Rotor for an external rotor motor

Abstract

Rotor for an external rotor motor, with a ring-shaped stack (1) of steel sheets welded together, and permanent magnets (2) attached to an inner side of the stack (1), a carrier (4) having a hub (5) for a shaft, characterized by Clamps (3) that grip around a radially outer edge of the support (4) and press the support (4) axially against the stack (1), wherein the stack (1) has pressure surfaces (6) between its axial ends against which an end of the clamps (3) facing away from the hub (5) presses.

Description

[0001] The invention relates to a rotor for an external rotor motor, comprising an annular stack of steel laminations, permanent magnets attached to an inner surface of the laminations, and a support having a hub for a shaft and attached to the laminations. Such a rotor is known from DE 10 2010 051 264 A1.

[0002] From WO 2019 / 105 751 A1, an internal rotor motor is known whose stator has a stack of steel sheets and clamp bands that encircle the stator on its outer circumference in the axial direction and press it together.

[0003] From DE 10 2019 202 563 A1 a rotor with a multi-part rotor carrier and a laminated core is known, which is attached to the rotor carrier by shrinking and a radial positive locking connection.

[0004] The object of the present invention is to show a way in which the support of a rotor for an external rotor motor can be attached to the stack of sheet metal in a cost-effective manner.

[0005] This problem is solved by a rotor having the features specified in claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

[0006] In a rotor according to the invention, the stack of welded steel sheets is pressed axially against the support by clamps that bear against an outer surface of the stack. According to the invention, the stack has pressure surfaces between its axial ends, against which an end of the clamps facing away from the support presses. Advantageously, clamps can therefore be used that are significantly shorter than the axial length of the sheet stack. The clamps of a rotor according to the invention are thus cost-effective and allow for simple manufacturing. Each clamp of a rotor according to the invention can be manufactured cost-effectively as a stamped and bent sheet metal part.

[0007] The pressure surfaces of the sheet stack, against which the clamps press, are preferably formed by radial projections of the sheet stack, but can also be formed by recesses and depressions on the outside of the sheet stack.

[0008] An advantageous embodiment of the invention provides that the stack of sheets is constructed from sheets of the same shape. For example, the ring-shaped sheets can have radial projections, for example 3 to 6 projections, on their outer circumference. When a group of such sheets, for example 4 to 6 sheets, are stacked on top of each other in the same angular orientation, a small stack of sheets is formed with radial projections that each extend in a straight line along its outer surface in the axial direction. A second stack consisting of a second group of sheets can then be placed on top of this small stack. These second stacks are all offset from the sheets of the first group by a predetermined angular angle. Although all sheets of the stack thus formed are identical, a stack can be created that has pressure surfaces at the boundary between the first and second groups, against which the clamps can be applied.

[0009] A further advantageous embodiment of the invention provides that the pressure surfaces are formed by axial end faces of radial projections of the sheet metal stack. Preferably, these projections are undercut on their axially extending side faces, and the clamps engage in these undercuts. Such an undercut can, for example, be designed as an axially extending groove in a side face of a projection. In this way, unintentional release of the clamps can be made more difficult.

[0010] Further details and advantages of the invention are explained using an exemplary embodiment of the invention with reference to the accompanying drawings. These show: Fig. 1 an embodiment of a rotor according to the invention; Fig. 2 a view of the rotor's sheet metal stack; Fig. 3 a detailed view of the rotor; Fig. 4 a cutaway detail view of the rotor; Fig. 5 another cutaway detail view of the rotor; and Fig. 6 a view of a rotor clamp;

[0011] In Fig. Figure 1 shows the rotor of an electric motor, more precisely an external rotor motor. The rotor has an annular stack of laminations 1 made of ferromagnetic steel, for example, electrical steel sheet or other soft magnetic steel sheet. The individual laminations of the stack 1 can be annular or each form only a ring segment. Permanent magnets 2, for example based on Nd₂Fe, are attached to the inside of the stack 1. 14B. The permanent magnets 2 can, for example, be arranged in grooves of the sheet metal stack 1 and fixed there, for instance, by means of adhesive. The sheet metal stack 1 is attached to a support 4, which has a hub 5 for a shaft, by clamps 3. The clamps 3 grip around a radially outer edge of the support 4 and press the support 4 axially against the stack 1.

[0012] In Fig. Figure 2 shows the sheet metal stack 1 of the rotor. The sheets of stack 1 are welded together. Between its axial ends, the sheet metal stack 1 has radial projections 9 on its outer surface, which form pressure surfaces 6 against which an end of the clamps 3 facing away from the hub 5 presses.

[0013] Fig. Figure 3 shows a detailed view of the rotor. Fig. 4 a cutaway detail view of the rotor, with the cutting plane running along the edge of a bracket 3. Fig. Figure 5 shows another cutaway detail view of the rotor, with the cutting plane passing through the middle of one of the brackets 3. Fig. 6 shows one of the brackets 3.

[0014] The pressure surfaces 6 are formed as axial surfaces of radial projections 9 of the sheet stack 1. As in particular Fig. As shown in Figure 4, these projections 9 have undercuts on their axially extending side surfaces. In other words, the projections 9 have an undercut 11 or a recess in their side surfaces, for example, an axially extending groove. The clamps 3 engage in this undercut 11. This makes it more difficult for the clamps 3 to loosen unintentionally, especially due to radial forces. Alternatively or additionally, the clamps 3 can also be bonded to the sheet stack 1, for example, by welding or bonding.

[0015] The projections 9, which form the pressure surfaces 6, can extend laterally from ribs 8 that run straight in the axial direction. As in particular Fig. As shown in Figure 2, the stack of sheets 1 has several ribs 8 on its outer surface, extending over the entire length of the stack. The pressure surfaces 6 extend circumferentially from both sides of some of these ribs 8, in the example shown from every second rib 8. The clamps 3 have a slot 10 at their end section, which presses against the pressure surfaces 6, through which the rib 8 passes.

[0016] In the illustrated embodiment, the stack of sheets 1 is constructed from steel sheets that are identical within their manufacturing tolerances. These ring-shaped steel sheets each have equidistant projections around their outer circumference, for example, 4 to 10 projections. In the illustrated example, half of the projections have the width of the ribs 8, and the other half have an increased width, namely the width of the pressure surfaces 6.

[0017] To construct the sheet stack 1, the steel sheets are stacked on top of each other in groups, with the sheets within each group lying in the same angular orientation and adjacent groups being rotated relative to each other by an angle of rotation, in the example shown by 45°. The projections 9 of the adjacent groups are thus offset from each other, so that the pressure surfaces 6 at the boundary between a first and a second group are accessible for the clamps 3. The ribs 8 facilitate the correct arrangement of the groups relative to each other. A group can consist of, for example, 4 to 25 sheets.

[0018] How in particular Fig.As shown in Figure 5, the edge of the carrier 4, around which the clamps 3 grip, can project axially. Radially inward from its projecting edge, the carrier 4 then has an axial recess 12 into which the respective clamp 3 engages. To further improve the adhesion of the clamps 3, a spring tab 13 can be cut out of an end section of the clamps 3, for example, with a U-shaped cut line. The spring tab 13 is pushed inward, i.e., toward the carrier 4, from the end section. The free end of the spring tab 13 faces the axially projecting edge of the carrier 4. The spring tab 13 thus forms a hook that prevents the clamp 3 from detaching.

[0019] To assemble the rotor, the stack of sheet metal 1 is inserted into the support 4. The support 4 then rests against the outside of the stack 1 and has axially extending slots in which the ribs 8 and the projections 9 of the stack of sheet metal 1 are arranged. To facilitate the insertion of the stack of sheet metal 1 into the support 4, these slots in the support 4 can narrow towards the hub 5. Reference symbol list 1 stack of metal sheets 2 permanent magnets 3 bracket 4 carriers 5 hub 6 pressure surface 8th rib 9 lead 10 slots 11 Undercut 12 axial recesses 13 spring tab

Claims

Rotor for an external rotor motor, comprising an annular stack (1) of steel sheets welded together, and permanent magnets (2) attached to an inside of the stack (1), a carrier (4) having a hub (5) for a shaft, characterized by clamps (3) which engage around a radially outer edge of the carrier (4) and press the carrier (4) axially against the stack (1), the stack (1) having pressure surfaces (6) between its axial ends against which an end of the clamps (3) facing away from the hub (5) presses. Rotor according to claim 1, characterized in that the pressure surfaces (6) are surfaces of radial projections (9) of the stack (1). Rotor according to claim 2, characterized in that the projections (9) have an undercut (11) in their axially extending side surfaces and the clamps (3) engage in this undercut (11). Rotor according to claim 2 or 3, characterized in that the carrier (4) abuts the outside of the stack (1) and has axially extending slots in which the projections (9) of the stack (1) are arranged. Rotor according to one of the preceding claims, characterized in that the stack (1) is composed of identically formed steel sheets, wherein a first group of sheets successive in the stacking direction is offset by an angle of rotation relative to a second group of sheets successive in the stacking direction, and thus the pressure surfaces (6) are formed at the boundary between these two groups. Rotor according to one of the preceding claims, characterized in that the carrier (4) has an axial recess (12) in the axial direction at its radially outer edge around which the clamps (3) reach and the clamps (3) engage in this axial recess (12). Rotor according to claim 6, characterized in that a spring tab is cut out from an end section of the clamps (3), the free end of which faces the radially outer edge of the carrier (4). Rotor according to one of the preceding claims, characterized in that the stack (1) has ribs (8) extending in a straight line in the axial direction on a radial outer surface and the pressure surfaces (6) extend circumferentially from this rib (8). Rotor according to claim 8, characterized in that the clamps (3) have a slot (10) in their end which presses against the pressure surfaces (6), through which one of the ribs (8) passes. Rotor according to one of the preceding claims, characterized in that the clamps (3) are materially bonded to the stack (1).

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