US2139977A - Cylinder head for internal combustion engines - Google Patents

Description

A. SCHWARZ Dec. 13, 1938.

CYLINDER HEAD FOR INTERNAL COMBUSTION ENGINES Filed July 22, 1956 2 Sheet-Sheet 1 ATTORN EY Dec. 13, 1938. A. SCHWARZ 2,

CYLINDER HEAD FOR INTERNAL COMBUSTION ENGINES Filed July 22, 1936 2 SIneets-$heet 2 INVENTOR A? red \Schu/arz BY M ATTORNEY Patented Dec. 13, 1938 UNITED; STATES PATENT OFFICE CYLINDER HEAD FOR INTERNAL CODIBUS- 1 TION ENGINES Alfred Schwarz Montclair, N. J. I

. Application July'22,11936, Serial No. 92,047 r 3 Claims.

It is the object of the present invention toconstruct a cylinder head to conform with the ther mal requirements of the engine, particularly for high compression ratios, and combinetherewith structural stability.

Heat transfer and structural design are inseparable in an internal combustion engine, particularly so in high speed engines where the time element is limited for acertain necessary amount of radiation. The total radiation area is also limited for a given sized motor, as is the cubical content of the cylinder headfor a given compression ratio. All of the factorsmust be coordinated with the type of metal used for the construction of the cylinder head, because of the widely varying heat transfer abilities of different metals. i r I It is the object of the present invention to de-' sign. a cylinder head, transferring the proper amount of heat into the cooling medium during the various parts of the cycle, and yet maintaining the structural stability necessary to with-- stand the explosion pressure,

In co-pending application No. 680,365 filed July' 14, 1933, I have described a method of heat balancing cylinder heads, to correct a limitation of compression ratios which I-have determined experimentally. In which experiments I have found that compression ratios are limited by the hottest and coolest portions of the cylinder'head.

It has been found that maximum compression, which as is well known will give maximum power and economy, can onlybe obtained if the'cylinder head is substantially of uniform temperature. Such temperature islimit'ed-to below the auto-ignition temperatures of theparticular fuel used.

It had been determined previously that different sections of standard cylinder headsv difiered more than one hundred-degrees, even during extended continuous operation, and that auto-ignition took place in' hotter sections, while the cooler sections caused a secondarydetonation, due to a delay in burning up to a period where abroadly developed flame-front set off the remaining charge too fast. Uniform temperatures established in accordance with my previous application, permitted increased compression ratio, and as a result, increased power and economy were obtained. It became a diflicult matter to obtain maximum results with a metal of high heat con. ductivity, because the most desirable minimum cross sections caused structural weakness;

The present invention contemplates to use sections of the cylinder head which require greater cross sections for heat balancing purposes, also for structural purposes, and where such is not permissible, reinforcements "are used, and are. so designed as to maintain the desired radiation capacity or heat storage, as the case may be. Y 6 As is generally known, aluminum is a metal of high heat conductivity and oftenused for .cylinder heads. For the purpose of an example, I will assume that the-head is to be made from aluminum, in which case some of the sections re- 10 quired for proper heat balance and radiation capacity are not sufiiciently strong to withstand the explosion pressure, which in gasoline engines is approximately 500 lb; per sq.-inoh, .and the average area of a cylinder head may be taken as 15. 15 sq. inches, so that thetotal explosion pressure ex-I erted against the cylinder head will is somewhere around 6000lbs.

' Referring now to the drawings there follows below a description of thefigures thereof: 0 Fig. 1 is a fragmentary sectional view ofa cast iron plate for use as a cylinder'head. v

, Fig.2 is a view similar to that ofe-Fig. 1, but

showing an aluminum plate. I

Fig. 3 is a sectional view through a portion of 25 a cylinder'head. 7 v

Fig. '4 is a sectional view of a cylinder head taken on line A-A of Fig. '5. i

Fig; 5 is abottom plan view of the cylinder, head of Fig. 4. w i

'FigQG is a plan view of thecylinder head viewed from the combustion-chamber side, with the cylinder location'indicated by a dotted line.

Fig. '7 is a plan View showing a 'cylinder'head for use on a four cylinder motor;

Most metals, particularly aluminum, fatigue with age, and become weaker under increased temperatures, so that it is-hotuncommon for aluminum cylinder heads to break, althoughtheoretically they may be designed to withstand 40 the pressure. Since it is desirable to use alum'inum as a wall for the'combustion chamber, the present invention contemplates to use a' fairly heavy steel to formthe water 'jacketand to reinforce the aluminum combustion chamber plate in such sections'where' increasedheatstorage is desirable, and to reinforce the aluminum plate in such places where increased sectionsare not permissible, by connections to the water jacket coverplate so designed to maintain the proper radiation, as far as the combustion iscoricern'ei-and to obtain the increased necessary strength by making said cover plate of sufllcient strength and suitable design to carry the extraload. We therefore have the. heat balanced combustion of heat transfer from gas to metal, and metal to;

water, also taking into consideration the conductivity factor'of the metal. The cast iron plate Fig. No. 1, having a gas at a temperature of 1500". F. on one side, and on that side, the surface temperature will be 310 F. The mean temperature will be 265 F., and the water tem, perature istaken as 160 F., which'is standard in gas engine testing practice. Under such conditions the heat transferfrom the gas to the water will be 77,000 B. t. u. per hour per sq. it. while the heat storage is 1320 B t. .u. at an intake temperature of 100. It I v Fig. No. 2 shows analuminum plate of the same thickness, and under the sameidentical condition the heat throughput is 80,900 B. t. u. per hour per sq. ft. -.The mean temperature is 240 F. The inner surface temperature is 250 F.', and the surface exposed to the water is 230 F.

The heatstorage per sq. ft; is 785 B. t. u.

Comparing the two conditions we have in cast iron, a flow of heat of 310 F. to 220 F. through which is adifierential of 90 F., while in the aluminum plate we have for the samethickness, only a differential of 20 R, which indicates that the flow in the direction of AA in iron is much slower than in aluminum. In other words all the, sections of an -aluminum cylinder head will bemore uniforma 'I'heheatretention capacity of aluminum is much smaller than iron, namely, only 785 B. t. u. per sq. ft. thick, while it is 1320 B. t.'u. for castiron. Ashas been seen before, the heat throughput through aluminum is much greater, and this'latter fact would indicate a lower thermal efliciency for the aluminum head. However, looking at Fig. No. 3, which represents a cross section of the charge of an L headmotor, we find that space A has a much greater capacity than space B. It standsto reason therefore that. the'wall section over A is heated much more than the section over B. Since every combustible only ignites when its heat of ignition is reached, section A will burn faster than section B, which causes a secondary explosion in section B, which assumes the proportion of detonation.

-'-I place over section B a greatermetal thickness, thereby increasing the heat storage in the metal, giving some heat back to the new charge duringcompression. The shock wall C having been foundby measurements always to be the hottest, .made-of' a particularly thin section. The exhaust valve region is always hotter than the intake valve regiomand I therefore decrease the section over the exhaust valve, and increase same over the intake valve. All of this can be readily determined by taking readings with constantan iron thermal couplesembedded into the cylinder head wall. Suchreadings will only have to be taken once for a specific engine to determine the best cylinder head design.

Actual brake H. P. tests have shown beyond any question that a very material increase in H. P. is obtained with the above described cylinat No. 3 the thickness is A,.

der head design. The drawings show as follows: Fig. No. 4 shows a cross section through the cylinder head AA. Fig. No. 5 shows a plan view of one cylinder and valve chest from the side of the water jacket. Fig. No. 6 shows a plan view of the cylinder head from the combustion chamber side, with the cylinder location indicated by a dotted line. The dimensions in Fig. No. 4 will give the required wall thickness over various sections for an aluminum casting. At No. l the wall thickness is 1 at No. 2 the thickness is In Fig. No. 5 it will be noted that the {a thickness is carried on from No. 4 to No. 5 and is connected to the stud- I bolt bosses 6, 6, and 6. Fig. No. 4 shows reinsection against the heavy steel plate No. 8. No. 9 is another reinforcement post also braced against the steel plate No. 8. These reinforcement posts are so calculated in sections, that the increased heat at No. 10 is'dissipated by increased area at No. 11. ply to a specificmotor only."

In the plan view, the reinforcement posts 1, 9, and. I2 are shown. It may be noted that the maximum span between reinforcements is thereby reducedto carry the explosion pressure, without however disturbing the heat balance of the cylinder head. Spark plug boss No, 13 also acts as a reinforcement. It must be remembered that the stud bolts exerting each about 1500 lbs. pressure, and in the particular cylinder head covering 4 cylinders illustrated in Fig. No. 7 there are stud bolts which are more than ample to hold down theentire cylinder head and lend strength to the reinforced sections, each stud bolt being connected by ribs No. 14 to the combustionchamber. e It isof course understood that various metals may be used for the combustion chamber plate,

providing the proper heat balance which is dif-,

ferent for different engines is taken into consideration. The method of calculating, hereinbefore given, can be usedby those versed in the art to design such cylinder heads. The cover plateNo. 8 forming the water jacket may be either made from a flat sheet, or may itself be reinforced with ribs, without departing from .the invention.

I claim: l

1. A cylinder head for internal combustion engine cylinder blocks, said head having a wall constructed to provide any number of combustion chamber. wallportions to overlie the cylinders and their respective intake and exhaust valve ports in said block, each combustion chamber wall portion of said head being divided into areas of differential heat transfer capacity, the areas of greater heat transfer capacity being arranged to overlie the hottest portions of the combustion chamber and being of less'tensile strength than Above dimensions obviously ap-' wall portion of said head being divided into areas overlying the intake andexhaust port regions which are of different tensile strength and heat transfer capacity, and heat conducting means connected .to 'and reinforcing the area of lesser tensile strength and greater heat transfer capacity above the exhaust valve port of the block, whereby substantially unifornr icombustion wall strength and temperature during the power stroke of the engine is maintained.

3. A head for an internal combustion engine cylinder block, said head having a combustion chamber forming wall overlying the cylinder and intake and exhaust valve ports for said cylinder in said block, said wall being divided into areas of differential heat transfer capacity, the area of

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