JPH0439384Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oil-cooled piston crown used in an internal combustion engine.

[Conventional technology]

Piston crowns for large-diameter, high-load internal combustion engines are exposed to high-temperature gas, so they must be actively cooled to prevent piston seizure. They are broadly classified and each has been put into practical use. Among these, oil-cooled piston crowns are increasingly being used for internal combustion engines because they can reduce cooling loss and simplify the structure.

[The problem that the idea aims to solve]

By the way, in oil-cooled piston crowns, the specific gravity of oil is light and the specific heat is small, so the heat transfer coefficient of the cooling surface is about 1/20 of that of water cooling under the same speed conditions, so the cooling effect is increased. It is now necessary to devise ways to measure this. Examples of this include a speed type in which the oil flow rate is partially increased, or a type in which a jet of oil is ejected near the cooling area. However, these devices are often subject to structural limitations, and it is currently difficult to obtain a sufficient cooling effect over all parts. In other words, when the piston crown 1 is cooled by the oil jet nozzles a and b in Fig. 2, when the cooling oil is jetted into the oil in the cooling chamber as shown in the right half of the figure, the pressure in the cooling chamber is high and the oil Since the resistance is large, the jet flow 14 is diffused, and its speed decreases when it reaches the cooling surface, which has the disadvantage that a sufficient heat transfer coefficient cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oil-cooled piston crown that overcomes the drawbacks of the conventional apparatus and provides a sufficiently high heat transfer coefficient when cooling the piston crown with oil.

[Means to solve the problem]

The present invention provides an oil-cooled piston crown in which cooling oil is jetted onto the inner surface of the piston crown to cool the piston crown. The first part that spouts cooling oil toward the cooling surface at the top of the piston crown.
a second cooling oil spouting nozzle that spouts cooling oil into a plurality of cooling holes drilled in the outer circumferential portion of the piston crown; It is characterized by having a vent pipe that opens near the first cooling oil jetting nozzle and whose lower end opens into the crankcase chamber.

[Effect]

Since the cooling chamber and crankcase chamber are communicated with each other by a ventilation pipe, there is no pressure difference between the two chambers, and the air in the crankcase chamber is supplied to the cooling chamber through the ventilation pipe, and the cooling oil in the cooling chamber is quickly discharged. be done. As a result, the cooling oil from the cooling oil jetting nozzle reaches the cooling surface of the piston crown without losing its initial velocity on the way.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The piston crown 1, piston skirt 2, and piston rod 3 are connected by bolts 21. 1b is a cooling chamber formed inside the piston crown 1; 12 is an upper ventilation pipe whose upper end opens into the cooling chamber 1b; and 13 whose upper end communicates with the upper communication pipe 12 and whose lower end opens into the crankcase chamber B. is the lower ventilation pipe,
The upper and lower vent pipes 12, 13 are attached to the piston rod 3 and crosshead pin 4, respectively. 7
2 is a cooling oil inlet pipe, 22 is a cooling oil inlet passage, 23 is a cooling oil outlet passage, 4 is a crosshead pin, and 11 is a bridge groove. 24 is a cooling oil reservoir, 25 is a large number of cooling holes drilled in the piston crown 1, and a and b are cooling oil jetting nozzles. The piston crown 1 includes a cooling oil jet nozzle a provided in the piston crown and a top cooling surface 1 of the piston crown provided in the oil sump casing 8.
It is cooled by cooling oil jetted from a cooling oil spouting nozzle b opening toward c. Also, due to the inertia caused by the reciprocating movement of the piston, the piston crown 1
The oil in the cooling chamber 1b also collides with the cooling surface of the piston crown 1 to cool the cooling surface. At this time, if the cooling chamber 1b is filled with oil and the pressure inside the cooling chamber 1b is high, the jets from the jet nozzles a and b and the upward flow of oil due to the inertia of the piston are blocked, and the jet nozzle a on the piston crown is blocked. , b has difficulty reaching the cooling surface.

In this invention, in order to prevent cooling oil from accumulating in the cooling chamber 1b, the crankcase chamber B and the cooling chamber 1b are
The air in the crankcase chamber B is sent to the cooling chamber 1b by communicating with them through communication pipes 13 and 12, thereby eliminating the pressure difference between the two chambers and facilitating the discharge of the cooling oil in the cooling chamber 1b. . Thereby, the cooling oil from the cooling oil jetting nozzles a and b reaches the cooling surface of the piston crown 1 without losing its initial velocity on the way. Although the air in the crankcase B contains oil mist, it is free of foreign matter and is clean and does not have any adverse effect on the piston crown.

The cooling oil in the cooling chamber 1b flows through a hollow part in the piston rod 3 partitioned by an oil outlet pipe 9, that is, an inlet passage 22.
The piston is cooled by jets from the jet nozzle b of the oil sump casing 8 and the jet nozzle a of the piston crown, and then the exit passage 23 in the oil outlet pipe 9
The oil is discharged into the crankcase chamber B through the oil outlet passage in the crosshead pin 4, and a portion of the oil is also discharged into the crankcase chamber B through the vent pipes 12 and 13.

[Effect of idea]

The larger the diameter of the piston crown of an internal combustion engine, the more severe the heat load becomes, and therefore an effective cooling means is required. The oil-cooled piston crown of this invention jets out the oil from the cooling nozzle as a jet in the air instead of in oil, and allows the oil to travel straight to the target cooling surface without losing its initial velocity on the way, ensuring sufficient heat transfer. In order to obtain the desired cooling rate, air is ejected from an air ejection nozzle into the cooling oil chamber of the piston crown, and is retained on the target cooling surface to maintain an air layer on the cooling surface. This improves the cooling efficiency of the piston crown, and prevents burnout of the piston crown top surface and scuffing of the piston and liner.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the structure of an oil-cooled piston crown according to the present invention, and FIG. 2 is an explanatory diagram of its operation. 1...Piston crown, 1b...Cooling chamber, 3...Piston rod, 12, 13...Vent pipe, a, b...Cooling oil jet nozzle, B...Crankcase chamber, C...
...Piston crown cooling oil chamber.

Claims (1)

[Scope of Claim for Utility Model Registration] In an oil-cooled piston crown that cools the inner surface of the piston crown by jetting cooling oil, a cooling oil reservoir formed at the center of the lower part of the piston crown is used to cool the piston crown. A first cooling oil spouting nozzle that spouts cooling oil toward the cooling surface at the top of the piston crown, and a first cooling oil jetting nozzle that spouts cooling oil toward the cooling surface at the top of the piston crown, and a first cooling oil jetting nozzle that jets cooling oil toward the cooling holes that are drilled in a plurality of holes on the outer periphery of the pistol crown. A second cooling oil spouting nozzle that spouts out water, and a vent pipe having an upper end opening near the first cooling oil spouting nozzle in the center of the cooling chamber and a lower end opening into the crankcase chamber. Oil-cooled piston crown.