US2863439A - Internal combustion engines - Google Patents

Description

United States Patent O INTERNAL COMBUSTION EN GINES Joseph Bischel, Mannhem, Germany, assignor to Motoren-Werke Mannheim A. G. vorm. Benz Abt. Stat. Motorenbau, Mannheim, Germany, a German company Applicationhebruary 12, 1958, Serial No. 714,818 Claims priority, application Germany February 28, 1957 9 Claims. (Cl. 123193 This invention relates to internal combustion engines and in particular to means for effecting a seal between a heavy metal cylinder of the engine and its associated light metal cylinder head. The invention has particular application to air cooled diesel engines.

It has been found in practice that the most satisfactory seal between a heavy metal cylinder and its light metal cylinder head is afforded when an end faceof the cylin der bears directly against an end face of the cylinder head without the interposition of a non-metallic packing element. Such a seal leads to more satisfactory operation of the engine than when a packing element is interposed in view of the fact that the cylinder and cylinder head are in direct -thermal contact with each other. It has been found, however, in hitherto proposed arrangements of this type that in use, the respective sealing surfaces of the cylinder and cylinder head become damaged by continuous contact with hot combustion gases and this damage leads in time to a defective seal.

In order to overcome this dsadvantage it has been proposed to form the respective bearing surfaces of the cylinder and of the cylinder head in such a way that an annular gap is formed between the baring surfaces and the interior of the cylinder chamber. In operation of the engine this gap which is known in the art by the term carbonisation path becomes substantially filled with combustion residue deposits, which deposits tend to protect the sealing surfaces from the effect of the hot combuston gases. In practical arrangements of this kind the cylinder head is formed with an annular collar around the mouth of the cylinder head which is adapted to engage at its inner surface a corresponding surface of a circular rim which extends from the main cylinder and surrounds the mouth of the cylinder. The engagement of the collar and rim is such as to leave an annular gap in which the combustion deposits collect and so prevent the passage of the hot combustion gases to the sealing surfaces of the collar and the rim. However, in view of the fact that the collar is made of a light metal and has a higher co-efficient of expansion than the cylinder rim which is made of a heavy metal, the collar undergoes more expansion than the rim during operation of the engine and in consequence the annular gap will be enlarged during this operation and an increased deposit of combustion residues will accumulate in this enlarged annular gap. When operation has stopped and the collar cools down it will, in consequence, contract but now the effective dimensions of the rim will be increased due to the excess combustion residues which have been de posited in the increased gap, and in consequence considerable contraction strains will be set up in the collar and these can, after a few cycles of expansion and contraction lead to the breakage of the collar. Furthermore, it has been found that with such a sealing arrangement the cylinder head and cylinder tend to adhere firmly together in the region of the oil carbon deposit and in consequence considerable force has to be employed in 2,863,439 Patented Dec. 9, 1958 order to separate them. The use of such force may of course result in damage to the cylinder or its head.

It is an object of the present invention to provide m an internal combustion engine means for effectinga seal between a cylinder and a light metal cylinder head in which the above mentioned dsadvantages are substantially avoided or reduced.

According to the present invention there-is provided an internal combustion engine comprsing a heavy metal cylinder and a light metal cylinder head, said cylinder having an opening around which is disposed an annular ridge-like rim, said rim being surrounded by an annular sealing surface of said cylinder, which surface is adapted to bear against a corresponding annular sealing surface formed on a heavy metal ring set into said cylinder head so as to surround an opening in said cylinder head, the arrangement being such that said sealing surfaces, when bearing against each other, are separated from the interior of said cylinder by a narrow annular gap formed between said rim and said ring, which gap becomes, upon operation of the engine, substantially blocked to the passage of combustion gases by the deposit therein of carbonisation residues.

For a better understanding of the invention and to show how the same may be carried into effect reference will now be made to the accompanying drawings, in which:

Figure 1 is a sectional elevation of part of a cylinder and cylinder head together with sealing means in accordance with the present invention; and

Figure 2 is a sectional elevation of part of the cylinder head and sealing means before machining.

Referring to the drawings, a light metal cylinder head 1 is formed with a peripheral annular collar, the inner surface of which is formed by one side of a heavy metal annular ring 2 cast into a suitable annular recess formed in the collar. The ring 2 may be suitably formed of cast iron and prior to its being cast in the recess is heated to a temperature of about 400 C. The under surface of the ring 2 is formed as a sealing surface 3 for a sealing engagement with a corresponding surface of a cylinder 9. The end of the ring 2 opposite the sealing surface 3 is given a curved surface 7 so as to substantially avoid notching in the region where the ring 2 is cast in. In order to prevent the ring 2 from becoming loosened in its light metal cylinder head mounting 1 the ring 2 is provided with a circumferental groove 4 which is' filled With the lightmetal which forms the cylinder head, thereby retaining the ring 2 in its mounting. After being cast in, the ring 2 and the cylinder head 1 are machined into a form shown in Figure 1 Thus that surface of the ring 2 which forms the inner wall of the annular collar is machined so as to provide a spherial recess in which can be fitted a complementary rim extending from the cylinder 9 and defining an opening into the cylinder 9. Furthermore, in order to prevent damage to the sealing surface 3 of the ring 2 when the cylinder head is placed upon a supporting surface this sealing surface 3 is formed by machining away the ring sufiiciently to allow for the adjacent cylinder head portion of the collar to project beyond the sealing surface 3.

A recess 5 is furthermore formed between the projecting the'tightening of tie rods used to secure the cylinder head of the cylinder.

When the cylinder head and cylinder are assembled as shown in Figure 1 the sealing surface 3 bears against the corresponding surface of the cylinder head and thereby effects a complete sealbetweenthe two parts. The inner surface of the ring 2 co-perateswith the corresponding outer surface of the annular rim extending from the cylinder to define a narrow carbonisaton path 10.

In operation of the device carbonisation residues will accumulate in the carbonisation path thereby effec tively blocking it to hot combustion gases which will now be unableto attack the sealing surfaces of the ring and cylinder. In view of the fact that the co-operating surfaces of the ring and cylinder which define the carbonisation path are formed of the same or similar heavy metals having the same or similar co-efficients of expansion, the expansion of the ring and the cylinder rim will be substantially equal and the carbonisation path will not increase substantially in dimensions during operation of the engine. In consequence the ring on cooling will not have to contract about excessive carbonisation deposits and cracking of the ring as in hitherto proposed arrangements should not take place. Furthermore, in view of the fact that undue contraction strains are in consequence not set up in the ring, there will be less tendency for the cylinder and cylinder head to adhere together, the cylinder head being readily detachable from the cylinder by means of for example a light hammer blow even after a lengthy period of operation.

In addition the fact that the collar is largely composed of a heavy metal ring having relatively high tensile strength enables the collar to Withstand contraction strain more effectively than a light metal collar. The fact that the heavy metal ring is cast into the cylinder head in such a way that it surrounds an inner cylinder head rim 12 ensures that in operation the ring and the surrounding light metal cylinder head are firmly pressed against one another as a result of differential heat expansion. There will thus be no opportunity for carbon residues to form between the engaging surfaces of the ring and cylinder head. Any resultant compression strain on the cylinder head itself has not been found to be detrimental whilst the ring itself readily withstands the resulting tension.

I claim:

1. In an internal combustion engine a heavy metal cylinder, a light metal cylinder head, an annular ridgelike rim on said cylinder defining an opening into said cylinder, an annular sealing surface of said cylinder disposed outside and around said rim, an annular heavy metal ring set into said cylinder head and forming a collar fitting around said rim and defining an opening into said cylinder head and a sealing surface on said ringfor bearing against said cylinder sealing surface.

2. In an internal combustion engine a heavy metal cylinder, a light meta] cylinder head, an annular ridgelike rim of said cylinder definng an opening into said cylinder, an annular sealing surface of said cylinder disposed outside and around said rim, an annular rim of said cylinder head defining an opening into said cylinder head, an annular heavy metal ring set into said cylinder head so as to surround said cylinder head rim, said ring forming a collar fitting around said rim of said cylinder, and a sealing surface on said ring for bearing against the corresponding sealing surface of said cylinder.

3. In an internal combustion engine, a combination according to claim 1, and furthermore comprising a further surface of said ring remote from its sealing surface, said further surface being in direct contact with said cylinder head and being at least partially curved.

4. In an internal combustion engine, a combination according to claim 2, and furthermore comprising a further surface of said ring remote from its sealing surface, said further surface being in direct contact with said cylinder head and being at least partially curved.

5. In an internal combustion engine, a combination according to claim 1, and furthermore comprising a lateral surface of said ring, said lateral surface being set into said cylinder head and having formed in it a circumferential groove which is filled with the material of said cylinder head.

6. In an internal combustion engine, a combination according to claim 2, and furthermore comprising a lateral surface of said ring, said lateral surface being set into said cylinder head and having formed in it a crcumferential groove which is filled with the material of said cylinder head.

7. In an internal combustion engine, a combination according to claim 1, and furthermore comprising an annular protectiveedge of said cylinder head surrounding the sealing surface of said ring and.projecting beyond said sealing surface.

8. In an internal combustion engine, a combination according to claim 2, and furthermore comprising an annular protective edge of said cylinder head surrounding the sealing surface of said ring and projecting beyond said sealing surface.

9. In an internal combustion engine, a combination according to claim 8 and wherein said ring is set into said cylinder head by casting.

No references cited.

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