Spindle motor with rotary encoder

Abstract

The invention relates to a spindle motor with encoder, comprising a stationary motor component (10, 14, 16; 24) and a rotatable motor component (18, 20, 22) which can be driven by an electromagnetic drive system (38, 40), wherein the encoder is a magnetic encoder and comprises at least one magnetic field sensor (44) which is arranged on the stationary motor component (10, 14, 16, 24) or a component (50) that is stationary relative to it, and which comprises an annular, multipole magnetized sensor magnet (46) which is arranged on the rotatable motor component (18, 20, 22) in the detection range of the magnetic field sensor (44), and wherein the sensor magnet (46) has a number of 2n magnetic poles, wherein the sector angle of one magnetic pole is α, and the sector angle β of the remaining 2n-1 magnetic poles is β = (360° - α) / (2n-1) is and where α is not equal to β.

Description

[0001] The invention relates to a spindle motor with rotary encoder according to the preamble of claim 1.

[0002] A brushless DC motor, in particular a spindle motor, with an optical encoder, e.g., for LiDAR applications, is known. In such motors, a so-called crown with N teeth and N openings is arranged on the rotor, wherein the position of the teeth and openings can be detected by at least one optical sensor, and the position of the rotor can be determined from this. Additionally, it may be provided that one tooth of the crown is wider than the others in order to obtain a reference position (zero position) of the rotor.

[0003] The orientation of the optical encoder used in LiDAR applications must be aligned with the orientation of the facets of the LiDAR system's mirror polygon. For this purpose, the optical encoder uses a specially designed mechanical crown, mounted on the rotor of the electric motor, and an optical sensor. Both components require a relatively large amount of space and a certain distance to ensure accurate optical detection. This makes it difficult to reduce the size of the motor and, consequently, the LiDAR system. Furthermore, optical encoders are susceptible to interference, as various factors such as dust, condensation, and external light (e.g., sunlight) or sudden changes in ambient brightness can impair their function.

[0004] US patent 2021 / 0408872A1 discloses a spindle motor with the features of the preamble of claim 1.

[0005] The object of the invention is to improve a spindle motor with rotary encoder with regard to the reliability of position determination and to reduce its size and manufacturing costs.

[0006] This problem is solved by a spindle motor with the features of claim 1.

[0007] Preferred embodiments of the invention and further advantageous features are described in the dependent patent claims.

[0008] The spindle motor according to the invention features a magnetic encoder, which is used instead of an optical encoder in order to minimize the encoder's footprint and reduce manufacturing costs. Furthermore, the use of a magnetic encoder reduces or completely eliminates the aforementioned factors influencing the encoder's functionality. In addition, a magnetic encoder can operate in a wider ambient temperature range than an optical encoder, which is advantageous for automotive applications.

[0009] The magnetic encoder comprises at least one magnetic field sensor. For example, a Hall sensor, a magnetoresistive sensor (MR sensor), or a giant magnetoresistive sensor (GMR sensor) can be used as the magnetic field sensor. The magnetic field sensor is positioned against a multipole, ring-shaped permanent magnet, hereinafter also referred to as the sensor magnet. The sensor magnet can be axially or radially magnetized and is preferably mounted on the rotating motor component of the spindle motor.

[0010] The magnetic field sensor can be integrated into any non-rotating motor component or housing component, e.g., into the motor flange or the electrical stator, or mounted on an electrical circuit board attached to the motor or externally. The magnetic field sensor can be positioned radially outside the outer diameter of the sensor magnet, radially inside the inner diameter of the sensor magnet, or axially below or above the sensor magnet.

[0011] The multipole sensor magnet is magnetized in a sector shape, whereby the magnetization shape (shape of the flux density) of the sensor magnet can be, for example, rectangular, sinusoidal or even arbitrarily shaped.

[0012] The number of magnetic poles in the multipole sensor magnet determines, among other things, the encoder's resolution. Its resolution can be 2n pulses, where n is a natural number and represents the number of magnetic pole pairs. The number of magnetic pole pairs in the sensor magnet is limited only by the physical dimensions / capabilities of the sensor magnet or the magnetization technique used.

[0013] The sensor magnet can, for example, be part of the motor drive's rotor magnet or a separate permanent magnet that can be attached directly to or near the rotor magnet. Ferromagnetic or non-ferromagnetic spacers can also be used between the sensor magnet and the rotor magnet.

[0014] The sensor magnet can be attached not only to the rotor magnet, but also to another suitable location on the rotating motor component or on a load component attached to the rotating motor component. It can be located on the rotor's outer diameter, the rotor's inner diameter, or on the top or bottom of the rotor.

[0015] To enable the detection of a full rotation of the rotor, the sensor magnet is preferably specially magnetized. For example, it is provided that at least one magnetic pole or pair of magnetic poles does not sweep the same sector angle as the other pole pairs of the multi-pole sensor magnet.

[0016] Preferably, the sensor magnet has a number of 2n magnetic poles, wherein the sector angle of one magnetic pole is α, and the sector angle β of the remaining 2n-1 magnetic poles is calculated as β=(360°−α) / (2n−1)

[0017] Preferably, for the magnetic field sensor to distinguish between magnetic poles with different sector angles, the difference angle δ between the sector angles α and β is between 1° and 4°, depending on the number of magnetic poles used in the sensor magnet. Typically, sensor magnets with n = 6 to n = 24 pole pairs, i.e., 2n = 12 to 2n = 48 magnetic poles, are used, in which case the following preferably applies: Difference angle δ=48° / 2n

[0018] The sector angle α, which differs from the sector angles β, is calculated as follows: α=β+ / −δ

[0019] Substituting equations 1 and 2 into equation 3 yields β=(360+ / −(48° / 2n)) / 2n

[0020] The rotatable motor component of the spindle motor can comprise a two-part hub with an inner hub component and an outer hub component, wherein the two hub components can be made of different materials. Preferably, the inner hub component is made of steel, as it is preferably a functional component of the fluid dynamic bearing system.

[0021] The outer hub component is made of a material that preferably has the same coefficient of thermal expansion as the rotatable load component attached to the outer hub component. The similar coefficients of thermal expansion of the outer hub component and the attached load component prevent stress and deformation of the load component due to changes in ambient temperature.

[0022] The stationary motor component has a motor base, wherein the magnetic field sensor is preferably arranged on an electrical circuit board mounted on the motor base. The magnetic field sensor preferably extends through an opening in the motor base and is positioned opposite the sensor magnet attached to the hub.

[0023] The spindle motor according to the invention can preferably be used to drive an optical scanner, in particular a LiDAR scanner. A LiDAR scanner has a polygon mirror rotatably driven by the spindle motor for deflecting a laser beam, wherein the polygon mirror is attached to the hub of the spindle motor and rotatably driven with the hub.

[0024] Preferably, the hub or an outer hub component of a two-part hub can be made of a material with the same coefficient of thermal expansion as the material of the polygon mirror, i.e., in particular, of aluminium.

[0025] The sensor magnet can preferably be arranged on the hub or on the polygon mirror.

[0026] The invention is described in more detail below with reference to several exemplary embodiments and the drawings. Fig. Figure 1 shows a section through a first embodiment of a spindle motor according to the invention. Fig. Figure 2 shows a section through a second embodiment of a spindle motor according to the invention. Fig. Figure 3 shows a section through a third embodiment of a spindle motor according to the invention. Fig. Figure 4 shows a section through a fourth embodiment of a spindle motor according to the invention. Fig. Figure 5 shows a section through a fifth embodiment of a spindle motor according to the invention. Fig. Figure 6 shows a section through a sixth embodiment of a spindle motor according to the invention. Fig. Figure 7 shows a section through a seventh embodiment of a spindle motor according to the invention. Fig. Figure 8 schematically shows one possible way of magnetizing the sensor magnet. Fig. Figure 9 schematically shows another type of magnetization of the sensor magnet. Fig. Figure 10 shows a section through another embodiment of a spindle motor according to the invention. Fig. Figure 11 shows a top view of the motor base of the spindle motor of Fig. 10 Fig. Figure 12 shows a section through another embodiment of a spindle motor according to the invention. Fig. Figure 13 shows a section through another embodiment of a spindle motor according to the invention. Fig. Figure 14 shows a section through another embodiment of a spindle motor according to the invention.

[0027] In the Fig. Figures 1 to 7 show cross-sectional views of various spindle motor configurations. The spindle motors are essentially identical in design and comprise the same components. Each spindle motor consists of a stationary motor component and a rotatable motor component, which is rotatably mounted relative to the stationary motor component about a rotational axis 36 by means of a fluid dynamic bearing system. The rotatable motor component is driven by an electromagnetic drive system. The spindle motors are preferably designed as external rotor motors.

[0028] The general structure of spindle motors is described using the following examples: Fig. 1 described. The basic structure described also applies to those described in the Fig. 2 to 7 spindle motors shown.

[0029] The stationary motor component of the spindle motor comprises a motor base 10 with a cylindrical receiving opening 12 in which the components of the fluid dynamic bearing system are accommodated. The fluid dynamic bearing system comprises a cylindrical sleeve 14 which is fastened in the receiving opening 12 of the motor base 10, for example by means of a press fit and / or adhesive bond.

[0030] A cylindrical bearing bushing 16 is received in the cylindrical sleeve 14 and secured in the sleeve 14 by means of a press fit and / or adhesive bond, the length of the bearing bushing 16 being slightly shorter than the length of the sleeve 14. The sleeve 14 and the bearing bushing 16 are part of the stationary motor component.

[0031] The rotatable motor component comprises a cylindrical shaft 18, which is rotatably mounted in a bearing bore of the bearing bushing 16. A hub 20 is attached to a free end of the shaft 18 that protrudes from the bearing bore.

[0032] At the other end of the shaft 18 a pressure plate 22 is attached, which is arranged in an annular free space between the sleeve 14, the bearing bushing 16 and a cover 24 closing the sleeve 14 and is rotatable together with the shaft 18.

[0033] The sleeve 14, the bearing bushing 16, the shaft 18, the pressure plate 22, and the cover 24 form the components of the fluid dynamic bearing system. A bearing gap 26 filled with bearing fluid separates the surfaces of the stationary sleeve 14, the stationary bearing bushing 16, and the stationary cover 24 from the surfaces of the rotatable shaft 18 and the rotatable pressure plate 22. The open end of the bearing gap 26 is sealed by a capillary sealing gap 28 to prevent the escape of bearing fluid from the bearing gap 26.

[0034] Along an axially extending section of the bearing gap 26 between the shaft 18 and the bearing bushing 16, two fluid-dynamic radial bearings 29, 30 are arranged at a mutual axial distance. The fluid-dynamic radial bearings 29, 30 comprise bearing groove structures arranged on the inner circumferential surface of the bearing bore of the bearing bushing 12 or on the outer circumferential surface of the shaft 18 or on both of these circumferential surfaces. When the shaft 18 rotates in the bearing bushing 16, the bearing groove structures generate a hydrodynamic pressure in the axially extending section of the bearing gap 26.

[0035] Bearing groove structures are also arranged on the two end faces of the pressure plate 22, which together with an opposing end face of the bearing bushing 16 or an opposing end face of the cover 24 each form a fluid-dynamic axial bearing 32, 34. The fluid-dynamic axial bearings 32, 34 absorb the axial forces that act on the bearing along the axis of rotation 36.

[0036] The spindle motor is preferably designed as a brushless DC motor, also known as a BLDC (Brushless DC) motor. The electromagnetic drive system comprises a ring-shaped and sector-shaped multipole magnetized rotor magnet 38 and a stator assembly 40, which has several stator teeth wound with coils. The coils are driven such that a rotating excitation field (rotating magnetic field) is generated. The electrical stator assembly 40 is attached to the outer circumference of the mounting opening on the motor base 10. The stator assembly 40 can, for example, comprise twelve poles (slots), with the excitation windings preferably being connected to three phases.

[0037] The rotor magnet 38 is designed as a ring-shaped permanent magnet and is attached to an inner circumferential surface of the hub radially opposite the stator assembly 40. The rotor magnet 38 surrounds the stator assembly 40 and is separated from it by a radial air gap. The rotor magnet 38 can, for example, have eight magnetic poles (four pole pairs). If the hub 20 is made of a non-magnetic material, the rotor magnet 38 can be surrounded by a magnetic return ring 42.

[0038] According to the invention, the spindle motor has at least one magnetic encoder to determine the rotational speed of the spindle motor and / or its rotor position. The magnetic encoder comprises a magnetic field sensor 44, which is arranged, for example, axially below the rotor magnet 38 on the motor base 10. The magnetic field sensor 44 can be arranged on a printed circuit board 48, which is also located on the motor base 10.

[0039] When the hub 20 rotates, the rotor magnet 38 attached to the hub 20 rotates over the magnetic field sensor 44, which detects the changing polarity of the magnetic field of the rotor magnet 38 as it passes over it. The eight-pole rotor magnet 38 has eight sector-shaped magnetized poles with alternating north-south magnetization. The magnetic field sensor 38 generates electrical output pulses with alternating electrical polarity from the changing magnetic field. The rotational speed and the relative position of the rotor magnet 38, and thus of the hub 20, can be determined from the changing polarities of the output signals.

[0040] At the in Fig. In the spindle motor shown in Figure 1, the rotor magnet 38 serves not only as a drive magnet for driving the hub 20, but also as a sensor magnet 46 for detecting the position of the rotating motor component, in particular the hub 20.

[0041] One disadvantage of the arrangement of Fig. 1 is that the rotor magnet 38 is usually uniformly magnetized, meaning that each magnetic pole has the same sector angle. With eight magnetic poles, this sector angle is 360° / 8 = 45°.

[0042] Therefore, it is not readily possible to detect the absolute position of the rotating motor component relative to the stationary motor component using the magnetic field sensor 44, since no reference position or zero position of the sensor magnet 46 relative to the magnetic field sensor 44 can be defined which could be repeatedly detected by the magnetic field sensor 44.

[0043] Fig. Figure 2 shows an embodiment of the invention in which a separate sensor magnet 46 is used to control the magnetic field sensor 44. The sensor magnet 46 is attached directly axially below and adjacent to the rotor magnet 38 on the inner circumferential surface of the hub 20. Preferably, the sensor magnet 46 is magnetized axially and sector-shaped and preferably has a significantly higher number of magnetic poles than the rotor magnet 38. For example, the sensor magnet 46 can have 12, 16, or 24 magnetic poles. The higher the number of magnetic poles of the sensor magnet 46, the higher the achievable angular resolution of the encoder. The magnetic field sensor 44 is as shown in Figure 2. Fig. 1 axially below the sensor magnet 46 on the motor base 10.

[0044] The sensor magnet 46 preferably has a special magnetization that allows the magnetic field sensor 44 to repeatedly detect an absolute position of the sensor magnet 46 and thus also of the hub 20.

[0045] A possible magnetization of the sensor magnet 46 is in Fig. Figure 8 shows the sensor magnet being magnetized in a sector shape and has, for example, a total of 12 magnetic poles and thus 6 magnetic pole pairs. Each magnetic pole pair sweeps out an equal sector angle of 360° / 6 = 60°. With the exception of one magnetic pole pair, the respective north and south poles of the magnetic pole pairs are also divided into equally large sector angles of 60° / 2 = 30°.

[0046] In one pair of magnetic poles of the sensor magnet 46, the sector angle of the north pole is significantly smaller than the sector angle of the south pole, or vice versa. For example, the north pole has a sector angle of 20°, while the south pole has a sector angle of 40°. The different sector angles of 20° and 40° of the magnetic poles of this pair of magnetic poles are detected by the magnetic field sensor 44 and differ from the remaining magnetic poles or pairs of magnetic poles, which all have a sector angle of 30° and 60°, respectively. Consequently, the period of the output pulses of the magnetic field sensor 44 generated by these magnetic poles with different sector angles differs from the period of the output pulses of the magnetic field sensor 44 generated by the other magnetic poles. From this, a reference position (zero position) of the sensor magnet 46 can be defined, which can be detected repeatedly with each revolution of the rotor.

[0047] In Fig. Figure 9 shows another type of magnetization of the sensor magnet 46, which has a total of 12 magnetic poles. Here, the sector angle of only one magnetic pole, for example, a north pole, differs from the sector angles of all other magnetic poles, so that this "reference position" of the north pole of the sensor magnet 44 can be detected based on the different output pulse of the magnetic field sensor 44. While a magnetic north pole has a sector angle α, the remaining angle is divided equally among the remaining magnetic poles.

[0048] For example, a magnet's north pole has a sector angle α of 19°. The remaining angle of 360° - 19° = 341° is divided equally among the remaining 11 magnet poles, so that each remaining magnet pole has a sector angle β = 341° / 11 = 31°. In general, β = (360° - α) / (2n-1), where the sensor magnet (46) has 2n magnet poles. In the present example, a relatively large difference angle δ = β - α = 12° was chosen to obtain integers for the sector angles α and β and to simplify the graphical representation. In practice, however, the difference angle δ can preferably be chosen to be significantly smaller and is between 1° and 4°.

[0049] The sensor magnet 46 can be magnetized in both radial and axial directions, depending on whether the magnetic field sensor 44 is positioned axially or radially with respect to the sensor magnet.

[0050] Fig. Figure 3 shows an embodiment of the spindle motor in which the sensor magnet 46 is arranged radially outside the rotor magnet 38 in a recess of the hub 20. The sensor magnet 46 is sector-shaped and magnetized in the axial direction. The magnetic field sensor 44 is arranged axially below the sensor magnet 46 on a circuit board 48 at the motor base 10.

[0051] Spindle motor from Fig. 4 The sensor magnet 46 is arranged radially outside the rotor magnet 38 on the outer circumferential surface of the hub 20. The sensor magnet 46 is sector-shaped and magnetized in the radial direction. The magnetic field sensor 44 is arranged radially outside the sensor magnet 46 on a surface that is fixed relative to the stationary motor component of the spindle motor, for example, on a device housing 50.

[0052] Fig. Figure 5 shows a spindle motor in which the sensor magnet 46 is arranged on the top and outer edge of the hub 20. The sensor magnet 46 is sector-shaped and magnetized in the axial direction. The magnetic field sensor 44 is arranged axially above the sensor magnet 46 on a surface that is fixed relative to the stationary motor component of the spindle motor, for example, on a device housing 50.

[0053] In Fig. Figure 6 shows that the sensor magnet 46 is arranged radially inside the top surface of the hub 20. The sensor magnet 46 is sector-shaped and magnetized in the axial direction. The magnetic field sensor 44 is arranged axially above the sensor magnet 46 on a surface that is fixed relative to the stationary motor component of the spindle motor, for example, on a device housing 50.

[0054] Fig. Figure 7 shows an identical positioning of the sensor magnet 46 as Fig. 6 on the top of the hub 20. The sensor magnet 46 is sector-shaped and magnetized in the radial direction. The magnetic field sensor 44 is arranged radially opposite the sensor magnet 46 on a surface that is fixed relative to the stationary motor component of the spindle motor, for example on a device housing 50.

[0055] The Fig. Figure 10 shows a section through a further embodiment of a spindle motor according to the invention, the bearing bushing 16 of which is fastened in a receiving opening of the motor base 10.

[0056] The shaft 18 of the spindle motor is rotatably supported by a fluid dynamic bearing system, which comprises two fluid dynamic radial bearings 29, 30 arranged between the outer circumferential surface of the shaft 18 and the inner circumferential surface of the bore of the bearing bushing 16. Furthermore, an upper end face of the bearing bushing 16 together with a lower end face of the hub 20 form a fluid dynamic axial bearing 32.

[0057] The continuous bearing gap 26, which is arranged between the bearing surfaces of the two radial bearings 29, 30 and the axial bearing 32, is filled with a bearing fluid and sealed by a capillary sealing gap 28. The capillary sealing gap 28 is bounded by an outer circumferential surface of the bearing bushing 16 and an inner circumferential surface of an axially extending wheel of the hub 20.

[0058] The sensor magnet 46 is arranged on an outer circumferential surface of the hub 20, opposite the top surface of the motor base 10. The magnetic field sensor 44 is arranged axially below the sensor magnet 46 on the stationary motor component. The magnetic field sensor 44 is mounted on a circuit board 48, which is attached to the underside of the motor base 10 and projects upwards through an opening 52 in the motor base 10 to below the sensor magnet 46. The connecting wires 54 for the motor windings of the stator assembly 50 are also electrically contacted on the circuit board 48. These wires are guided through the opening 52 and bores 56 in the motor base 10 to the circuit board 48. Further electronic components 58 may also be arranged on the circuit board 48.

[0059] The hub 20 of the spindle motor is driven by the electromagnetic drive system, consisting of stator assembly 40 and rotor magnet 38, and carries a load, which can be, for example, a so-called polygon mirror 60 of a laser scanner. The polygon mirror 60 sits on a horizontal flange on the outer circumferential surface of the hub 20 and is held in place by a clamp 62, which is fastened to the top of the hub 20 by screws 64.

[0060] Fig. Figure 11 shows a top view of the motor base of the spindle motor of Fig. 10, where the opening 52 in the motor base 10 and the circuit board 48 arranged below it can be seen, on the top of which the magnetic field sensor 44 is arranged, which protrudes through the opening 52.

[0061] Fig. Figure 12 shows a further embodiment of the invention, in which the spindle motor has a hub 20 consisting of two hub components 20a and 20b. An inner hub component 20a is attached to the shaft 18 and is preferably made of steel. The inner hub component 20a, together with the bearing bushing 16, forms a fluid-dynamic axial bearing 32 of the fluid-dynamic bearing system and the capillary sealing gap 28 for sealing the bearing gap 26. Furthermore, the inner hub component 20a carries the rotor magnet 38 on a radially inner circumferential surface and serves as a magnetic return, since it is made of magnetic steel.

[0062] The annular outer hub component 20b is attached to the outer circumference of the inner hub component 20a by means of a press fit and / or adhesive bond and is preferably made of aluminum, as is the polygon mirror 60 attached to the outer hub component 20b. By using aluminum for the outer hub component 20b and the attached polygon mirror 60, these components have the same coefficient of thermal expansion, thus preventing stresses and deformations due to unequal thermal expansion of the materials. However, the outer hub component 20b and the polygon mirror 60 can also be made of a different metal alloy, glass, or a suitable plastic.

[0063] The polygon mirror 60 sits on a horizontal flange on the outer circumferential surface of the outer hub component 20b and is held clamped on the outer hub component 20b by means of a clamp 62, which clamp 62 is fastened to the top of the outer hub component 20b by screws 64.

[0064] The sensor magnet 46 is attached to an inner circumferential surface of the outer hub component 20b, specifically to a lower edge of the outer hub component 20b, which is opposite the motor base 10. The magnetic field sensor 44 is arranged axially below the sensor magnet 46 and extends through an opening 52 in the motor base 10. The magnetic field sensor 44 is mounted on a circuit board 48, which is located on the underside of the motor base 10 and may be equipped with further electronic components 58. The winding wires 54 of the stator assembly 40, which pass through the opening 52 in the motor base 10, are also electrically contacted on the circuit board 48.

[0065] Fig. Figure 13 shows a similar embodiment of the invention as the Fig. 12, with the difference that the inner hub component 20a connected to the shaft 18 has a smaller diameter and, together with the bearing bushing 16, forms a fluid-dynamic axial bearing 32 of the fluid-dynamic bearing system and the capillary sealing gap 28 for sealing the bearing gap 26. The inner hub component 20a is preferably made of steel.

[0066] The annular outer hub component 20b is attached to the outer circumferential surface of the inner hub component 20a by means of a press fit and / or adhesive bond. The rotor magnet 38, together with a magnetic return ring 42, is attached to a radially inner circumferential surface of the outer hub component 20b. The magnetic return ring 42 is necessary because the outer hub component 20b is preferably not made of a ferromagnetic material and is, for example, made of aluminum.

[0067] Fig. Figure 14 shows an embodiment of a spindle motor according to the invention with a one-piece hub 20 similar to the spindle motor of Fig. 10.

[0068] Unlike Fig.In 10, the sensor magnet is not arranged on the hub 20 of the spindle motor, but on the load component attached to the hub 20, for example a polygon mirror 60. The sensor magnet 46 is arranged on the underside of the polygon mirror 60, with the magnetic field sensor 44 being arranged, for example, radially opposite the sensor magnet 46.

[0069] The advantage of this arrangement is that the sensor magnet 46 is located outside the spindle motor, and the magnetic field sensor 44 can also be located outside the motor compartment, either on the motor base or on an external circuit board. Therefore, no modifications to the spindle motor are necessary. List of reference symbols 10 Engine base 12 Intake opening 14 Sleeve 16 Bearing bushing 18 wave 20 hub 22 Printing plate 24 lids 26 bearing gap 28 capillary sealing gap 29 fluid dynamic radial bearing 30 fluid dynamic radial bearing 32 fluid dynamic axial bearing 34 fluid dynamic axial bearing 36 Rotation axis 38 Rotor magnet 40 Stator arrangement 42 Return ring 44 Magnetic field sensor 46 Sensor magnet 48 circuit boards 50 device housings 52 Breakthrough (circuit board) 54 connecting wire 56 bore 58 components 60 polygon mirrors, load-bearing component 62 bracket 64 screw QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] US 2021 / 0 408 872 A1

[0004]

Claims

[1] Spindle motor with encoder, comprising a stationary motor component (10, 14, 16, 24) and a rotatable motor component (18, 20, 22, 42) which is rotatably driven by an electromagnetic drive system (38, 40), wherein the encoder is a magnetic encoder and comprises at least one magnetic field sensor (44) arranged on the stationary motor component (10, 14, 16, 24) or a component (50) fixed relative thereto, and an annular, multi-pole magnetized sensor magnet (46) arranged in the detection range of the magnetic field sensor (44) on the rotatable motor component (18, 20, 22, 42) or on a load component (60) attached to the rotatable motor component (18, 20, 22, 42). characterized by that the sensor magnet (46) has a number of 2n magnetic poles, wherein the sector angle of one magnetic pole is α, and the sector angle β of the remaining 2n-1 magnetic poles is β = (360° - α) / (2n-1) and wherein α is not equal to β. [2] Spindle motor according to claim 1, characterized by that the sensor magnet (46) simultaneously forms the rotor magnet (38) of the electromagnetic drive system (38, 40). [3] Spindle motor according to one of claims 1 or 2, characterized by that the sensor magnet (46) is magnetized in the axial or radial direction. [4] Spindle motor according to one of claims 1 to 3, characterized by that the sensor magnet (46) is magnetized in a sector shape with alternating magnetic polarity, wherein the sector angle α of at least one circular ring sector differs from the sector angles β of the other circular ring sectors. [5] Spindle motor according to one of claims 1 to 4 characterized by that the difference angle δ between the sector angle α and the sector angle β is chosen to be δ = 48 / 2n, where further α = β + / - δ. [6] Spindle motor according to one of claims 1 to 5, characterized bythat the magnetization shape of the sensor magnet (46) is rectangular or sinusoidal. [7] Spindle motor according to one of claims 1 to 6, characterized by that the magnetic field sensor (44) is a Hall sensor, a magnetoresistive sensor (MR sensor) or a giant magnetoresistive sensor (GMR sensor). [8] Spindle motor according to one of claims 1 to 7, characterized by that the spindle motor is supported by a fluid dynamic bearing system. [9] Spindle motor according to one of claims 1 to 8, characterized by in that the rotatable motor component (18, 20, 22, 42) comprises a two-part hub (20) with an inner hub component (20a) and an outer hub component (20b), wherein the sensor magnet (46) is arranged on the outer hub component (20b). [10] Spindle motor according to one of claims 1 to 9, characterized bythat the fixed motor component (10, 14, 16, 24) has a motor base (10), and the magnetic field sensor (44) is arranged on a circuit board (48) of the spindle motor arranged on the motor base (10). [11] Spindle motor according to claim 10, characterized by that the magnetic field sensor (44) extends through an opening (52) in the motor base (10) and is positioned opposite the sensor magnet (46) attached to the hub (20). [12] Optical scanner, in particular LiDAR scanner, driven by a spindle motor according to one of claims 1 to 11. [13] Optical scanner according to claim 12, characterized by that it has a polygon mirror (60) which is fastened to the hub (20) of the spindle motor, wherein the sensor magnet (46) is fastened to the polygon mirror (60). [14] Optical scanner according to claim 12 or 13, characterized bythat the hub (20) or the outer hub component (20b) consists of a material with the same expansion coefficient as the material of the polygon mirror (60).

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