US1376620A - Cylinder-head for internal-combustion engines - Google Patents

Description

R. HILDEBRAND.

CYLiNDER HEAD FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED 050.4,1919.

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I I fi/fl/ae/Jfld R. HILDEBRAND.

CYLINDER HEAD FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED DEC. 4, 1919.

1 ,376,620. Patented May 3, 1921.

2 SHEETS-SHEET 2- frken/a/ UNITED STATES PATENT OFFICE.

CYLINDER-HEAD FOR INTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent.

Patented May 3, 1921.

Application filed'Decmber 4, 1919. Serial No. 342,371.

' To all whom it may concern Be it known that I, REINHARD HILDE- BRAND, a citizen of Germany, a resident of inder-Heads for Internal-Combustion Engines, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

This invention relates to improvements in cylinder heads for internal combustion engines, the invention being especially adapted for use in ver large internal combustion engines of the Diesel type, wherein the ignition is effected by compressingair to about 500 lbs. pressure per square inch, thereby producing a temperature of about 1000 F. The temperatures resulting from combustion usually range from about 2000 F. to 2500 F. Actual experience has shown that comparatively small Diesel engines of less than a few hundred horse-power can be carefully designed to withstand the stresses resulting from higher pressures and high temperatures, and it may appear that much larger engines could likewise be readily designed by merely copying the smaller designs, but this is not true. In fact, the very large Diesel engines have never been entirely successful. Their cylinder heads have not withstood severe stresses resultin from the intense heat and high pressure in the combustion chambers, this being especially true of engines having cylinders larger than 26 to 30 inches in diameter. Asa consequence, very large engines of the Diesel type, although highly economical so far as fuel is concerned. have not comeinto general use.

The cylinder heads of small engines form the top ivalls of comparatively small com-' bustion chambers, and by cooling these small heads injurious stresses can be avoided, but in a much larger engine. the combustion space is very large in comparison with the cooling surfaces of the walls of the combustion chamber, and owingto the increase in volume of the fuel without a corresponding increase in cooling area, the walls of the large combustion chambers are subjected to 1 comparatively high temperatures. Furthermore. the large combustion chamber is relatively high and very intense heat-1s generated at the center of the combustion chamcylinder.

her, as well as at the center of the cylinder head torming the top Wall thereof.

Owing to the extremely high temperatures at the central portions of large cylinder heads, and the lack of opportunity for p)r oper cooling, the cylinder heads of large iesel engines eventually crack near the center. Heat variations cause expansion and contraction of the cylinder head which is a complex casting containing valves and subected to high pressures, and great diificulty has therefore been experienced in designing large cylinder heads capable of withstanding even a brief period of service. The difiiculties of this problem are fully appreciated by engineers familiar with Diesel engines,

and the failure to produce very large en g nes of this type adapted to stand the heat and pressure without breakage in the cylinder heads clearly shows that there must be some unusual difliculties preventing a solution of this particular problem. I will, therefore, briefly point out conditions existing in cylinder heads of this kind, and endeavor to show Why the stresses do not result in breakage of my cylinder head.

The ordinary type of cylinder head has a central portion opposing the engine piston and exposed dlrectly to the highv pressures and intense heat resulting from combustion in the cylinder. This highly heated central portion 18 usually surrounded by a watercooled marginal portion seated upon the top of the cyllnder. Obviously, the water cooled margin tends to prevent expansion of the central portion, but the fire-heated central portion must expand, and as a result the large cylinder heads eventually crack near the center, as will be hereafter pointed out. If the cyllnder head could, during actual runn ng of the engine, be heated uniformly, and if it were free to expand and contract, there would be no severe stresses due to heat. Withthrs ideal condition in view, my object 18 to eliminate stresses which have heretofore resulted in fractures in-large cylinder heads.

F1gure I is a to view, partly in sect-ion, on the line II, ig. II, showing a cylinder head embodying the features of this invention. i

Fig. II is a section on the line II-II, Fig.

I, showing thecylinder head applied to a Fig. III is a section on the line III-III, Fig. I.

Fig. IV is a diagrammatical View showing the heat-exposed face of the cylinder head. Fig. V is a diagrammatical vertical section, showing the head applied to a cylinder.

1 designates the cylinder of an internal combustion engine, and 2 designates a piston adapted to reciprocate in the cylinder. To illustrate one form of the invention, I have shown a hollow cylinder head in the form of a single casting having a bottom wall E, side walls 3 and a to wall 4, all integrally connected together. il orts 5 are formed in the side walls 3 for the admission and discharge of cooling fluid, preferably water, which passes through the hollow cylinder head as suggested by arrows in F ig. II. The bottom of the cylinder head is only slightly larger than the internal diameter of the cylinder, and the marginal edges of this bottom are seated upon the top face of the cylinder. Vertical bolts 6 detachably secure the cylinder head to the cylinder. The upper portion of the head is extended to receive the bolts, or studs, which lie entirely beyond the heat-exposed lower portion of the head, said lower portion being free to expand in response to the action of heat generated in the combustion chamber.

The Diesel engine head is provided with the usual inlet port 7 for the admission of air, exhaust port 8 for the discharge of .products of combustion, and injector 9 whereby fuel is injected into the combustion chamber. To receive the injecting device an opening is formed in the center of the bottom wall E, at a; point directly bet-ween the inlet and exhaust ports, which are preferably formed in said bottom wall. A tube 9 surrounds the fuel injecting device, said tube being secured as shown in Fig. II.

Theory and actual experience show that the ordinary large cylinder head cracks in the direction A--B (Fig. IV), this being the typical Diesel head crack. It is gen erally termed a heat crack, for the stresses due to heat greatly exceed those due to pressure. While the engine is running, both of these stresses vary constantly, fluctuating in wide limits. 'After each ignition follows a rapid rise in temperature and consequently an increase in stress up to a maximum. Then follows a decrease, down to minimum until the compression stroke begins, when the temperature and consequently the stresses begin to increase. The fibers of the metal, therefore, are continually elonhead crack;

The ordinary Diesel head is ahollow 'casting having'central portions. exposed directly to the heat generated in the combustion chamber, and theseheat-exposed portions are surrounded by relatively cool marginal portions not directly exposed to the burning fuel. The marginal portions of the ordinary head are not only protected from direct action of the fire, but they are also cooled by water circulating through the cylinder head. It is obvious that the central portions of the cylinder head-bottom, being exposed directly to the fire, must expand, and if such expansion is effectively resisted, or prevented, destructive stresses are bound to occur. In the ordinary cylinder head having water-cooled margins protected from direct action of the fire, these relatively cool margins may be compared to a non-yielding collar shrunk onto the heat-exposed central por tions, and they very effectively oppose expansion of the central portions; Obviously, the heat-exposed central portions cannot freely expand it they'are surrounded by an integral non-expanding marginal portion.

Some advantage may be gained by making the cylinder head only slightly larger than the internal diameter of the cylinder, but this alone would not eliminate the destructive stresses due to a comparatively cool paratively non-expanding margin, it appears that expansion in the direction C--D is very-firmly opposed by the resistance at the margin, While in the direction A-B some expansion is permitted at the inlet and exhaust ports. The metal at these ports is yielding not only because the walls .of the ports can be forced to a slightly oval form, but primarily because it is cooled at these points, and thus contracted, by the comparatively' cool exhaust gases passing through one port and by the cold air passing through the other. I, therefore, believe it is especially desirable to relieve the stresses in the direction C-D. v

, Attention is now directed to Fig. I and to the diagrammatical view (Fig. IV) which show that the water-receiving chamber 'is elongated in the direction AB. Some expansion in this direction is permitted by physical displacement of the metal forming the ports, and by the cooling action of incoming and outgoing fluids tending to cause contraction of the metal forming the walls ofthe ports. However, we are faced with the problem of preventing destructive heat stressesin the direction C-D. The central tion, and since both theory. and actual practice show that these central portions are more intensely heatedthan the margins, -I

expose said central portions to the direct action of the cooling water. The marginal portions M, at opposite sides of the central portions, are exposed to heat transmitted from the combustion chamber, but not to the direction action of the cooling water. Therefore, the marginal portions on the line C-D will freely expand in repsonse to the action of the heat, thereby permitting and aiding expansion of the central portions in the direction CD. Instead of preventing expansion by the use of an integral nonexpanding margin around the heat exposed central portions, I have herein disclosed expanding marginal portions which cooperate with the central portions to permit expansion thereof, so as to eliminate stresses which have heretofore caused the typical Diesel head cracks.

Another advantage of the elongated, or oval, water chamber as compared with a circular one, lies in the fact that the oval wall can yield more easily in response to the expansion of the heat-exposed wall, but it is to be understood that the invention is not limited to a cooling chamber of any particular shape, nor to any particular means for cooling the cylinder head. Although I have shown inlet and exhaust ports in the cylinder head, it will likewise be understood that such ports may beformed at any suitable points in the engine. I am also aware that various modifications within the scope of the claims hereunto appended will suggest themselves to those skilled in the art.

The cylinder head I have shown to illustrate the invention has a bottom wall exposed directly to the heat generated in the combustion chamber. This bottom wall has expanding central portions from which heat is rapidly transmitted to prevent undue expansion thereof. Marginal portions of the bottom wall are exposed to the heat, but not to the direct action of the cooling medium,

so these heat-retaining expanding margins permit expansion of the expanding central portions.

ing from opposite sides of thewater-receiving chamberso as to overlap the top of the cylinder, as shown in Figs. II and V. The attaching bolts 6 do not prevent expansion of the margins. termed a differential cooling means, for it acts directly upon the heat-exposed central portions, but only indirectly upon the heat-exposed marginal portions M, said marginal portions being comparatively uncooled, so as to expand freely in response to the heat.

The side walls 3 of the water-receiving chamber are located directly above the The heat-retaining margins M are preferably in the form of flanges extend- The cooling device may be,

piston, where they serve as effective reinforcing means for the cylinder head. 'Herenuts 6, or from the pressure in the cylinder,

are transmitted through the walls 3 which overlie the combustion chamber, said walls 3 serving as compression members which are well adapted to withstand and transmit th stresses. 1

I claim:

1. An internal combustion engine having a cylinder head comprising a bottom wall, a top wall and a single continuous side wall, the bottom wall projecting beyond said side wall.

2. An internal combustion engine having a. cylinder head provided with top. and bottom walls and a wall connecting the same, the area inclosed by the bottom of said connecting Wall being smaller than said bottom wall and substantially in the form of an oval.

3. An internal combustion engine provided with a combustion chamber and a cylinder head, said cylinder head having expanding central portions from which heat is rapidly transmitted to prevent undue expansion thereof, said cylinder head also having heat-retaining expanding marginal portions permitting expansion of said expanding central portions, said heat-retaining expanding marginal portions being directly exposed to heat generated in the combustion chamber so as to expand in response to the action of the heat, and fastening means for the cylinder head permitting expansion of said heat-retaining expanding marginal portions.

4. In an internal combustion engine, a cylinder provided with a combustionchamher, and a cylinder head seated on said cylinder, said cylinder head having expanding central portions exposed directly to the heat of the combustion chamber, cooling means acting directly upon said expanding central portions to revent undue expansion thereof, said cylin er head having comparativelyuncooled heat-retaining expanding marginal portions permitting expansion of the cooled central portions, said heat-retaining expanding marginal portions of the cylinder head being directly exposed to the heat generated in the combustion chamber so as to expand freely in response to the action of the heat, and fastening means permitting expansion of said comparatit' 'ely uncooled marginal portions of the cylinder head.

5. An internal combustion engine provided with a combustion chamber and a cylinder head, said cylinder head having expanding central portions exposed directly to the heat of the combustion chamber and cooling means comprising a water-receiving chamber over said expanding central portions, sa1d expanding central portions belng exposed directly to the water to provide for a with a bottom wall, said bottom wall hav-- ing expanding central portions exposed directly to the heat of the combustion chamber, cooling means including a water-receiving chamber formed over said expanding central portions to prevent undue expansion thereof, said bottom wall also having relatively uncooled heat-retaining expanding marginal portions directly exposed to the heat generated in the combustion chamber so as to expand freely in response to the action of the heat, and fastening means whereby said cylinder'head is secured to permit free expansion of said relatively uncooled heat-retaining marginal portions of said bottom wall.

7. An internal combustion engine having a combustion chamber and a cylinder head, said cylinder head having cooling means including an elongated water-receiving chamber narrower than the cylinder head, the bottom wall of said elongated water-receiving chamber being exposed directly to the heat of the combustion chamber so as to expand in response to the action of the heat, said cylinder head also having relatively uncooled heat-retaining expanding marginal portions exposed to heat transmitted from said combustion chamber so as to expand freely in response to the action of the heat, and said heat-retaining expanding marginal portions being located at opposite sides of said elongated water-receiving chamber to permit expansion of said bottom Wall.

8. An internal combustion engine having acombustion chamber and a cylinder head, said cylinder head having cooling means in cluding an elongated water-receiving chamber narrower than the cylinder head, the bottom wall of said elongated water-receiving chambe being exposed directly to the heat of the combustion chamber so as to expand in response to the action of the heat, said cylinder head also having relatively uncooled heat-retaining expanding marginal flanges exposed to heat transmitted from said combustion chamber so as to expand freely in response to the action of the heat,

and said heat-retaining expanding marginal flanges being located at opposite sides of said elongated water-receiving chamber to permit expansion of said bottom wall 9. An internal combustion engine having a combustion chamber and a cylinder head, said cylinder head having cooling means including an elongated water-receiving chamber narrower than the cylinder head, the bottom wall of said elongated water-receiving chamber being exposed directly to the heat of the combustion chamber so as to expand in response to the action of the heat,

said bottom wall being provided with a valve port, said cylinder head having relatively uncooled heat-retaining expanding marginal portions exposed to heat transmitted from said combustion chamber so as to expand freely in response to the action of the heat, and said heat-retaining expanding marginal portions being located at opposite sides of said elongated water-receiving chamber to permit expansion of said bottom wall,

10. An internal combustion engine provided wit-h a,cylinder forming'a combustion chamber, and a cylinder head consisting of a single casting secured to and seated on one end of the cylinder, the bottom of said cylinder head being substantially as large as the diameter of its seat, said cylinder head having cooling means including an elongated water-receiving chamber narrower than the cylinder head, the bottom wall of said elongated water-receiving chamber being formed integral with said cylinder head, and said bottom wall being exposed to the heatof the combustion chamber so as to expand in response to the action of the heat, said bottom wall ofthe elongated waterreceiving chamber being provided with an air inlet port and an exhaustport, said cylinder head having relatively uncooled heat-retaining expanding marginal portions exposed to heat transmitted from said combustion chamber so as to expand freely in response to the action of the heat, and said heat-retaining expanding marginal portions being located at opposite sides of 'said elongated water-receiving chamber to permit expansion of said bottom wall.

11. An internal combustion engine provided with a cylinder, a piston in said cylinder, a hollow cylinder head having a top wall, side walls and a bottom wall seated on said cylinder, said side walls being located directly above the pistonand said bottom wall being extended from the side walls to overlap the cylinder, and fastening means wherebystresses are transmitted through said sidewalls toforce the cylinder head onto .the cylinder.

In testimony that I claim the foregoing I hereunto afiix my signature.

REINHARD HILDEP-RAND.

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