Rotor of an electric machine with cord bandage

Abstract

Rotor (1) of an electrical machine, with lamination packs (8) in which a plurality of slots (9) are formed in the longitudinal direction, each having slot constrictions (18) on an outer circumferential side (17) of the rotor (1), with a machine winding (7) having winding heads (10) and with a cord bandage (14) formed by a cord (11), which is inserted in the slots (9) and covers the winding heads (10) with a net-like braid (12), characterized in that at least one end (21) of the cord (11) is forced into a gusset space (19) of the slot (9) formed between the machine winding (7) and the slot constriction (18) by a filling element (20) made of a paper material, which is introduced into one of the slots (9), for fixing, wherein the gusset space (19) between the machine winding (7) and the slot constrictions (18) is designed in such a way thatthat the material of the lamination packs (8) spreads roof-like over areas of the machine winding (7) and the cord (11) and the filling element (20) are pushed below the groove constriction (18) into the gussets (19) on the left and right sides of the groove constriction (18).

Description

[0001] The invention relates to a rotor of an electric machine with laminated cores in which several grooves are formed longitudinally, each with groove constrictions on an outer circumferential side of the rotor, comprising winding heads and a cord bandage formed by a cord which is inserted in the grooves and covers the winding heads with a net-like mesh. The invention further relates to a method directed towards the manufacture of the cord bandage. State of the art

[0002] It is known to apply a bandage to sections of the rotor of electric machines for abrasion protection in certain applications. A polyester cord is frequently used as the bandage, which is bonded at the beginning and end by melting under heat. It is also known to produce bandages from yarn, but the beginning and end of the cord must be knotted. Such careful knotting cannot be automated, so in the prior art, the rotors must be removed from the production line and the knots made manually. This requires considerable logistical effort and time, and in unfavorable cases, the quality of the knots is inconsistent.

[0003] DE 103 00 796 A1 and EP 0 579 953 A1 each disclose a rotor of an electric machine with slots narrowed on the input side, into which a machine winding with end winding heads is inserted. Furthermore, a cord bandage extending over the winding heads and running in the slots, formed by a cord, is provided, wherein at least one end of the cord is pressed into a gusset formed between the machine winding and the slot narrowing by a filling element inserted into one of the slots for fixation.

[0004] Comparable cord bandages for rotors of electrical machines are also described in EP 0 536 162 B1, EP 1 422 335 A2 and US 5 352 948 A.

[0005] The object of the invention is to manufacture a fully automatic cord bandage in order to minimize material costs and improve the process, in which the cord can be fixed without manual intervention. Disclosure of the invention

[0006] To solve the problem, it is provided that at least one end of the cord is forced into a gusset formed between the winding and the narrowing of the groove by a paper-based filling element inserted into one of the grooves. This gusset is designed such that the material of the lamination stacks spreads roof-like over areas of the winding, and the cord and the filling element are forced into the gussets to the left and right of the narrowing. The cord is therefore not secured by knotting, welding, or heat-induced bonding (melting of the cord material), but rather by being forced into the gusset formed between the winding and the narrowing of the groove.This insertion into the gusset is achieved by the filling element, which applies force to at least one end of the cord, thus forcing it into the gusset. By inserting the cord into the gusset, the filling element prevents the end of the cord from slipping out of its intended position, thus preventing the cord bandage from loosening during operation. The wedging of the cord end in the gusset by the filling element eliminates the need for knotting or gluing. A particular advantage of this is that the error-prone process of knotting, especially manual knotting, is eliminated. Furthermore, it is unnecessary to subject the rotor to heat (as is common practice in the prior art for gluing polyester cord) or to introduce an additional chemical, namely the adhesive.

[0007] In a preferred embodiment, the filling element is a paper cord, in particular a paper cord flattened by deformation. The paper material is formed into a cord whose dimensions are altered by flattening to create a filling element resembling a so-called paper wedge, although the design need not be wedge-shaped in the strict sense; the decisive factor is the flattening of the paper cord to form a more planar than round cross-section.

[0008] Preferably, the flattened paper cord has a greater width than the width of the groove's opening. This makes it possible to wedge the flattened paper cord in the groove in a self-locking manner. It engages under the groove's narrowing and, at least partially, enters the space between the machine winding and the groove's narrowing, thus securing the cord inserted there.

[0009] In another preferred embodiment, the filler element is shorter than the length of the groove. To adequately secure the end of the cord in the groove, it is not necessary for the filler element to extend over the entire length of the groove. It is sufficient for the filler element to be inserted in a region of the groove at the end of which the end of the cord is located. This advantageously avoids an unnecessary increase in the rotor's mass, particularly an eccentric increase in the rotor's mass.

[0010] In a further embodiment, the cord has a beginning and an end, and during the creation of the cord bandage, the beginning is wrapped for fastening, while the end is secured by means of the filling element. The ends of the cord forming the cord bandage are thus distinguished as a beginning and an end, with the beginning being the end of the cord processed at the start of the bandage production, and the end being the end that is to be secured at the end of the bandage production. The beginning of the cord is therefore not secured by a filling element or a similar aid, or, for example, by gluing, but rather by wrapping. This corresponds, for example, to the handling of a knot and is based on the fact that frictional forces are built up between individual parts of the rotor and between cord sections in such a way that the cord holds itself in a self-locking manner.When inserting the cord, specifically the cord end, into the grooves, it is wound from one groove to another over a winding head. This quickly creates a structure of overlapping cord sections, which prevents the cord from slipping out of the groove due to the applied frictional forces (because the cord is inserted under tension, not loosely). Therefore, there is no need for a separate securing of the cord end with a filler element or adhesive.

[0011] Furthermore, a method is proposed for securing the end of a cord bandage formed by a cord on the rotor of an electric machine. In this method, the end of the cord is inserted into a groove in the rotor, and a filler element is placed into a narrowing of the groove such that the end is forced into a space formed between a machine winding and the narrowing of the groove, thus securing it. This method allows the use of a simple cord (twine), which can be particularly advantageously impregnated with resin after its insertion, or which, when the rotor is impregnated with resin, as is known from the prior art, fills itself particularly advantageously with resin, resulting in a particularly stable and durable bond.

[0012] Further advantageous embodiments result from the dependent claims and from combinations thereof.

[0013] The invention will be explained in more detail below using an exemplary embodiment, without being limited to this.

[0014] They show Fig. 1 a rotor of an electric machine, Fig. 2 a cross-sectional view of a section of this rotor, Fig. 3. The insertion of a filler element formed from a paper cord into a groove to secure the filler element and Fig. 4. The rotor in its finished state after the filling element has been inserted.

[0015] Fig. Figure 1 shows a rotor 1 for installation in an electric machine (not shown). The rotor 1 is mounted on a rotor shaft 2 and has a fan 4 at a first rotor end 3 for conveying cooling air, and a commutator 6 at a second rotor end 5. The commutator 6 is electrically connected to a machine winding 7 mounted on the rotor 1 for supplying it with electrical energy, in a manner known from the prior art. The rotor has slots 9 in lamination stacks 8, into which the machine winding 7 is inserted. Conductors made of copper wire forming the winding 7 are guided in the slots in a coil-like manner, forming winding heads 10, to generate magnetic field lines, in a manner known from the prior art.After the machine winding 7 is applied, a cord 11 is inserted, starting in a groove 9, and guided over the winding heads 10 in such a way that it covers the winding heads 10 with a net-like braid 12. For this purpose, the cord 11 is guided from a groove 9 over a winding head 10 at the first rotor end 3 and then back in another groove 9 to the second rotor end 5 and the winding head 10 there, until a braid 12, as shown here by way of example, has formed. The cord 11 thus forms a compact bandage 13, namely a cord bandage 14, on the rotor 1, in particular over the winding heads 10, by means of the braid 12.The winding heads 10 are thus very well protected against abrasive particles, such as those carried in a cooling air stream 15, since when the rotor 1 rotates during operation of the electric machine (not shown), the particles carried in the cooling air stream 15, such as dust particles, are deflected at the highest points of the winding heads 10 formed by the braid 12 and do not reach the sensitive winding heads 10. This provides very good abrasion protection for the winding heads 10. At the same time, good mechanical fixation of the machine winding 7, especially the winding heads 10, is achieved, which can be further increased by impregnating the cord 11 or even the machine winding 7 or the entire rotor 1 with a resin 16.

[0016] Fig. Figure 2 shows a section-by-section cross-section through the described rotor 1, with lamination stacks 8 in which slots 9 are formed longitudinally. The slots 9 have a narrowing 18 on their upper side, i.e., on an outer circumferential side 17 of the rotor 1, a reduction in the clear width w of the slot 9 through which the machine winding 7 is inserted. A space 19 is formed between the machine winding 7 and the narrowing 9, specifically in such a region that the material of the lamination stacks 8 spreads over parts of the machine winding 7 in a roof-like manner to form the narrowing 18. The cord 11 is inserted into this space 19 in such a way that it is held clamped in the space 19 between the lamination stack 8 and the machine winding 7.To secure the cord 11 by clamping it, a filler element 20 is inserted into the groove 9 such that, below the groove constriction 18 and in contact with the machine winding 7, it is pressed into the gusset spaces 19 to the left and right of the groove constriction 18. This holds the cord 11 firmly in the gusset space 19, preventing it from coming loose. This ensures a very secure hold and reliable fixation of the cord 11 in the gusset space 19 and thus on the rotor 1. An additional knotting of the cord 11 after applying the [missing information] is not required. Fig. Bandage 13 shown is not required.

[0017] Fig. Figure 3 shows the rotor 1 with the lamella packs 8 in sections. The cord 11 is inserted into these packs to form the bandage 13 over the winding heads 10. After the bandage 13 is complete, one end 21 of the cord 11 is held taut, and the filler element 20 is inserted into the groove 9. The end 21 of the cord 11 emerges from the groove after the bandage 13 is complete. The filler element 20 is formed from a paper cord 22 and is therefore made of a paper material 23. The paper cord 22 is designed as a flattened paper cord 24, meaning its width is significantly greater than its thickness. This allows it to be inserted into the groove constrictions 18 for expansion under the lamella packs 8 in the intersecting spaces 19. There, it becomes taut due to its material properties and its tendency to expand to assume its original shape. In this process, the cord 11 is advantageously wedged in the gusset space 19 by pushing it in.

[0018] Fig. Figure 4 shows the rotor 1 in its finished state, with the filler element 20, which is shorter than the length of the groove 9 into which it is inserted, fully inserted and, if necessary, trimmed to length. Here, after the application of the bandage 13 by winding the cord 11 over the winding heads 10 and securing the end 21 of the cord 11 with the filler element 20, which is designed as a paper cord 22, the rotor 1 is impregnated with resin 16, namely an insulating synthetic resin 25. The cord 11 and the filler element 20 each absorb a considerable amount of resin 16 and thereby form a solid, very dimensionally stable bond after the resin 16 has dried and hardened. The rotor 1 is thus mechanically very well fixed, particularly in the area of ​​its winding heads 10, and the bandage 13 provides excellent protection against particles (dust, etc.) introduced, for example, by a cooling system.

Claims

[1] Rotor (1) of an electric machine, with laminated stacks (8) in which several slots (9) are formed in the longitudinal direction, each with slot constrictions (18) on an outer circumferential side (17) of the rotor (1), with a machine winding (7) having winding heads (10) and with a cord bandage (14) formed by a cord (11), which is inserted in the slots (9) and covers the winding heads (10) with a net-like mesh (12), characterized by, that at least one end (21) of the cord (11) is pressed into a gusset space (19) of the groove (9) formed between the machine winding (7) and the groove constriction (18) by a filling element (20) made of a paper material inserted into one of the grooves (9), wherein the gusset space (19) between the machine winding (7) and the groove constrictions (18) is designed such that the material of the lamella packs (8) spreads roof-like over areas of the machine winding (7) and the cord (11) and the filling element (20) are pressed into the gusset spaces (19) to the left and right of the groove constriction (18) below the groove constriction (18). [2] Rotor according to claim 1, characterized by , that the filling element (20) is a paper cord (22), in particular a paper cord (24) flattened by deformation. [3] Rotor according to claim 2, characterized by, that the flattened paper cord (22, 24) has a greater width than the width of the groove narrowing (18) of the groove (9). [4] Rotor according to any one of the preceding claims, characterized by , that the filler element (20) is shorter than the length of the groove (9). [5] Method for fastening the end (21) of a cord bandage (12) formed by a cord (11) of a rotor (1) of an electric machine according to one of the preceding claims, wherein the end (21) of the cord (11) is inserted into a groove (9) of the rotor (1) and a filling element (20) is inserted into a groove constriction (18) of the groove (9) such that the end (21) is forced into a gusset space (19) formed between a machine winding (7) and the groove constriction (18) and is thus fixed.

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