Internal-combustion engines – Cooling – With jacketed head and/or cylinder
Reexamination Certificate
1999-07-20
2001-03-27
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Cooling
With jacketed head and/or cylinder
C123S041720
Reexamination Certificate
active
06205959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an engine block having at least one cooling duct extending in an intermediate wall between the cylinders, said wall having a minimum casting material thickness of less than 5 mm, also a casting mold for the manufacture of such an engine block, and a method for manufacturing such an engine block.
2. Description of the Related Art
In order to keep the length of an engine block, e.g. a cast aluminum block, as short as possible, efforts are made to arrange the cylinder cavities of a row of cylinders closely adjacent to one another. As a result, the intermediate walls between the cylinders are correspondingly thin. Because of the more closely adjacent combustion chambers and the reduced heat conduction, these thin intermediate walls are exposed to increased thermal stress, especially at the end of the cylinder face closest to the cylinder head. Consequently, it is necessary to provide a cooling duct in the intermediate wall.
It is known in the art that a cooling duct can be produced by machining, namely by cutting into the engine block from the cylinder head seating surface of the block and then sealing the opening shut. This leaves behind a cooling duct that connects sections of a cooling jacket enclosing the row of cylinders, said sections of the cooling jacket extending on opposite sides of the row of cylinders. Alternatively, the engine block is drilled into from the side in order to produce such a cooling duct, and afterwards the drilled passage between the cooling jacket and the outer surface of the engine block must be sealed shut again.
SUMMARY OF THE INVENTION
It is the purpose of the present invention to create an engine block of improved quality while reducing the effort involved in its manufacture.
This task is performed by an engine block according to the invention, characterized in that the cooling duct is bordered solely by a skin of casting material, i.e. the engine block according to the invention is produced in a casting mold in which, for the purpose of producing the cooling duct, a duct mold core, secured only at its ends, is arranged between the mold cores for the cylinder cavities.
In an engine block according to the invention, the strength and durability are increased in comparison with a known engine block of similar type by virtue of the fact that the cooling duct is formed without any machining, i.e. without intervening in the solidification structure of the cast material.
In a preferred embodiment of the invention, the cross sectional area of the cooling duct is reduced from its ends towards a transverse axis of the cooling duct that perpendicularly intersects the axes of the cylinders. This reduction in cross sectional area takes account of the fact that the wall between the cylinders is reduced in thickness as this transverse axis is approached. As the thickness of the intermediate wall increases on both sides, so the cross sectional area of the cooling duct also increases, thereby advantageously reducing the flow resistance of the duct and increasing the throughflow of coolant.
The minimum width of the cooling duct in the direction of the transverse duct axis perpendicularly intersecting the axes of the cylinders may range between 0.5 and 1.5 mm.
While it is conceivable for the cross sectional area to have any desired form, the cross sectional area of the duct is preferably elongate, with a longitudinal axis running parallel to the cylinder axes. While the width of the cooling duct is limited by the thickness of the wall between the cylinders, in the direction of the cylinder axes the cooling duct can widen to a relatively large extent, thus increasing the throughflow cross section.
In a preferred embodiment of the invention, the cooling duct extends in a straight line between oppositely arranged sections of a cooling jacket enclosing the row of cylinders.
The casting mold core is made of a material that is soluble in a liquid, or combustible, and/or brittle, namely in particular a salt, carbon and/or glass.
Once the casting material has been poured and has solidified, a salt core can be removed from the casting by dissolving it out. It is obvious that a soluble salt must be chosen that has a melting temperature above the temperature of the casting material used. A carbon core can be burnt out, for which purpose it may be necessary to supply oxygen to promote the combustion process. It is further conceivable that a pyrotechnical core material may be used, said material comprising carbon and an oxidizing agent added to the carbon, such that the composition of the material ensures full removal of the core by combustion while, however, avoiding explosive combustion.
A brittle glass core may be removed from a narrow cooling duct, even if the entrances to the cooling duct are not accessible to tools, by using, for example, ultrasonic means to shatter the core into small pieces. The glass core may be appropriately prepared for this process by being pre-stressed. Alternatively, the glass core may be removed by a pressurized water jet.
In a further preferred embodiment of the invention, the casting mold core is attached at its ends to a part of the casting mold possessing the cores for forming the cylinders. This measure ensures that the cooling duct is arranged in the prescribed position within the intermediate wall, with little deviation in tolerance, relative to the cores forming the cylinder cavities and thus relative to the cylinder cavities themselves. If the cooling duct mold were attached to another part of the casting mold, larger manufacturing tolerances would have to be accepted with respect to the positioning of the cooling duct due to fluctuations in the exactness of the fit of the casting mold parts relative to each other.
The invention will now be explained and described in more detail on the basis of embodiments and the attached drawings referring to these embodiments.
REFERENCES:
patent: 4446906 (1984-05-01), Ackerman et al.
patent: 4586553 (1986-05-01), Allen et al.
patent: 5217059 (1993-06-01), Kuhn et al.
patent: 3300924 (1984-07-01), None
patent: 3828093 (1989-03-01), None
patent: 0197365 (1986-10-01), None
patent: 2102317 (1983-02-01), None
Lellig Klaus
Smetan Herbert
Harris Katrina B.
Kueffner Friedrich
VAW alucast GmbH
Yuen Henry C.
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