Method for winding a rotor pole of an electric machine and compression tool

Abstract

The invention relates to a method for winding a rotor pole (7) for an electric machine, the method comprising a step of compressing the pole along a longitudinal axis (A1) of the rotor, followed by a step of winding a wire around the longitudinally compressed pole. A compression tool (10) is also provided. Figure for the abstract: Fig. 2

Description

Title of the invention: Method for winding a rotor pole of an electric machine and compression tool Technical field of the invention

[0001] The present invention relates generally to the field of electrical machines, and in particular to the realization of the wound rotor of such machines.

[0002] It relates more particularly to a method for winding a rotor pole of an electric machine and a compression tool for winding a rotor pole of an electric machine. State of the art

[0003] A radial flux rotor has a generally cylindrical structure extending around the rotor's axis of rotation. The rotor comprises a longitudinal body and a plurality of poles projecting radially from this body along its entire length. Each pole includes a base (the "radial extension portion") and a pole head that protrudes on either side of the radial extension portion.

[0004] A winding wire is wound around the radial extension portions, under the pole heads, to form windings.

[0005] During the winding process, that is, during the winding of a conductive wire around the radial extension portion of each salient pole, each winding turn (resulting in the formation of a loop) applies a longitudinal compressive force to the pole. Since the rotor body is conventionally formed from a stack of metal sheets (or plates) stacked along the longitudinal direction of the rotor, this compressive force results in a longitudinal compression of the metal sheets and therefore a reduction in the length of the salient pole. The greater the number of winding turns, the more the salient pole is compressed, and the greater the reduction in the length of the salient pole (up to a certain limit).

[0006] Thus, the first winding turns are made around a salient pole whose length will subsequently decrease under the compressive force of the following winding turns. Consequently, the turns are more relaxed the earlier they are wound in the process. This phenomenon makes it difficult to achieve a well-ordered winding (whose turns are equally taut and parallel), which is necessary to obtain a stable inter-pole spacing from one inter-pole spacing to the next. Presentation of the invention

[0007] In order to overcome the aforementioned drawbacks of the prior art, the present invention proposes a tool enabling ordered winding, in which Each winding is properly tensioned.

[0008] More particularly, the invention proposes a method for winding a rotor pole for an electric machine, the method comprising a step of compressing the pole, along a longitudinal axis of the rotor, and then a step of winding a wire around the longitudinally compressed pole.

[0009] Thus, thanks to the compression step prior to winding, the winding of the coil turns begins around a pole that is already compressed, and the pole length decreases less or not at all during winding. This prevents the formation of a coil with some turns that are completely stretched, or even partially stretched.

[0010] Other advantageous and non-limiting features of the process according to the invention, taken individually or in all technically possible combinations, are as follows: - the wire forming turns around the pole, the winding stage is carried out in such a way that each turn exerts a longitudinal compressive force on the pole, the pole being compressed at the compression stage by a compressive force at least equivalent to the compressive force exerted by twenty turns, and preferably twenty-eight turns. - the rotor comprising a central body, the pole having a pole head and a radial extension portion extending radially from the central body to the pole head, during the compression step, a compression tool is used, this tool having two clamping lugs and actuating means configured to translate the two clamping lugs towards each other, the compression step including a positioning step of the tool so that each clamping lug extends on either side while bearing against longitudinal ends of the pole, a step of actuating the actuating means so as to compress the pole between the two clamping lugs. - the actuation means are screwing means. - the actuation means comprising an orifice provided in each clamping lug, one of which is tapped and a screw engaged through the two orifices, the actuation step comprises a rotation of the screw in the orifices so that the clamping lugs slide towards each other. - the compression tool includes a translation guide establishing a sliding connection with the clamping lugs, the tool positioning step further including a placement of the translation guide against a distal surface of the pole head relative to the central body. - the screw having a threaded body screwed into the tapped hole of one of the clamping lugs and a screw head, the compression tool has a spring placed between the other of the clamping lugs and the screw head.

[0011] According to another aspect, a wound rotor pole compression tool is proposed, comprising a first clamping lug, a second clamping lug, actuation means configured to translate the clamping lugs towards each other, and a translation guide establishing a sliding connection with the clamping lugs.

[0012] Other advantageous and non-limiting features of the process according to the invention, taken individually or in all technically possible combinations, are as follows: - the translation guide surrounds at least partially the clamping lugs and the actuation means. - the actuation means includes a screw having a threaded body screwed into the tapped hole of one of the clamping lugs and a screw head, the tool having a spring placed between the other clamping lugs and the screw head.

[0013] According to another aspect, a rotor for an electric machine is proposed, comprising at least one wound pole including a pole around which are wound several turns of an electrically conductive wire, each turn having a minimum tension force of 20N.

[0014] Of course, the various features, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0015] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0016] On the attached drawings:

[0017] [Fig-1] is a schematic perspective view of a rotor wound according to a process according to the invention, and on which a tool according to the invention is engaged;

[0018] [Fig.2] is a cross-sectional view of the rotor and tool of [Fig. 1];

[0019] [Fig.3] illustrates the tension of each turn during the winding of a rotor pole according to a process of the prior art,

[0020] [Fig.4] illustrates the tension of each turn during the winding of one pole of the rotor of the [Fig.l].

[0021] The invention relates to the winding of the poles of a rotor 1 for an electric machine. This rotor 1 is designed to rotate relative to a stator, around an axis of rotation Al corresponding in practice to the longitudinal axis of this rotor 1.

[0022] In this description, any direction parallel to the axis of rotation Al of the rotor is considered to be a longitudinal direction. Any direction orthogonal to the axis of rotation Al of the rotor and passing through the axis of rotation Al of the rotor is considered here to be a radial direction. Any direction orthogonal to the rotor's axis of rotation Al and not passing through the rotor's axis of rotation Al is called circumferential or ortho-radial (a circumferential trajectory is therefore a circular trajectory). The same applies to directions relative to the axis of the compression tool shown below.

[0023] As shown in Figures 1 and 2, the wound rotor 1 here comprises a body 2 of overall cylindrical shape which extends around the axis of rotation Al between a first face 3 and a second face 4. The body 2 of the rotor 1 is here made up of a plurality of metal sheets (or plates) orthogonal to the axis of rotation Al and stacked in the longitudinal direction.

[0024] The rotor 1 further comprises a shaft 5 which extends through the body 2. The body 2 of the rotor 1 comprises a central portion 6 of generally cylindrical shape and a plurality of salient poles 7, here eight salient poles 7, which extend radially from the central portion 6 away from the axis of the rotor 1. The salient poles 7 extend longitudinally along the entire length of the body 2, that is to say, between the first face 3 and the second face 4. The salient poles 7 are regularly distributed around the axis of rotation AL

[0025] Each salient pole 7 has a base called "extension portion 8" which extends radially from the central body 6 to an associated pole head 9, which forms ortho-radial projections cantilevered on either side of the extension portion 8. Thus, the cross-section of each pole 7 has an overall mushroom shape, of which the extension portion 8 forms the stem and the pole head 9 the cap.

[0026] The method according to the invention relates to winding a coil around the extension portion 8 of each salient pole 7. The method comprises, for example, winding a plurality of parallel turns using an electrically conductive wire. Each turn is wound with a predetermined tension, for example, between 50 newtons and 150 newtons.

[0027] At their ends, the salient poles 7 have edges that would damage the conductor wire if it were wound directly around the pole. To avoid this drawback, each pole is provided, at each of the faces 3 and 4, with a winding head guide 21 which gives the ends of the poles non-zero radii of curvature.

[0028] In order to avoid longitudinal compression of the metal sheets - and therefore a reduction in the length of the body 2 - during winding, which would lead to a progressive decrease in the tension of each turn during winding, the process includes, prior to winding the turns around a salient pole 7, a step of longitudinal compression of the salient pole 7.

[0029] For example, compression is achieved by applying compressive forces on the first face 3 and the second face 4, orthogonally to these faces. The resistance to compressive forces depends on the rotor parameters (pole length, material, number of metal sheets, etc.) and the compressive force applied to the pole depends on the tension of each turn. For example, if it has been observed that at the end of a conventional winding process (without prior compression), a number N of turns are completely stretched, the compressive force to be applied to the salient pole 7 prior to winding will be chosen so as to be at least equal to the compressive force exerted by N turns. Here, the compressive force is chosen to be the compressive force exerted by twenty-eight turns.

[0030] In order to apply the desired compression force to the salient pole 7 during its winding, a compression tool 10 is proposed which is configured to be placed on the pole so as to apply the compression force prior to the winding step, and which remains there throughout the winding.

[0031] The compression tool comprises a first clamping lug 11 and a second clamping lug 12, each configured to be positioned at one end of the rotor. Each of these clamping lugs has a contact surface configured to make contact with one of the faces 3, 4 of the rotor. These contact surfaces extend orthogonally to the axis of rotation Al, and they are designed to bear against areas of the faces 3, 4 of the salient pole that extend orthogonally to this axis. These clamping lugs could have various shapes. Here, they are designed to bear against the heads 9 of the salient poles.

[0032] The tool 10 includes actuating means 13 configured to translate the first and second clamping lugs 11, 12 towards each other. Here, the actuating means 13 are screwing means. They include a tapped hole 14 provided in one of the clamping lugs 11, 12, here the first clamping lug 11, and a second smooth hole 15 provided in the other clamping lug 12, here the second clamping lug 12.

[0033] The actuation means 13 further comprise a screw 16, a threaded body 17 (or threaded rod) of which is screwed into the first orifice 14 and engaged in the second orifice 15, and a screw head 18 of which is placed against the clamping lug having the unthreaded orifice, here the second clamping lug 12. Thus, in this configuration, a rotation of the screw 16 causes the first clamping lug 11 and the second clamping lug 12 to slide towards each other along the screw 16. Here, the first orifice is through, but alternatively it could be through.

[0034] The screw head 18 could be placed against the second clamping lug 12. However, in the illustrated example, the screw head 18 is placed against the second clamping lug 12 by means of a compression spring 19 or a Belleville washer. This spring 19 is in practice housed in a cavity provided in the second clamping lug 12, and is compressed between the head of the screw 16 and the bottom of this cavity.

[0035] When the compression tool 10 is engaged on the protruding pole 7 and the clamping lugs 11, 12 exert a compressive force on the protruding pole 7, the spring 19 is compressed between the screw head 18 and the second clamping lug. Thus, even if, despite the prior compression of the pole, the tension in the coils causes a further reduction in the length of the protruding pole 7, the compression tool 10 remains held on the protruding pole 7.

[0036] The tool 10 preferably comprises a translation guide 20 establishing a sliding connection with the clamping lugs 11, 12, so as to ensure perfectly rectilinear translation of the clamping lugs 11, 12. The translation guide 20 also acts as a protective housing for the tool 10 and partially surrounds the clamping lugs 11, 12 and the actuation means 13. The translation guide 20 has a generally tubular shape, and the clamping lugs 11, 12 have a complementary shape so as to be partially engaged inside the translation guide 20, each at an opposite end of the translation guide 20. Each clamping lug, however, has an outer flange serving as a stop to prevent the two lugs from coming together at a predetermined distance.

[0037] The translation guide 20 has a contact surface of complementary shape to that of a distal face of the pole head 9 (relative to the central body 6), allowing, when said complementary face is placed against the distal face of the pole head, better holding of the tool on the salient pole 7.

[0038] Figure 3 illustrates the evolution of the tension in the first 75 turns during a The conventional winding process (without prior compression) and [Fig. 4] illustrate the evolution of the tension in the first 115 turns during the winding process described above. In these figures, the tension T is represented on the ordinate, and the number n of each turn (its position in the winding) is represented on the abscissa.

[0039] It is apparent from [Fig. 3] that the tension T of the turns decreases sharply during winding. For example, the first turn, wound with a tension T(l) of 100 newtons, is completely stretched by the time the twentieth turn is wound. During the winding of the 75th turn, the first 34 turns are completely stretched. Stretched turns do not extend in a generally straight line, and are therefore not parallel to the stretched turns.

[0040] It is apparent from [Fig. 4] that, despite the prior compression of the salient pole 7, the turns undergo distension. Indeed, the first turns apply sufficient additional compressive force to further compress the salient pole 7. Beyond the twentieth turn, the pole has reached its maximum compression and its length no longer varies. Nevertheless, at the end of the winding process, none of the wound coils do not end up completely stretched.

[0041] Since, at the end of the winding, the total compressive force exerted by the tensioned turns is greater than that exerted initially (i.e., before the pole was wound) by the compression tool 10, the latter exerts only a small compressive force on the pole at the end of the winding, sufficient to ensure that the tool remains in place on the pole. This force is, for example, exerted by the spring 19 alone.

[0042] For example, the tension T(l) of the first turn decreases gradually but reaches a plateau (20 newtons) as soon as the 20th turn is wound. At the end of the winding, none of the wound turns has a tension T lower than 20 newtons. This results in a winding in which all the turns are under tension, and therefore parallel.

[0043] At the end of the process according to the invention, the actuation means 13 are actuated so as to completely relax the spring 19 and the compression tool 10 is released from the salient pole 7. When the compression tool 10 is released, the compression force that it exerted on the salient pole 7 becomes zero, which causes a release of the stack of sheets constituting the salient pole 7 and therefore an increase in the tension of the wires.

[0044] The invention is not limited to the methods of implementation and embodiment described above in connection with figures 1 to 4.

[0045] In particular, the compression tool described above is especially suited to compressing a salient pole. However, the invention is not limited to this tool, and other embodiments could use different compression tools. For example, the compression tool may not include a translation guide, or may include different actuation means (e.g., a jack system, a motorized system, etc.).

[0046] The application of a compressive force on a single pole has been described. The invention obviously applies to all poles and, according to certain embodiments, all poles are compressed prior to winding. For example, a compression tool is engaged on each salient pole before the winding of the first salient pole.

[0047] Furthermore, in order to compress the pole, the compression tool described above establishes contact with each of the opposite faces of the rotor. Alternatively, the compression tool can establish contact with the winding head guides rather than directly with the opposite faces of the rotor, so that, during compression, the winding head guides are compressed between the pole and the corresponding clamping lug.

[0048] It may also be provided that at the beginning of the winding a compression force equal to that which the turns will exert at the end of the winding.

Claims

Claims

1. Method for winding a rotor pole (7) for an electrical machine, the method comprising: - a step of compressing the pole (7), along a longitudinal axis (Al) of the rotor, then - a step of winding a wire around the longitudinally compressed pole (7).

2. Method according to claim 1, in which, the wire forming turns around the pole (7), the winding step is carried out so that each turn exerts a longitudinal compression force on the pole (7), the pole being compressed in the compression step by a compression force at least equivalent to the compression force exerted by twenty turns, and preferably twenty-eight turns.

3. A method according to claim 1 or 2, wherein, the rotor (1) comprising a central body (6), the pole (7) comprising a pole head (9) and a radial extension portion (8) which extends radially from the central body (6) to the pole head (9), during the compression step, a compression tool (10) is used, this compression tool (10) comprising two clamping lugs (11, 12) and actuating means (13) configured to translate the two clamping lugs (11, 12) towards each other, the compression step comprising: - a step of positioning the compression tool (10) so that each clamping lug (11, 12) extends on either side and bears against longitudinal ends of the pole (7), - a step of actuating the actuating means (13) so as to compress the pole between the two clamping lugs (11, 12).

4. A method according to claim 3, wherein the actuating means (13) are screwing means.

5. Method according to claim 4, in which the actuating means (13) comprise an orifice (14, 15) formed in each clamping tab (11, 12) of which one (14) is threaded and a screw (16) engaged through the two orifices (11, 12), the actuating step comprises a rotation of the screw (16) in the orifices (14, 15) so that the clamping tabs (11, 12) slide towards each other.

6. A method according to any one of claims 3 to 5, wherein the compression tool (10) comprises a translation guide (20) sta- providing a sliding connection with the clamping tabs (11, 12), the step of positioning the compression tool (10) further comprising placing the translation guide (20) against a distal surface of the pole head relative to the central body (6).

7. Method according to any one of claims 1 to 5, in which, the screw (16) comprising a threaded body (17) screwed into the tapped hole (14) of a first (14) of the clamping lugs and a screw head (18), the compression tool (10) comprises a spring placed between the other of the clamping lugs and the screw head.

8. Wound rotor pole compression tool, comprising a first clamping lug (11), a second clamping lug (12), actuating means (13) configured to translate the clamping lugs (11, 12) towards each other, and a translation guide (20) establishing a sliding connection with the clamping lugs (11, 12).

9. Compression tool according to claim 8, wherein the translation guide (20) at least partially surrounds the clamping tabs (11, 12) and the actuating means (13).

10. Tool according to claim 8 or 9, in which the actuating means comprise a screw (16) comprising a threaded body (17) screwed into a tapped hole (14) of one (11) of the clamping lugs (11, 12) and a screw head (18), the compression tool (10) comprising a spring (19) placed between the other clamping lug (12) and the screw head (18).

11. Rotor for an electrical machine, comprising at least one wound pole comprising a pole (7) around which several turns of an electrically conductive wire are wound, each turn having a minimum tension force of 20N.

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