EP2089173A1

EP2089173A1 - Cylinder crankcase for a motor vehicle

Info

Publication number: EP2089173A1
Application number: EP07819294A
Authority: EP
Inventors: Herbert MÖDING; Stephan Beer; Manfred Laudenklos
Original assignee: KS Aluminium Technologie GmbH
Current assignee: KS Huayu Alutech GmbH
Priority date: 2006-11-10
Filing date: 2007-10-25
Publication date: 2009-08-19
Also published as: WO2008055594A1; DE102006053018A1; US20090277415A1; JP5216016B2; JP2010509068A; DE102006053018B4

Abstract

The invention relates to a quasi-monolithic cylinder crankcase, cast in a permanent metal mould, for an internal combustion engine, having an infiltration body (1) which is made so as to penetrate the cylinder crankcase and is formed by an inductively welded, open-cell metal foam.

Description

DESCRIPTION

Cylinder crankcase for a motor vehicle

The invention relates to a quasi-monolithic cylinder crankcase, cast in a metallic permanent mold, for an internal combustion engine with an infiltration body penetrated into the cylinder crankcase. In addition, the invention relates to an infiltration body and a method for producing such infiltration body for use in and for producing a cylinder crankcase for an internal combustion engine.

The internal combustion engines used in today's motor vehicles are for the most part made of light metal alloys. In most cases, the cylinder crankcases of these internal combustion engines made of aluminum or their alloys, with magnesium alloys are used, which bring just like aluminum alloys the advantage of low specific gravity and thus a low weight with it. In order to meet the increased and ever-increasing demands on, for example, the compression pressures, over-eutectic aluminum-silicon alloys are used in the field of aluminum alloys which, depending on the alloy, almost correspond to those of ferrous materials in their moduli of elasticity and strength. A disadvantage of these high-strength aluminum alloys is that on the one hand set high strengths, which have a positive effect on the demands placed on the cylinder crankcase, but on the other hand are consuming due to their high strength in the processing.

In order to be able to utilize the advantage of high strengths in high-strength aluminum alloys and also to be able to easily machine the cylinder crankcase, EP 0 449 356 B1 describes a cylinder crankcase which is made only locally alloyed, so that on the one hand the necessary tribological properties are obtained highly stressed area of the cylinder surface is provided and on the other hand, the cylinder crankcase is easy to work. Described is a molded in a metallic permanent, bushing single cylinder or multi-cylinder block of an aluminum alloy embedded in the aluminum matrix silicon grains, wherein in the region of the cylinder bore a cylinder bore forming, penetrated with hypoeutectic aluminum alloy hollow cylindrical shaped fiber body of ceramic fibers is embedded with silicon grains inserted therein. Here, the separately prepared fiber molded body is placed on a quill of the mold and filled the aluminum alloy melt into the mold and solidified under pressure. Preferably, the aluminum alloy melt is solidified under a pressure of at least 30 bar, but in particular 200 to 1000 bar. The method described here is also known as squeeze casting method. During pressurization after filling of the aluminum alloy melt in the mold, the aluminum alloy melt is infiltrated into the fibrous body, so that depending on the preheating of the fiber molding and alloy composition, a composite material or a locally alloyed, quasi monolithic cylinder block can be produced.

The use of porous, infiltrierbarer moldings for the production of engine blocks is also described in DE 196 17 457 A1. For the technical production of the blocks according to the invention, the prefabricated cores are inserted into the molds representing the external dimensions, and the resulting cavities are filled with the liquid metal. Due to the temperature of the melt while the outer regions of the porous cores are melted, so that between the cores and the massive block structure creates an intimate and mechanically strong connection. The degree of melting is hereby influenced by the fact that the temperature of the melt is set higher or lower or that the melting points of the materials used are placed on a different level. An indication of a pressurized pouring can not be found in the publication. Various methods are known for the preparation of the porous shaped articles used herein. Thus, on the one hand, the thermal sintering of metallic particles is described, wherein the particles are filled into a mold and heated to the melting point, whereby they fuse firmly together at their points of contact. This will be a mechanically stable Composite created with a large number of smaller interconnected cavities. Described is also a production of the sintered metal moldings, wherein the metallic particles are filled into a divisible ceramic mold and the mold is immersed in an electric coil, and the particles are heated inductively at high frequency. In addition, the use of so-called open-pore metal foams to use the production of flow paths in engines is described.

The production of porous laminar material composites is also disclosed in DE 197 22 088 A1. In this case, a powder layer or a powder molded body is briefly exposed to an alternating magnetic field in the frequency range from about 10 kHz to 120 MHz in order to generate an induction current of such energy density in the powder layer or the powder molded body that the points of contact of the powder particles are melted together at their points of contact. The condition is only that the powder is electrically conductive, so that an electric current can be induced. The process runs at melting temperature, so that the powder particles fuse at their points of contact. The type of welding creates a solid, porous composite material, which has a good dimensional stability.

Based on the prior art, the object of the invention is to provide a cylinder crankcase and a method for producing a cylinder crankcase, which is constructed quasi monolithic and locally different strength values. In addition, the object of the invention is to provide a method for producing a cylinder crankcase, which is independent of the casting process.

The solution of the object according to the invention in relation to the production of a cylinder housing is provided by the fact that the infiltration body is formed in a cylinder crankcase from an inductively welded, open-pore shaped body. The solution according to the invention provides a cylinder crankcase which has a quasi-monolithic structure but locally has different strengths in the highly stressed regions. In this case, by the choice of materials for the production of the infiltration body, by the size of the metal particles and thus the size of the cavities between the metal particles in the body and the temperature of the preheating of the infiltration before the pouring into the cylinder crankcase defined and targeted specifiable strengths in locally highly stressed areas of the cylinder crankcase adjustable and thus the required tribological properties are achieved, as well as the necessary sliding properties are adjustable in the bearing block area ..

The use of an inductively welded infiltration body is also advantageous because the inductively welded molded body has a relatively high strength in itself, so that the cylinder crankcase according to the invention can be represented as a pressure or squeeze cast cylinder crankcase. This advantage has a positive effect on the structural design of the cylinder crankcase on the one hand as well as the costs in the production of the cylinder crankcase. In particular, the infiltration bodies are easy to handle, since they are dimensionally stable and themselves have a high strength as infiltration body. There are thus provided by the invention cylinder crankcase whose static and dynamic strength properties and / or wear resistance are targeted and locally adjustable.

The metal particles for forming the infiltration body, which can also be designated as a shaped body or green compact, are formed on the basis of metal particles based on iron and / or non-iron. Preferably, but not exclusively, the infiltration body is formed from the metals iron and / or nickel and / or chromium and / or manganese and / or their alloys. The condition here is that the metal powder used, which represents the metal particles to form the green compact, is electrically conductive, since the green compact is produced by means of an induction current having an energy density such that the points of contact of the metal particles are meltably connectable to one another.

The metal particles in this case have an average size of 0.1 mm to 1, 5 mm, so that depending on the size or diameter of the metal particles used, a degree of porosity of the infiltration body is adjustable. Here, the infiltration body is produced as a reinforcing element of metal particles by inductive welding of the metal particles, wherein the metal particles are brought into a pressurized bed or under vibration in shape.

The degree of porosity of the infiltration body is between 20% and 70%. The degree of porosity to be set depends on the infiltration conditions, the is called the geometry of the infiltration body and the pressure buildup specifications of the casting process. It is possible according to the invention to use organic or inorganic spacers for porosity fractions of more than 50% in the preparation of the infiltration bodies. The placeholders used here are resins and / or plastics and / or cellulose and / or gelatine and / or salts. It has been shown that at high levels of porosity no preheating of the infiltration body is required. Should the be achieved compared with very high moduli of elasticity in the locally reinforced portions of the cylinder crankcase, the result of this requirement, a relatively low pore volume of 20% to 50%, so that the infiltration body to a temperature of 300 ⁰ C to 800 ° C before loading in the mold must be preheated. By preheating the infiltration body on the one hand, the infiltration of the light metal melt is facilitated and on the other hand is defined by the preheating of the infiltration the formation of intermetallic compounds between the Umgussmaterial and the infiltration body forming metal particles influenced. Thus, it is easily understood that an infiltration body preheated to, for example, 500 ^° C., produces more intermetallic compounds than a slightly preheated, low-pore volume infiltration body, since the energy stored in the infiltration body is ready for alloy formation. Due to the high heat capacity of the infiltration body, which is formed from an open-pore metal foam, the heat loss during insertion into the mold is low, so that the infiltration conditions over the known from the prior art ceramic foams are significantly improved.

In the case of an infiltration of, for example, magnesium alloys, open-pore metal foams are inherent as iron-based infiltration bodies, so that no reactions take place and no reproducible bond strengths result. If, on the other hand, iron or non-ferrous metal foams are infiltrated with aluminum alloys, the particle size and the preheating temperature can be used to achieve an almost complete conversion of the metal foam into aluminides, so that a highly wear-resistant composite material is produced. These highly wear-resistant composite materials then serve, for example, as cylinder running surfaces or as bearings in the area of the crankshaft.

The material properties of the cylinder crankcase formed according to the invention are determined by means of the particle size, the choice of materials for the infiltration body. per, the setting of the porosity in the infiltration body and a possible preheating of the infiltration body defined and reproducibly adjustable. Another possibility, the formation of the intermetallic phases and thus an influence on the material properties, such as the strength, is to coat the surface of the infiltration body, thus reducing or largely blocking the conversion of metal particles with the Umgussmaterial. The surface of the infiltration body is in this case oxidizable or nitridable or provided with an inorganic coating. In addition to the above-mentioned factors influencing the formation of the intermetallic phases, it is thus possible for several types of intermetallic compounds and a core region of pure metal to be formed in the region of the local strength increase of the cylinder crankcase. For example, if the infiltration body is formed of iron particles, depending on the particle size, porosity, preheating and coating, a core region of pure iron is formed, which is formed by a first layer of FeAI, if the encapsulation material is an aluminum alloy, for example. A further iron aluminide intermetallic compound of the form Fe ₂ Al ₅ forms above this first iron aluminide layer and the third surrounding layer would form an intermetallic compound of the form FeAl ₃ . This example is of course non-limiting and constitutes only one embodiment of the formation of iron aluminides when the metal particles of iron and the encapsulant material for forming the cylinder crankcase are made of an aluminum-based alloy. By way of example, however, it is also conceivable that in such a material combination the core region consists of pure iron aluminides, the first surrounding region of iron aluminides of the form Fe ₂ Al ₅ and the second surrounding region of iron aluminides of the form FeAl ₃ . The settings of the intermetallic compounds can be influenced in a defined manner with the aforementioned adjustable parameters with regard to the desired static or dynamic increase in strength.

The inductive welding of the metal particles for the preparation of the infiltration body is a cost-effective production process. Depending on the desired porosity are mixed with the metal particles placeholders, which are dissolved or vaporized during the pouring of the liquid melt into the mold. Wildcards are, for example, organic resins and / or plastics, and / or Cellulose and / or gelatin, but also organic ingredients, such as salts. An advantage of the inductive welding is the high dimensional stability. According to the invention, the infiltration body is formed, for example, from metal particles produced under pressure, so that a green body is formed, which is then subjected to an inductive middle frequency field with such a high energy density that a welding takes place at the contact points of the metal particles. The induced mid-frequency field in this case has a frequency of 1 kHz to 400 kHz and is variable according to the material used for the metal particles and the selected particle size, wherein the welding is substantially at the contact points of the metal particles. In the inductive welding, a protective gas or Formiergasatmosphäre is conceivable, but not essential to the invention, since any existing oxide layers on the metal particles due to the high induced voltage, and the resulting skin effect, are broken at the contact points over the entire cross section of the infiltration body. Placeholders or fixation components on an organic basis are gasified during the inductive welding process. The welding process regulates itself corresponding to the particle size according to the law of induction.

An essential advantage of the inductively welded infiltration bodies is that the infiltration bodies can be used for pressurized casting processes, since the infiltration bodies withstand the pressures during die casting due to their mechanical stability of the welds. Thus, the infiltration bodies are inserted into the casting mold and encapsulated under a pressure of 10 bar to 15 bar and then brought to solidification under a pressure of up to 1000 bar.

The production of local composite materials in the cylinder crankcase by means of the infiltration body on the one hand an increase in strength as well as an increase in wear resistance is possible. In addition, the tribological properties can be specifically influenced as well as the gluten properties can be set.

Another advantage of using the infiltration bodies of inductively welded metal particles is that the infiltration bodies have a weight advantage over monolithic iron-based castings. By the complete infiltration of the Umgussmaterials in the infiltration body, a gap-free pouring is also possible. The invention will be explained in more detail with reference to an infiltration experiment of open-pored metal foam.

FIG. 1 shows a micrograph in a resolution of 40 μm in a region between encapsulation material and infiltration body,

Figure 2 shows an enlarged section according to an area Il from the

Figure 1 and

FIG. 3 shows a region III likewise shown in enlarged form as the edge region of the infiltration body from FIG. 1.

In the figure 1 is a micrograph of an infiltration body 1, which is cast in a Umgussmaterial 2, shown. The infiltration body 1 in this case has two clearly distinguishable regions II and III. The edge region IM of the infiltration body 1 is enclosed directly by the encapsulation material 2, which is a light metal alloy such as aluminum or magnesium. The encapsulation material 2 is completely penetrated into the infiltration body and has formed the two clearly distinguishable regions II and III in part by forming intermetallic phases.

The infiltration body 1 according to this embodiment is made of a shaped body formed under the brand name "Astaloy CrM" with a density of 3.5 g / cm ^3. The casting material selected was the aluminum-silicon alloy AISi 12 CuNiMg. Alloy has completely penetrated into the infiltration body 1. Figure 1 clearly shows how precisely the composite material formation is adjustable according to the invention The infiltration body 1 was preheated under atmospheric conditions to about 500 °, which led to oxide formation on the surface of the metal particles This oxidation of the edge region III of the infiltration body 1 was inhibited here by the formation of intermetallic phases 3. The oxide barriers 5, 6 in FIG. 3, which represent an enlarged view of the oxidized edge region III, can be clearly seen the aluminum alloy 8, but the formation of intermetallic compounds was prevented by the oxidic coating of the infiltration body 1 prevented. FIG. 3 thus clearly shows how, by means of preheating, the oxidic coating of the infiltration body 1 and thus of the inductively bonded metal particles 7 can be controlled in a targeted manner by the duration of the preheating. For longer preheating times under atmospheric conditions, the edge region IM is displaceable into the core of the infiltration body 1. The method of coating the infiltration body is of course also applicable to the other claimed coating methods.

If, according to an aluminide formation, that is, a formation of intermetallic compounds between the metal particles 7, 9 and the encapsulation material 8, 10 sought, so no coating is deposited on the infiltration body 1, and it forms a material structure with intermetallic compounds and homogeneous transitions between the metal particles 9 and the encapsulation material 10, as shown in FIG. FIG. 2 shows an enlarged view of the region 2 close to the center of the infiltrated infiltration body 1, which was present as an open-pored metal foam 1 prior to encapsulation.

Claims

PATENT CLAIMS

1. In a permanent metallic cast quasi-monolithic cylinder crankcase for an internal combustion engine with a penetrated into the cylinder crankcase infiltration body (1), characterized in that the infiltration body of an inductively welded, molten connected, open-pore shaped body (1) is formed, the degree of porosity of the infiltration body between 20% and 70% and the infusion material has completely penetrated into the infiltration body and has formed intermetallic phases.

2. Cylinder crankcase according to claim 1, characterized in that the shaped body (1) of metal particles (7, 9) is formed on iron and / or non-ferrous basis.

3. Cylinder crankcase according to claim 2, characterized in that the metal particles (7, 9) have an average size of 0.1 mm to 1, 5 mm.

4. Cylinder crankcase according to one of claims 1 to 3, characterized in that the surface (3) of the infiltration body (1) is coated, wherein the surface (3) is oxidized or nitrided or provided with an organic coating.

5. Cylinder crankcase according to one of claims 1 to 4, characterized in that the infiltration body (1) has a cylinder bore forming, hollow cylindrical or at least part of a bearing shell forming infiltration body (1).

6. Cylinder crankcase according to one of claims 1 to 5, characterized in that the cylinder crankcase from a light metal alloy (8, 10) is formed and the infiltration body (1) of the light metal alloy (8, 10) is completely infiltrated.

7. Cylinder crankcase according to claim 6, characterized in that the infiltration body (1) made of iron and / or nickel and / or chromium and / or manganese and / or their alloys is formed and at least a partial conversion of the materials takes place, so that a composite material and / or an intermetallic phase is formed.

8. A method for producing an infiltration body (1) for a cylinder crankcase according to one of claims 1 to 7, in which an electrically conductive metal particles (7, 9) existing moldings (1) is subjected to an induction current, wherein the metal particles (7, 9) are melt-bonded at their points of contact, characterized in that the shaped body (1) is formed from metal particles (7, 9) with an average size of 0.1 mm to 1, 5 mm and under vibration or by means of a pressurized bed.

9. A method for producing an infiltration body according to claim 8, characterized in that the shaped body (1) from a mixture of metal particles (7, 9) and placeholders is formed, being used as a placeholder organic and / or inorganic constituents.

10. A process for producing an infiltration body according to claim 9, characterized in that are used as placeholders resins and / or plastics and / or cellulose and / or gelatin and / or salts.

11. A method for producing an infiltration body according to any one of claims 9 and 10, characterized in that the placeholders are gasified during the inductive welding, so that a porous molded body is formed with a porosity of 20% to 70%.

12. A method for producing an infiltration body according to one of claims 8 to 11, characterized in that the shaped body (1) is acted upon by an inductive medium frequency field having a wavelength of 1 kHz to 400 kHz.

13. infiltration body, produced according to one of claims 8 to 12, which consists of a made of electrically conductive metal particles (7, 9) powder and in which the metal particles (7, 9) are connected by means of an induction current molten, characterized in that the infiltration body (1) is formed from a powder consisting of metal particles (7, 9) and / or organic and / or inorganic placeholders, wherein the degree of porosity of the infiltration body (1) can be adjusted by means of the placeholder.

14. infiltration body according to claim 13, characterized in that the

Infiltration body (1) is an open-pored metal foam.

15. infiltration body according to claim 13 and 14, characterized in that the infiltration body (1) has a degree of porosity between 20 and 70%.

16. infiltration body according to one of claims 13 to 15, characterized in that the surface (3) of the infiltration body (1) coated, in particular oxidized or nitrided or provided with an organic coating.

17. A method for producing a cylinder crankcase according to one of claims 1 to 7, with a penetrated infiltration body (1) according to any one of claims 14 to 17, wherein the infiltration body (1) is inserted into a casting tool and then the light metal alloy (8, 10 ) is introduced into the casting tool, characterized that the light metal alloy (8, 10) is solidified under pressure.

18. A method for producing a cylinder crankcase according to claim 17, characterized in that the infiltration body (1) is heated to a temperature of 300 ⁰ C to 800 ⁰ C prior to insertion.

19. A method for producing a cylinder crankcase according to any one of claims 17 and 18, characterized in that the light metal alloy (8, 10) is inflated under a pressure of 10 to 20 bar and solidified up to 1000 bar.