Rotor and method for producing a rotor

Abstract

A rotor (10) for an electric machine is provided, in particular for an electric excited synchronous motor, the rotor (10) comprising a rotor core (12) with a plurality of rotor teeth (14) extending from the rotor core (12) in a radial direction and a plurality of windings (16) each wound around one of the rotor teeth (14). The rotor (10) comprises at least one support element (20) which is at least in part formed from a stabilization material (22) which in the initial state is absorbent and compressible, the stabilization material being in contact with the windings (16) in such a way that it is compressed by the windings (16). The windings (16) and the stabilization material (22) are impregnated with resin at least in the area where the stabilization material (22) contacts the respective winding (16). Furthermore, a method for producing a rotor (10) for an electric machine is provided.

Description

[0001] Rotor and method for producing a rotor

[0002] The invention refers to a rotor for an electric machine, in particular for an electric excited synchronous motor, and to a method for producing a rotor for an electric machine.

[0003] Electric machines are generally known. An electric machine with an electric excited synchronous motor comprises a rotor which has at least one current-carrying inductance through which the corresponding magnetic field is generated. The inductance is realized by at least one winding with several turns.

[0004] When the motor is running, in particular at high speeds, centrifugal forces act on the windings in such a way that the individual wires of the windings tend to move relative to each other. Such a movement however is unwanted because due to this movement, the windings are likely to be damaged.

[0005] In order to avoid a movement of the individual wires of the windings, it is a known solution to mechanically fix the windings, in particular by means of a resin impregnation or by gluing the wires together, such that the wires are fixed in place. However, this solution does not reliably prevent the wires from moving at high rotational speed.

[0006] To further improve the fixation of the windings, the rotor can be fully potted. Consequently, the rotational speed of the rotor can be increased without causing a movement of the windings. However, this solution is disadvantageous regarding the weight of the rotor. Also, the heat dissipation from the rotor is impaired since the potting material has the same effect as an insulator.

[0007] It is thus an object of the present invention to provide an improved rotor for an electric machine that allows a high rotational speed of the rotor while a movement of the windings is avoided.

[0008] This object is achieved by a rotor for an electric machine, in particular for an electric excited synchronous motor, the rotor comprising a rotor core with a plurality of rotor teeth extending from the rotor core in a radial direction and a plurality of windings each wound around one of the rotor teeth. The rotor comprises at least one support element which is at least in part formed from a stabilization material which in the initial state is absorbent and compressible, the stabilization material being in contact with the windings in such a way that it is compressed by the windings. The windings and the stabilization material are impregnated with resin at least in the area where the stabilization material contacts the respective winding.

[0009] When the stabilization material is impregnated, it becomes stiff, such that the windings are sufficiently supported and held in place by means of the at least one support element.

[0010] Due to the stabilization material being compressible in the initial state, the shape of the stabilization material adapts to the form of the windings. Thereby, tolerances of the windings can be compensated.

[0011] When the stabilization material has absorbed the resin and the resin is cured, it has the same effect as a full potting of the rotor and thus reliably keeps the windings in place.

[0012] However, the stabilization material does not come with the disadvantages of the full potting, because it allows a better heat dissipation than a full potting and the weight of the rotor is less than with a full potting.

[0013] Preferably, the support element has a carrier and the stabilization material is attached to the carrier. The carrier is in particular a stiff element. Thus, the carrier ensures that the support element has a sufficient stability to enable easy handling and attachment to the rotor. Without the carrier, the stabilization material would be easily bendable, which could impede the attachment of the stabilization material to the rotor. Also, the amount of stabilization material needed can be reduced. However, depending on the location where the support element is to be attached, it is thinkable that the support element is fully made from stabilization material.

[0014] The stabilization material is for example prefabricated in the form of pads.

[0015] According to one embodiment, the at least one support element is arranged between a pair of windings and the stabilization material is in contact with the windings along the longitudinal sides of the windings. In this way, the windings are supported in such a way that the windings are restricted from moving towards the radially outermost end of the rotor teeth.

[0016] For example, the at least one support element has a wedge-like cross section and extends along an axial direction of the rotor. Thereby, a gap that is present between two windings in a circumferential direction of the rotor is occupied by the support element. In other words, by means of the wedge-like support element being arranged in the gap, there is no free space to which the windings could move.

[0017] The stabilizing material can be a strip-like element attached to the support element on opposite sides thereof, such that the stabilization material is specifically arranged in the area where the support element contacts the winding. In other words, an area of the support element that is not in contact with the windings is free of stabilization material, which is advantageous regarding the production costs of the rotor.

[0018] According to one embodiment, the support element is an end cap that is attached to the axial ends of the rotor and the stabilization material is in contact with the winding head of at least one winding. Thereby, it is ensured that the winding heads are not lifted up from the rotor or shifted with respect to the rotor.

[0019] The end cap for example comprises a mounting ring centered on a rotor shaft and a support ring mechanically supporting the winding head at least indirectly, the end cap further having webs extending in a radial direction, the stabilization material being attached to the webs. Due to the webs, the end cab has a particularly high stability. Also, between the webs, the end cap has openings through which the rotor is accessible for cooling fluid.

[0020] The end cap is preferably produced as a single piece.

[0021] The width of the stabilization material in a peripheral direction attached to one web can be smaller than the width of the winding head. Thereby, it is ensured that cooling fluid can contact the winding heads at least in the lateral area.

[0022] The end cap may have a circumferential collar at the outer support ring that is aligned at an end plate arranged at the rotor core. The collar provides an additional alignment of the end cap.

[0023] The stabilization material is for example a material with open pores, a textile, a foam or a fleece. Such materials are capable of absorbing resin and it is thus possible to stiffen the initially flexible material. Moreover, such materials allow sufficient heat dissipation. Also, depending on the size of the pores, it is possible that cooling fluid can permeate the stiffened stabilization material and reach the windings.

[0024] In one exemplary embodiment, the stabilization material is made from Nomex®.

[0025] The stabilization material may be attached to the support element by means of glue or adhesive tape. Thereby, the stabilization material can be attached to the carrier particularly easy. The attachment of the stabilization material to the support element does not have to be permanently, but only has to ensure that the support element with the stabilization material can be mounted in the wanted position. After the stabilization material is impregnated with resin, the stabilization material is fixed in place by means of the hardened resin.

[0026] In an exemplary embodiment, the windings are orthocyclic. Thereby, the winding can be particularly compact. Moreover, an orthocyclic winding is self-stabilizing and thus contributes to holding the windings in a fixes position.

[0027] The object is further achieved by a method for producing a rotor for an electric machine, in particular an inventive rotor as described above. The method comprises the step of providing a rotor core with a plurality of rotor teeth extending from the rotor core in a radial direction and a plurality of windings that are wound around the rotor teeth. In a further method step, at least one support element having a compressible, absorbent stabilization material is provided. The support element is attached to the rotor core, thereby bringing the stabilization material in contact with the windings such that the stabilization material is compressed by the windings. Afterwards, the stabilization material and the windings are impregnated with resin and the resin is cured. Thereby a compound of the stabilization material and the wires of the winding is formed.

[0028] As already described with respect to the rotor, the support element provides a sufficient stabilization for the windings while at the same time allowing a good heat dissipation.

[0029] Further features and advantages of the invention can be derived from the following description and from the enclosed drawings. In the drawings:

[0030] Figure 1 shows an inventive rotor, Figure 2 shows a support element for the rotor according to Figure 1 in a front view,

[0031] Figure 3 shows a front view of the support element according to Figure 1 in contact with the windings of the rotor,

[0032] Figure 4 shows a further embodiment of an inventive rotor,

[0033] Figure 5 shows a cross section of the rotor of Figure 4,

[0034] Figure 6 shows a front view of a rotor core and a support element,

[0035] Figure 7 shows a cross section of a further inventive rotor, and

[0036] Figure 8 shows a cross section of another inventive rotor.

[0037] Figure 1 shows a rotor 10 for an electric machine, in particular for an electric excited synchronous motor, in a partially exploded view.

[0038] The rotor 10 comprises a rotor core 12 with a plurality of rotor teeth 14 extending from the rotor core 12 in a radial direction. At their free end, the rotor teeth 14 have a widened section 15. For example, the rotor core 12 is a stack of laminations.

[0039] The rotor core 12 is mounted on a rotor shaft 17.

[0040] The rotor 10 further comprises a plurality of windings 16 each wound around one of the rotor teeth 14. In Figure 1 , the windings 16 are depicted in a simplified manner.

[0041] Between the windings 16, a circumferential gap 18 is present, respectively. According to a conventional embodiment, these gaps 18 can be filled with resin in order to keep the windings 16 in a fixed position.

[0042] However, this results in a high weight of the rotor 10 as well as in an impeded heat dissipation.

[0043] Therefore, the a rotor 10 according to a first embodiment comprises several support elements 20 that are inserted into the gaps 18 in order to fix the windings 16. In other words, each support element 20 is arranged between a pair of windings 16 and the stabilization material 22 is in contact with the windings 16 along the longitudinal sides of the windings 16. In Figure 1 , only one support element 20 is depicted for reasons of simplicity, however, a support element 20 is provided for each gap 18.

[0044] The support element 20 shown in Figures 1 to 3 has a wedge-like cross section and extends along an axial direction of the rotor 10. Thus, the cross section of the support element 20 is adapted to the shape of the gaps 18.

[0045] In the embodiment according to Figure 1 , the support element 20 extends along the full length of the rotor core 12. However, it is also possible that the support element 20 is split in two parts that are inserted into the rotor 10 from opposite sides.

[0046] The support element 20 is at least in part formed from a stabilization material 22. The stabilization material 22 is absorbent and compressible in an initial state. For example, the stabilization material 22 is a material with open pores, a textile, a foam or a fleece.

[0047] In the depicted embodiment, the support element 20 comprises a carrier 24 to which the stabilization material 22 is attached, for example by gluing or an adhesive tape.

[0048] The carrier 24 is for example an extruded profile.

[0049] At its center, the carrier 24 can have a continuous opening 25 for further weight reduction.

[0050] Preferably, the stabilization material 22 is prefabricated in form of stickers, which comprise a pad of stabilization material 22 with an adhesive tape applied to one side of the pad.

[0051] In the embodiment shown in Figures 1 to 3, the stabilization material 22 is a strip-like element attached to the support element 20 on opposite sides thereof.

[0052] When the support element 20 is inserted into the gaps 18, it is braced by the widened section 15 of the rotor teeth 14.

[0053] The stabilization material 22 is in contact with the windings 16 when the support element 20 is inserted into the gaps 18, in such a way that it is compressed by the windings 16, as it is visualized in Figure 3, which shows a support element 20 in contact with two windings 16. Figure 3 also shows that the windings 16 are arranged in an orthocyclic manner, which allows a compact and stable design of the windings 16.

[0054] After attaching the support element 20 to the rotor core 12 and bringing the stabilization material 22 in contact with the windings 16 such that the stabilization material 22 is compressed by the windings 16, the stabilization material 22 and the windings 16 are impregnated with resin and the resin is cured. Thereby a compound of the stabilization material 22 and the wires of the winding 16 is formed.

[0055] In particular, the windings 16 and the stabilization material 22 are impregnated with resin at least in the area where the stabilization material 22 contacts the respective winding 16.

[0056] The impregnation may be done by roll dipping or by applying resin with a nozzle.

[0057] Figures 4 to 6 show a further embodiment of a rotor 10 with a support element 20 that is an end cap 26 which is attached to an axial end of the rotor 10. For example, an end cap 26 is attached to each axial end of the rotor 10.

[0058] The rotor core 12 and the windings 16 are depicted in a simplified manner in Figure 4.

[0059] The end cap 26 is for example made of a non-conductive material with a high tensile strength.

[0060] The stabilization material 22 attached to the end cap 26 is in contact with the winding head 28 of at least one winding. In particular, the stabilization material 22 is compressed by the winding head 28.

[0061] As shown in Figure 4, the end cap 26 comprises a mounting ring 34 and a support ring 36 as well as webs 38 extending in a radial direction. The webs 38 connect the mounting ring 34 and the support ring 36. Thus, the end cap 26 has a wheel-like form.

[0062] The end cap 26 is centered on the rotor shaft 17 with its mounting ring 34 (see Figure 5).

[0063] The mounting ring 34, the support ring 36 and the webs 38 together form the carrier 24 for the stabilization material. The support ring 36 is mechanically supporting the winding head 28 at least indirectly as it is shown in the sectional view in Figure 5.

[0064] The end cap 26 further has a circumferential collar 40 at the outer support ring 36 that is aligned at an end plate 42 arranged at an axial end of the rotor core 12.

[0065] The end plate 42 has a collar 44 axially protruding away from the rotor core 12, wherein the circumferential collar 40 of the end cap 26 is aligned at the collar 44 of the end plate 42.

[0066] In case of the supporting element 20 being the end cap 26, the stabilization material 22 is attached to the webs 38.

[0067] Figure 6 shows a part of the rotor core 12 with a winding 16 and a part of the end cap 26 in a front view. From Figure 6 it is clear that the width of the webs 38 is smaller than the width of a winding head 28. Thus, as the stabilization material 22 does not protrude over the webs 38, the width of the stabilization material 22 in a peripheral direction attached to one web 38 is smaller than the width of the winding head 28.

[0068] In a preferred embodiment, the stabilization material 22 on the end cap 26 is present in addition to the support elements 20 arranged in the gaps 18. However, both solutions can be applied to a rotor 10 independently from each other.

[0069] In the embodiments according to Figures 1 to 6, the windings 16 have a rectangular cross section.

[0070] However, the windings 16 can have a different cross section, for example a trapezoidal cross section as depicted in Figure 7 or a polygonal cross section as shown in Figure 8.

Claims

Claims1 . A rotor (10) for an electric machine, in particular for an electric excited synchronous motor, the rotor (10) comprising a rotor core (12) with a plurality of rotor teeth (14) extending from the rotor core (12) in a radial direction and a plurality of windings (16) each wound around one of the rotor teeth (14), wherein the rotor (10) comprises at least one support element (20) which is at least in part formed from a stabilization material (22) which in the initial state is absorbent and compressible, the stabilization material being in contact with the windings (16) in such a way that it is compressed by the windings (16), wherein the windings (16) and the stabilization material (22) are impregnated with resin at least in the area where the stabilization material (22) contacts the respective winding (16).

2. The rotor (10) according to claim 1 , wherein the at least one support element (20) is arranged between a pair of windings (16) and the stabilization material (22) is in contact with the windings (16) along the longitudinal sides of the windings (16).

3. The rotor (10) according to claim 2, wherein the at least one support element (22) has a wedge-like cross section and extends along an axial direction of the rotor (10).

4. The rotor (10) according to any one of the preceding claims wherein the stabilizing material (22) is a strip-like element attached to the support element (20) on opposite sides thereof.

5. The rotor (10) according to claim 1 , wherein the support element (20) is an end cap (26) that is attached to the axial ends of the rotor (10) and the stabilization material (22) is in contact with the winding head (28) of at least one winding (16).

6. The rotor (10) according to claim 5, wherein the end cap (26) comprises a mounting ring (34) centered on a rotor shaft (17) and a support ring (36) mechanically supporting the winding head (28) at least indirectly, the end cap (26) further having webs (38) extending in a radial direction, the stabilization material (22) being attached to the webs (38).

7. The rotor (10) according to claim 6, wherein the width of the stabilization material (22) in a peripheral direction attached to one web (38) is smaller than the width of the winding head (28).

8. The rotor (10) according to any one of claims 5 to 7, wherein the end cap (26) has a circumferential collar (40) at the outer support ring (36) that is aligned at an end plate (42) arranged at the rotor core (12).

9. The rotor (10) according to any one of the preceding claims, wherein the stabilization material (22) is a material with open pores, a textile, a foam or a fleece.

10. The rotor (10) according to any one of the preceding claims, wherein the stabilization material (22) is attached to the support element (20) by means of glue or adhesive tape.

11. The rotor (10) according to any one of the preceding claims, wherein the windings (16) are orthocyclic.

12. A method for producing a rotor (10) for an electric machine, in particular a rotor (10) according to any one of the preceding claims, the method comprising the steps of:- providing a rotor core (12) with a plurality of rotor teeth (14) extending from the rotor core (12) in a radial direction and a plurality of windings (16) that are wound around the rotor teeth (14),- providing at least one support element (20) having a compressible, absorbent stabilization material (22),- attaching the support element (20) to the rotor core, thereby bringing the stabilization material (22) in contact with the windings (16) such that the stabilization material (22) is compressed by the windings (16),- impregnating the stabilization material (22) and the windings (16) with resin and curing the resin, thereby forming a compound of the stabilization material (22) and the wires of the winding (16).

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