EP4331085A1

EP4331085A1 - Rotor for an electric motor

Info

Publication number: EP4331085A1
Application number: EP22730710.5A
Authority: EP
Inventors: Jochen Dehn; Sandro FISCHER
Original assignee: Brose Fahrzeugteile SE and Co KG
Current assignee: Brose Fahrzeugteile SE and Co KG
Priority date: 2021-05-20
Filing date: 2022-05-19
Publication date: 2024-03-06
Also published as: WO2022243411A1; US20230396106A1

Abstract

The invention relates to a rotor (2) for an electric motor, having a rotor body (4) with a cylindrical rotor packet (6) and a number of surface magnets (16), which are distributed on a lateral surface (12) of the rotor packet (6) in the form of rotor poles and which have a bread loaf-shaped cross-section with a convex curvature (40) oriented towards the outer circumference, and having a cuff-shaped protective sleeve (36), which is exposed on the outer circumference of the rotor body (4), wherein the protective sleeve (36) has a flange collar (44) at least on an end face, said flange collar being shaped into the radially indented regions (42) between the curvatures (40) of tangentially adjacent surface magnets (16) in a form- and/or force-fitting manner.

Description

description

Rotor for an electric motor

The invention relates to a rotor for an electric motor, comprising a rotor body with a cylindrical rotor core and magnets with a number of surfaces, and a sleeve-like protective sleeve which is placed on the outer circumference of the rotor body. The invention further relates to a method and a device for producing such a rotor, and an electric motor with such a rotor.

In a modern motor vehicle, electric motors are used in a variety of ways as drives for different control elements. Electric motors are used, for example, as power window, sunroof or seat adjustment drives, as steering drives (EPS, Electrical Power Steering), as cooling fan drives or as gear actuators. Such electric motors have to have a relatively high torque or power density and be operationally reliable even at high temperatures.

An electric motor as an energy converter of electrical energy into mechanical energy comprises a stator, which forms the stationary motor part, and a rotor, which forms the moving motor part. In the case of an internal rotor motor, the stator is usually provided with a stator yoke on which are arranged radially to the center, ie star-shaped inwards, protruding stator teeth whose free ends facing the rotor form the so-called pole shoe.

A particular brushless electric motor as an electrical (three-phase) machine usually has a stator provided with a field or stator winding, which is arranged coaxially to a rotor with one or more permanent magnets.

The rotor generally has a rotor body with a cylindrical, stamped (rotor) laminated core as the central rotor core. The rotor pack is here- joined, for example, fixed to the shaft with a motor shaft of the electric motor. The rotor stack has, for example, receptacles into which the permanent magnets are pressed. Alternatively, it is also conceivable, for example, for the permanent magnets to be fastened or held as surface magnets on an outer circumference of a jacket surface of the rotor core. For this purpose, it is conceivable, for example, for the surface magnets to be joined to the lateral surface in a materially bonded manner, in particular by means of an adhesive or epoxy. Also conceivable are holding devices for the non-material connection attachment and/or holding of the surface magnets on the lateral surface.

The surface magnets conventionally have a cross-sectional shape in the shape of a loaf of bread. In other words, the permanent magnets of the rotor are designed as surface-mounted bread loaf magnets. A cross-sectional shape in the form of a loaf of bread is to be understood here and in the following in particular as the shape of a box loaf of rectangular shape, in which one of the long sides is designed to curve convexly outwards. Due to the curvature of the surface magnets, the outer circumference of the rotor body is not circular in shape.

During operation of the electric motor, due to the high speeds, large centrifugal forces act on the surface magnets of the rotor, which increases the risk of the surface magnets becoming undesirably detached from the lateral surface. In order to prevent a surface magnet from detaching from the lateral surface and blocking the electric motor in a gap area between the rotor and the stator, a sleeve-like protective sleeve (protective tube) is usually placed on the rotor body to protect it from being thrown.

Typically, an edge of the protective sleeve for fastening to the rotor body is bent radially inwards (crimped) so that the rotor body is axially overlapped by the front side of the protective sleeve. The forming or flanging is done here, for example, by rolling or by pressing. When burnishing or rolling, the material of the protective sleeve is deformed all around. Since the sleeve to be deformed is not held completely round by the rotor stack due to the curvature of the surface magnets, it can happen that the material of the protective sleeve is partially constricted during the rolling process, which leads to the formation of cracks and an associated reduction in mechanical stress Stability of the protective sleeve can come.

During pressing, a round tool is pressed from above against the protective sleeve or the rotor body. Comparatively large forces are necessary, so that the resulting mechanical (compressive) stresses can lead to bulking, i.e. compression, bulging or cambering of the protective sleeve, which means that the material of the protective sleeve radially penetrates the air gap between the rotor and stator wanders.

DE 102019205993 A1 discloses a protective sleeve for a rotor which has a flanged collar which is flanged on the face side for attachment to the rotor body. The flanged collar has a number of tangentially and axially running recesses, by means of which the stresses that occur during flanging can be reduced.

The invention is based on the object of specifying a particularly suitable rotor for an electric motor and a corresponding electric motor. The invention is also based on the object of specifying a particularly suitable method and a particularly suitable device for producing such a rotor. In particular, a cost-effective and effort-reduced assembly of the rotor should be made possible, in which the necessary assembly forces are reduced.

With regard to the rotor, the object is achieved with the features of claim 1 and with regard to the method with the features of claim 3 and with regard to the device with the features of claim 6 and with regard to the electric motor with the features of claim 10 according to the invention. Advantageous te configurations and developments are the subject of the dependent claims. The rotor according to the invention is suitable and set up for an electric motor, in particular for an internal rotor of a motor vehicle designed as an SPM motor (Surface Permanent Magnet). In other words, the rotor according to the invention is in particular an SPM rotor.

In this case, the rotor has a rotor body which can be firmly joined or joined to a motor shaft. The rotor body has a cylindrical rotor stack, which is designed, for example, as a stamped stacked laminated core (laminated rotor core) with a number of rotor laminations stacked along an axial direction. On the outer circumference of a lateral surface of the rotor core, a number of permanent-magnetic surface magnets are distributed as rotor or pole magnets. The surface magnets here have a bortlaibför-shaped cross-sectional shape with a convex curvature oriented towards the outer circumference. The rotor stack has in particular an equilateral polygonal or multi-cornered base area, so that the lateral surface has a number of contact surfaces for the surface magnets with the same surface area along a tangential or azimuthal direction, i.e. along the outer circumference.

To protect the surface magnets from being thrown, a sleeve-like protective sleeve is placed on the outer circumference of the rotor body. According to the invention, the protective sleeve has a flanged collar on at least one end face, which is formed into the radially constricted areas or flanks between the bulges of tangentially adjacent surface magnets in a positive and/or non-positive manner. As a result, a particularly suitable rotor is realized.

According to the invention, the space between the surface magnets is used to attach the protective sleeve to the rotor body. Since the distance between the rotor body and a surrounding stator is greater in these areas than in the area of the bulges (or their crests), a material of the protective sleeve that is bulky (compressed, curved, cambered) due to the deformation does not impair the air gap or the electric motor represent. In contrast to the prior art, the front beaded edge or beaded collar of the protective sleeve is not completely reshaped, but only at the points arranged between the bulges. According to the invention, the non-circular outer peripheral shape of the rotor body is thus used to fasten the protective sleeve.

The conjunction “and/or” is to be understood here and in the following in such a way that the features linked by means of this conjunction can be designed both together and as alternatives to one another.

A "positive fit" or a "positive connection" between at least two parts connected to one another is understood here and in the following in particular to mean that the parts connected to one another are held together at least in one direction by a direct interlocking of the contours of the parts themselves or by an indirect Interlocking takes place via an additional connecting part. The "blocking" of a mutual movement in this direction is therefore due to the shape. A “positive connection” or a “positive connection” between at least two parts connected to one another is understood here and in the following in particular to mean that the parts connected to one another are prevented from sliding off one another due to a frictional force acting between them. If there is no "connection force" that causes this frictional force (this means the force that presses the parts against each other, for example a screw force or the force of weight itself), the non-positive connection cannot be maintained and can therefore be released.

“Axial” or an “axial direction” is understood here and in the following in particular as a direction parallel (coaxial) to the axis of rotation of the electric motor, ie perpendicular to the end faces of the rotor. Correspondingly, here and below, the terms “radial” or a “radial direction” are used in particular in a direction oriented perpendicularly (transversely) to the axis of rotation of the electric motor along a radius of the Rotor or the electric motor understood. Here and in the following, “tangential” or a “tangential direction” means in particular a direction along the circumference of the rotor (circumferential direction, azimuthal direction), ie a direction perpendicular to the axial direction and to the radial direction.

In an advantageous embodiment, the rotor body has a holding device, which is placed on the end face of the rotor core, for fastening and/or holding the surface magnets on the lateral surface of the rotor core without a material bond. The bulges of the surface magnets protrude radially from the outer circumference of the holding device. In other words, the bulges of the surface magnets form the radially outermost points of the rotor body. Since the holding device is therefore somewhat smaller and there is no magnet in the axial direction in the areas between the bulges, the material of the protective sleeve can also be displaced downwards during the forming process, i.e. axially away from the formed end face into the free area be, which leads to a lower bulking of the Ma material in the radial direction. As a result, the protective sleeve fits snugly against the rotor body 4 in a particularly compact manner, so that when installed, an air gap that is as uniform as possible is realized between the rotor and the stator.

A "material connection" or a "material connection" between at least two parts connected to one another is understood here and in the following in particular to mean that the parts connected to one another at their contact surfaces through material union or crosslinking (e.g. due to atomic or molecular bonding forces) optionally held together under the action of an additive. Correspondingly, “free of material connection” means in particular that there is no material connection between the surface magnets and the outer surface when the surface magnets are attached. The surface magnets are therefore only fastened to the rotor core in a positive and/or non-positive manner by means of the holding device.

The holding device has, for example, two one-piece, i.e. one-piece or monolithic, holding rings (isolation discs) which are attached to the opposite ing end faces of the rotor core are arranged. The retaining rings, which are embodied, for example, as injection-molded parts, each have a circular annular body with retaining contours on the outside radially and protruding axially in the direction of the rotor core.

The retaining rings are in particular made of a glass fiber reinforced plastic material, for example a polyamide (PA), in particular PA 6.6 GF30, or a polyphenylene sulfide (PPS), in particular PPS GF30, or a polyoxymethylene (POM), in particular POM GF30. The abbreviation GF30 stands for a glass fiber content of 30%.

The holding contours are designed in such a way that they interlock radially and tangentially between the surface magnets. As a result, the surface magnets are held in the radial and tangential direction without a material bond on the lateral surface. For the axial fixation of the surface magnets, it is provided, for example, that the surface magnets are enclosed axially between the two retaining rings. For this purpose, the surface magnets are at least partially covered radially by means of the ring body. In particular, an axial form fit between the retaining rings is thus realized.

Thus, the geometry required for holding and/or fastening the surface magnets is only provided on the holding device, as a result of which the rotor core can have a particularly simple geometric shape. In particular, the rotor core does not have any additional measurements or contours or extensions on the lateral surface, as a result of which the rotor laminations and thus the rotor core can be produced particularly easily and inexpensively. Furthermore, the magnetic field lines of the permanent magnets within the rotor stack are not disturbed by the arrangement of the permanent magnets on the jacket surface.

The method according to the invention is intended for the production of a rotor described above, and is suitable and configured for this. apply the explanations in connection with the rotor also apply to the process and vice versa.

If method steps are described below, advantageous configurations for the device result in particular from the fact that it is designed to carry out one or more of these method steps.

According to the method, a rotor body and a protective sleeve are provided. The cuff-like protective sleeve is, for example, designed essentially in the shape of a pot. This means that the protective sleeve has a (sleeve) base as a face contact surface for the rotor body. The bottom or the contact surface has, for example, a central recess as a through-opening for a motor shaft. A front area of the protective sleeve opposite the contact surface is designed as a flared collar of the protective sleeve and, after the rotor body has been inserted into the protective sleeve, is formed, caulked or non-positively into the radially drawn-in areas between the bulges of the tangentially adjacent surface magnets crimped. This means that the assembly forces for joining the protective sleeve to the rotor body are specifically introduced into the intermediate areas between the bulges. This reduces the required assembly forces, particularly in the area of the holding device, and there is essentially no radially projecting deformation of the protective sleeve into the air gap area, which improves the system security of an electric motor. The process can essentially be used with all SPM rotors with bread loaf magnets, regardless of the number of poles.

In contrast to the prior art, the protective sleeve is not formed or crimped by means of rolling or pressing, but essentially by caulking in the intermediate areas of the protective sleeve. In other words, the material of the protective sleeve is constricted in a targeted or local manner in the intermediate areas and thus nestled against the non-round outer contour of the rotor body. In a suitable development, the protective sleeve has a bevel that is radially widened on the end face as an insertion aid for the rotor body. In other words, the protective sleeve has an oversize protruding into the air gap on the end face, so that the rotor body can be inserted in a funnel-like manner. This simplifies the insertion of the rotor body into the protective sleeve. The rotor body is inserted into the protective sleeve via the chamfer, with the chamfer then being bent or straightened radially inwards by means of a first punch before the flanged collar is formed. This means that the first stamp radially inwards bends the oversize of the protective sleeve protruding into the air gap. In this case, the bent bevel forms, for example, the flanged collar for the subsequent forming or flange step.

In an expedient embodiment, the flanged collar is pressed onto the outer circumference of the rotor body by means of a second stamp after it has been formed. This takes into account the fact that the material of the protective sleeve is pushed away by the forming or by the flanging in the area of the bulges. In other words, before the forming process, the bulges are essentially in contact with the inner circumference of the protective sleeve, with the protective sleeve being lifted off the bulges as a result of the forming. This means that due to the deformation of the protective sleeve, a clear (radial) distance can form between the bulges and the protective sleeve. The protective sleeve is thus deformed radially into the air gap in the area of the bulges. This deformation in the area of the bulges is corrected with the subsequent second stamping process, and the protective sleeve is thus pressed or pressed against the surface magnets again in the area of the bulges. This ensures that the protective sleeve does not bulk into the air gap inadmissibly.

The advantages and configurations listed with regard to the rotor and/or the method can also be transferred to the device described below and vice versa. The device according to the invention is intended for the manufacture of a rotor described above, and is also suitable and set up for it. In this case, the device has a crown tool which ches is provided and set up to form a flared collar of the protective sleeve positively and/or non-positively into the radially constricted areas between the bulges of tangentially adjacent surface magnets of the rotor body. The device also has, for example, a first and second stamp. As a result, a particularly suitable device is realized.

The crown tool of the device thus deforms the protective sleeve not tangentially circumferentially, but only selectively or locally at the free spaces between the rotor body and the protective sleeve that are freed by the bulges.

In an expedient embodiment, the crown tool has a cylindrical tool body with a crown rim at the front, facing the rotor. In this case, the crown ring is designed for reshaping or deforming the flange collar. A central extension is also provided on the tool body, which engages in a through-opening of the rotor body during the forming process. The through-opening of the rotor body serves to accommodate a rotor or motor shaft when installed. The extension, for example in the form of a bolt or cylinder, engages in this case, for example, in a form-fitting manner in the central through-opening, so that the rotor body is positioned, stabilized and centered in the course of the forming process. The crown and the extension are in this case in one piece, ie in one piece or monolithic, formed on the tool body by. The extension is designed here, for example, as a pin or peg of the tool body. For forming, the crown tool is lowered in the manner of a stamp from above onto the rotor body equipped with the protective sleeve, with the extension engaging in the through-opening, and where the crown collar partially forms, caulks, or crimps the flanged collar.

In a conceivable embodiment, the crown rim has a number of axially protruding crown or pinnacle extensions, which are distributed tangentially along the circumference of the tool body. Preferably, each pinnacle extension has a radially inwardly directed forming nose, which in The flanged collar is formed during the forming process. This results in a particularly suitable tool and thus a particularly suitable device for producing the rotor. In a preferred application, the rotor described above is part of an electric motor. The electric motor according to the invention is suitable and set up for a power steering system of a motor vehicle, for example. The advantages and configurations listed with regard to the rotor and/or the method and/or the device can also be transferred to the electric motor and vice versa

In this case, the electric motor has a stator and a motor shaft which is rotatably mounted relative to this and on which the rotor is carried fixedly to the shaft. The electric motor is designed here, for example, as a brushless electric motor in the manner of an internal rotor.

In an application for power steering, the electric motor is arranged in the area of a driver's cab, with the rotor according to the invention ensuring particularly smooth engine operation, since the surface magnets and protective sleeve are held without shaking on the rotor core. As a result, the development of noise from the electric motor is reduced in an advantageous and simple manner, which is advantageously transferred to the user comfort of the motor vehicle.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. Show in it:

1 shows a perspective view of a rotor in a partially dismantled state,

2 in a perspective exploded view of the rotor, FIG. 3 in a plan view of the rotor in a pre-assembly state, FIG. 4 in perspective of a first punch for manufacturing the rotor, FIG figure 4, 6 shows a crown tool for manufacturing the rotor, FIG. 7 shows perspective views of the end face of the rotor after machining with the crown tool according to FIG. 6,

Fig. 8 in perspective a second die for producing the rotor,

9 shows a perspective view of the end face of the rotor after machining with the second punch according to FIG. 8, and

10 shows the rotor in a side view. Corresponding parts and sizes are always provided with the same reference numbers in all figures.

In Fig. 1, a rotor 2 of an electric motor, not shown is Darge provides. The electric motor designed as a brushless internal rotor is, for example, part of an electric power steering system of a motor vehicle. The rotor 2 has a rotor body 4 with an approximately cylindrical rotor stack 6 which is joined to a motor shaft or rotor shaft 8 so that it is fixed to the shaft. The motor shaft 8, and thus the rotor 2, are rotatably mounted in the assembled state with respect to a stationary stator of the electric motor. In the assembled state, an annular air gap is formed between the outer circumference of the rotor 2 and the inner circumference of the stator.

2 shows the rotor 2 in a disassembled state using an exploded view. As can be seen comparatively clearly in the exploded view in FIG. 2, the rotor core 6 in this exemplary embodiment has an equilateral, decagonal base area. The rotor stack 6 is formed here from a number of rotor laminations, not designated in any more detail, which are stacked and punched along an axial direction A to form a laminated core (laminated rotor core). The rotor assembly 6 has a central feed-through opening 10 for receiving the motor shaft 8 . The rotor core 6 also has a circumferential surface 12 extending in the axial direction A, which has ten similar contact surfaces corresponding to the base surface. chen 14 trains. The contact surfaces 14 are provided with reference numbers in the figures merely by way of example.

In this embodiment, the rotor 2 is designed as an SPM rotor with ten permanent-magnetic surface magnets 16 for generating a magnetic excitation field. The surface magnets 16 , which are provided with reference numbers only as an example, are distributed along a tangential or azimuthal direction T on the outer circumference of the lateral surface 12 on the rotor core 6 . The surface magnets 16 are embodied as loaf magnets and each have an approximately loaf-shaped cross-sectional shape along the axial direction A, with the surface magnets 16 being positioned on a respective associated contact surface 14 of the lateral surface 12 . In the assembly state of the rotor 2, the surface magnets 16 are held and/or fastened to the lateral surface 12 of the rotor core 6 by means of a holding device 18 without a material bond.

The holding device 18 has two holding rings or insulating discs 20 . As can be seen comparatively clearly from FIGS. 1 and 2, the retaining rings 20 are placed on the opposite end faces 22a, 22b of the rotor core 6 in the joined or assembled state. The retaining rings 20 each have an annular body 24 in the form of a circular ring. A central annular opening 26 is made in the annular body 24 for the passage of the motor shaft 8 . The inner circumference of the annular body 24 that is radially inward along a radial direction R, that is to say the inner wall of the annular opening 26, has an approximately star-shaped cross-sectional shape or inner contour in the exemplary embodiments shown.

The star-shaped cross-sectional shape of the inner wall is formed here by ten ra dial inwardly projecting tooth extensions 28 of the annular body 24. The tooth extensions 28 are only provided with reference numbers in the figures as an example. On an underside facing the rotor core 6, the ring bodies 24 each have ten holding contours 30 on the outer circumference and ten attachment extensions 32 on the inner circumference. The retaining contours 30 and the fastening supply extensions 32 are the underside of the ring body 24 axially upstanding molded. The retaining contours 30 are distributed evenly along the outer circumference of the ring body 24 . The attachment extensions 32 are distributed along the inner circumference, the attachment extensions 32 being integrally formed in particular in the region of a respective radially inner tooth end of the tooth extensions 28 , ie in one piece or monolithically.

As can be seen, for example, in the illustration in FIG.

To reduce the mass moment of inertia of the rotor 2, the rotor core 6 is provided with ten recesses 34 passing through the laminated core. From savings 34 are arranged along the tangential direction T evenly distributed around the central through-opening 10 around. The recesses 34 are provided with reference numbers in the figures merely as an example.

As can be seen in particular in FIG. 3 , the recesses 34 have an approximately teardrop-shaped cross-section along the axial direction A. In the assembled state, the attachment projections 32 of the annular body 24 engage in the recesses 34 . The teardrop shape of the recesses 34 acts like a centering aid when the retaining rings 20 are joined to the rotor core 6. This means that the retaining ring 20 engages axially in the rotor core 6 at least in sections by means of the attachment extensions 32.

The holding contours 30 arranged radially on the outside along the radial direction R have an approximately trapezoidal cross-sectional shape along the axial direction A. The bases of the cross-sectional shape are oriented along the tangential direction T. In this case, the radially inner base side has a shorter dimension in comparison to the radially outer base side. The leg sides running between the base sides run obliquely to the tangential direction T and obliquely to the radial direction R. As can be seen, in particular, in FIG. In other words, the holding contours 30 are arranged in the corner areas between two adjacent contact surfaces 14 . In this case, the cutouts 34 are oriented approximately in the middle of the respective contact surfaces 12 along the radial direction R.

As can be seen comparatively clearly in the top view of FIG. The sides of the limbs of the holding contours 30 bear against the radially outer contour of the surface magnets 16 in such a way that the surface magnets 16 are enclosed tangentially and radially in these contact areas, at least in sections. This means that the surface magnets 16 are held in a form-fitting manner along the tangential direction T and the radial direction R by means of the holding contours 30, with the engagement of the fastening extensions 32 in the recesses 34 preventing the surface magnets 16 from rotating or preventing them from rotating on the lateral surface 12 is realized.

The surface magnets 16 are here on the end faces 22 a, 22 b of the rotor packet 6 along the radial direction R at least partially covered by the ring bodies 24 of the retaining rings 20 . Thus, the surface magnets 16 are framed in a form-fitting manner along the axial direction A between the retaining rings 20 .

To protect the surface magnets 16 from being thrown, a sleeve-like protective sleeve 36 is placed on the outer circumference of the rotor body 4 . The protective sleeve 36 is preferably made of steel, in particular stainless steel. In other words, the protective sleeve 36 is in particular a stainless steel sleeve.

A method for manufacturing the rotor 2, in particular for attaching the protective sleeve 36 to the rotor body 4, by means of a device that is not shown in detail is explained in more detail below with reference to FIGS. In a first method step, the rotor body 4 is inserted into the protective sleeve 36 . For this purpose, the protective sleeve 36 on the end face facing the rotor body 4 has, for example, a radially widened chamfer 38 (FIG. 1) as an insertion aid. The chamfer 38 here has a radial oversize protruding into the air gap, so that the rotor body 4 can be inserted or introduced into the protective sleeve 36 like a funnel.

As can be seen in particular in FIG. 3, the surface magnets 16 have a convex curvature 40 on the outer circumference. The bulges 40 of the surface magnets 16 protrude radially from the outer circumference of the annular body 24 . In other words, the bulges 40 of the surface magnets 16 form the radially outermost points of the rotor body 4. Due to the bulges 40 of the surface magnets 16, the outer circumference of the rotor body 4 therefore has no circular (outer) shape or (outer) contour. In this case, the protective sleeve 36 essentially has a circular cross-sectional shape, which bears on the inner circumference at the crests of the bulges 40 . As a result, between the protective sleeve 36 and the flanks of two tangentially adjacent surface magnets 16 in each case, ten circumferentially distributed areas 42 or free spaces are formed as clearances between the outer circumference of the rotor body 4 and the inner circumference of the protective sleeve 36 .

After the rotor core 4 has been inserted into the protective sleeve 36, the chamfer 38 is bent or straightened radially inwards by means of a (first) stamp 43 shown in FIG. 4 (FIG. 5). This means that the punch 43 bends the oversize of the protective sleeve 36 radially inwards, which protrudes into the air gap. For this purpose, the approximately cylindrical die 43 has a circular indentation with chamfer-like inclined side walls on the end face. When the plunger 43 is lowered, the chamfer 38 of the protective sleeve 36 is pressed against the outer circumference of the rotor core 4 by the inclined side walls.

In a next method step, a front flanged collar (flared edge) 44 of the protective sleeve 36 is reshaped. The flanged collar 44 is in this case an end-side axial section of the protective sleeve 36, which, for example, the directed Chamfer 38 includes. The flanged collar 44 which is not shaped around it protrudes at least partially axially from the seated rotor body 4 . In the representations of FIGS. 5, 7 and 9, the (non-formed) flanged collar 44 has, for example, an axial overhang of less than 15 mm (millimeters), in particular less than 10 mm, for example approximately 5 mm.

After the rotor body 4 has been inserted into the protective sleeve 36 , the flanged collar 44 is shaped, caulked or flanged into the radially constricted areas 42 between the bulges 40 in a positive and/or non-positive manner.

This means that the assembly forces for joining the protective sleeve 36 to the rotor body 4 are specifically introduced into the intermediate areas. In other words, the free spaces or free spaces formed between the flanks of the bulges 40 are used as points of attack for a forming tool. This means that the surface of the protective sleeve 36 is deformed or flanged radially inward in the areas 42 as local caulking surfaces.

For forming the flanged collar 44, the device has a crown tool 46 as a forming die. 6 crowns tool 46 of the device has a cylindrical tool body 48 with an end face, the rotor 2 facing crown ring 50 and a zentra len recess 52 for an extension not shown in detail.

The bolt-shaped or cylindrical extension is inserted into the recess 52, for example, as a pin or Zap fen. Alternatively, the extension can also be integrally formed on the tool body 48 . The diameter of the extension is slightly smaller than the inner diameter of the through-opening 10.

The crown ring 50 has ten crown or pinnacle extensions 54 distributed around the circumference. The pinnacle extensions 54 each have a deforming nose 56 directed radially inwards. The forming nose 56 has an axially inclined ramp as a forming contour for the flanged collar 44 . For forming, the crown tool 46 is lowered from above the rotor body 4 fitted with the protective sleeve 36 in the manner of a punch in the direction of the end face 22a. Here, the extension engages in the through-opening 10, so that the rotor body 4 and the crown tool 46 are centered and aligned axially with one another. When the crown tool 46 is lowered, the flange collar 44 is formed, caulked, or flanged into the areas 42 by means of the forming lugs 56 .

The upper edge of the flanged collar 44 is flanged radially inward in the regions 42 by the crown tool 46, so that the retaining ring 20—and thus the rotor body 4—in the regions 42 is at least partially overlapped axially by the flanged collar 44.

7 shows a view of the end face of the rotor 2 after the forming process using the crown tool 46. As can be seen comparatively clearly in FIG or aloof. In other words, as a result of the forming in the areas 42, a clearance 58 is formed in the area of the bulges 40 between them. As a result, the protective sleeve 36 is radially deformed in the area of the bulges 40 or in the area of the distances 58 into the future air gap between the rotor 2 and the stator.

In order to reduce the distances 58, the flanged collar 44 is therefore pressed axially and radially onto the rotor body 4 or the retaining ring 20 in a third method step by means of a (second) punch 59 shown in FIG. The ram 59 is designed similarly to the ram 43, the central depression of the ram 59 being deeper than that of the ram 43. For example, the diameter of the indentation is larger in stamp 43 than in stamp 59. Stamps 43 and 59 also have recesses 52, for example, for an extension that engages in through-opening 10 when lowered. 9 and 10 show the rotor 2 in the assembled state after the third process step. The material of the protective sleeve 36 in the area of the flanged collar 44 is pressed from the outside onto the rotor body 4 by the (second) stamp 43, so that the distances 58 are essentially formed to zero. In other words, the protective sleeve 36 or the flanged collar 44 is nestled against the bulges 40 on the outer circumference. The protective sleeve 36 thus encompasses the outer contour of the rotor body 4 in the area of the flanged collar 44 in a radially and tangentially form-fitting manner.

According to the method, the space between the surface magnets 16 is thus used for the targeted introduction of the assembly forces. Since the retaining ring 20 is radially somewhat smaller than the outer circumference of the rotor body 4, and there is no surface magnet 16 in the axial direction at this point, the material of the protective sleeve 36 is deformed both radially and axially in the course of forming with the crown tool 46 free areas 42 displaced, resulting in less bulking of the material in the radial direction. In particular, the material is pushed axially downwards, that is to say in the direction of the end face 22b, into the free area, as a result of which radial bulking of the material is reduced. The bulging material in these areas 42 does not impair the electric motor or the air gap, since the distance from the stator in these areas 42 is significantly greater than in the area of the bulges 40 . According to the method, a radial bulking of the protective sleeve 36 is thus deliberately effected or accepted only in the areas 42 in which the radial distance from the stator is greater. The claimed invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived from this by the person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all of the individual features described in connection with the various exemplary embodiments can also be combined in other ways within the scope of the disclosed claims, without departing from the subject matter of the claimed invention. The crown tool 46, for example, is also inventive on its own and thus represents an invention in its own right.

Reference List

2 rotors

4 rotor body

rotor package

8 Motor shaft 10 Through opening 12 Lateral surface 14 Contact surface 16 Surface magnet 18 Holding device 20 Retaining ring

22a, 22b end face 24 ring body 26 circular ring opening

28 tooth process 30 retaining contour 32 attachment extension 34 recess 36 protective sleeve 38 chamfer 40 curvature

42 area

43 stamp 44 flared collar

46 crown tool

48 tool bodies

50 crown wreath

52 recess 54 pinnacle extension

56 forming nose

58 distance

59 stamps A axial direction

R radial direction

T tangential direction

Claims

Expectations

1. Rotor (2) for an electric motor, having

- a rotor body (4) with a cylindrical rotor stack (6) and with a number of surface magnets (16) which are distributed on a lateral surface (12) of the rotor stack (6) as rotor poles and which have a cross-sectional shape in the form of a loaf of bread with a Having a convex curvature (40) orientated on the outer circumference, and

- a sleeve-like protective sleeve (36) which is placed on the outer circumference of the rotor body (4),

- wherein the protective sleeve (36) has a flared collar (44) at least on one end face, which fits positively and/or non-positively into the radially drawn-in areas (42) between the bulges (40) of tangentially adjacent surface magnets (16). is reshaped.

2. Rotor (2) according to claim 1, characterized in that the rotor body (4) has a holding device (18) placed on the end face of the rotor core (6) for the non-bonding attachment and/or holding of the surface magnets (16) on the lateral surface (12) of the rotor core (6), the bulges (40) of the surface magnets (16) projecting radially over the outer circumference of the holding device (18).

3. A method for producing a rotor (2) according to claim 1 or 2,

- wherein a rotor body (4) with a cylindrical rotor stack (6) and with a number of surface magnets (16), which are distributed on a surface area (12) of the rotor stack (6) as rotor poles, and which have a loaf-shaped cross-sectional shape with a have a convex curvature (40) oriented towards the outer circumference, and a sleeve-like protective sleeve (36) for receiving the rotor body (4) are provided,

- wherein the rotor body (4) is inserted into the protective sleeve (36), and - wherein a front flanged collar (44) of the protective sleeve (36) is positively and/or non-positively fitted into the radially constricted areas (42) between the bulges (40) of tangentially adjacent surface magnets (16) by means of a crown tool (46). is reshaped.

4. The method according to claim 3, wherein the protective sleeve (36) has a radially widened chamfer (38) on the front side as an insertion aid for the rotor body (4), characterized in that the rotor body (4) via the chamfer (38) into the protective sleeve (36 ) is introduced, and the chamfer (38) before the forming of the flanged collar

(44) is bent radially inwards by means of a first punch (43).

5. The method according to claim 3 or 4, characterized in that the flanged collar (44) is pressed after its deformation by means of a second stamp (59) on the outer circumference of the rotor body (4).

6. Device for fixing a rotor (2) according to claim 1 or 2, comprising a crown tool (46) which is provided and set up for this purpose in a flanged collar (44) of a protective sleeve (36) in a positive and/or non-positive manner to reshape radially constricted areas (42) between bulges (40) of tangentially adjacent surface magnets (16) of a rotor body (4).

7. The device according to claim 6, characterized in that the crown tool (46) has a cylindrical tool body (48) with a front crown rim (50) for forming the flanged collar (44), and with a cylindrical extension (52), the extension

(52) engages in a feed-through opening (10) of the rotor body (4) in the course of the reshaping.

8. Device according to claim 7, characterized in that the crown rim (50) has a number of axially upstanding pinnacle extensions (54) which are arranged tangentially distributed along the tool body perimeter.

9. The device according to claim 8, characterized in that each pinnacle extension (54) has a radially inwardly directed deforming nose (56).

10. Electric motor for a motor vehicle, having a rotor (2) according to claim 1 or 2.