Rotor for an outrunner motor

Abstract

A rotor for an external rotor motor is described, comprising a stack (1) of ferromagnetic steel sheets, permanent magnets (2) attached to an inner surface of the stack (1), and a support (3) having a hub for a shaft and attached to the stack (1). According to the invention, the support is connected to the stack (1) by a shaft-hub connection.

Description

[0001] The invention relates to a rotor for an electric motor having the features specified in the preamble of claim 1.

[0002] In such a rotor for an external rotor motor, a lamination stack forming a short-circuit ring must be connected to a support having a hub for a shaft. The object of the present invention is to demonstrate a way to achieve this cost-effectively while ensuring reliable torque transmission from the lamination stack to the support.

[0003] This object is achieved by a rotor having the features recited in claim 1. Advantageous developments of the invention are the subject of subclaims.

[0004] According to the invention, the stack of laminations is connected to the carrier by means of a shaft-hub connection. The ferromagnetic steel laminations are preferably made of electrical steel, i.e., soft magnetic steel, for example, silicon steel.

[0005] An advantageous development of the invention provides that the sheets forming the stack of the short-circuit ring are welded together. In this way, the short-circuit ring, although consisting of individual sheets, is preassembled into a convenient assembly. However, the sheets can also be connected to each other in other ways, for example, by stamped stacking or with an interlock system. The individual sheets of the stack can be ring-shaped sheets or each form only one ring segment.

[0006] A further advantageous development of the invention provides that the sheets of the stack are connected by a plurality of weld seams that extend in the axial direction and are preferably arranged on the outside of the sheet stack. The magnetic properties of steel sheets are generally impaired by welding. In the region of the weld seam, where the material has been melted, the microstructure is typically adversely changed. It is therefore advantageous if the volume of the weld seams in the sheet stack is relatively small and thus the magnetic properties of the sheet stack are only slightly impaired. For example, the weld seams can be provided in projections on the outside of the sheet stack, in particular completely provided in projections on the outside of the sheet stack.Such projections may extend in the axial direction on the outside of the lamination stack and contribute to the shaft-hub connection of the lamination stack to the carrier.

[0007] A further advantageous development of the invention provides that the shaft-hub connection of the sheet stack to the carrier is made by means of projections of the sheet stack, which extend in the axial direction on an outer side of the sheet stack and engage in slots of the carrier.

[0008] A further advantageous development of the invention provides that the carrier carries a plurality of holders on its outer side, which connect the lamination stack to the carrier. The holders can grip around the lamination stack at one end and around an edge of the carrier at their other end, thus preventing axial movement of the lamination stack relative to the carrier. The holders can be arranged, for example, on projections of the lamination stack that extend in the axial direction. The holders can be welded to the lamination stack. This can advantageously increase the stability of the rotor.

[0009] A further advantageous development of the invention provides that the support surrounds the lamination stack only over a portion of the axial length of the lamination stack. Since the steel sheets of the stack are welded together, it is sufficient to transmit torque from the lamination stack to the support if the shaft-hub connection is made over a portion of the axial length of the lamination stack. This advantageously reduces the mass of the rotor and thus improves the efficiency of the motor. Good results can be achieved, for example, if the support surrounds the lamination stack over 20% to 50% of the length of the lamination stack.

[0010] A further advantageous development of the invention provides that the carrier has pairs of projections extending in the axial direction on the outside of the laminated core stack, between which the slots are formed. In this way, the mass of the rotor can be advantageously reduced and thus the efficiency of the motor increased. Preferably, the projections have a raised portion on their edge facing the slot, thus extending further in the radial direction at this edge, which advantageously improves the mechanical stability for torque transmission from the stack to the carrier.

[0011] The number and width of the pairs of projections can be freely selected within wide limits. For example, a reliable shaft-hub connection can be realized with a carrier having 3 to 6 pairs of projections. In one embodiment of the invention, the distance between adjacent pairs of projections is at least twice the slot width and can, for example, be five to ten times the slot width. In this way, the mass of the carrier can advantageously be kept low while still achieving a reliable shaft-hub connection between the carrier and the lamination stack.

[0012] A further advantageous development of the invention provides that the laminated core stack has grooves on its inner side that extend in the axial direction and in which the permanent magnets are arranged. The permanent magnets can thus advantageously stabilize the laminated core stack. The permanent magnets can, for example, be glued into the grooves. Projections on the outer side of the laminated core stack can, for example, be arranged opposite the grooves and thus compensate for the locally reduced radial thickness of the laminated core stack caused by the groove. However, it is not necessary for a projection to be located opposite each groove.

[0013] Further details and advantages of the invention are explained using an exemplary embodiment with reference to the accompanying drawings. They show: Fig. 1 a rotor for an external rotor motor, and Fig. 2 a schematic representation of the shaft-hub connection between sheet stack and carrier.

[0014] The Fig. The rotor shown in Figure 1 has a stack 1 of ferromagnetic steel sheets, permanent magnets 2 attached to an inner side of the stack 1, and a support 3 made of non-ferromagnetic material, which is attached to the stack 1 and has a hub for a shaft (not shown). The support 3 can be made, for example, of aluminum or an aluminum-based alloy. The steel sheets of the stack 1 are made of electro-beam, i.e., soft magnetic steel, for example, silicon steel, and are stacked one upon the other in the axial direction. The sheet plane of the individual sheets thus extends perpendicular to the axial direction.

[0015] The stack 1 carries holders 4 on its outer side, which encompass both ends and preferably also the support 3. These holders 4 can be welded to the stack. In the illustrated embodiment, weld seams (not shown) run through the lamination stack, thus connecting all individual laminations of the short-circuit ring 1 to one another. However, the laminations of the lamination stack can also be mechanically connected to one another in other ways, for example, by an interlock system or by means of stamped stacking.

[0016] In the example shown, stack 1 carries four fixtures 4, and the sheets of stack 1 are welded together by four welds 5. The number of fixtures 4 and welds 5 can be varied. Good results are generally achieved with three to six fixtures 4 and welds 5. More fixtures increase the manufacturing effort; fewer fixtures make handling stack 1 more difficult.

[0017] In the illustrated embodiment, the holders 4 are arranged on projections 6 of the stack 1, which extend axially along the outer side of the sheet stack. Advantageously, the magnetic properties of the sheets are only negligibly affected by the welding, especially if the weld seams 5 extend only within the projections 6 within the stack 1.

[0018] The projections 6 on the outside of the stack 1 are also used for a shaft-hub connection of the stack 1 with the carrier 3. This shaft-hub connection is Fig. 2 illustrates. Fig. Figure 2 shows schematically in a sectional view a detail of the stack 1 together with the rotor carrier 3. The projections 6 of the short-circuit ring 1, which in Fig. 2 are shown without holders for the sake of simplicity, engage in slots of the carrier 3 and thus enable a transmission of torque from the stack 1 to the carrier 3. The slots of the carrier 3 are formed between projections 8 of the carrier 3, which extend in the axial direction on the outside of the stack 1. The slots are thus formed by pairs of projections 8 of the carrier 3, which are in particular in Fig. 1 can be seen.

[0019] The projections 8 of the carrier 3 extend only over a part of the axial length of the stack 1, for example over 20% to 50% of the axial length of the stack 1. In this way, a corrugated hub connection between the stack 1 and the carrier 3 can be realized with little material expenditure and advantageously low weight.

[0020] The projections 8 of the carrier 3 have a raised portion 9 at their edge adjacent to the projections of the stack, thus extending further in the radial direction at this edge. The raised portions 9 are a thickening of the projections 8 and increase the mechanical stability for torque transmission.

[0021] There is a significant gap between adjacent pairs of projections 8 of the carrier 3 to save material. In the example shown, the gap is more than twice the slot width and amounts to five to ten times the slot width.

[0022] How Fig. As shown in Figure 2, each of the projections 6 of the stack 1 is arranged opposite one of the permanent magnets 2. The permanent magnets 2 are glued into grooves in the inside of the stack 1. However, not every permanent magnet 2 is opposite a projection of the stack 1. As Fig.1 shows, it has more permanent magnet 2 than projections 6 of the stack 1. List of reference symbols 1 stack 2 permanent magnets 3 carriers 4 brackets 5 welds 6 projections of the stack 8 projections of the carrier 9 Survey

Claims

[1] Rotor for an external rotor motor, with a stack (1) of ferromagnetic steel sheets, permanent magnets (2) attached to an inner side of the stack (1), and a carrier (3) having a hub for a shaft and being attached to the stack (1), characterized by , that the carrier (3) is connected to the stack (1) by a shaft-hub connection. [2] Rotor according to claim 1, characterized by that the sheets of the stack (1) are welded together. [3] Rotor according to claim 2, characterized by that the sheets of the stack (1) are welded to one another by a plurality of weld seams (5) extending in the axial direction on the outside of the stack (1). [4] Rotor according to one of the preceding claims, characterized by that the stack (1) has on its outer side projections (6) extending in the axial direction, which engage in slots of the carrier (3). [5] Rotor according to claim 3 and 4, characterized by that the weld seams (5) run in the projections (6). [6] Rotor according to one of the preceding claims, characterized by that the stack (1) carries on its outside brackets (4) which connect the stack (1) to the carrier (3). [7] Rotor according to one of the preceding claims, characterized by that the carrier (3) surrounds the stack (1) only over part of the axial length of the stack (1). [8] Rotor according to claim 7, characterized by that the carrier (3) surrounds the stack (1) for 20% to 50% of the length of the stack (1). [9] Rotor according to one of claims 4 to 8, characterized by that the carrier (3) has pairs of projections (8) extending in axial directions on the outside of the stack (1), between which the slots are formed. [10] Rotor according to claim 9, characterized bythat the distance between adjacent pairs of projections (8) of the carrier (3) is at least twice as large as the slot width, preferably five to ten times the slot width. [11] Rotor according to claim 9 or 10, characterized by that the projections (8) of the carrier (3) have a raised portion (9) on their edge facing the slot. [12] Rotor according to one of claims 3 to 11, characterized by that one of the permanent magnets (2) is arranged opposite each of the projections (6) of the stack (1). [13] Rotor according to one of the preceding claims, characterized by that only every second of the permanent magnets (2) on the outside of the stack (1) is opposite a projection (6) of the stack (1).

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