JPH0451020Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention relates to the pistons of diesel engines, for example, and is particularly applicable to pistons with a high heat load, without being subject to various dimensional restrictions. This invention relates to a piston in which a ring trager and an annular cooling pipe are integrally cast in order to efficiently cool an annular groove for mounting a top ring.

[Conventional technology]

A conventional piston made of aluminum for a diesel engine will be explained with reference to FIG. A ring trager 12 is integrally cast into the upper side surface of the piston 10 so that its outer periphery is exposed, and a top ring (not shown) is attached to the outer periphery of the ring trager 12. An annular groove 14 is formed. A direct combustion chamber recess 16 is formed in the center of the upper surface of the piston 10. Annular cavity 18
is formed using a salt core or the like, and is located at approximately the same distance from the inner peripheral surface of the ring trager 12 and the surface of the direct combustion chamber recess 16. The oil supply hole 20 extends upward from the bottom of the piston 10,
An annular cavity 18 is reached. The jetted oil 22 spouted from the oil jet (not shown) reaches the lower end of the oil supply hole 20, and the oil is guided to the annular cavity 18 through the oil supply hole 20, and then the oil is introduced into the annular groove 1.
4 and the recess 16 for the direct combustion chamber. Note that the annular groove 30 is not yet formed before or during casting, and is formed by cutting or the like on the outer peripheral surface of the ring trager 12 after the piston 10 is cast.

The annular cavity 18 is formed using a salt core or the like, but in order to ensure a predetermined strength of the piston 10, the annular cavity 18 is directly connected to the inner peripheral surface of the ring trager 12 and the combustion chamber recess 16. The distance to the wall of the salt core needs to be set to an appropriate value, and there are many design constraints such as the position and dimensions of the salt core and their accuracy. In addition, for direct injection diesel engine pistons with small bore diameters, pistons with low compression heights, and pistons with height springs, it is difficult to form the annular cavity 18 with a salt core or the like in terms of ensuring strength. It's summery.

[Problem that the invention attempts to solve]

Therefore, this applicant disclosed a piston structure as shown in FIGS. 4 and 5 in a previous utility model registration application. In FIG. 4, in the aluminum piston 10 for a diesel engine, the annular cooling pipe 24 has a circumferential cross section, goes around the ring trager 12 in the circumferential direction, and has an annular cavity 18 inside. are divided. The annular cooling pipe 24 is fixed to the inner periphery of the ring trager 12 by press fitting or brazing, and the outer periphery of the annular cooling pipe 24 is fixed to the inner periphery of the ring trager 12. The annular cooling pipe 24 is integrally cast with the ring trager 12 while being fixed to the inner peripheral portion of the ring trager 12 . The oil supply hole 26 is formed using a drill or the like after the piston 10 is cast.
The annular cavity 18 extends in the axial direction of the annular cooling pipe 24 , opens at the lower end into a stepped portion around the lower opening of the piston 10 , and penetrates the lower part of the annular cooling pipe 24 at the upper end.
has reached.

The oil 22 ejected from an oil jet (not shown) is ejected toward the lower end opening of the oil supply hole 26 and introduced into the oil supply hole 26 . The cooling oil then enters the annular cavity 18 in the annular cooling pipe 24 through the oil supply hole 26 and flows along the annular cavity 18 . At that time, the annular groove 14
and directly absorbs heat from the walls of the combustion chamber recess 16 and cools them.

Thus, the piston structure shown in FIG. 4 provides the following advantages. (a) An annular cavity through which cooling oil flows is formed in the annular cooling pipe 24, and the outer circumference of the annular cooling pipe 24 is fixed to the inner circumference of the ring trager 12 by press fitting etc. Since it is integrally cast, the annular cavity 18 can be formed without reducing the strength of the upper part of the piston. (b) Furthermore, since this annular cavity 18 exists in a position extremely close to the inner circumference of the ring trager 12, the ring trager 12
The two annular grooves 14 can be efficiently cooled. (c) In addition, when forming the annular cavity 18, the annular cavity 1 of the ring trager 12 is formed without using a salt core or the like.
8 is formed, the accuracy of the dimensions, position, etc. of the annular cavity 18 is improved, design constraints are reduced, manufacturing is simplified, and manufacturing costs can be reduced.

However, as shown in detail in FIG. 5, the range of the annular cooling pipe 24 where the oil supply hole 26 is not formed, the annular outer circumference of the annular cooling pipe 24 and the ring tray are located at the lower part of the annular cooling pipe 24. An upper closed gap 28 is formed between the piston 10 and the annular inner circumferential portion of the piston 12, and when the piston 10 is cast, hot water does not flow sufficiently into the upper closed gap 28, and casting defects are likely to occur in this portion.

The purpose of this invention is to reliably avoid casting defects in pistons in which the annular cooling pipe that guides oil for cooling the Ring Trager is fixed to the inner peripheral side of the Ring Trager and is integrally cast with the Ring Trager. That's true.

[Means for solving problems]

According to the piston of this invention, the ring trager is fitted with a top ring in the annular groove on its outer periphery, and the annular cooling pipe is fixed to the inner periphery of the ring trager at its outer periphery to cool the ring trager. The oil is guided, the ring trager and the annular cooling pipe are cast together. Communication grooves that communicate the upper and lower surfaces of the annular cooling pipe are formed at appropriate intervals in the circumferential direction on the inner peripheral portion of the ring trager.

〔Example〕

This invention will be explained below with reference to the embodiments shown in FIGS. 1 to 3.

1 and 2 show an embodiment of this invention, in which FIG. 1 is a longitudinal sectional view, and FIG. 2 is a ring trager 12 and an annular cooling pipe 2 assembled together.
4 from below. Annular cooling pipe 2
The outer peripheral part 30 of 4 is the inner peripheral part 3 of the ring trager 12.
2, and the ring trager 12 and the annular cooling pipe 24 are integrally cast. The communication groove 34 is
The piston 10 has an arcuate cross section in the cross-sectional direction, and is formed on the inner peripheral part 32 of the ring trager 12 at equal angular intervals in the circumferential direction, for example, at 45° intervals. It has an opening width. The outer peripheral portion 30 of the annular cooling pipe 24 is separated from the bottom surface of the communication groove 34 at the location of each communication groove 34 and has a predetermined gap between it and the bottom surface, so that the lower surface side of the annular cooling pipe 24 is separated from the bottom surface of the communication groove 34. It communicates with the upper surface side through.

FIG. 3 is a view showing the ring trager 12 and the annular cooling pipe 24 assembled to each other in the piston of the second embodiment from below. In this embodiment, the communication groove 36 has an arcuate cross section with respect to the transverse direction of the piston 10, and similarly to the communication groove 34 in FIG.
2, are formed at equal angular intervals in the circumferential direction, for example, at 45° intervals, and have a predetermined opening width in the circumferential direction of the ring trager 12, and communicate the lower surface side of the annular cooling pipe 24 with the upper surface side. .

When the piston 10 is cast, as indicated by the upper closed recess 28 in FIG.
2 and the lower surface side of the annular cooling pipe 24, the inner peripheral part 32 of the ring trager 12 and the annular cooling pipe 2
A downward recess is formed between the outer circumferential portion 30 of No. 4 and the outer peripheral portion 30 of No. 4.
However, the air bubbles in this downward recess are caused by the communication groove 34,
36 to the upper surface of the annular cooling pipe 24, the hot water can smoothly enter this downward recess.

[Effect of idea]

As described above, according to the piston of this invention, communication grooves that communicate the upper surface side and the lower surface side of the annular cooling pipe are formed at appropriate intervals in the circumferential direction in the inner peripheral portion of the ring trager. Therefore, when the piston is cast, air bubbles in the downward recess that are formed between the inner periphery of the ring trager and the outer periphery of the annular cooling pipe on the lower surface side of the ring trager and the annular cooling pipe are The hot water escapes upward through the communication groove in the inner circumference of the piston, and as a result, the hot water smoothly enters the downward recess, thereby preventing the occurrence of casting defects in the piston.

[Brief explanation of drawings]

1 and 2 relate to a first embodiment of this invention, in which FIG. 1 is a longitudinal sectional view, FIG. 2 is a view from below showing a ring trager and an annular cooling pipe assembled together; FIG. 3 is a view showing from below the ring trager and the annular cooling pipe that are assembled to each other in the piston of the second embodiment, and FIGS. 4 and 5 are the utility model patents previously filed by this applicant. Regarding the piston shown in the registration application, Fig. 4 is a half longitudinal sectional view of the piston where the oil supply hole is formed to guide cooling oil from the lower part of the piston to the annular cooling pipe, and Fig. 5 is the oil supply hole. FIG. 6 is an enlarged vertical cross-sectional view of the area of the annular cooling pipe where the piston is not formed, and FIG. 6 is a vertical cross-sectional view of a conventional piston. 10... Piston, 12... Ring Traga,
14... Annular groove, 24... Annular cooling pipe, 30
...Outer circumference, 32...Inner circumference, 34, 36...Communication groove.

Claims (1)

[Scope of utility model registration request] A ring trager is fitted with a top ring in an annular groove on its outer periphery, and an annular cooling pipe is fixed to the inner periphery of the ring trager at its outer periphery to guide cooling oil for the ring trager, In a piston in which a trailer and the annular cooling pipe are integrally cast, communication grooves are provided in the inner circumferential portion of the ring trailer at appropriate intervals in the circumferential direction to communicate the upper surface side and the lower surface side of the annular cooling pipe. A piston characterized by being formed of.