Method for producing a rotor for an electric motor

Abstract

A method for producing a rotor body includes producing one or more fiber strips from fiber material, and providing cutouts in the fiber strip or in the fiber strips. The fiber strip or the fiber strips are oriented in relation to one another such that at least one of the cutouts lies on another of the cutouts so that cutouts which lie one above the other form a three-dimensional receptacle for a magnet. A rotor for an electric motor with a rotor body is also provided.

Claims

1. A method for producing a disc-shaped rotor body, the method comprising the following steps: producing at least one fiber strip of fiber material; providing recesses in the fiber material of the at least one fiber strip; aligning the at least one fiber strip causing at least one of the recesses to lie on top of another one of the recesses and causing the recesses lying on top of each other to form a three-dimensional receptacles in the disc-shaped rotor body; and placing magnets in the receptacles.

2. The method according to claim 1, which further comprises producing the at least one fiber strip as several ring-segment-shaped or circular-ring-shaped fiber strips each having at least one respective recess.

3. The method according to claim 1, which further comprises producing the at least one fiber strip as a spiral fiber strip with several recesses.

4. The method according to claim 1, which further comprises placing the at least one fiber strip in a cavity.

5. The method according to claim 4, which further comprises: providing placeholders in the cavity; and placing the at least one fiber strip in the cavity causing the placeholders to be provided in the receptacles for later installation of the magnets.

6. The method according to claim 1, which further comprises providing the rotor body with a circular cross section defining a circle center of the rotor body, and spacing the receptacles equally from the circle center of the rotor body.

7. The method according to claim 1, which further comprises producing the at least one fiber strip by weaving.

8. The method according to claim 7, which further comprises weaving the recesses into the at least one fiber strip.

9. The method according to claim 7, which further comprises shifting a part of the fiber material of the at least one fiber strip to form the recesses in the at least one fiber strip after the weaving of the at least one fiber strip.

10. The method according to claim 1, which further comprises providing a higher number of fibers per volume in an edge region of the at least one fiber strip than an average number of fibers per volume of the entire at least one fiber strip.

11. The method according to claim 1, which further comprises bringing the at least one fiber strip into contact with a polymer after aligning the at least one fiber strip.

12. The method according to claim 11, which further comprises selecting the polymer as a duromer, an elastomer or a thermoplast.

13. The method according to claim 11, which further comprises hardening the polymer.

14. The method according to claim 1, which further comprises hardening the polymer by increasing at least one of pressure or temperature.

15. The method according to claim 13, which further comprises placing the magnets in the receptacle of the rotor body after hardening of the polymer.

16. The method according to claim 1, which further comprises producing the rotor body from a carbon fiber reinforced plastic.

17. A rotor for an electric motor, the rotor comprising: a disc-shaped rotor body formed of at least one fiber strip of fiber material; said at least one fiber strip having recesses formed in said fiber material of said at least one fiber strip; said at least one fiber strip being aligned to cause at least one of said recesses to lie on top of another one of said recesses and to cause said recesses lying on top of each other to form three-dimensional receptacles; and magnets disposed in said receptacles.

18. The rotor body according to claim 17, wherein said magnets are permanent magnets.

19. The rotor body according to claim 18, wherein said permanent magnets are each disposed in a respective one of said receptacles.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention as well as further details and embodiments of said invention are described in more detail by schematic drawings in the following. Hereby, the figures show different process steps of producing a rotor body according to the invention:

(2) FIG. 1 the weaving of a fibre strip,

(3) FIG. 2 a woven spiral fibre strip,

(4) FIG. 3 the inserting of a fibre strip in a cavity,

(5) FIG. 4 the placeholders arranged in the cavity,

(6) FIG. 5 the contacting of the fibre strip with a matrix and the hardening of the rotor body and

(7) FIG. 6 a rotor produced according to the invention.

DESCRIPTION OF THE INVENTION

(8) In the FIGS. 1 to 6, the production process of a rotor for an electric motor according to the invention is schematically shown, particularly for an electric motor as described in DE 10 2006 036 707. The rotor is produced from a fibre composite material and comprises a plurality of magnets, which are arranged evenly and with equal distance from the rotor axis.

(9) The rotor comprises a disc-shaped rotor body which is of a carbon fibre-plastic-composite material. Instead of carbon fibres, glass fibres, aramid fibres, basalt fibres or other synthetic or natural fibres, fibres from synthetic polymers or manufactured inorganic fibres or a combination of said fibres can be used.

(10) To produce said rotor, carbon fibres are initially woven to a spiral fibre strip. Several so-called warp fibres 1 form a carrier, in which weft fibres 2 are inserted (see FIG. 1). The fibres 1, 2 are interwoven according to the so-called reverse weft method. The weft fibres 2 are preferably inserted at right angles to said warp fill tires 1. After crossing the outermost warp fibres 3, 4, the weft fibre 2 is woven between the warp fibres 1 in reverse direction. By reversing the direction of the weft fibres 2 at the edge of the fibre strip to be produced, the edge region of said fibre strip will be enhanced and stable edges 5 are formed. Moreover, the warp fibres 1 are arranged more closely at the edge regions, whereby said edge regions are additionally enhanced.

(11) At certain regions, the weft fibres 2 are not woven over the entire width of the fibre strip to be produced, to say not from the outermost warp fibre 3 to the opposite outermost warp fibre 4. The direction of a weft fibre 2 is reversed at a warp fibre 6 lying between the outermost warp fibres (half reverse weft). After several such half reverse wefts, a complete weft follows, to say the weft fibre 2 is pulled through from the outermost warp fibre 3 to the other outermost warp fibre 4. This way, a recess or opening 7 is formed, in which no crossing warp and weft fibres are present.

(12) By the above-mentioned method, a long spiral fibre strip 8 (see FIG. 2) is produced, which comprises recesses 7 at predetermined points. Said spiral fibre strip 8 has, for instance, an inner diameter 9 between 50 and 100 mm and an outer diameter 10 between 250 and 300 mm.

(13) Instead of the above-mentioned, immediate weaving of the recesses 7 into the fibre strip, it is also possible to interweave the warp fibres 1 and the weft fibres 2 over the entire width and length of said fibre strip and subsequently shifting said warp fibres 1 and said weft fibres 2 so that the desired recesses 7 are provided.

(14) The dimensions of the fibre strip, particularly its inner diameter 9 and its outer diameter 10, are chosen in dependence of the size of the rotor to be produced. The outer diameter 10 is, for instance, between 150 mm and 600 mm, for common electric motors and generators. It is also certainly possible to employ the invention with larger dimensions for producing rotors of electrical machines. For instance, rotor bodies with an outer diameter between 1000 mm and 3000 mm can be produced by the method according to the invention, as employed in generators for wind power plants.

(15) The length of the fibre strip 8 is provided such that the spiral stapled fibre strip 8 corresponds to the thickness of the rotor body to be produced after the compressing and hardening. Due to the compaction occurring during the compressing of the fibre strip, a certain excess length has to be calculated for said fibre strip, to say the stapled fibre strip 8 has a larger thickness before the compressing step than the final rotor body shall have.

(16) In a next process step, the fibre strip 8, as shown in FIG. 3, is placed in a cavity 11. Said cavity 11 corresponds to the negative form of the desired rotor body.

(17) In FIG. 4, a cut through the cavity 11 is shown. At the bottom of the cavity 11, a plurality of placeholders 12 is arranged in a circular manner. The placeholders 12 can be, for instance, of the same material as the rest of the cavity 11 and said placeholders are firmly connected with said cavity. Au lieu of the firm connection with the cavity 11, the placeholders 12 can also be movable, in particular shiftable, and preferably shiftable in the direction parallel to the symmetry axis of the cavity 11 and parallel to the rotation axis of the rotor body to be produced (hereinafter called z-axis). The placeholders 12 are provided at the points, at which the magnets are provided after completion of the rotor body.

(18) The fibre strip 8 is placed in the cavity 11, wherein the placeholders 12 are placed in the recesses 7 of the fibre strip 8.

(19) After the fibre strip 8 has been placed in the cavity until the desired thickness 13, a polymer 14, which is used as matrix for the fibre-enhanced rotor body, is placed in the cavity 11. The polymer 14 is preferably a duromer, an elastomer or a thermoplast, for instance, a synthetic resin or an epoxy resin or a ceramic material. Alternatively, the prefabricated fibre strip can already be soaked with a polymer.

(20) This way, the fibre strip 8 is embedded in a polymer matrix 14. Said polymer 14 is then hardened by a temperature increase and a pressure increase. For this, the cavity 11 is heated and the fibre strip 8, which is in the cavity 11, is compressed by a plunger 15 (FIG. 5).

(21) After hardening of the fibre strip-polymer-compound, the produced rotor body 16 is removed from the cavity 11. The produced rotor body 16 is ring-shaped and disc-shaped and comprises a plurality of receptacles 17 arranged in a circular manner. The receptacles 17 are provided at those points which have been kept free by the placeholders 12.

(22) Finally, magnets are placed in the receptacles 17 and then said magnets are fixed in the receptacles, for instance, glued in the receptacles 17.

(23) By using the invention, it is possible to produce a rotor body 16 with receptacles 17 in a continuous production process. The previously necessary process step, to say to drill, to cut, to mill or to waterjet receptacles 17 for magnets into the rotor body 16, is no longer necessary.

(24) In another embodiment of the invention, the magnets, which shall be arranged in the finished rotor body 26, shown in the process step in FIG. 4 are used as placeholders 12. As mentioned with regard to the embodiment above, the magnets are fixed to the desired positions in the cavity 11 or shifted in the recesses in the direction of the z-axis by a shifting system. Thereby, the movable placeholders can be shifted into the lower half of the cavity 11 or into the plunger 15.

(25) After infilling/injecting respectively by vacuum infusion of the polymer 14 such as a synthetic resin in the cavity 11, the compressing and the hardening the composite material, which is made of the fibre strip 8 and the polymer 14, the magnets are firmly embedded in the rotor body 16 and encapsulated together with the fibre strip 8. By this embodiment of the invention, the complete rotor of rotor body 16 and magnets can be produced in a continuous process.

(26) The rotor body 16 produced according to the invention is preferably used as rotor in an electric motor or generator, for instance, in a transverse flux machine.