Patent Publication Number: US-7900551-B2

Title: Piston for an internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of PCT/DE2006/002254 filed on Dec. 15, 2006, which claims priority under 35 U.S.C. §119 of German Application No. 10 2005 061 059.5 filed on Dec. 21, 2005. The international application under PCT article 21(2) was not published in English. 
     The invention relates to a piston for an internal combustion engine, in accordance with the preamble of claim  1 . 
     A piston is known from the published application DE 102 14 830 Al, which has a ring-shaped cooling channel disposed in the edge region on the piston crown side, which channel has an oil inlet opening on the side facing away from the piston crown, by way of which opening an oil spray nozzle sprays cooling oil into the cooling channel. The cooling channel is delimited radially on the outside by a molded-on part that carries the ring belt, and radially on the inside by the piston crown shaped to configure the combustion bowl, so that cooling oil flowing in the cooling channel can only cool the ring belt and the radially outer region of the combustion bowl. 
     A piston is known from the Japanese patent application JP 09 079116, in which the entire underside of the piston crown has cooling oil sprayed onto it, and is thereby cooled. 
     It is a disadvantage in this connection that neither in the Offenlegungsschrift DE 102 14 830 nor in the Japanese patent application JP 09 079116 are any measures provided that serve for cooling the pin bosses. 
     Proceeding from this, the invention is based on the task of avoiding the stated disadvantage of the state of the art. This task is accomplished with the characteristics that stand in the characterizing part of the main claim and the secondary claim. Practical embodiments of the invention are the object of the dependent claims. 
    
    
     
       Some exemplary embodiments of the invention will be described below, using the drawing. This shows: 
         FIG. 1  a section through a piston having a cooled ring insert, whose run-off bore is directed at the upper pin boss region, so that the oil running off out of the cooling channel of the ring insert can be used to cool the pin boss, 
         FIG. 2  a section along the line AA in  FIG. 1 , which shows an oil pocket formed into the upper pin boss region, whose function consists in storing oil for lubricating the piston pin, and 
         FIG. 3  the piston according to  FIG. 1  in section, in which the oil spray nozzle for introducing cooling oil into the cooling channel of the cooled ring inert is connected with another spray nozzle directed at the upper pin boss region, to form a double spray nozzle. 
         FIG. 4  a section on the left side of the drawing along line IV-IV from  FIG. 3  where the right side of the drawing is identical to the right side of  FIG. 3 . 
     
    
    
       FIG. 1  shows a sectional diagram of a piston  1  for an internal combustion engine, in the piston crown  2  of which a combustion bowl  3  is formed. The piston  1  can consist of steel, gray cast iron, aluminum or another light metal, such as magnesium, for example. In the piston-crown-side edge region of the piston  1 , a cooled ring insert  4  for a compression ring, not shown in the figure, is disposed, which insert has a ring-shaped cooling channel  5  radially on the inside. Facing away from the piston crown, the ring insert  4  is followed by a second groove  6  for another compression ring, and a third groove  7  for an oil control ring. A rotating piston skirt  9  is connected with the ring belt  8  formed from the ring insert  4  and the grooves  6  and  7 , which skirt has a pin boss  10 , in each instance, formed into the sides that lie radially opposite one another, each pin boss having a pin bore  11 . 
     The piston-crown-side regions  12  of the pin bosses  10  are reinforced radially on the inside, as can be seen particularly well also in  FIG. 4  (a section through the piston shown in  FIG. 3 , along the line IV-IV), thereby resulting, in these regions  12 , in a zenith  15  of the pin bores  11  that is enlarged radially towards the inside, a lower surface pressure of the pin on the zenith  15  of the pin bores  11 , and therefore in lesser wear of these regions of the pin bores  11 , which are subject to the greatest stress in engine operation. 
     Oil pockets  13  and  14  are formed into the radially inner sides of the piston-crown-side regions  12  of the pin bores  11 , the purpose of which pockets consists in storing oil during engine operation, which oil is utilized for improved lubrication of the piston pin (not shown in the figure). This additionally contributes to a reduction in the wear of the piston pin and the pin bore  11 . 
     The oil required for cooling the ring insert  4  is sprayed directly into the cooling channel  5  disposed radially within the ring insert  4 , by at least one oil spray nozzle  16 , by way of an oil run-in bore  17 , in each instance. After passing through the cooling channel  5 , the oil exits again from oil run-off bores  18 . The oil run-off bores  18  are oriented radially inward and in the direction of the regions  12  of the pin bosses  10 , seen in the direction facing away from the piston crown, so that the oil flowing out of the cooling channel  5  hits the piston-crown-side regions  12  of the pin bosses  10 , and thereby cools them. 
       FIG. 2  represents a partial section through the piston  1  in the piston-crown-side region  12  of the pin boss  10  along the line AA in  FIG. 1 , which shows the shape of the oil pocket  14 , in which oil for lubricating the piston pin, not shown in the figures, is stored. 
       FIG. 3  shows an embodiment of the oil spray nozzle  16 , which is connected with an additional spray nozzle  19 , whose function consists in cooling the piston-crown-side regions  12  of the pin bosses  10  by means of spraying them directly with oil  20 . The spray nozzles  16  and  19  are combined, in the present exemplary embodiment, to form an integrated double spray nozzle  21 , which is also disposed on the radially opposite side of the piston  1 , in advantageous manner, in order to cool the piston crown there by means of spraying it, as well, and at the same time, to introduce oil into the cooling channel  5  by way of the oil run-in opening situated there. 
     As shown in the figures, the cooling channel  5  can be part of a cooled ring insert  4 . However, it is also possible to dispose the cooling channel  5  at a distance from the ring insert, so that cooling of the combustion bowl  3  is thereby improved. Furthermore, it is sufficient, particularly in the case of smaller pistons, to cool only the pin boss  10 , exclusively using a spray nozzle  19 , by means of spray-on cooling, whereby the oil pockets  13 ,  14  for cooling and lubricating the pin boss  10  are filled with cooling oil. 
     REFERENCE SYMBOL LIST 
     
         
           1  piston 
           2  piston crown 
           3  combustion bowl 
           4  cooled ring insert 
           5  cooling channel 
           6  second groove 
           7  third groove 
           8  ring belt 
           9  piston skirt 
           10  pin boss 
           11  pin bore 
           12  piston-crown-side region of the pin boss  10   
           13 ,  14  oil pocket 
           15  zenith of the pin bore  11   
           16  oil spray nozzle 
           17  oil run-in bore 
           18  oil run-off bore 
           19  spray nozzle 
           20  oil 
           21  double spray nozzle 
           22  piston interior chamber