Disc motor

Abstract

The present application discloses a disc-type motor, comprising: an output shaft, which defines a central axis, and defines an axial direction extending along the central axis, a radial direction perpendicular to the axial direction, and a circumferential direction around the axial direction; a stator assembly, the stator assembly comprising an inner stator coil group and an outer stator coil group, the inner stator coil group and the outer stator coil group respectively comprising a plurality of inner stator coils and a plurality of outer stator coils uniformly arranged in a circumferential direction and having an equal first number, each inner stator coil having a corresponding outer stator coil aligned in a radial direction and located radially outside thereof; a rotor assembly, the rotor assembly comprising an inner magnet group and an outer magnet group, the inner magnet group and the outer magnet group respectively comprising a plurality of inner magnets and a plurality of outer magnets uniformly arranged in a circumferential direction and having an equal second number, each inner magnet having a corresponding outer magnet aligned in a radial direction and located radially outside thereof.

Description

Technical Field

[0001] The present application relates to a disc motor. Background Art

[0002] Axial flux permanent magnet machine (AFPMM) is gaining more and more attention due to its compact structure, high efficiency and high power density. This type of motor is particularly suitable for electric vehicles, renewable energy systems and other applications that require high torque density and compact structure.

[0003] In general, the disc motor includes a stator assembly and a rotor assembly arranged side by side around the output shaft and along the axial direction defined by the output shaft. The stator assembly includes a stator coil for generating an axial magnetic field, and the generated magnetic field passes through the axial air gap between the stator assembly and the rotor assembly. The rotor assembly includes a magnet, which rotates around the output shaft while cutting the magnetic lines of force of the magnetic field.

[0004] In the structure of the prior art, Figure 1 As shown, in a cross section perpendicular to the axial direction defined by the output shaft, a plurality of stator coils 10 are evenly arranged in a circumferential direction around the axial direction, and each stator coil 10 is formed by a conductive wire wound around a stator core.

[0005] The radial inner contour and radial outer contour of each stator coil 10 constitute an inner circumference and an outer circumference. In this stator structure, the temperature of the inner circumference is higher than that of the outer circumference. The allowable temperature limit at the inner circumference makes it impossible to wind more wires, which in turn limits the improvement of the motor power density.

[0006] It is hoped that the above-mentioned technical problems can be solved and the power density of the motor can be improved. Summary of the invention

[0007] The purpose of this application is to provide a new disc motor structure that can improve power density.

[0008] To this end, the present application provides a disc motor, comprising:

[0009] an output shaft defining a central axis, and defining an axial direction extending along the central axis, a radial direction perpendicular to the axial direction, and a circumferential direction around the axial direction;

[0010] a stator assembly mounted around the output shaft and fixed relative to the housing of the disk motor, the stator assembly comprising an inner stator coil group and an outer stator coil group, the inner stator coil group and the outer stator coil group respectively comprising a plurality of inner stator coils and a plurality of outer stator coils uniformly arranged in the circumferential direction and having an equal first number, each inner stator coil having a corresponding outer stator coil aligned in the radial direction and located on the outer side thereof away from the central axis;

[0011] a rotor assembly mounted to the output shaft and rotating therewith, the rotor assembly including an inner magnet group and an outer magnet group, the inner magnet group and the outer magnet group respectively including a plurality of inner magnets and a plurality of outer magnets arranged in a circumferential direction and having an equal second number, each inner magnet having a corresponding outer magnet aligned in a radial direction and located on an outer side thereof away from a central axis.

[0012] In one embodiment, in a cross section perpendicular to the axial direction, the inner stator coil has a first side edge and a second side edge opposite in the circumferential direction, the outer contour of the outer stator coil has a first side edge and a second side edge opposite in the circumferential direction, and the first side edge and the second side edge of the inner stator coil are respectively roughly radially aligned with the first side edge and the second side edge of the outer stator coil.

[0013] In one embodiment, in a cross section perpendicular to the axial direction, outer contours of the inner stator coil and the outer stator coil have substantially equal angles relative to a central axis of the output shaft.

[0014] In one embodiment, the stator assembly includes a stator housing fixed to a disk motor, the stator housing including a plurality of compartments spaced apart by a plurality of spacers in a circumferential direction, each compartment accommodating an inner stator coil and an outer stator coil radially aligned therewith.

[0015] In one embodiment, the inner magnet group includes a plurality of inner magnet subsets arranged in the circumferential direction and spaced apart from each other, each inner magnet subset includes a plurality of inner magnets adjacent to each other in the circumferential direction; correspondingly, the outer magnet group includes a plurality of outer magnet subsets arranged in the circumferential direction and spaced apart from each other, each outer magnet subset includes a plurality of outer magnets adjacent to each other in the circumferential direction.

[0016] In one embodiment, in a cross section perpendicular to the axial direction, the outer contour of the inner magnet has a first side edge and a second side edge opposite to each other in the circumferential direction, and the outer contour of the outer magnet has a first side edge and a second side edge opposite to each other in the circumferential direction, and the first side edge and the second side edge of the inner magnet are substantially radially aligned with the first side edge and the second side edge of the outer magnet, respectively.

[0017] In one embodiment, in a cross section perpendicular to the axial direction, outer contours of the inner magnet and the outer magnet have substantially equal angles relative to the central axis of the output shaft.

[0018] In one embodiment, the inner stator coil and the outer stator coil include an inner core and an outer core, respectively, and wires are wound around wire winding parts of the inner core and the outer core, respectively, to form the inner stator coil and the outer stator coil.

[0019] In one embodiment, in a cross section perpendicular to the axial direction, the wire winding portions of the inner core and the outer core have a substantially fan-shaped or substantially trapezoidal shape.

[0020] In one embodiment, the first number is greater than the second number, preferably, the first number is 1.5 times the second number.

[0021] In one embodiment, the stator assembly includes two stator assemblies, and the rotor assembly includes one rotor assembly, wherein the one rotor assembly is arranged between the two stator assemblies in the axial direction; or

[0022] The stator assembly includes one stator assembly, and the rotor assembly includes two rotor assemblies, wherein the one stator assembly is arranged between the two rotor assemblies in the axial direction; or

[0023] The stator assembly includes a stator assembly, and the rotor assembly includes a rotor assembly, wherein the stator assembly and the rotor assembly are arranged side by side in the axial direction.

[0024] According to the disc motor of the present application, the stator assembly includes an inner stator coil group and an outer stator coil group separated from each other in the radial direction, and correspondingly, the rotor assembly includes an inner magnet group and an outer magnet group separated from each other in the radial direction. Since the outer circumference of the outer stator coil group has not reached the maximum allowable temperature when the inner circumference of the inner stator coil group reaches the limit of the allowable temperature, the inner stator coil group and the outer stator coil group are separately and separately arranged so that the number of winding turns of each outer stator coil in the outer stator coil group can be increased independently of its corresponding inner stator coil, thereby improving the power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The foregoing and other features, advantages and benefits of the present application will be described in detail below with reference to the accompanying drawings in conjunction with exemplary embodiments of the present application.

[0026] Figure 1is a schematic diagram of the arrangement of stator coils constituting a stator assembly of a disk-type motor of the prior art;

[0027] Figure 2 A perspective view of a disc-type motor including two rotor assemblies and a stator assembly sandwiched between the two rotor assemblies according to the present application is shown;

[0028] Figure 3 yes Figure 2 another view of a rotor assembly with one rotor assembly removed to expose the arrangement of stator coils of the stator assembly;

[0029] Figure 4 yes Figure 3 A front view of the invention, in which only the arrangement of the stator coils is shown;

[0030] Figure 5 yes Figure 4 an enlarged view of a portion of the stator coil, the portion comprising an inner stator coil and a corresponding outer stator coil located radially outside the inner stator coil;

[0031] Figure 6 yes Figure 2 A schematic diagram of a rotor assembly of a disc motor according to the present application;

[0032] Figure 7 yes Figure 6 A front view of the invention showing only the arrangement of the magnets; and

[0033] Figure 8 yes Figure 7 An enlarged view of a portion of the device, the portion comprising an inner magnet sub-group and a corresponding outer magnet sub-group located radially outside the inner magnet sub-group. DETAILED DESCRIPTION

[0034] The disc motor (or referred to as “disk permanent magnet motor” or “axial flux permanent magnet motor”) of the present application generally includes an output shaft, at least one stator assembly and at least one rotor assembly.

[0035] The output shaft of the disc motor defines a central axis or a rotation axis, an axial direction extending along the central axis, a radial direction perpendicular to the axial direction, and a circumferential direction extending around the axial direction. The at least one stator assembly and the at least one rotor assembly are mounted around the output shaft and arranged side by side along the above-mentioned axial direction. For example, the disc motor may include two stator assemblies and a rotor assembly disposed between the two stator assemblies in the axial direction; or two rotor assemblies and a stator assembly disposed between the two rotor assemblies in the axial direction; or a rotor assembly and a stator assembly arranged side by side in the axial direction. Optionally, the present application is not limited to the above-mentioned motor configurations, and disc motors containing any number of stator assemblies and rotor assemblies arranged in the axial direction are within the scope of the present application. Figure 2 The perspective view of the disk motor 1 is shown, which includes two rotor assemblies 20 and a stator assembly 30 sandwiched between the two rotor assemblies 20 , wherein the output shaft of the disk motor 1 is installed in the through hole 12 .

[0036] For the sake of clarity, in the present application, the direction in which the central axis of the output shaft (not shown) of the disk motor 1 extends is the axial direction Z, the radial direction R extends radially perpendicular to the axial direction Z, and the circumferential direction C surrounds the axial direction Z. These directions are Figure 4 and 7 They are expressed separately in.

[0037] The stator assembly 30 of the disc motor includes a plurality of stator cores and stator coils wound on each stator core, and the rotor assembly 20 includes a rotor disk in a plane perpendicular to the axial direction and a magnet, such as a permanent magnet, disposed on the rotor disk. The stator coil generates a magnetic field having axial magnetic lines of force, which pass through an axial air gap between the stator assembly and the rotor assembly. The rotor disk of the rotor assembly is fixed to the output shaft and rotates together with the magnet disposed on the rotor disk with the rotating magnetic field generated by the stator coil.

[0038] Figure 3 yes Figure 2 Another view of the present invention shows that one rotor assembly 20 is removed, exposing the arrangement of the stator coils of the stator assembly 30. Figure 4 yes Figure 3 A front view showing Figure 3 Arrangement of the stator coils of the stator assembly 30 in a cross section perpendicular to the axial direction.

[0039] like Figure 3As shown, the stator assembly 30 of the disc motor 1 includes a stator housing 32 fixed to the housing (not shown) of the disc motor 1 and a stator coil accommodated in the stator housing 32, the stator housing 32 defines a plurality of compartments 36 separated by a plurality of spacers 34 in the circumferential direction C, each compartment 36 accommodating a group of corresponding inner stator coils 110 and outer stator coils 210.

[0040] refer to Figure 3 and Figure 4 The stator coil of the stator assembly 30 includes an inner stator coil group 100 located radially inward and thus closer to the central axis of the output shaft and an outer stator coil group 200 located radially outward and thus farther from the central axis of the output shaft. The inner stator coil group 100 and the outer stator coil group 200 respectively include a plurality of (e.g., 12 in the illustrated embodiment) inner stator coils 110 ( Figure 3 and 4 In the figure, only one inner stator coil is marked with a reference numeral) and the same number of multiple outer stator coils 210 (only one outer stator coil is marked with a reference numeral). Each inner stator coil 110 has a corresponding outer stator coil 210 located radially outside thereof, for example, Figure 2 In the figure, the outer stator coil corresponding to the inner stator coil marked with reference numeral 110 is the outer stator coil marked with reference numeral 210 .

[0041] Figure 5 An enlarged view of an inner stator coil 110 and an outer stator coil 210 corresponding to the inner stator coil 110 in the radial direction is shown.

[0042] like Figure 5 As shown, the inner stator coil 110 includes an inner stator core (not shown) located radially inside thereof, and the conductive wire is wound around the inner stator core along a winding direction W indicated by an arrow (or, in another embodiment, in a direction opposite to the illustrated direction W) to form the inner stator coil 110.

[0043] exist Figure 5 In the cross-sectional view, the outer contour of the inner stator coil 110 is generally fan-shaped, and has a first side edge 132 and a second side edge 134 opposite to each other in the circumferential direction C, and has an inner edge 136 located radially innermost and an inner edge 138 located radially outermost.

[0044] The inner stator core of each inner stator coil 110 has a wire winding portion that is approximately trapezoidal, approximately rectangular, approximately square, or approximately fan-shaped in the cross-sectional view. For the inner stator core of each inner stator coil 110, the wire winding portion has a contour that matches the inner contour of the inner stator coil 110 in the cross-sectional view perpendicular to the axial direction and extends along the axial direction Z.

[0045] In some embodiments, the inner stator core of each inner stator coil 110 may only include the wire winding portion located inside the inner stator coil 110. In other embodiments, in order to achieve the fixation of the stator assembly to the motor housing or the stator housing, the inner stator core of each inner stator coil 110 may also include other extension portions that are integrally formed with or attached to the wire winding portion. For example, the inner stator core of each inner stator coil 110 may be roughly "I" or "T" shaped, that is, it also includes other portions extending therefrom transversely to the wire winding portion.

[0046] Similarly, if Figure 3-5 As shown, in the cross-sectional view, the outer contour of the outer stator coil 210 is also roughly fan-shaped, and has a first side edge 232 and a second side edge 234 opposite in the circumferential direction C, and has an inner edge 236 located radially innermost and an outer edge 238 located radially outermost.

[0047] Similarly, the outer stator core of each outer stator coil 210 has a wire winding portion that is roughly trapezoidal, roughly rectangular, roughly square, or roughly fan-shaped in the cross-sectional view. For each outer stator core, the wire winding portion has a contour that matches the inner contour of the outer stator coil 210 in the cross-sectional view perpendicular to the axial direction and extends along the axial direction Z.

[0048] In some embodiments, the outer stator core of each outer stator coil 210 may only include the wire winding portion wound thereon. In other embodiments, in order to achieve the fixation of the stator assembly to the motor housing or the stator housing, the outer stator core of each outer stator coil 210 may also include other extension portions that are integrated with the wire winding portion or attached to the required portion. For example, the inner stator core of each outer stator coil 210 may be roughly "I" or "T" shaped, that is, it also includes other portions extending therefrom transversely to the wire winding portion.

[0049] The inner stator core of each inner stator coil 110 may have the same shape as that of the outer stator core of each outer stator coil 210 , or may be different.

[0050] In the present application, the inner stator coil 110 of the stator assembly 30 is radially aligned with the outer stator coil 210, which means that the first side edge 132 and the second side edge 134 of each inner stator coil 110 are roughly radially aligned with the first side edge 232 and the second side edge 234 of the corresponding outer stator coil 210, respectively, so that the fan-shaped wrap angle (equivalent to the angle between the two side edges relative to the central axis of the output shaft) of the inner stator coil 110 and the outer stator coil 210 is roughly equal.

[0051] As in the stator assembly structure described above, when the inner circumference formed by the inner edges 136 of all inner stator coils 110 has the highest allowable temperature, the number of turns (turns) N1 of each inner stator coil 110 is substantially equal to the number of turns of each stator coil in the prior art. However, the outer circumference formed by the outer edges 236 of all outer stator coils 210 has not yet reached the highest allowable temperature, so the number of turns N2 of each outer stator coil 210 can be greater than the number of turns of each stator coil in the prior art, and thus can carry a larger current. Since the number of turns of the outer stator coil group 200 increases, more energy can be input, so that the power density of the disk motor of the present application is improved.

[0052] Figure 6 shows a schematic diagram of a rotor assembly 20, Figure 7 yes Figure 6 , but only clearly shows the arrangement of the magnets of the rotor assembly 20 in a cross section perpendicular to the axial direction Z. The rotor assembly 20 includes a rotor disk 25 and a plurality of magnets attached to the rotor disk 25.

[0053] Corresponding to the stator assembly 30 including the inner stator coil group 100 and the outer stator coil group 200, the magnets of the rotor assembly 20 also include an inner magnet group 300 located radially inside and thus close to the central axis of the output shaft, and an outer magnet group 400 located radially outside and thus far from the central axis of the output shaft. The inner magnet group 300 and the outer magnet group 400 respectively include the same number of inner magnets 310 and outer magnets 410 arranged along the circumferential direction C around the axial direction Z. Each inner magnet 310 in the inner magnet group 300 has an outer magnet 410 located radially outside and corresponding to it, for example Figure 6-8 The inner layer magnets 310 and 410 with reference numerals are radially corresponding inner layer magnets and outer layer magnets.

[0054] The inner layer magnets 310 constituting the inner layer magnet group 300 are divided into a plurality of inner layer magnet subgroups 310A arranged in the circumferential direction C and slightly spaced apart from each other in the circumferential direction C, each inner layer magnet subgroup 310A including two or more inner layer magnets 310. In the illustrated embodiment, the inner layer magnets 310 include 10 inner layer magnet subgroups 310A, each inner layer magnet subgroup 310 being composed of five inner layer magnets 310 adjacent in the circumferential direction C.

[0055] Accordingly, the outer layer magnets 410 constituting the outer layer magnet group 400 are divided into a plurality of outer layer magnet subgroups 410A arranged in the circumferential direction C and slightly spaced apart from each other in the circumferential direction C, each outer layer magnet subgroup 410A including two or more outer layer magnets 410. In the illustrated embodiment, the outer layer magnets 410 include 10 outer layer magnet subgroups 410A, each outer layer magnet subgroup 410 being composed of five outer layer magnets 410 adjacent in the circumferential direction C. There is a circumferential gap between two outer layer magnet subgroups 410A adjacent in the circumferential direction and between the two inner layer magnet subgroups 310A.

[0056] refer to Figure 8 The inner magnet subgroup 310A and the outer magnet subgroup 410A and each inner magnet 310 and outer magnet 410 correspond to each other in radial direction, that is, the inner magnet 310 has first and second side edges 332 and 334 opposite to each other in the circumferential direction C, and the outer magnet 410 has first and second side edges 432 and 434 opposite to each other in the circumferential direction C, the first side edge 332 of the inner magnet 310 and the first side edge 432 of the outer magnet 410 are substantially aligned in the radial direction R, and the second side edge 334 of the inner magnet 310 and the second side edge 434 of the outer magnet 410 are substantially aligned in the radial direction R. The inner magnet 310 and the outer magnet 410 have inner side edges 336 and 436 located at the innermost radial side, respectively, and outer side edges 338 and 438 located at the outermost radial side, respectively. Thus, the inner magnet 310 has a sector shape defined by the first and second side edges 332 and 334, the inner edge 336 and the outer edge 338, and the outer magnet 410 has an equal sector shape through the first and second side edges 432 and 434, the inner edge 436 and the outer edge 438, and the sector shape defined by the radially corresponding inner magnet 310 and the sector shape of the outer magnet 410 have substantially the same sector wrap angle.

[0057] The inner circumference and outer circumference formed by the inner edges 336 and outer edges 338 of all the inner magnets 310 of the inner magnet group 300 of the rotor assembly 20 are respectively roughly aligned with the inner circumference and outer circumference formed by the inner edges 136 and outer edges 138 of each inner stator coil 110 of the inner stator coil group 100 of the stator assembly in the axial direction Z, and the inner circumference and outer circumference formed by the inner edges 436 and outer edges 438 of all the outer magnets 410 of the outer magnet group 400 of the rotor assembly 20 are roughly aligned with the inner circumference and outer circumference formed by the inner edges 236 and outer edges 238 of each outer stator coil 210 of the outer stator coil group 200 of the stator assembly in the axial direction Z.

[0058] Optionally, the number M1 of circumferentially arranged inner or outer stator coils 110 or 210 included in the inner or outer stator coil group 100 or 200 of the stator assembly is greater than the number M2 of circumferentially arranged inner or outer magnets 310 410 included in the inner or outer magnet group 300 or 400 of the rotor assembly. Preferably, the number M1 is 1.5 times the number M2.

[0059] The preferred embodiments of the present application are described above with reference to the accompanying drawings. Those skilled in the art should understand that the above description is merely exemplary and is not intended to limit the scope of the present application to the specific embodiments shown in the drawings and described above. Without departing from the principles of the present application, the specific structure or parameters of the disc motor can be changed as needed, such as, but not limited to: the number of inner or outer stator coils contained in the inner or outer stator coil group; the number of inner or outer magnets contained in the inner or outer magnet group; the radial dimension ratio of the first or second side edge of the inner stator coil to the first or second side edge of the outer stator coil, that is, the ratio of the radial dimension of the wire winding part of the inner stator core to the radial dimension of the wire winding part of the outer stator core; the circumferential dimension of the inner or outer edge of the inner or outer stator coil; the radial air gap dimension between the outer circumference portion formed by the inner stator coil and the inner circumference portion formed by the outer stator coil, etc. The scope of protection of the present application is limited only by the claims.

Claims

1. A disc motor, comprising: an output shaft defining a central axis, and defining an axial direction extending along the central axis, a radial direction perpendicular to the axial direction, and a circumferential direction around the axial direction; a stator assembly mounted around the output shaft and fixed relative to the housing of the disc motor, the stator assembly comprising an inner stator coil group and an outer stator coil group, the inner stator coil group and the outer stator coil group respectively comprising a plurality of inner stator coils and a plurality of outer stator coils uniformly arranged in a circumferential direction and having an equal first number, each inner stator coil having a corresponding outer stator coil aligned in a radial direction and located on an outer side thereof away from a central axis; and a rotor assembly mounted to the output shaft and rotating therewith, the rotor assembly including an inner magnet group and an outer magnet group, the inner magnet group and the outer magnet group respectively including a plurality of inner magnets and a plurality of outer magnets arranged in a circumferential direction and having an equal second number, each inner magnet having a corresponding outer magnet aligned in a radial direction and located on an outer side thereof away from a central axis.

2. The disk motor according to claim 1, wherein: In a cross section perpendicular to the axial direction, the inner stator coil has a first side edge and a second side edge opposite in the circumferential direction, the outer contour of the outer stator coil has a first side edge and a second side edge opposite in the circumferential direction, and the first side edge and the second side edge of the inner stator coil are radially aligned with the first side edge and the second side edge of the outer stator coil, respectively.

3. The disk motor according to claim 2, wherein: In a cross section perpendicular to the axial direction, outer contours of the inner stator coil and the outer stator coil have equal included angles relative to a central axis of the output shaft.

4. The disc motor according to any one of claims 1 to 3, wherein: The stator assembly includes a stator housing fixed to a disk motor, the stator housing including a plurality of compartments spaced apart by a plurality of spacers in a circumferential direction, each compartment accommodating an inner stator coil and an outer stator coil radially aligned therewith.

5. The disc motor according to any one of claims 1 to 4, wherein: The inner magnet group includes a plurality of inner magnet subsets arranged in a circumferential direction and spaced apart from each other, each inner magnet subset includes a plurality of inner magnets adjacent to each other in the circumferential direction; correspondingly, the outer magnet group includes a plurality of outer magnet subsets arranged in a circumferential direction and spaced apart from each other, each outer magnet subset includes a plurality of outer magnets adjacent to each other in the circumferential direction.

6. The disk motor according to claim 5, wherein: In a cross section perpendicular to the axial direction, the outer contour of the inner layer magnet has a first side edge and a second side edge opposite to each other in the circumferential direction, and the outer contour of the outer layer magnet has a first side edge and a second side edge opposite to each other in the circumferential direction, and the first side edge and the second side edge of the inner layer magnet are radially aligned with the first side edge and the second side edge of the outer layer magnet, respectively.

7. The disk motor according to claim 6, wherein: In a cross section perpendicular to the axial direction, the outer contours of the inner magnet and the outer magnet have equal included angles relative to the central axis of the output shaft.

8. The disc motor according to any one of claims 1 to 7, wherein: The inner layer stator coil and the outer layer stator coil include an inner layer core and an outer layer core, respectively, and conductive wires are wound around conductive wire winding portions of the inner layer core and the outer layer core, respectively, to form the inner layer stator coil and the outer layer stator coil.

9. The disk motor according to claim 8, wherein: In a cross section perpendicular to the axial direction, the wire winding portions of the inner layer core and the outer layer core have a fan-shaped or trapezoidal shape.

10. The disk motor according to any one of claims 1 to 9, wherein: The first number is greater than the second number, and the first number is 1.5 times the second number.

11. The disk motor according to any one of claims 1 to 10, wherein: The stator assembly includes two stator assemblies, and the rotor assembly includes one rotor assembly, wherein the one rotor assembly is arranged between the two stator assemblies in the axial direction; or The stator assembly includes one stator assembly, and the rotor assembly includes two rotor assemblies, wherein the one stator assembly is arranged between the two rotor assemblies in the axial direction; or The stator assembly includes a stator assembly, and the rotor assembly includes a rotor assembly, wherein the stator assembly and the rotor assembly are arranged side by side in the axial direction.

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