Patent Application
20060008354
This application claims the priority of 103 41 415.0, filed Sep. 5, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a high-speed impeller for delivering gaseous or liquid media.
DE 101 63 951 C1 describes a rotor disk which is made of a metal and has local fiber reinforcements. In this case, the fiber reinforcements consist of metal matrix composites (MMC). These inner MMC rings are pressed into the circumference of the rotor disk by means of a radial press fit.
A rotor consisting of a composite material is described in WO 02/01311 A1, various rings of fiber-reinforced wound bodies being slipped concentrically over one another and thus forming a flat cylindrical rotor disk.
Said examples show methods of reinforcing an impeller subjected to high centrifugal loading. However, the arrangements described have the disadvantage that complex impeller structures cannot be reproduced or the fiber reinforcements are not fully integrated in the impeller.
An object of the invention includes providing a high-speed impeller which has an integrated reinforcement in a complex cross-sectional contour.
A solution of this object includes a high-speed impeller in which a reinforcing core structure is surrounded by an outer functional section, and reinforcing sleeves are pushed concentrically over one another for producing the core structure. In this case, “pushed concentrically over one another” refers to the fact that the outside diameter of an inner reinforcing sleeve equals an inside diameter of an outer reinforcing sleeve to the extent that the outer reinforcing sleeve can be pushed with little play over the inner reinforcing sleeve.
In this case, the length of the respective reinforcing sleeve varies in such a way that it can approximately reproduce a predetermined cross-sectional geometry of the core contour.
Due to such a construction of the core structure, a reinforcement of the impeller can be produced which, in deviation from the cylindrical structure of the reinforcements which are mentioned in the prior art, is designed, for example, in hyperbolic shape or in a rising exponential manner. The reinforcement is therefore not only settled in a narrow cylindrical region, but it can also be adapted along a complex cross-sectional structure of the high-speed impeller.
In many cases, the cross-sectional geometry of the high-speed impeller narrows with increasing diameter, for which reason it is expedient that, in a development of the invention, the length of the reinforcing sleeves is reduced with increasing outside diameter.
A further aspect of the invention constitutes a high-speed impeller which, claim 3. Such a high-speed impeller, like previously mentioned the high-speed impeller, has a reinforcing core structure which is surrounded by an outer functional section. However, this embodiment of the high-speed impeller is distinguished by the fact that, in order to produce the core structure, a plurality of reinforcing sleeves with in each case inner bores having the same diameter are aligned in such a way that the inner bores are aligned congruently. The expression “congruently” in this case refers to the fact that the inner bores are concentrically aligned on a common axis in such a way that a shaft can be pushed with little play through the aligned arrangement of the inner bores. However, the outside diameter of the aligned reinforcing sleeves varies in order to reproduce a predetermined cross-sectional geometry of the core structure. The functional section of the high-speed impeller is likewise cast onto the core structure.
By the arrangement of the reinforcing sleeves being modified, the high-speed impeller according to this latter embodiment achieves the same advantages as are also described by the arrangement of the high-speed impeller as in the first-described embodiment.
As described, the aligned arrangement of the reinforcing sleeves having the congruently superimposed inner bores can be pushed onto a shaft; however, it can also be pushed onto a reinforcing sleeve of the same kind. In this way, additional radial and axial strengthening is achieved.
In an advantageous development of the invention, the reinforcing sleeves are produced from a fiberreinforced material. Any form of fiber-reinforced materials by means of which a marked increase in the tensile strength and thus a marked increase in the strength of the high-speed impeller is achieved is suitable in this case. In a further development, the reinforcing sleeves comprise long-fiber-reinforced wound bodies. Such wound bodies may either already be infiltrated with a metal before the integral casting of the functional section, or they may be infiltrated with the metal of the functional section during the integral acasting of the functional section.
Furthermore, the reinforcing sleeves may consist of a metal-matrix composite material reinforced with short fibers. Furthermore, a porous ceramic infiltrated by metal may be used for the reinforcing sleeves. An increase in the tensile strength and in the modulus of elasticity is also achieved by such reinforcing sleeves.
It may also be expedient to produce the reinforcing sleeves from non-fiber-reinforced, high-strength metal materials, for example from spray-compacted metal materials or from high-strength wrought alloys. As a rule, such materials can be produced more cost-effectively than fiber-reinforced materials and are used when there is little latitude in terms of the cost of the component.
The use of the high-speed impeller according to the invention is in particular especially expedient in exhaust-gas turbochargers, in this case equally as a compressor wheel or a turbine wheel. The impellers may also be used in an expedient manner as gas turbine wheels or as water pump wheels.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
A schematic illustration of a high-speed impeller in the form of a compressor wheel 2 for an exhaust-gas turbocharger is shown in
For the sake of clarity, only a cross section of the core structure is shown in FIGS. 2 to 5. The illustration of the functional section 6 having the compressor blades 7 is dispensed with.
Shown in
The reinforcing sleeves 8 have an outside diameter 12 and an inside diameter 14. In this case, the outside diameter 12 of each reinforcing sleeve 8 is configured in such a way that it corresponds to the inside diameter 14 of the following reinforcing sleeve 8 to the extent that the two reinforcing sleeves 8 can be pushed over one another with little play (cf.
The result of such a type of construction is shown schematically in
The core structure 4 from
An aligned arrangement of various sleeves 20, with in each case a constant inner bore 22, is shown in the example in
An aligned arrangement of reinforcing sleeves 20, similar to the example from
The types of construction of the reinforcing structure 4 which are shown in FIGS. 2 to 5 involve comparatively complex arrangements. In practice, it may therefore often be expedient for reasons of cost for only two _einforcing sleeves 8 to be pushed concentrically over one another according to the example from
The materials which are used for producing the reinforcing sleeves 8 or 20 are likewise adapted to the mechanical stresses which act on the compressor wheel 2. The production of the reinforcing sleeves from a fiber-reinforced material has been found to be expedient.
A possible example for the production of a reinforcing sleeve 8 or 20 consists in producing a wound body of long-fiber material or of spun short-fiber material. In this case, the fibers are impregnated in a wax, resin or polymer. The impregnated material hardens after the wound body has been wound up, thereby resulting in “preforms” of the reinforcing sleeves 8, 20. These preforms of the reinforcing sleeves 8, 20 can be cut into segments having the desired lengths 10, in which case these segments, according to the mode of expression used here, may already be referred to as reinforcing sleeves 8, 20. These reinforcing sleeves 8, 20 can be attached to one another or pushed over one another, for example, by adhesive bonding, pressing, stitching, stacking or hot melting. Thus preliminary fixing already exists and already represents the cross-sectional geometry of the core structure 4.
Organic material such as wax or polymer is then melted or the resin or the polymer or the wax is burnt out of the reinforcing sleeves 8, 20. The reinforcing sleeves 8, 20, which are thus free of organic bonding agents, are placed in a casting mold and are infiltrated during the pouring with the metal melt, which also subsequently forms the functional section 6. In this case, a die-casting or a squeeze-casting process is expedient. If appropriate, the burning-out and the pouring of the metal melt can also be effected at the same time.
In another variant of the method of producing the core structure 4, fiber-reinforced wound bodies, which are inflitrated with polymers or resins or waxes, are produced in a similar manner to the preceding example and are assembled to form a core structure 4 similar to FIGS. 2 to 5, the organic material—wax, resin or polymer—is removed, and the core structure 4 is infiltrated with a special metal in a corresponding casting process, for example a die-casting process. The core structure 4 infiltrated in this way is then encapsulated with the functional section 6 in the precision casting or in another low-pressure casting process.
In the casting process described last, it may be expedient to provide the already pre-infiltrated core structure 4 with an adhesion layer so that the liquid metal adheres more effectively to the core structure during the integral casting of the functional section 6 and thus forms a firm bond.
In the cases in which the fiber wound body is infiltrated with liquid metal, it may possibly be expedient to coat the fibers, so that, on the one hand, a reaction of the infiltration metal with the fiber is avoided and, on the other hand, better wetting and better infiltration is ensured.
For reasons of cost, when less stringent mechanical demands are made on the compressor wheels 2 or in general on the high-speed impeller to be produced, the reinforcing sleeves may be produced, for example, from a wrought alloy, in particular an aluminum wrought alloy. The use of metal-matrix composites, which if appropriate are reinforced with short fibers, or the use of spray-compacted metallic materials may be expedient for the reinforcing sleeves 8, 20.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10341415.0 | Sep 2003 | DE | national |
