The invention relates to a cooled piston for an internal combustion engine, having a combustion bowl in the piston head, and a cooling channel that runs in ring shape at the height of the ring belt, which channel is closed off, at its end that is open towards the piston skirt, by means of a wall part that is appropriately shaped and provided with a cooling oil inlet and a cooling oil outlet, and is radially divided at least once on its circumference.
Such a piston is known, for example, from DE 199 26 568 A1, in which a wall part closes off the cooling channel, whereby the wall part is provided with several radially disposed cross-walls that extend axially into the cooling channel, distributed over the circumference of the wall part, in order to improve the heat removal. In this connection, the cross-walls divide the cooling channel into shaker spaces, i.e. sections having a constant size, in order to maintain a certain level of cooling oil in the cooling channel.
Furthermore, a multi-part, liquid-cooled piston for internal combustion engines is known from DE 27 23 619 C2, which has an oil guide ring at the cooling oil inlet of its cooling channel, which ring guides the cooling oil that runs into the cooling channel, along the periphery of the cooling channel, by means of a lip.
It is a general disadvantage of the aforementioned embodiments that the dwell time of the cooling oil in the cooling channel has not been satisfactorily solved and that a specific heat removal from the hot piston regions into the coolant, i.e. as a function of the temperatures that occur, cannot be implemented.
It is the aim of the invention to configure a cooling channel for a piston of an internal combustion engine in such a manner that improved location-dependent heat removal from the particularly hot piston regions is achieved, so that an approximately uniform temperature distribution in the cooling channel and therefore an optimal cooling effect of the piston is guaranteed.
This aim is accomplished by means of the characteristics of claim 1.
By means of the solution according to the invention, the result is advantageously achieved that the cold cooling oil that is introduced into the cooling channel is distributed with a very small volume on a first section of an oil guide ring, as compared with the entire cooling channel volume, and therefore an intimate contact with the wall surfaces to be cooled is produced by means of the shaker effect. The amount of heat introduced into the cooling oil, i.e. the cooling of the piston, is therefore high and intensive. In order to control the amount of heat to be absorbed by the cooling oil in such a manner that as uniform as possible a temperature distribution is achieved at the ring belt of the piston, the subsequent sections of the oil guide ring increase the cooling channel volume, in each instance, according to the invention, thereby correspondingly reducing the dwell time of the cooling oil on the wall surfaces to be cooled. The great temperature difference that exists between the cooling inlet (cold cooling oil) and the cooling oil outlet (hot cooling oil) is prevented, and thereby a cause for the formation of mechanical stresses in the region of the combustion chamber of the piston is also prevented.
Further advantageous embodiments are the object of the dependent claims.
The invention will be explained in greater detail below, using an exemplary embodiment. The drawing shows:
A piston 1 has a cooling channel 2 provided at the height of the ring belt, which channel is closed off, at its end that is open towards the piston skirt, by means of a two-part spring part 8, which possesses an opening that serves as the cooling oil inlet 5. An oil guide ring 3 that runs around the periphery, and is provided on its circumference with a cooling oil inlet, also referred to as 5, and a cooling oil outlet 6, is disposed in the cooling channel 2 in such a manner that it is supported on the spring part 8 and, with its outer wall part, on a recess 10, as shown in
The oil guide ring 3 has steps 9, symmetrically distributed over its circumference, between the cooling oil inlet and the cooling oil outlet, which steps form sections 4 between the steps, in each instance, which sections are disposed axially in the cooling channel 2, at different heights. Starting from the cooling oil inlet 5, the first section 4.1 or 4.1′ possesses the smallest volume, with reference to the total cooling channel volume, i.e. step 9 has a height h that corresponds to approximately 60 percent of the cooling channel height. Each of the subsequent steps of the sections 4.2 to 4.4, or 4.2′ to 4.4′, increase in size by approximately another 10 percent in height with reference to the first section. The distribution of the steps 9, and therefore the number, is defined by means of different arc angles α, β, γ, δ (in the clockwise direction, according to
Number | Date | Country | Kind |
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102 21 561.8 | May 2002 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE03/01534 | 5/13/2003 | WO | 11/12/2004 |