US2448983A - Engine cylinder - Google Patents

Description

` suitable shaping devices. such asrollers ordies.

Patented sept 1, 1941i lnimma crnmnsn Halex Johnson, Jackson llelghtal. Y., asslgnor to Fairchild Engine and Airplane Corporation, Farmingdale, N. Y., a corporation o! Maryland Application z, 1944, snm Na. 533,685 Aa calm. (cuna-2')Y 'rms invention relates to mbmararucles and has particular reference to one-piece domed engine cylinders, but the invention is not limited to 'that Yuse. Engine cylinders, particularly cylinders of air-cooled aeronautical engines, are usually composed of two separate parts.Y viz., the barrel and the head, which are screwed and shrunk or otherwise permanently secured together, both barrel and head being provided with eitherintegral or attached heat-radiating ns.

. By reason of this construction.' the size of the cylinder head is disproportionately great, `so that the air-cooling space between adjacent cylpreferably while the material is in the cold state,

yalthough heat may be externally applied if de-` sired. In so shaping the free end of the tube, the material achieves a temperature suitable vfor working, owing to ,the friction of relative movement between the tube and the shaping die or tool', as the vdie or tool and the tube are r0- tated at high speed relatively to each other around an axiscoincident with that ofthe tube.

By properly shaping the die or tool and the cooperatingV mandrel positioned within the tube,

' the materiaij may be formed into virtually any desired shape and thickness, including thickinder heads on inlineair-cooled engines is small.

requiring. complicated; and vextensive flnning Vto obtain adequate heat dissipation. If the barrel and the head could be made in one piece with a steel liner taking all the stresses. the cylinder head wall thickness would be materially reduced. However, the nature of the material commonly" used for the wearing surfaces of the cylinder, particularly the barrel. ,precludes formation of the cylinder head as a part ofthe barrel because then thermaterial which 'is satisfactory for the barrel must Vbe made-,substantially heavier in the head portion in orderrto have adequate strength to sustain the combustion pressure! If, however, lthe head portion of a one-piece v cylinder could be made to have different physical characteristics so as to be stronger than the cylinder barrel wall for the intended purpose. the desirable aforementioned advantages would be realized. In accordance with the present invention, a

one-piece cylinder is provided which consists of cast material z for the nwearing surfaces of the cned portions for greater strength, valve seats, and the like, as described. The nished onepiece cylinderl formed in the manner described is' then'A preferably heat-treated in the usual way accordedto the barrel portion of the cylinder. and the one-piece cylinder has adequate strength for use in a high speed aeronautical engine, while retainingthe desirable properties of a casting in the barrel or wearing portion.

It Awill be seen that this invention provides a one-piece cylinder which, after being fitted with the usual cooling fins formed, cast, shrunk, or otherwise applied thereto, has all of the desir able characteristics of the usual two-piece cylinder,A but with reduced dimensions in the head area permitting improved heat ilow and desirable increased heat radiating flnning with consequent enhanced cooling emciency at the head portion,while providing desired physical propbarrel Vportion and material with different physical characteristics inthe head or dome porerties in the direction of piston travel. For a more complete understanding of the invention, reference may be had to the accom- Danying drawings, in which:

Figure 1illustrates one form of apparatus for making the one-piece cylinder of this invention; Figs. 2 and 3 illustrate elevation and plan 40.- views", respectively, of an alternative apparatus teria] which is satisfactory forthe barrel portion of theiengine cylinder.Y such as. for example.

for the cylinder'.

of the .cast tube into a closed dome by means of' Y for making the tion: and

Fig. 4 illustrates an enlarged axial section of va. iinished cylinder of this invention, with the usual, cooling fins and with the Rockwell hardness index of various sections thereof indicated thereon- Referring to Fig. 1 of the drawings, a straight thin-walled tube I0 provided with the mounting flange H Vis cast of'steel, preferably chromemolybdenum steel of S; A.`E. specication No.

one-piece cylinder of this inven- 44140 (.8-1.l Cr, .l5-25h10), or similar metal,

which has good strength and wearing characteristics for use as thin-walled cylinder barrel stock, butwhich may be materially thickened when used as cylinder head-stock. to increase its eo so to obtain a dense casting and to isolate 'methods istics of the material should be altered to en- -able the shaping deslredand also lto provide` material having the necessary strength required for the cylinder head, without vmaterially increasing its thickness.

The combined forming of the cylinder and conversion oi' the metal at the free end of the tube I0, shown by the doted lines in Fig. i, is eilected by a spinning operation, preferably by means oi a concave non-rotatable die I2 having an inwardly tapering inner face I3 merging in-to the con- `tour desired for the cylinder head. The curvature of the recess I4 in the die I2 is such as to obtain the desired shape and thickness of the head portions and may be adequate to provide material for machining the valve seats, if desired.

The cast tube I is'mounted in a chuck I5 by means of suitable clamps I8 engaging the mounting flange II so as to rotate at high speed about under pressure is supplied by tube 22 for advancing the die I2 toward and into engagement with the tube III, the rate of advance of the die I2 being controlled by a suitable valve in pipe 22, not shown.

In making the lcylinder of this invention with the apparatus shown in Fig. 1, the tube I0 is rotated at high speed and simultaneously the die I2 is advanced to engage its free end. Owing to the taper I3 ofthe concavity in the die I2, a reducing pressure is exerted on the tube end so as to develop substantial heat in the cast metal by friction, and to simultaneously gradually compress the free end of the -hot tube so as to reduce its diameter. As the die I2 slowly advances, the metal which surface I3 progressively engages is likewise heated by the friction and the metal is worked and substantially flows to conform to the contour of the diev I2, until the free end shown in dotted lines in Fig. 1, is reduced to the dome shape 23, which is preferably thicker at the center 26 and thins progressively as it merges into the wall portion 2E.

During this hot working, the cast metal is, in eilect. altered into a wrought metal, the change including a transition zone T being indicated by the shading in Fig. 4. The continuation of. the frictional heat as the end of the tube is compressed into the tip of the head 26'is sufiieient to effect a sort of welding action, so that the tip edges are closed to form continuous metal across the dome 23 at all points.

Preferably, the interior oi the tube Ill adjacent its free end is supported by a mandrel 25 having its tip or head shaped to the contour desii-ed for the interior surface of thenished cylinder head. As shown in Fig. l, the contour of the head of the mandrel 25 is such as to provide s greater thickness of material at the center or tip 2E of the 'cylinder head, that is to say, the radius of curvature or the mandrel 25 at its tip or head .4 is greater than the radius of curvature o! recess I4 of the die I2 at the center of its recess. a1- though it may have the same curvature as the die recess Il, and the die I2 will not be advanced as far toward the mandrel head, whereby increased thickness of dome 23 is obtained. By variously shaping the mandrel 25 and the recess I4 in die I2, virtually any desired thickness or conguration for the head 23 may be obtained, as will be readily understood.

Instead of employing the preformed die I2 for working the cast steel into the desired head shape.

as described in connection with Fig. 1, a roller 21, shown in Figs. 2 and 3, rotating in a suitable yoke 28 pivoted on the bed 20' of the forming machine about a vertical axis 28 substantially coincident with the center of curvature of the dome, may be employed. In this case the end of the cylinder tube is preferably preheated and the roller 21 gradually swung from the dotted line position shown in Fig. 2 about its pivot 29 to the full line position shown as the material is worked and shaped in the manner described. friction contributing the maior part of the heat required for the shaping operation. An interior mandrel similar to mandrel in Fig. 1 may be used, depending upon requirements.

The finished cylinder retains the physical characteristics of the cast steel, such as S. A. E. No.

for mounting on the engine crankcase at flange I I 4 4140 mentioned, along the barrel portion B, where it is required for the piston engaging surface. However, the head portion H has altered physical characteristics, owing to the working produced by the forming operation of this invention, and those physical characteristics are similar to those obtained in wrought metal in the sense that the material has greater physical strength than the original cast metal, so as to withstand the pressures to which it is subjected in use on an engine.

The transition zone .T between the barrel porl- Ition B and the head portion H shows a gradual change from crystalline structure of the cast portion B to the crystalline structure of the wrought portion H, the zone T. having a relatively coarse crystalline structure which is augmented when overheating results during working at that point. Consequently, close control of temperature is required in zone T to prevent overheating or burn-f ing and to maintain a relatively ne crystalline structure at that point comparable with that in zones B and H.

Heat treatment of the entire finished cylinder according to the heat treatment usually accorded the barrel portion B for S. A. E. 4140 steel, viz., heating to and holding at about 1650 F. for

about one-half hour, cooling in air, heating and'.

holding at about 1550 F. for about twenty-live minutes, quenching in oil, and nally tempering by heating to and holding at about 1100" F. for about two hours, results in a substantially uniform grain structure in areas B, T and H; in the nature of areilned sorbitic structure.

Before heat treatment, in an experimental operation, the hardness of the finished one-piece cylinder ranged from 24 to 25 Rockwell C hardness for the straight or barrel portion B of the cylinder. approximately 34 Rockwell "C hardness. in the zone T, and 30 to 32 Rockwell C hardness in the dome H, as indicated by the indices shown on the axial section of Fig. 4.

The cylinder thus formed may be completed by providing it with'cooling fins in the usual way. as indicated by way of illustration by the dotted lines in Fig. 4. This finning may be applied by casting cooling iin and valve port material on the entire ,cylinder and milling finsv and ports therein, by casting a muti.' with suitable fins. or by shrinking a jacket of heat transfer material thereon, with or without completed iins previously formed, or the like, such completing operations accordingly forming no part of the present invention. Suillce it to say that the one-piece cylinder of this invention is susceptible tothe usual machining and other nished operations accorded cylinder barrels and heads.

acteristics changingvprogressively from substantially cast steel adjacent said barrel portion to substantially wrought steel adjacent to said head portion.

The entire cylinder wall may be made as thin as is desirable, and hence serve as a strength liner for an enveloping structure, which may include the air cooling fins, cooling liquid Jacket and the like, or it may be lmade as thick as required throughout, or various portions thereof may be thickened in the manner described so as to serve as the sole strength member for the cylinder, to which Vvmay be applied cooling fins or cooling liquid jackets imparting little or no strength to the cylinder as a whole, or the tube may be so formed as to provide part of the strength needed in use with the enveloping structure completing the strength requirements, and the like. Various methods may be employed. for adapting the one-piece cylinder of this invention to the requirements of the engine to which it is to be applied, this invention not being limited to the particular use to which the cylinder is to the die recess may be heated to various degrees to supply additional heat as at the center of the die recess to aid in closing the center 'or tip oi the cylinder dome, and the like. Various other changes in the invention may be made within the scope of the appended claims.

I claim:

1. As an article of manufacture, a one-piece internal combustion engine cylinder part formed of metal, having a substantially uniform chemical composition throughout and comprising a straight-sided tubular barrel portion having substantially the physical characteristics of cast steel, and a dome-shaped head portion having substantially the physical characteristics of wrought steel.

2. As an article of manufacture. a one-piece internal combustion engine cylinder part formed oi metal, having a substantially uniform chemical composition throughout and comprising a straight-sided tubular barrel portion having substantially the physical characteristics oi. cast steel. a dome-shaped head portion having substantially the physical characteristics of wrought steel, and an intermediate portion between saidv barrel and head portions having physical char- 3. As an article of manufacture, a one-piece internal combustion engine cylinder part, coniprising integral barrel and head'portions, both composed of metal of substantially uniform initial chemical composition and physical characteristics throughout, the physical characteristics of the metal constituting the head portion having been altered as compared to the physical characteristics of the metal constituting the barrel portion, and the chemical composition of said entire part remaining unaltered. y

' 4. As an article of manufactureLa one-piece internal combustion engine cylinder part, comprising a substantially straight-sided tubular barrelportion formed of metal having physical characteristics suitng it for cylinder barrel service, and a dome-shiped cylinder headv portion merging into said barrel portion and `formed of metal having different physical characteristics than said barrel portion metal and suitng it for cylinder head service.

5; As an article of manufacture, a one-piece internal combustion engine cylinder part. com prising a substantially straight-sided tubular barrel portion 'having physical characteristics suiting it for cylinder barrel service, and a domeshaped cylinder head portion merging into said barrel portion and having different physical characteristics than said barrel portion and `suiting it for cylinder head service, said cylinder head portion having greater wall thickness than said barrel portion.

6. As an article 'of manufacture, a one-piece internal combustion engine cylinder part, comprising a substantially straight-sided tubular bar- Hsmx JonNsoN.y anraanNcas crrnn The following references are oi' record the ille of this patent:

UNITED s'rs'rns PATENTS Number Name Date 368,837 Kennedy Aug. 2'3, 1887 1,157,323 Nicholson Oct. 19, 1915 1,157,335 Steinbecker Oct. 19, 1915 1,267,253 Murray May 21, 1918 1,274,812 Sullivan Aug. 6, 1918 1.283.800 Kastner Nov. 5.1918 1.328.273 VFuchs Jan. 20, 1920 1.762.370 Warner June 10. 1930 2,851,020

Dewey June is, 1944

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