CN116918218A - Rotor for an electric motor - Google Patents

Abstract

The invention relates to a rotor (2) for an electric motor, comprising: a rotor body (4) having a cylindrical rotor stack (6) and a plurality of surface magnets (16) which are arranged as rotor poles in a distributed manner on the circumferential side (12) of the rotor stack (6) and which have a strip-shaped bread-shaped cross-sectional shape with a convex curvature (40) oriented towards the outer circumference; and a sleeve-shaped jacket (36) which is placed on the outer circumference of the rotor body (4), wherein the jacket (36) has a crimp ring (44) at least on the end face, which is shaped and/or force-locked into a radially retracted region (42) between the arches (40) of the tangentially adjacent surface magnets (16).

Description

Rotor for an electric motor

Technical Field

The invention relates to a rotor for an electric motor, the rotor having: a rotor body having a rotor stack of cylinders and a plurality of surface magnets; and a sleeve-shaped sheath disposed on the outer circumference of the rotor body. The invention also relates to a method and a device for manufacturing such a rotor, and an electric motor having such a rotor.

Background

In modern motor vehicles, electric motors are used in a wide variety of ways as drives for different adjusting elements. For example, electric motors are used as window lifters, sliding roofs or seat adjustment drives, as steering drives (EPS), as radiator fan drives or as transmission actuators. Such electric motors must have a relatively high torque or power density and be safe to operate even at high temperatures.

An electric motor as an energy converter for converting electric energy into mechanical energy comprises a stator forming a stationary motor part and a rotor forming a moving motor part. In an internal rotor motor, the stator is usually provided with a stator yoke on which stator teeth are arranged which project radially towards the centre (which means that the star extends inwards), the free ends of the stator teeth facing the rotor forming so-called pole shoes.

In particular brushless electric motors as (rotary current) electric machines generally have a stator provided with a magnetic field or stator windings, which stator is arranged coaxially with a rotor having one or more permanent magnets.

The rotor typically has a rotor body with a stamped stack of (rotor) laminations of a cylinder as the rotor stack in the center. The rotor stack is in this case fixedly coupled, for example, with respect to the shaft, to the motor shaft of the electric motor. For example, the rotor stack has a receptacle 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 the outer circumference of the circumferential side of the rotor stack. For this purpose, it is conceivable, for example, for the surface magnets to be bonded to the peripheral side face in a material-locking manner, in particular by means of an adhesive or epoxy. It is also conceivable to fasten and/or hold the surface magnets to the peripheral side surface without a material bond using a holding device.

The surface magnets have here conventionally a cross-sectional shape of a bread-loaf shape. In other words, the permanent magnets of the rotor are implemented as surface-mounted elongated bread-shaped magnets. The cross-sectional shape of the bread shape is understood here and in the following to be in particular the shape of a bread with a rectangular shape, wherein the long sides are formed convexly and convexly outwards. The outer circumference of the rotor body does not have a circular shape due to the curvature of the surface magnets.

In operation of the electric motor, a greater centrifugal force acts on the surface magnets of the rotor due to the high rotational speed, thereby increasing the risk of undesired loosening of the surface magnets from the circumferential side. In order to prevent the surface magnets from coming loose from Zhou Cemian and to prevent blocking of the electric motor in the gap area between the rotor and the stator, a sleeve-like jacket (protective tube) is usually placed over the rotor body as a slinger-proof protection.

Typically, the edge of the jacket is bent radially inwards (crimped) here over a complete turn for fastening on the rotor body, so that the end face of the rotor body is axially snapped by the jacket. The shaping or crimping is carried out here, for example, by means of rolling or pressing.

During rolling or rolling, the material of the jacket deforms throughout the entire revolution. Because the sleeve to be deformed is not held completely round by the rotor stack due to the curvature of the surface magnets, the material of the sleeve may be partially too tightly bound during the rolling process, whereby crack formation may occur and an accompanying reduction in the mechanical stability of the sleeve may occur.

During pressing, the round tool is pressed from above against the end face of the jacket or rotor body. In this case, relatively high forces are required, so that the resulting mechanical (compressive) stresses can lead to bulging of the jacket, i.e. to compressed bulges, arches or bulging, whereby the material of the jacket moves radially into the air gap between rotor and stator.

A sheath for a rotor is known from DE 10 2019 205 993 A1, which has a crimp ring crimped for fastening to the rotor body end face. The crimping ring has a plurality of tangentially and axially extending recesses, by means of which stresses occurring during crimping are reduced.

Disclosure of Invention

The object of the present invention is to specify a particularly suitable rotor for an electric motor and a corresponding electric motor. The object of the invention is also to specify a particularly suitable method and a particularly suitable device for producing such a rotor. In particular, inexpensive and cost-effective assembly of the rotor should be possible, wherein the necessary assembly forces are reduced.

According to the invention, this object is achieved with the features of claim 1 in respect of the rotor and of claim 3 in respect of the method and of claim 6 in respect of the device and of claim 10 in respect of the electric motor. Advantageous embodiments and improvements are the subject matter of the dependent claims.

The rotor according to the invention is suitable for and designed as an inner rotor for an electric motor, in particular an SPM (Surface Permanent Magnet (surface permanent magnet)) motor of a motor vehicle. In other words, the rotor according to the invention is constructed in particular as an SPM rotor.

The rotor has a rotor body, which is fixedly coupled or can be coupled to the motor shaft relative to the shaft. The rotor body has a rotor stack of cylinders, which is configured, for example, as a punched stack of laminations (rotor lamination stack) with a plurality of rotor plates stacked in the axial direction. A plurality of permanent-magnet surface magnets are distributed on the outer circumference of the circumferential side of the rotor stack as rotor magnets or pole magnets. The surface magnets have a cross-sectional shape of the shape of a long strip of convex curvature facing outwards Zhou Dingxiang. In particular, the rotor stack has an equilateral polygonal or polygonal base surface, so that the circumferential side has several contact surfaces for the surface magnets with the same surface area along the circumference in the tangential or azimuthal direction.

In order to protect the surface magnets from being thrown out, a sleeve-like jacket is arranged on the outer circumference of the rotor body. According to the invention, the sheath has a crimp ring at least on the end face, which is positively and/or non-positively deformed into the radially retracted region or flank between the arches of the tangentially adjacent surface magnets. A particularly suitable rotor is thereby achieved.

According to the invention, the space between the surface magnets is thus used to fasten the sheath to the rotor body. As a result of the greater distance between the rotor body and the surrounding stator in these regions than in the region of the curvature (or the apex thereof), the material of the jacket bulges (compressed bulges, arches, bulges) as a result of the deformation, without interfering with the air gap or the electric motor.

In contrast to the prior art, the end-side crimp edge or crimp ring of the jacket is thus not completely shaped in full circle, but only at the locations arranged between the arches. According to the invention, the non-circular peripheral shape of the rotor body is thus used to fasten the sheath.

The term "and/or" is understood here and in the following to mean that the features associated with the term can be formed either jointly or alternatively to one another.

In this context and in the following, a "form-fitting" or "form-fitting connection" between at least two mutually connected parts is understood to mean, in particular, that the mutually connected parts are held together at least in one direction by the contours of the parts themselves being directly or indirectly by means of additional connecting parts. Thus, "blocking" the mutual movement in this direction occurs due to the shape.

In this context and in the following, a "force-locking" or "force-locking connection" between at least two mutually connected parts is understood to mean in particular that the mutually connected parts are prevented from sliding relative to one another due to the frictional forces acting between them. If this friction force is caused to be lost in the "connecting force" (which means that the force pressing the parts against each other, for example the screw force or the force of gravity itself) is lost, so that the force-locking connection cannot be maintained and thus a release can occur.

An "axial" or "axial direction" is understood here and in the following to mean in particular a direction parallel (coaxial) to the rotational axis of the electric motor, i.e. perpendicular to the end face of the rotor. Accordingly, "radial" or "radial direction" is understood here and in the following to mean, in particular, a direction perpendicular (transverse) to the rotational axis of the electric motor along the radius of the rotor or of the electric motor. "tangential" or "tangential direction" is understood here and in the following to mean in particular a direction along the circumference of the rotor (circumferential direction, azimuthal direction), i.e. 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 arranged on the end face of the rotor stack and serves to fasten and/or hold the surface magnets to the circumferential face of the rotor stack without a material bond. The curvature of the surface magnets protrudes radially beyond the outer circumference of the holding device. In other words, the curvature of the surface magnets forms the radially outermost point of the rotor body. Since the holding device is thus smaller and there are no magnets in the axial direction in the region between the arches, the material of the sheath can also be pushed into this free region downwards, i.e. axially away from the reshaped end face, during reshaping, which results in less bulging of the material in the radial direction. In this way, the jacket is fitted in a particularly compact manner to the rotor body 4, so that in the installed state, an air gap is realized between the rotor and the stator which is as uniform as possible.

In this context and in the following, a "material-locking" or "material-locking connection" between at least two mutually connected parts is understood to mean, in particular, that the mutually connected parts are held together on their contact surfaces by material bonding or crosslinking (for example due to atomic or molecular bonding forces), if appropriate under the influence of additives. Thus, "no material locking" means in particular that there is no material locking between the surface magnet and the peripheral side surface when the surface magnet is fastened. The surface magnets are therefore fastened to the rotor stack in a form-locking and/or force-locking manner only by means of the retaining device.

The holding device has, for example, two one-piece, i.e. one-piece or one-piece holding rings (insulating disks) which are arranged on opposite end sides of the rotor stack. These retaining rings, which are embodied, for example, as injection molded parts, each have a ring-shaped ring body with a radially outer retaining contour which projects axially in the direction of the rotor stack.

The retaining ring is made in particular of a glass-fiber-reinforced plastic material, for example of Polyamide (PA), in particular PA 6.6GF30, or of polyphenylene sulfide (PPS), in particular PPS GF30, or of Polyoxymethylene (POM), in particular POM GF 30. The abbreviation GF30 here means a glass fiber content of 30%.

The retaining contour is designed such that it engages radially and tangentially in a form-locking manner between the surface magnets. The surface magnets are thereby held on the circumferential side in a non-material-locking manner in the radial direction and in the tangential direction. For axial fixing of the surface magnet, it is provided, for example, that the surface magnet is axially clamped between two retaining rings. For this purpose, the surface magnets are radially covered at least in sections by means of the ring body. In particular, an axial form-locking is thus achieved between the retaining rings.

The geometry required for holding and/or fastening the surface magnets is therefore provided only on the holding device, whereby the rotor stack can have a geometrically particularly simple design. In particular, the rotor stack has no additional receptacles or contours or projections on the circumferential side, so that the rotor sheet and thus the rotor stack can be produced particularly simply and inexpensively. Furthermore, since the permanent magnets are arranged on the circumferential side, the magnetic field lines of the permanent magnets inside the rotor stack are not disturbed.

The method according to the invention is provided for manufacturing the rotor described above, as well as being suitable and designed for use therein. The statements made in connection with the rotor apply here also in the sense of this method and vice versa.

In the case of the method steps described below, an advantageous embodiment of the device is achieved in particular by the device being designed to carry out one or more of these method steps.

According to the method, a rotor body and a jacket are provided. The sleeve-shaped jacket is designed here, for example, essentially as a pot. This means that the jacket has a (jacket body) bottom as an end-side abutment surface for the rotor body. The bottom or abutment surface has, for example, a central recess as a through opening for the motor shaft. The region of the jacket facing the abutment surface is designed as a crimp ring of the jacket and, after the rotor body has been inserted into the jacket, is shaped, crimped or crimped in a form-locking and/or force-locking manner into the radially retracted region between the arches of the tangentially adjacent surface magnets. This means that the assembly force for engaging the jacket with the rotor body is introduced in a targeted manner into the intermediate region between the arches. The required assembly forces are thereby reduced, in particular in the region of the holding device, and substantially no radial protruding deformation of the jacket into the air gap region is achieved, as a result of which the system safety with respect to the electric motor is improved. The method can be used here in essentially all SPM rotors with long bread-shaped magnets, irrespective of the number of poles.

In contrast to the prior art, the shaping or crimping of the sheath is not carried out by rolling or pressing, but rather essentially by caulking in the middle region of the sheath. In other words, the material of the sheath is tied inwardly in the intermediate region in a targeted or partial manner and thus is pressed against the non-circular outer contour of the rotor body.

In a suitable development, the sheath has a chamfer that expands radially on the end face as an introduction aid for the rotor body. In other words, the jacket has an overdimensioning at the end face which protrudes into the air gap, so that the rotor body can be inserted in a funnel-shaped manner. Thereby simplifying the process of inserting the rotor body into the sheath. The rotor body is introduced into the jacket via the chamfer, wherein the chamfer is then bent or directed radially inwards by means of a first die before the crimp ring is reshaped. This means that the first stamp bends the overscaled portion of the sheath extending into the air gap radially inwards. The curved chamfer forms here, for example, a crimp ring for a subsequent shaping or crimping step.

In a suitable embodiment, the crimp ring is pressed onto the outer circumferential side of the rotor body by means of a second pressing die immediately after the crimp ring has been reshaped. This allows for the case that the material of the jacket is pressed away in the region of the curvature, either by reshaping or by crimping. In other words, the curvature is essentially applied to the inner circumference of the sheath prior to the reshaping process, wherein the sheath lifts off from the curvature as a result of the reshaping process. This means that, due to the deformation of the jacket, a (radial) clear distance is formed between the curvature and the jacket. The jacket is thus radially reshaped into the air gap in the region of the curvature. This deformation in the region of the curvature is to be eliminated with a subsequent second stamping process, and the jacket is thus pressed or pressed again onto the surface magnets in the region of the curvature. This ensures that the jacket does not bulge out into the air gap without being permitted.

The advantages and embodiments listed in relation to the rotor and/or the method can also be transferred in a meaning to the device described below and vice versa. The apparatus according to the invention is provided for manufacturing the rotor described above and is suitable for and set up for this purpose. The device has a crown tool which is provided and designed to positively and/or non-positively shape the crimp ring of the jacket into the radially retracted region between the arches of the tangentially adjacent surface magnets of the rotor body. The apparatus also has, for example, a first and a second stamper. A particularly suitable device is thereby achieved.

The crown tool of the device therefore does not deform the sheath tangentially in full turns, but only in a point-wise or local manner at the free space between the rotor body and the sheath, which is left by the curvature.

In a suitable embodiment, the crown tool has a cylindrical tool body with a crown flange on the end face facing the rotor. The crown flange is configured here for reshaping or deforming the crimp ring. Furthermore, a central projection is provided on the tool body, which projection engages into the through opening of the rotor body during the reshaping process. The through opening of the rotor body is used in the mounted state for accommodating the rotor shaft or the motor shaft. The projections, for example, of the pins or cylinders, engage in a form-locking manner, for example, in the central through-opening, so that the rotor body is positioned, stabilized and centered during the reshaping process. The crown flange and the projection are integrally, i.e. one-piece or integrally, formed to the tool body. The projection is embodied here, for example, as a pin or a peg of the tool body. For reshaping, the crown tool is lowered in a compression-molded manner from above to the end face of the rotor body equipped with the sheath, wherein the projections are embedded in the through-openings, and wherein the crown flange locally reshapes, calks or crimp the crimp ring.

In a conceivable embodiment, the crown flange has a number of axially upstanding protruding crown projections or battlement projections arranged tangentially along the circumference of the tool body. Preferably, each battlement-like projection has a radially inwardly directed reshaping nose therein which reshapes the crimp ring during the reshaping process. A particularly suitable tool is thereby provided and thus a particularly suitable apparatus for manufacturing a rotor is achieved.

In a preferred application, the rotor described above is part of an electric motor. The electric motor according to the invention is suitable for use in, for example, and is designed for, a power steering of a motor vehicle. The advantages and embodiments listed with respect to the rotor and/or the method and/or the device can also be transferred to the electric motor in a meaning and vice versa.

The electric motor has a stator and a motor shaft rotatably supported relative to the stator, and the rotor is fixedly supported on the motor shaft relative to the shaft. For example, the electric motor is here embodied as a brushless electric motor of the inner mover type.

In the case of an application for power steering, the electric motor is arranged in the region of the cockpit, wherein particularly quiet motor operation is ensured by the rotor according to the invention, since the surface magnets and the jacket are held on the rotor stack without vibration. The noise generation of the electric motor is thereby advantageously and simply reduced, which advantageously translates into a user comfort of the motor vehicle.

Drawings

Embodiments of the present invention will be explained in more detail hereinafter with reference to the drawings. Wherein:

FIG. 1 shows a perspective view of a rotor in a partially disassembled state;

FIG. 2 shows a perspective exploded view of the rotor;

fig. 3 shows a top view of the rotor in a preassembled state;

fig. 4 shows a first die for producing a rotor in perspective;

fig. 5 shows a perspective view of the rotor end side after machining with the first press according to fig. 4;

FIG. 6 shows a crown tool for manufacturing a rotor;

FIG. 7 shows a perspective view of the rotor end side after machining with the crown tool according to FIG. 6;

fig. 8 shows a second die for manufacturing a rotor in perspective;

fig. 9 shows a perspective view of the rotor end side after machining with a second press according to fig. 8; and

fig. 10 shows a side view of the rotor.

In all figures, parts and dimensions corresponding to each other are always provided with the same reference numerals.

Detailed Description

Fig. 1 shows a rotor 2 of an electric motor, which is not shown in detail. The electric motor, which is configured as a brushless inner rotor, is part of an electric motor-type power steering of a motor vehicle. Rotor 2 has a rotor body 4 with a rotor stack 6 of generally cylindrical shape fixedly engaged with a motor shaft or rotor shaft 8 with respect to the shaft. In the assembled state, the motor shaft 8 and thus the rotor 2 are rotatably supported relative to the stationary stator of the electric motor. In the assembled state, an annular air gap is formed between the outer periphery of the rotor 2 and the inner periphery of the stator.

Fig. 2 shows the rotor 2 in an exploded view in a disassembled state. As can be seen relatively clearly in the exploded view of fig. 2, the rotor stack 6 has in this embodiment an equilateral, decagonal base. The rotor stack 6 is formed here from a plurality of rotor plates, which are not shown in detail, which are stacked in an axial direction a into a stack (rotor stack) and punched out. The rotor stack 6 has a central through opening 10 for receiving the motor shaft 8. The rotor stack 6 also has a peripheral side 12 extending in the axial direction a on the peripheral side, which is formed with ten contact surfaces 14 of the same type, corresponding to the bottom surface. The abutment surface 14 is provided with reference numerals in the figures for example only.

In the present embodiment, the rotor 2 is implemented as an SPM rotor having ten permanent magnet surface magnets 16. They are used to generate an excitation magnetic field. The surface magnets 16, which are only exemplary provided with reference numerals, are arranged here distributed over the circumference of the circumferential side 12 in the tangential or azimuthal direction T on the rotor stack 6. The surface magnets 16 are configured as strip-shaped magnets and each have a substantially strip-shaped cross-sectional shape in the axial direction a, wherein the surface magnets 16 are arranged in a position on the respective associated contact surfaces 14 of the peripheral side surfaces 12. In the assembled state of the rotor 2, the surface magnets 16 are held and/or fastened to the circumferential side 12 of the rotor stack 6 by means of the holding device 18 without a material bond.

The holding device 18 has two holding rings or insulating discs 20. As can be seen relatively clearly from fig. 1 and 2, the retaining rings 20 are placed in the engaged or assembled state on opposite end sides 22a, 22b of the rotor stack 6. The retaining rings 20 here each have an annular ring body 24. For the motor shaft 8 to pass through, a central annular opening 26 is introduced into the ring body 24. In the illustrated embodiment, the ring body 24 has a generally star-shaped cross-sectional shape or inner contour along the radially inner circumference of the radial direction R, i.e., the inner wall of the annular opening 26. The star-shaped cross-sectional shape of the inner wall is formed here by ten radially inwardly projecting tooth projections 28 of the ring body 24. The tooth projections 28 are provided with reference signs in the figures only by way of example.

On the underside facing the rotor stack 6, the ring body 24 has ten retaining contours 30 on the outer circumference side and ten fastening projections 32 on the inner circumference side. The retaining profile 30 and the fastening projection 32 are shaped so as to protrude axially from the underside of the ring body 24. The retaining contours 30 are arranged uniformly distributed along the circumference of the ring body 24. The fastening projections 32 are arranged distributed along the inner circumference, wherein the fastening projections 32 are formed in one piece, i.e. in one piece or in one piece, in particular in the region of the respective radially inner tooth end of the tooth projection 28.

As can be seen for example in the illustration of fig. 3, the distribution of the retaining profiles 30 and the fastening projections 32 relative to one another is arranged such that the fastening projections 30 are each arranged between two adjacent retaining profiles 32 in the tangential direction T.

In order to reduce the moment of inertia of the rotor 2, the rotor stack 6 is provided with 10 recesses 34 through the stack. The recesses 34 are arranged uniformly distributed in the tangential direction T around the central through opening 10. The recess 34 is provided with reference signs in the figures only by way of example.

As can be seen in particular in fig. 3, the recess 34 has a substantially drop-shaped cross-sectional shape in the axial direction a. In the assembled state, the fastening projections 32 of the ring body 24 engage in the recesses 34. In this case, the drop shape of the recess 34 acts as a centering aid when the retaining ring 20 is engaged with the rotor stack 6. This means that the retaining ring 20 is at least partially inserted axially into the rotor stack 6 by means of the fastening projections 32.

The retaining profile 30 arranged radially outside in the radial direction R has a substantially trapezoidal cross-sectional shape in the axial direction a. The base of the cross-sectional shape is oriented in the tangential direction T, the radially inner base having a shorter dimension than the radially outer base. The waist side extending between the bottom edges is here inclined with respect to the tangential direction T and extends inclined with respect to the radial direction R.

As can be seen in particular in fig. 3, the distribution of the retaining contours 30 is arranged such that the retaining contours 30 are arranged in the corner regions of the decagonal rotor stack 6. In other words, the retaining contour 30 is arranged in the corner region between two adjacent abutment surfaces 14. The recess 34 is oriented approximately centrally with respect to the respective contact surface 12 in the radial direction R.

As can be seen relatively clearly in the top view of fig. 3, a substantially three-point fastening is thus achieved for each surface magnet 16 by means of the retaining ring 20. The waist side of the holding contour 30 rests on the radially outer contour of the surface magnets 16, so that the surface magnets 16 are at least partially tangentially and radially clamped in these rest areas. This means that the surface magnets 16 are held in a form-locking manner in the tangential direction T and in the radial direction R by means of the holding profile 30, wherein a torsion-proof protection or torsion-proof of the surface magnets 16 on the circumferential side 12 is achieved by the insertion of the fastening projections 32 into the recesses 34. The surface magnets 16 are covered at least in sections in the radial direction R by the ring body 24 of the retaining ring 20 at the end sides 22a, 22b of the rotor stack 6. Thus, the surface magnets 16 are positively clamped between the retaining rings 20 in the axial direction a.

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

Hereinafter, a method for manufacturing the rotor 2, in particular for fastening the jacket 36 to the rotor body 4 by means of a device not shown in detail, will be explained in more detail with reference to fig. 3 to 10.

In a first method step, the rotor body 4 is inserted into the sheath 36. For this purpose, the jacket 36 has, for example, a radially open chamfer 38 (fig. 1) on the end face facing the rotor body 4 as an introduction aid. The chamfer 38 has a radial oversize extending into the air gap, so that the rotor body 4 can be introduced into the jacket 36 in a funnel-shaped manner.

As can be seen in particular in fig. 3, the surface magnets 16 have a convex curvature 40 toward the outer periphery. In this case, the curvature 40 of the surface magnet 16 protrudes radially beyond the outer circumference of the ring body 24. In other words, the curvature 40 of the surface magnets 16 forms the radially outermost point of the rotor body 4. The outer circumference of the rotor body 4 therefore does not have a circular (outer) shape or (outer) contour due to the curvature 40 of the surface magnets 16. The sheath 36 has a substantially circular cross-sectional shape, which rests on the inner circumference on the apex of the curvature 40. Thereby ten peripherally distributed areas 42 or free spaces are formed between the jacket 36 and the flanks of each two tangentially adjacent surface magnets 16 as a clear distance between the outer circumference of the rotor body 4 and the inner circumference of the jacket 36.

After insertion of rotor stack 4 into jacket 36, chamfer 38 is bent or pointed radially inward by means of (first) die 43 shown in fig. 4 (fig. 5). This means that the stamp 43 bends the overscaled penetration of the sheath 36 into the air gap radially inwards. For this purpose, the substantially cylindrical stamp 43 has a circular depression on the end side, which depression has a chamfer-like inclined side wall. As the die 43 descends, the chamfer 38 of the jacket 36 is pressed onto the outer circumference of the rotor stack 4 by means of a suitable side wall.

In the next method step, the crimp ring 44 (crimp edge) of the end face of the jacket 36 is reshaped. The crimp ring 44 is an axial section of the end face of the jacket 36, which includes, for example, the chamfer 38 that is pointed. The unmodified crimp ring 44 projects here at least partially axially from the inserted rotor body 4. In the illustrations of fig. 5, 7 and 9, the (unmodified) crimp ring 44 has, for example, an overrun of less than 15mm (millimeters), in particular less than 10mm, for example about 5 mm.

After the rotor body 4 has been inserted into the jacket 36, the crimp ring 44 is deformed, crimped or crimped in a form-locking and/or force-locking manner into the radially retracted regions 42 between the arches 40. This means that the assembly force for engaging the jacket 36 with the rotor body 4 is introduced in a targeted manner into the intermediate region. In other words, the free space or free surface formed between the flanks of the arches 40 is used as an action point for the reshaping tool. This means that the surface of the jacket 36 in the region 42 as a partial caulking surface is deformed or crimped radially inwards.

To reshape the crimp ring 44, the apparatus has a crown tool 46 as a reshaping die. The crown tool 46 of the device, which is shown separately in fig. 6, has a cylindrical tool body 48 with a crown flange 50 facing the rotor 2 on the end side and a central recess 52 for a projection, not shown in detail.

The projections of the pin shape or the cylinder are inserted into the recesses 52, for example as pins or studs. Alternatively, the projection may also be integrally formed onto the tool body 48. The diameter of the projection is here slightly smaller than the inner diameter of the through opening 10.

Crown flange 50 has ten crown projections or battlement projections 54 arranged circumferentially side-by-side. The battlement-like projections 54 each have radially inwardly directed modified lugs 56. The reshaping nose 56 has an axially inclined ramp as a reshaping profile for the crimp ring 44.

For reshaping, the crown tool 46 is lowered in the form of a die onto the rotor body 4 equipped with the jacket 36 in the direction of the end side 22 a. The projections engage in the through-openings 10, so that the rotor body 4 and the crown tool 46 are centered and oriented in axial alignment with one another. As crown tool 46 is lowered, crimp ring 44 is reshaped, swaged, or crimped into region 42 by means of reshaping nose 56.

By means of crown tool 46, the upper edge of crimping ring 44 is crimped radially inward into region 42, so that retaining ring 20 (and thus rotor body 14) is at least partially axially engaged by crimping ring 44 in region 42.

Fig. 7 shows an observation of the end side of the rotor 2 after a reshaping process by means of a crown tool 46. As can be seen relatively clearly in fig. 6, the material of the jacket 36 is pressed or lifted off as a result of the reshaping in the region of the curvature 40. In other words, the net distance 58 is formed in the centrally located region of the curvature 40 due to the reshaping in the region 42. The jacket 36 is thereby deformed radially into the subsequent air gap between the rotor 2 and the stator in the region of the curvature 40 or in the region of the distance 58.

In order to reduce the distance 58, the crimp ring 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) die 59 shown in fig. 8. The stamp 59 is implemented in a similar manner to the stamp 43, the central depression of the stamp 59 being implemented deeper than the depression of the stamp 43. For example, the diameter of the recess in the case of the stamper 43 is larger than the diameter of the recess in the case of the stamper 59. For example, the pressing dies 43 and 59 also have a recess 52 for a projection that engages into the through opening 10 during the lowering. Fig. 9 and 10 show the rotor 2 in the engaged state after a third method step.

By means of the (second) die 43, the material of the jacket 36 is pressed from the outside onto the rotor body 4 in the region of the crimp ring 44, so that the distance 58 is substantially reshaped to zero. In other words, the jacket 36 or the crimp ring 44 is held against the outer peripheral side of the curvature 40. The jacket 36 thus engages the outer contour of the rotor body 4 in a radially and tangentially positive manner in the region of the crimp ring 44.

According to this method, the space between the surface magnets 16 is thus used for targeted introduction of the assembly force. Since the retaining ring 20 is smaller radially than the outer circumference of the rotor body 4 and in this position no surface magnets 16 are in abutment in the axial direction, during the shaping with the crown tool 46 the material of the jacket 36 is pushed both radially and axially into the free region 42, which results in less bulging of the material in the radial direction. In particular, the material is pushed axially downward, i.e. in the direction of the end face 22b, into the free region, as a result of which the radial expansion of the material is reduced. The bulging material does not damage the electric motor or the air gap in these areas 42, since the distance to the stator is much greater in these areas 42 than in the region 40 of the camber. According to this method, radial bulging of the jacket 36 therefore takes place or is taken into account specifically only in the region 42 with a large radial distance from the stator.

The claimed invention is not limited to the embodiments described above. Rather, other variations to the invention can be derived by those skilled in the art within the scope of the claims disclosed without departing from the inventive subject matter. In particular, all the individual features described in connection with the different 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.

Thus, the crown tool 46 itself is, for example, also inventive and is thus an invention itself.

List of reference numerals

2. Rotor

4. Rotor body

6. Rotor stack

8. Motor shaft

10. Through opening

12. Peripheral side surface

14. Surface for sticking

16. Surface magnet

18. Holding device

20. Retaining ring

22a, 22b end sides

24. Ring body

26. Circular ring opening

28. Tooth bulge

30. Retaining profile

32. Fastening projection

34. Blank part

36. Sheath

38. Chamfering edge

40. Arch part

42. Region(s)

43. Compression mould

44. Crimping ring

46. Crown tool

48. Tool body

50. Crown flange

52. Blank part

54. Battlement-shaped bulge

56. Modified nose

58. Spacing of

59. Compression mould

Aaxial direction

R radial direction

T tangential direction

Claims (10)

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

-a rotor body (4) with a rotor stack (6) of cylinders and a number of surface magnets (16) arranged as rotor poles distributed over a circumferential side (12) of the rotor stack (6), and having an elongated bread-shaped cross-sectional shape with convex arches (40) oriented towards the outer circumference, and

a sleeve-shaped sheath (36) placed on the outer circumference of the rotor body (4),

-wherein the sheath (36) has a crimp ring (44) at least at the end face, which is positively and/or non-positively deformed into a radially retracted region (42) between the arches (40) of the tangentially adjacent surface magnets (16).

2. The rotor (2) according to claim 1,

it is characterized in that the method comprises the steps of,

the rotor body (4) has a holding device (18) which is placed on the end face on the rotor stack (6) and serves to fasten and/or hold the surface magnets (16) to the circumferential face (12) of the rotor stack (6) without a material-locking manner, wherein the arches (40) of the surface magnets (16) protrude radially beyond the outer circumference of the fastening device (18).

3. Method for manufacturing a rotor (2) according to claim 1 or 2,

-wherein a rotor body (4) is provided having a cylindrical rotor stack (6) and a plurality of surface magnets (16) which are arranged as rotor poles distributed on a circumferential side (12) of the rotor stack (6) and which have an elongated bread-shaped cross-sectional shape with a convex curvature (40) oriented towards the outer circumference, and a sleeve-shaped jacket (36) is provided for accommodating the rotor body (4),

-wherein the rotor body (4) is inserted into the sheath (36) and

-wherein the end-side crimp ring (44) of the sheath (36) is positively and/or non-positively deformed by means of a crown tool (46) into the radially retracted region (42) between the arches (40) of the tangentially adjacent surface magnets (16).

4. A method according to claim 3, wherein the jacket (36) has a chamfer (38) which expands radially on the end face as an introduction aid for the rotor body (4),

it is characterized in that the method comprises the steps of,

the rotor body (4) is introduced into the jacket (36) via the chamfer (38), and the chamfer (38) is bent radially inwards by means of a first die (43) before the crimp ring (44) is shaped.

5. The method according to claim 3 or 4,

it is characterized in that the method comprises the steps of,

immediately after the shaping of the crimp ring, the crimp ring (44) is pressed onto the outer circumferential side of the rotor body (4) by means of a second pressing die (59).

6. Device for producing a rotor (2) according to claim 1 or 2, having a crown tool (46) which is provided and designed for positively and/or non-positively reshaping a crimp ring (44) of a jacket (36) into a radially retracted region (42) between arches (40) of tangentially adjacent surface magnets (16) of a rotor body (4).

7. The apparatus according to claim 6,

it is characterized in that the method comprises the steps of,

the crown tool (46) has a cylindrical tool body (48) with a crown flange (50) for shaping the crimp ring (44) at the end face and with a cylindrical projection (52), wherein the projection (52) engages in the through-opening (10) of the rotor body (4) during the shaping process.

8. The apparatus according to claim 7,

it is characterized in that the method comprises the steps of,

the crown flange (50) has a plurality of axially upstanding lugs (54) arranged tangentially along the periphery of the tool body.

9. The apparatus according to claim 8,

it is characterized in that the method comprises the steps of,

each battlement-like projection (54) has a radially inwardly directed modified nose (56).

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