JP3890857B2 - Piston lubrication structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lubricating structure for a piston of an internal combustion engine.
[0002]
[Prior art]
FIG. 5 to FIG. 6 show piston lubrication structures conventionally used in internal combustion engines. Conventionally, an internal combustion engine converts a reciprocating motion in the direction of the piston central axis X into a rotational motion around the crankshaft by connecting a piston pin 3 supported by the piston 1 and a crankpin of a crankshaft (not shown) with a connecting rod 5. Power transmission.
[0003]
The piston side surface 7 has a piston ring groove 11 in which a piston ring 9 that loosely fits a piston ring 9 that maintains the compression pressure of the combustion chamber 10 and prevents the lubricating oil from flowing into the combustion chamber 10, and the piston 1 has a top dead center. An oil ring groove 19 into which an oil ring 17 for scraping off the lubricating oil adhering to the inner surface 15 of the cylinder liner when it descends is formed.
[0004]
The piston 1 has a lubricating hole 26 that extends from the side surface Y of the oil ring groove 19 to the sliding portion 23 between the piston pin 3 and the pin boss portion 21 of the piston 1, and flows into the oil ring groove 19. Lubricating oil is guided to the sliding portion 23 to lubricate and cool the sliding portion 23.
[0005]
However, in the lubricating structure of the piston 1 configured as described above, as shown in FIG. 6, the lubricating hole 26 that guides the lubricating oil to the sliding portion 23 between the pin boss portion 21 and the piston pin 3 has the oil ring groove 19. Since it can be formed only in the vicinity of the inner pin boss end 22, the amount of lubricating oil flowing in is small, and there is a possibility that the sliding portion 23 is not sufficiently lubricated. As a result, there is a problem that the friction of the sliding portion 23 increases and fuel consumption is deteriorated, or wear is increased and the component life is shortened.
[0006]
Therefore, Japanese Patent Laid-Open No. 9-72215 has a nozzle that injects oil toward the back of the piston, a cooling cavity that circulates oil injected from the nozzle at the top of the piston, and an oil that flows through the cooling cavity. There is disclosed a technique that includes an oil supply hole that partially guides a pin boss portion and ensures lubricity of a sliding portion between the pin boss portion and a piston pin.
[0007]
[Problems to be solved by the invention]
However, the technique described in the above publication has a problem that it is necessary to perform complicated processing on the top of the piston, which complicates the manufacturing process.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide appropriate lubrication to a sliding portion between a pin boss portion of a piston and a piston pin with a relatively simple configuration.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, a first lubricating hole that guides lubricating oil from an oil ring groove that is provided on the side surface of the piston and in which an oil ring is loosely fitted to a sliding portion between the piston pin and the pin boss portion. A pair of skirt portions extending on the thrust side and the anti-thrust side below the piston side surface, a pin boss end surface notched between the pair of skirt portions, and between the pin boss end surface and the piston side surface The first lubricating hole is formed from the flange to supply the excess lubricating oil retained in the flange to the sliding portion when the piston is lowered. Therefore, the excess lubricating oil that remains in the flange portion is guided to the sliding portion between the piston pin and the pin boss portion, and the sliding portion is appropriately lubricated.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. As shown in FIG. 1, an intake port 53 and an exhaust port 55 are formed in the cylinder head 51, and a combustion chamber 57 formed below the cylinder head 51 and an intake valve that opens and closes the intake and exhaust ports. 59 and an exhaust valve 61 are provided, and the intake valve 59 and the exhaust valve 61 are driven in conjunction with the intake, compression, explosion, and exhaust strokes of the engine 50. A cylindrical cylinder liner 65 is press-fitted into the cylinder block 63 below the cylinder head 51, and the piston 70 slides on the inner peripheral surface of the cylinder liner 65 substantially parallel to the piston center axis X by each stroke of the engine 50 described above. Move. The pin boss portion 77 of the piston 70 is pivotally supported by a small end portion 71a of a connecting rod 71 via a piston pin 73, and the large end portion 71b of the connecting rod 71 is pivotally supported by a crankpin 75 of a crankshaft. Thus, the reciprocating motion of the piston 70 is converted into the rotational motion around the crankshaft to transmit power.
[0011]
In this embodiment, the sliding portion 82 between the connecting rod small end portion 71a and the piston pin 73 is an interference fit, and the sliding portion 78 between the piston pin 73 and the pin boss portion 77 is an intermediate fit. Since the fitting structure is adopted, when the piston 70 reciprocates, the connecting rod small end portion 71a and the piston pin 73 are fixed and hardly slide, while the piston pin 73 and the pin boss portion 77 slide in the rotation direction. It is configured to move.
[0012]
As shown in FIG. 2, a piston ring groove 80 is provided above the piston side surface 79, and a piston ring 81 having a role of maintaining the compression pressure of the combustion chamber 57 is loosely fitted.
[0013]
An oil ring groove 83 is formed below the piston ring groove 80 on the piston side surface 79, and an oil ring 84 having a role of scraping off the lubricant adhering to the inner peripheral surface of the cylinder liner 65 when the piston 70 is lowered is loosely fitted. ing. In addition, the introduction hole 87 is formed in the side surface portion P of the oil ring groove 83 at a constant interval so as to introduce excess lubricating oil scraped off by the oil ring 84 and flowing into the oil ring groove 83 into the piston 70. The oil ring groove 83 is formed on the entire circumference and in the vicinity of the pin boss end 74 of the oil ring groove 83 side surface P, the oil ring groove 83 side surface portion P reaches the sliding portion 78 between the piston pin 73 and the pin boss portion 77. One lubricating hole 90 is formed. Accordingly, in the vicinity of the pin boss end 74 of the side surface portion P of the oil ring groove 83, the lubricating oil scraped off by the oil ring 84 and flowing into the oil ring groove 83 passes through the first lubricating hole 90 and the piston pin 73 and the pin boss. Guided to the sliding part 78 with the part 77, the part is lubricated and cooled.
[0014]
Further, a pin boss end surface 96 formed by notching between a pair of skirt portions 110 extending on the thrust side 92 and the anti-thrust side 94 is provided on the pin boss end portion 74 below the piston side surface 79. Between the pin boss end surface 96 and the piston side surface 79, a flange portion 95 that is substantially perpendicular to the pin boss end surface 96 is continuously formed. As a result, the piston side surface 79 is formed with a recessed portion that extends radially inward from the piston side surface 79 side, so that the contact area between the inner peripheral surface of the cylinder liner 65 and the piston side surface 79 is reduced, reducing friction. ing.
[0015]
The flange portion 95 is formed with a second lubrication hole 93 reaching the first lubrication hole 90 described above. That is, as shown in FIGS. 3 and 4, a second lubricating hole 93 having a substantially elliptical cross section is formed upward from the flange portion 95, and the tip of the second lubricating hole 93 extends to the first lubricating hole 90. Has reached.
[0016]
According to the embodiment of the present invention configured as described above, the sliding portion 78 between the pin boss portion 77 and the piston pin 73 can be appropriately lubricated. That is, when the piston 70 descends from the top dead center, the oil ring 84 loosely fitted in the oil ring groove 83 of the piston side surface 79 scrapes off the lubricating oil adhering to the inner peripheral surface of the cylinder liner 65 as described above. The lubricating oil taken into the ring groove 83 is introduced into the piston through the introduction hole 87, and cools the piston. In the vicinity of the pin boss end portion 74, the lubricating oil taken into the oil ring groove 83 is guided to the sliding portion 78 between the piston pin 73 and the pin boss portion 77 through the first lubricating hole 90.
[0017]
On the other hand, without flowing into the oil ring groove 83, the lubricating oil interposed between the inner peripheral surface of the cylinder liner 65 and the piston side surface 79 flows toward the pin boss end surface 96 without the piston skirt portion. At this time, as described above, the flange portion 95 formed between the pin boss end surface 96 and the piston side surface 79 flows because the second lubricating hole 93 reaching the first lubricating hole 90 is opened. The lubricating oil passes through the second lubricating hole 93 and the first lubricating hole 90 from the opening of the flange portion 95 due to inertia, and is guided to the sliding portion 78 between the pin boss portion 77 and the piston pin 73. As a result, surplus lubricating oil retained in the flange portion 95 is used for lubrication of the sliding portion 78 between the pin boss portion 77 and the piston pin 73. As a result, since the sliding portion 78 is sufficiently lubricated with a simple configuration, the friction at the same portion is reduced, fuel efficiency is improved, wear is suppressed, and the component life is improved.
[0018]
In this embodiment, the connecting structure between the connecting rod small end portion 71a and the piston 70 is a press-fit structure, but is not limited to this, and the sliding portion between the connecting rod small end portion 71a and the piston pin 73 is not limited thereto. Since the piston pin 73 and the pin boss part 77 need to be lubricated even in the full float structure in which the sliding part 78 between the piston pin 73 and the pin boss part 77 is set to an intermediate fit with the gap 82 being the clearance fit, It has the same effect.
[0019]
In the present embodiment, the opening end 102 of the first lubrication hole 90 is configured to face the sliding portion 78 of the piston pin 73 and the pin boss portion 77. However, the present invention is not limited to this. The piston pin 73 and the pin boss part 77 may be lubricated as a configuration in which the oil ring groove 83 extends linearly from the side surface part P of the oil ring groove 83 and the opening end faces the piston internal space 100.
[0020]
【The invention's effect】
As described above in detail with the embodiment, according to the piston lubricating structure of the present invention, the first lubricating hole for guiding lubricating oil from the oil ring groove to the sliding portion between the piston pin and the pin boss portion, and the piston A pin boss end surface formed by cutting out a pair of skirt portions extending on the thrust side and the anti-thrust side below the side surface, and formed between the pin boss end surface and the piston side surface, and substantially the same as the pin boss end surface And a second lubrication hole that reaches the first lubrication hole from the collar to supply the surplus lubricating oil retained in the collar to the sliding portion when the piston descends. Excess lubricating oil remaining in the flange is guided to the sliding portion between the piston pin and the pin boss portion, and the sliding portion is appropriately lubricated. As a result, the friction of the sliding portion between the piston pin and the pin boss portion is reduced, the fuel consumption is improved, the wear is suppressed, and the component life is also improved.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a piston lubrication structure according to an embodiment of the present invention.
2 is a piston lubrication structure according to an embodiment of the present invention, and is a cross-sectional view taken along the line II in FIG.
FIG. 3 is an enlarged view of a Q portion in FIG. 2;
4 is a piston lubrication structure according to an embodiment of the present invention, and is a view as viewed from A in FIG.
FIG. 5 is a cross-sectional view of an essential part showing a conventional lubricating structure of a piston.
6 is a piston lubrication structure of the prior art, and is a Z view of FIG.
[Explanation of symbols]
70 piston 73 piston pin 77 pin boss part 78 sliding part 83 oil ring groove 84 oil ring 90 first lubricating hole 93 second lubricating hole 95 flange 96 pin boss end face

Claims (1)

A piston, a connecting rod pivotally supported on a pin boss portion of the piston via a piston pin, an oil ring groove provided on a side surface of the piston and having an oil ring loosely fitted thereto, and the piston ring from the oil ring groove A first lubricating hole for guiding lubricating oil to a sliding portion with the pin boss portion, a pair of skirt portions extending on the thrust side and the anti-thrust side below the side surface of the piston, and a gap between the pair of skirt portions. a pin boss end surface which is away form, is formed between the piston side surface and the pin boss end surface, and a substantially vertical eaves part against the pin boss end surface, the piston lowers the surplus lubricating oil staying in the eaves section A piston lubrication structure comprising a second lubrication hole extending from the flange to the first lubrication hole to be supplied to the sliding part .

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