US1376621A - Cylinder-head for internal-combustion engines - Google Patents

Description

R. HILDEBRAND. CYLINDER HEAD FOR INTERNAL COMBUSTION E NGINES.

APPLICATION FILED DEC. 4, 1919.

1,376,621 v Patented May 3, 1921.

2 SHEETS-SHEET I.

R. HILDEBRAND. CYLINDER HEAD EOR INTERNAL COMBUSTION ENGINES. APPLICATION FILED 050.4,1919.

1,376,621 Patented May 3,1921.

2 SHEETS-SHEET 2.

PATENT OFFICEL REINHARD HILDEBRAND, OF WEBSTER GROVES, MISSOURI.

CYLINDER-HEAD FOR INTERNAL-COMBUSTION ENGINES.

Application filed December 4, 1919.

To all 10 710m it may concern Be it known that I, REINHARD HILDE- BRAND, a citizen of Germany, a resident of \Vebster Groves, in the county of St. Louis and State of Missouri. have invented. certain new and useful Improvements in CylinderHeads 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 very large internal combustion engines of the 'Diesel type, wherein the ignition is effected by compressing air to about 500 lbs. pressure per-square inch, thereby producing a tcmperature'of about 1000 F. Thetemperatures 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 high 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 resulting 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. As a consequence, very large engines of the Diesel type, although highly economical so far as fuel is concerned, have not come into general use.

The cylinder heads of small engines form the top walls 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 at the walls of the combustion chamber. and owing to the increase in volume of the fuel without a corresponding increase in cooling area, the walls of the large combustion chambers are subjected to comparatively high temperatures. Furthermore, the large combustion Specification of Letters Patent.

Patented May 3, 1921.

Serial No. 342,372.

chamber is relatively high and very intense heat is generated at the center of the combustion chamber, as well as at the center of the cylinder head forming the top Wall thereof.

Owing to the extremely high temperatures at the central portions of large cylinder heads, and the lack of opportunity for proper cooling, the cylinder heads of large Diesel engines eventually crack near the center. Heat variations cause expansion and contraction of the cylinder head, which is a complex casting containing valves and subjected to high pressures, and great difficulty has therefore been experienced in designing large cylinder heads capable of withstanding even a brief period of service. The difficulties of this problem are fully appreciated by engineers familiar with Diesel engines, and the failure to produce very large engines 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 directly to the high pressures and intense heat resulting from combustion in the cylinder. This highly heated central portion is usually surrounded by a watercooled-marginal portion seated upon the top of the cylinder. Obviously, the watercooled margin tends to prevent expansion of the central portion, but the fireheated central portion must expand, and as a result the large cylinder heads eventually crack near the center, as will be hereafter pointed out. My object is to eliminate stresses which have heretofore resulted in fractures in large cylinder heads.

Figure I is a horizontal section on the line I-I Fig. II, showing a cylinder head Fig. IV is a diagrammatical view showing the heat-exposed face of the cylinder head.

Fig. V is a diagrammatical vertical section, showin a slightly different head applied to a cy inder.

1 designates the cylinder of an internal combustion engine, and2 designates a piston adapted to reciprocatein 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 top wall 4, all integrally connected together. Ports 5 are formed in the side walls 3 for the admission and discharge of cooling fluid, preferably water, which passes through the hollow c linder head as suggested by arrows in Fig. I The bottom of the cylinder head is 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. Y

The Diesel engine head shown in Figs; I to IV 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 between 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.

The bottom wall E of the cylinder head has central portions exposed directly to the heat of the combustion chamber and marginal portions seated upon the top of the cylinder. A cavity, or recess, R formed in the.

heat-exposed portion of the cylinder head, is provided with a top wall 10 and relatively narrow side walls 11 whereby said top wall is integrally connected to the bottom wall E.

- The inlet and exhaust ports are preferably formed in the wall 10 of the recess R, said recess forming part of the combustion chamber.

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 generally termed a heat crack, for the stresses due to heat greatly exceed those due to pressure. \Vhile the engine is running, both of these stresses vary constantly, fluctuating in wide limits. After each igrition 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,

stresses are bound to occur.

therefore, are continually elongating and contracting, and if the fibers thus affected through the cylinder head. It is obvious that g 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 In a 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 portions, and if the cylinder head bottom is in the form of a flat plate, its marginswill very effectively oppose expansion of the central portions. The heatexposed central portions of a perfectly flat plate cannot freely expand if they are sur rounded by an integral non-expanding mar ginal 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 or noirexpanding marginal portion.

Since t 1e ordinary cylinder heads crack in the direction A-B (Fig. IV) and not in the direction C-D, it is evident that the stresses in the direction CD are greater than in the direction A-B, for a rupture due to tensile or compression stresses is always approximately at a right angle to the stress. In the ordinary head, with a comparatively non-expanding margin, it appears that ex- I pansion 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.

Attention is now directed to the diagrammatical views (Figs. IV and V) which shew that the recess R is elongated in the direc= tive to the marginal tion is permitted by physical displacement of the metal forming the ports, and by the cooling action of the incoming and outgoing fluids tending to cause contraction of the metal forming the walls of the ports. However, we are faced with the roblem of preventing destructive stresses in the direction CD. The central portions of the bottom wall E are exposed directly to the heat resulting from combustion, and since these central portions are more intensely heated than the marginal portions, I permit differential expansion which could not occur in the ordinary cylinder head having a flat bottom wall.

The new cylinder head, instead of having a flat and rigid bottom wall, is comparatively flexible, the wall element 10 at the top of recess'R being capable of expanding relaportions of the head. This comparative flexibility is obtained by the action at the side wall elements 11 whereby the elongated heat exposed wall element 10 is integrally connected to the cylinder head. Since wall elements 11 lie at an angle to the elements with which they are integrally connected, said elements 11 are comparatively free to yield without fracture, when the heat exposed wall 10 expands relative to the outer portions of the cylinder head. For these reasons, the elements 11 may be termed yieldable connections. They are integrally connected to other portions of the head, and

they provide sufficient flexibility to permit the desired differential expansion without fracture.

The central portions of the combustion chamber are hotter than the margins thereof, and the central portions of the heat-exposed face of the cylinder head are likewise hotter'than the portions remote from the center. exposed to the heat at the center line of the combustion chamber, will expand and contract relative to the cooler outer portions, and the yieldable elements 11 will permit such expansion and contraction, thereby eliminating destructive stresses which have heretofore caused the typical Diesel head cracks.

When compared with a flat plate, the heat exposed wall E has the advantage of yieldingness which permits differential expansion of the elements exposed to different temperatures. and this recessed wall is also stronger than a plain flat wall.

The wall E may be cooled in any suitable manner, but its top face is preferably exposed directly to the cooling medium, while the bottom face is exposed directly to the heat generated in the combustion chamber. The recess B may be of any suitable shape, and the inlet and exhaust ports may be formed in any suitable parts of the engine. However, I prefer to follow the general pra- So the wall element 10, directly.

.wall, for a connection of this kind will permit comparatively free expansion and contraction of the central portions which are subjected to relatively high temperatures.

The invention, however, lies in certain combinations of elements which will be particularly pointed out. in the claims, it being understood that the invention comprehends modifications and equivalents of the structure herein shown.

The combustion chamber formed by the recess Bis elongated, and a'question may arise as to whether the combustion in an elongated chamber will be as complete or perfect as the combustion in a circular chamber. Complete combustion in a Diesel engine depends primarily upon whether the fuel is sprayed into the combustion chamber,

so as to thoroughly penetrate the entire body of air therein. I therefore believe it is desirable to use a piston having an approximately convex top face onto which the fuel is sprayed as shown in Fig. III. This fuelreceiving face is inclined downwardly from the center of the piston, and the fuel striking the inclined face will bedefiected and distributed in the elongated chamber .R, as suggested by Fig III. Furthermore, the substantially convex piston top is comparatively stron and it reduces the heightat the center 0 the combustion chamber. Inasmuch as the center of the cylinder head is usually overheated, there is some advantage gained by reducing the volume of burning kf)uel at the center of the combustion cham- Fig. V illustrates a modification wherein an inlet port 9 for the injection of fuel is formed in one side of the cylinder head, instead of in the top wall 10.

I claim:

1. An internal combustion engine provided with a cylinder head having marginal portions, an elongated expanding central portion exposed to the heat resulting from combustion in the engine, said heat-exposed elongated central portion being offset relative to said marginal portions, and a yieldable connection integrally connecting said central and marginal portions to permit differential expansion thereof.

2. An internal combustion engine provided with a cylinder head having marginal portions, an elongated expanding central portion exposed to the heat resulting from combustion in the engine, said elongated expanding central portion being offset relative to said marginal portions to form the top wall of an elongated recess in the heat-exposed face of said head, and a yieldable connection integrally connecting said central and marginal portions to permit differential expansion thereof, said yieldable connection forming the side walls of said recess.

3. An internal combustion engine provided with a cylinder head having marginal portions, an elongated expanding central portion exposed to the heat resulting from combustion in the engine, said elongated expanding central portion being offset relative to said marginal portions to form the top wall of an elongated recess in the heatexposed face of said head, and a yieldable connection integrally connecting said central and marginal portions to permit differential expansion thereof, said yieldable connection forming the side walls of said recess, and the elongated top wall of said recess being provided with an inlet for the admission of combustion fluid and also with an air inlet port and an exhaust port.

4. An internal combustion engine provided with a cylinder having a seat at its upper end, a hollow cylinder head through which cooling fluid is transmitted, fastening devices whereby said cured to the cylinder, said cylinder head having marginal portions contacting with said seat, an elongated expanding central portion exposed directly to the heat resulting from combustion in the engine and also to said cooling fluid, said elongated expanding central portion being offset relative to said margina portions to form the elongated top wall of an elongated recess in the heatexposed face of said head, and a relatively narrow yieldable connection integrally connecting said central and marginal portions to permit differential expansion thereof, said yieldable connection forming the side walls of said recess, and the elongated heat-exposed top wall of said recess being provided with an inlet for the admission ofvcombustihead is detachably se-' ble fluid and also with an air inlet portand an exhaust port.

5. An internal combustion engine provided with a cylinder head having marginal portions, an elongated expanding central portion exposed tothe heat resulting from combustion in the engine, said elongated expanding central portion being offset relative to said marginal portions to form the top wall of an elongated recess in the heat-exposed face of said head, and a yieldable con nection integrally connecting said central and marginal portions to permit differential expansion thereof, said yieldable connection forming the side walls of said recess, said recess being elongated transversely of the cylinder to provide an elongated combustion chamber in said cylinder head, a piston facing said elongated top wall, and a fuel in jector whereby fuel is injected away from said top wall and onto said piston, the fuelreceiving faceof said piston being inclined downwardly from its center to provide for the distribution of fuel in the elongated combustion chamber formed by said recess.

6. An internal combustion engine provided with a cylinder head having marginal portions, an expanding central portion exposed to the heat resulting from combustion in the engine, said elongated expanding central portion being offset relative to said marginal portions to form the top wall of a recess in the heat-exposed face of said head, and a yieldable connection integrally connecting said central and marginal portions to permit differential expansion thereof, said yieldable connection forming the side walls of said recess, said recess providing a combustion chamber in said cylinder head, a piston facing said top wall, and a fuel injector whereby fuel is injected into said recess and onto said piston the fuel receiving face of said piston being inclined downwardly from its center to provide for the distribution of fuel in the combustion chamber formed by said recess.

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

REINHARD HILDEBRAND.

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