US1742396A - Internal-combustion engine piston - Google Patents

Description

Jan. 7, 1930. A. T. ,Kgslgef 1,742,396

INTERNAL GOHBUSTO ENGINE PISTO-F mea gan. 22. 1927 l i f Www AI KasIeY I INVENTQR WITNESS ATTORNEY Patented Jan. 7, 1930 UNITED STATES PATENT omer. l

ALEXANDER T. KASLEY, OF` IVIOOIRIES,l PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANFACTURIN G COMPANY, A CORPORATION OIF PENNSYLVANIA INTERNALCOMBUSTION ENGINE lPIS'JON Application led January 22, 1927. -Seral No. 162,796.

My invention relates to pistons for internal combustion engines and it has for an object to provide apparatus'of this character which shall be highly conductive ot' heat, thereby 5 rendering the provision of special cooling means for the pistons unnecessary.

More particularly, my invention has for an object to provide a piston having the head and ring belt portions thereof made ot' metal 10 having a high coeiiicientof thermal conductivity, for example, copper', in order that heat received by the head portion of the piston may be readily conducted to regions of lower temperature, thereby preventing the accumulation of heat in the piston and the attainment of such high temperature therein as would call for the provision of special cooling means.

It is common practice in the internal combustion engine art, particularly with engines of the large Otto cycle type and of the Diesel type, to Water-cool the piston. With Diesel engines, Where higher temperatures and pressures obtain, the question of piston temperature is a serious one, and it has heretofore usually been met by the expedient of Water cooling. The problem of piston cooling, Where the engine is of the opposed-piston, two-cycle, Diesel type is more pronounced for the reason that the piston Which covers and uncovers the exhaust openings serves as a deector for products of combustion, and is exposed twice as often as it is in a four-cycle engine.

It has also been determined in the internal combustion engine art, where no special means is provided for piston cooling, that the major portion of the heat passes fromthe piston head and ring belt to the 'cylinder Wall, the rings bearing closely against sides of the ring grooves and against the interior of the cylinder facilitating the transmission of heat. While the major portion of the heat is transmitted in this Way, a minor portion is left-for dissipation by the skirt portion of the piston,

^ and the greater part of this heat passes from the piston to the cylinder Wall.

As a result of my endeavors to provide a piston Without special cooling means for a Diesel engine, more particularly an engine of the opposed-piston type, I have discovered In my Work leading up to copper pistonswith Diesel engines, cast iron and aluminum pistons were used without success. The aluminum pistons deteriorated rapidly due to heat effects. The cast iron pistons showed excessive accumulationsof'carbon and the piston rings lost their springiness, this occurring after only 30 hours of use of the cast iron pistons. The injury to the piston rings was due to excessive temperatures; and the accumulations of carbon on the crank side of the piston head were due to this same cause, it being apparent that lubricating oil would .be subjected to very hi h temperatures With conse uent cracking t ereof and deposition of car on.

Copper pistons were then made and in-v stalled in the same cylinder lin which the aluminum and cast iron pistons had been used and the engine put in operation. After approximately 300 hours of service, the engine Was dismantled with the result that it was found that the piston 'rings were uninjured and there was practically no carbon.- The reason for this satisfactory operation with copper pistons is that copper has such high conductivity for heat that the pistons never reach such a high temperature as to result in serious cracking of oil or injury to the piston ring or to themselves, such pistons readily conducting heat to cooler regions. e A further object of my invention is/to provide a two-cycle internal combustion engine, more particularly of the Diesel type, with copper pistons, pistons of this character serving not only to simply the problem of cool ing, asset forth above, but also serving as good cross-head bearingelements and to redensity duce the maximum crank shaft stresses, the latter effect being due to the relatively greater of copper as compared to other materials commonly used for engine pistons.

Apparatus made in accordance with my invention is illustrated in the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a longitudinal sectional view of.

an engine cylinder employing my improved pistons; c

Figs. 2 and 3 are longitudinal sectional views of one of the pistons shown in Fig. 1;

Fig. 4 is a transverse sectional view taken along the line IV-IV of Fig. 3;

Fig. 5 is an end elevational view of one of the pistons viewed from the skirt end; and,

Fig. 6 is a longitudinal sectional view showing a modified form of piston.

Referring to the drawings4 more in detail, I show a cooled or water-j acketed engine cylinder 10 having opposed pistons 11 and 12 therein, the pistons being made of material, for example, copper, have a relatively high coefficient of conductivity for heat. vrl`he pistons are connected by rods 13 and 14 to crank shafts 15 and 16, respectively, the crank shafts being interconnected in any suitable way to secure proper timing of operation of the pistons.

The cylinder 10 is provided with scavenge air inlet' openings 17 adjacent to one end thereof, these openings being covered and uncovered by the piston 11; and, adjacent to the other end of the cylinder, there are exhaust openings 18 covered and uncovered by the piston 12. Th'e pistons are so timed, as is well-known in the art, that the piston 12 uncovers the exhaust openings 18 before the scavenge air inlet openings 17 are uncovered, thereby permitting of the ready straight flow of scavenging air to expel products of combustion from the cylinder. With this arrangement, the exhaust openings 18 are preferably closed before the air inlet openings 17,

thereby assuring of the cylinder beingiilled with super-charged air before compression begins.

After the cylinder has been supplied with air and after compression has proceeded to the desiredextent, fuel is injected by a suitable device 20, such fuel being preferably ignited due to the heat of compression of the air. With a two-cycle Diesel engine, such as al'- ready described, it will be seen that the piston 12 is subjected to severe heat effects for, not only is it heated during the compression stroke and during the power portion of the outward stroke on every revolution but it also acts as a deflector of hot gases during the exhaust period. Where the engine is of the high-speed type, the problem of heat effects becomes evenniore serious. These two things contribute to make the use of an uncooled piston more difficult; however, I have found that copper pistons, without any special cooling means, may be used with entire satisfaction. .For example, I have used copper pistons of about live inches in diameter for an engine having a speed around 1000 R.' I. M.

Ilie pistons 11 and 12 are similar in structure so that a description of one in detail will suiiice. As shown in Figs. 2 to 5, inclusive, each pistonv is of the trunk type, made of copper and includes a head portion 22 having a ring belt portion 23 and a skirt portion 24. Wrist pin bearings or supports 25 are provided in the piston, such bearings or supports preferably having inwardly extending and opposed hubs, as indicated at 20. Ribs 27 are joined to the forward sides of the hubs 26, to the interior of the piston and to the head portion, these webs or ribs not only serving as mechanical strengthening means but also as heat conductive means. The part of the skirt to the rear of the wrist pin bearings 25 is formed to provide strengthening webs or ribs 28.

The ring belt portion 23A is provided with a suitable number of piston ring grooves 29 for piston rings 30.

To the rear of the Wrist pin bearing 25, I showran oil groove 31 having passages 32 extending within the hollow piston, the groove 31 being formed with -a scraping edge 33 for the purpose of removing excess lubricant from the cylinder wall upon a power stroke of the piston. The opposite wall of the groove 31 is rounded ofi' as indicated at 34 to facilitate distribution and spreading of oil on the cylinder Wall upon a compression stroke.

As copper is ordinarily too soft, particularly when cast, to afford a good bearing surface, the wrist pin bearings or supports 25 are hardened by rolling or mechanically working .in order to produce hardening, such bearings then being machined to receive wrist pins.

In Fig. 6, I show a modified form of piston in whichthe piston head and ring belt portions are made of copper, as indicated at 35, the remainder of the piston being made of any suitable material such as cast iron and indicate at 36.

The high conductivity for heat ossessed by pistons made of copper, as wel as the large amount of surface thereof contiguous to water-cooled cylinder walls, assures that heat may be readily conducted from the pis- 'y Westinghouse that it is highly satisfactory in this respect. `As the density of copper is comparatively high, great inertia effects develop; and, while such effects would be undesirable with fourcycle operation, yet they are advantageous with tivo-cycle operation in that they reduce the maximum crank shaft stresses.

While copper pistons may be used to advantage in the internal combustion engine art wherever the question of overheating of the pistons becomes acute, I have found such pistons to be highly satisfactory in connection with Diesel engines, particularly engines of the two-cycle, high-speed type. Not only has this discovery of a material making possible the use of an uncooled piston in a two-cycle opposed piston type of engine resulted in greater simplicity and economy in construction, but it has simplified the construction of an engine made up of a large number of cylinders such as disclosed and claimed in the application of H. T. Herr, Serial No. 102,043, filed Aqil 14, 1926, assigned to the lectric & Manufacturing Company. i

While I have specifically referred to the engine pistons as being made of copper, it will be understood by those skilled in the art that such pistons may be made of any suit'- able material having a sufficiently high coefficient of thermal conductivity as to secure such transfer of heat to the cooled,cylinder walls as will prevent the attaining of such high temperatures at the head end of the piston as would result in unsatisfactory combustion or injury to the pistons or rings.A

Upon referring to page 303 of Marks Mechanical Engineering Handbookfit will be noted that the coefficient of conductivity for aluminum is between 115 and 120, depending on the temperatures; that the conductivity of copper is around, 220, and that the conductivity of cast iron is very much lower, that is, around 27. While copper has been found to serve well for the purposes stated, it4 will be obvious that any metallic material having suitable physical and thermal characteristics may be used.

While I have shown my invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from. the spirit thereof, and I desire, therefore, that only p such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is 1. In a Diesel engine of the two-cycle type having a cooled cylinder, an uncooled iston in the cylinder having top and ring be t por- .tions made of copper. p y

2. In an internal combustion engine, the

combination with a working cylinder having' an exhaust port in the side wall thereof, of

a Working piston in said cylinder adapted to cover and uncover said exhaust port, said workin-g piston having its top and ring belt portions formed entirely of copper.

3. In an engine of the opposed-piston, twocycle type having a cylinder provided with inlet and exhaust openings in the side wall thereof, metallic working pistons disposed in the cylinder each having a specific gravity greater than cast iron and havingtheir head and ring belt portions made of copper, one of said pistons being arranged to cover and uncover the inlet port and the other of said pistons being arrangedto cover and uncover the exhaust port.

'4. In an internal combustion engine, the combination of a cylinder provided with cooling means and an uncooled working piston in the cylinder having at least its top and rin@ belt portions formed of copper in order to of heat.

In testimony whereof, I have hereunto subscribed my name this 20th day of January,

ALEXANDER T. KASLEY.

facilitate the conduction and dissipation-

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