JPH06249061A - Piston structure for internal combustion engine - Google Patents

Abstract

PURPOSE:To shorten the axial length of a piston and prevent working accuracy from degradation by a structure of the piston having a piston ring groove and piston pin hole overlapping each other or equivalent. CONSTITUTION:Head 2 has a piston pin hole 5 on the lower surface side and is provided on the outer periphery with a top land 8, top ring groove 6, second land 9, second ring groove 7 and third land 10. A compression ring 11 is attached to the top ring groove 6. The third land 10 is adapted to fit in a recessed part 12a on the inner periphery of an oil ring 12 and the upper half of the ring 12 is disposed in the second ring groove 7. Thus, the oil ring 12 is attached to the third land 10 with a function equivalent to the piston ring groove. About a half of width occupied by the ring 12 will suffice for the groove width necessary for the upper side of the third land 10 to attach the oil ring 12. Also, the third land 10 and piston pin hole 5 do not overlap each other in working.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a piston used in an internal combustion engine, and more particularly to a piston structure of an internal combustion engine in which mounting of a piston ring arranged adjacent to a piston pin hole is improved. is there.

[0002]

2. Description of the Related Art Conventionally, as a technique of this type, for example, a piston structure disclosed in Japanese Utility Model Laid-Open No. 2222648 can be cited. In this conventional technique, as shown in FIG. 4, an oil ring groove 21 for mounting an oil ring is provided.
And piston pin hole 22 for assembling the piston pin
And are formed so as to overlap each other in the axial direction of the piston 23. With this structure, the axial length of the piston 23 is shortened, so that the weight and the posture of the piston 23 are reduced.

[0003]

However, in the above-mentioned prior art, the oil ring groove 21 and the piston pin hole 22 overlap each other, so that there is the following problem in terms of manufacturing. That is, when the piston 23 is manufactured, the oil ring groove 21 and the piston pin hole 22 are processed separately in the front and rear. Therefore, when one of the oil ring groove 21 and the piston pin hole 22 is machined and then the other is machined, a part of the machining is interrupted at the previously machined portion, which may cause deterioration of machining accuracy. It was Therefore, in some cases, it was necessary to secure the processing accuracy by performing secondary processing or the like.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to shorten the axial length of the piston by a structure equivalent to that in which the piston ring groove and the piston pin hole are overlapped. It is possible to provide a piston structure of an internal combustion engine that is capable of achieving the above and does not cause a reduction in processing accuracy.

[0005]

In order to achieve the above object, according to the present invention, there is provided a piston for an internal combustion engine, the outer periphery of which has the same axial height as the upper end of a piston pin hole. It is intended that a protrusion extending in the circumferential direction is provided, and a piston ring that has a recess corresponding to the protrusion on the inner circumference and is fitted into the protrusion at the recess is provided.

[0006]

According to the above construction, since the recess of the piston ring is fitted in the projection, the piston ring is mounted on the projection with a function equivalent to that of the piston ring groove. Since the protrusion is a convex side to which the recess of the piston ring is fitted, the groove width for the piston ring required on the upper side of the protrusion is about half of the occupied width of the piston ring. Further, since the ridge is provided at the same axial height as the upper end of the piston pin hole, the ridge and the piston pin hole do not overlap each other to be machined.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the piston structure of an internal combustion engine according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a side view showing a part of the piston 1 in this embodiment with a part broken away, FIG. 2 is an enlarged sectional view showing a main part of FIG. 1, and FIG. It is a bottom view which fractures and shows a part of it. The piston 1 is provided with a substantially disc-shaped head 2 and a skirt 3 extending below the head 2. Between the head 2 and the skirt 3, a pair of piston pin bosses 4 are provided on the lower surface side of the head 2 and open outward in the front-rear direction of the piston 1. The inside of the piston pin boss 4 serves as a piston pin hole 5 for mounting the piston pin.

Two ring grooves, that is, a top ring groove 6 and a second ring groove 7, are provided on the outer circumference of the head 2. The top and bottom of each of the ring grooves 6 and 7 are a top land 8, a second land 9 and a third land 10 extending in the outer peripheral direction of the head 2. Further, in this embodiment, the protruding land is formed by the third land 10 located below the second ring groove 7. Here, while the outer diameters of the top land 8 and the second land 9 are set to be the same, that of the third land 10 is set to be slightly smaller than the others. The lower surface of the third land 10 is set to have the same axial height as the upper end of the piston pin hole 5.

The top ring groove 6 is fitted with a compression ring 11 as a piston ring. Further, a cutter ring type oil ring 12 as a piston ring is attached to the third land 10. That is, the recess 12a corresponding to the third land 10 is formed on the inner circumference of the oil ring 12. And
The oil ring 12 has the recess 12a in the third land 1
It is fitted with 0. The oil ring 12 is mounted so as to straddle the third land 10.
The upper half is arranged in the second ring groove 7, and most of the lower half is arranged on the lower surface side of the head 2. Further, another compression ring 13 is mounted in the second ring groove 7 between the oil ring 12 and the second land 9. That is, in this embodiment, the upper half of the oil ring 12 and the compression ring 13 are mounted together in the second ring groove 7.

The piston 1 constructed as described above is connected to one end of the connecting rod by a piston pin (not shown) mounted in the piston pin hole 5. Furthermore, piston 1
Is connected to a crankshaft (not shown) at the other end of the connecting rod, and is then mounted on a cylinder bore (not shown) of the internal combustion engine for use.

Therefore, the internal combustion engine is operated and the piston 1
When the cylinder moves downward, the excess lubricating oil adhering to the cylinder bore is scraped off by the oil ring 12.
Also, the combustion gas in the combustion chamber is generated by each compression ring 1
It is sealed by the action of 1, 13.

On the other hand, in the piston 1 of this embodiment, in the structure thereof, the concave portion 12a of the oil ring 12 is fitted in the third land 10 in a concavo-convex relationship. The oil ring 12 is mounted with the same function as the groove. And the third land 10 is the oil ring 1.
Since it is the convex side that is fitted into the second concave portion 12a,
The groove width for the oil ring 12 required on the upper side of the third land 10 is about half the width occupied by the oil ring 12. That is, in the piston 1 of this embodiment, a normal oil ring groove can be omitted, and after the oil ring groove is omitted, the oil ring 12 is mounted by about half of the occupied width of the ring. The width of the groove may be secured in the second ring groove 7.

As a result, the height of the head 2, the height from the top land 8 to the piston pin hole 5 (compression height), and the extension are increased by a structure equivalent to that of a normal piston ring groove and piston pin hole. As a result, the axial length of the piston 1 can be shortened.
Further, the position of the piston pin hole 5 in the piston 1 can be set higher, and thus the center of the rotation moment around the piston pin can be set higher.

Therefore, the posture of the piston 1 can be improved when the internal combustion engine is operating. As a result, it is possible to reduce the slap hammering sound and the like, and it is possible to improve the gas sealability by the compression rings 11 and 13. Further, since the normal oil ring groove can be omitted, the weight of the piston 1 can be reduced accordingly. Furthermore, since the axial length of the piston 1 can be shortened, the axial length of the cylinder bore can be shortened accordingly, and the cylinder block can be made lighter. Further, since the compression height can be shortened, the length of the connecting rod can be increased by that amount to increase the contact ratio, which in turn can improve fuel efficiency.

In addition, since the oil ring 12 has a channel-shaped cross section, the rigidity of the oil ring 12 itself can be increased. Therefore, the followability of the oil ring 12 with respect to the high-speed motion of the piston 1 can be improved and the oil consumption amount can be reduced.

In addition, since the third land 10 is provided at the same axial height as the upper end of the piston pin hole 5, the third land 10 and the piston pin hole 5 can be machined so as to overlap each other. Absent. Therefore, even if the third land 10 and the piston pin hole 5 are processed separately in the front and rear, there is no intermittent processing before and after the front and rear, and it is possible to prevent a decrease in the processing accuracy of the both 10, 5.
Therefore, it is possible to omit the secondary processing for securing the processing accuracy.

The present invention is not limited to the above-described embodiment, but may be implemented as follows with a part of the configuration appropriately changed without departing from the spirit of the invention. (1) In the above embodiment, the piston 1 is provided with two compression rings 11 and 13 in addition to the oil ring 12.
However, it is also possible to use a piston in which the number of compression rings is appropriately increased or decreased.

(2) In the above embodiment, the upper half of the oil ring 12 and the compression ring 13 are mounted together in the second ring groove 7, but the compression ring mounted in the second ring groove may be omitted. In this case, since the width of the second ring groove can be further narrowed, the axial length of the piston can be further narrowed.

[0020]

As described above in detail, according to the present invention, a ridge extending in the circumferential direction is provided on the outer periphery of the piston at the same axial height as the upper end of the piston pin hole, and the ridge is
The piston ring is fitted in the recess. Therefore, the piston ring is mounted on the ridge with the same function as the piston ring groove, and the groove width required on the upper side of the ridge is about half of the occupied width of the piston ring. Further, the protrusion and the piston pin hole do not overlap each other to be machined. As a result, the axial length of the piston can be shortened by the structure equivalent to that where the piston ring groove and the piston pin hole are overlapped. Moreover, it has an excellent effect that it is possible to prevent a reduction in processing accuracy.

[Brief description of drawings]

FIG. 1 is a side view showing a piston according to an embodiment of the present invention with a part thereof broken away.

FIG. 2 is an enlarged cross-sectional view of a main part of FIG. 1 in one embodiment.

FIG. 3 is a bottom view of the piston according to the embodiment with a part thereof cut away.

FIG. 4 is a front view showing a conventional piston.

[Explanation of symbols] 2 ... Head, 3 ... Skirt, 5 ... Piston pin hole, 10
... third land as a ridge, 12 ... oil ring as a piston ring, 12a ... a recess.

Claims (1)

[Claims] 1. A piston for an internal combustion engine, wherein a protrusion extending in the circumferential direction is provided on the outer periphery of the piston at the same axial height as the upper end of a piston pin hole, and a recess corresponding to the protrusion is formed. A piston structure for an internal combustion engine, comprising a piston ring which is provided on an inner periphery and is fitted into the projection at a recess thereof.