US3021183A - Cylinder and piston structures - Google Patents

Description

Feb. 13, 1962 w. c. CHENEY ETAL 3,021,183

CYLINDER AND PISTON STRUCTURES Filed Nov. 2a. 1958 116.4; INVENTORS.

ATTORNEYS.

3,021,183 CYLINDER AND PESTGN STRUCTURES Wendell C. Cheney and Harold Morehouse, Lake City,

Minn,- and Marshall G. Whitfield, Garden City, l l.Y.g

said Cheney and said Morehouse assignors, by direct and mesne assignments, to Gould-National Batteries,

Inc., St. Paul, Minn, a corporation of Delaware Filed Nov. 28, 1958, Ser. No. 777,036 11 Claims. (Cl. 309-6) This invention relates to the problem of minimizing wear and scoring of pistons and cylinders, particularly in internal combustion engines, and has also to do with various combinations of cylinder and piston structures in which this general object is attained.

Generic aspects of the invention apply to engines having ferrous cylinders or cylinder blocks, cylinders or cylinder blocks made in part of heavy metal and in part of light metal such as aluminum, cylinders or cylinder blocks made entirely of light metal, and to engines of the so-called wet sleeve type in which a sleeve pro viding the inner surface which coacts with a piston is removably and renewably mounted in a block and is contacted on its outer surface by a cooling iluid. The invention is applicable to engines of the above types using ferrous pistons, light metal pistons, and composite pisas respects'engine cylinders tons of light metal containing heavy metal reinforce- "-1 mcnts, the pistons being used with or without rings. The generic aspects of the invention are further applicable to all types of internal combustion engines, from small structures such as are used to power pumps, lawn mowers, motor-cycles and the like, through normal fourcycle engines such as are used in automotive equipment, to heavy duty structures including two-cycle engines, super-charged diesel engines, and engines in the gasoline and diesel fields using very high compression ratios.

Structures of all of these types are well known to skilled workers in the art and do not require description. The invention will be explained in connection with a specific embodiment which is a light metal cylinder or block and a light metal, ringless piston, with incidental references to other types of structure, it being understood that the specific embodiment is exemplary only and not limiting, beyond the terms of the appended claims. The exemplary embodiment is chosen because it serves to illustrate certain specific aspects of the invention as well as the more general aspects.

Additional and more specific objects of the invention are:

The provision of a structure facilitating the use of ringless pistons in engine cylinders.

The provision of a structure facilitating the use of light metal pistons in light metal cylinders.

The provision of a structure facilitating the use of ringless pistons in light metal cylinders.

These and other objects of the invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, are accomplished by that structure and arrangement of partsof which the aforesaid exemplary embodiment will now be described. Reference is made to the accompanying drawings wherein:

FIGURE 1 is a longitudinal sectional view of an exemplary cylinder with a piston partially shown therein.

FlGURE 2 is an elevational View of a ringless piston of a type which may be used in the cylinder of FIG- URE 1.

FIGURE 3 is a diagrammatic view of an engine showing another embodiment of the invention.

FIG. 4 is a diagrammatic view showing a piston and cylinder embodying another form of the invention.

3,621,183 Patented Feb. 13, 1962 It is known that wear, abrasion, scoring and scufiing and pistons are influenced by a number of factors such as temperature and the nature of the metals which operate against each other. Most of the wear of cylinders and cylinder liners in internal combustion engines occurs in that portion of the cylinder which lies between the upperand lower limits of travel of the top compression ring of the piston, the cylinder wear being greatest where the compression ring reverses its direction of travel. Lubrication also has some effect upon wear; and it has been recognized that wear is minimized to a certain extent by a porous condition of the inside surface of the cylinder. Porous metals or finishes which, nevertheless, are hard enough to sustain abrasion, have been found desirable; and attempts have been made to accomplish the edect of porosity by an artificial roughening of the bore of the cylinder.

- Porosity, whether naturally occurring in the surface of of the metal or whether artificially produced, has not been found a complete solution for the problem. As the porosity is relatively slight, the desired amount of lubrication may not be attained; but if the interior surface of the cylinder is roughened or rendered porous to such a degree that a highly efiective amount of lubrication will be present between the piston and the cylinder, the consumption of oil by the engine is very greatly increased, with additional undesirable effects such as coking and the like.

. The present invention is based on the discovery that wear, abrasion, scuffing, and scoring may be very largely eliminated or ameliorated without increasing oil consumption by a construction and procedure which will now be described. Referring first to FIGURES l and 2, there is illustrated at 1 an exemplary cylinder for an internal combustion engine. This cylinder is illustrated as of the air-cooled type and hence characterized by projecting cooling fins 2. The metallic material of which the cylinder is made is not a limitation upon the aspect of the invention here under description, nor is the form of the cylinder or its air-cooled or fluid-cooled character. The particular cylinder is shown as havingports 3, 4, 5 and 6 which, again, are illustrative but not limiting. A piston 7 operates within the cylinder and comprises ahead portion 8 and a skirt portion 9. The piston may have any suitable construction and may be made of any suitable metallic material. It will have theusual pin holes 10 surrounded by interior bosses for the reception of the conventional wrist pins.

It has been found that adequate lubrication may be supplied to the piston without excessive oil consumption by the provision of a configuration in the inner surface of the cylinder wall and the location of this configuration in a particular way. In its simplest form, the configuration consists of agroove 11a formed in the inner cylinder wall. This groove may be and preferably is fully circular. Its dimensions may vary; but excellent results have been attained with a groove about inch in width having a depth of about the same'dimension. The depth and width of the groove may be substantially varied in accordance with the lubricant-delivering capacity desired in any particular cylinder of any particular size.

Grooves from a few thousandths of an inch in width and depth up to grooves, say, A inch or inch in width and depth, may be employed, depending somewhat on the size of the cylinder and the length of the piston stroke. But it iswithin the purview of the invention to provide a series of annular grooves in the interior surface of the cylinder, which grooves are closely spaced so that they may be located as hereinafter taught. If the grooves themselves are very small, there will desirably be a pluralprovide the required invention, the groove or grooves will be uncovered by the end of the piston ski-rt;

Where the piston has rings, these should not travel over or past the grooves. The grooves should not be uncovered by the head of the piston in any position; but in some structures good results can be obtained even though the skirt does not uncover or fully uncover the groove or grooves at the top end of the stroke.

When a groove or grooves are provided and located as herein set forth, and means are provided to deliver oil to the grooves, it will be found that the piston is kept in a well lubricated condition with the skirt of the piston covered at all times with an ample film of oil, while at the same time the consumption of oil by the engine will not be significantly increased. Thus, the structure of this invention operates unexpectedly in a way very different from porosity or roughness in the cylinder surface. The delivery of oil to the groove or grooves may be accomplished by the splashing of oil from the engine crankcase, since the groove or grooves will be exposed during each cycle. It does not constitute a departure from the invention, however, to provide special means for delivering oil to the groove or grooves, such as spray nozzles or other means involving the use of conduits, if such are desired.

The groove 110, or its equivalent as hereinafter set forth, acts to keep the skirt of the piston well lubricated. At the same time, the groove is so located that the upper part of the piston, i.e. the portion of the piston adjacent the head, does not pass the groove, but is always located on the cylinder head side of the groove, irrespective of the position of the piston. Consequently, the groove does not act to deliver oil into the firing space of the cylinder. At the same time, oil is maintained between the piston skirt and the cylinder walls, so that lubricant in relatively small but suflicient quantities is delivered to the head end of the piston or to the piston rings, if rings are used. It is believed that this action largely explains the reason why the means of this invention are effective in minimizing wear and scoring, while they do not significantly increase oil consumption.

FIGURE 2 illustrates a piston without rings. Such pistons may advantageously be provided with one or twoshallow grooves 11 and 12 near the head end, in approximately the position of the piston rings in the ordinary piston. These help to increase the lubrication at the head end of the piston without pumping oil into the firing space. Adistributor groove 13 may be provided in the skirt end of the piston if desired. Grooves on the piston do not act in the same way as thegroove 11a in the cylinder wall. Thegroove 11a greatly increases the efficiency and life of ringless pistons in internal combustion engines.

It has already been indicated that a series of grooves may be substituted for thesingle groove 11a, providing the grooves are so closely spaced that they may be located in the span of the travel of the piston as hereinabove indicated. The lubrication means of this invention is not restricted to a circular groove or series of grooves. It is well known that in most engine cylinders the wear or scoring tendency is localized in portions of the cylinder walls (and corresponding portions of the piston) lying substantially normal to the axis of the wrist pin. The groove or grooves may be confined to such portions of the cylinder walls. In FIGURE 4 there is cally an engine having a horizontal cylinder lq, withpiston 15 having rings 16. The piston is connected by usual connecting rod 17 to a crank shaft 18. If the cyclical operation of the engine is such that the illustrated relationship of parts obtains at the start of the power stroke, the wear and scoring tendency will be largely localized at the top sides of the cylinder wall and piston. In such an instance it is within the scope of this invention to confine the groove orgrooves 11a to the top side of the cylinder wall as shown. Similarly in cylinders where the thrust load comes at the bottom side the groove or grooves may be confined thereto.

7 ing provided with illustrated diagrammati- A result similar to that produced by the groove orgrooves 11a can be obtained by the use of other indentations, relatively closely spaced, of sufi'iciently great capacity to hold the required amount of lubricant, and confined lengthwise of the cylinder to such an area of the cylinder wall that, like the grooves, they will be uncovered by the piston skirt when the piston is in its top or outermost position, but will lie inwardly of the piston rings on the outer part of the piston when the piston is in its bottom or innermost position. Such indentations may be produced in various ways, but are most conveniently made by knurling. In FIGURE 3 there is shown a portion of a cylinder wall 19 hearing a series of indentations 20 formed by knurling.

Thegrooves 11a or the indentations 20 are formed by the use of a cutting tool or knurling tool employed in the process of finishing the interior of the cylinder.

An essential difference between the action of the means of this invention and a general porosity of the interior walls of the cylinder lies in the fact that if a general porosity has enough capacity to keep the skirt of a piston well lubricated, it will tend to pump oil into the firing space of the cylinder whereas the means of this invention does not. The means of this invention, however, may be used in cylinders having a degree of porosity without departing from the spirit of the invention.

As indicated, the means of this invention are of utility in all of the known types of cylinder and piston combinations. The cylinder may be air cooled and hence provided with heat-dispersing fins, or it may be water cooled and form a part of a cylinder block having an integral cooling jacket. Yet again the cylinder may be of the wet sleeve type in which the cylinder proper is a sleeve which is replaceably positioned within a cooling jacket. The pistons may be of heavy metal, e.g. cast iron, or of light metal, e.g. aluminuinor aluminum alloys, or of light metal with heavy metal reinforcements. The pistons may be used with or without rings. The means of the invention are elfective despite considerable variations in piston clearance. For example, in an engine having a cast iron cylinder and a cast iron piston, a clearance of .001 inch per inch of cylinder bore is common with a round ground ferrous piston (the clearance being somewhat less when the piston is cam ground), the piston be rings. The invention works well with such a clearance. Where light metal pistons are employed in ferrous cylinders a clearance of about .00075 inch per inch of cylinder bore is usual, most light metal pistons being cam ground. The present invention is very efiective in minimizing wear and scoring with such a clearance; and where both piston and cylinder are made from the same aluminum alloy closer clearances can be used. Where pistons without rings are employed, closer tolerances at full operating temperatures are generally sought, a clearance of about .0005 inch per inch of cylinder bore being effective for engines with cylinder bore diameters of around. 2 inches. The means of this invention not only serve to maintain full lubrication under all such clearances, but are of great importance in the use of ringless pistons because the life of such pistons is very considerably prolonged.

The invention is of especial importance not only in the field of cylinders and pistons made of metals which are matched as to coelficients of expansion, and where close tolerances are generally sought, but also in the field of cylinders made of light metals. It has not generally been found satisfactory to make cylinders of aluminum or ordinary hypoeutectic aluminum alloys since their wear resistance is not great. The means herein taught, however, will usefully prolong the life of such cylinders rendering them useful especially in small engines. In a copending application of Marshall G. Whitfield and Wendell C. Cheney, two of the present inventors, entitled Aluminum Alloy Engine Cylinder, Serial No. 743,659, filed June 23, 1958, there are described engine cylinders made of or consisting on their inner wall surfaces of a hypereutectic silicon-aluminum alloy containing substantially 17 to 25% or more silicon. Preferred structures may be made in accordance with that invention by preforming an interior sleeve or cylinder of the hypereutectic alloy and then casting about its outer surfaces at body of aluminum alloy of diiferent characteristics, permissibly but not necessarily hypoeutectoid, but having a different coefiicient of expansion such that the hypereutectic sleeve is maintained under compression. Yet again a structure may be made in which a hypereutectic sleeve is located within a block of other light metal and is water or air cooled. Hypereutectic cylinders of this character, used in connection with matched light metal pistons with or without rings otter a large field of utility for the practice of the present invention. The precipitated silicon in the hypereutectic alloy contributes to hardness and wear resistance. The interior surfaces of such cylinders usually have a slight but useful porous structure. When the principles of this invention are applied to such structures, the useful life thereof is very greatly prolonged; and this invention has permitted the efiective use of matched combinations of light metal cylinders and light metal pistons at close tolerances.

Modifications may be made in the invention without departing from the spirit of it. The invention having been described in certain exemplary embodiments what is claimed as new and desired to be secured by Letters Patent is:

1. In combination, in an internal combustion engine, a cylinder having an interior surface, a piston in sliding engagement with said interior surface and having a head and a skirt, the interior surface of said cylinder having an oil-receiving reservoir in the form of at least one indentation, said reservoir being limited in extent longitudinally of said cylinder to a position at which it will be uncovered by the skirt of said piston at one extreme of the piston travel but covered by said skirt at the other extreme, the said reservoir having a substantial extent circumferentially of said cylinder.

2. The structure claimed in claim 1 wherein said piston has rings and wherein said reservoir is located in such position that it lies at all times on the skirt side of said rings.

3. The structure claimed in claim 2 wherein the interior surface at least of said cylinder is formed of a hypereutectic silicon aluminum alloy.

4. The structure claimed in claim 1 wherein said piston is devoid of rings.

5. The structure claimed in claim 4 wherein the interior surface at least of said cylinder is formed of a hypereutectic silicon aluminum alloy.

6. The structure claimed in claim 4 wherein the interior surface at least of said cylinder is formed of a hypereutectic silicon aluminum alloy, and in which said piston is formed from a similar hypereutectic silicon aluminum alloy and has a clearance of about /z thousandths of an inch per inch of cylinder diameter in said cylinder.

7. The structure claimed in claim 1 wherein said oilreceiving reservoir comprises a series of closely spaced indentations, said series extending at least partially circumferentially of said cylinder.

8. In combination a cylinder and a piston for reciprocation therein, said cylinder having a head end and an interior surface, said piston having a head end and a skirt, said piston being connected with a crank shaft by means of a connecting rod and a wrist pin, and an oilreceiving reservoir in the form of at least one indentation in the interior surface of said cylinder so located as to be uncovered by the skirt of said piston at the extremity of the travel of said piston toward the head end of said cylinder, and so as to fall short of the head end of said piston at the opposite extremity of its travel, said reservoir being limited in extent longitudinally of said cylinder being located in a portion of the interior surface of said cylinder opposite a line normal to the wrist pin of said piston, the said reservoir having asubstantial extent circumferentially of said cylinder.

9. In combination, in an internal combustion engine, a cylinder having an interior surface, a piston in sliding engagement with said interior surface and having a head and a skirt, the said interior surface of said cylinder having an oil-receiving reservoir in the form of a groove extending circumferentially of said interior surface of said cylinder, and so positioned that it will be uncovered by the skirt of said piston at one extreme of the piston travel, but covered by said piston at the other extreme, the said piston and the interior surface of said cylinder being made of metal having substantially the same coefficient of expansion.

10. The structure claimed in claim 9 wherein said piston has a circumferential groove in its skirt travelling past the groove in the interior surface of said cylinder upon each stroke of said piston.

11. The structure claimed inclaim 10 wherein said piston and the interior surface at least of said cylinder are formed from a hypereutectic silicon aluminum alloy.

References Cited in the file of this patent UNiTED STATES PATENTS 1,193,200 Strand Aug. 1, 1916 1,295,329 Kennedy Feb. 25, 1919 1,459,819 Bonner June 26, 1923 1,871,820 Morton Aug. 6, 1932 FOREIGN PATENTS 632,173 Germany Oct. 4, 1932 1,097,144 France Feb. 9, 1955 OTHER REFERENCES Schafer: German application 1,007,560, printed May 2, 1957 (K1 46Cl) 2 pages spec, 1 sheet dwg.

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