JP2768978B2 - Lubrication structure of piston pin for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating structure for a piston pin for an internal combustion engine, and more particularly, to reliably discharge fine metal powder generated from a friction surface to reduce wear of a piston or a piston pin. The present invention relates to a lubricating structure that can prevent seizure and is advantageous in strength.

[Conventional technology]

The piston of the internal combustion engine is for transmitting the combustion pressure to the crankshaft via the connecting rod, but in connection with the connecting rod, the small end of the connecting rod is located between both bosses of the piston body, The boss,
A structure is employed in which a piston pin is rotatably inserted into a piston pin hole formed through the small end. By the way, since a large load due to combustion and a large inertial force due to reciprocating motion act on the connecting portion between the piston and the piston pin, lubricating oil is provided between the outer peripheral surface of the piston pin and the inner peripheral surface of the piston pin hole. To prevent wear and seizure.

An example of such a lubricating structure for a piston pin for an internal combustion engine is disclosed in, for example, Japanese Utility Model Publication No. 61-21560. This forms an oil groove extending in the axial direction of the piston pin hole from the outer peripheral edge of the piston body on the inner peripheral surface of the piston pin hole of the piston body, and the lubricating oil introduced into the oil groove is further rotated by rotation of the piston pin. An oil film is formed by being guided to a sliding surface between the piston pin and the piston pin hole.

[Problems to be solved by the invention]

However, the conventional piston pin lubrication structure described above
Since the oil groove is formed in the piston main body, stress concentration due to the above-described load is easily generated in the oil groove portion, and metal fatigue is easily generated since the load always acts on the oil groove portion in the same state. However, there is a problem that it is disadvantageous in strength. Further, due to the structure in which the oil groove is formed in the piston main body, metal fine powder generated due to wear of the piston main body and the piston pin tends to remain in the oil groove, and as a result, wear is particularly caused by abrasion of the Si-based metal fine powder. There is a problem that is promoted.

The present invention has been made to solve the above-mentioned conventional problems, and a lubricating structure of a piston pin for an internal combustion engine which can reliably remove metal fine powder on a sliding surface to avoid abrasion and is advantageous in strength. It is intended to provide.

[Means for solving the problem]

Therefore, the present invention provides a lubricating structure for a piston pin for an internal combustion engine for connecting a piston and a connecting rod, wherein the piston pin is rotatably inserted into a piston pin hole formed through a boss portion of the piston. The axial movement is restricted by the snap ring fitted in the annular grooves at both ends of the piston pin, a needle bearing is interposed between the piston pin and the connecting rod, and an oil groove extending in the axial direction is formed on the outer surface of the piston pin. Then, the outer end of the oil groove is located on the end face of the piston pin, and the inner end is located inside the inner end of the boss portion of the piston. The cross section is substantially semicircular so that the lubricating oil introduced into the inner portion from the inner end flows through the oil groove to the outer portion from the snap ring of the piston pin hole, and at least the lubricating oil is formed. Bottom end is characterized in that the intended depth located piston pin radially inward than the inner diameter of the snap ring.

Here, the oil groove of the present invention may be started from the end face of the piston pin as described above, or may be started in the middle and extend inward from the boss portion. More preferably, it extends more inward.

[Action]

According to the piston pin lubrication structure of the present invention, an oil groove is formed on the outer surface of the piston pin, the outer end of the oil groove is on the end face of the piston pin, and the inner end is on the inner side of the boss of the piston. Since the lubricating oil is located, the lubricating oil is introduced between the piston pin and the piston pin hole through the oil groove, and an oil film is formed between the two, so that a lubricating effect is obtained. Further, the oil groove rotates along the inner peripheral surface of the piston pin hole with the rotation of the piston pin. The resulting metal fine powder is collected in the oil groove. Further, since the metal fine powder is open at the inner end or the outer end of the oil groove inward or outward, the metal fine powder is collected outside the oil groove. As a result, abrasion due to the fine metal powder can be avoided. In addition, since the oil groove has a substantially semicircular cross-section and a depth at which the bottom surface of at least the outer end is located inside the inner diameter of the snap ring, the outer end of the oil groove is closed by the snap ring. Thus, the problem that the flow of the lubricating oil is obstructed can be avoided, and the above-described lubricity can be ensured.

Also, since the present invention has a structure in which an oil groove is formed in the piston pin, stress concentration does not occur in the piston body,
Also, since the position of the oil groove changes with the rotation of the piston pin, it does not receive the combustion pressure and inertia force in the same state,
As a result, there is no possibility that metal fatigue occurs as compared with a case where a load is always applied in the same state as in the conventional structure, and this is advantageous in strength.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 3 are views for explaining a lubrication structure of a piston pin for an internal combustion engine according to one embodiment of the present invention. In this embodiment, a case where the present invention is applied to a two-cycle engine will be described as an example.

In the figure, reference numeral 1 denotes a two-stroke engine, which is configured by connecting a cylinder block 2 on a crankcase 13 and disposing a cylinder head 4 on an upper surface of the cylinder block 2. The piston body 3 is inserted so as to be movable up and down. On the lower surface of the cylinder head 4 is formed a recess which forms the combustion chamber 5 with the piston body 3, and the ignition plug 4a is inserted into this portion.

A crankshaft 6 is provided in the crankcase 13, and the shaft 6 is connected to the piston body 3 via a connecting rod 7. This connecting rod 7
Is composed of a small end 7a and a large end 7b. The large end 7b is connected to the crankshaft 6, and the small end 7a is connected to the piston body 3, respectively. Reference numeral 2a denotes a scavenging port, which communicates with the combustion chamber 5 when the piston body 3 descends.

Bosses 3a, 3a extending in the radial direction are formed on the inner wall of the piston body 3, respectively, and a piston pin hole 3b is formed through the boss 3a. A needle bearing 1 of the connecting rod 7 is provided between the bosses 3a.
The small end portion 7a provided with 1 is located, and a cylindrical piston pin 9 is rotatably inserted into the piston pin hole 3b and the needle bearing 11. The axial movement of the piston pin 9 is restricted by a snap ring 10 fitted in an annular groove at both ends of the piston pin hole 3b. Thus, the piston body 3 is connected to the crankshaft 6 by the connecting rod 7.

Oil grooves 12 are formed at both ends of the outer surface of the piston pin 9. Each oil groove 12 has a circular arc shape in cross section, extends in the axial direction, and is formed so as to be inclined so as to be shallower toward the inner end 12a. Also this oil groove
The inner end 12a of the boss 12 is located slightly inside the inner end 3c of the boss 3b, and the outer end 12b is located on the end face 9 of the piston pin 9.
a, and its bottom surface is located inside the inner diameter of the snap ring 10.

 Next, the operation and effect of this embodiment will be described.

In the two-stroke engine 1 of the present embodiment, when the piston body 3 is lowered during the explosion stroke, the air-fuel mixture containing the lubricating oil sucked into the crank chamber is pressurized, and the pressure in the crank chamber is increased. Lubricating oil, oil groove 12
Is supplied mainly from the inner end 12a side. The lubricating oil in the oil groove 12 is supplied to the entire inner peripheral surface of the piston pin hole 3b as the piston pin 9 rotates,
A thin oil film is formed between 3b and the piston pin 9. Thereby, good lubrication is performed, and wear and seizure can be prevented. Also, in this case, the oil groove 12 moves so as to sweep the inner peripheral surface of the piston hole 3b with the rotation of the piston pin 9, so that the fine metal powder between them is collected in the oil groove 12. The collected metal fine powder is discharged from the outer end 12b of the oil groove 12 due to the intrusion of the lubricating oil due to the pressure increase in the crank chamber. Incidentally, the metal fine powder contains very hard Si powder, and if it remains between the piston pin and the piston pin hole without being removed, it is liable to be worn.

As described above, according to the piston pin lubrication structure of the present embodiment, the oil groove 12 is formed on the piston pin 9 side, and the inner end 12a of the oil groove 12 is located inside the inner end 3c of the boss 3a, Since 12b is located on the end face 9a of the piston pin 9, good lubrication is performed by introducing the lubricating oil as described above, and further, the fine metal powder can be discharged from the sliding surface while being collected. Wear can be greatly reduced.

Further, in this embodiment, since the oil groove 12 of the piston pin 9 rotates and constantly changes its position, the oil groove 12 does not receive a load in the same state, and compared with the conventional case where the oil groove is formed on the piston body side. Metal fatigue is less likely to occur, which is advantageous in strength. Further, since the oil groove 12 of the present embodiment has a structure formed on the outer surface of the piston pin 9, it is easier to process than the conventional case in which the oil groove 12 is formed on the inner peripheral surface of the boss portion of the piston.

In the above embodiment, the case where only one oil groove 12 is formed at both ends in the axial direction of the piston pin 9 has been described as an example. However, in the present invention, this oil groove 12 is formed at a plurality of locations in the circumferential direction. In this case, the same effect as in the above embodiment can be obtained.

Further, in the above embodiment, the case where the present invention is applied to a two-stroke engine is taken as an example. However, the present invention can of course be applied to a four-stroke engine. In this case, the lubricating oil scraped off by the oil ring travels along the piston body. It is supplied into the oil groove.

FIG. 4 is a diagram showing a modification of the above embodiment.

4 (a) and (e) show both end faces of the piston pin 9.
This is an example in which the oil groove 20 is formed between 9a, 9a. In this case, the metal fine powder flows out from the center 20a and both ends 20b of the oil groove 20. In this modification, since the oil groove 20 is also formed at the center of the piston pin, a flat bearing is used for connecting the connecting rod.

4 (d) and (h) show the outer end 23 of the oil groove 23.
This is an example in which b is located on the end face 9a of the piston pin 9 and the depth of the groove is constant. In any of the above modifications, the same effect as in the above embodiment can be obtained.

〔The invention's effect〕

As described above, according to the lubrication structure of the piston pin for an internal combustion engine according to the present invention, the oil groove is formed on the outer surface of the piston pin, and the outer end of the oil groove is located on the end surface of the piston pin. Since the end is located inside the boss of the piston, lubricating oil can be reliably supplied to the sliding surface, metal fine powder on the sliding surface can be reliably removed, and wear can be significantly suppressed. Yes, and also advantageous in strength,
In addition, since at least the outer end of the oil groove is formed at a depth such that the bottom surface is located inside the inner diameter of the snap ring, the snap ring does not hinder the flow of the lubricating oil. There is.

[Brief description of the drawings]

1 to 3 are views for explaining a lubricating structure of a piston pin for a two-stroke engine according to one embodiment of the present invention. FIG. 1 is a cross-sectional view of the piston, and FIG. FIG. 2 (b) is a cross-sectional view of the piston pin, FIG. 2 (b) is a side view thereof, FIG. 3 is a partial cross-sectional view showing a two-cycle engine, and FIG. 4 (a) and 4 (d) are cross-sectional views thereof, and FIGS. 4 (e) and 4 (h) are side views thereof. In the figure, 1 is a two-cycle engine (internal combustion engine), 3
Is a piston body, 3a is a boss, 7 is a connecting rod, 9 is a piston pin, 9a is an end face of the piston pin, 12, 20, and 23 are oil grooves, 12a, 20a, and 23a are inner ends, and 12b, 20b, and 23b. Are the outer ends, respectively.

Claims (1)

(57) [Claims] In a lubrication structure for a piston pin for an internal combustion engine for connecting a piston and a connecting rod, the piston pin is rotatably inserted into a piston pin hole formed through a boss portion of the piston. The axial movement is restricted by the snap ring fitted in the annular grooves at both ends of the piston pin, a needle bearing is interposed between the piston pin and the connecting rod, and an oil groove extending in the axial direction is formed on the outer surface of the piston pin. Then, the outer end of the oil groove is located on the end face of the piston pin, and the inner end is located inside the inner end of the boss portion of the piston. A substantially semicircular cross-section so that lubricating oil introduced into an inner part from the inner end flows through the oil groove to an outer part of the snap ring of the piston pin hole, and at least an outer end thereof; Lubrication structure bottom of the piston pin for an internal combustion engine, characterized in that were of depth located piston pin radially inward than the inner diameter of the snap ring.