|Publication number||US3781022 A|
|Publication date||Dec 25, 1973|
|Filing date||Nov 30, 1970|
|Priority date||Dec 1, 1969|
|Publication number||US 3781022 A, US 3781022A, US-A-3781022, US3781022 A, US3781022A|
|Inventors||J Kumabe, K Shimuzu|
|Original Assignee||Rikagaku Kenkyusho, Teikoku Piston Ring Co Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (8), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Kumabe et al.
[451 Dec. 25, 1973 PISTON RING AND CYLINDER LINER HAVING MINUTE OIL-RETAINING INDENTATION Inventors: Junichiro Kumabe, Tokyo; Koichi Shimuzu, Okaya, both of Japan Assignees: Rikagaku Kenkyusho, Wako-shi,
Saitama-ken; Teikoku Piston Ring Co., Ltd., Tokyo, both of J apan Filed: Nov. 30, 1970 Appl. No.: 93,568
Foreign Application Priority Data Dec. 1, 1969 Japan 44/95716 Dec. 1, 1969 Japan 44/95717 US. Cl 277/213, 277/214, 92/169 Int. Cl. Fl6j 9/12, F16j 11/04 Field of Search 123/193; 92/169,
 References Cited FOREIGN PATENTS OR APPLICATIONS 1,133,041 11/1956 France 92/169 Primary Examiner-Samuel B. Rothberg Att0rney-William D. Hall, Elliott 1. Pollock, Fred C. Philpitt, George Vande Sande, Charles F. Steininger and Robert R. Priddy 5 7 1 ABSTRACT 5 Claims, 9 Drawing Figures PAIENTEU use 25 I975 sum 1 BF 2 INVENTOR U .M m H S K E B A M U K d BY WM Z/WL KM ATTORNEY PATENIED DEC 2 5 I975 3381.022 SHEET 2 OF 2 R m m V m d. KUMA BE 4' K. SHIMIZU /7 M Ma VMJM ATTORNEY PISTON RING AND CYLINDER LINER HAVING MINUTE OIL-RETAINING INDENTATION SUMMARY OF THE INVENTION Introduction of high performance engines in recent years has brought a serious problem of the effects of seizure and irregular abrasion due to scuffing of their cylinders and piston rings upon the running of the engines. The current tendency is that more and more such defects are being detected as a result of increases in the mean effective pressure, explosion pressure, and engine speed for higher outputs.
Since scuffing is in many cases attributed to the coarseness of the outer surface of piston rings and the inner surface of cylinders, extensive efforts have been made to solve the problem through improvements of the casting and machining of such parts. As yet, however, no fundamental solution has been found out. For this reason, a high-speed run immediately after the assembling of an engine is prohibited, and some negative makeshift must be resorted to, as for example many hours of running-in before full-speed operation.
Hard chrome plated piston rings and cylinder liners, which are typical of the parts in use, are formed with oil-retaining pores. However, the plating by nature makes it difficult to control the irregularity of such pores, and again these parts require lengthy running-in periods.
On the other hand, improvements in composition are being achieved for non-plated piston rings and cylinder liners. Nevertheless, the formation of a workdeteriorated layer cannot be prevented. The layer in the form of irregularly distributed regions has very poor resistance to the sliding abrasion at the time of precision finishing, boring, or honing. Their microscopic surface contours consist of irregular indentations which form abnormal extreme-pressure contacting parts. They present difficulties for localized retention of oil film and increase the chances of unusual high-pressure contact, thus making for a scuffing tendency. These surface characteristics represent the limitations of the prior art machining techniques, and this is the reason why many hours of the inefficient, cumbersome and costly running-in operation has to be resorted to customarily under light load.
This invention relates to a piston ring and a cylinder liner which overcome all of the foregoing difficulties of the conventional parts. More specifically, the invention relates to a piston ring and a cylinder liner which are formed with numerous oil-retaining indentations in a geometrically uniform and regular grid pattern on the entire outer peripheral surface or the entire inner surface, respectively, to avoid the forming of abnormal extreme-pressure contacting parts and render it possible to obtain ideal lubricative-contact surface conditions after a short running-in period.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a piston ring having minute oil-retaining indentations of a geometric grid pattern on the surface in accordance with the present invention;
FIG. 2 is a front view of the piston ring as seen from the direction'indicated by an arrow mark I] in FIG. 1;
FIG. 3 is a side view of a cylinder liner having minute oil-retaining indentations of a geometric grid pattern on the surface in accordance with the invention;
FIG. 4 is a sectional view taken along the line lV-IV of FIG. 3;
FIG. 5 is an enlarged view showing the surface conditions ofa part of piston ring tha characterize this invention;
FIG. 6 is an axial sectional view showing a piston ring of the invention in contact with a conventional cylinder liner;
FIG. 7 is a sectional view of the same parts but as seen from the direction atright angles to their axial direction;
FIG. 8 is a side view of an arrangement for machining the outer peripheral surface of a piston ring according to the invention; and
FIG. 9 is a side view of an arrangement for machining the inner surface of a cylinder liner according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be better understood by the following detailed description taken in conjunction with the accompanying drawings showing embodiments thereof.
FIG. 1 is a side view of a piston ring 1 according to this invention, and FIG. 2 is a front view of the same ring, both showing the outward appearance of the ring covered with continuous rows of numerous fine oilretaining indentations arranged in a geometric grid pattern. The geometric grid pattern is formed of indentations distributed with regular pitches in the circumferential direction of the piston ring 1. FIGS. 3 and 4 show, respectively, one side of a cylinder liner 2 according to the invention and a central section along the longitudinal direction of the same liner, the latter illustrating the surface conditions of the cylinder liner formed with indentations by the feed pitch S of the boring tool and with indentations distributed with a regular pitch I in the circumferential direction by regular forced vibration which is produced by the machine tool dynamic rigidity of the tool edge and the cutting conditions. Conventional piston rings and cylinder liners to not have such circumferentially and regularly distributed indentations.
FIG. 5 shows a microscopic structure of the surface of the piston ring I of FIG. 2 or the cylinder liner 2 of FIG. 4. In the figure, axial lines a, b, c, d, e, f, and so forth on the piston ring 1 or the cylinder liner 2 represent ridges which define valleys or notches in between, or between the lines a-b, b-c, c-d and so forth. Of circumferential lines A, B, C, D, E, F, G, H and so forth, the alternate lines A, C, E, G and so forth represent ridges whereas the other alternate lines B, D, F, H and so forth represent the bottoms of valleys or notches. It follows that the piston ring 1 or the cylinder liner 2, as the case may be, contacts the smooth surface ofa conventional matching element with the prominences or distinct points indicated by solid dots in FIG. 5;
The indentations have fine pitches, for example 1 15 ,u. and S 20 IL. All of the surface indentations other than the prominent contact points serve as minute oilretaining units, and the oil trapped therein contributes to smooth lubrication of the contacting parts. Thus, the surface has a geometric pattern with a grid or mesh of the minute oil-retaining notches.
FIG. 6 is an axial section ofa cylinder liner in an engine, and FIG. 7 is a section at right angles to the axis of FIG. 6, either figure showing a piston ring 1 of the invention in contact with a conventional cylinder liner 2'.
As shown, the outer peripheral surface of the piston ring 1 having oil-retaining notches 3 slides in contact with the inner surface of the cylinder liner 2. The surface prominences of such a piston ring or such a cylinder liner combined with a conventional piston ring, having the uniform height and regular shape, can complete the initial abrasion after a very short period of running-in and, with an even contacting surface, it can proceed to the stage of normal, constant abrasion. After the running-in, the lubricating effect by the countless oil-retaining notches regularly distributed over the contacting surface can improve the wear resistance of the mating parts.
H68. 8 and 9 illustrate examples of apparatus for machining such a piston ring or cylinder liner. A workpiece 4 of piston ring or cylinder liner which is rotatably chucked to the spindle of a lathe is machined with a cutting tool 5. The tool 5 is designed for resonance with a single wave mode of bending vibration, and is fixed with vibration joints 6 to a tool rest 7, so that the tool tip can be subjected to regular forced vibrations. To avoid any restriction of the vibration mode, the tool rest 7 is secured to a tool holder 9 which, in turn, is fixedly mounted on a carriage 8 of the lathe. With such an arrangement, the dynamic characteristic conditions and machining conditions to be used are carefully considered and chosen, and uniform and sustained vibration of the tool tip is ensured. Then, the peripheral or end cutting or boring is carried out.
EXAMPLE 1 A workpiece for piston ring, measuring 50 mm in outside diameter, 44 mm in inside diameter and 8 mm in thickness, was machined under the conditions of spindle speed 220 r.p.m., overall tool length 150 mm, node-to-node distance 88 mm, rake angle 0, depth of cut 0.05 mm, and feed 0.06 mm/rev, and regular indentations of geometric grid pattern having pitches of I p. and S 60 u were formed.
The time required for running-in of the engine using this piston ring could be reduced to one-third to onefifth of the running-in periods with conventional piston rings.
EXAMPLE 2 A workpiece 4 for cylinder liner, having inside diameter of 400 mm, outside diameter of 440 mm and length of 800 mm, was machined under the conditions of spindle speed 25 rpm, tool holder 9 length 500 mm, holder diameter mm, tool shank thickness 17 mm, tool shank length mm, node-to-node distance 88 mm, rake angle 0, depth of cut 0.05 mm and feed 0.8 mm. Regular indentations of geometric grid pattern having pitches of I 16 p. and S 800 p. resulted. The time required for the running-in of the engine using this cylinder liner was as short as about one-third to onefifth of the time required with conventional liners.
As will be clear from FIG. I, the present invention is as advantageously applicable to the end faces and inner surface of a piston ring 1 as on its outer peripheral surface.
What we claim is:
1. A metallic part having a cylindrical surface thereof which is adapted to be in sliding, pressured, lubricated contact with a mating metallic element to provide a high-pressure seal therebetween,
said cylindrical surface of said part having a myriad of minute indentations which are disposed in a regular, geometric grid pattern, v
said indentations being defined by closely spaced continuous helical grooves each formed in said surface with a repetitive depth variation to form thereby closely spaced successive ridges and valleys in each groove and with the spacing between successive of said ridges being less than the groove width.
2. The invention as defined in claim 1 wherein said metallic part is a piston ring and said grid pattern is formed on the outer cylindrical surface of said ring.
3. The invention as defined in claim 2 wherein the width of each helical groove is about 60 microns and the circumferential spacing between successive of said ridges in any groove being about 20 microns.
4. The invention as defined in claim 1 wherein said metallic part is a cylinder liner and said grid pattern is formed on the inner cylindrical surface of said cylinder liner.
5. The invention as defined in claim 4 wherein the width of each helical groove is about 800 microns and the circumferential spacing between successive of said ridges in any groove being about 16 microns.
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|U.S. Classification||277/461, 92/169.1, 277/924|
|International Classification||F16J10/04, F16J9/00|
|Cooperative Classification||F16J10/04, F16J9/00, Y10S277/924|
|European Classification||F16J9/00, F16J10/04|