Two-phase stepping motor

Abstract

The invention relates to a two-phase stepping motor (100) comprising: a central shaft (1); two electromagnetic coils (3); two ferromagnetic stators (2A, 2B), each housing an electromagnetic coil (3); a rotor (4) rotationally fixed on the central shaft (1) and positioned between the two stators (2A, 2B), the rotor (4) having two faces, each face being magnetized; and a spacer (5) arranged between the stators (2A, 2B) for maintaining the two stators at a fixed minimum distance from each other. A central shaft (1) passes through each of the two coils (3) to permit rotation of the central shaft (1) within the stators (2A, 2B). Each of the two stators (2A, 2B) comprises an annular portion arranged around one of the coils and at least two teeth (250) extending from the annular portion, each tooth comprising a radial portion (251) extending radially between one of the coils (3) and the rotor (4) in the direction of the central axis (1). The teeth of the temporarily polarized stator all have the same polarity.

Description

Technical Field

[0001] The invention relates to a stepper motor, in particular to a two-phase stepper motor. Background Art

[0002] Stepper motors, especially compact stepper motors, can be applied to equipment that requires high precision. The angular rotation of these motors is controlled by means of pulse signals, making them suitable for a wide variety of electrical equipment. For example, stepper motors are commonly found in medical devices (e.g., medication dispensing devices) and optical equipment (such as microscopes or cameras).

[0003] Different types of stepper motors are known in the art, each type of stepper motor seeking a different balance between speed and torque.

[0004] Variable reluctance (VR) stepper motors, for example, include a stator with several phases and a rotor, each of which provides teeth with concentrated magnetic forces. The angular rotation of the rotor is driven by the attraction of the rotor teeth to the oppositely magnetized poles on the stator teeth. VR motors generally do not contain permanent magnets and achieve relatively good speeds. However, one of their disadvantages is that torque control is not optimal.

[0005] Compared with VR type stepper motors, permanent magnet (PM) type stepper motors achieve relatively lower speed but better torque.

[0006] PM stepper motors having a disc-shaped rotor, in which the faces of the rotor are alternately magnetized, have been described previously.

[0007] For example, US5982058A describes a two-phase stepper motor having two rotors rotatably fixed on an axis, the two rotors having a first permanent magnet and a second permanent magnet, each having a plurality of north pole and south pole magnet regions. The stator is loosely mounted around the axis and positioned between the opposing magnets. The stator has a disc-shaped yoke and structural poles extending parallel to the axis away from the yoke toward the rotor. Electromagnetic wire coils are wound around these structural poles to allow the formation of multiple electromagnets.

[0008] Alternative implementations of PM stepper motors with cylindrical rotors are also known in the art. The cylindrical rotor is axially magnetized so that the north and south poles alternate around the lateral cylindrical surface of the rotor. Portions of the stator and / or electromagnetic coils are typically arranged around the lateral surface of the cylindrical rotor so as to interact with the alternatingly polarized lateral surface.

[0009] For example, EP1482626A1 describes a PM stepper motor whose outer circumference of a cylindrical rotor assembly is multi-pole magnetized. The stator assembly includes a first stator unit and a second stator unit, each of which has a yoke with a plurality of teeth formed along one side and bent toward the other yoke in the assembled motor. The teeth of the two yokes are connected to each other by means of an inserted spacer. These teeth are aligned with the magnetized outer circumference of the cylindrical rotor assembly.

[0010] US4207483 describes a cylindrical stepper motor comprising a stator member aligned on a common axis with a rotor member, one of the members having two pairs of interdigitated pole teeth. Each pair of pole teeth comprises an inner pole tooth and an outer pole tooth, wherein a coil associated with a pair of interdigitated pole teeth magnetizes the inner pole tooth and the outer pole tooth in the pair with opposite polarity. The pair of interdigitated teeth extend perpendicularly to the rotor axis from an array (e.g., two coplanar flat rings).

[0011] The present invention seeks to find a compact PM stepper motor, preferably of cylindrical shape, which can provide high torque and a large number of angular positions. Summary of the invention

[0012] The object of the present invention is to provide a compact permanent magnet stepper motor which is powerful and capable of precise angular positioning without compromising its compact size.

[0013] Another object of the present invention is to improve the torque of a compact permanent magnet stepper motor.

[0014] Preferably, the stepper motor should be able to provide higher torque than a conventional PM stepper motor of the same or similar size, with the same or similar step angle.

[0015] Another object of the present invention is to provide an alternative arrangement of a powerful stepper motor having compact dimensions.

[0016] According to the invention, one or more of these objects are achieved by the subject matter of the appended claims and in particular by the independent claim. Further optional embodiments are provided in the dependent claims.

[0017] In particular, one or more of these objects are achieved by a stepper motor comprising: a central shaft; two electromagnetic coils; two ferromagnetic stators, each housing an electromagnetic coil. The central shaft of the motor passes through each of the two coils, thereby allowing the shaft to rotate within the stator.

[0018] The electromagnetic coils are preferably copper coils made of insulated copper wire.

[0019] The stepper motor further comprises a rotor mounted on the central shaft such that the rotor is rotationally fixed to the shaft. The rotor is positioned between the two stators. The rotational movement of the central axis is driven by the angular displacement of the rotor.

[0020] Each of the two stators includes an annular portion arranged around one of the coils and at least two teeth extending from the annular portion. Each tooth includes a radial portion extending radially in the direction of the central axis. The radial portion of the stator tooth is layered between the electromagnetic coil housed in the stator and the face of the rotor.

[0021] In order to drive the rotor, the stator is temporarily polarized. The teeth of the temporarily polarized stator all have the same polarity.

[0022] The teeth of one temporarily polarized stator may have one polarity and the teeth of the other polarized stator may have the opposite polarity.

[0023] The electromagnetic coils housed by the stator may fill substantially the entire interior cylindrical volume enclosed by the stator, thereby maximizing the volume of the coils inside the stator.

[0024] Since the stator teeth do not protrude into the interior cylindrical volume defined by the stator, the coils can be wound in cylindrical form to a diameter that matches the inner diameter of the cylindrical stator.

[0025] The coil may extend from its core to the inner surface of the cylindrical stator wall.

[0026] The arrangement of the stator, stator teeth and magnetic rotor of the invention allows to optimize the space available for winding electromagnetic wires on both sides of the magnetic rotor.

[0027] Thus, this arrangement allows the volume of the electromagnetic wire (e.g. copper wire) included in the coil to be increased relative to the volume of the magnet. This increased ratio helps achieve better torque for the motor. Furthermore, the amount of electromagnetic wire is also increased relative to the volume of ferromagnetic material, further facilitating high torque.

[0028] Additionally, the arrangement of the invention allows the number of windings of the electromagnetic wire in the coil to be increased.

[0029] Unlike conventional stepper motors where multiple coils are wound around multiple teeth, lobes, poles or other structural elements of the stator to provide alternating magnetic poles, the number of windings of the coils in the present invention is completely independent of the number of teeth, or the number of structures providing alternating magnetic poles.

[0030] Preferably, no teeth or radial projections extend into the space delimited by the stator walls.Thus, the stator allows increasing the packaging weight of the electromagnetic coil windings in the motor.

[0031] The magnitude of the magnetic field strength is proportional to the number of windings in the electromagnetic coil. More efficient packaging of the coils in a stepper motor produces increased torque. The increased torque provides a more powerful stepper motor without having to increase the current or increase the size of the motor.

[0032] The teeth of the stator may further comprise a longitudinal portion extending parallel to the central axis towards the rotor as a continuation of the annular portion of the stator. In this embodiment, the radial portion of the tooth is substantially perpendicular to the longitudinal portion.

[0033] Preferably, the inner diameter of the cylindrical volume enclosed by the annular portion of the stator is the same as the inner diameter defined by the longitudinal portions of the stator teeth.

[0034] The inner diameter of the stator is preferably constant over the length of the stator. Furthermore, the inner diameter of the stator is preferably also constant in the radial direction of the lateral surface. This means that no other structural features of the stator protrude into the inner cylindrical volume of the stator.

[0035] The two stators are preferably substantially identical.The teeth of one stator are preferably angularly offset relative to the teeth of the other stator.

[0036] The motor further comprises a spacer arranged between the stators for maintaining the two stators at a fixed minimum distance from each other. The spacer should be sized to prevent the stator from contacting the face of the rotor. The spacer is preferably at least partially made of an insulating material such as plastic or a composite insulating material.

[0037] The spacer preferably comprises an annular portion. The annular portion is arranged around the rotor.

[0038] The spacer is preferably arranged to maintain the angular offset of the teeth of the two stators so that the angular position of the stators relative to each other is fixed. The spacer may, for example, have a projection for engaging between each pair of longitudinal portions of adjacent stator teeth. These projections preferably protrude from both sides of the annular portion parallel to the central axis so that at least one projection on both sides engages with a compatible recess between two adjacent teeth in one stator.

[0039] The stator includes a stator yoke having a cylindrical portion. The stator may also include a flange having a hollow cylindrical member having a diameter smaller than the stator yoke. The cylindrical flange member is axially inserted into the stator yoke to mount the coil. In this embodiment, the center axis axially passes through the cylindrical flange member. The cylindrical flange member can be inserted through the center of the coil. The coil can also be wound on the outer surface of the cylindrical flange member.

[0040] The stator may further include a cover member sized to cover the face of the stator opposite the stator teeth. This face is the second face of the stator, which faces away from the rotor in the assembled stepper motor. The cover member may be connected to the cylindrical flange member. However, in embodiments of the stator without an axially arranged cylindrical flange member, a cover member may also be included.

[0041] The covering member provides a surface to which the motor can be connected to an external structure or element. The covering member can, for example, be arranged to fix the motor to a support device. The covering member can also be arranged to attach a gearbox and / or an adapter to the motor.

[0042] The rotor has two faces, each of which is magnetized. The radial portions of the stator teeth are arranged between the coils and the rotor so as to interact with the magnetized faces of the rotor.

[0043] Since the stator and the rotor including the teeth are arranged sequentially in the axial direction of the rotor, the volume of the magnetic rotor having a defined thickness can be maximized to fit the cylindrical shape of the motor. This arrangement provides a significant advantage over PM stepper motors known in the art, in which stator components (e.g., coils) are arranged around the lateral surface of the rotor, thereby increasing the outer diameter of the motor.

[0044] Thus, the arrangement of the teeth relative to the rotor in the present invention allows maximizing the diameter of the magnetic rotor for a given diameter of the stepper motor.

[0045] In addition, since the ferromagnetic stator teeth interact with both faces of the rotor, longitudinal magnetization along the lateral surface of the rotor is not required to drive the angular displacement of the rotor. Therefore, the rotor can be disc-shaped. The disc-shaped rotor also helps to reduce the length of the entire motor.

[0046] In a preferred embodiment, the rotor comprises two magnetic rotor disks, each disk comprising an even number of disk sectors. The disks are magnetized so that each magnetic south pole and magnetic north pole alternate on a disk sector on each side of the rotor disk. The disk sectors are each axially magnetized in the depth of the rotor disk so that one pole (e.g., a south pole) is located on one surface of the disk sector and the other pole (e.g., a north pole) is located on the opposite surface of the disk sector.

[0047] The two magnetic rotor discs are positioned with a fixed angular displacement relative to each other. Preferably, each disc sector of one rotor disc completely overlaps a disc sector of the other rotor disc. The surfaces of the aligned disc sectors can have the same magnetic poles or opposite magnetic poles. This means that a sector of one rotor disc with axial NS polarization can be aligned with a sector of the other rotor disc with axial NS polarization or axial SN polarization.

[0048] The disc sectors of the magnetic rotor disc may be equal to twice the number of radial portions of the stator teeth.All radial portions of the ferromagnetic teeth of the stator should be positioned to interact with disc sectors of the rotor disc that each provide the same magnetic pole (ie, south or north).

[0049] In a preferred embodiment, a central rotor disc is layered between two magnetic rotor discs. The central disc is arranged to fix the magnetic rotor discs in their angular position. Preferably, the central disc is made of a ferromagnetic material such as steel or iron. The ferromagnetic central disc participates in the magnetic field of the magnetic rotor discs. In particular, the ferromagnetic central disc helps to direct the magnetic flux of the magnets radially towards the central axis of the rotor.

[0050] When current flows to the electromagnetic stator coils, each of them provides a magnetic phase. The rotational movement of the two-phase stepper motor is driven by alternating the phases of the stator. Under the excitation of the current, the coils temporarily polarize the stator teeth to either the south or north pole. The magnetic force is concentrated in the stator teeth, which attract the disk sectors with opposite polarization on the face of the rotor disk. The alternating polarization of the two stators can drive the stepwise angular displacement of the rotor disk and the extension of the central axis to which the rotor is fixed.

[0051] The rotation of the rotor can be driven in one predefined direction. It is also possible that the stepper motor is driven bidirectionally.

[0052] The teeth of the stator can be irregularly spaced. In this embodiment, all radial portions of the teeth of the stator will still be positioned to interact with the disc sectors of the rotor disc that each have the same magnetic pole, however, at least one of the teeth may overlap slightly with the adjacent disc sector of the opposite pole. The irregular spacing between the teeth generates torque even when no current is temporarily provided to the coil. The torque generated in this way smoothes the sudden step-by-step movement of the rotor in accordance with the provision of alternating current. Therefore, the rotational speed of the rotor is made more stable. The stepper motor runs more smoothly without stagnation.

[0053] The irregular spacing of the teeth also provides the advantage that the rotor can be easily turned or its position adjusted when no current is supplied to the stepper motor. In embodiments where the regularly spaced teeth are perfectly aligned with the polarized rotor disk sectors, resistance needs to be overcome to move the rotor segments out of their aligned position. This is not the case when the alignment is imperfect, i.e., if at least some of the teeth overlap with unequally sized portions of two adjacent disk sectors, such as is the case with irregularly spaced teeth. The imperfect alignment results in a less stable angular position of the rotor, so that this position can be smoothly changed manually, for example by rotating the central axis, when no current is applied.

[0054] In a preferred embodiment, electrical traces for transmitting input / output signals to and optionally from the stepper motors are arranged in one or more flexible printed circuit boards (PCBs). The traces may be arranged, for example, in the front flexible PCB and the rear flexible PCB.

[0055] One or both end portions of the flexible PCB may have a ring shape, preferably matching the face of the cylindrical coil it is arranged in. In this embodiment, the central axis passes through the ring-shaped end portions of the flexible PCB.

[0056] One or both end portions of the flexible PCB may also have a curved shape, which preferably matches the curvature of the face of the cylindrical coil on which it is arranged.

[0057] The flexible PCB may have different types of ends, such as a toroidal end portion and another curved end portion.

[0058] Portions of the flexible PCB may be received along the length of the stator into recesses on the cylindrical surface of the stator.

[0059] The traces of the flexible PCB may be electrically connected to each other and / or to the electromagnetic coil.

[0060] The electrical connection may be provided, for example, by soldering.

[0061] The front flexible PCB may include a first end portion electrically connected to the first side of the front coil and a second end portion disposed on the second side of the rear stator.

[0062] As used herein, the first side of the coil is the side facing the rotor disk.As used herein, the second side of the coil is the side facing away from the rotor disk.

[0063] The second end portion of the front flexible PCB is preferably secured to the second face of the rear stator, for example by means of a suitable adhesive.

[0064] The rear flexible PCB can be configured to provide current to the coil. For this purpose, the rear flexible PCB should be electrically connected to the rear coil, the front flexible PCB and an external power source.

[0065] The rear flexible PCB may include a first end portion for electrically connecting the PCB with a first side of a coil (rear coil) housed in the rear stator.

[0066] The second end portion of the rear flexible member is preferably configured to input and optionally output electrical signals.

[0067] In one embodiment, the rear flexible PCB further comprises a middle annular portion adapted to be electrically connected to the front flexible PCB.The middle portion may be arranged on, preferably fixed to, the second face of the rear stator, wherein the central axis passes through the annular portion.

[0068] The intermediate section may, for example, be arranged on a stator yoke or a suitable covering member (eg a flange disk) covering the second face of the stator.

[0069] The intermediate section should be arranged on the second face of the rear stator or a suitable cover thereof or attached thereto without establishing an electrical connection with the stator.

[0070] The second end of the front-flex PCB is preferably electrically connected (eg, soldered) to the middle section of the rear-flex PCB.

[0071] In this embodiment, the rear flexible PCB preferably includes a first longitudinal portion arranged parallel to the central axis and extending along the outer surface of the rear stator from the first end portion to a middle portion of the rear flexible PCB.

[0072] The rear flexible PCB of this embodiment may further include a second longitudinal portion folded toward the front stator on an edge of the second face of the rear stator. The second longitudinal portion may extend beyond the front stator in the longitudinal direction of the assembled motor so that the free end of the rear flexible PCB can be used for external electrical connection.

[0073] The assembled stepper motor can be surrounded by an outer sheath. The sheath preferably has a hollow cylindrical shape for enclosing the stator, rotor, spacer, and optionally at least part of the wires or flexible PCB. Preferably, the two stators, rotor and spacer are completely covered by the outer sheath. The outer sheath should preferably be made of a protective durable material (such as stainless steel). To keep the size of the stepper motor compact, the thickness of the outer sheath should be 0.05mm to 0.5mm, or 0.1mm to 0.3mm. Preferably, the outer sheath should be waterproof or water-resistant.

[0074] The stepper motor of the present invention may further include an angular encoder. The angular encoder may be mounted on a flexible PCB, for example. The encoder may be used to determine the angular velocity, angular acceleration and / or angular position of the central axis or the rotor.

[0075] The stepper motor of the present invention may also include a magnetic field sensor. The magnetic field sensor may be mounted on a flexible PCB. The advantage of this sensor is that the field strength can be monitored. In this way, the current applied to the coil can be adjusted to achieve the desired field strength. An additional advantage of monitoring the magnetic field strength is that defects in the coil can be easily detected. Therefore, the coil can be repaired or replaced to ensure continued performance of the motor.

[0076] The stepper motor of the present invention is a compact stepper motor. Preferably, the maximum outer diameter of the stepper motor is 3 mm to 70 mm, preferably 4.5 mm to 22 mm.

[0077] The invention also relates to a method for assembling a stepper motor as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Exemplary embodiments of the present invention are disclosed in the description and illustrated in the accompanying drawings, in which:

[0079] Figure 1 schematically illustrates a three-dimensional exploded view of an embodiment of a stepper motor according to the present invention;

[0080] Figure 2A A three-dimensional exploded view showing the rotor disk and central shaft;

[0081] Figure 2B A three-dimensional view showing a rotor disk rotationally fixed about a central axis;

[0082] Figure 3A A three-dimensional exploded view showing the front stator and front coil;

[0083] Figure 3B Show Figure 3A 3D view of the assembled front stator;

[0084] Figure 4A A three-dimensional exploded view showing the rear stator and rear coil;

[0085] Figure 4B Show Figure 4A A three-dimensional view of the assembled rear stator, wherein the first longitudinal section follows the guide recess toward the second face of the stator;

[0086] Figure 4C Show Figure 4A A three-dimensional view of the assembled rear stator, wherein the middle portion of the rear flexible PCB is arranged on the second side (not visible) of the stator;

[0087] Figure 5A shows a three-dimensional view from the rear end of an embodiment of an assembled stepper motor with an outer sheath according to the present invention; and

[0088] Figure 5B A three-dimensional view from the front end of an embodiment of an assembled stepper motor with an outer sheath according to the invention is shown. DETAILED DESCRIPTION

[0089] exist Figure 1A possible embodiment of a stepper motor 100 according to the invention is shown in FIG. The figure depicts a schematic exploded view of the motor. The embodiment comprises a rotor 4 having a plurality of disk sectors (in the example shown, ten disk sectors). These sectors are magnetized alternately to opposite poles, i.e. north and south poles. The rotor is rotationally fixed to a central axis 1. The central axis 1 runs along the entire length of the stepper motor 100.

[0090] The central shaft 1 axially passes through the front stator 2A and the rear stator 2B, each of which includes a stator yoke 20A, 20B. The two stators each contain a coil, respectively, the front coil and the rear coil. The central shaft 1 passes through the core of each coil so that it can rotate axially inside the coil.

[0091] The stepper motor shown here comprises a front flexible PCB 6 and a rear flexible PCB 7. The stepper motor also comprises a stator support member 91 such as a bearing.

[0092] The outwardly facing surface of the rear stator yoke 20B and / or the front stator yoke 20A is preferably covered by a cover member 24. The cover member can serve as a surface for connecting the motor to an external structure. The cover member 24 can also serve as an interface with a gearbox, an adapter or other units.

[0093] The covering member is preferably disc-shaped. The covering member may be a supporting flange member such as Figure 1 and Figure 4A as shown in .

[0094] The distance between the two stators and their mutual angular alignment are fixed by a spacer 5. The spacer shown here has a central annular portion and projections 51, each of which is compatible with the area between two adjacent stator teeth. The shape of the projections 51 is complementary to the shape of the recesses between the stator teeth 250, so that the spacer 5 matches the shape of the two stators. It thus fixes the stators in their angular position.

[0095] However, the spacer 5 is not limited to the specific shape shown in this figure. The number of projections of the spacer can, for example, be less than the number of recesses between the stator teeth. Alternating projections and recesses in the spacer and stator can also be foreseen to fix the angular position of the stators relative to each other.

[0096] The spacer 5 should be sized so that it creates a distance between the stators 2A, 2B that is large enough to permit the rotor 4 to be layered between the stators. The spacer 5 should be sized and arranged so that no one rotor face contacts the stators 2A, 2B. The gap between the rotor 4 and the stator phases 2A, 2B is important to avoid the polarized stator teeth sticking to the magnetic rotor and thus preventing the motor from rotating.

[0097] exist Figure 2A and Figure 2BThe rotor is shown in more detail in FIG. Figure 2A An exploded view of the rotor is shown, which in this embodiment comprises three discs. The two outer discs 41 each comprise magnetised disc sectors 45 of alternating polarity. The centre disc 42 separates the magnetic discs 41 and is preferably made of a magnetic material, such as a ferromagnetic material like steel or iron.

[0098] This is shown in Figure 2B middle, Figure 2B The assembled rotor 4 is shown fixed to the central shaft 1. The disk sectors 45 providing one magnetic pole (eg, the north pole) are shown in white, while the disk sectors 45 providing the other magnetic pole (eg, the south pole) are shown as striped areas.

[0099] In the assembled motor, the rotor disc may be secured to the central shaft by means of rotor support members 47 .

[0100] Possible embodiments of the front and rear stators are shown in more detail in the subsequent figures.

[0101] In these embodiments, the stator coils 3 are electrically connected via flexible PCBs 6 and 7, which is a preferred option for providing current to the coils. Although the flexible PCBs are used to provide input signals and current to the coils, the flexible PCBs can also be used to receive signals from electronic components or sensors located in the motor and output these signals through external connections.

[0102] The flexible PCB may for example comprise an angular encoder or be connected to an angular encoder.The flexible PCB may also comprise a sensor or be connected to a sensor, such as a magnetic field sensor or a temperature sensor.

[0103] Figure 3A and Figure 3B A three-dimensional view of a possible embodiment of the front stator 2A with the front flexible PCB 6 is shown.

[0104] Figure 4A , Figure 4B and Figure 4C A possible embodiment of the rear stator is shown.

[0105] The front stator 2A and the rear stator 2B each include a stator yoke 20A, 20B. The front stator 2A and the rear stator 2B of the illustrated embodiment also include a stator flange with an axial cylindrical flange member 23, around which the electromagnetic coil 3 is placed. In the illustrated embodiment, these stator flanges each also include a disc-shaped support member 24 for supporting the mounted coil. The support member 24 acts as a covering member of the stator.

[0106] In an alternative embodiment, the cylindrical flange member 23 and the cover member are provided as separate elements, which may optionally be reversibly connected to each other.

[0107] The stator yokes 20A, 20B are generally cylindrical in shape, with a recess 22 along their outer surface for guiding a portion of the flexible PCB in the assembled motor.

[0108] The stator yokes 20A, 20B each comprise an annular portion 200 oriented away from the rotor in the assembled motor and a plurality of teeth 250 , in the example shown, each stator yoke 20A, 20B having five teeth.

[0109] The teeth of this embodiment have a longitudinal portion 252, which, in the assembled motor, extends from the cylindrical lateral surface of the annular portion toward the rotor. The stator teeth 250 also include radial portions 251, which, in the assembled motor, each extend perpendicularly from the longitudinal portion 252 toward the geometric center axis of the stator, or toward the center axis 1.

[0110] exist Figure 3A and Figure 3B A possible embodiment of a front flexible PCB 6 is also shown in FIG. The front flexible PCB 6 comprises a first toroidal end portion 61 and a second curved end portion 62. The two end portions are connected by an intermediate longitudinal portion.

[0111] The first end portion 61 is electrically connected to a first face of the electromagnetic coil, which face is the face facing the rotor 4 in the assembled motor.

[0112] Generally, the electrical connection can be established by soldering the flexible PCBs to each other or to the coils. For this purpose, the end sections can include soldering points 99.

[0113] Figure 3B The assembled front stator is shown with the first end of the front flexible PCB soldered to the first face of the coil. The middle part of the front flexible PCB 6 is folded upwards. This middle part is arranged in the longitudinal direction of the stepper motor, in the direction of the rear stator in the assembled motor. The middle part should be sized so that the second end part 62 of the front flexible PCB can be arranged on the second face of the rear stator, the second face of the stator being the face facing away from the rotor in the assembled motor.

[0114] These Figure 4A , Figure 4B and Figure 4CThe rear stator yoke 20B shown in FIG. 2 is identical to the front stator yoke 20A. Both stators 2A, 2B have an axial cylindrical flange member 23, however, the outer face of the disc-shaped flange member 24 of the rear stator is preferably flat. The flat outer face is better suited for arranging the fixed parts of the front and rear flexible PCBs, as shown in the drawings, especially Figure 1 The support member 24 of the rear stator yoke also comprises lateral recesses which can be aligned with the guide recesses 22 of the stator to guide the longitudinal portion of the flexible PCB.

[0115] FIG. 4A to FIG. 4C A possible embodiment of a rear flexible PCB 7 shown in FIG. 7 comprises a first toroidal end portion 71 , a toroidal middle portion 70 and a second end portion 72 for external electrical connection.

[0116] The first longitudinal portion 76 extends between the first end portion 71 and the middle portion 70. The second longitudinal portion 77 extends between the middle portion 70 and the second end portion 72.

[0117] like Figure 4A As shown in , the first end portion 71 is arranged on a first face of the electromagnetic coil 3 accommodated in the rear stator 2B and is electrically connected thereto.

[0118] The first longitudinal portion 76 is folded over the edge of a first face of the coil 3 and is guided by the guide recess 22 along the surface of the rear stator yoke 20B towards its second face which, in the assembled motor, is oriented away from the rotor.

[0119] The middle portion 70 can then be folded onto the second face of the rear stator at the edge of the lateral cylindrical surface.

[0120] exist Figure 4C 2B with the rear flexible PCB 7. The middle portion 70 is arranged on, preferably adhered to, the lower side of the stator shown here, which is the second face of the stator 2B. The second longitudinal portion 77 and the second end portion 72 are free for further arrangement and connection.

[0121] The second longitudinal portion 77 can provide the extension required to connect the PCB to an external power source. Optionally, the second longitudinal portion 77 can be folded over the edge of the second face of the rear stator so as to be longitudinally arranged along the cylindrical surface of the assembled motor in the direction of the front stator 2A and beyond the front stator 2A. The second longitudinal portion 77 thus arranged can be guided by the guide recess 22 included in the outer surface of the stator yoke 20A, 20B.

[0122] The motor may be encased by an outer sheath 8. The sheath is used to protect the motor from environmental influences. The sheath may be waterproof or water resistant to protect the electromagnetic components from moisture. The outer sheath 8 preferably has a cylindrical shape to match the shape of the rotor housed therein. Optionally, the sheath 8 may include a cover 95 on either end of its cylindrical shape so that the stepper motor can be sealed inside the sheath with only the required wires, cables or flexible PCB extending outwardly.

[0123] Figure 5A and Figure 5B The embodiment illustrated in shows a stepper motor housed in a housing 8 with a cover 95. The rear flexible PCB protrudes outwardly through the housing to enable electrical connections to the motor.

[0124] The two-phase stepper motor of the present invention, and in particular the embodiment presented in the drawings, can be assembled according to the steps set forth below.

[0125] To assemble the front stator 2A, the front flexible PCB 6, preferably the first end portion 61 thereof, is electrically connected, preferably soldered, to the first face of the coil 3. Then, the coil 3 is inserted into the front stator 2A so that the first face of the coil 3 is adjacent to the radial portion 251 of the stator tooth.

[0126] Optionally, a coil may be installed around a hollow cylindrical flange member 23 of the stator yoke 20A, 20B into which the center shaft 1 is inserted.

[0127] To assemble the front stator 2B, the rear flexible PCB 7, preferably its first end portion 71, is electrically connected, preferably soldered, to the first face of the second coil 3. The second coil is then inserted into the rear stator so that the first face of the coil is adjacent to the radial portion of the stator teeth.

[0128] Then, the center shaft 1 is axially inserted into the stator through the core of the coil accommodated in the front stator.

[0129] In a subsequent step, the rotor 4 is mounted on the central shaft 1 so that it is rotationally fixed to this shaft, so that the radial portion of the teeth 251 of the front stator faces the rotor and so that the rotor 4 does not touch said radial portion.

[0130] Optionally, spacer members may be temporarily inserted to ensure that a minimum distance between the rotor 4 and the front stator is maintained during assembly thereof.

[0131] Then, the spacer 5 can be arranged onto the front stator 2A and around the rotor 4. The spacer 5 should be arranged so that the front flexible PCB 6, in particular the longitudinal portion thereof, protrudes outward between the front stator 2A and the spacer 5.

[0132] The rear stator 2B accommodating another coil 3 is mounted on the shaft so that the radial portion of the teeth of the rear stator faces the rotor so that the rotor does not contact the radial portion and so that the rear flexible PCB protrudes outward between the rear stator and the spacer.

[0133] Optionally, the coils may be mounted around a hollow cylindrical flange member 23 of the stator 2A, 2B into which the central shaft 1 is inserted. The flange member 23 should include a central opening through which the central shaft 1 may pass. Preferably, the flange member 23 of the rear stator serves as a support member 24 having a flat disc-shaped outer surface adapted to cover the second face of the open cylindrical shape of the rear stator. The flat disc-shaped outer surface should be adapted to attach a flexible PCB.

[0134] Once the two stators 2A, 2B have been mounted on the central shaft 1, the front flexible PCB 6 and the rear flexible PCB 7 are folded towards the second face of the rear stator 2B, which is the face facing away from the rotor 4. The second end portion 62 of the front flexible PCB and the middle section 70 of the rear flexible PCB are arranged on the second face of the rear stator. The second face of the rear stator may be the outer surface of the support member 24. Preferably, the middle section 70 of the rear flexible PCB may be fixed to the second face of the rear stator, for example by means of an adhesive.

[0135] Then, the front flexible PCB 6, preferably the second end portion 62 of the front flexible PCB is electrically connected (preferably soldered) to the rear flexible PCB 7, preferably the middle portion 70 of the rear flexible PCB.

[0136] A portion of the rear flexible PCB extends from the second surface of the rear stator 2B to achieve electrical connection with an external device.

[0137] Optionally, the rear flexible PCB 7 can be folded on the edge of the second face of the rear stator 2B so that the rear flexible PCB 7, preferably the second longitudinal portion of the rear flexible PCB 77, extends beyond the front stator 2A along the longitudinal direction of the assembled motor. The rear flexible PCB 7 can be guided along the lateral surface of the substantially cylindrical assembled motor by the guide recess 22.

[0138] The motor thus assembled may optionally be inserted into an outer sheath 8. The portion of the rear flexible PCB 7 which is folded back over the rear stator edge to run along the length of the assembled stepper motor is preferably also housed inside the outer sheath 8.

[0139] Reference numerals

[0140] 1 Central axis

[0141] 2 Stator

[0142] 2A front stator

[0143] 2B rear stator

[0144] 3 Coils

[0145] 3A front coil

[0146] 3B rear coil

[0147] 4 Rotor

[0148] 5 Spacers

[0149] 51 Spacer protrusion

[0150] 20A front stator yoke

[0151] 20B Rear stator yoke

[0152] 22 Guide recess

[0153] 23 Cylindrical flange component

[0154] 24 Support flange member

[0155] 200 Annular part of stator yoke

[0156] 250 stator teeth

[0157] 251 Longitudinal section of stator tooth

[0158] 252 Radial part of stator teeth

[0159] 41 Magnetic rotor disc

[0160] 42 Center rotor disc

[0161] 45 disc sectors of the magnetic rotor disc

[0162] 47 Rotor disc support

[0163] 6 front flexible PCB

[0164] 61 First end portion of the front flexible PCB

[0165] 62 Second end portion of the front flexible PCB

[0166] 7. Flexible PCB

[0167] The middle part of the flexible PCB after 70

[0168] 71 First end portion of the rear flexible PCB

[0169] 72 The second end portion of the rear flexible PCB

[0170] 76 The first longitudinal section of the rear flexible PCB

[0171] 77 The second longitudinal section of the rear flexible PCB

[0172] 8 Outer sheath

[0173] 91 Bearings

[0174] 93 Rear flange disc

[0175] 95 Motor cover disc

[0176] 99 brazing points

[0177] 100 Stepper Motor

Claims

1. A two-phase stepper motor (100), comprising: - a central axis (1), - two coils (3), - two ferromagnetic stators (2A, 2B), each housing one of said coils (3), The central shaft (1) passes through each of the two coils (3), thereby permitting the central shaft (1) to rotate within the stator (2A, 2B), - a rotor (4) rotationally fixed on said central shaft (1) and positioned between said two stators (2A, 2B), said rotor (4) having two faces, each of which is magnetized, and - a spacer (5) arranged between said stators (2A, 2B) for maintaining the two stators at a fixed minimum distance from each other, in, Each of the two stators (2A, 2B) comprises an annular portion arranged around one of the coils and at least two teeth (250) extending from the annular portion, each tooth comprising a radial portion (251) extending radially between one of the coils (3) and the rotor (4) in the direction of the central axis (1), and In this case, the temporarily polarized stator teeth all have the same polarity.

2. The stepper motor according to claim 1, wherein: The teeth (250) each comprise a longitudinal portion (252) extending parallel to the central axis (1) towards the rotor (4) as a continuation of the annular portion of the stator (2A, 2B), and wherein the radial portion (251) is perpendicular to the longitudinal portion (252).

3. The stepper motor according to any one of claims 1 to 2, wherein the two stators (2A, 2B) are identical, wherein: The teeth of one stator are angularly offset relative to the teeth of the other stator.

4. The stepper motor according to any one of claims 1 to 3, wherein: The spacer (5) comprises an annular portion made of insulating material.

5. The stepper motor according to any one of claims 1 to 4, wherein: The spacers (5) are arranged to maintain an angular offset of the teeth (250) of the two stators (2A, 2B) such that the angular position of the stators relative to each other is fixed.

6. The stepper motor according to any one of claims 1 to 5, wherein: The spacer (5) has a projection (51) which engages between at least one pair of longitudinal portions (252) of adjacent teeth of each stator.

7. The stepper motor according to any one of claims 1 to 6, wherein: The rotor (4) comprises two magnetic disks (41), each magnetic disk (41) comprising disk sectors (45), wherein each disk sector (45) is polarized to a first magnetic pole, such as a north pole, and wherein its adjacent magnetic regions are polarized to an opposite magnetic pole, such as a south pole, so that magnetic south poles and magnetic north poles alternate in the disk sectors (45) of the magnetic rotor disk (41).

8. The stepper motor according to claim 7, wherein: The radially magnetized rotor disks (41) are angularly displaced relative to each other.

9. The stepper motor according to any one of claims 1 to 8, wherein: The teeth (250) of the stator (2A, 2B) are irregularly spaced.

10. The stepper motor according to any one of claims 1 to 9, wherein: The two coils (3) are each connected to electrical wires arranged in one or more flexible printed circuit boards (PCB) (6, 7).

11. A stepper motor according to claim 9, comprising a front flexible PCB (6) having a first end portion (61) and a second end portion (62), the first end portion (61) being electrically connected to a first face of a coil housed in one of the stators, for example soldered thereto, the stator being a front stator (2A), the first face of the coil or the stator being the face facing the rotor disc, the second end portion (62) being arranged on, preferably fixed to, a second face of the other stator, the other stator being a rear stator (2B), the second face of the coil or the stator being the face facing away from the rotor disc (41).

12. The stepper motor according to claim 10 or 11, further comprising a rear flexible PCB (7) configured to provide current to the coil (3), wherein The rear flexible PCB (7) is electrically connected to the front flexible PCB (6), wherein a first end portion (71) of the rear flexible PCB is electrically connected to a first side of a coil accommodated in the rear stator (2B), and wherein a second end portion (72) of the rear flexible PCB is configured to input and optionally output electrical signals.

13. The stepper motor according to claim 12, wherein the rear flexible PCB (7) further comprises a toroidal middle portion (70), the toroidal middle portion (70) being electrically connected to the front flexible PCB (6) and arranged on, preferably fixed to, the second face of the rear stator (2B), wherein: The central axis (1) passes through the middle portion (70).

14. The stepper motor according to claim 13, wherein the rear flexible PCB (7) further comprises a first longitudinal portion (76) and a second longitudinal portion (77), wherein the first longitudinal portion (76) is arranged parallel to the central axis (1) and extends along the outer surface of the rear stator (2B) from the first end portion (71) to the middle portion (70) of the rear flexible PCB, and the second longitudinal portion (77) extends on the edge of the second face of the rear stator (2B), so that the free end portion (72) of the rear flexible PCB can be used for external electrical connection.

15. A method for assembling a stepper motor (100) according to any one of claims 1 to 14, comprising the following steps (i) electrically connecting, preferably soldering, a front flexible PCB (6) to a first side of a coil, said coil being the front coil; (ii) inserting the front coil into a stator, namely the front stator (2A), so that the first face of the front coil is adjacent to a radial portion (251) of a stator tooth, the radial portion pointing radially inward from the outer periphery of the front stator (2A); (iii) electrically connecting, preferably soldering, the rear flexible PCB (7) to the first side of another coil, the other coil being the rear coil; (iv) inserting the rear coil into a second stator, which is the rear stator (2B), so that a first face of the rear coil is adjacent to a radial portion (251) of a stator tooth, the radial portion being directed radially inward from an outer periphery of the rear stator (2B); Wherein, steps (i) and (ii) may also be implemented after steps (iii) and (iv), (v) installing a front stator (2A) with the front coil around the central axis (1); (vi) rotatably fixing the rotor (4) to the central shaft (1) so that the radial portion (251) of the teeth of the front stator (2A) faces the rotor (4) and so that the rotor does not contact the radial portion (251), (vii) arranging a spacer (5) onto the front stator (2A) and around the rotor (4) so ​​that the front flexible PCB (6) protrudes outward between the front stator (2A) and the spacer (5); (viii) mounting a rear stator (2B) with a rear coil around the central axis (1) so that the radial portion of the teeth (251) of the rear stator faces the rotor (4), so that the rotor (4) does not contact the radial portion (251), and so that the rear flexible PCB (7) protrudes outward between the rear stator (2B) and the spacer (5); (ix) folding the front flexible PCB (6) and the rear flexible PCB (7) toward a second surface of the rear stator (2B), the second surface facing away from the rotor (4); (x) arranging the free end portion (62) of the front flexible PCB (6) and the middle portion (70) of the rear flexible PCB (7) on the second surface of the rear stator (2B); (xi) electrically connecting the free end portion (62) of the front flexible PCB so arranged with the middle portion (70) of the rear flexible PCB so arranged.

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