KR0178034B1 - Piston of internal combustion engine - Google Patents

Abstract

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Description

Combustion engine pistons

1 is a longitudinal sectional view of a piston according to the invention when mounted on top of a piston rod;

FIG. 2 is a cross sectional view of the piston, similar to FIG. 1 but with the transition portion between the annular rib and the piston head designed as a conical surface.

3 is a plan view of the piston viewed from the direction of arrow III-III of FIG. 2;

* Explanation of symbols for main parts of the drawings

1: piston head 2: side wall

5: rib 6: cross section

7: flange 8: piston rod

10: skirt member 13: bore

14 duct 15 central cavity

16: closed end 17: annular chamber

20: insertion part

The present invention relates to a piston for a combustion engine, and more particularly to a large marine diesel engine, in the form of an annular rib integrated with the piston head as a power transmission element between the piston and the piston rod. In such an engine, a plurality of bores uniformly distributed on the circumference are provided at the annular portion between the outer side of the annular rib and the side wall of the piston extending downward from the piston head. Each bore extends from the closed end toward the piston head almost parallel to the axis of the piston to create an outlet into the lower annular chamber. The rib is provided with a radial duct which, via the bore, serves as a fluid connection between the central cavity in the rib and the lower conversion chamber.

Said piston is disclosed in German Patent No. 3 7 02 694, according to the patent, only some of the bores have an associated duct, while the coolant is splash cooling from the annular chamber to the extra bore. Provided in a manner. As the piston reciprocates up and down within the cylinder of the engine, the piston coolant is pumped down into the annular chamber through the duct and the bore from the central cavity, dispersing below all the bores in this annular chamber. The duct has a diameter approximately equal to that of the bore, and after inflow into the bore, the piston coolant mainly moves in the longitudinal direction of the bore.

It is an object of the present invention to provide a piston with improved cooling.

In this respect, the piston according to the invention differs from that of the prior art in the following points. That is, each duct has a diameter sufficiently smaller than the associated bore, and the axis of the duct is nearly tangential to an imaginary cylinder coaxial with the bore and having a diameter of 0.4 to 0.6 times the bore diameter.

Because of the smaller diameter ducts compared to the bore, the coolant from the central cavity enters the bore as a concentrated jet with a relatively high flow rate, and due to the fact that the duct is displaced about the axis of the bore, the coolant is tangential in the bore. By flowing and making a strong rotation along the bore's wall, strong heat transfer from the wall to the coolant can be achieved, thus improving the cooling of the piston.

The piston according to the invention can be characterized in that the duct extends into each bore so that the cooling of the piston is improved by uniform cooling of all bores. In view of the fact that the duct has a small diameter, the piston maintains sufficient mechanical strength even when the annular rib is perforated by the duct to each bore.

According to a preferred embodiment of the present invention, the duct is open into the central cavity in the conical surface. The conical surface is coaxial with the piston and forms a transition region between the inner surface of the rib and the bottom of the piston head. This facilitates the machining of the radial duct and also has the advantage that the concentration of forces in the area around the outlet or opening of the duct in the transition region between the rib and the piston head is reduced.

In a preferred embodiment of the piston according to the invention in which all outer ends of the duct are arranged on the same side of the associated bore shaft, even cooling of the piston is achieved because the duct is distributed evenly on top of the annular rib.

The invention is now described by way of example, with reference to the accompanying drawings.

The illustrated piston has a concavely curved piston head 1, which is integrally formed with a piston side wall 2 facing downward on its circumference, the piston side wall 2 having four A groove 3 for the piston ring is provided. The groove 4 in the upper region of the side wall near the bottom of the upper side of the piston serves to receive a lifting tool when inserting and removing the piston into and out of the associated engine cylinder.

An annular rib 5 is provided which is integral with the piston head 1 and faces downward, in the embodiment shown the average diameter of the annular rib is about half of the piston diameter, which leads to a cross section 6 facing downward. Thus, several bolts 9 are fixed to the flange 7 on the piston rod 8. A separate annular skirt member 10 is bolted to the lower side of the side wall 2 and embedded in a circumferential slot in the flange along the inner circumference to the flange 7. It is sealed by).

Bolts 9 having a gap hole and a threaded hole, together with a threaded hole in the piston side wall 2 and a gap hole in the skirt member 10, appear on a plane that is a cross section of each figure for illustrative purposes. have.

At the site between the side wall 2 and the outside of the rib 5, the piston has a plurality of bores 13, which are closed towards the piston head 1 and at the ends spaced from the piston head. It extends into the lower annular chamber 17. At the closed end of the bore, the bore 13 is provided with a concave curved top. In this case, the bores 13 having an axis parallel to the longitudinal axis of the piston are equally spaced to form a partition 12 which acts as a reinforcing rib between the side wall 2 and the annular rib 5. .

In an embodiment not shown, the axis of the bore may form an angle of 0 to 5 degrees with respect to the longitudinal axis of the piston on the radial plane. This is in contrast to distributing the cooling effect in a desired way between the piston head 1 and the side wall 2 of the piston. If the axis of the bore is positioned to intersect the longitudinal axis of the piston, for example under the piston head, more intense cooling occurs along its circumference at the site of the piston ring and the piston head. In contrast, if the axis of the bore intersects the piston axis over the piston head, the arcuate portion of the piston head above the rib 5 can be cooled more strongly.

Each bore 13 is connected to a straight duct 14 extending from the inner side of the rib 5 close to the point where the duct 14 enters into the piston head 1 to the point close to the closed end 16 of the bore. Connected to the central cavity 15, the axis of the duct is oriented tangential to the imaginary cylinder coaxial with the bore and having a diameter that is 0.5 times the diameter of the bore, as shown.

In FIG. 1 the transition between the annular rib 5 and the piston head 1 is shown to have a uniform curvature in cross section, while the corresponding transition in FIG. 2 has the shape of a conical surface coaxial with the piston. According to the latter embodiment, the concentration of stress is reduced and the duct is facilitated.

The piston rod 8 has a central bore, which is divided into an inner flow passage 21 and an outer annular flow passage 19 by a tubular insert 20. The inner flow passage 21 is discharged from the top into the central cavity 15, while the outer flow passage 19 is closed by the insert 20 at the top. The lower annular chamber 17 in fluid connection with all mowers 13 is in fluid connection with the flow passage 19 via one or more cross bores 18 in the flange 7.

During operation of the engine, a piston coolant, preferably cooling oil, is supplied by means of a pump to the flow passage 21 in the piston rod 8 and the coolant is returned through the flow passage 19. When the piston moves upwards with increased acceleration, the coolant that may be in the piston is forced to return to the piston rod, but the coolant flows with decreasing acceleration when the piston reaches its top dead center. It flows upwardly through the passages 21 and 19 and also into the central cavity 15 and the bore 13, respectively. In the latter case, it also flows through the duct 18 and the lower annular chamber 17. In this stage of piston movement, the lower side of the piston head is cooled in a splash cooling manner. During the movement of the piston, the piston coolant is forced into the central cavity 15, from which it flows through the duct 14 into the bore, and due to the tangential flow into the bore, the coolant therein undergoes active rotation. The angular momentum vector of the flow is almost parallel to the direction of movement of the piston, so the rotation of the coolant is not disturbed by the movement of the piston. When the piston approaches the bottom dead center, the oil is forced out of the central cavity 15 and the bore 13 and recycled to the hollow piston rod, after which the cycle continues.

Claims (4)

As a power transmission element between the piston and the piston rod 8, a plurality of bores having annular ribs 5 integrated with the piston head, which are evenly distributed circumferentially, extend downward from the piston head 1. Provided in the annular portion between the piston side wall 2 and the outer side of the annular rib 5, each bore having an axis of the piston to make an outlet into the lower annular chamber 17 from the closed end towards the piston head. Extending substantially parallel to the ribs 5, the ribs 5 are provided with radial ducts 14 which provide fluid connection between the lower annular chamber and the central cavity 15 in the ribs 5 via the bore. In combustion engine pistons, such as marine large diesel engines, which are provided in a provided form, each duct has a diameter sufficiently smaller than the associated bore, the axis of the duct being coaxial with the bore, the diameter of the bore 13 A piston for a combustion engine, characterized in that it is substantially tangential in addition to the imaginary cylinder having a diameter of 0.4 to 0.6 times. The piston of claim 1 wherein the duct makes an outlet into each bore. 2. The duct according to claim 1, wherein the duct opens into the central cavity (15) in the conical surface, the conical surface being coaxial with the piston and between the inner surface of the piston head and the inner surface of the rib (5). A piston comprising a. The piston according to claim 1, wherein the outer ends of the ducts are all disposed on the same side of the associated bore axis.

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