WO2008037640A1

WO2008037640A1 - Stator in an electric motor

Info

Publication number: WO2008037640A1
Application number: PCT/EP2007/059892
Authority: WO
Inventors: Achim Hawighorst; Guenter Kastinger
Original assignee: Robert Bosch Gmbh
Priority date: 2006-09-26
Filing date: 2007-09-19
Publication date: 2008-04-03
Also published as: DE102006045355A1; EP2070181A1

Abstract

A stator in an electric motor comprises a stator part configured as a hollow body, the part comprising a receiving space for receiving a rotating armature. The walls of the stator part are made of a magnetically conductive material and carry a magnet. In the circumferential direction, the walls of the stator part have a varying wall thickness, which is tapered in the region of the magnet and is configured in a reinforced manner, at least in some sections, in the region outside of the magnet. The stator is designed to have at least two parts, comprising an interior and an exterior stator part, wherein at least one of the stator parts has a varying wall thickness in the circumferential direction.

Description

description

title

Stator in an electric motor

The invention relates to a stator in an electric motor according to the preamble of claim 1.

State of the art

In US 4,973,871 described as a permanent-magnet DC electric motor is described, the stator has a receiving space for receiving a rotationally mounted armature, wherein on the stator inner walls opposite two opposite-pole permanent magnets are arranged. The stator has a non-round cross-sectional shape, wherein the walls of the stator in the region of the magnets have the cross-section diminishing flattenings and are formed in the remaining regions with a constant wall cross-section. Seen over the circumference of the stator thus has sections with tapered wall thickness and sections with greater wall thickness. Since such stators are usually made of magnetically conductive material, which leads to an increase in the magnetic flux in the material of the wall, an increase in the magnetic flux density is achieved by the cross-sectional reduction. The sections between the magnets with increased wall thickness ensure that the magnetic flux between the magnets is maintained.

However, due to the flattening on the outside of the stator in the region of the magnets, an edge arises in the transition between the tapered and reinforced wall section, which impairs a continuous magnetic flux and carries the risk of scattering losses.

For further prior art reference is still made to DE 198 37 134 Al, from which a magnetically conductive wall of a small electrical machine is known. The magnetic flux is in this small machine using a magnetically conductive Wall surrounding return ring made. Wall sections with reduced wall thickness are not provided in the stator of this small electrical machine.

In addition, reference is made to DE 101 44 914 A1, from which it is likewise known to form the stator in the circumferential direction with changing wall thickness, the magnets being arranged in the region of the reduced wall thickness.

Disclosure of the invention

The invention has for its object to reduce the weight of a stator in an electric motor without affecting the magnetic flux density with simple measures.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

According to the invention, the stator is constructed at least in two parts with a radially inner and a radially outer stator part, wherein at least one of the stator parts has an alternating wall thickness in the circumferential direction. The changing wall thickness, which changes continuously and without a jump in the circumferential direction, in particular as in the first aspect of the invention, enables a largely uniform magnetic flux between the north and south poles of the magnet or the magnets.

Possible is both an embodiment with a first stator with constant wall thickness and the second stator with changing wall thickness as well as a version with two stator with changing wall thicknesses that change in the circumferential direction and partially compensate or reinforce. If one of the stator parts has a constant wall thickness, then this can be both the inner and the outer stator ring, and accordingly the respective other stator part has an alternating wall thickness. The portions of tapered wall thickness are in turn at the level of the magnets, which are positioned on the inside of the stator. If, on the other hand, it is provided that both stator parts have a wall thickness which varies in the circumferential direction, the entire housing is Wall thickness in the radial direction, formed by the two directly superimposed stator parts, reduced in the region of the magnets and reinforced in the area outside the magnets.

Provide two or more stator parts in the radial direction offers the advantage of a larger structural design option. In addition, different materials can be used for the stator parts, whereby influence on the physical properties, in particular on the course of the magnetic flux density can be taken. The stability can also be improved, for example by the use of a particularly stable stator part.

According to an advantageous embodiment, the wall of the stator is made of magnetically conductive material and has an alternating wall thickness seen in the circumferential direction. In the areas that receive the magnets, the wall thickness is tapered, whereas the areas between the magnets are at least partially reinforced. In the circumferential direction, the transitions between the sections of tapered and reinforced wall thicknesses are continuous and free of cracks, so that both the envelope of the outer lateral surface and the first derivative of the envelope are continuous, expediently both on the inside of the stator and on the outside , By reducing the wall thickness in the region of the magnets, at least partial compensation with regard to the change in the magnetic flux along the magnetically conductive wall of the stator part is achieved. The larger wall thickness between the magnets allows a smooth flow without appreciable change in flux density and without wastage. At the same time, the weight of the stator part and thus of the stator can be reduced overall due to the sections with reduced wall thickness. As seen in the circumferential direction, the wall thickness changes smoothly and without jump, jumps in the magnetic flux density can be avoided.

Suitably, at least one stator part is ring-shaped or sleeve-shaped, so that a peripheral, closed wall is provided in the circumferential direction. The second stator part can either be ring-shaped or sleeve-shaped or According to an alternative embodiment, form individual segments that do not extend over the entire circumference, but only over a limited angle segment. These individual segments are connected to the annular or sleeve-shaped stator part and are located in particular at the sections where an overall greater wall thickness, formed by the summation of the inner and outer stator part, should be given. The individual stator segments can form either the inner stator parts or the radially outer stator parts.

Furthermore, it may be advantageous to provide an additional cylindrical holding part, which expediently likewise consists of magnetically conductive material and forms a stator part. This cylindrical holding part can be combined with the two inner and outer stator parts, of which at least one, if appropriate also both, have a wall thickness region which changes in the circumferential direction. However, the cylindrical holding part usually forms the innermost stator part, on the inner wall, the magnets are attached.

The inner stator part, on which the magnets are arranged, has a receiving space with a cylindrical cross-section, which is produced in two steps according to a preferred method for producing the stator. First, in a first step by forming, in particular by deep drawing, a cylindrical component having a constant wall thickness is produced, wherein the wall thickness is reduced in a subsequent, second step by forming, for example by means of rolling. In contrast to machining, the forming process has the advantage of solidifying the material. In order to obtain the circular inner diameter, it may be expedient, after the first forming step, first to impart to the stator part a non-circular inner diameter and to bring it into circular form only after the second step by the additional forming. The second step involves at the same time producing a section with a tapered wall thickness.

According to a further advantageous embodiment, a stator, which is in particular annular, formed in the circumferential direction alternately convex and concave, wherein the Transition between convex and concave sections advantageously continuous and jump-free.

Brief description of the drawings

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 in cross-section a stator of an electric motor designed as a small motor, wherein the stator has an inner, annular part with constant wall thickness and a radially outer annular stator part with variable wall thickness and placed on the inside of the inner stator two opposing magnets,

2 shows a cross section through a further embodiment of a

Stator having a cylindrical, inner stator part with a constant wall thickness and two outer stator segments, each with a variable wall thickness,

Fig. 3 shows a cross section through a further embodiment with an inner, cylindrical stator part with a constant wall thickness and an outer, annular

Stator part with changing wall thickness, adapted to a version with a total of four individual magnets,

Fig. 4 shows a cross section through a stator with four magnets, wherein the outer stator part four individual

Having segments of circumferentially variable cross section,

5 shows a longitudinal section through a stator of a small motor electric motor with inner and outer, respectively annular stator part, wherein the inner stator part, which receives the magnets, is open at both end faces, Fig. 6 is a Fig. 5 corresponding representation, wherein the inner

Stator part is cup-shaped with a closed end face,

7 to 14 different embodiments of a stator with inner and outer stator and variable total wall thickness,

15 to 17 a longitudinal section through in each case an electric motor with inner and outer stator.

In the figures, the same components with the same reference numerals.

Embodiment (s) of the invention

The illustrated in the following embodiments stator 1 is part of a designed as a small motor electric motor, which is in particular a permanent-magnet DC motor, which is used in auxiliary equipment in motor vehicles, for example, for the operation of sliding roofs, window regulators, windscreen wipers or the like.

1, the stator 1 comprises a radially inner, annular or sleeve-shaped stator part 2 and a radially outer, likewise annular or sleeve-shaped stator 3. In the inner stator 2 is an inner, cylindrical receiving space 6 for Recording of the rotating armature. At the

Inner wall of the inner stator part 2 opposite polarity permanent magnets 4 and 5 are arranged, which are formed part-circular and extend over a limited angular segment of the wall inside. Each magnet 4 or 5 covers an angular segment of slightly more than 90 °, so that between the magnets 4 and 5, an angular segment remains free, which extends approximately over an angular range of 60 to 80 °.

The inner stator 2 is cylindrical with a constant wall thickness. The outer stator 3 is located directly on the Lateral surface of the inner stator 2 and has in

Seen circumferentially a changing wall thickness. In the area of the magnets 4 and 5, the outer stator part 3 has a reduced wall thickness, whereas in the region of the segment section in which no magnets are arranged, the outer stator part 3 has a reinforced wall section. The transition between the wall sections with reduced wall thickness and the wall sections with greater wall thickness is fluent and continuous, avoiding jumps. The total wall thickness, formed by the inner stator part 2, the outer stator part 3 and the magnets 4 and 5, as far as they extend over the circumference, is selected such that an approximately constant wall thickness is provided in the circumferential direction over 360 °.

In the embodiment of FIG. 2, in contrast to the previous embodiment, the outer stator 3 is not designed as a continuous ring, but formed in two parts with two individual segments 3a and 3b, which extend along those angle sections at which no

Magnets are located. Viewed in the circumferential direction, each segment 3a and 3b, respectively, has a varying cross-section, which is greatest in the middle and continuously drops towards the two lateral ends. In the angular segment, which is covered by the magnets 4 and 5, there is no outer stator segment.

In the exemplary embodiment according to FIGS. 3 and 4, a total of four magnets 4, 5, 7 and 8 are distributed uniformly over the circumference on the inner casing of the inner stator part 2, which is designed as a ring or sleeve with a constant wall thickness. The outer stator part 3 is likewise designed in the shape of a ring or sleeve, but the wall thickness in the region of the angular segments which have a magnet is reduced and reinforced in the angular segment between two adjacent magnets. The transition between the different wall thicknesses is fluent. The angle segment with a magnet is about 60 °, the angle segment without a magnet about 30 °. According to FIG. 4, the outer stator part is four in total

Individual segments 3a, 3b, 3c and 3d carried out, which are respectively positioned in the angle sections in which there is no magnet. However, since each segment 3a to 3d extends over an angular range larger than the magnet free

Angle range, there is an overlap with the sections in which the magnets are added, wherein in the overlap region, the wall thickness of each segment 3a to 3d is already reduced. The wall thickness of each segment falls off towards each lateral end face. There is a gap between adjacent outer segments.

FIGS. 5 and 6 each show a longitudinal section through a stator 1 with an inner stator part 2 and an outer stator part 3 and a magnet 4 fastened to the inner wall of the inner stator part 2. According to Fig. 5, both stator parts are sleeve-shaped, the respective end faces are open. In the embodiment of FIG. 6, however, an end face of the inner stator 2 is formed closed, in the region of this end face is located in the wall of a bearing 9 for receiving the armature shaft of the electric motor.

The connection between the inner and outer stator 2 and 3 takes place in the case of a ring-shaped or sleeve-shaped outer stator by pressing, rolling, shrinking,

Embossing or similar. In the case of individual segments, these can be fixed by welding, riveting, embossing etc.

Suitable materials for the inner stator 2 and the outer stator 3 are magnetically conductive materials, in particular soft magnetic materials such as ferromagnetic materials. Possible is both a version with the same material for inner and outer stator and a version with different materials.

In the embodiment of FIG. 7, the stator is designed to accommodate four individual magnets, which are distributed over the circumference on the inside of the stator. The inner stator part has four individual stator segments 2a, 2b, 2c and 2d, each changing in the circumferential direction Have cross section and in the middle of the highest

Wall thickness and to the sides have a decreasing wall thickness. The four segments are designed as individual segments. The outer stator 3 is formed annular or sleeve-shaped and has an approximately constant wall thickness in the circumferential direction. The shape of the outer stator part 3 is convex-concave in the circumferential direction such that a total of four concave sections alternate with four intermediate convex sections. In the region of the convex portions seen from the outside, the individual segments 2a, 2b, 2c and 2d are located on the inside of the outer ring 3. The magnets are arranged in the region of the intermediate convex portions which are at least partially free of the inner segments.

In the embodiment of FIG. 8, the stator is designed to receive two individual magnets. The inner stator part 2 is made in two parts and has two opposite segments 2a, 2b, which are not connected to each other and have a cross-sectional shape executed in the manner described above. The outer, annular stator part 3 has an oval outer

Cross-sectional shape, the wall thickness of the outer stator 3 is not constant in the circumferential direction, it decreases in the direction of the individual sections out, in which there is no inner segment.

The embodiment of FIG. 9 corresponds in essential parts to that of FIG. 7, so that reference is made in this respect to the description there. In contrast to the embodiment of FIG. 7, however, in the embodiment of FIG. 9 is an additional cylindrical

Holding part 10 is provided, which forms the innermost stator. The cylindrical holding part 10 is made of magnetically conductive material, in particular of a soft magnetic material. The cylindrical holding part 10 has a constant wall thickness in the circumferential direction. On the outer side of the cylindrical holding part 10, the segments 2 a to 2 d of the outer stator part are fixed, on the inner wall, the magnets are arranged and fixed. The attachment of both the segments on the outside and the magnets on the inside can be done for example by means of punched and bent shots or tabs on the wall of the holding part 10.

In the embodiment of FIG. 10, the stator 1 is designed to receive two permanent magnets. As in the previous one

Embodiment, a cylindrical holding part 10 is provided, which forms the innermost stator. On the outside of the cylindrical holding part 10, two individual segments 2 a and 2 b of the inner stator part are fixed, each of the largest cross section towards the center and a sloping towards the sides

Have cross-section. The two segments 2a and 2b are enclosed by an annular, outer stator part 3, which has a constant wall thickness in the circumferential direction. In the overall cross section, the outer stator part 3 is elliptical.

The stator 1 shown in FIG. 11 has two stator parts 2 and 3, whose lateral surface is in each case convex and concave. In the case of both stator parts, convex sections with concave sections alternate in the circumferential direction. The wall thickness of the inner stator part 2 varies in the circumferential direction, wherein the convex portions have a greater wall thickness and the concave portions have a smaller wall thickness. The wall thickness of the outer stator 3, which is adapted to the outer circumferential surface of the inner stator, however, is constant. There are a total of four circumferentially distributed convex portions and four concave sections provided.

The stator 1 in the embodiment of FIG. 12 is designed to receive two permanent magnets and has two annular or sleeve-shaped stator 2 and 3, of which the inner stator 2 has an alternating wall thickness, whereas the outer stator 3 has a constant wall thickness , Both stator parts 2 and 3 have an elliptical cross-sectional shape.

In the embodiment according to FIG. 13, three stator parts are provided, namely, in addition to the inner stator part 2 and the outer stator part 3, the cylindrical holding part 10, which forms the radially innermost stator part. The embodiment according to FIG. 13 essentially corresponds to that according to FIG. 9, However, with the difference that the inner stator 2 is formed as a circumferential ring, whereas in FIG. 9, the stator 2 has individual, independent segments 2a to 2d. In Fig. 13, the magnets 4, 5, 7 and 8 are additionally registered, which are each in the range of angular segments with a small wall thickness.

The embodiment according to FIG. 14 corresponds to that according to FIG. 12, but in FIG. 14 additionally two permanent magnets 4 and 5 are arranged on diagonally opposite inner sides of the inner

Stator part 2 located. The magnets 4 and 5 are in the range of thinner wall thicknesses of the inner stator 2.

FIGS. 15 to 17 show further exemplary embodiments of stators 1 in longitudinal section. According to FIG. 15, the inner stator part 2 has a ring-shaped or sleeve-shaped design, whereas the outer stator part 3 is additionally closed at one end side and therefore has a pot shape. In the area of the front side is located in the wall, a bearing 9 for supporting the armature shaft.

The embodiment according to FIG. 16 corresponds in principle to that according to FIG. 15, but in FIG. 16 additionally a magnet 4 is drawn on the inner wall of the inner stator part 2.

In the embodiment of FIG. 17 inner stator 2 and outer stator 3 are each formed as a sleeve which is open at both axial ends.

Claims

claims

1. stator in an electric motor, in particular a permanent-magnet DC motor, in particular in auxiliary devices in motor vehicles, with a hollow body formed as a stator (2, 3) with a receiving space (6) for receiving a rotating armature, wherein the wall of the stator (2, 3) consists of magnetically conductive material and carrier of a magnet (4, 5, 7, 8) and in the circumferential direction has an alternating wall thickness, such that the wall thickness in the region of the magnet (4, 5, 7, 8) tapers and im Area outside the magnet (4, 5, 7, 8) at least partially reinforced, characterized in that the stator (1) is at least two parts with an inner and an outer stator (2, 3), wherein at least one of the stator (2, 3) has an alternating wall thickness in the circumferential direction.

2. Stator according to claim 1, characterized in that in the circumferential direction, the transitions between sections of tapered and reinforced wall thicknesses in at least one

Stator part (2, 3) continuously and free of cracks.

3. Stator according to claim 2 or 2, characterized in that the outer stator part (3) has an alternating wall thickness in the circumferential direction.

4. Stator according to one of claims 1 to 3, characterized in that the inner stator part (2) has an alternating wall thickness in the circumferential direction.

5. Stator according to one of claims 3 to 4, characterized in that the stator part (2, 3), which changes in the circumferential direction Has wall thickness, as a stator segment (2a to 2d; 3a, 3b) is executed, which extends only over a partial circumference.

6. Stator according to claim 5, characterized in that in the circumferential direction a plurality of stator segments (2a to 2d; 3a, 3b) are provided.

7. Stator according to one of claims 1 to 6, characterized in that a stator part (2, 3) is cylindrical with a constant wall thickness.

8. Stator according to one of claims 1 to 7, characterized in that the inner and / or the outer stator part (2, 3) are made of soft magnetic material.

9. Stator according to one of claims 1 to 8, characterized in that three radially intermeshing stator (2, 3, 10) are provided, one of which is designed as a cylindrical holding part (10).

10. Stator according to claim 9, characterized in that the cylindrical holding part (10) forms the radially innermost stator part.

11. Stator according to one of claims 1 to 10, characterized in that a stator part (2, 3) in the circumferential direction has alternately convex and concave shaped portions.

12. A method for producing a stator, in particular according to one of claims 1 to 11, characterized in that in a first step, the stator (2, 3) is produced by deep drawing as a component with a constant wall thickness and in a second step, the wall thickness in the area of the at least one magnet to be attached (4, 5, 7, 8) is reduced by forming.

13. The method according to claim 12, characterized in that the reduction of the wall thickness takes place by means of rolling.

14. The method according to claim 12 or 13, characterized in that the stator (2, 3) after the deep drawing carried out in the first step has a deviating from the circular cross-sectional shape inner diameter and only after the second step by the additional forming a circular inner diameter is set ,