Light Metal Cylinder Head for Internal Combustion Engines

The present invention relates to a light metal cylinder head for internal combustion engines, according to which a metal plate is arranged on the cylinder head bottom; along its outer circumference, the plate has a ring-shaped or annular insert.

Such metal plates are known. As a rule, the plates are made of gray cast iron, and are used with air-cooled self-ignition internal combustion engines, mainly with such engines having two-stage combustion, but they are also used with supercharged internal combustion engines in order to prevent the direct influence of the combustion gases upon the cylinder head bottom and thus to protect the light metal cylinder head against too high temperatures.

Such a cylinder head with a metal plate is described in German Patent No. 525696. In this disclosure the cylinder head is fastened to the metal plate by means of a screw connection. A part of the outer circumference of the cylinder pipe barrel is provided with a thread, and the cylinder pipe is screwed to the annular insert by means of a thread provided on the inner side of the insert.

The disadvantage of such a connection consists therein that upon heating, the cylinder head and the metal plate expand to a different degree in the radial direction, so that the screw connection between the metal plate and the cylinder pipe is subjected to shear action which can lead to screw breakage. Since the light metal cylinder head expands more strongly during heating than does the metal plate, the heat transfer between the metal plate and the cylinder head is not clearly defined. Consequently, the plate can become too hot and can deform, thus becoming unusable.

The object of the present invention is to arrange the metal plate in the cylinder head in such a way that, in spite of different materials, no leakiness can arise, and a defined heat transfer is obtained between the cylinder head and the metal plate.

This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a schematic cross sectional view of a portion of the inventive connection location between a cylinder head, metal plate, and cylinder pipe or barrel;

FIG. 2 is a view similar to that of FIG. 1, and shows another embodiment of the present invention; and

FIGS. 3-5 show still further embodiments of the present invention.

The light metal cylinder head of the present invention is characterized primarily in that the annular insert is arranged on the cylinder head and/or on the cylinder pipe or barrel in such a manner that, due to the different heat stresses arising during operation, forces are effective upon the metal plate in such a way that the metal plate engages against the cylinder head bottom. Hereby the advantage is attained that upon heating of the metal plate and of the cylinder head, as well as of the cylinder pipe, a force is effective upon the metal plate. Thus, the metal plate also engages against the cylinder head bottom with its entire surface during operation, so that a definite and uniform heat transfer is assured between the metal plate and the cylinder head bottom. Accordingly, localized overheating of the metal plate cannot occur, so that a distortion of the metal plate is definitely prevented.

The annular insert can be made of the same material as the metal plate, and can be formed in a unitary embodiment therewith. It is also possible, however, that the annular insert be embodied as a sleeve, on the inside of which an offset portion or shoulder is provided for receiving the metal plate; in this case, the annular insert is produced as a separate cylinder which on its inner mantle surface has an offset portion or shoulder upon which the metal plate engages and by means of which the metal plate is pressed against the cylinder head bottom. In this connection, it is expedient to provide a radial spacing between the metal plate and the annular insert.

Cooling ribs are provided expediently on those outer surfaces of the annular insert facing the surrounding air so that the annular insert remains as cool as possible, since it serves as a support for the metal plate which distorts under heat stress.

The following disclosure sets forth possibilities for fastening the metal plate with simple means on the cylinder head in such a way that forces due to the thermal stresses act upon the metal plate so that it engages more tightly against the cylinder head bottom.

Referring now to the drawings in detail, the figures thereof illustrate the schematically represented cylinder head 1, the metal plate 2, the cylinder pipe or barrel 3, and the annular insert 4.

As shown in FIG. 1, the annular insert 4 and the metal plate 2 form a unit. The annular insert 4 is connected with the metal plate 2 in such a manner that a dish or pan shape results. For improving the heat transfer, on the outer circumference of the annular insert 4, there are provided either a thread or short ribs, by means of which the metal plate 2 and the annular insert 4 are either screwed into the cylinder head 1 or are cast thereinto. In this way, the annular insert 4 is so anchored in the cylinder head 1 that its free end face simultaneously forms a part of the sealing surface with the cylinder pipe 3.

During the heating of the metal plate 2 as well as of the cylinder head 1, the two parts expand radially outwardly. Since the cylinder head 1 is made of light metal, it has a higher heat expansion coefficient than does the metal plate 2. Consequently, the expanding cylinder head 1 acts on the annular shaped insert 4, so that by way of the annular insert 4 forces are introduced into the metal plate 2 which press the metal plate 2 against the cylinder head bottom. This effect can also be aided thereby that the side of the metal plate facing the combustion chamber is concavely curved. Since the radial expansion of the cylinder head 1 is dependent upon the heating thereof, with increasing heating a force growing in strength will press the metal plate 2 more and more strongly against the cylinder head bottom, so that in all possible temperature ranges a defined heat transfer is made possible between the cylinder head bottom and the metal plate.

In FIG. 2, the annular insert 4a is likewise embodied in one piece or unitary with the metal plate 2a. In contrast to the arrangement according to FIG. 1, the annular insert of the metal plate 2a is, so to speak, embodied as a cover which has an axially extending radial surface radially surrounds the cylinder head bottom portion (which is axially extending and radially inwardly recessed). In contrast to the embodiment of FIG. 1, in the embodiment of FIG. 2 an annular collar, shoulder, or flange 5a is provided on that end face of the annular insert 4a facing the cylinder pipe 3a, and this flange surrounds the cylinder pipe 3a on its outer circumference fitting within a notch therein. Since the annular insert 4a now has an outer side facing the surrounding air, it is advantageous to provide this side with cooling ribs or vanes 6a. Consequently, the lower temperature level of the annular insert 4a is further reinforced relative to the metal plate 2a. Consequently, the insert 4a forms a practically rigid abutment surface for the cylinder head 1a which expands when subjected to heat. Also here, as in the embodiment of FIG. 1, the expanding cylinder head 1a exerts a force against the annular insert 4a in such a manner that the metal plate 2a, depending upon the force, is pressed more or less strongly against the cylinder head bottom. That side of the metal plate 2a facing the combustion chamber can likewise be concavely curved, so that the pressing thereof against the cylinder head bottom during heating is enhanced.

In the embodiment of FIG. 3, the metal plate 2b likewise is made in one piece or unitary with the annular insert 4b. However, in this embodiment, the metal plate 2b, with its annular insert 4b, is installed in the cylinder head bottom in such a way that the cylinder head bottom can expand freely radially outwardly upon heating. So that nevertheless a force, depending upon the heating of the structural parts, is effective on the metal plate 2b in such a manner that it is pressed more strongly against the cylinder head bottom, the end face of the cylinder barrel or pipe 3b is provided with a continuous annular flange or collar 7b, against the inner side of which the outer side of the annular extension 4b engages. The annular insert 4b in this embodiment is likewise provided with cooling ribs 6b.

Upon heating of the metal plate 2b, this plate is essentially precluded from a radial expansion by the annular insert 4b since this extension, on the one hand, is provided with cooling ribs 6b and consequently is considerably cooler than the metal plate 2b, and, on the other hand, is precluded from a radial expansion by the collar 7b of the cylinder pipe 3b. By the here likewise concavely curved side of the metal plate facing the combustion chamber, the pressing-on or engagement against the cylinder head bottom upon heating is additionally increased.

FIG. 4 shows a combination of the two arrangements of the annular extensions 4a and 4b of FIGS. 2 and 3; i.e., the cylinder head 1c is again surrounded externally by the annular extension 4c, whereas the cylinder pipe 3c has a continuous flange or collar 7c, against the inner side of which the outer side of the annular insert 4c engages. By this arrangement, the force reacting considerably to the heat expansion of the cylinder head and the metal plate is strengthened, so that the metal plate 2c is pressed with a very high pressure against the cylinder head bottom.

FIG. 5 illustrates how the metal plate 2d can be fastened on the annular insert 4d when they are embodied as two separate parts, with the annular insert 4b being provided with a shoulder 8d for receiving the metal plate 2d. In such a case, it is possible to produce the annular insert 4d of a different material than is used for the metal plate 2d, especially to undertake an optimization with regard to heat dissipation. Examples of metals which can be used include gray cast iron, cast steel, and spheroidal graphite cast iron (i.e., ferrous metals). The important thing to remember is that the metal plate and the insert must be of different material than the cylinder head.

Naturally also the examples of the annular insert with the metal plate illustrated in FIGS. 1 through 4 can be embodied as two separate pieces.

The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.