Patent Application
20100294229
The present invention relates to an engine component and the utilization of a new type of cast iron alloy for an engine component.
In the field of internal combustion engines, it is necessary to ensure especially good wear qualities for various parts and certain areas of the affected parts. This concerns cylinder liners and engine pistons, for example. For engine pistons in particular, the ring seal groove area requires reinforcement in order to improve the wear behavior. This particularly concerns the ring carriers which, although initially provided for as separate elements on an engine piston, can be integrally cast in, for example.
For the described areas, a high-alloy austenitic cast iron material is known from DE 100 49 598 A1 which can have different compositions.
DE 40 26 611 A1 discloses a material for a brake block that can contain zircon.
The object of the invention is, with regard to the wear behavior, to provide an improved engine component as well as to propose the use of a cast iron alloy with which an improved engine component can be manufactured.
The solution of this object is achieved also by the engine component described in claim 1.
Accordingly, the new type of engine component, which can, for example, be a cylinder liner, an engine piston or a part thereof, such as a ring carrier or a piston boss bushing for example, consists of a cast iron alloy containing zircon as an alloy constituent in a proportion of 0.1% or less. Upon analyzing an engine component manufactured in this manner, it was shown that zircon acts advantageously in the formation of carbide, forming a particularly fine and uniformly distributed special carbide as compared with those already known cast iron alloys used for engine components. Additionally, it follows that, in the engine component manufactured from an alloy of this type, graphite was primarily formed as lamellar graphite precipitation, which further improved the wear behavior. Zircon makes the structural arrangement more consistent and homogenous, leading to improved wear behavior.
Tests have shown that the specific rate of wear, which was initially measured in a wear test outside of the engine, is half of that of the previously used material. A further improvement is provided by the material according to the present invention in terms of the coefficient of thermal expansion. In conjunction with this, it should be observed that the new type of material can, for example, be used for a ring carrier that can be cast into a piston. Due to the temperature fluctuations that are typical of an operating engine, thermal stresses develop as a result of the differences between the thermal expansion coefficients of the ring carrier material on the one hand and the piston material on the other hand. There are correspondingly fewer stresses, the greater the similarity of the thermal expansion coefficients. It was ascertained for the material according to the present invention that its coefficient of thermal expansion is significantly closer to that of the piston alloy than is the case for those materials presently known. As a result of this, the stresses in the transitional area between the cast-in ring carrier and the piston material can be avoided, thus significantly reducing the tendency to form cracks and the danger of the ring carrier separating and the piston malfunctioning as a result.
In the end, an increased thermal conductivity was determined for the material according to the present invention as compared with the material used up to now. This improves the heat dissipation in an advantageous manner and by this achieves a temperature reduction in the grooves, so that the engine component manufactured according to the invention is also improved in this respect.
Preferred embodiments of the engine component according to the present invention are described in the further claims.
A zircon proportion of 0.01% as the minimum amount for the alloy constituent according to the present invention proved to be favorable.
Further, the use of nickel as an alloy constituent is preferred, in a proportion of 9.0% to 13.5%, preferably 10% to 12%.
It was found that the zircon that is added according to the present invention forms particularly in combination with boron carbides and/or chrome carbides particularly stable, fine and uniformly distributed special carbides. Therefore, it is preferable that the material of the engine component contains boron in a proportion of 0.1% or less, preferably at least 0.005%, and/or chrome in a proportion of 1.0% to 2.6%.
Especially favorable properties were further ascertained when the material contains calcium as an alloy constituent in a proportion of 0.01% or less.
An example of the cast iron alloy used that is especially preferable as a result of the trials performed is specified in detail in claim 5.
With regard to the structural arrangement, the cast iron material of the present invention exhibits in an advantageous manner an essentially austenitic structural arrangement.
As mentioned, the wear qualities can especially be thereby improved in that the material contains graphite in an advantageous manner as lamellar graphite precipitation. Furthermore, the graphite can be present as spheroidal graphite, vermicular graphite or as temper carbon. The proportion of graphite in the form of lamellar graphite precipitation thereby corresponds to at least 50% by volume, preferably at least 75% by volume, especially preferred is at least 85% by volume, and is uniformly distributed by the zircon and/or by an infusion treatment.
The advantageous properties in terms of the thermal expansion coefficient, as described above, can in particular be achieved if this lies within a range of 18.5±1×10−6 mm/mm° C. at 50° C. and 27.5±1×10−6 mm/mm° C. at 400° C.
With regard to thermal conductivity, particularly favorable properties were ascertained if this lies within a range of 29.5±1 W/mK at 50° C. to 27.5±1 W/mK at 400° C.
In addition, the present invention proposes, in view of a similar alloy previously disclosed for brake support plates, using a cast iron alloy that contains zircon as an alloy constituent in a proportion of 0.1% or less as a reinforcement material for an engine component, such as a cylinder liner or an engine piston, especially in the ring seal groove area and particularly preferable for a ring carrier. By using a cast iron alloy of this type for manufacturing cylinder liners, engine pistons or ring carriers, or for the reinforcement of areas that are particularly subject to wear and tear, such as the ring seal groove area of an engine piston, the improved products described above can be manufactured.
The material according to the present invention was manufactured with the following alloy and various trials were performed:
The remainder is Fe and unavoidable impurities.
The specific rate of wear was first measured in a test outside the engine. A rate of approximately 6×10 −12 m3/Nm was ascertained for the standard material used as comparative example. For the material according to the present invention, this was merely about 3×10−12 m3/Nm.
Furthermore, the thermal expansion coefficient of the material according to the present invention was compared with that of a standard material and that of a conventional piston alloy. NiCuCr1562 was utilized as standard material. As can be seen from
Finally, the thermal conductivity of the standard material described above was compared with that of the material according to the present invention. In conjunction with this, the outcome is that, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 07011498.8 | Jun 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/054651 | 4/17/2008 | WO | 00 | 12/14/2009 |
