Cylinder crankcase for an internal combustion engine

Abstract

Cylinder crankcase (1) for an internal combustion engine, comprising at least one cylinder bore (3) formed from a material comprising chromium, molybdenum, carbon, with a 0.2 to 0.3 wt.% content of carbon in the material, and ceramic, wherein the ceramic comprises a first and a second oxide ceramic, wherein the first oxide ceramic has an 80 wt.% content of the ceramic and the second oxide ceramic has a 20 wt.% content of the ceramic, and wherein the first oxide ceramic is aluminum oxide (Al2O3) and the second oxide ceramic is zirconium oxide (ZrO2).

Description

[0001] The invention relates to a cylinder crankcase for an internal combustion engine, in particular a diesel engine, and in particular to a cylinder crankcase with a cylinder bore made of a specific material.

[0002] Despite increasingly strict emissions regulations for internal combustion engines, especially diesel engines, fuel quality remains below European standards in many markets for a variety of reasons. Sulfur levels in diesel fuel, in particular, vary greatly around the world. The maximum limit of 10 ppm (parts per million) set by the European standard (EN 590) is far exceeded, with levels as high as 2,000 ppm in Brazil and China, and well over 10,000 ppm in Jordan, for example. In addition, fuel quality can vary considerably even within a country. While better quality fuel is available in urban areas, rural areas often only offer inferior fuel, some of which does not meet national fuel standards.

[0003] This lower quality of diesel fuel or the high sulfur content means that engines are subject to greater corrosion effects, which can be particularly problematic for engines that were developed for diesel fuel with a lower sulfur content, as required by a standard, for example.

[0004] When operating with high-sulfur fuel, oil consumption may increase over time. This increased oil consumption may be caused by corrosion-induced wear of cylinder bores and piston rings. These corrosion effects can occur at specific power levels of 50 kW / dm and above. 3increase disproportionately. Therefore, one solution in countries with high-sulfur fuel for a given engine displacement is to use low-performance engines with an output of, for example, less than 50 kW / dm3, with the economic disadvantage of a lower profit contribution. Another solution is to provide the required engine power with a larger engine displacement, with corresponding weight and fuel consumption disadvantages. Depending on a manufacturer's engine program, a separate engine would have to be developed for such countries, which, however, may be uneconomical depending on the marketable volume.

[0005] It is generally known to manufacture engine cylinder crankcases from cast iron. Cast iron materials include compositions that contain, among other things, carbon, aluminum, chromium, and other metals, as shown, for example, in DE 10 2004 010 916 A1, or molybdenum, as proposed in US application US 2013 / 0 089 682 A1. Furthermore, German patent DE 10 2011 009 443 B3 discloses a wire-like spray material for producing cylinder bores based on carbon, silicon, manganese, chromium, copper, and nitrogen. German patent application DE 199 56 622 A1 also proposes an alloy for cylinder liners based on aluminum bronze and containing, for example, a chromium alloy.

[0006] The published patent application DE 103 34 701 A1 describes a thermally sprayed cylinder liner for internal combustion engines, which is made of a thermally sprayed iron-based alloy with friction and wear-reducing particles dispersed therein.

[0007] The published patent application US 2013 / 0 133 608 A1 describes a cylinder with a running surface with a coating comprising a metal matrix reinforced with ceramic particles.

[0008] The patent DE 34 01 433 C2 describes a process for coating parts of the combustion chambers in engines.

[0009] A ceramic-metal composite or a metal-ceramic composite is known from the published patent application WO 2004 / 043 875 A2.

[0010] A method for producing a cylinder block is known from the published patent application DE 40 40 975 A1.

[0011] The published patent application EP 1 710 216 A2 describes a material for thermal coating, a surface layer, and a compressor with a surface layer of the material.

[0012] Even though the prior art proposes different materials for cylinder crankcases or cylinder running surfaces or cylinder liners, it is the object of the present invention to provide a cylinder crankcase for an internal combustion engine which at least partially overcomes the above-mentioned disadvantages.

[0013] This object is achieved by the cylinder crankcase according to the invention according to claim 1.

[0014] One aspect of the present invention relates to a cylinder crankcase for an internal combustion engine, comprising at least one cylinder bore formed from a material comprising chromium, molybdenum, carbon and ceramic.

[0015] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0016] As mentioned, the exemplary embodiments relate to a cylinder crankcase for an internal combustion engine, such as a gasoline engine or, in particular, a diesel engine, comprising at least one cylinder bore formed from a material comprising chromium, molybdenum, carbon, and ceramic. Some exemplary embodiments also relate to an internal combustion engine, such as a gasoline engine or, in particular, a diesel engine, with a cylinder crankcase as described herein, or to a motor vehicle with such an internal combustion engine.

[0017] The cylinder crankcase may, for example, have one, two, three, four or more cylinders, wherein, for example, a cylinder bore is provided for each cylinder in a corresponding associated cylinder tube in the cylinder crankcase, along which the corresponding cylinder piston runs, as is generally known to the person skilled in the art.

[0018] The cylinder bore can generally be arranged directly in the respective cylinder tube or, for example, be formed in a cylinder liner arranged in the cylinder tube, or the cylinder liner itself can form the cylinder bore. Furthermore, the cylinder crankcase can also be formed partially or entirely from the workpiece, so that, for example, the inner wall of the cylinder tube, which is formed in the base body of the cylinder crankcase, forms the cylinder bore.

[0019] The cylinder liner can, for example, be cast into the cylinder crankcase or thermally joined and, for example, have a wall thickness of less than 0.5 mm, whereby the cylinder liner is partially or completely formed from the material.

[0020] The cylinder bore can completely form the inside of the cylinder tube or only sections of it (e.g. stripes, score lines, elevations, grooves, etc.).

[0021] The chromium content in the material creates a passive layer that reduces corrosive attack from the acids produced during fuel combustion in the cylinder, especially sulfuric acid. The ceramic in the material also makes it harder, thus reducing corrosive attack from the acids produced during fuel combustion in the cylinder.

[0022] Due to the high corrosion resistance, combustion engines and especially diesel engines can be realized, for example, with a specific power greater than 50 kW / dm 3 especially greater than 55, 60, 70 or even 80 kW / dm 3 . In some embodiments, the internal combustion engine, in particular a diesel engine, can achieve cylinder bore wear of less than 100 nm / h, in particular less than 80, 60, 40 nm / h, or even less than 20 nm / h in some embodiments when operated with diesel fuel having a sulfur content greater than 4000 ppm and at 95-105% of the rated speed and more than 95% of the maximum torque achievable at this speed.

[0023] In some embodiments, the ceramic comprises an oxide ceramic. An oxide ceramic can be based on the oxide of a single element, e.g., Al2O3, ZrO2, MgO, etc., or it can contain, for example, oxygen ions as well as several cations of different elements in its crystal lattice, e.g., MgAl2O4, BaTiO3, ZnFe2O4, etc., and can therefore be a so-called mixed oxide ceramic.

[0024] In some embodiments, the oxide ceramic comprises aluminum oxide (Al2O3) and / or zirconium oxide (ZrO2), which have proven to be particularly resistant to the material.

[0025] In some embodiments, the ceramic comprises a first and a second oxide ceramic, e.g., a mixture of the first and second oxide ceramic. In some embodiments, the first oxide ceramic makes up 80% by weight of the ceramic, and the second oxide ceramic makes up 20% by weight of the ceramic, based on the total weight of the ceramic, i.e., the ceramic content in the material. The first oxide ceramic may comprise aluminum oxide (Al2O3) and the second oxide ceramic may comprise zirconium oxide (ZrO2), so that in some embodiments, the ceramic consists of 80% by weight of aluminum oxide (Al2O3) and 20% by weight of zirconium oxide (ZrO2). This mixture has proven to be particularly resilient.

[0026] In some embodiments, the proportion of ceramic is 30 to 40 wt.% based on the total weight of the material, which allows a particular hardness and resistance of the material to be achieved.

[0027] In some embodiments, the proportion of chromium is 10 to 20 wt.% based on the total weight of the material, whereby a corresponding passive layer and associated acid resistance can be achieved.

[0028] In some embodiments, the material has the following composition with weight percentages that refer to the total weight of the material: - Chromium content of 10 to 20 wt.%, preferably 12 to 14 wt.%; - Molybdenum content of 0 to 7 wt.%, preferably 2 to 3 wt.%; - Carbon content (C) less than 0.5 wt.%, preferably 0.2 to 0.3 wt.%; and - Oxide ceramic content of 30 to 40 wt.%, preferably 34 to 36 wt.%, wherein the oxide ceramic content consists of an oxide ceramic mixture of 80 wt.% Al2O3 and 20 wt.% ZrO2, based on the total weight of the oxide ceramic content.

[0029] In some embodiments, the cylinder bore has a thickness between 0.1 mm and 3 mm, in particular a thickness of 0.1 mm, 0.5 mm, 1 mm or 3 mm.

[0030] In some embodiments, the cylinder bore is produced at least partially by means of a plasma coating process, in particular an atmospheric plasma coating process, which is generally known to those skilled in the art and therefore will not be explained in further detail below. The layer thickness of the cylinder bore made of the material is selected such that, after honing, it has a minimum thickness of more than 0.1 mm, preferably more than 0.5 mm. Honing is a machining fine machining process that is generally known to those skilled in the art, particularly in the production of cylinder bores, and therefore will not be explained in detail below.

[0031] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 schematically shows an embodiment of a cylinder crankcase for a diesel engine.

[0032] Fig. Figure 1 shows an embodiment of a cylinder crankcase 1 of a diesel engine, wherein the diesel engine has four cylinders. For each cylinder, a so-called cylinder tube 2 is formed in the cylinder crankcase 1. For the sake of simplicity, Fig. 1 illustrates only one cylinder tube 2 of the cylinder crankcase 1, which is formed in a base body 4 of the cylinder crankcase 1. The base body 4 is formed here, by way of example and without limiting the present invention accordingly, from a cast material, e.g., cast iron or light metal, such as aluminum, or another castable material, as is generally known to those skilled in the art.

[0033] On the inside of the cylinder tube 2, which is formed by the material of the base body 4, a cylinder bore 3 is formed, which forms the running surface for a piston (not shown), as is also basically known.

[0034] The cylinder bore 3 is basically made of a material as described above, whereby the material in this embodiment has the following composition (based on the total weight of the material): - Chromium content of 12 to 14 wt%; - Molybdenum content of 2 to 3 wt.%; - carbon content (C) of 0.2 to 0.3 wt.%; and - Oxide ceramic content of 34 to 36 wt.%, wherein the oxide ceramic content consists of an oxide ceramic mixture of 80 wt.% Al2O3 and 20 wt.% ZrO2, based on the total weight of the oxide ceramic content.

[0035] The cylinder bore 3 is formed by an atmospheric plasma coating process and with such a thickness that it has a minimum thickness of 0.5 mm after honing.

[0036] This allows the diesel engine to run on diesel fuel with a sulphur content of more than 4000 ppm at a specific power of more than 80 kW / dm 3 The cylinder bore 3 is so resistant due to the material used that when the diesel engine is operated at 95-105% of the rated speed and more than 95% of the maximum torque achievable at this speed, it has a cylinder bore wear of less than 20 nm / h (in some embodiments less than 40 nm / h), whereby in some embodiments this applies to operation of the diesel engine with a sulfur content of more than 4000 ppm and less than 5000 ppm.

[0037] In other embodiments, the diesel engine can be operated with diesel fuel having a sulfur content of more than 4000 ppm at a specific power of more than 55 kW / dm 3 or more than 65 kW / dm3. List of reference symbols 1 cylinder crankcase 2 cylinder tube 3 cylinder bore 4 basic bodies

Claims

[1] Cylinder crankcase (1) for an internal combustion engine, comprising at least one cylinder bore (3) which is formed from a material which comprises chromium, molybdenum, carbon, with a 0.2 to 0.3 wt.% proportion of carbon in the material, and ceramic, wherein the ceramic comprises a first and a second oxide ceramic, wherein the first oxide ceramic has an 80 wt.% proportion of the ceramic and the second oxide ceramic has a 20 wt.% proportion of the ceramic, and wherein the first oxide ceramic is aluminum oxide (Al2O3) and the second oxide ceramic is zirconium oxide (ZrO2). [2] Cylinder crankcase (1) according to claim 1, wherein the proportion of ceramic is 30 to 40 wt.% based on the total weight of the material. [3] Cylinder crankcase (1) according to one of the preceding claims, wherein the proportion of chromium is 10 to 20 wt.% based on the total weight of the material. [4] Cylinder crankcase (1) according to one of the preceding claims, wherein the cylinder bore (3) has a thickness between 0.1 mm and 3 mm. [5] Cylinder crankcase (1) according to one of the preceding claims, wherein the cylinder bore (3) is produced by a plasma coating process.

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