is a front view showing a piston 31 according to the second embodiment, and FIG. 3B is a bottom view of the piston 31 schematically showing a flow of a lubricating oil J. .

As shown in these figures, the piston 31 according to the present embodiment is different from the piston 11 of the first embodiment in the structure of the inner wall surface of the skirt portion 32. . That is, in the present embodiment, instead of the guide groove 27 (see FIG. 1), a projection 33 as a lubricating oil guide is formed on the inner wall surface of the skirt portion 32 so as to protrude. To elaborate,
The projections 33 are arranged on the skirt portion 32 as shown in FIGS.
And the lubricating oil J is selectively guided to the pin boss rib corner portion 22 as the piston 31 descends.

The operation and effect of this embodiment will be described below. In the present embodiment, in order to selectively guide the lubricating oil J to the pin boss rib corner 22, the protrusion 33 is formed to project from the inner wall surface of the skirt 32.
Therefore, when the piston 31 descends, the lubricating oil J collected or sprayed by the skirt portion 32 flows along the protrusion 33 and is guided intensively to the pin boss rib corner portion 22. Then, the lubricating oil J thus guided is applied to the pin boss rib corner 22.
Will surely come into contact with After that, lubricating oil J
Flows in such a manner as to spread entirely over the inner surface of the piston 31 and simultaneously contacts the entire inner surface thereof. In this way, at the portion where the lubricating oil J comes into contact, heat is taken away by the lubricating oil J and thereby cooled. As described above, also in the present embodiment, since the lubricating oil J is positively supplied to the pin boss rib corner portions 22 having high temperature and high stress, and is entirely supplied to the inner surface, the lubricating oil J Cooling of the piston 31 by J can be performed very efficiently.

It should be noted that the present invention is not limited to the above embodiments, but may be implemented as follows, with a part of the configuration being appropriately changed without departing from the spirit of the invention. In the above-described embodiments, four guide grooves 27 and four protrusions 33 are formed on the inner wall surfaces of the skirt portions 15 and 32. However, if the lubricating oil J can be reliably guided to the pin boss rib corner portions 22, The numbers of the guide grooves 27 and the projections 33 are not particularly limited. Further, a configuration may be employed in which five or more guide grooves and protrusions are formed on the inner wall surface of the skirt portion, and guide grooves and protrusions are formed on the inner wall surface of the skirt portion. With this configuration, the cooling effect of the piston by the lubricating oil J can be further enhanced.

In the above embodiments, the guide groove 27 and the projection 33 are used as the lubricating oil guide means. However, if the lubricating oil J can be accurately guided to the pin boss rib corner portion 22, for example, the oil may be used. A jet nozzle, a pipe or the like may be used, and the lubricating oil guiding means is not particularly limited to the guide groove 27 or the projection 33.

In the first embodiment, the lubricating oils J are guided by the guide grooves 27 so as not to intersect. However, the lubricating oils J are guided to intersect on a plane, that is, diagonally. You may. In this case, in order to prevent the lubricating oils J from actually interfering with each other,
It is desirable to adjust the angle at which the guide groove is formed.

In the second embodiment, the protrusion 33 is formed integrally with the skirt portion 32. However, the protrusion and the skirt portion may be formed separately, and they may be joined by, for example, welding. Good.

In each of the above embodiments, the pistons 11 and 31 having three ring grooves 16 have been embodied. However, the pistons may have other ring grooves than three.
In addition, technical ideas that are not described in each claim of the claims and that can be grasped from each of the above embodiments are described below together with their effects.

[0031] In the piston for an internal combustion engine according to claim 1, the lubricating oil guide means includes a guide groove formed on an inner wall surface at a lower end portion of the skirt portion, and a projection formed on an inner wall surface of the skirt portion. And characterized by the following.

In this case, since the two means are used as the lubricating oil guiding means, the cooling effect by the lubricating oil can be further enhanced. -The piston of the internal combustion engine according to any one of claims 1 to 3, wherein the head, the skirt, and the pin boss are formed of an aluminum alloy.

With this configuration, the weight of the piston can be reduced.

[0034]

According to the first aspect of the present invention, the lubricating oil supplied to the skirt can be reliably guided to the pin boss rib corner by the lubricating oil guiding means. Therefore, the pin boss rib corners can be reliably cooled by the lubricating oil, and the cooling effect of the piston can be efficiently increased.

According to the second aspect of the present invention, the lubricating oil supplied to the skirt can be reliably guided to the pin boss rib corner by the guide groove. Therefore, the corner portions of the pin boss ribs can be reliably cooled by the lubricating oil, and the piston can be cooled more efficiently.

According to the third aspect of the present invention, the lubricating oil supplied to the skirt can be reliably guided to the pin boss rib corner by the projection. Therefore, the corner portions of the pin boss ribs can be reliably cooled by the lubricating oil, and the piston can be cooled more efficiently.

[Brief description of the drawings]

FIG. 1 is a front view and a bottom view showing a configuration of a piston according to a first embodiment.

FIG. 2 is an operation view showing a state where the piston and the like according to the embodiment are assembled in a cylinder bore;

FIG. 3 is a front view and a bottom view showing the configuration of a piston according to a second embodiment.

[Explanation of symbols]

11: piston, 12: cylinder bore, 13: head, 14: pin boss, 15: skirt, 16: ring groove, 17: piston ring, 17a, 17b: compression ring, 17c: oil ring, 19: piston pin, 20: Piston pin hole, 21: Pin boss rib, 22: Pin boss rib corner, 27: Guide groove as lubricating oil guide, 31: Piston, 32: Skirt, 33: Projection as lubricating oil guide, J ...
Lubricating oil.

Claims (3)

[Claims] 1. A substantially disk-shaped head having a ring groove in which a piston ring is mounted, a skirt provided below the head, and provided inside the head and the skirt. A piston pin hole into which a piston pin is inserted, and a pair of pin boss portions having pin boss rib portions, the piston of an internal combustion engine reciprocating in a cylinder bore, wherein the inner wall surface of the skirt portion is A piston for an internal combustion engine, comprising lubricating oil guide means for guiding lubricating oil to a pin boss rib corner where a back surface of a head portion and the pin boss rib intersect. 2. The piston of an internal combustion engine according to claim 1, wherein said lubricating oil guide means is a guide groove formed in an inner wall surface of a lower end portion of said skirt portion. 3. The piston of an internal combustion engine according to claim 1, wherein said lubricating oil guide means is a projection formed on an inner wall surface of said skirt portion.