Electric motor device for driving a sunroof or a roller blind in a vehicle

Abstract

Electric motor device (10) for driving a sunroof (2) or a roller blind in a vehicle (100), comprising: a rotor device (20) comprising an at least partially cylindrical outer surface (21); a stator device (30) having a core (31) including a plurality of stator teeth (32) projecting toward the rotor device (20), the stator teeth (32) comprising a tooth root (33) connected to a stator ring (34) and a tooth tip (35) having a wing-shaped tooth shoulder (36) on each side in a circumferential direction, the wing-shaped tooth shoulder (36) having a tip (37) formed at an end portion (47) of the respective wing-shaped tooth shoulder (36) in the circumferential direction; wherein the tooth tip (35) includes a surface (39) facing the at least partially cylindrical outer surface (21) of the rotor device (20) to form a gap (40) therebetween; wherein the surface (39) comprises: - a hollow cylindrical surface section (41) having a constant gap distance (g1) in the direction of the at least partially cylindrical outer surface (21) of the rotor device (20) in the circumferential direction, and - each having an inclined surface portion (42) having an increasing gap distance (g2) with respect to the at least partially cylindrical outer surface (42) of the rotor device (20) in the circumferential direction towards the respective tip (37) formed by the end portion in the circumferential direction; wherein the hollow cylindrical surface portion (41) includes a first radius (r1) with respect to a center axis (C) of the rotor device, and the tip (37) formed at the end portion in the circumferential direction has a second radius (r2) with respect to the center axis (C) of the rotor device (20); wherein a first ratio (r2 / r1) between the second radius (r2) and the first radius (r1) is 1.02 or more and 1.08 or less.

Description

Technical area:

[0001] The present invention relates to an electric motor device for driving a sunroof or a roller blind in a vehicle. Technical background:

[0002] Brushless motors, such as BLDC (brushless direct current) or PMSM (permanent magnet synchronous) motors, are increasingly being used as electric motor devices to drive various components in vehicles, with important implementations involving sunroofs or window shades, for example. Such motors offer several advantageous features over conventional brushed DC motors and other alternatives. For example, compared to brushed DC motors, PMSM motors have fewer components that typically wear out over time. This means that PMSM motors can operate for much longer periods without maintenance.In addition, PMSM motors are generally very efficient as they do not suffer from voltage drops and energy loss, resulting in less battery consumption in vehicles, an essential factor for both conventional and electric vehicles (EVs).

[0003] In addition, PMSM motors incorporate control devices that enable precise control of speed, torque, and position. This precision is especially important for sunroofs, where smooth operation and the ability to stop precisely in positions are critical to user satisfaction and safety. Modern vehicles are becoming increasingly integrated with electronic systems, and PMSM motors are well-suited for integration as part of such systems due to their controllability and the ease with which they can be integrated with electronic control units (ECUs) and sensors.

[0004] Additionally, PMSM motors tend to produce less noise than brushed motors, a significant advantage in the automotive environment, where noise reduction is constantly sought. Furthermore, they generate less electromagnetic interference, which could disrupt the vehicle's electronic systems. Furthermore, PMSM motors tend to be more compact and lightweight without compromising performance. This property is advantageous in automotive applications where space conservation and avoiding significant additional weight to the vehicle are important considerations.

[0005] In general, PMSM motors may comprise a stator device and a rotor device, which are housed together with a respective control device in a common housing. Known concepts of stator devices in brushless DC motors (PMSM motors) provide for a common profile of the stator teeth, see the Fig. 1, wherein a dimension and shape of each tooth includes a tooth tip having a surface facing the rotor device, the tooth tip being completely hollow-cylindrical with edges or end portions arranged on both sides in the circumferential direction of the tooth tip, the edges forming peaks on respective tooth shoulders. Corresponding to an outer cylindrical surface of the rotor, this results in a small gap having a constant width along the circumferential direction.

[0006] Such a stator device 30 comprises, as in a comparative example of Fig. 1, a stator core 31 comprising a stator ring 34 and stator teeth 32 extending from the stator ring 34, and windings 28 of wire wound around the stator teeth 32 and electrically excited under suitable control of the control device (not shown) to drive the rotor device 20.

[0007] The stator teeth 32 each include a tooth root 33 adjacent to the stator ring 34 and a tooth tip 35 opposite the stator ring 34 and projecting radially inward toward the rotor assembly 20. The tooth tip 35 has two shoulder portions 360 formed on either side of the tooth tip 35 in a circumferential direction. In a cross-sectional profile, the two shoulder portions 360 taper toward an end portion 470 that forms a tip 37 at its outermost end in the circumferential direction about a central or rotational axis C of the rotor assembly 20. The tooth tip 35 also has a surface 39 facing an at least partially cylindrical outer surface 21 of the rotor assembly 20. The surface 39 is completely hollow cylindrical and forms a gap 40 which is defined by a constant distance between the surface 39 and the outer surface 21 along the circumferential direction.

[0008] The tip 37 forms an outer edge 371 of the surface 39. Starting from the outer edge 371, an outer contour of the cross-sectional profile of the tooth tip 35 extends in a substantially radial direction away from the center axis C of the rotor device 20, thereby forming a substantially flat, radially oriented surface portion 372. At a radially outer end thereof, the flat, radially oriented surface portion 372 transitions into a curved surface portion 373, which in turn transitions into a flat rear surface of the respective shoulder portion.

[0009] However, the known concept as described above leads to higher noise emissions due to a comparatively high cogging torque.

[0010] Document EP 4 287 463 A1 discloses stator teeth with a curved shape at the outer ends, so that in these areas an inner distance g1 between the rotor circumference and the inner surface of the stator tooth widens to a larger distance g2. In particular, Fig. 2 of this document, a nonlinear curve is described as causing a reduction in torque fluctuations. The stator device in question is part of a fan motor, i.e., a motor designed to produce very low torque at a very high speed. The motor is an asynchronous motor. In particular, the stator tooth disclosed in the document exhibits a relationship of 1.5.g1 < (g2-g1) < 6.g1, where—as mentioned above—g1 is the inner distance between the tooth and the rotor, and g2 is the widened outer distance. However, this parameterization and the corresponding limiting range provide a significant torque reduction, which can be expected to be incompatible with PMSM motors operating at high torque at comparatively low speed.

[0011] Document JP 2017-184451 A2 also discloses stator teeth having a curved shape at the outer ends, so that in these areas the inner distance G1 between the rotor circumference and the inner surface of the stator tooth widens to a larger distance G2 towards the end portions thereof. Description of the invention:

[0012] It is an object to provide an electric motor device that improves known concepts by reducing noise emissions and preferably reduces high cogging torques in the multitude of applications in driving sunroofs or roller blinds in a vehicle.

[0013] According to aspects and embodiments of the invention, an electric motor device for driving a sunroof or a roller blind in a vehicle is provided, comprising a rotor device having an at least partially cylindrical outer surface and a stator device with a core including a plurality of stator teeth projecting towards the rotor device, wherein the stator teeth comprise a tooth root connected to a stator ring and a tooth tip with a wing-shaped tooth shoulder on each side in a circumferential direction, wherein the wing-shaped tooth shoulder has a tip formed at an end portion of the respective wing-shaped tooth shoulder in the circumferential direction.

[0014] The tooth tip includes a surface facing the at least partially cylindrical outer surface of the rotor device to form a gap therebetween, the surface comprising: - a hollow cylindrical surface section having a constant gap distance in the direction of the at least partially cylindrical outer surface of the rotor device in the circumferential direction, and - each having an inclined surface portion having an increasing gap distance with respect to the at least partially cylindrical outer surface of the rotor device in the circumferential direction towards the respective tip forming the end portion in the circumferential direction.

[0015] Furthermore, the hollow cylindrical surface portion includes a first radius (r1) with respect to a center axis of the rotor device, and the tip forming the end portion in the circumferential direction has a second radius (r2) with respect to the center axis of the rotor device, wherein a first ratio (r2 / r1) between the second radius (r2) and the first radius (r1) is a value of 1.02 or more and 1.08 or less.

[0016] In an alternative aspect and an alternative embodiment, which can, however, also be advantageously combined with the first aspects and embodiments, an electric motor device for driving a sunroof or a roller blind in a vehicle is provided, comprising: a rotor device comprising an at least partially cylindrical outer surface, and a stator device having a core including a plurality of stator teeth projecting towards the rotor device, wherein the stator teeth comprise a tooth root connected to a stator ring and a tooth tip with a wing-shaped tooth shoulder on each side in a circumferential direction, wherein the wing-shaped tooth shoulder has a tip formed at an end portion of the respective wing-shaped tooth shoulder in the circumferential direction, wherein the edge portion is defined to have a curved cross-sectional profile,which has a constant radius of curvature.,

[0017] The tooth tip includes a surface facing the at least partially cylindrical outer surface of the rotor device to form a gap therebetween, the surface comprising: - a hollow cylindrical surface section having a constant gap distance in the direction of the at least partially cylindrical outer surface of the rotor device in the circumferential direction, and - each having an inclined surface portion having an increasing gap distance with respect to the at least partially cylindrical outer surface of the rotor device in the circumferential direction towards the respective tip formed by the end portion in the circumferential direction.

[0018] The hollow cylindrical surface portion includes a first radius (r1) relative to a center axis of the rotor device, and a first transition between the inclined surface portion and the edge portion has a third radius (r3) relative to the center axis of the rotor device. A second ratio (r3 / r1) between the third radius (r3) and the first radius (r1) is a value of 1.006 or more and 1.01 or less.

[0019] The proposed electric motor device features a novel stator tooth design. The tooth shoulders, which have end portions with their tips in the circumferential direction, incorporate a vane design in terms of the shape or cross-sectional profile of the tooth edge or end portions. Such a specific shape contributes to creating a variable air gap that reduces the overall amplitude and harmonics of the cogging torque, which in turn contributes to reducing overall noise emissions.

[0020] Particularly with respect to, for example, sunroof applications of the electric motor device in vehicles, particularly automobiles, trucks, construction vehicles, or recreational vehicles, where noise is critical for passengers in a vehicle, a significant improvement can be achieved by embodiments of the invention. That is, the total cogging torque can be reduced by 10% or more, preferably 15% or more, more preferably 20% or more, in one specific embodiment by 21%, which contributes to reducing the overall noise (i.e., both airborne and structurally borne).

[0021] Reduced harmonics during detent also improve high-frequency speed and / or torque fluctuation, resulting in a better subjective noise perception for passengers in a vehicle.

[0022] In terms of cost, it appears that no additional costs or process steps are required to implement the invention in the manufacture and assembly of electric motor devices.

[0023] It should be noted that the invention is not only applicable to sunroof applications, but also to roller blinds, doors or side windows, rear or tailgates in vehicles or to moving components such as sensors or cameras, as present, for example, in roof sensor modules used, among others, in fully or partially autonomous driving.

[0024] Advantageous aspects and embodiments are further provided in the dependent claims.

[0025] Further advantageous aspects and embodiments emerge from the dependent claims. Short description of the drawings: Fig. 1 shows a cross-sectional profile of a stator tooth of a stator device according to the prior art; Fig. 2 shows a cross-sectional profile of a stator tooth of a stator device according to an embodiment; Fig. 3 shows a cross-sectional profile of a stator tooth of a stator device according to an embodiment in greater detail in connection with a first specific parameterization of the tooth shoulder geometry; Fig. 4 shows a cross-sectional profile of a stator tooth of a stator device according to an embodiment in greater detail in connection with a second specific parameterization of the tooth shoulder geometry; Fig. 5 shows a cross-sectional profile of a stator tooth of a stator device according to an embodiment in greater detail in connection with a third specific parameterization of the tooth shoulder geometry; Fig. 6 shows a cogging torque plotted against time with respect to stator devices with the cross-sectional profiles of the tooth shoulder in an electric motor device according to the invention; Fig. Figure 7 shows a maximum cogging torque plotted against time for the three stator devices with the cross-sectional profiles of the tooth shoulder in an electric motor device according to the invention; Fig. 8 shows a cogging torque versus the rotation angle of the rotor for an electric motor according to the prior art; Fig. 9 shows a cogging torque versus the rotation angle of the rotor for an electric motor according to an embodiment of the invention; Fig. 10 is a schematic perspective view of a vehicle in which a sunroof driven by an electric motor device according to embodiments is formed. Description of embodiments:

[0026] In the following description of preferred exemplary embodiments, it should be understood that the present disclosure of the various aspects is not limited to the details of the construction and arrangement of the components as shown in the following description and in the figures. The exemplary embodiments may be practiced or embodied in a variety of ways. Furthermore, it should be understood that the phraseology and terminology used herein is used for the purpose of specific description only and should not be construed as limiting by those skilled in the art.Furthermore, in the following description, identical reference numerals in the various exemplary embodiments or figures indicate identical or similar features or objects, so that in some cases a repeated detailed description thereof is omitted in order to maintain compactness and clarity of illustration.

[0027] An overview of a roof section of a vehicle 100 in which an embodiment according to aspects of the invention can be integrated is shown in Fig. 10. The vehicle 100 includes a windshield 110 and a rear window 120 in the roof section, which is defined by frame parts 130. An opening 1 is formed in the roof section, which opening can be opened or closed by moving a sliding roof 2 (for example, a sunroof) as an example of a movable component. For the purpose of moving or driving the sliding roof 2, an electric motor device 10 is provided in the roof section of the vehicle 100 at a suitable location. In the schematic drawing of Fig. 10, the location of the electric motor device within the roof section is arbitrarily chosen, and any other locations can be selected according to requirements. Also, the sunroof 2 can be a roller blind or any other movable component, such as a side window in a door of the vehicle 100, or a power-driven tailgate or door of the vehicle 100, or a sensor and / or camera component of a roof sensor module forming part of a system that supports autonomous driving, or the like.

[0028] With reference to Fig. 1 and Fig. 2, the electric motor device 10 comprises a housing and a control device, a stator device 30, and a rotor device 20. The housing and the control device are not shown in the figures. The stator device 30, the rotor device 20, and the control device can be accommodated in the housing. The housing is provided with a connector assembly that allows for the plugging in of a power line and a communication line, such as a communication bus, for example, a LIN bus or a CAN bus (not shown). The electric motor device 10 can be a brushless motor device, such as a BLDC or PMSM motor. The control device can receive instructions via the communication line, for example, to control the excitation of an electronic circuit including the windings 38 of the stator device 30.

[0029] Fig. 1 and Fig. 2 shows a comparison between a stator device 30 having a common tooth shoulder profile according to the prior art and a tooth shoulder having a vane shape according to embodiments of the invention. Fig. 1 illustrates the stator device 30 according to the prior art, which was explained above. There, a surface 39, which faces an at least partially cylindrical outer surface 21 of the rotor device 20 across a gap 40, extends completely between and encloses the tips 37 of the end portions of the two shoulder portions 360. Consequently, a distance g1 between a surface 39, which faces an at least partially cylindrical outer surface 21 of the rotor device 20, and this outer surface 21 is completely constant in the circumferential direction.

[0030] Fig. Figure 2 discloses a stator device 30 of an electric motor device 10 according to an embodiment of the invention. For the purpose of brevity, only differences with respect to the prior art are emphasized, while a description of the same or similar features as in Fig. 1 is omitted.

[0031] The electric motor device 10 has the stator device 30, as explained above, in addition to the rotor device 20, the housing, and the control device. The stator device 30 comprises, as shown in Fig. 2, a stator core 31 comprising a stator ring 34 and stator teeth 32 extending from the stator ring 34, and windings 28 of wire wound around the stator teeth 32 and electrically excited under suitable control of the control device (not shown) to drive the rotor device 20.

[0032] The stator teeth 32 each include a tooth root 33 adjacent to the stator ring 34 and a tooth tip 35 opposite the stator ring 34 and projecting radially inward toward the rotor device 20.

[0033] The tooth tip 35 has two shoulder portions 36 that are wing-shaped. The two shoulder portions 36 are formed on both sides of the tooth tip 35 in a circumferential direction. In a cross-sectional profile, the two shoulder portions 36 taper toward an end portion 47, which forms a tip 37 at its outermost end in the circumferential direction about a center or rotational axis C of the rotor device 20. The tooth tip 35 also has a surface 39 that faces an at least partially cylindrical outer surface 21 of the rotor device 20. In this embodiment, the surface 39 is only partially hollow-cylindrical and forms a gap 40 that is defined by a constant distance g1 between the surface 39 and the outer surface 21 along the circumferential direction.

[0034] The wing shape of the shoulders 36 is due to a different design of the end portion 47 of each of the shoulders 36 (the stator teeth in this embodiment are axially symmetric about a radius line extending through the center axis C) compared to the end portions 470 of the shoulders 360 according to the prior art.

[0035] More specifically, the surface 39 includes a hollow cylindrical surface portion 41 and two inclined surface portions 42 sandwiching the inner hollow cylindrical surface portion 41 on both sides thereof in the circumferential direction. Specifically, the inclined surface portions 42 extend between the inner hollow cylindrical surface portion 41 and the respective tips 37 of the shoulders 36. As a result of this design, the tips 37 are not positioned on a general cylindrical plane defined by the inclined surface portions 42, but are located farther from the center axis C than the hollow cylindrical surface portion 41.

[0036] More precisely, as in Fig. As shown in Figure 3, the hollow cylindrical surface portion 41 includes a first radius r1 with respect to a center axis C of the rotor device 20, and the tip 37 formed at the end portion in the circumferential direction has a second radius r2 with respect to the center axis C of the rotor device 20. Therefore, a first ratio r2 / r1 between the second radius r2 and the first radius r1 may be 1.02 or more and 1.08 or less. In a specific embodiment, the first ratio r2 / r1 is 1.03.

[0037] Various embodiments were also investigated by parameterizing the first ratio as shown in the figures. Fig. Figure 3 indicates the features of the specific parameterization specified in claim 1. An advantageous range was found for r2 / r1: 1.02 < r2 / r1 < 1.08. r2 is the radius toward the tip 37, and r1 is the radius toward the hollow cylindrical surface portion 41. As can be seen, the difference is present, but comparatively moderate. Compared to the parameterization specified in document EP 4 287 463 A1 (see above), a value of g2 - g1 = 0.3 would be achieved by the tooth profile of the present embodiment, which is approximately 0.03 × g1.

[0038] As in Fig. 3, but also further in Fig. 4, which shows an enlarged section of Fig. As shown in Figure 3, the end portion 47 extends around the tip 37, with the tip 37 being defined as an outermost point (in the cross-sectional profile) in the circumferential direction. In other words, the tip 37 does not form a sharp edge as in the prior art, at least in this specific embodiment. Furthermore, the end portion 47 is defined to have a constant radius of curvature rc, and the tip 37 is thus located within the range of a constant radius of curvature rc.

[0039] The inclined surface section 42 may be gently curved from the hollow cylindrical surface section 41 toward the end section 47 with the constant radius of curvature rc. Between the inclined surface section 42 with a varying radius of curvature and the end section with the constant radius of curvature rc, there is a first transition 34, which is also designated in the figure as coordinate x3 (or x3l, with I = left-hand shoulder). Note that a point x2 shown in the figures denotes the coordinate of the tip 37. This first transition 43 between the inclined surface section 41 and the end section 47 has a third radius r3 with respect to the center axis C of the rotor device 20. Here, a second ratio r3 / r1 between the third radius r3 and the first radius r1 is a value of 1.006 or more and 1.01 or less, according to the embodiments shown.

[0040] Further, a second transition 44 is defined between the hollow cylindrical surface portion 41 on one side and each of the inclined surface portions 42 on the other side. This second transition is also designated in the figures by the coordinate x1. As shown in Fig. 5, a first radius line R1, which extends between one of the first transitions 42 and the center axis C of the rotor device 20, and a second radius line R2, which extends between the tip 37 of a respective wing-shaped tooth shoulder 36 and the center axis C of the rotor device 20, enclose a second angle β. Furthermore, a third radius line R3, which extends between a tip 37 of the opposite wing-shaped tooth shoulder 36 of the same tooth tip 35 and the center axis C of the rotor device 20, and a second radius line R2 enclose a first angle α. According to the embodiments presented herein, a second ratio (β / α) between the second angle β and the first angle α is 0.03 or more and 0.18 or less.

[0041] Resulting cogging and maximum cogging torques are in Fig. 6 and Fig. 7 for tooth shoulder profiles with a ratio of r2 / r1 = 1.02, 1.03 and 1.08. As shown in Fig. 6, the cogging torque decreases with increasing r2. As can be seen from the maximum cogging torque, which is shown in Fig. As can be deduced from the torque density shown in Figure 7, the maximum torque density of the electric motor device decreases with increasing r2 (note: absolute value of the displayed torque considered here). The reduction in torque ripple exceeds what would be expected from reducing the cogging torque alone. It appears that a ratio of r2 / r1 = 1.03 provides a best compromise between loss of total torque and reduction of torque fluctuations, which would lead to undesirable noise emission.

[0042] Fig. 8 and Fig. 9 show a comparison of the cogging torque over the rotation angle of the rotor in the prior art ( Fig. 8) and according to one embodiment ( Fig.9). It can be seen that the maximum peak torque is reduced from 5.42 mNm to 4.32 mNm and the total amplitude and harmonics of the cogging torque are reduced.

[0043] It should be noted again that in the drawings, x1 (left and right sides) denotes the second transition between the hollow cylindrical surface portion, x2 (left and right sides) denotes the tip at the curved end portion, and x3 (left and right sides) denotes the first transition between the inclined surface portion and the curved edge portion with a constant radius of curvature. List of reference symbols: 1 opening (roof section of the vehicle) 2 sunroof 10 Electric motor device 20 Rotor device 21 cylindrical outer surface (rotor) 30 Stator device 31 core 32 stator teeth 33 Tooth base 34 Stator ring 35 tooth head 36 wing-shaped shoulder section 360 shoulder section (state of the art) 37 Point at the end of the shoulder 371 Outer edge of surface 39 (sharp edge; state of the art) 372 substantially flat radially oriented surface section (state of the art) 373 (sharply) curved surface section (state of the art) 38 windings 39 Surface facing the at least partially cylindrical outer surface 40 gap 41 hollow cylindrical surface section 42 inclined surface section 43 first transition 44 second transition 47 End section (edge ​​section) 100 vehicles 110 Windshield 120 rear window 130 frame parts (roof) 470 End section (edge ​​section, state of the art) C center axis, axis of rotation R1 first radius line R2 second radius line QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 4 287 463 A1 [0010, 0037] JP 2017-184451 A2

[0011]

Claims

[1] Electric motor device (10) for driving a sunroof (2) or a roller blind in a vehicle (100), comprising: a rotor device (20) comprising an at least partially cylindrical outer surface (21); a stator device (30) having a core (31) including a plurality of stator teeth (32) projecting toward the rotor device (20), the stator teeth (32) comprising a tooth root (33) connected to a stator ring (34) and a tooth tip (35) having a wing-shaped tooth shoulder (36) on each side in a circumferential direction, the wing-shaped tooth shoulder (36) having a tip (37) formed at an end portion (47) of the respective wing-shaped tooth shoulder (36) in the circumferential direction; wherein the tooth tip (35) includes a surface (39) facing the at least partially cylindrical outer surface (21) of the rotor device (20) to form a gap (40) therebetween; wherein the surface (39) comprises: - a hollow cylindrical surface section (41) having a constant gap distance (g1) in the direction of the at least partially cylindrical outer surface (21) of the rotor device (20) in the circumferential direction, and - each having an inclined surface portion (42) having an increasing gap distance (g2) with respect to the at least partially cylindrical outer surface (42) of the rotor device (20) in the circumferential direction towards the respective tip (37) formed by the end portion in the circumferential direction; wherein the hollow cylindrical surface portion (41) includes a first radius (r1) with respect to a center axis (C) of the rotor device, and the tip (37) formed at the end portion in the circumferential direction has a second radius (r2) with respect to the center axis (C) of the rotor device (20); wherein a first ratio (r2 / r1) between the second radius (r2) and the first radius (r1) is 1.02 or more and 1.08 or less. [2] Electric motor device (10) for driving a sunroof (2) or a roller blind in a vehicle (100), comprising: a rotor device (20) comprising an at least partially cylindrical outer surface (21); a stator device (30) having a core (31) including a plurality of stator teeth (32) projecting toward the rotor device (20), the stator teeth (32) comprising a tooth root (33) connected to a stator ring (34) and a tooth tip (35) having a wing-shaped tooth shoulder (36) on each side in a circumferential direction, the wing-shaped tooth shoulder (36) having a tip (37) formed at an end portion (47) of the respective wing-shaped tooth shoulder (36) in the circumferential direction, the end portion (47) being defined to have a curved cross-sectional profile having a constant radius of curvature (rc); wherein the tooth tip (35) includes a surface facing the at least partially cylindrical outer surface (21) of the rotor device (20) to form a gap (40) therebetween; where the surface has: - a hollow cylindrical surface section (41) having a constant gap distance (g1) in the direction of the at least partially cylindrical outer surface (21) of the rotor device (20) in the circumferential direction, and - each having an inclined surface portion (42) having an increasing gap distance (g2) with respect to the at least partially cylindrical outer surface (21) of the rotor device (20) in the circumferential direction in the direction of the respective tip (37) formed by the end portion in the circumferential direction; wherein the hollow cylindrical surface portion (41) includes a first radius (r1) with respect to a center axis (C) of the rotor device (20), and a first transition (43) between the inclined surface portion (41) and the end portion (47) has a third radius (r3) with respect to the center axis (C) of the rotor device (20); wherein a second ratio (r3 / r1) between the third radius (r3) and the first radius (r1) is 1.006 or more and 1.01 or less. [3] Electric motor device (10) according to claim 1 or 2 or according to a combination of the features of claims 1 and 2, wherein the electric motor device (10) is a brushless motor device, for example a BLDC or PMSM motor. [4] Electric motor device (10) according to one of the preceding claims, wherein the hollow cylindrical surface section (41) on one side and each of the inclined surface sections (42) on the other side each define a second transition (44) therebetween, wherein a first radius line (R1) extending between one of the first transitions (42) and the center axis (C) of the rotor device (20) and a second radius line (R2) extending between the tip (37) of a respective wing-shaped tooth shoulder (36) and the center axis (C) of the rotor device (20) enclose a second angle (β), and wherein a third radius line (R3) extending between a tip (37) of the opposite wing-shaped tooth shoulder (36) of the same tooth head (35) and the center axis (C) of the rotor device (20) and a second radius line (R2) enclose a first angle (α), wherein a second ratio (β / α) between the second angle (β) and the first angle (α) is 0.03 or more and 0.18 or less. [5] Electric motor device (10) according to one of the preceding claims, wherein: the increasing gap distance (g2) within the inclined surface section (42) increases smoothly from the second transition to the first transition and further within the curved edge section to the tip of the wing-shaped tooth shoulder. [6] Electric motor device (10) according to one of the preceding claims, wherein: the inclined surface portion (42) extends in a gently curved shape around the tip (37) of the wing-shaped tooth shoulder (36).

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