JPH0341075Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an engine piston in which a cooling hole is formed on the back surface of the piston to introduce injected oil to cool the piston.

BACKGROUND ART Engine pistons have heretofore been known in which a cooling hole is formed on the back surface of the piston, and injected oil from an oil jet is introduced into the piston to cool the piston. In this case, in order to increase cooling efficiency, it is necessary to send a large amount of oil into the cooling holes, but in order to do this, it is possible to direct the oil jet from the oil jet toward the cooling holes and introduce the oil directly into the cooling holes. Just do it like this. However, in this case, although the cooling efficiency increases in the piston portion near the cooling hole, the cooling efficiency in other portions is low, and the piston cannot be cooled uniformly. Therefore, when oil is injected onto the back surface of the piston other than the cooling hole, the oil collides with the back surface of the piston and spreads over the entire surface, reducing the amount of oil that can be introduced into the cooling hole and increasing the high temperature inside the cooling hole. The amount of exchange between cold oil and low-temperature supply oil may be reduced, and the purpose of providing cooling holes may be lost. If the injected oil is directed toward the cooling hole in this way, the uniform cooling effect of the piston will be inhibited, and if the oil is injected avoiding the cooling hole, the cooling effect of the cooling hole will be reduced.

Purpose This invention was made based on the above recognition,
The aim is to provide a piston of the type mentioned at the outset, which makes it possible to increase the amount of oil introduced into the cooling holes and also to improve the uniform cooling of the piston.

Configuration The present invention proposes a configuration in which an oil guide groove is formed on the back surface of the piston, and the guide groove opens into a cooling hole.

Effects According to the above configuration, since the oil is guided by the guide groove, the effect of uniformly cooling the piston is enhanced, and since the cooling hole opens into the guide groove,
The amount of oil introduced into the cooling holes also increases. The guide grooves also serve the purpose of increasing the contact area with the cooling oil, and also serve as cooling fins, helping to improve the heat dissipation effect.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Figures 1 and 2 show an example of a piston according to the present invention, and the back surface 2 of this piston 1 has an appropriate number of oils, three in the example shown, as also shown in Figures 3 and 4. A guide groove 3 is formed from left to right in FIG. Similarly, a suitable number of cooling holes 4 are provided on the back side 2 of the piston, and these holes are drilled, for example, by a drill. In the illustrated example, three cooling holes 4 are formed in the left side area of the piston back surface 2 in FIGS. 1 and 2, and three cooling holes 4 are formed in the right side area, and each cooling hole 4 is formed in the oil guide groove 3. It is open to

The piston 1 reciprocates in the direction of arrow A (FIG. 1) in a cylinder (not shown), and at this time, oil flows from the oil jet 5 shown in FIG. 6 is injected. Therefore, the oil that hits the piston back surface 2 passes through the guide groove 3 and flows over a wide range from the left side to the right side in FIGS. 1 and 2 as shown by arrow B, and then flows downward from the back surface 2. . Since the cooling oil flows over a wide area on the back surface 2 of the piston, the piston 1 receives a relatively uniform cooling effect. Moreover, since the cooling holes 4 open into the guide grooves 3, the oil flowing through the guide grooves 3 is effectively introduced into each cooling hole 4, with the help of the inertia of the cooling oil due to the vertical movement of the piston in the A direction. The hot oil in the hole is replaced with
The inside of the piston is cooled. That is, if oil is injected onto the back surface of the piston without providing the guide groove 3, this oil will spread widely on the back surface of the piston, and the amount of oil introduced into the cooling hole will be reduced, but with the guide groove 3 provided, By passing the oil here, the oil can be concentrated in the cooling holes, and the amount of oil introduced into the cooling holes 4 can be increased. In addition, if oil is injected directly toward the cooling hole without providing a guide groove, the amount of oil introduced into the cooling hole will increase, but since it will directly hit the opening of the cooling hole, the flow of oil in the cooling hole will be obstructed, resulting in uniform cooling of the piston. However, by providing the oil guide groove 3, the oil can pass through the groove 3, and the oil can flow over a wide range on the back surface of the piston, achieving a uniform cooling effect on the piston.

The oil guide groove 3 may be formed in a shape that is more recessed than the general case on the back surface of the piston.
If the guide groove 3 is formed at the bottom of the guide groove 3, the surface area of the piston back surface 2 can be expanded by the fins 7, which is advantageous because the piston cooling effect can be further enhanced.

The intended purpose of the present invention can be achieved by providing at least one oil guide groove and at least one cooling hole in each guide groove, and the number of these can be selected as necessary. Further, the extending direction of the guide groove and the location of the cooling holes can be set as appropriate.

Effects According to the piston according to the present invention, it has become possible to increase the amount of oil introduced into the cooling hole and to improve the uniform effect of the piston.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a piston according to the present invention, with holes for piston pins etc. omitted;
Fig. 2 is a bottom view of the piston shown in Fig. 1 as seen in the direction of the arrow, Fig. 3 is a sectional view taken along the - line in Fig. 2,
FIG. 4 is a sectional view taken along the line -- in FIG. 2. 1... Piston, 2... Back side, 3... Oil guide groove, 4... Cooling hole, 6... Oil.

Claims (1)

[Claims for Utility Model Registration] In an engine piston having a cooling hole formed on the back surface of the piston for introducing injected oil to cool the piston, at least one oil guide groove is formed on the back surface of the piston, and at least one oil guide groove is formed on the back surface of the piston. The piston is characterized in that the cooling hole opens into the oil guide groove.