Hollow core stepping motor

Abstract

A hollow core stepping motor (1) comprises a stator (2) and a rotor (3) for rotation about an axis (A) relative to the stator (2). The rotor (3) comprises at least one circular permanent magnet array (4), the stator (2) comprises a plurality of circular coil arrays (5, 6, 7, 8), each circular coil array comprising a plurality of coils (5a, 6a, 7a, 8a) for generating a magnetic field. A change in the magnetic field produces a step-by-step rotation of the rotor (3). Each circular coil array (5, 6, 7, 8) is arranged such that a respective coil (5a, 6a, 7a, 8a) is offset from a coil (5a, 6a, 7a, 8a) in an adjacent circular coil array (5, 6, 7, 8), the coils (5a, 6a, 7a, 8a) being offset in a tangential direction (D1) along the circumference of the circular coil array (5, 6, 7, 8) and / or in a radial direction (D2) starting from the axis (A).

Description

Technical Field

[0001] The present invention relates to a hollow-core stepper motor, which includes a stator and a rotor that are coaxially arranged along an axis and nested, and the rotor is configured to rotate around the axis relative to the stator. Background Art

[0002] There are several difficulties in the optical systems of portable electronic devices. The external dimensions of electronic devices such as smart phones are preferably as small as possible, while the optical system requires a certain size to provide sufficiently good image clarity, spatial frequency, sensitivity, etc.

[0003] Hollow-core ring motors have traditionally been used as actuators for various components in linear moving optical systems because the central motor part of such motors is open to allow light to enter. In addition, this form factor enables the motor to be used for functions such as producing a protruding lens, achieving focusing, and even zooming. However, since most of the central volume is removed in such motors, certain driving characteristics are lost, such as torque (generation of force) and precision (resolution). Therefore, current technical solutions for protruding smart phone cameras or smart phone camera optics typically include a small solid-core stepper / DC motor, which is equipped with various gear drive systems to generate high torque and step resolution.

[0004] When integrating the actuator with an image sensor and a circular lens, the actuator is usually placed outside the optical system, thus increasing the size. Using a low-torque small stepper motor requires relatively large transmission components, which generate noise during operation. Audible noise can interfere with the audio of video recording. In addition, by using transmission components with a high gear ratio, although the torque is increased, the actuation speed is reduced at the same time. Therefore, traditional motor systems either generate high torque and medium to low speeds, or generate low torque and high speeds. Generally, in order to provide stable and precise actuation and have a sufficient actuation range, higher torque is required.

[0005] However, in some usage scenarios, for example, when the device is impacted or dropped, high speeds are required to cause a protective or preventive retraction movement of the optical element.

[0006] Therefore, an improved motor is needed, especially for optical systems in small electronic devices. Summary of the Invention

[0007] The object of the present invention is to provide an improved hollow-core stepper motor for an electronic device. The above and other objects are achieved by the features of the independent claims. Other implementations are apparent from the dependent claims, the description, and the drawings.

[0008] According to a first aspect, a hollow-core stepper motor is provided. The hollow-core stepper motor includes a stator and a rotor that are coaxially arranged along an axis and nested, and the rotor is configured to rotate about the axis relative to the stator; the rotor includes at least one circular permanent magnet array; the stator includes a plurality of circular coil arrays, each circular coil array including a plurality of coils for generating a magnetic field, and a change in the magnetic field generates a stepwise rotation of the rotor about the axis relative to the stator; the arrangement of each circular coil array is such that the respective coils are at least partially offset relative to the coils in an adjacent circular coil array, and the coils are offset relative to each other in a tangential direction along the circumference of the circular coil array and / or in a radial direction starting from the axis.

[0009] With this technical solution, the motor has a sufficiently small external dimension and can be used within a portable electronic unit or an optical unit without consuming too much power. Since an additional gear transmission mechanism is eliminated, the torque generated throughout the operating range is sufficiently stable and high enough. In addition, such a motor can simultaneously generate high torque and high speed.

[0010] In a possible implementation of the first aspect, the rotor includes at least two circular permanent magnet arrays, and each circular permanent magnet array is operably coupled to at least one circular coil array. In this way, the functional components of the rotor can be reduced to the smallest possible size, so that the hollow space within the motor can be utilized to accommodate an optical unit or to minimize the size of the overall technical solution.

[0011] In another possible implementation of the first aspect, the stator includes a substrate for carrying the circular coil arrays, and each coil is arranged around a stud that protrudes from the surface of the stator in a direction towards the rotor. This not only simplifies manufacturing and assembly but also ensures a uniform distribution of the coils.

[0012] In yet another possible implementation of the first aspect, the coils in one circular coil array are arranged around a first set of studs, and the coils in an adjacent circular coil array are arranged around a second set of studs, and the second set of studs is staggered with respect to the first set of studs. This ensures a uniform and space-efficient distribution of the coils in several dimensions.

[0013] In yet another possible implementation of the first aspect, each coil is wound around a second axis extending perpendicular to the axis. This makes the magnetic field strongest in one direction, and this direction does not generate interfering currents in the printed circuit board of the device.

[0014] In yet another possible implementation of the first aspect, the hollow core stepper motor includes two circular coil arrays coplanarly disposed on a first plane extending perpendicular to the axis, wherein the coils in one circular coil array are set at a first radial distance from the axis, and the coils in the other circular coil array are set at a second radial distance from the axis, and the second radial distance is greater than the first radial distance. This makes the size of the motor as small as possible, especially for a very thin motor.

[0015] In yet another possible implementation of the first aspect, the hollow core stepper motor includes at least one other circular coil array coplanarly disposed with the circular coil array on the first plane, and the coils in the other circular coil array are set at another radial distance from the axis, and the other radial distance is greater than the second radial distance. In this way, the stepper motor achieves more steps, that is, smaller steps.

[0016] In yet another possible implementation of the first aspect, the hollow core stepper motor includes two circular coil arrays disposed along the axis, wherein the coils in one circular coil array are disposed at a first position along the axis on the first plane, and the coils in the other circular coil array are disposed at a second position along the axis on the second plane. This makes the size of the motor as small as possible, especially with a very small outer diameter.

[0017] In yet another possible implementation of the first aspect, the hollow core stepper motor includes at least one other circular coil array disposed at a third position along the axis on another plane. In this way, the stepper motor achieves more steps, that is, smaller steps.

[0018] In yet another possible implementation of the first aspect, the coils in one circular coil array are offset in the tangential direction along the circumference of the circular coil array with respect to the coils in at least one other circular coil array. This makes the steps of the stepper motor as small as possible.

[0019] In yet another possible implementation of the first aspect, the hollow core stepper motor includes at least three circular coil arrays, wherein at least two circular coil arrays are coplanarly arranged on the first plane, and at least one other circular coil array is disposed on the second plane. This is conducive to the stepper motor generating the required small steps while still having a small volume.

[0020] According to the second aspect, there is provided an electronic device including the hollow core stepper motor provided above.

[0021] In this way, the electronic device can include an optical unit driven by a motor, etc. Such a motor has a sufficiently small form factor to be used within the device or the optical unit and does not consume too much power. Since the additional gear transmission mechanism is omitted, the torque generated within the entire operating range is sufficiently stable and high enough. In addition, such a motor can also generate high torque and high speed simultaneously without generating noise.

[0022] In a possible implementation of the second aspect, the electronic device includes an optical unit, and the optical unit is displaced at least partially by the hollow core stepper motor. In this way, the motor can be used in an optical system.

[0023] According to a third aspect, a method for generating a stepwise rotation of a rotor in a hollow core stepper motor is provided. The rotor includes at least one circular permanent magnet array and is nested with a stator. The stator includes a plurality of circular coil arrays, and each circular coil array includes a plurality of coils for generating a magnetic field. The change in the magnetic field generates the rotation of the rotor relative to the stator about an axis. The arrangement of each circular coil array is such that the respective coils are at least partially offset relative to the coils in an adjacent circular coil array. The coils are offset relative to each other in a tangential direction along the circumference of the circular coil array and / or in a radial direction starting from the axis; the method includes the following steps: supplying the current to the circular coil arrays by alternately supplying the current to a coil in a first circular coil array and a coil in a second circular coil array.

[0024] By this method, the motor has a sufficiently small form factor to be used within a portable electronic unit or an optical unit and does not consume too much power. Since the additional gear transmission mechanism is omitted, the torque generated within the entire operating range is sufficiently stable and high enough. In addition, such a motor can also generate high torque and high speed simultaneously.

[0025] In a possible implementation of the third aspect, the stator includes at least one other circular coil array, and the method further includes the following steps: supplying the current to the circular coil arrays by alternately supplying the current to a coil in a first circular coil array, a coil in a second circular coil array, and a coil in any other circular coil array. In this way, the stepper motor achieves more steps, i.e., smaller steps.

[0026] In another possible implementation of the third aspect, the first circular coil array is disposed on a first plane, the second circular coil array is disposed on a second plane, and the current is alternately supplied to one coil in the first circular coil array and one coil in the second circular coil array. This enables the size of the motor to be minimized, especially the outer diameter is very small.

[0027] In yet another possible implementation of the third aspect, the first circular coil array and the second circular coil array are disposed on the first plane, and the current is alternately supplied to one coil in the first circular coil array and one coil in the second circular coil array. This enables the size of the motor to be minimized, especially for a very thin motor.

[0028] In yet another possible implementation of the third aspect, the stator includes at least one other circular coil array disposed on the first plane, the second plane, or other planes, and the current is alternately supplied to one coil in the first circular coil array, one coil in the second circular coil array, and one coil in the other coil array. This is beneficial for the stepper motor to generate the required small steps while still having a small volume.

[0029] These and other aspects are apparent in the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following detailed part of the present invention, various aspects, embodiments, and various implementations will be explained in more detail with reference to the exemplary embodiments shown in the drawings, in which:

[0031] Figure 1a A cross-sectional perspective view of a hollow-core stepper motor provided by an example of an embodiment of the present invention is shown, in which the optical unit is in a retracted position;

[0032] Figure 1b Shows Figure 1a a cross-sectional perspective view of the example in

[0033] Figure 2 in which the optical unit is in an extended position;

[0034] Figure 3 A cross-sectional perspective view of a part of a hollow-core stepper motor provided by an example of an embodiment of the present invention is shown;

[0035] Figure 4a A perspective view of a part of a stator provided by an example of an embodiment of the present invention is shown;

[0036] Figure 4b shows a cross-sectional view of an example in Figure 4a ;

[0037] Figure 5a shows a perspective view of a stator and a rotor provided by an example of an embodiment of the present invention;

[0038] Figure 5b shows Figure 5a a side view of an example in

[0039] Figure 5c and Figure 5d shows possible paths through which current flows between coils in different circular coil arrays in Figure 5a and Figure 5b ;

[0040] Figure 6 shows possible paths through which current flows between coils in different circular coil arrays of a stator provided by an example of an embodiment of the present invention;

[0041] Figure 7a shows a partial perspective view of a stator provided by an example of an embodiment of the present invention;

[0042] Figure 7b shows Figure 7a an exploded view of an example in

[0043] Figure 7c shows Figure 7a a top view of an example in

[0044] Figure 8a including possible paths through which current flows between coils in different circular coil arrays of a stator provided by an example of an embodiment of the present invention;

[0045] Figure 8b shows Figure 8a a side view of an example in including possible paths through which current flows between coils in different circular coil arrays.

[0046] The present invention relates to an electronic device, which includes a hollow-core stepper motor 1, which will be introduced in detail below. The hollow-core stepper motor 1 is particularly suitable for smaller electronic devices such as smartphones and tablet computers, but the hollow-core stepper motor 1 can also be used in devices of any size. An optical unit can be connected to the hollow-core stepper motor 1 and is optionally at least partially surrounded by the hollow-core stepper motor 1. The hollow-core stepper motor 1 can also be used to generate a rotational movement about an axis A, so that such an optical unit can linearly move along the axis A. The optical unit can include at least one lens module, and the lens module in turn includes at least one lens.

[0047] The hollow core stepper motor 1 includes a stator 2 and a rotor 3 which are coaxially arranged along an axis A and nested, and the rotor 3 is configured to rotate about the axis A relative to the stator 2; the rotor 3 includes at least one circular permanent magnet array 4; the stator 2 includes a plurality of circular coil arrays 5, 6, 7, 8, and each circular coil array 5, 6, 7, 8 includes a plurality of coils 5a, 6a, 7a, 8a for generating a magnetic field, and the change of the magnetic field generates a stepwise rotation of the rotor 3 about the axis A relative to the stator 2; the arrangement of each circular coil array 5, 6, 7, 8 is such that the respective coils 5a, 6a, 7a, 8a are at least partially offset relative to the coils 5a, 6a, 7a, 8a in adjacent circular coil arrays 5, 6, 7, 8, and the coils 5a, 6a, 7a, 8a are offset relative to each other in the tangential direction D1 along the circumference of the circular coil arrays 5, 6, 7, 8 and / or in the radial direction D2 starting from the axis A.

[0048] As described above, the hollow core stepper motor 1 includes a stator 2 and a rotor 3 which are coaxially arranged along an axis A and nested, that is to say, the stator 2 and the rotor 3 are coaxially arranged along the axis A, and the rotor 3 surrounds the stator 2, as Figures 1a to 3 shown, or alternatively, the stator 2 surrounds the rotor 3. In other words, the stator 2 and the rotor 3 are annular elements. The inner diameter of the outermost side of the stator 2 and the rotor 3 is greater than the outer diameter of the innermost side of the stator 2 and the rotor 3. The optical unit 2 can be arranged in the hollow space defined by the inner diameter of the innermost side of the stator 2 and the rotor 3.

[0049] The rotor 3 is configured to rotate about the axis A relative to the stator 2. The axis A can coincide with the optical axis of the optical unit which is operably coupled to the hollow core stepper motor. The rotor 3 includes at least one circular permanent magnet array 4, Figure 3 and Figure 4a shows an embodiment including one circular permanent magnet array 4. The rotor 3 can also include two or more circular permanent magnet arrays 4, that is, two or more circular permanent magnet arrays 4 stacked on top of each other along the axis A (not shown).

[0050] The stator 2 includes a plurality of circular coil arrays 5, 6, 7, 8. Figure 4a and Figure 4b shows one circular coil array 5, 6, 7, 8. Each circular coil array 5, 6, 7, 8 includes a plurality of coils 5a, 6a, 7a, 8a for generating a magnetic field. The change of the magnetic field (i.e., the change of the attractive force or the repulsive force) generates a stepwise rotation of the rotor 3 (including the permanent magnet 4) about the axis A relative to the stator 2. Each circular permanent magnet array 4 is operably coupled to at least one circular coil array 5, 6, 7, 8.

[0051] Each step of the progressive rotation about axis A can correspond to a predetermined range of movement of other components such as the optical unit along the first axis A1, which can be equal to the depth of focus of the optical unit, etc. For example, the range of movement can be from 3 mm to 7 mm, and the movement can be completed in a time less than 500 ms. As Figures 1a to 2 shown, a connection structure can be provided between the optical unit and the rotor 3. The connection structure can include at least two threaded elements that are configured to move at least partially along axis A in response to rotation of the rotor 3 about axis A.

[0052] As Figure 4b shown, the stator 2 can include a substrate 2a that is configured to carry a circular coil array 5, 6, 7, 8, each coil 5a, 6a, 7a, 8a being disposed around a stud 2b, 2c that projects from the surface of the stator 2 in a direction towards the rotor 3. Each coil 5a, 6a, 7a, 8a can be wound around one of the studs 2b, 2c.

[0053] As Figures 7a to 7c shown, the coils 5a, 6a, 7a, 8a in one of the circular coil arrays 5, 6, 7, 8 can be disposed around a first set of studs 2b, and the coils 5a, 6a, 7a, 8a in an adjacent circular coil array 5a, 6a, 7a, 8a can be disposed around a second set of studs 2c, the second set of studs 2c being staggered with respect to the first set of studs 2b.

[0054] Each circular coil array 5, 6, 7, 8 is arranged such that its respective coils 5a, 6a, 7a, 8a are at least partially offset with respect to the coils 5a, 6a, 7a, 8a in an adjacent circular coil array 5, 6, 7, 8.

[0055] For example, the coils 5a in the circular coil array 5 are offset or misaligned with respect to the coils 6a in the circular coil array 6. The coils 5a, 6a, 7a, 8a are offset with respect to each other in the tangential direction D1 along the circumference of the circular coil arrays 5, 6, 7, 8 and / or in the radial direction D2 as seen from the axis A, the tangential direction D1 and the radial direction D2 being as Figure 3 shown.

[0056] For example, if the stator 2 includes a circular coil array 5 stacked along the axis A above the circular coil array 6, as Figures 5a to 5d shown, then any individual coil 5a in the circular coil array 5 can be offset in the tangential direction D1 with respect to an individual coil 6a in two adjacent (optionally adjacent) circular coil arrays 6 such that the longitudinal axis of the coil 5a is misaligned with the corresponding longitudinal axis of the coil 6a, the longitudinal axes of the coils 5a, 6a extending parallel to the axis A.

[0057] The stator 2 may include any suitable number of circular coil arrays 5 stacked on top of each other. For example, Figure 6 Three circular coil arrays 5, 7, 8 stacked on top of each other are shown. In this case, the longitudinal axis of any coil 5a is misaligned with the corresponding longitudinal axis of the adjacent coil 7a in the circular coil array 7 and the corresponding longitudinal axis of the coil 8a in the circular coil array 8 provided on the side of the circular coil array 7 opposite to the circular coil array 5.

[0058] In other words, as Figure 5b shown, the hollow core stepper motor 1 may include two circular coil arrays 5, 7 arranged along the axis A, where the coils 5a in one circular coil array 5 are provided at a first position along the axis A on the first plane P1, and the coils 7a in the other circular coil array 7 are provided at a second position along the axis A on the second plane P2. As Figure 6 shown, the hollow core stepper motor 1 may include at least one other circular coil array 8, which are provided at a third position along the axis A on the other plane P3.

[0059] If the stator 2 includes a circular coil array 5 nested within a circular coil array 6, as Figures 7a to 7c shown, any individual coil 5a in the circular coil array 5 may be offset radially D2 with respect to the adjacent individual coil 6a in the circular coil array 6 such that the coils 5a in the circular coil array 5 are provided within the coils 6a in the circular line 6. In addition, each individual coil 5a in the circular coil array 5 may be offset in the tangential direction D1 with respect to the adjacent (optionally adjacent) individual coil 6a in the circular coil array 6 such that each individual coil 5a partially overlaps with two adjacent coils 6a.

[0060] In other words, as Figure 7a shown, the hollow core stepper motor 1 may include two circular coil arrays 5, 6 arranged coplanarly on a first plane P1 extending perpendicular to the axis A. As Figure 7c shown, the radial distance of the coils 5a in one circular coil array 5 from the axis A is set to a first radial distance R1, while the radial distance of the coils 6a in the other circular coil array 6 from the axis A is set to a second radial distance R2, and the second radial distance R2 is greater than the first radial distance R1.

[0061] The hollow core stepper motor 1 may include at least one other circular coil arrays 7, 8 arranged coplanarly with the circular coil arrays 5, 6 on the first plane P1, and the radial distance of the coils 7a, 8a in the other circular coil arrays 7, 8 from the axis A is set to other radial distances R3, and the other radial distances R3 are greater than the second radial distance R2 (not shown).

[0062] If the stator 2 includes more than two circular coil arrays 5, 6, 7, 8, these coil arrays can be stacked or nested, as Figure 8a and Figure 8b . The stator 2 includes a first coil array layer and a second coil array layer. The first coil array layer includes the circular coil array 5 and the circular coil array 6 which are nested. The second coil array layer includes the circular coil array 7 and the circular coil array 8 which are nested. These two coil array layers are stacked along the axis A.

[0063] The hollow-core stepper motor may also include at least three circular coil arrays 5, 6, 7, 8. Among them, at least two circular coil arrays 5, 6 are coplanarly arranged on the first plane P1, and at least one other circular coil array 7, 8 is arranged on the second plane P2.

[0064] Regardless of whether the circular coil array configuration is nested, stacked, or nested and stacked, the coils 5a, 6a, 7a, 8a in one circular coil array 5, 6, 7, 8 can be offset in the tangential direction along the circumference of the circular coil array relative to the coils 5a, 6a, 7a, 8a in at least one other circular coil array 5, 6, 7, 8.

[0065] The present invention also relates to a method for generating a stepwise rotation of the rotor 3 of the hollow-core stepper motor 1. The rotor 3 includes at least one circular permanent magnet array 4 and is nested with the stator 2. The stator 2 includes a plurality of circular coil arrays 5, 6, 7, 8. Each circular coil array 5, 6, 7, 8 includes a plurality of coils 5a, 6a, 7a, 8a for generating a magnetic field. The change of the magnetic field generates the rotation of the rotor 3 relative to the stator 2 around the axis A. The setting of each circular coil array 5, 6, 7, 8 is such that the respective coils 5a, 6a, 7a, 8a are at least partially offset relative to the coils 5a, 6a, 7a, 8a in the adjacent circular coil arrays 5, 6, 7, 8. The coils 5a, 6a, 7a, 8a are offset relative to each other in the tangential direction D1 along the circumference of the circular coil arrays 5, 6, 7, 8 and / or in the radial direction D2 starting from the axis A.

[0066] The above method includes the following steps: By alternately supplying current to a coil 5a in the first circular coil array 5 and a coil 6a in the second circular coil array 6, current is supplied to the circular coil arrays 5, 6. This is indicated by the dotted lines in Figure 5c 、 Figure 5d and Figure 7c .

[0067] The stator 2 may include at least one other circular coil array 7, 8, and the above method may include the following additional steps: providing current to the circular coil arrays 5, 6, 7, 8 by alternately supplying current to one coil 5a in the first circular coil array 5, one coil 6a in the second circular coil array 6, and one coil 7a, 8a in any other circular coil array 7, 8. This is shown by the dashed lines in Figure 6 and Figure 8b as shown.

[0068] As Figure 5c and Figure 5d shown, the first circular coil array 5 may be disposed on the first plane P1, the second circular coil array 6 may be disposed on the second plane P2, and current may be alternately supplied to one coil 5a in the first circular coil array 5 and one coil 6a in the second circular coil array 6.

[0069] As Figure 7c shown, the first circular coil array 5 and the second circular coil array 6 may be disposed on the first plane P1, and current may be alternately supplied to one coil 5a in the first circular coil array 5 and one coil 6a in the second circular coil array 6.

[0070] As Figure 8b shown, the stator 2 may include at least one other circular coil array 7, 8 disposed on the first plane P1, the second plane P2, or other plane P3, and current may be alternately supplied to one coil 5a in the first circular coil array 5, one coil 6a in the second circular coil array 6, and one coil 7a, 8a in the other coil array 7, 8.

[0071] Various aspects and implementations have been described in connection with various embodiments. However, those skilled in the art, when practicing the claimed subject matter, can understand and realize other variations of the disclosed embodiments by studying the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Listing some measures in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0072] The reference numerals used in the claims should not be construed as limiting the scope. Unless otherwise indicated, the drawings (e.g., cross-hatching, component arrangements, proportions, degrees, etc.) should be read in conjunction with the specification and should be considered part of the entire written description of the invention. As used herein, the terms "horizontal," "vertical," "left," "right," "upper," and "lower," and their adjectival and adverbial derivatives (e.g., "horizontally," "to the right," "upward," etc.) refer only to the direction of the structure shown when a particular drawing is facing the reader. Similarly, the terms "inward" and "outward" generally refer to the direction of a surface relative to its axis of elongation or axis of rotation, as the case may be.

Claims

1. A hollow core stepper motor (1), characterized in that, the hollow core stepper motor (1) comprises: a stator (2) and a rotor (3) which are coaxially arranged and nested along an axis (A), wherein the rotor (3) is configured to rotate relative to the stator (2) about the axis (A); the rotor (3) comprises at least one circular permanent magnet array (4); the stator (2) comprises a plurality of circular coil arrays (5, 6, 7, 8), each circular coil array (5, 6, 7, 8) comprises a plurality of coils (5a, 6a, 7a, 8a) for generating a magnetic field, and the change of the magnetic field generates a stepwise rotation of the rotor (3) relative to the stator (2) about the axis (A); the arrangement of each circular coil array (5, 6, 7, 8) is such that the respective coils (5a, 6a, 7a, 8a) are at least partially offset relative to the coils (5a, 6a, 7a, 8a) in adjacent circular coil arrays (5, 6, 7, 8); the coils (5a, 6a, 7a, 8a) are offset relative to each other in a tangential direction (D1) along the circumference of the circular coil arrays (5, 6, 7, 8) and / or in a radial direction (D2) starting from the axis (A).

2. The hollow core stepper motor (1) according to claim 1, characterized in that, the rotor (3) comprises at least two circular permanent magnet arrays (4), and each circular permanent magnet array (4) is operatively coupled to at least one circular coil array (5, 6, 7, 8).

3. The hollow core stepper motor (1) according to claim 1 or 2, characterized in that, the stator (2) comprises a substrate (2a) for carrying the circular coil arrays (5, 6, 7, 8), and each coil (5a, 6a, 7a, 8a) is arranged around a stud (2b, 2c), and the stud (2b, 2c) protrudes from the surface of the stator (2) in a direction towards the rotor (3).

4. The hollow core stepper motor (1) according to claim 3, characterized in that, the coils (5a, 6a, 7a, 8a) in one circular coil array (5, 6, 7, 8) are arranged around a first set of studs (2b), and the coils (5a, 6a, 7a, 8a) in an adjacent circular coil array (5a, 6a, 7a, 8a) are arranged around a second set of studs (2c), and the second set of studs (2c) is staggered with the first set of studs (2b).

5. The hollow core stepper motor (1) according to any one of the above claims, characterized in that, The hollow-core stepping motor (1) includes two circular coil arrays (5, 6) arranged coplanarly on a first plane (P1) extending perpendicular to the axis (A), where the coils (5a) in one circular coil array (5) are set at a first radial distance (R1) from the axis (A), and the coils (6a) in the other circular coil array (6) are set at a second radial distance (R2) from the axis (A), and the second radial distance (R2) is greater than the first radial distance (R1).

6. The hollow-core stepping motor (1) according to claim 5, characterized in that, the hollow-core stepping motor (1) includes at least one other circular coil array (7, 8) arranged coplanarly with the circular coil arrays (5, 6) on the first plane (P1), and the coils (7a, 8a) in the other circular coil array (7, 8) are set at another radial distance (R3) from the axis (A), and the other radial distance (R3) is greater than the second radial distance (R2).

7. The hollow-core stepping motor (1) according to any one of the above claims, characterized in that, the hollow-core stepping motor (1) includes two circular coil arrays (5, 7) arranged along the axis (A), where the coils (5a) in one circular coil array (5) are arranged at a first position along the axis (A) on the first plane (P1), and the coils (7a) in the other circular coil array (7) are arranged at a second position along the axis (A) on the second plane (P2).

8. The hollow-core stepping motor (1) according to claim 7, characterized in that, the hollow-core stepping motor (1) includes at least one other circular coil array (8), and the other circular coil array (8) is arranged at a third position along the axis (A) on another plane (P3).

9. The hollow-core stepping motor (1) according to any one of claims 5 to 8, characterized in that, the coils (5a, 6a, 7a, 8a) of one circular coil array (5, 6, 7, 8) are offset in the tangential direction along the circumference of the circular coil array with respect to the coils (5a, 6a, 7a, 8a) of at least one other circular coil array (5, 6, 7, 8).

10. The hollow-core stepping motor according to any one of the above claims, characterized in that, the hollow-core stepping motor includes at least three circular coil arrays (5, 6, 7, 8), where at least two circular coil arrays (5, 6) are arranged coplanarly on the first plane (P1), and at least one other circular coil array (7, 8) is arranged on the second plane (P2).

11. An electronic device, characterized in that, the electronic device includes the hollow-core stepping motor (1) according to any one of claims 1 to 10.

12. A method for generating a stepwise rotation of a rotor (3) in a hollow-core stepping motor (1), characterized in that, The rotor (3) includes at least one circular permanent magnet array (4) and is nested with the stator (2). The stator (2) includes a plurality of circular coil arrays (5, 6, 7, 8). Each circular coil array (5, 6, 7, 8) includes a plurality of coils (5a, 6a, 7a, 8a) for generating a magnetic field. The change of the magnetic field generates the rotation of the rotor (3) relative to the stator (2) about the axis (A). The arrangement of each circular coil array (5, 6, 7, 8) is such that the respective coils (5a, 6a, 7a, 8a) are at least partially offset relative to the coils (5a, 6a, 7a, 8a) in adjacent circular coil arrays (5, 6, 7, 8). The coils (5a, 6a, 7a, 8a) are offset relative to each other in the tangential direction (D1) along the circumference of the circular coil arrays (5, 6, 7, 8) and / or in the radial direction (D2) starting from the axis (A). The method includes the following steps: supplying the current to the circular coil arrays (5, 6) by alternately supplying the current to a coil (5a) in the first circular coil array (5) and a coil (6a) in the second circular coil array (6).

13. The method according to claim 12, wherein, the stator (2) includes at least one other circular coil array (7, 8), and the method further includes the following steps: supplying the current to the circular coil arrays (5, 6, 7, 8) by alternately supplying the current to a coil (5a) in the first circular coil array (5), a coil (6a) in the second circular coil array (6), and a coil (7a, 8a) in any other circular coil array (7, 8).

14. The method according to claim 12 or 13, wherein, the first circular coil array (5) is arranged on a first plane (P1), the second circular coil array (6) is arranged on a second plane (P2), and the current is alternately supplied to a coil (5a) in the first circular coil array (5) and a coil (6a) in the second circular coil array (6).

15. The method according to any one of claims 12 to 14, wherein, the first circular coil array (5) and the second circular coil array (6) are arranged on the first plane (P1), and the current is alternately supplied to a coil (5a) in the first circular coil array (5) and a coil (6a) in the second circular coil array (6).

16. The method according to any one of claims 12 to 15, wherein, The stator (2) includes at least one other circular coil array (7, 8) disposed on the first plane (P1), the second plane (P2), or other plane (P3), and the current is alternately supplied to a coil (5a) in the first circular coil array (5), a coil (6a) in the second circular coil array (6), and a coil (7a, 8a) in the other coil arrays (7, 8).

Images