Title of Invention: Piston for an internal combustion engine
Abstract: In a piston for an internal combustion engine, which includes in its top an annular cooling oil passage which, at one side of the piston, is in communication with a cooling oil supply passage extending axially through the piston and has a bottom opening through which cooling oil is supplied by an injection nozzle, and, opposite the cooling oil supply passage, a cooling oil return passage in communication with the annular cooling oil passage for removing the cooling oil therefrom, at least the cooling oil supply passage includes cooling oil retaining pockets which retain, during outward movement of the piston, part of the cooling oil supplied to the cooling oil supply passage and from which the retained cooling oil is dislodged and moved to the annular cooling oil passage during inward movement of the piston.
Detailed Description: Part PAC: DESCRIPTION OF A PREFERRED EMBODIMENTS
Part PAR: FIG. 1 shows a piston 1 disposed in a cylinder 2 of V-type internal combustion engine in which the cylinders are inclined. The piston 1 includes a head portion 3 with an annular cooling oil passage 4, which is in communication with an cooling oil supply passage 5 and a cooling oil return passage 6. The passages 5 and 6 extend essentially parallel to the piston axis 7 and are arranged diametrically opposite each other in a plane extending normal to the axis 8 and through the axial center of the piston pin 9.
Part PAR_2: The cooling oil is supplied to the oil supply passage 5 by a stationary injection nozzle 10 and then flows through the annular cooling oil passage 4, which it leaves through the oil return passage 6.
Part PAR_3: As shown in FIG. 1, the oil supply passage 5 is disposed above the longitudinal center axis 7 of the piston 1 and the oil return passage 6 is disposed below. In this way, the flow of cooling oil through the annular passages 4 is supported by gravity.
Part PAR_4: Along the lower inside wall of the supply passage 5 several oil retaining pockets 11 are arranged, one after the other, in such a way that they retain part of the oil supplied by the injection nozzle 10, when the piston moves outwardly that is toward its top dead center position. During the following inward return movement of the piston the oil retained in the pockets leaves the pocket and is thrown, together with the oil from the injection nozzle 10, into the annular cooling oil passage 4. In a similar way, the lower side of the oil return passage 6 may be provided with oil retaining pockets 12.
Part PAR_5: In order to increase the residence time of the cooling oil in the annular cooling oil passage 4, the annular cooling oil passage 4 may be provided with a spiral wall structure 13. The course of the spiral wall structure 13 is shown schematically in FIG. 3 by the cross-sections 3'-3' and 3"-3" given in dashed lines.
Part PAR_6: Instead of a spiral wall structure, or in addition thereto, the annular cooling oil passage in the cylinder head may also have the shape as shown in FIG. 4. In this case, the cooling oil passage 4a includes at its upper inner walls 14 inclined portions forming ramps 15 and, at its lower inner walls 16, troughs 17, which are displaced from the ramps 15 in circumferential direction. During return movement of the piston, the oil is thrown out of the troughs 17 against the ramp 15, whereby it is moved forwardly. Then, during the following outward movement of the piston 3, the oil is directed into the next downstream trough 17 as indicated by the arrows. In this way, a strong heat transfer is provided which is intensified by the increased residence time of the cooling oil in the troughs 17.


{'bibliographic_information': "{'Patent Number': '061642495', 'Series Code': '9', 'Application Number': '2674173', 'Application Type': '1', 'Art unit': '377', 'Application Filing Date': '19990312', 'Title of Invention': 'Piston for an internal combustion engine', 'Issue Date': '20001226', 'Number of Claims': '6', 'Exemplary Claim Number(s)': '1', 'Assistant Examiner': 'Harris; Katrina B.', 'Primary Examiner': 'Wolfe; Willis R.', 'Number of Drawing Sheets': '1', 'Number of figures': '4'}", 'source_file': './grant/2000/pftaps20001226_wk52.txt', 'source_data': 'USPTO-Grant'}