DE102011089517A1 - Method for producing a machine element and machine element for an electrical machine - Google Patents

Abstract

The invention relates to a method for producing a machine element (1), in particular for a stator or a rotor of an electrical machine, comprising the following steps: - providing a magnetic powder material with elongated magnetic powder particles (12) in a mold; - applying a magnetic field, which penetrates the provided powder material; - compacting the powder material in the mold (17); and - bonding the powder particles to obtain the machine element (1).

Description

Technical area

The present invention relates to machine elements for electrical machines, in particular machine elements for guiding a magnetic field for a stator or a rotor of the electric machine. The invention further relates to methods for producing such machine elements.

State of the art

In addition to the lamination structure of machine elements is also known to build machine elements for conducting magnetic fields from soft magnetic composite (SMC) powder materials, such as Somaloy 700, the example of "Somaloy Technology", Somaloy Brochure, December 2010, Höganäs AB, Sweden, www.hoganas.com , are known.

SMC materials are composed of surface-isolated iron particles that are unevenly shaped but have an approximately spherical structure of the same size. The powder materials have particles of iron compounds having a size suitable for pressing and forming machine elements. The particles may, for example, have dimensions of about 0.1 mm and be compressed in a single step with pressures of about 800 MPa to obtain magnetic machine elements with complex shapes and close tolerances. The compressed SMC machine elements are then heated at temperatures of about 500 ° C for about 30 minutes to obtain the machine element.

A disadvantage of the powder material used is that it can only obtain machine elements with isotropic magnetic properties in all spatial directions. While this is advantageous for electric machines having three-dimensional magnetic flux characteristics such as axial field machines, claw pole machines and transverse flux machines, in other types of electric machines, the magnetic field corresponds to a radial field type in which the magnetic flux lines are substantially one-dimensional and certain small areas of the magnetic circuit in two spatial directions.

It is an object of the present invention to provide a machine element made of a powder material for pressing and having improved magnetic properties and an improved method for producing such a machine element.

Disclosure of the invention

This object is achieved by the method for producing a machine element for an electrical machine according to claim 1 and by the machine element for an electrical machine according to the independent claim.

Further advantageous embodiments of the present invention are specified in the dependent claims.

• – Bereitstellen eines magnetischen Pulvermaterials mit länglichen magnetischen Pulverpartikeln in einer Pressform;
• – Anlegen eines Magnetfelds, das das bereitgestellte Pulvermaterial durchdringt;
• – Verdichten des Pulvermaterials in der Pressform;
• – Verbinden der Pulverpartikel, um das Maschinenelement zu erhalten.

According to a first aspect, a method for producing a machine element, in particular for a stator or a rotor of an electric machine, is provided. The method comprises the following steps:

• Providing a magnetic powder material with elongated magnetic powder particles in a mold;
• - applying a magnetic field, which penetrates the provided powder material;
• - compacting the powder material in the mold;
• - Connecting the powder particles to obtain the machine element.

An idea of the above method for manufacturing a machine element is to expose a powder material with elongated magnetic particles during or before pressing a magnetic field having substantially the same field line direction inside the machine element to be formed as the field line direction of a magnetic field, the machine element in later use is exposed in an electrical machine. This aligns the elongated powder particles along the magnetic field lines. After application or during the application of the magnetic field, the powder material is pressed to obtain the solid machine element. The previously oriented magnetic particles maintain their alignment. Due to the corresponding orientation of the magnetic powder particles, there are fewer interfaces between adjacent powder particles in the material of the machine element thus produced in the direction of alignment of the magnetic powder particles than in a transverse direction. As a result, the magnetic conductivity is significantly increased in the direction of alignment of the magnetic powder particles with respect to transverse directions.

Furthermore, the densification of the powder material may be performed during the applied magnetic field.

According to an embodiment, the compacting of the powder material may be performed after the magnetic field has been applied.

It can be provided that during the application of the magnetic field, the mold and / or the powder material is exposed to one or more shocks and / or vibrations.

Furthermore, the elongated magnetic powder particles may have a length to width ratio between 2 and 5.

In particular, the proportion of the elongated magnetic powder particles in the powder material may be at least 50%, in particular at least 80%.

• – das magnetische Pulvermaterial mit länglichen magnetischen Pulverpartikeln in einer Pressform bereitgestellt wird;
• – ein Magnetfeld angelegt wird, das das bereitgestellte Pulvermaterial durchdringt;
• – das Pulvermaterial in der Pressform verdichtet wird;
• – die Pulverpartikel verbunden werden, um das Maschinenelement zu erhalten.

According to a further aspect, a machine element, in particular for a stator or a rotor of an electrical machine, is provided, wherein the machine element is made of a magnetic powder material with elongated magnetic powder particles, by

• - The magnetic powder material is provided with elongated magnetic powder particles in a mold;
• - A magnetic field is applied, which penetrates the provided powder material;
• - The powder material is compacted in the mold;
• - The powder particles are connected to obtain the machine element.

According to a further aspect, a machine element, in particular for a stator or a rotor of an electric machine, is provided, wherein the machine element has at least one region in which elongated magnetic powder particles are arranged adjacent to one another, their longitudinal axes being aligned parallel to one another.

One idea of the above machine element is to build it up with a powdery material having elongated magnetic particles. The particles are aligned by magnetic field lines at or before compression along the preferential direction, so that along the field lines improved magnetic permeability, i. H. magnetic conductivity, is present, while the magnetic conductivity is relatively lower in transverse directions. By providing elongated particles, it is possible to achieve a significant improvement of the magnetic conductivity in a field line direction at low particle volume.

Brief description of the drawings

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

1 a schematic cross-sectional view of the internal structure of a compressed SMC material, which is produced according to a conventional method;

2 a representation of the internal structure of an anisotropic SMC material prepared by a method according to an embodiment of the present invention;

3 a detail of a machine element of an electric machine with indicated flux lines of the magnetic field;

4a to 4d Charts showing the directions of magnetic field lines in the in 3 marked areas A, B, C, D represent;

5 a further illustration of the machine element of 3 with enlarged illustrated powder particles of the SMC material;

6 a magnetizing arrangement for applying a magnetic field through the machine element to be produced 3 to align the elongated powder particles.

Description of embodiments

1 shows a schematic cross-sectional view through a section of a machine element 1 which has been made with a SMC material. The SMC material consists essentially of powder particles 2 the same size of a magnetic material, such. As iron, the surface through an insulating layer 3 is isolated. The powder particles 2 have a diameter of about 0.1 mm and are about cubic or spherical with irregular shaped surface.

The particles 2 are pressed together in a pressing process to a shape of the machine element to be produced 1 to be defined, and then cured in a heating process, so that the powder particles permanently connect to each other. 1 shows an exemplary arrangement of the powder particles 2 after the heating process. One recognizes the powder particles 2 same size, which abut each other, so that the area of the spaces between the particles 2 minimized as possible.

Due to the same size of powder particles 2 of the SMC material are the magnetic properties of a machine element thus produced 1 the same in all spatial directions, ie the material of the machine element behaves isotropically with respect to its magnetic properties. In particular, however, the magnetic conductivity in the direction of the magnetic field lines F by the Number of interfaces 4 between each two powder particles 2 along the field lines F determined.

To the number of interfaces 4 to reduce, in principle, an enlargement of all dimensions of the particles 2 into consideration. However, this leads to correspondingly larger spaces between the individual powder particles 2 because the powder material can not be completely compressed, ie without the existence of gaps. Larger gaps, however, have a negative effect on the magnetic conductivity and therefore do not lead to a desired improvement in the magnetic conductivity or even to their reduction.

It is therefore, as in 2 shown, provided a machine element 10 with elongated powder particles 12 train. The powder particles 12 are otherwise, ie regardless of their size, with which the 1 comparable. This ensures that before curing to the shape of the machine element 10 pressed powder particles 12 these are aligned along a desired field line direction of the magnetic field. 2 shows powder particles 12 whose longitudinal axes are parallel to one another, corresponding to the direction of the indicated magnetic field lines F.

The elongated powder particles 12 , in the 2 have substantially a cross-sectional area transverse to their longitudinal extent, which are about the same size as that of the powder particles 2 of the 1 has, ie, a diameter or width w _p between w _p = 0.05 to 0.3 mm. The length l _{p of} the powder particles 12 However, compared to conventional powder particles of SMC material is significantly increased. The ratio of the length l _{p of} the powder particles 12 to the width w _{p of} the powder particles 12 is between 2 and 5. The thickness of the powder particles 12 ie in z direction in 2 , corresponds approximately to the width w _p .

This means that the isolated powder particles 12 may have a size l × w × t of about 0.2 to 0.5 mm × 0.1 mm × 0.1 mm.

The advantage of the above powder particles 12 Composite material is that it can be formed into arbitrarily shaped bodies with anisotropic magnetic properties. Thereby, a higher conductivity in a preferred magnetic direction can be achieved compared to isotropic magnetic properties of conventional machine elements made of a powder material, as in connection with 1 described.

In the arrangement of the elongated powder particles 12 as they are in 2 are the number of boundary points 14 , on each of which two powder particles 12 abut one another, in the direction of the longitudinal direction of the powder particles 12 , ie in the direction of the field lines F, significantly reduced, so that in this direction an improved magnetic conductivity is achieved.

In 3 is the magnetic field in stator segments with a T-shaped stator tooth and with a magnetic return region for an electric machine as an example of a machine element by means of field lines 10 of the 2 shown in more detail. The inside of the machine element 10 The lines shown represent the field lines of the magnetic field.

The 4a to 4d show by closed circulation curves the directions of magnetic field lines F in the in 3 marked areas A, B, C, D, which are assumed during a revolution of the permanent magnet excited rotor. Plotted are the radial R and tangential T components of the magnetic flux in the tooth shank A, the tooth shoe B, the tooth root C and the magnetic return area D, as in FIG 3 shown. It can be seen that a magnetic flux essentially exists only in one direction, in particular in the toothed shaft A and in the magnetic return region D. In the areas of the tooth root C and the tooth shoe B, on the other hand, magnetic fluxes occur in two spatial directions, ie both in the radial direction R and in the tangential direction T of the machine element 10 to be formed stator, on.

In 5 are for the in 3 shown areas A, B, D, the orientations of the elongated powder particles 12 shown after magnetizing the machine element 10 during manufacture. Illustrative are the powder particles 12 shown enlarged in order to recognize their orientation with respect to the magnetic field lines F can. It can be seen that the powder particles 12 aligned along the magnetic field lines.

As in 6 is shown for producing such a machine element 10 a powder material with elongated powder particles 12 , as in connection with 2 described and provided in a cavity of a mold 17 introduced, the shape of the machine element to be produced 10 Are defined. In the present example, the manufacturing method using an approximately T-shaped machine element 10 as in 3 shown, explained.

After the powder material into the cavity of the mold 17 was filled, are the powder particles 12 in a loose and not compressed form. The loose powder particles 12 have a relatively low magnetic conductivity, since they are not initially aligned and thus large gaps between the powder particles 12 resulting in significantly influence the magnetic resistance. However, the magnetic conductivity is sufficient to provide a nearly uniformly aligned magnetic field in the machine element 10 so that the alignment process can be started.

The mold 17 is then exposed to a magnetic field corresponding in direction to the magnetic field to which the machine element 10 is exposed during subsequent operation after its completion.

For example, a magnetizing arrangement 15 according to 6 for producing the T-shaped machine element 10 of the 3 be provided. The magnetizing arrangement 15 of the 6 has two coupled magnetic circuits for guiding two magnetic fields. The magnetic fields are generated by energizing a coil winding 16 generated, which is a middle leg of the Magnetisieranordnung 15 which is part of both magnetic circuits.

The magnetic circuits are interrupted at a tee to form a correspondingly shaped die 17 for producing the T-shaped machine element 10 of the 3 take. The mold 17 is so on the Magnetisieranordnung 15 put on or inserted into the interruption of the magnetic circuits, that in the Magnetisieranordnung 15 generated magnetic field the mold 17 and that in the cavity of the mold 17 introduced introduced powder material. In the embodiment shown, the mold is so to the Magnetisieranordnung 15 set up that the toothed shaft forms an extension of a central leg, in which the magnetic field in comparison to other areas of the Magnetisieranordnung 15 has the highest field strength. The two opposite ends of a yoke portion of the T-shaped machine element 10 lie in each case at two further poles of the magnetizing arrangement 15 at. The magnetic field lines extend radially along the toothed shaft and share towards the two opposite ends of the yoke portion. In the radially inner region, a tooth head is formed in the exemplary embodiment in which the magnetic field lines fan out inwardly in accordance with the contour of the tooth head. The machine element 17 is for example designed as a stator element or rotor element which can be wound with an electric coil and a plurality of such elements can be joined together to form a circular stator or rotor.

In the process, the mold becomes 17 subjected to a magnetic field corresponding in direction to the magnetic field, the machine element 10 is exposed during subsequent operation after its completion. As a result, the magnetic field lines through the powder material in the cavity of the mold correspond 17 essentially those, as in the electric machine, in which the machine element 10 is used during operation.

A pressing of the elongated powder particles 12 while the magnetic field to the mold 17 is applied, leads to a movement of the elongated powder particles 12 and a reorientation of the elongated powder particles 12 in the direction of the magnetic field, with the longitudinal axes of the powder particles 12 align in the direction of the magnetic field lines F. For pressing, a pressure on the powder particles 12 exercised, so that the powder particles 12 move, rotate by their movement and thereby align themselves according to the applied magnetic field. This improves the magnetic conductivity of the powder material as its density increases, thereby further increasing the strength and orientation of the magnetic field in the powder material during the pressing process.

To assist in the process of aligning the elongated powder particles 12 can the mold 17 shaken or otherwise exposed to shock or vibration, so as to achieve optimal alignment of the largest possible proportion of the elongated powder particles 12 to reach.

By subsequent further pressing of the powder material, removal from the Magnetisieranordnung 15 and performing a subsequent heating process, the powder particles become 12 permanently with each other to the machine element 10 connected. The previously caused by the magnetic field orientation of the individual powder particles remains 12 consist.

The above manufacturing method and machine elements made by it are not only useful for stator teeth, but can also be used for complete magnetic circuits for any kind of electric machines.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• "Somaloy Technology", Somaloy Brochure, December 2010, Höganäs AB, Sweden, www.hoganas.com [0002]

Claims (10)

Method for producing a machine element ( 10 ), in particular for a stator or a rotor of an electrical machine, comprising the following steps: - providing a magnetic powder material - preferably soft magnetic composite (SMC) material - with elongated magnetic powder particles ( 12 ) in a mold ( 17 ); - applying a magnetic field, which penetrates the provided powder material; - compacting the powder material in the mold ( 17 ); - bonding the powder particles ( 12 ) to the machine element ( 10 ) - in particular sintering or curing. The method of claim 1, wherein the compacting of the powder material is performed during the applied magnetic field and / or after the magnetic field has been applied. Method according to claim 1 or 2, wherein during the application of the magnetic field the powder material and / or the mold ( 17 ) is exposed to one or more shocks and / or vibrations. Method according to one of claims 1 to 4, wherein the elongated magnetic powder particles ( 12 ) have a length to width ratio between 2 and 5 - wherein in particular this length to width ratio of a maximum length l _p and a maximum width w _{p of} the powder particles ( 12 ) is determined. Method according to one of claims 1 to 4, wherein the proportion of the elongated magnetic powder particles ( 12 ) in the powder material is at least 50%, in particular at least 80%. Machine element ( 1 ), in particular for a stator or a rotor of an electrical machine, - preferably produced by a method according to one of claims 1 to 5 - wherein the machine element ( 10 ) of a magnetic powder material - preferably soft magnetic composite (SMC) material - with elongated magnetic powder particles ( 12 ) is prepared by - the magnetic powder material with elongated magnetic powder particles ( 12 ) in a mold ( 17 ) provided; - A magnetic field is applied, which penetrates the provided powder material; The powder material in the mold ( 17 ) is compressed; The powder particles ( 12 ) - in particular sintered or hardened - to the machine element ( 10 ) to obtain. Machine element ( 10 ), in particular for a stator or a rotor of an electrical machine, wherein the machine element ( 1 ) has at least one region in which elongated magnetic powder particles ( 12 ) are arranged adjacent to each other, wherein the longitudinal axes are aligned parallel to each other. Machine element ( 10 ) according to claim 6 or 7, characterized in that the machine element ( 10 ) is formed approximately T-shaped and a radial toothed shaft with substantially radially oriented powder particles ( 12 ), and having a circumferentially extending yoke portion in which the powder particles ( 12 ) are aligned substantially tangentially to the circumferential direction. Machine element ( 10 ) according to claim 6 to 8, characterized in that the elongated magnetic powder particles ( 12 ) have a length to width ratio between 2 and 5 - in particular this length to width ratio of a maximum length l _p and a maximum width w _{p of} the powder particles ( 12 ) is determined. Machine element ( 10 ) according to one of claims 6 to 9, characterized in that the proportion of the elongated magnetic powder particles ( 12 ) in the powder material is at least 50%, in particular at least 80%.

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