Patent Application
20190107076
This application claims priority benefit of European Patent Office Application No. EP17425096, filed Oct. 10, 2017. The entire contents of which hereby incorporated by reference herein.
A piston is a moving component that is contained by a cylinder of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, and other mechanisms. In an engine, the piston can transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall.
According to some aspects, systems and methods provide a piston and process for manufacturing a piston includes an upper part providing an upper combustion surface including a top land, a land ring and a combustion bowl. An undercrown surface is formed under the combustion bowl. A lower part including pin bosses and a piston skirt are formed under the undercrown surface. At least one of the upper part and the lower part are formed with metal injection molding.
According to some aspects, the piston is formed from multiple parts.
According to some aspects, the multiple parts are joined by sinter bonding, friction welding, brazing, flanging or pin coupling.
According to some aspects, one part is formed with MIM (Metal Injection Molding) and the other part is formed by another process.
According to some aspects, both parts are formed with MIM.
Other systems, methods, features, and advantages is or will become apparent upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description and be protected by the accompanying claims.
In association with the following detailed description, reference is made to the accompanying drawings, where like numerals in different figures can refer to the same element. The features of the drawings are not necessarily drawn to scale.
While the disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein is described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. It is further appreciated that in some embodiments, one or more elements illustrated by way of example in a drawing(s) may be eliminated and/or substituted with alternative elements within the scope of the disclosure.
In some example, the piston 2, or at least part of the piston 2, is manufactured using a metal injection molding (MIM) process, as described in more detail below. In some examples, the piston 2 is manufactured using one or more blanks. In the case of more than one blank used to manufacture the piston 2, the parts of the piston 2 can be joined together using sinter bonding and/or welding by induction or friction, and/or by including a piston pin to join the pieces and provide an articulated assembly. In some examples, the parts of the piston 2 can be manufactured using different processes, including but not limited to, MIM, casting, forging, machining of billets, etc. In some examples, the piston 2 is made from a lost wax casting. Material used to produce pistons include, but are not limited to, aluminum alloys, steel alloys, etc. In some examples, the piston 2 is manufactured from a steel alloy powder. In some examples, the MIM process can be configured to provide a cooling gallery to the piston 2. In some examples, the piston 2 does not include a cooling gallery. In some examples, the piston can endure high peak pressures, e.g., up to about 250 bar or more.
For multi-part pistons 2, in some examples the different parts are made by the same material and/or process, and in other examples the parts are made using different materials and/or processes. For example, both parts can be manufactured using the MIM process or one part is manufactured by the MIM process and another part is manufactured by forging a metal billet, etc. Table 1 contains some examples of possible combinations used to produce piston blanks. Other combinations are possible.
Combinations of parts produced with different manufacturing types can be joined in various ways, e.g., sinter bonding, friction welding, brazing, flanging or pin coupling, etc. In some examples, the MIM process can be used to produce a solid piston 2, or MIM can be used to produce one or more of parts of piston 2. Sinter bonding can be used to join together the MIM formed parts with parts formed with the same process or with parts formed with different processes to provide a solid piston 2. As described in more detail below, the piston 2 can be formed with one or more parts and/or with different geometrical features, including but not limited to: single part oil cooling galleryless, single part with cooling gallery, multi-part galleryless, multi-part with cooling gallery, cooling gallery formed both in upper and lower parts of the piston 2, lower part of the cooling gallery formed on the crown of the piston and closed at its top with a cap, cooling gallery formed in the undercrown of a piston main blank and closed with a cap to create the floor and the inlet and outlet opening port of oil cooling gallery, etc. In some examples, a multi-part piston 2 can be joined by a joint and pin, as described in more detail below. The joint can include a cylindrical or other shaped opening.
The piston can be formed joining upper part and lower part 160 through a junction surface (A-A). The junction surface (A-A) could have various shapes. Upper part and lower part 160 can be formed with different processes, including MIM. The upper part and lower part 160 can include the same or different material compositions from one another. Joining the upper part and lower part 160 can be accomplished in various ways, including sinter bonding. It is also possible to join upper part and lower part 160 of piston 2 with other techniques, including but not limited to, friction welding, brazing, induction welding, etc.
The pistons 2 of
The lower part of piston 160 include a pair of pin bosses 170 and piston skirt 180; the pin bosses 170 each having a pin bore 40 are laterally spaced from one another coaxially along a pin bore axis 190 that extends perpendicularly to the central longitudinal axis 30. Each pin boss 170 have generally a snap ring groove 200 at their outer side; snap ring groove 200 are spaced from one another along the pin bore axis 310 to fit the piston pin. The upper part 10 and a lower part 160 can be made of different materials; upper part 10 and a lower part 160 can be made of MIM, casting forging, machining processes, etc., with similar materials and mixed combinations as shown in Table 1. The upper part 10 and a lower part 160 can be joined after machining and finishing, and assembled together with a piston pin and circlips.
With regard to one or more of the pistons 2 of
A process of metal injection molding can include various steps. First, an injectable starting material can be prepared, including a binder and very fine metal powder, containing more than 90% by weight of metal powder. Like plastic, this material is processed into molded parts (green parts) with a plastic injection machine (plastic injection molding). After injection, the binder content, which made the shaping possible, is leached out of the molded parts without the parts themselves losing their shape (brown parts). Binders are mixtures of organic molecules such as paraslin wax, polyolefins and stearic acids. The composition of the binders determines the debinding mode for the green part. Debinding is possible in different ways, including but not limited to: Heating to melt, decompose, and ultimately evaporate the polymeric binder. This can be accomplished with care in order to avoid disruption of the as-molded part, and in this connection the use of binders with several ingredients which decompose or evaporate at different temperatures is advantageous. The time required for binder removal depends on the wall thickness of the part. Catalytic decomposition of feedstock using gaseous nitric acid or oxalic acid can reduced the time for binder removal and the risk of part disruption. Binder removal process is to dissolve out the binder with suitable solvents such as acetone, ethanol or hexane. Some binder constituents are even water soluble. Normally heating is used as a final step to complete the removal by evaporation
In a further step the parts can be sintered, thereby obtaining metallic properties. Sintering is the heating process in which the separate particles weld together and provide the necessary strength in the finished product. The process can be carried out in controlled atmosphere furnaces, sometimes in a vacuum, at a temperature below the melting point of the metal. Sintering can be carried out either in a gaseous atmosphere or in a vacuum. To avoid oxidation of the metal, the atmospheres used are generally reducing. Apart from protecting the metal, such atmospheres have the further advantage of reducing the oxide on the surfaces of the powder particles. This surface oxide increases with decreasing particle size. The composition of the sintering atmosphere can depend on the metal being sintered. For many metals a straightforward atmosphere containing hydrogen is all that is required, but in the case of steels which have carbon as an essential alloying element, the atmosphere must be either inert or contain a carbon compound or compounds so that it is in equilibrium with the steel, e.g., it is neither carburise nor de-carburise the steel. As the ‘brown’ part is extremely porous, a very large shrinkage occurs during sintering and the sintering temperature is closely controlled in order to retain the shape and prevent ‘slumping’. The metal powder used determines the mechanical and geometrical properties of the resulting piston. Preferred metal powder compositions include steel based powder for their strength and temperature resistance.
While particular embodiments are illustrated in and described with respect to the drawings, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the appended claims. It will therefore be appreciated that the scope of the disclosure and the appended claims is not limited to the specific embodiments illustrated in and discussed with respect to the drawings and that modifications and other embodiments are intended to be included within the scope of the disclosure and appended drawings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it is appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure and the appended claims.
Many modifications and other embodiments set forth herein will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17425096 | Oct 2017 | EP | regional |
