Patent Application
20180023703
The present disclosure relates to a piston ring and more particularly to a piston ring with high conformability for gas or diesel combustion engines.
This section provides background information related to the present disclosure which is not necessarily prior art.
Piston rings are typically made from steel for many high performance engines. In general, steel is harder and it has a higher tensile and fatigue strength in comparison with ductile and grey cast iron. Steel piston rings can solve a lot of problems in highly stressed engines. They are stronger, harder, seal better and resist breakage and wear under load. They are ideal for any application that involves higher combustion temperatures, higher compression loads and tougher emission standards. The smaller cross section of a steel ring, permitted by the greater strength, also improves the ability of the ring to conform to less-than-perfect cylinder bores. Compared to ductile or cast-iron, the inherent high strength of steel creates less chance of ring breakage. Steel also provides longer service life.
The present disclosure provides improved piston ring conformability with the engine cylinder bore and provides a method of making the improved piston ring.
According to the present disclosure, a piston ring includes a generally circular open ring having a generally cylindrical outer diameter surface and an inner diameter surface having a plurality of radially outwardly extending arcuate recesses.
In addition, a method of making a piston ring is provided including extruding a rectangle cross-section steel wire to include two recesses in a side edge thereof and winding the extruded steel wire in a ring shape with the arcuate recesses being on an inner diameter surface of the wound ring.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
With reference to
The high conformability steel piston rings 10 can be formed first by warm or cold extrusion of rectangle cross-section steel wire 40 to make uniform sinusoidal, radiused or other type shape undercuts or recesses on one side of the wire as illustrated in
The winding of the formed wire 40 may be completed through either a hot or cold forming process. In hot winding, the rings 10 can be austenitized at 880 C±50 C, hot wound and oil quenched. After quenching, the rings 10 are tempered at 400 C±25 C. In the cold winding, the wire 40 is first induction-hardened at 950 C±50 C and tempered at 470 C±25 C and then wound at room temperature to the required sizes and possibly further stress relieved at 180 C±25 C.
To improve the steels durability (fatigue), if needed, the steel rings 10 may be shot-peened to produce compressive residual stress on the ring surfaces. In the shot peening process, 0.2-0.5 mm diameter ‘cut wire’ types of shots with hardness in the range of 610-670 HV are used. The shot peening intensity may be measured on a type A strip using the Almen test and the minimum and maximum values were 0.25 and 0.4 mm, respectively (curvature or deformation of the sheet). The shot peening duration may last 6-10 seconds and the coverage can be 99.9%.
To make the steel rings 10 compatible with cast iron liners (cylinder walls), at least the outer surfaces 16 of the steel rings 10, that contact the bore surfaces, may be coated with either chrome or molybdenum, PVD or DLC, or nitride. Prior to coating, the ring outer surface must be ground flat. Gas nitriding is a heat treatment process that impregnates the surface of the steel with nitrogen to case harden the steel surface. For steel rings 10, gas nitriding case hardens the entire surface of the ring 10 to a depth of about 25 μm which greatly improves its resistance to side wear as well as face wear.
Prior to coating, the steel ring outer surface should be ground flat. After extraction and rolling, as disclosed, the steel wire surfaces are usually flat. Unlike chrome, moly, PVD, or DLC coating, gas nitriding is a heat treatment process that impregnates the surface of the steel with nitrogen to case harden the steel surface.
The alloy for the steel rings may contain 0.5-0.6 wt % C, 1.2-1.6 wt % Si, −0.6-0.9 wt % Mn, 0.6-0.8 wt % Cr, 0.035 max P, 0.04 wt % max S and balance Fe.
The amount of machining that is required to finish a steel ring 10 is far less than that which is required to finish grey cast iron or ductile iron rings, particularly with the extruded steel wire. So, in general steel rings are actually less expensive to manufacture, at least in large batches. Most of the steel rings currently in production have a width of 1.2 mm, some are as small as 1.0 mm.
The high conformability of the disclosed piston rings 10 helps to improve oil consumption, blow by and to reduce piston ring tension. In addition, the high conformability provides improved performance. In addition, the manufacturing method reduces manufacturing cost as compared to other forms of feature manufacturing.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
