DE102012224012A1 - Spool for mounting on a magnetic core, reluctance resolver and method of manufacture - Google Patents

Abstract

The present invention relates to a coil former (100) for mounting on a magnetic core (118) of a rotating electrical machine and to a magnetoelectric angle sensor, in particular a reluctance resolver, the stator of which is constructed according to the principles of the invention. The coil former has a winding body (102) for applying a winding, the winding body (102) having a receptacle (124) for receiving a tooth (116) of the magnetic core (118), the winding body (102) having a partially open cross section , so that the coil former (100) can be pushed onto the tooth in a direction transverse to a longitudinal axis of the tooth (116), and the coil former (100) is shaped in such a way that it interacts with the magnetic core (118) for fixing. Furthermore, at least one guide element (134) can be provided for guiding a coil wire (111) during the winding of the coil body (100).

Description

The present invention relates to a bobbin for mounting on a magnetic core of a rotating electrical machine and to a magnetoelectric angle sensor, in particular a reluctance resolver whose stator is constructed according to the principles of the invention. Finally, the present invention relates to a manufacturing method for producing such a reluctance resolver.

Such reluctance resolvers have a rotationally symmetrical, at least partially soft magnetic stator and a rotationally symmetrical, at least partially soft magnetic rotor, which face each other to form an air gap. The magnetic resistance in the air gap changes periodically due to a circumferentially varying configuration of the rotor.

The angle sensor has a magnetic flux transmitter arranged on the stator, which generates a predetermined magnetic flux distribution in the air gap via at least one pole pair. Furthermore, a magnetic flux receiver is arranged on the stator, which measures the intensity of the magnetic field via at least two mutually offset signal poles, wherein an angle value for a relative position of the rotor relative to the stator can be derived from the two receiver signals.

Such angle sensors, which are based on the principle of a variable magnetic flux intensity in the air gap between the stator and rotor, are known in many ways. In principle, different principles for generating the magnetic flux in the transmitting part and also different principles for magnetic field measurement in the receiver part come into consideration. The resolvers, ie the resolvers and syncros, use electromagnetic coils in the form of primary and secondary windings. Such resolvers in the form of resolvers and syncros have long been known as accurate and robust angle sensors. In this case, so-called passive reluctance resolver are known in which both the primary winding and the secondary winding are accommodated on the stator, while the rotor without development, so passive, only with soft magnetic parts affects the magnetic flux circuit. By an uneven design of the soft magnetic rotor, for example by providing cams (English "lobes"), the magnetic flux between the primary windings and the secondary windings in the stator is influenced differently, from which can be derived via the induced voltage, the angular position of the rotor.

For the production of such a stator, there are various technical implementation possibilities. On the one hand, the windings can be wound directly onto one or more teeth of the magnetic core. On the other hand, there is the possibility for winding schemes, in each of which only a single tooth is enclosed by the one or more windings, to first apply the windings to plastic bobbins and to push these bobbins onto the teeth of the magnet core during assembly. Such an arrangement is for example from the US 5,300,884 known. In this arrangement, however, no mechanical fixing possibility is given as the bobbin could be held on the magnetic core until the final attachment, z. B. on the circuit board, which accomplishes the wiring is mounted. A similar arrangement is also from the DE 10 2009 061 032 A1 known

It is also known to fix the bobbins to the magnetic core by means of special holding structures, as for example in the DE 10 2010 004 887 A1 is shown.

However, the above-mentioned known bobbins are first wound and then mounted in a direction along the longitudinal axis of the individual teeth on the magnetic core. Subsequently, an electrical contacting of the separated individual terminals of the coils, for example via a printed circuit board (PCB), take place. This approach requires a high number of items and a lot of effort during assembly and contacting.

On the other hand is from the US 7,385,323 B2 It is known that the coil windings can not be applied to the bobbin until it is already mounted on the magnet core. In the arrangement of the US 7,385,323 B2 For example, the metallic magnetic core is initially surrounded by two plastic half-shells and then applied the winding. The coil wire is then wound on the insulator shells and through the slots formed on each side of the magnetic pole teeth to form a plurality of coils in a circular series connection. The upper and lower insulator half shells interact with each other to fix the coil bobbins to the magnetic core.

A disadvantage, however, in this arrangement, that still comparatively many individual plastic parts are required to provide the equipped with coils magnetic core.

Another important aspect of manufacturing magnetic cores in which the winding is wound directly onto the teeth of the core is the guidance of the coil wire during winding. There are different approaches to perform this winding as efficiently as possible. For example, the shows US 6,685,127 B2 a method for winding a rotor for a rotating field machine, in which a belonging to the winding machine hook is used to guide the wire and to avoid that the winding nozzle in their orientation in space, ie from the vertical to the horizontal, must be moved ,

However, there is still the need to fix bobbin to the teeth of a magnetic core in a way that they can be easily and inexpensively mounted, but ensure a safe and long-term stable seat in operation, and moreover a particularly efficient and accurate winding enable.

This object is solved by the subject matter of the independent patent claims. Advantageous developments of the present invention are the subject of the dependent claims.

Here, the present invention is based on the idea to form the winding body with a partially open cross section, so that the bobbin in a direction transverse to a longitudinal axis of the tooth is pushed onto the tooth and is fixed in interaction with the tooth at this. In this way, on the one hand, only a single plastic part is needed for the bobbin and on the other hand a particularly efficient, easily automatable assembly is possible.

The inventors of the present invention have recognized that the substantially saddle-shaped configuration of the bobbin sufficient for sufficient guidance, security and insulation of the coil winding and that no completely closed cross-section is required. In a particularly simple manner, the bobbin is fixed to the magnetic core in that a snap hook or a crushing rib is provided on the receptacle of the bobbin, in which the tooth is received, via which the bobbin is firmly fixed to the tooth. In contrast to known solutions, only one half-shell is therefore provided in the solution according to the invention instead of the usual two-part molding.

Alternatively or additionally, a fixing device may also be provided, which is arranged in a region of the bobbin oriented toward the yoke of the magnetic core and cooperates with a holding structure of the magnetic core in order to fix the bobbin. This may be, for example, hooks which are inserted into corresponding openings on the magnetic core. Such compounds may, for example, according to the principles of DE 10 2010 004 887 A1 be designed.

Another aspect of the present invention is the provision of a specially designed guide member for guiding the coil wire during the winding operation.

In particular, the guide element has a guide slope, which extends from an end region of the guide element to a base region of the guide element arranged on the coil body. In particular, the guide element is designed such that the base region has a smaller cross-sectional dimension than the front region. This can be achieved by a truncated pyramidal configuration of the guide element, wherein the base of the truncated pyramid is located at the end portion and has a polygonal, circular or ellipsoidal shape. However, the guide element can also have the shape of an oblique prism or a skewed cylinder, ie in the base region have a cross-section offset with respect to the end region in the direction of the desired wire position, wherein the end region but has a similar surface dimension as the base region.

It is crucial in any case that by train on the wire this experiences a force component in the direction of the base region and is thus automatically brought into the correct position.

According to an advantageous embodiment of the present invention may also be provided to pretreat the wound wire so that it can be bonded after winding, and thus eliminates the usual Vergussschritte. For example, the wire may be provided with a corresponding coating which is melted after being wound by hot air in an oven or by heating by a current flow through the wire. In this way, the production of the Coil body according to the invention and the associated magnetic cores and sensor systems are further simplified.

For a better understanding of the present invention, this will be explained in more detail with reference to the embodiments illustrated in the following figures. The same parts are provided with the same reference numerals and the same component names. Furthermore, individual features or combinations of features from the embodiments shown and described can in themselves represent independent inventive or inventive solutions.

Show it:

1 a perspective view of a fully assembled magnetic core according to the present invention;

2 a detail from 1 ;

3 a perspective view of a bobbin during assembly on the magnetic core;

4 a detail from 3 ;

5 another detail 3 ;

6 a magnetic core before winding;

7 a magnetic core after winding;

8th the magnetic core 6 in a view rotated by 180 °;

9 a side view of the magnetic core 1 ,

Hereinafter, with reference to the figures advantageous embodiments of the present invention will be explained in more detail. It should be noted that, although it will be assumed below always of a magnetic core, which can be used as a stator in a reluctance resolver, the present invention is of course applicable to any type of rotating electrical machines. This means that the type of fixing bobbins according to the invention can also be used for motors and generators, both at stator cores and at rotor cores.

Furthermore, the present invention is not limited to embodiments in which the teeth of the magnetic core protrude from an annular Jochrücken in the direction of the central axis inwardly, but in a similar analogy arranged on the outer periphery of a core magnetic core teeth can be appropriately equipped with the bobbins of the invention.

Finally, the bobbins according to the invention can be combined not only with laminated magnetic cores, but also with those which are made in one piece.

1 shows a perspective view of a magnetic core according to the invention 118 ,

In the embodiment shown, the magnetic core 118 a total of sixteen teeth 116 on, as for example, to realize 16-pole stator for a 6-speed resolver according to the DE 10 2009 061 032 A is proposed. The individual teeth 116 are over a yoke back 132 connected with each other. In the transition area between yoke backs 132 and tooth 116 is on both sides of the tooth 116 a holding opening 120 provided, in which a corresponding projection 114 engages the bobbin, so that the bobbin 100 firmly on the tooth 116 is fixed.

According to the present invention, each spool is 100 shaped so that it is in a direction transverse to the longitudinal axis of the tooth 116 is slidable before the winding 110 is attached. The mounting direction is in 1 with the arrow 122 marked.

According to a specific embodiment, in 1 is shown, the individual bobbin 100 together to form an integral bobbin array 140 connected, according to the shape of the magnetic core 118 is substantially annular. Thus, all 16 bobbin 100 essentially simultaneously on the magnetic core 118 to be assembled. However, the principles of the present invention are not necessarily limited to this annular configuration of a bobbin array.

As will be more apparent from the following drawings, each of the bobbins 100 designed so that it directly with the magnetic core, especially with the teeth 116 cooperates to fix the bobbin thereto. There are therefore no further parts for fixing the bobbin longer required and the actual assembly of the insulator is with a pressing in the direction 122 completed. For example, on an inner surface of the winding body 102 Crimp ribs or locking devices for securing the bobbin 100 be provided.

According to a further aspect of the present invention, each bobbin has by way of example two guide elements 134 , the wire during the winding process 111 when changing to the next coil so that the winding wire nozzle of a winding device does not have to be moved out of its horizontal position. The guide projections have a tapered cross-section towards the coil, so that by applying tensile forces to the wire 111 this automatically along the guide slope down towards the magnetic core 118 is pulled. The substantially truncated pyramidal guide elements 134 can besides the in 1 of course also have an elliptical, circular or otherwise polygonal base surface shown square base.

The guide element 134 but may, as already mentioned and not shown in the figures, also have the shape of an oblique prism or a skewed cylinder, ie in the base region with respect to the forehead area in the direction of the desired wire position offset cross-section, the forehead area but a similar Area dimension has the same as the base area. In any case, it is crucial that by pulling on the wire 111 this experiences a force component in the direction of the base region and is thus automatically brought into the correct position.

The arrangement of the windings can, for example, according to the principles of DE 10 2009 061 032 A1 take place by the order of the windings is carried out so that first all windings are wound in one direction (ie, for example Pol 16, Pol 2, Pol 4, etc. to pole 14 clockwise and then the poles 13, 11, 9 to pole 15th counterclockwise). In this way it can be ensured that not a single large circle is wound with the diameter of the stator, but first a large circle in one direction and then a second circle is wound in the opposite direction. For a sensor system, winding a single giant single-turn coil would mean that in this winding, the magnetic field passing through the resolver would disturb the resolver's signal. In the arrangement according to the invention, the disturbing effects average out in an advantageous manner.

In the 1 shown embodiment also has the advantage that the wiring directly through the coil wires 111 is formed so that no additional Printed Circuit Board (PCB) is required. This simplifies the production and reduces the height on the other hand.

2 shows a detail 1 , from which in particular the operation of the guide elements 134 becomes clear. How out 2 it can be seen form the guide elements 134 guide slopes 126 out, along which the wire 111 when winding in the direction of the magnetic core 118 is pulled. By providing appropriate feed channels 108 In addition, it can be ensured that the wires in a defined manner to the individual coil bobbins 100 back and away again. The magnetic core 118 is, as is well known, from individual slats 136 composed.

As already mentioned, the individual bobbins 100 each represent individual plastic parts. In this case would be in place 128 be a parting line. Alternatively, however, the entire ring of bobbins as a single array 140 of coherent bobbins 100 getting produced.

The 3 to 5 illustrate an exemplary embodiment of the bobbin according to the invention 100 during mounting on the magnetic core 118 , It is in the 3 and 4 recognizable that locking projections 114 as a holding element on the tooth 116 of the magnetic core 118 are provided. Alternatively, however, crushing ribs or, in general, an interference fit can also be provided. Further shows 5 that ever the bobbin 100 two retaining projections 114 has, in corresponding openings 120 on the magnetic core 118 be introduced to allow secure mounting and positioning. The retaining projections 114 are doing by pressing in the openings 120 fixed and the design of the magnetic core 118 with its openings 120 is done according to the principles of DE 10 2010 004 887 A1 ,

In particular, on the magnetic core 118 in the openings 120 Holding structures provided with the retaining projections 114 on the bobbin 100 interact. For example, this holding structure may be formed by two hook-shaped projections, which in the retaining projection 114 intervention.

Since the distance between the opposing support structures of the magnetic core must be relatively narrow in order to reliably grip the plastic retaining projection, a comparatively expensive punching tool must be provided, if both projections in each individual lamination 136 would like to provide.

In contrast, as in the DE 10 2010 004 887 A1 explained, provided to each lamella in such a way that in a first and a third quadrant, the projections are oriented in one direction and in a second and fourth quadrant in the opposite direction. By laminating the sheets with a radial angle offset of 90 ° between two superimposed sheets can mechanically realize a closely spaced support structure, without having to comply with these narrow structure widths in the punching of a single lamination sheet. In order to enable a simple automation of the laminating process, the individual laminations designed according to the invention can be displaced radially from position to position always in the same direction, ie clockwise or counterclockwise.

Furthermore, the individual teeth of the magnetic core can each with pole pieces 138 be provided. These pole pieces, which are appropriately widened designed end portions of the tooth 116 may be formed in the inventive arrangement serve two different important purposes:

On the one hand, the magnetic flux which flows directly from pole to pole directly without being passed through the rotor can be reduced by such shaping. Particularly when used in resolvers, any proportion of magnetic flux that does not pass through the air gap leads to a reduction in the signal strength and thus the accuracy of the resolver. For motors or generators, it is necessary for reasons of the drive torque or the efficiency that the magnetic flux takes the path through the air gap and the rotor.

On the other hand, such a configuration with a pole shoe can also be used mechanically for fastening the bobbin. For this purpose, it is advantageous that the coil body tapers in the cross section of its inner wall in such a way that the coil body comes into pressing contact with the pole piece of the magnetic core only in its fully mounted position. In order to reduce the forces that occur when plugging, also only a small area ratio of the recording of the bobbin should come into contact with the pole piece of the magnetic core. For this purpose, further crush ribs may be provided on the inner wall of the bobbin.

As already mentioned are the plastic pins, which are the guide elements 134 form, shaped so that the wire guide does not have to be pivoted during the winding to move from one coil to the next. The wire guide can always remain horizontally aligned and the guide slope 126 ensures that the wire automatically finds its desired end position. During manufacture, the wire guide moves only over the pins, then is moved between the bobbins and centered, and then the winding starts. In order to prevent disturbances during the winding also, as already mentioned, supply channels for the wire are provided, in which the wire is arranged in order not to hinder the layer stratification when winding the coil.

In this way, a disorderly winding is prevented or at least reduced and therefore more windings can be accommodated in a tighter space. In addition, the accuracy of the sensor is improved during operation, since in disordered winding angle errors are greater.

If the wire guide device does not need to be tilted, the entire winding process is faster and simpler devices can be used for the winding.

As well as out 5 can be seen, is below the guide element 134 arranged a recess, which is why in the injection mold for this molding no slide must be provided and therefore the production is simplified.

6 shows the magnetic core 118 with the bobbins mounted on it 100 before the coil windings are attached.

7 shows in a plan view of the arrangement of 1 , Wherein the individual poles for the definition of the winding arrangement are designated by the reference symbols P1 to P16. The individual outward guided contact pins 112 are provided with the names C1 to C6 and in Table 1 below, an exemplary winding scheme is given. CW is a clockwise winding and CCW is a counterclockwise winding. Table 1: Winding diagram, connections and winding device winding scheme prime Sin cos C4 direction turns C2 direction turns C6 direction turns P16 CW 47 P3 CW 78 P4 CW 78 P2 CW 47 P7 CW 78 P8 CW 78 P4 CW 47 P11 CW 78 P12 CW 78 P6 CW 47 P15 CW 78 P16 CW 78 P8 CW 47 P13 CW 78 P14 CCW 78 P10 CW 47 P9 CCW 78 P10 CCW 78 P12 CW 47 P5 CCW 78 P6 CCW 78 P14 CW 47 P1 CCW 78 P2 CCW 78 P13 CCW 47 C1 C5 P11 CCW 47 P9 CCW 47 P7 CCW 47 P5 CCW 47 P3 CCW 47 P1 CCW 47 P15 CCW 47 C3

A rotated by 180 ° arrangement is from the 8th seen. Here it also becomes clear that each of the teeth 116 a pole piece 138 having.

The 9 Finally, a side view of the fully assembled resolver 146 from the 1 , As can be seen from this view, all wire connections 111 guided in the plastic of the bobbin. They therefore do not come with the metal of the magnetic core 118 in touch.

The production of a resolver stator according to the present invention will be described in detail below with reference to all 1 to 9 be explained. It is assumed by way of example that all bobbins 100 to a bobbin array 140 connected to each other. For the production of the magnetic core is first 118 from a variety of layered lamellae 136 built up. Subsequently, the bobbin array 140 as a ring over all teeth 116 of the magnetic core 118 pushed. The fixation and adjustment takes place on the one hand on the holding elements 114 and on the other via the locking elements 130 ,

In the next step, the bobbins are wound, with the wire 111 on the guide elements 134 as described above. According to an advantageous embodiment, a so-called baked enamel wire is used for winding, which has, for example, a base coat of polyurethane and a Layered baked enamel of polyvinyl butyral. After winding, the wire can be heated by appropriate surges or by annealing in an oven to safely bake the windings together. Alternatively, a polyamide can be used as a baked enamel.

In this way, the often used encapsulation of the windings can be avoided in a separate step. In addition, the caked together wire layers are arranged much less space.

In summary, the arrangement according to the invention offers, inter alia, the following advantages both for use in reluctance resolvers and in electric motors or generators:
The bobbins can be attached to a magnetic core in a particularly secure manner. This gives a much better resistance to environmental influences such as vibration and temperature jumps. Furthermore, the bobbin is centered much better on the stator, so that the electrical properties of the electrical machine are improved because all coils occupy the same position.

The production of the magnetic core equipped with coils is much faster and largely automated, with the number of items to be supplied is reduced.

The height of the overall arrangement can be significantly reduced. LIST OF REFERENCE NUMBERS numeral description 100 bobbins 102 winding body 104 first flange 106 second flange 108 Feed channel for wire 110 winding 111 wiring 112 Contact pin to the outside 114 Holding projection, holding element 116 Tooth (pole) 118 magnetic core 120 holding opening 122 mounting direction 124 admission 126 guide slope 128 parting line 130 catch projection 132 Jochrücken 134 guide element 136 lamella 138 pole 140 Bobbins Array 146 resolver 148 Recess below the guide element

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 patent literature

• US 5,300,884 [0005]
• DE 102009061032 A1 [0005, 0041]
• DE 102010004887 A1 [0006, 0015, 0045, 0048]
• US 7385323 B2 [0008, 0008]
• US 6685127 B2 [0010]
• DE 102009061032 A [0035]

Claims (19)

Spool for mounting on a magnetic core ( 118 ), wherein the bobbin ( 100 ): a winding body ( 102 ), for applying a winding, wherein the winding body ( 102 ) a recording ( 124 ) for picking up a tooth ( 116 ) of the magnetic core ( 118 ), wherein the winding body ( 102 ) has a partially open cross-section, so that the bobbin ( 100 ) in a direction transverse to a longitudinal axis of the tooth ( 116 ) is pushed onto the tooth, and wherein the bobbin ( 100 ) is shaped so that it with the magnetic core ( 118 ) cooperates for fixing. Spool according to claim 1, wherein the receptacle ( 124 ) is dimensioned so that the bobbin ( 100 ) is fixed in the assembled state by means of a press fit on the tooth. Bobbin according to claim 1 or 2, wherein on the inner surface of the receptacle ( 124 ) at least one latching device ( 130 ) for locking with the tooth ( 116 ) is formed. Spool according to one of the preceding claims, further comprising a first ( 104 ) and a second flange ( 106 ), wherein at the first flange ( 104 ) at least one retaining element ( 114 ) is formed in cooperation with a holding opening ( 120 ) of the magnetic core ( 118 ) the bobbin ( 100 ) on the tooth ( 116 ) fixed. Spool according to one of the preceding claims, further comprising at least one guide element ( 134 ) for guiding a coil wire ( 111 ) during winding of the bobbin ( 100 ). Spool according to claim 5, wherein the guide element ( 134 ) at least one guide slope ( 126 ) which extends from an end region of the guide element to a base region of the guide element arranged on the coil body and is oriented such that the coil wire ( 111 ) is guided from the forehead area to the base area. Bobbin according to claim 5 or 6, wherein the bobbin ( 100 ) directly adjacent to the at least one guide element a recess ( 108 ) for receiving the coil wire. Spool for mounting on a magnetic core ( 118 ), wherein the bobbin ( 100 ): a winding body ( 102 ), for applying a winding, wherein the winding body ( 102 ) a recording ( 124 ) for picking up a tooth ( 116 ) of the magnetic core ( 118 ), a first ( 104 ) and a second flange ( 106 ), wherein at the first flange ( 104 ) at least one guide element ( 134 ) for guiding a coil wire ( 111 ) is arranged during the winding of the bobbin, and wherein the guide element ( 134 ) at least one guide slope ( 126 ) which extends from an end region of the guide element to a base region of the guide element arranged on the coil body and is oriented such that the coil wire ( 111 ) is guided from the forehead area to the base area. Spool according to claim 8, wherein the winding body has a partially open cross-section, so that the bobbin ( 100 ) in a direction transverse to a longitudinal axis of the tooth ( 116 ) is pushed onto the tooth. Bobbin according to claim 8 or 9, wherein the receptacle ( 124 ) is dimensioned so that the bobbin is fixed in the assembled state by means of a press fit on the tooth. Bobbin body according to one of claims 8 to 10, wherein on the inner surface of the receptacle at least one latching device ( 130 ) for locking with the tooth ( 116 ) is formed. Bobbin according to one of claims 8 to 11, wherein on the first flange ( 104 ) at least one retaining element ( 114 ) is formed in cooperation with a support structure ( 120 ) of the magnetic core ( 118 ) fixes the bobbin to the tooth. Bobbin body according to one of claims 8 to 12, wherein the bobbin directly adjacent to the at least one guide element has a recess ( 108 ) for receiving the coil wire ( 111 ) having. Bobbin array ( 140 ) comprising a plurality of bobbins ( 100 ) according to one of the preceding claims, wherein the bobbins ( 100 ) are connected together so that they are substantially simultaneously on the teeth ( 116 ) of the magnetic core ( 118 ) are mountable. Bobbin body array according to claim 14, which is produced in one piece as a molded part. Magnetoelectronic angle sensor with an at least partially ferromagnetic stator ( 118 ) and an at least partially ferromagnetic rotor facing each other to form an annular air gap, wherein the magnetic resistance in the air gap periodically changes due to circumferentially varying formation of the rotor as the rotor rotates about an axis of rotation with one on the rotor Stator ( 118 ) arranged on at least one pair of poles a predetermined magnetic flux distribution in the air gap, with one on the stator ( 118 ) arranged magnetic flux receiver which measures the intensity of the magnetic field via at least two mutually offset at an angle Signalpolpaare, wherein from the two receiver signals an angle value for the relative position of the rotor relative to the stator ( 118 ) is derivable, wherein the stator ( 118 ) is formed by a magnetic core and the magnetic flux transmitter and the magnetic flux receiver windings on bobbins ( 100 ) according to one of claims 1 to 13 or a bobbin array according to one of claims 14 or 15 are arranged. Method for producing a magneto-electronic angle sensor comprising the following steps: Providing a magnetic core having circumferentially distributed a plurality of teeth separated by grooves; Providing a plurality of bobbins; Mounting the bobbins on the teeth of the magnetic core by sliding in a direction transverse to a longitudinal axis of the respective tooth, each bobbin having a winding body with a partially open cross-section Attaching windings from a coil wire to the assembled bobbins. The method of claim 17, wherein the coil wire is formed by a baked enamel wire. A method according to claim 18, wherein the enameled wire has a temperature-resistant base insulation and a covering layer which bonds by heating and preferably polymerises thereby.

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