Method for producing a stator for an electric motor

Abstract

The present invention relates to a method for producing a stator for an electric motor with a yoke ring and a pole star ring with a plurality of stator teeth for the arrangement of windings, preferably winding packages, wherein the pole star ring can be received in the yoke ring, with the pole star ring being inserted into the yoke ring, wherein the stator teeth face the yoke ring, and with the pole star ring being expanded, as a result of which the stator teeth are pressed against the yoke ring. Furthermore, the invention relates to such a stator for an electric motor with a yoke ring and a pole star ring, which can be received in the yoke ring, with a plurality of stator teeth for the arrangement of windings and with an opening for the arrangement of a rotor, wherein the stator teeth of the pole star ring are connected to one another via expandable connecting pieces which are plastically deformed in the mounted state.

Description

[0001] Method for producing a stator for an electric motor

[0002] The present invention relates to a method for producing a stator for an electric motor, comprising a yoke ring and a cushion ring with a plurality of stator teeth for arranging windings, preferably winding packs, wherein the cushion ring is inserted into the yoke ring. Furthermore, the invention relates to such a stator for an electric motor, comprising a yoke ring and a cushion ring, which can be accommodated in the yoke ring, with a plurality of stator teeth for arranging windings, and with an opening for arranging a rotor.

[0003] A conventional electric motor has a stator, which forms a stationary motor component, and a rotor, which forms a rotating motor component. In an internal rotor, the stator is typically equipped with a stator yoke on which radially inward-projecting stator teeth are located. The stator teeth have pole pieces at the ends facing the rotor and are provided with windings that generate an electromagnetic field during operation. To form and amplify the electromagnetic field, the stator yoke and the stator teeth are typically made of a soft magnetic material, for example, in the form of laminated cores.

[0004] When manufacturing the stator yoke, it is impossible to apply the windings from the outside through the closed yoke ring, while from the inside the pole pieces make access to the stator teeth difficult. With a one-piece stator yoke, a complex winding process is therefore necessary to provide the stator teeth with the necessary windings. For the production of stators for an electric motor, it is therefore common to use a multi-part stator structure, with very different designs, for example stators composed of C-shaped segments, yoke rings for stators with the individual stator teeth to be attached to them, or two-part stators with a cushion ring and a cylindrical yoke ring. With these multi-part stator concepts, a winding can be easily applied directly to the stator teeth.

[0005] Both the cushion ring and the cylindrical yoke ring of a two-part stator are typically manufactured from several individual sheet metal elements arranged one above the other in the axial direction and joined together to form a sheet stack by stamping, bonding, welding, bonding, or other stacking processes. For example, in US 2002 / 0083572 A1, loosely packed stator laminations are aligned using an expanding mandrel and then secured in a motor housing by screwing. Windings are wound onto the freely accessible stator teeth of the cushion ring or pushed onto them as winding packs. Following the fitting of the windings to the externally accessible pole teeth, the cushion ring is joined by pressing or shrinking.During the press connection between the cushion ring and the yoke ring, manufacturing tolerances can lead to air gaps between the stator teeth and the yoke ring, resulting in magnetic losses in the stator, as well as deformation of the stator teeth and, consequently, to the rejection of the stator.

[0006] In the prior art two-part stators with a cushion ring and a yoke ring, the cushion ring is pressed axially into the yoke ring when the components are joined. Mechanical contact between the components during axial pressing can result in notches on the components and chips that negatively impact the operation of the electric motor. Furthermore, splitting can occur in the laminated cores of the cushion ring and yoke ring, causing the laminations to no longer lie flat against one another, leading to magnetic losses in the stator. Furthermore, precise contours and tight tolerances of the cushion ring and yoke ring are required during axial pressing to avoid air gaps between the stator teeth and the yoke ring and to ensure a consistent outer diameter of the yoke ring.

[0007] For example, DE 10 2015 000 769 A1 discloses a stator for an electric motor with a force- or friction-locked press connection between the stator teeth of a cushion ring and a yoke ring. The yoke ring is axially pressed onto the cushion ring, and a material-to-material connection is additionally created using a microencapsulated adhesive. DE 102016201 967 A1 describes a tangential press connection between the stator teeth of a cushion ring and a yoke ring for process-reliable stator production. The stator teeth are designed with a slot-shaped, resilient recess and are inserted into axial grooves of the yoke ring to achieve a press fit with the yoke ring using tangential forces.

[0008] It is therefore the object of the present invention to provide an improved method for producing a stator for an electric motor, which method simplifies the production and assembly of the cushion ring and yoke ring, while at the same time reducing waste and ensuring functionally reliable stator quality. The object underlying the invention is achieved in a method for producing a stator for an electric motor by providing a yoke ring and a cushion ring with a plurality of stator teeth for arranging windings, preferably winding packages, wherein the cushion ring can be received in the yoke ring, by inserting the cushion ring into the yoke ring, with the stator teeth facing the yoke ring, and by spreading the cushion ring, whereby the stator teeth are pressed against the yoke ring. This method enables a secure and chip-free arrangement of the cushion ring in the yoke ring.It is advisable to arrange windings on the stator teeth before inserting the cushion ring, whereby individual prefabricated winding packages can be pushed onto the stator teeth from the outside. To form the cushion ring, the individual stator teeth are connected to one another in the area of ​​the inner pole pieces, for example with plastically deformable elements, preferably with expandable connecting webs. When inserting the cushion ring into the yoke ring, the stator teeth are arranged in the yoke ring with little or no mechanical stress, so that neither notches nor chips nor splitting can occur in the laminated cores of the stator teeth or the yoke ring. The ends of the stator teeth facing away from the pole pieces then face the inner circumferential surface of the yoke ring in the radial direction.It is advisable to place the yoke ring in a thick-walled support ring before expanding the cushion ring located within it, so that the yoke ring is not expanded or deformed by the radial compression force during expansion. The radial force acting on the stator teeth presses the free ends of the stator teeth against the yoke ring, creating a press fit between the cushion ring and the yoke ring. The deformable elements between the stator teeth are stretched, extended, or bent as the cushion ring expands.

[0009] A favorable embodiment provides for the cushion ring to have an opening with an inner diameter for accommodating a rotor, and expanding the cushion ring expands the inner diameter of the opening. This centrally located opening of the cushion ring enables safe and easy radial force to expand the cushion ring, whereby the final inner diameter for accommodating the rotor in the fully assembled stator is only determined after the cushion ring has been expanded. For a fault-free and efficient electric motor, a uniform distance between the stator teeth or pole pieces and the rotor is necessary, which is why all stator teeth are pressed as evenly as possible onto the yoke ring.

[0010] In an advantageous process variant, one or more inwardly projecting connecting webs are provided in the spaces between the individual stator teeth to form the cushion ring. Pressing on the connecting webs straightens the connecting webs, thereby spreading the cushion ring. By applying a force to the connecting webs, they can be deformed or straightened. This widens the inner diameter of the opening in the cushion ring, pressing the stator teeth against the yoke ring. The deformation can occur plastically without heating, thus reducing the complexity of the production process. In addition, the permeability of the connecting webs is reduced, thus reducing unwanted magnetic flux via the connecting webs.

[0011] An advantageous embodiment provides that the yoke ring has several recesses on an inner circumferential surface for accommodating the stator teeth of the cushion ring. When the cushion ring is spread open, the stator teeth are pressed into the recesses. This enables permanent fixation of the ends of the stator teeth to the inner circumferential surface of the yoke ring by means of a tangential holding force. The recesses on the inner circumferential surface can be designed as axial grooves, with radially deeper grooves and small remaining gaps between the yoke ring and the stator teeth enabling less dispersion of the cogging torque between the individual teeth and the yoke ring. The provision of recesses and the pressing of the stator teeth into the recesses further allows for the precise positioning of the stator teeth in the stator and thus an increase in the efficiency of the electric motor.

[0012] A modification of the method provides that a spreading tool, preferably a spreading tool with a wedge-shaped spreading element, is inserted into the cushion ring in order to spread the cushion ring open. The spreading tool is preferably inserted into the cushion ring after the cushion ring has been inserted into the yoke ring. The use of a suitable spreading tool enables uniform spreading of the cushion ring and thus also a good and uniform connection of the plurality of stator teeth to the yoke ring. A practical embodiment provides that the spreading tool is inserted in the axial direction into the rotor opening of the cushion ring and expands there evenly in the radial direction in order to evenly spread the cushion ring open via the application of radial force. The wedge-shaped spreading element can comprise a conical cone which is inserted into an expandable conical cylinder.The deeper the conical cone is inserted into the conical cylinder, the more the outer circumference of the conical cylinder increases, with the cylindrical outer surface of the conical cylinder pressing against the cushion ring or the connecting webs of the cushion ring. Due to the cylindrical outer shape, the contact pressure is evenly distributed over the entire axial length of the stator. The contact pressure is applied at right angles to the rotation axis of the motor or rotor. In a special variant, the spreading tool has several radially movable struts, preferably one strut assigned to each stator tooth, with the struts being pressed radially outwards to spread the cushion ring. The radial force of the spreading tool is exerted directly on the individual stator tooth via the strut pressing centrally on the stator tooth.If a simultaneous and uniform radial force is applied to all stator teeth of the cushion ring, this results in a uniform contact pressure of all stator teeth against the yoke ring.

[0013] An alternative method variant provides that one or more inwardly projecting connecting webs are provided in the spaces between the individual stator teeth to form the cushion ring, and the spreading tool has a plurality of radially movable struts, preferably a strut assigned to each space between the individual stator teeth, wherein the struts are pressed radially outward in order to straighten the connecting webs and thereby spread the cushion ring. One or more connecting webs, preferably curved connecting webs, can be provided in the spaces between the individual stator teeth, wherein the radially movable struts of the spreading tool essentially bear against all connecting webs of a space and press them outward.When expanding the cushion ring, the struts of the expanding tool are positioned essentially centrally between the stator teeth to apply pressure as evenly as possible to the respective connecting webs. Bending the connecting webs or straightening the previously bent connecting webs reduces the magnetic conductivity of the connecting web material, as this material saturates more quickly after the bending process. Reducing the magnetic conductivity at the connecting webs of the individual stator teeth of the cushion ring is beneficial during operation of the electric motor, as the webs between the individual stator teeth create an undesirable magnetic short circuit.

[0014] In an advantageous process variant, the connecting webs are removed after the cushion ring has been spread open, particularly by cutting or vaporizing with a laser beam underwater. This prevents the magnetic short circuit between the stator teeth, enabling higher torque. Due to their proximity to the winding package, the removal of the connecting webs is only possible to a limited extent by punching or mechanical cutting.

[0015] A useful design provides for the spreading tool to have an axially movable working wedge, and the struts of the spreading tool to have wedge-shaped pressing surfaces. The conically widening working wedge, which can be moved axially toward the rotor opening, enables a uniform radial force to be applied to the stator teeth or the connecting webs of the cushion ring via the wedge-shaped pressing surfaces of the struts, so that the stator teeth are pressed evenly outward and against the yoke ring by the axially movable working wedge.

[0016] The present invention further relates to a stator for an electric motor having a yoke ring, preferably a cylindrical yoke ring, a cushion ring which can be received in the yoke ring and has a plurality of stator teeth and a rotor opening, as well as windings, preferably winding packages, which are arranged on the stator teeth. According to the invention, the stator teeth of the cushion ring are connected to one another via expandable connecting webs, wherein the connecting webs are plastically deformed in the assembled state compared to the original state of the stator and the stator teeth are pressed against the yoke ring compared to the original state. In the original or pre-assembled state, the stator is unassembled in individual parts which are not fastened to one another. This enables precise alignment and secure arrangement of the stator teeth on the yoke ring, wherein the stator teeth or the pole shoes have the same radius orhave the same distance from the rotor axis so that the most even air gap possible to the rotor can be guaranteed later in the electric motor. This not only improves the efficiency of the electric motor through the precise positioning of the stator teeth in the yoke ring, but also reduces production waste and the electric motor's susceptibility to defects by avoiding chips, deformations and splitting of the laminated cores during stator manufacture. The expandable connecting webs, in particular plastically deformable connecting webs, whose deformation is not or not fully reversible after a radial force is applied, between the individual stator teeth of a cushion ring enable quick and easy positioning of the cushion ring in the yoke ring before a radial force is applied and even spreading of the cushion ring and pressing of the stator teeth against the yoke ring due to the radial force application.This enables reliable, fast, and therefore cost-effective stator production with a permanent press fit of the stator teeth against the inner circumferential surface of the yoke ring. The connecting webs also enable a magnetic short circuit between the stator teeth, which can reduce existing torque ripple depending on the wiring, pole pairs, and number of teeth of the electric motor.

[0017] To ensure good magnetic conductivity of the stator, the cushion ring can be designed as a lamination stack comprising multiple stator laminations, with individual stator laminations being designed as lamination rings that extend over all stator teeth of the cushion ring and form expandable connecting webs between the stator teeth. This not only enables good magnetic conductivity of the stator teeth but also enables simple formation of the expandable connecting webs. The stator laminations can be designed as blank laminations or as punched lamination rings and can be connected to a lamination stack by punching, gluing, welding, bonding, or similar. At least three stator laminations of the cushion ring can be designed as lamination rings, with the lamination rings preferably being evenly distributed across the thickness of the lamination stack.For example, every fifth, tenth, or twentieth stator lamination in the lamination stack can be designed as a lamination ring to enable a correspondingly functionally reliable design of the cushion ring. Alternatively, all stator laminations in the lamination stack can be designed with a thin connecting web. This creates a closure of the stator toward the rotor opening after the cushion ring is spread open and the stator teeth are pressed against the yoke ring. All winding cavities between the closed cushion ring and the yoke ring can be cast without the need for additional internal sealing.

[0018] Advantageously, the expandable connecting webs can be designed as curved connecting webs, preferably with a radial bend. This allows for both the simple provision of sufficient stretchability to expand the cushion ring, as well as plastic deformability to ensure sufficient stability of the cushion ring when inserted into the yoke ring and, after expansion, the pressing of the stator teeth against the yoke ring. For this purpose, the curved connecting webs are typically positioned between the stator teeth at the inner ends of the stator teeth or the pole pieces and have an outwardly curved bend.

[0019] In an alternative form, the expandable connecting webs can also be designed as connecting webs that are bent in the radial direction and arched towards the opening, whereby these inwardly curved connecting webs protrude in particular into the central opening of the cushion ring in a pre-assembled state. Inwardly curved means arched towards the center of the stator or the cushion ring. The center of the stator lies on the rotation axis of the motor or the rotor. When spread open, these inwardly curved connecting webs are directly stretched or straightened by the struts of the spreading tool, which significantly reduces the magnetic conductivity of the connecting webs. The connecting webs have a certain dimensional rigidity. When pressed onto the stator teeth, the connecting webs are stretched. As soon as the pressure on the stator teeth decreases, the connecting webs partially spring back to their original shape.When the struts of the spreading tool are pressed onto the connecting webs, the contact pressure directly deforms the connecting webs. This reduces the springback of the material or the connecting webs after the spreading tool is removed. This more precisely defines the radius of the stator interior, in which the motor rotor rotates. By pressing on the connecting webs, they are bent to a predefined position and thus to a defined inner diameter of the opening. The inner diameter of the opening corresponds to the stator inner radius. Due to smaller tolerances for the inner diameter, a larger rotor can be inserted into the stator, which allows for a smaller air gap between the stator and rotor and thus a greater torque.

[0020] The connecting webs preferably have a fracture notch. The fracture notch can, in particular, be punched out. Due to the tensile or bending stress during expansion, the connecting webs can break during the expansion stroke. The radial expansion stroke of the expansion tool can be increased for this purpose. The fracture of the connecting webs prevents the magnetic connection or a magnetic short circuit between the stator teeth, increasing the potential torque.

[0021] A useful embodiment provides for the yoke ring to have a plurality of recesses distributed over the inner circumferential surface for accommodating the radial ends of the stator teeth. The provision of substantially uniformly distributed recesses allows for a uniform arrangement and more precise positioning of the stator teeth during stator manufacture. In particular, these recesses, distributed over the inner circumferential surface of the yoke ring, can be designed as grooves running in the axial direction. The yoke ring is preferably cylindrical in shape. The lateral edges of the grooves enable more precise positioning of the stator teeth, while simultaneously enabling a tangential interference fit between the edges of the grooves and the radial ends of the stator teeth, the effect of which improves with the depth of the grooves.The radial ends of the stator teeth can also be rectangular in shape so that they can be securely held in the slots by the tangential press fit and thus securely connected to the yoke ring. The press fit at the edges of the axially running slots not only enables tangential force to be applied to the stator teeth, but also ensures precise alignment of the stator teeth in the direction of the rotor axis. In this design, the expandable connecting webs only serve to position the stator teeth relative to the yoke ring when inserting and spreading the cushion ring. Once the stator teeth are securely pressed into the slots on the inner circumferential surface of the yoke ring, the expandable connecting webs between the individual stator teeth can be removed after spreading the cushion ring, since the tangential press fit securely positions the stator teeth in the slots and connects them to the yoke ring.In this advantageous design, the magnetic short circuit between the stator teeth is eliminated, allowing for higher torque. The removal of the connecting webs is preferably carried out by cutting or vaporizing with a laser beam underwater. Due to their proximity to the winding core, the removal of the connecting webs is only possible to a limited extent by punching or mechanical cutting.

[0022] Non-limiting embodiments of the present invention are explained in more detail below with reference to exemplary drawings. In the drawings:

[0023] Figure 1 is a perspective view of a cushion ring for a stator according to the invention,

[0024] Figure 2 is a perspective view of the cushion ring from Figure 1 and several individual winding packages,

[0025] Figure 3 is a perspective view of the cushion ring from Figures 1 and 2 with the winding packages pushed on,

[0026] Figure 4 is a perspective view of the cushion ring with plugged-on winding packages from Figure 3 and a yoke ring,

[0027] Figure 5 is a perspective view of the yoke ring from Figure 4 with the cushion ring inserted,

[0028] Figure 6 is a perspective view of a stator according to the invention with the yoke ring from Figures 4 and 5 and the spread and pressed-in cushion ring from Figure 3,

[0029] Figure 6a is an enlarged partial sectional view of the stator from Figure 6 with a schematically illustrated spreading tool,

[0030] Figure 7 is a sectional view of the stator from Figure 6 without winding packages and with a schematically illustrated spreading tool, Figure 7a is a sectional view of the stator from Figure 7 without winding packages and without spreading tool,

[0031] Figure 8 is a perspective sectional view through the stator of Figure 6 with a spreading tool accommodated therein,

[0032] Figure 8a is a sectional view through the stator and the spreading tool from Figure 8, and

[0033] Figure 9 is an enlarged partial sectional view of a further embodiment of a stator according to the invention with a schematically illustrated spreading tool.

[0034] Figure 1 shows a perspective view of a cushion ring 1 which, together with a yoke ring 2 and winding packages 3, forms a stator 4 according to the invention. In the illustrated embodiment, the star-shaped cushion ring 1 is manufactured as a laminated core comprising several layers of stator laminations which are layered one above the other in the axial direction to form a central, cylindrical opening 5 and are connected to one another, for example by being stamped together. When the stator 4 is in the assembled state, the rotor of the electric motor is received in the opening 5 and can rotate in the axial direction. The star-shaped cushion ring 1 comprises several radially outwardly extending stator teeth 6 which, on the inner side located radially to the cylindrical opening 5, form pole shoes 7 which, in the assembled state, face the rotor of the electric motor.To position the stator teeth 6 in the cushion ring 1 and to form the closed ring of the cushion ring 1 around the opening 5, the stator teeth 6 are connected to one another in the region of the pole shoes 7 via expandable connecting webs 8. In the embodiment of the cushion ring 1 shown in Figure 1, the connecting webs 8 are designed as radially outwardly bent webs formed by individual stator laminations of the cushion ring 1 designed as a laminated core. In the embodiment shown, only individual laminations are designed with connecting webs 8, for example, only every fifth, tenth, or twentieth lamination has connecting webs 8. The connecting webs 8 are usually evenly distributed over the thickness of the stator teeth 8 in the axial direction.

[0035] As shown in Figures 2 and 3, individual prefabricated winding packages 3 are pushed onto the stator teeth 6 projecting outwards in the radial direction, each stator tooth 6 being provided with a winding package 3, see Figure 2. As can be seen in the perspective view of the cushion ring 1 in Figure 3, the winding packages 3 are pushed completely onto the stator teeth 6 up to the pole piece 7, so that the radially outwardly projecting ends 9 of the stator teeth 6 project slightly relative to the winding packages 3.

[0036] The perspective view in Figure 4 shows not only the cushion ring 1 with the winding packs 3 pushed onto the stator teeth 6, but also the yoke ring 2 in an assembled position. The yoke ring 2 has recesses 10 on its inner circumference for positioning the stator teeth 6, which in this embodiment are designed as grooves 19 extending in the axial direction. In the assembled position shown here, each radially projecting end 9 of the stator teeth 6 is aligned with a groove 19 extending in the axial direction on the inner circumference of the yoke ring 2. Like the cushion ring 1, the yoke ring 2 can also be manufactured as a laminated core made of stator laminations stacked one above the other in layers.As shown in Figure 5, the yoke ring 2 is pushed axially onto the cushion ring 1 during assembly, with the protruding ends 6 of the stator teeth 6 merely being guided through the grooves 19 on the inner circumference of the yoke ring 2, so that no chips or notches can form on the grooves 19 and the protruding ends 9. A gap 11 remains between the protruding ends 9 and the groove bottom 20 of the grooves 19.

[0037] After positioning the cushion ring 1 in the yoke ring 2, a force acting in the radial direction is exerted from the opening 5 onto each stator tooth 6 or each pole piece 7 of the stator teeth 6, so that the protruding ends 9 of the stator teeth 6 are pressed into the recesses 10. As can be seen in Figure 6, the protruding ends 9 of the stator teeth 6 then rest against the bottom 20 of the slots 19, so that the initially existing gap 11 is essentially filled by the protruding ends 9.

[0038] When the cushion ring 1 is radially expanded and the protruding ends 9 are pressed into the recesses 10 of the yoke ring 2, the opening 5 widens and the distance between the individual stator teeth 6 increases. Due to the increasing distance between the stator teeth 6, the expandable connecting webs 8 between the stator teeth 6 are stretched as the cushion ring 1 is radially expanded, so that the bending of the connecting webs 8 flattens. Since the connecting webs 8 in this embodiment are formed by the stator laminations of the laminated core of the cushion ring 1, the majority of the stretching of the connecting webs 8 occurs as plastic deformation. This can also be seen in the enlarged partial sectional view with the expanded cushion ring 1 and the stator teeth 6 pressed into the grooves 19 of the yoke ring 2 in Figure 6a.By means of the spreading tool 12, which is only shown schematically here, a radial force is applied to the stator teeth 6, so that the protruding ends 9 of the stator teeth 6 are pressed firmly into the grooves 19 of the yoke ring 2, whereby the bending of the connecting webs 8 flattens in order to compensate for the larger distance between the stator teeth 6.

[0039] The press fit between the stator teeth 6 and the yoke ring 2 is essentially created by tangential forces between the side walls of the slots 19 and the protruding end 9 of the stator teeth 6. Due to the permanent press connection between the stator teeth 6 and the yoke ring 2, the connection between the individual stator teeth 6 via the connecting webs 8 is no longer required after the cushion ring 1 has been spread open, which is why the connecting webs 8 can also be removed after the spreading process. Furthermore, due to the uniform spreading process and the uniform pressing of the stator teeth 6 into the yoke ring 2, all stator teeth 6 are pushed outwards essentially evenly and to the same extent by the spreading tool 12, so that the pole shoes 7 of the stator teeth 6 all have the same distance from the axial axis. This can be seen particularly well in the sectional views of the stator 4 without winding packs 3 in Figures 7 and 7a.

[0040] Figure 8 shows a perspective sectional view through a spreading tool 12 with a stator 4 arranged therein. The spreading tool 12 has a thick-walled support ring 13 against which the yoke ring 2 rests during the spreading and pressing process so that the yoke ring 2 is not expanded or bent. This sectional view also shows the structure of the stator teeth 6 or the cushion ring 1 from a laminated core of stator laminations stacked one above the other. The spreading tool 12 has a working wedge 14 that can be moved in the axial direction, wherein the working wedge 14 is moved against the preload force of a spring 15 by means of a centrally arranged threaded bolt 16. The conically tapered flanks of the working wedge 14 act on several radially movable struts 17, which are held on the working wedge 14 by elastic rings 18, see also Figure 8a.The force applied in the axial direction via the working wedge 14 is transferred via the inclined inner flanks of the struts 17 into a radial force which acts uniformly on the straight outer flanks of the struts 17 onto the stator teeth 6 and presses them into the recesses 10 on the yoke ring 2.

[0041] A further embodiment of a stator 4 according to the invention and a corresponding method for manufacturing is shown in Figure 9, which shows an enlarged partial sectional view of the stator 4 and a schematically illustrated spreading tool 12. The cushion ring 1 of this stator 4 according to the invention again has a plurality of stator teeth 6 with internal pole shoes 7 and protruding ends 9. The cushion ring 1 is arranged in a yoke ring 2, and each stator tooth 6 of the cushion ring 1 is provided with a winding package 3 previously pushed on from the outside. To form the cushion ring 1, the individual stator teeth 6 are provided with plastically deformable connecting webs 8 at the edges of the pole shoes 7, wherein the bend of the connecting webs 8 protrudes inwards relative to the pole shoes 7 into the opening 5 of the cushion ring 1.In this variant, the spreading tool 12 generates a radial force that acts on the connecting webs 8 between the individual stator teeth 6 and straightens the connecting webs 8 to spread the cushion ring 1. As a result, the protruding ends 9 of the stator teeth 6 are pressed against the inner circumferential surface of the yoke ring 2 to create a permanent press fit of the cushion ring 1 or the stator teeth 6 on the yoke ring 2. By bending the connecting webs 8, the magnetic conductivity of the connecting webs 8 is reduced in order to reduce the undesirable magnetic short circuits between the individual stator teeth 6. In this embodiment, too, recesses 10 or grooves 19 running in the axial direction can be provided on the inner circumferential surface of the cylindrical yoke ring 2 in order to precisely position the stator teeth 6.

[0042] List of reference symbols

[0043] 1 cushion ring

[0044] 2 yoke ring

[0045] 3 winding packages

[0046] 4 Stator

[0047] 5 Opening

[0048] 6 stator teeth

[0049] 7 Pole piece

[0050] 8 connecting bridges

[0051] 9 protruding ends

[0052] 10 recesses

[0053] 11 gap

[0054] 12 Spreading tool

[0055] 13 Support ring

[0056] 14 Working wedge

[0057] 15 spring

[0058] 16 threaded bolts

[0059] 17 struts

[0060] 18 elastic rings

[0061] 19 grooves

[0062] 20 groove base

Claims

Claims 1. Method for producing a stator (4) for an electric motor, comprising the steps: Providing a yoke ring (2) and a cushion ring (1) with a plurality of stator teeth (6) for arranging windings, preferably winding packages (3), wherein the cushion ring (1) can be received in the yoke ring (2); Inserting the cushion ring (1) into the yoke ring (2), with the stator teeth (6) facing the yoke ring (2); and - Spreading the cushion ring (1), whereby the stator teeth (6) are pressed against the yoke ring (2).

2. The method according to claim 1, wherein the cushion ring (1) has an opening (5) with an inner diameter for arranging a rotor and the spreading of the cushion ring (1) widens the inner diameter of the opening (5).

3. Method according to claim 1 or 2, wherein one or more inwardly projecting connecting webs (8) are provided in spaces between the individual stator teeth (6) to form the cushion ring (1), and the cushion ring is spread open by pressing onto the connecting webs (8).

4. Method according to one of claims 1 to 3, wherein the yoke ring (2) has a plurality of recesses (10) on an inner circumferential surface for receiving the stator teeth (6) of the cushion ring (1), and when the cushion ring (1) is spread open, the stator teeth (6) are pressed into the recesses (10).

5. Method according to one of claims 1 to 4, wherein a spreading tool (12), preferably a spreading tool with a wedge-shaped spreading element (14), is introduced into the cushion ring (1) in order to spread the cushion ring (1).

6. The method according to claim 5, wherein the spreading tool (12) has a plurality of radially movable struts (17), preferably for each stator tooth (6) a strut (17) associated with the stator tooth (6), and the struts (17) are pressed radially outwards in order to spread the cushion ring (1).

7. Method according to claim 5, wherein one or more inwardly projecting connecting webs (8) are provided in the spaces between the individual stator teeth (6) to form the cushion ring (1), and the spreading tool (12) has a plurality of radially movable struts (17), preferably a strut (17) associated with the space for each space between the individual stator teeth (6), and the struts (17) are pressed radially outwards in order to straighten the connecting webs (8) and thereby spread the cushion ring (1).

8. Method according to claim 7, wherein the connecting webs (8) are removed after the cushion ring (1) has been spread open, in particular by cutting or evaporation with a laser beam under water.

9. Stator (4) for an electric motor with a yoke ring (2), preferably a cylindrical yoke ring (2), a cushion ring (1) which can be received in the yoke ring (2) and has a plurality of stator teeth (6) and an opening (5) for arranging a rotor, and windings, preferably winding packages (3), which are arranged on the stator teeth, characterized in that the stator teeth (6) of the cushion ring (1) are connected to one another via expandable connecting webs (8), wherein the connecting webs (8) are plastically deformed in the assembled state compared to an original state of the stator (4) and the stator teeth (6) are pressed against the yoke ring (2) compared to an original state.

10. Stator (4) for an electric motor according to claim 9, characterized in that the cushion ring (1) is designed as a stack of stator laminations, wherein individual stator laminations are designed as lamination rings which extend over all stator teeth (6) of the cushion ring (1) and form the expandable connecting webs (8) between the stator teeth (6).

11. Stator (4) for an electric motor according to claim 10, characterized in that at least three stator laminations are designed as lamination rings are, whereby the sheet rings are preferably evenly distributed over the thickness of the sheet stack.

12. Stator (4) for an electric motor according to one of claims 8 to 11, characterized in that the expandable connecting webs (8) are designed as curved connecting webs (8), preferably with a bend in the radial direction.

13. Stator (4) for an electric motor according to claim 12, characterized in that the expandable connecting webs (8) are designed as connecting webs (8) bent in the radial direction and curved towards the opening (5), wherein the connecting webs (8) in a pre-assembled state protrude in particular into the opening (5) of the cushion ring (1).

14. Stator (4) for an electric motor according to one of claims 12 to 13, characterized in that the connecting webs (8) have a breaking notch.

15. Stator (4) for an electric motor according to one of claims 9 to 14, characterized in that the yoke ring (2) has a plurality of recesses (10) distributed on the inner circumferential surface for receiving the radial ends (9) of the stator teeth (6).

16. Stator (4) for an electric motor according to claim 15, characterized in that the recesses (10) distributed on the inner circumferential surface of the yoke ring (2) are designed as grooves (19) extending in the axial direction.

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