Brushless motor and method for producing brushless motor

Abstract

The invention relates to a brushless motor (10), in particular a brushless direct current motor (12), comprising a stator (14) and a rotor (18) arranged inside the stator (14) so as to be rotatable relative to the stator, the rotor (18) having a cylindrical main body (20) which is connected to a motor shaft (16) in a rotationally fixed manner and carries a plurality of permanent magnets (24) on the outer circumference (22) thereof, the stator (14) has a stator winding (32) with a plurality of single-tooth windings (28) for driving the rotor (18) by means of an electrogenerated magnetic field. According to the invention, the permanent magnets (24) of the rotor (18) are fastened by means of thin-walled stiffeners (56) which radially surround the permanent magnets, the stiffeners (56) being integrally and / or positively connected to the permanent magnets (24) by means of a plurality of solder joints (72). The invention also relates to a method for producing a brushless motor (10).

Description

Technical Field

[0001] The invention relates to a brushless motor, in particular a brushless DC motor, comprising a stator and a rotor arranged inside the stator so as to be rotatable relative to the rotor, wherein the rotor comprises a cylindrical base body which is connected to the motor shaft in a rotationally fixed manner and carries a plurality of permanent magnets on its outer circumference, wherein the stator comprises a stator winding for driving the rotor by means of an electromagnetically generated magnetic field, the stator winding comprising a plurality of single-tooth windings. The invention also relates to a method for producing a brushless motor. Background Art

[0002] A brushless motor is particularly to be understood as a motor having a three-phase winding on the stator side, which can be controlled or regulated in such a way that a rotating magnetic field is generated, which drives a permanently excited rotor. Alternatively, it is also conceivable to use the rotor in connection with a generator.

[0003] The rotor for a brushless motor, in particular a brushless direct current motor, referred to as a BLDC (brushless direct current) or EC (electronically commutated) motor, has a magnet with permanent magnet excitation, which is usually manufactured in two different embodiments. On the one hand, permanent magnets of different magnetic poles can be embedded in the so-called slots (Taschen) of the hollow cylindrical base body, and on the other hand, it is possible that the magnets or correspondingly alternatingly magnetized magnetic rings are applied to the base body from the outside as surface magnets. The base body is composed of at least a plurality of rotor layers (Rotorlaminationen) stacked into a rotor lamination stack, and the rotor layers are respectively stamped from soft magnetic sheets. However, other configurations of rotors for motors, in particular EC motors, can also be considered. The hollow cylindrical base body of the rotor can be constructed, for example, from a composite material (soft magnetic composite material-SMC). The SMC material consists of high-purity iron powder, which has a special surface coating on each individual particle. These electrically insulating surfaces ensure high resistance even after extrusion and heat treatment, which in turn minimizes or avoids eddy current losses. SMC materials are known to those skilled in the art, so that no further discussion of the composition of the SMC materials is intended here.

[0004] The permanent magnets of the magnetic ring are composed in particular of hard magnetic materials, such as iron alloys, cobalt alloys or nickel alloys. If the permanent magnets are configured as surface magnets, they can be magnetized before or after being mounted on the rotor. In addition, plastic-bonded permanent magnets (kunststoffgebundene Dauermagnete) can be considered, the magnet powder of which is embedded in a matrix formed by a plastic binder. The magnet powder can, for example, consist of hard ferrite, SmCo- and / or NdFeB or be configured as an AlNiCo alloy. Preferably, the plastic binder is configured as a thermoplastic binder, for example composed of polyamide or polyphenylene sulfide. Alternatively, it is also conceivable that the plastic binder is configured as a thermosetting binder, for example configured as an epoxy resin.

[0005] Compared to embedded magnets, surface magnets, in addition to their many advantages, also have the disadvantage of lower mechanical strength with respect to centrifugal forces, which act on the surface magnets during operation of the motor. Therefore, in order to avoid defects and malfunctions, in addition to the mechanical strength of the surface magnets, the fixing of the surface magnets on the base body is also very important.

[0006] DE 11 2016 0004 207 T5 discloses a rotor for an electric machine, which has a rotor core, a plurality of permanent magnets, a conducting element and a retaining element. The permanent magnets are formed on the outer peripheral region of the rotor core and are arranged spaced apart from each other in the circumferential direction by a pole gap. The conducting element has a conductivity which is higher than the conductivity of the permanent magnets. The conducting element surrounds the rotor core and the plurality of permanent magnets as a whole and has a first region and a second region which are opposite to each other in the circumferential direction with a gap. The retaining element finally surrounds the rotor core, the plurality of permanent magnets and the conducting element as a whole. Summary of the invention

[0007] The object of the present invention is to provide a brushless motor whose permanent magnets arranged on the outer circumference of the rotor are held by reinforcements which are improved compared to the prior art, wherein the reinforcements are also connected particularly reliably to the permanent magnets in order to avoid defects and malfunctions.

[0008] In order to achieve the stated object, it is provided that the permanent magnets of the rotor are fastened by means of a thin-walled reinforcement radially surrounding the permanent magnets, wherein the reinforcement is connected to the permanent magnets in a material-locked and / or form-locked manner via a plurality of weld points. As a result, in a particularly advantageous manner, the motor in general and the rotor in particular can be effectively and cost-effectively protected from damage even at particularly high rotational speeds of more than 20,000 rpm (rotations per minute). In addition, the thin-walled reinforcement allows a small gap between the rotor and the stator, so that the motor can be configured in such a way that the losses of the motor in terms of the effective action coefficient are minimal.

[0009] In addition, the present invention relates to a motor-driven processing tool, in particular an electric hand-held machine tool, which has a brushless motor according to the present invention. In addition, in the context of the present invention, a motor-driven processing tool should be understood as a machine tool operated by a battery and / or an electrical network, which is used to process a workpiece with an insertion tool driven by a brushless motor. Here, the electric processing tool can be configured as a hand-held machine tool or as a fixed machine tool. In this context, typical machine tools are hand-held or table drilling machines, screwdrivers, electric hammers, planers, angle grinders, vibrating sanders, polishers and the like. As electric tools, correspondingly driven gardening and construction tools such as lawn mowers, lawn trimmers, pruning saws, motor and groove milling machines, blowers, robot crushers and excavators can also be considered. In addition, the present invention can be applied to brushless motors of household appliances such as vacuum cleaners, mixers, etc.

[0010] In the extended solution, it is provided that the reinforcement is constructed as at least one hollow cylindrical sleeve, wherein the number, shape and distribution of the welds depend on the operating parameters of the brushless motor and / or the sleeve. Thus, for example, each permanent magnet can be provided with a number of 1 to 10, in particular 2 to 4 welds. Here, the number of welds depends on the size of the rotor, in particular the diameter and length of the rotor, and the size and shape of the permanent magnets. In order to avoid damage to the magnetic flux between the rotor and the stator, the number of welds should be as small as possible. On the other hand, a certain minimum number is required to reliably fasten the reinforcement or sleeve. Alternatively or in addition, in addition to optimizing the number of welds, the size or shape of the welds can also be changed so that the welds have a diameter of 0.2 to 2 mm respectively. In addition, possible imbalances of the rotor can be compensated by the number, shape and distribution of welds.

[0011] Particularly preferably, the welding point is arranged in the middle of the permanent magnet in the circumferential direction of the rotor and / or arranged near or on the pole gap between two adjacent permanent magnets. Thus, the best possible contact between the reinforcement part or sleeve and the permanent magnet can be ensured without impairing the effective action coefficient of the motor.

[0012] The at least one sleeve may be provided with a seam, which runs substantially perpendicular to the longitudinal axis of the motor shaft of the brushless DC motor. Unlike a seamless sleeve, the seam allows a simpler manufacturing process for the sleeve. Similarly, the reinforcement may consist of a plurality of sleeves, which are pushed onto the permanent magnet. Here, the individual sleeves of the reinforcement may be pushed successively from one direction along the longitudinal axis of the motor shaft onto the permanent magnet mounted on the rotor, and in particular when the number of sleeves is even, the individual sleeves are pushed in pairs from two directions along the longitudinal axis onto the permanent magnet.

[0013] In another embodiment, the reinforcement is composed of a paramagnetic metal, in particular aluminum, brass, stainless steel or the like. Alternatively, the reinforcement may also be composed of a plastic having a magnetic permeability of a maximum of 15, in particular a maximum of 2, or a composite material formed by plastic and a paramagnetic metal. Paramagnetic metals are to be understood as metals having a magnetic permeability greater than 1, which are not strongly attracted by magnets and cannot be magnetized themselves. Therefore, paramagnetic metals are significantly different from ferromagnetic metals, such as iron and diamagnetic metals, such as copper, in terms of their magnetic properties. It should be noted here that the concept "non-magnetic material" is sometimes used for paramagnetic or non-ferromagnetic materials. Strictly speaking, however, there is no non-magnetic material, because each material has a magnetic reaction under a certain intensity of magnetic field to which it is exposed. It is particularly advantageous that a reinforcement composed of a paramagnetic metal and / or a plastic with a low magnetic permeability prevents partial or complete short circuiting of the magnetic circuit of the brushless motor.

[0014] In order to simplify the sliding of the at least one sleeve onto the permanent magnets of the rotor, the sleeve has at the open end an introduction section which is widened relative to its inner diameter and whose inner diameter is larger than the outer diameter of the rotor with the mounted permanent magnets.

[0015] The invention relates to a method for producing a brushless motor, wherein a reinforcement is pushed onto a permanent magnet of a rotor along the longitudinal axis of the motor shaft and subsequently welded to the permanent magnet in a material-locked and / or form-locked manner by means of a laser, in particular a laser of an assembly device. The laser heats the focal point intensely for a short time, thereby producing a molten column, which softens or liquefies parts of the reinforcement and the permanent magnet in such a way that after the solidification of the molten column, undercuts and / or projections are produced between them, which cause a form-locked connection. In a further method step, the reinforcement is connected to the permanent magnet in a force-locked manner by means of a longitudinal extrusion connection before welding. In this case, the reinforcement is plastically and irreversibly deformed during the longitudinal extrusion connection by widening its inner diameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Please refer to the attached Figures 1 to 11 The invention is explained by way of example, wherein identical reference numerals in the figures denote identical components having the same principle of action.

[0017] The accompanying drawings show:

[0018] Figure 1 : A cross-sectional view of a three-phase brushless motor according to the prior art,

[0019] Figure 2 :Used to control the Figure 1 A block diagram of the electronic circuit of a motor constructed as a brushless DC motor,

[0020] Figure 3 : A cross-sectional view of a first embodiment of a brushless motor according to the present invention,

[0021] Figure 4 : A perspective view of a second embodiment of a rotor of a brushless motor according to the present invention,

[0022] Figure 5 :Used to fasten Figure 4 A cross section of the sleeve of the permanent magnet of the rotor according to the invention,

[0023] Figure 6 : A perspective view of a third embodiment of a rotor of a brushless motor according to the present invention,

[0024] Figure 7 : A perspective view of a first embodiment for connecting a sleeve to a permanent magnet according to the invention,

[0025] Figure 8 :according to Figure 7 A top view of an embodiment of a single solder joint,

[0026] Fig. 9 : A perspective view of a second embodiment for connecting a sleeve to a permanent magnet according to the invention,

[0027] Fig.10 : a perspective view of a third embodiment for the connection of a sleeve to a permanent magnet according to the invention, and

[0028] Fig.11 : A perspective view of a fourth embodiment for connecting a sleeve to a permanent magnet according to the present invention. DETAILED DESCRIPTION

[0029] Figure 1A cross section of a brushless motor 10 according to the prior art is shown, which is configured as a three-phase brushless direct current motor (BLDC motor or EC motor) 12, which has a stator 14 and a rotor 18 arranged in a rotationally fixed manner on a motor shaft 16. The brushless direct current motor 12 is used to drive a processing tool not shown in detail, such as a vacuum cleaner, a machine tool or the like. Instead of a BLDC motor or EC motor 12, an alternating current motor (AC motor) can also be considered, for example, configured as an asynchronous or synchronous motor. The rotor 18 of the brushless direct current motor 12 includes a cylindrical base body 20, which has a plurality of permanent magnets 24 configured as surface magnets on its outer circumference 22, which alternate their polarity N, S in the circumferential direction of the rotor 18. Four permanent magnets 24 are shown in the embodiment, which form two rotor pole pairs. However, different numbers of permanent magnets 24 can also be considered. The stator 14 has six radially inwardly directed stator teeth 26, each of which carries a single-tooth winding 28, wherein each two oppositely disposed single-tooth windings 28 form a winding line 30 of a three-phase stator winding 32. The stator 14 defines a cylindrical cavity by its stator teeth 26, in which the rotor 18 is arranged rotatably relative to the stator 14 by means of the motor shaft 16. The winding line 30 generates a rotating magnetic field when energized, which causes the permanently excited rotor 18 and the motor shaft 16 to rotate. It should be particularly pointed out that the present invention below can not only be applied to a brushless motor 10 constructed as an electric motor. The brushless motor 10 can also be constructed as a correspondingly constructed generator. Below, the present invention will be described only based on the brushless DC motor 12.

[0030] exist Figure 2 The control method for Figure 1 Device 34 for brushless DC motor 12. Device 34 includes, in addition to brushless DC motor 12, control or regulating unit 36, drive circuit 38 and comparator 40. For reasons of simplicity, only the most important components and assemblies of device 34 are shown. Control or regulating unit 36 ​​can be configured as a microprocessor (μP), a digital signal processor (DSP), an application-specific integrated circuit (ASIC) or the like. It is also conceivable that control or regulating unit 36 ​​is at least partially composed of discrete semiconductor components. Drive circuit 38 is configured as an inverter in the form of a B6 bridge circuit and has a half-bridge 42 configured as an inverter circuit for each phase or winding line 30 of the three-phase U, V, W of stator winding 32. Each half-bridge 42 is composed of a first power switch 44 and a second power switch 46, the first power switch being connected to a high supply potential V H (high side) connected, the second power switch is connected to the low supply potential V LThe power switches 44, 46 can be designed as semiconductor switches in the form of IGBTs, IGCTs, thyristors, power MOSFETs or the like, but can also be designed as relays. The control or regulation unit 36 ​​uses a pulse width modulated signal or a plurality of pulse width modulated signals S PWM (the two are used synonymously here) the individual power switches 44, 46 are controlled to energize each of the two winding lines 30, so that the first power switch 44 of one of the three half-bridges 42 is closed (for example, T1), while the first power switches 44 of the other two half-bridges 42 are open (for example, T3 and T5), and the second power switch 46 of one of the other two half-bridges 42 is closed (for example, T2), while the second power switch 46 of at least the lower half-bridge 42 is open (for example, T4), and the first power switch 44 of the half-bridge (for example, T1) is closed. In this way, in order to generate a rotating magnetic field, the first power switch 44 and the second power switch 46 can be switched alternately, so that four of the six single-tooth windings 28 of the winding line 30 are energized, so that the stator flux (Statordurchflutung) generated during operation is oriented on average perpendicular to the rotor flux (Rotordurchflutung). In addition, in order to avoid short circuits, it is ensured that the two power switches 44, 46 of the same half-bridge 42 are not closed at the same time (for example, T1 and T4). For this purpose, the power switches 44, 46 of the same half-bridge 42 are always switched on and off by means of a pulse width modulation signal S for a certain dead time after the respective other power switch 44, 46 is switched off. PWM Closed. Such circuit arrangements are known to those skilled in the art and are not discussed in detail here. Instead of multiple B6 half-bridges, an H-bridge or similar inverter circuit can also be used to control the individual phases U, V, W of the brushless DC motor 12.

[0031] In order to be able to determine the exact switching time points for the individual power switches 44, 46 for the drive circuit 38, the control or regulating unit 36 ​​must know the position of the rotor 18. For example, the rotor position can be acquired with the aid of sensors, such as Hall sensors, which are arranged on the stator 14 in the circumferential direction of the rotor 18. However, instead of acquiring the rotor position using sensors, it is often advantageous to acquire the rotor position in a sensorless manner by means of back electromotive force (Back-EMF) in combination with electrical commutation, since this usually results in less cost and higher reliability due to the elimination of sensors, and a more compact design of the brushless motor 10 is achieved. When using the back electromotive force, the course of the voltage induced by the permanent magnets 24 of the rotor 18 in the currentless winding line 28 is detected. For this purpose, according to the prior art, the line current I of one of the phases U, V, W is first predicted. U ,I V ,I WThe zero crossing (Nulldurchgang) of the pulse width modulation signal S is detected, and for the predetermined time period in which the predicted zero crossing occurs, the pulse width modulation signal S is used to generate the pulse width modulation signal S. PWM The energization of the corresponding winding line 30 is interrupted. When the line voltage U of the relevant phases U, V, W is cut off, U , U V , U W After that, the line current I U ,I V ,I W Flows through a freewheeling element (not shown) which is connected in parallel with the switched-off power switches 44, 46. In the case of a MOSFET, the freewheeling element is implemented, for example, by its own freewheeling diode. Since the freewheeling diode conducts in only one direction, once the line current I U ,I V ,I W When the value reaches zero, there is a step-like increase in voltage. Therefore, the line current I U ,I V ,I W The zero crossing of the line voltage U U , U V , U W Determine and calculate the line current I after disconnection U ,I V ,I W The position of the rotor 18 is detected by the phase difference between the electromotive force and the back electromotive force.

[0032] In accordance with Figure 2 In the exemplary embodiment shown, only phase U is used to detect the rotor position. For this purpose, the comparator 40 forms a potential V acting on a first input at a common star point 48 of the winding lines 30 of the brushless DC motor 12. SP and the potential V acting on the second input of the node 50 for energizing the corresponding winding line 30 of the phase U BF,U The arithmetic difference between Diff In order to determine the potential V of the voltage induced in the non-energized winding line 30 BF,U , using a voltage divider 54 formed by at least two resistors 52, which is connected to the node 50 on one side and to the reference potential V on the other side. GND , low supply potential V L or similar reference potential. The arithmetic difference U Diff As the digitized back EMF signal S BF,U The signal is transmitted from the comparator 40 to the control or regulating unit 36 ​​.

[0033] Figure 3The present invention is illustrated based on a section through the brushless DC motor 12 transversely to the longitudinal axis A of the motor shaft 16 . Figure 1 The base body 20 of the rotor 18, which is connected to the motor shaft 16 in a rotationally fixed manner, carries permanent magnets 24 on its outer circumference 22, which have alternating polarities N, S. The permanent magnets 24 are connected to the base body 20 in a material-locked, form-locked and / or force-locked manner on the one hand and are fastened by means of a thin-walled reinforcement 56 radially surrounding the permanent magnets on the other hand. In order to reliably fasten the permanent magnets 24 even at very high rotational speeds of more than 20.000 rpm of the brushless DC motor 12, and to keep the magnetic gap between the rotor 18 and the stator 14 as small as possible to maintain or increase efficiency, the reinforcement 56 has an elastic modulus of at least 150 GPa and / or a yield strength of at least 600 MPa. Here, due to the high elastic modulus, very small deformations can be achieved even with small wall thicknesses, while the high yield strength can avoid undesirable plastic deformations on the outer circumference 58 of the reinforcement 56.

[0034] In order to prevent partial or complete short circuit of the magnetic circuit of the brushless motor 12, the reinforcement 56 is composed of a paramagnetic metal, in particular aluminum, brass, stainless steel or the like. Alternatively, the reinforcement 56 can also be composed of a plastic having a maximum magnetic permeability μ of 15, in particular a maximum of 2. r , or a composite material formed by plastic and paramagnetic metal.

[0035] A pole gap 60 is provided between two adjacent permanent magnets 24 mounted on the base body 20 of the rotor 18. For the form-locking or force-locking fixation of the permanent magnets 24, the base body 20 of the rotor 18 has projections 62 distributed on its outer circumference 22, by means of which the permanent magnets 24, which are preferably not yet magnetized, can be positioned with defined pole gaps 60. These projections 58 can be formed, for example, as bumps, ribs or the like on the base body 20. Alternatively or in addition, the permanent magnets 24 can also be connected to the base body 20 in a material-locking manner, for example by means of adhesive bonding. The pole gaps 60 allow both optimization in terms of the power density of the brushless DC motor 12 and optimization in terms of full utilization of the magnetic material used for the permanent magnets 24. As a result, a balance between cost and efficiency of the brushless DC motor 12 can be achieved in a simple manner as required, in that the pole gap 60 is kept as small as possible on the one hand, so as not to reduce or only to a minimum the power density of the brushless DC motor 12, and on the other hand is configured so large that the magnetic material used can be fully utilized as much as possible. For this purpose, the width W of the pole gap 60 in the circumferential direction and the outer diameter D of the rotor 18 provided with the permanent magnets 24 are R (See Figure 4) is preferably less than 10%. In this context, a thin-walled reinforcement 56 is preferably understood to mean that the thickness T of the reinforcement 56 is less than its inner diameter D I 2%.

[0036] In order to manufacture the brushless DC motor 12 according to the present invention, in a first method step, a plurality of initially unmagnetized or weakly magnetized permanent magnets 24 are assembled on the outer circumference 22 of the base body 20 of the rotor 18, in particular by means of an assembly device not shown in detail, so that a pole gap 60 is retained between two adjacent permanent magnets 24. Here, the permanent magnets 24 can be fixed to the base body in a material-locked, form-locked and / or force-locked manner in the manner described above. In the following method step, the reinforcement 56 is pushed onto the permanent magnet 24 of the rotor 18 in the direction of the longitudinal axis A of the motor shaft 16. Preferably, this can also be performed automatically by the assembly device. During the pushing process, the reinforcement 56 is connected to the permanent magnet 24 by a force-locked longitudinal extrusion connection, so that the reinforcement 56 is connected to the permanent magnet 24 by its inner diameter D I The expansion (see Figure 5 ) and is plastically and irreversibly deformed. Before the rotor 18 is installed in the stator 14, the permanent magnets 56 are magnetized in a further method step by means of magnetizing coils of an assembly device.

[0037] The pole gap 60 between each two adjacent permanent magnets 24 provides the following advantages: a simple, subsequent and, most importantly, complete magnetization of the initially unmagnetized or weakly magnetized permanent magnets 24. The complete magnetization achieves a significantly increased magnetic flux, so that the permanent magnets 24 also contribute significantly to the torque generation of the brushless DC motor 12 in their edge regions. In addition, the unmagnetized or weakly magnetized permanent magnets 24 can be positioned more easily and more precisely on the outer circumference 22 of the base body 20 of the rotor 18, since no magnetic attraction forces or at least only small magnetic attraction forces are generated by them.

[0038] Figure 4 A further embodiment of a rotor 18 is shown in a perspective view. The reinforcement 56 is designed as a hollow cylindrical sleeve 64 which is connected to the permanent magnets 24 of the rotor 18 in a force-fitting manner by means of a longitudinal press connection. In this case, the sleeve 64 is formed during the longitudinal press connection by its inner diameter D I The expansion of the plastic deformation is irreversible. Figure 3 The reinforcement 56 of the rotor 18 can also be designed, for example, as a ring which extends only over a portion of the length of the base body 20 of the rotor 18, while the sleeve 64 completely surrounds the permanent magnet 24. The sleeve 64 thus extends over the entire length of the base body 20 of the rotor 18 in the direction of the longitudinal axis A of the motor shaft 16. At the open end 66, the sleeve 64 has a diameter D I Widened introduction stage 68, the inner diameter D of the introduction stage PGreater than the outer diameter D of the rotor 18 with the permanent magnets 24 mounted thereon R As a result, a simplified displacement of the sleeve 64 along the longitudinal axis A of the motor shaft 16 is possible.

[0039] To illustrate, in Figure 5 , a thin-walled sleeve 64 having a thickness T which has not yet been pushed onto the rotor 18 is shown in a section along the longitudinal axis A. It can be seen here that the inner diameter D of the introduction stage 68 at the open end 66 of the sleeve 64 P is larger than the inner diameter D of the hollow cylindrical portion of the sleeve I In order to achieve a longitudinal press connection during the displacement of the sleeve 64, the inner diameter D of the hollow cylindrical part of the sleeve is I In the undisplaced state, it must be smaller than the outer diameter D of the base body 20 of the rotor 18 provided with the permanent magnets 24 . R Therefore, in the unassembled state of the sleeve 64 the following relationship applies: D P >D R >D I Furthermore, undesired plastic deformations on the outer circumference 58 of the sleeve 64 during operation of the brushless DC motor 12 can be avoided by a correspondingly high yield strength of at least 600 MPa. This allows, on the one hand, very small magnetic gaps to be achieved between the rotor 18 and the stator 14 without the risk of mechanical contact and, on the other hand, ensures a circumferential movement of the rotor 18 even at very high rotational speeds.

[0040] Figure 6 A further embodiment of the invention is shown, in which the reinforcement 56 is formed by two sleeves 64 ′, 64 ″ which are joined together by means of a seam 70 running essentially perpendicular to the longitudinal axis A of the motor shaft 16 . Figure 4 and 5The seamless sleeve 64 and the seam 70 allow a simpler production and assembly process of the sleeves 64', 64", in particular when the base body 20 of the rotor 18 extends particularly long. In this case, the sleeves 64', 64" can be connected by material locking, in particular welded, by means of the seam 70 before being pushed onto the permanent magnet 24, so that after the connection, the sleeves have an introduction stage 68', 68" at their open ends 66', 66", respectively. Alternatively, it is also conceivable to push the individual sleeves 64', 64" of the reinforcement 56 successively from one direction along the longitudinal axis A of the motor shaft 16 onto the base 20 of the rotor 18 equipped with the permanent magnets 24, especially when the number of sleeves 64 is even, push the individual sleeves in pairs from two directions along the longitudinal axis onto the base, and then connect the sleeves by means of a seam 70. If the sleeves 64', 64" are composed of plastic or a composite material, the seam 70 connecting the sleeves can also be produced by means of laser welding or the like. Adhesive bonding of the seam 70 is also conceivable.

[0041] Figure 7 A first embodiment of a connection between a reinforcement 56 designed as a sleeve 64 and a permanent magnet 24 is shown in a three-dimensional view. For the sake of clarity, the representation of the base body 20 of the rotor 18 and the motor shaft 16 is omitted. However, it should be noted that the permanent magnets 24 (as described above) are already mounted in a manner that maintains the pole gap 60 arranged between the permanent magnets before the sleeve 64 is pushed onto the base body 20 of the rotor 18. The sleeve 64, which is composed of a paramagnetic metal in particular, is connected to the permanent magnet 24 by a plurality of weld points 72 in a material-locking and / or form-locking manner. The weld points 72 can be set automatically in a particularly advantageous manner after the sleeve 64 has been pushed onto the permanent magnet 24 by means of a corresponding welding device, in particular a laser, of the assembly device, but not shown in detail. Manual setting of the weld points 72 is also conceivable. As a result, even at very high rotational speeds of over 20,000 rpm and in the event of impacts, falls or the like, the brushless DC motor 12 can generally and its rotor 18 in particular can be effectively and cost-effectively protected against damage, for example by deformation and / or axial movement of the sleeve 64 along the longitudinal axis A of the motor shaft 16.

[0042] The number, shape and distribution of the welds can vary depending on the operating parameters of the brushless DC motor 12 and / or the sleeve 64. For example, the number of welds 72 should be as large or as small as necessary for a reliable fixation of the sleeve 64, and should also be as small or as large as necessary to avoid impairment of the magnetic field between the rotor 18 and the stator 14. Figure 7, three welding spots 72 are respectively arranged in the region of the pole gap 60 along the longitudinal axis A—two of the welding spots 72 are located near the open end 66 and the third is located substantially at half the length of the sleeve 64. In the case of a longer or shorter sleeve 64, more or fewer welding spots 72 can be provided accordingly. It is also possible to provide a plurality of welding spots 72, depending on the outer diameter D of the rotor 18. R Depending on the number of permanent magnets 24 or pole gaps 60, the welding spots 72 are not arranged near each pole gap 60, but leave each pole gap 60. However, it is advantageous that the number of welding spots 72 per permanent magnet 24 is in the range of 1 to 10, in particular 2 to 4, wherein, as mentioned, this depends decisively on the size of the rotor 18 and the number, size and shape of the permanent magnets 24.

[0043] Figure 8 A single weld spot 72 is shown in a top view. In addition to a material-locking connection by means of a laser, a form-locking connection can also be produced, so that the focal point is heated intensively for a short time, thereby producing a molten column, which softens or liquefies parts of the sleeve 64 and the permanent magnet 24. After the molten column solidifies, undercuts and / or projections are produced between the sleeve 64 and the permanent magnet 24, which cause the form-locking connection. Alternatively or additionally, in addition to optimizing the number of weld spots 72, the size or shape of the weld spots can also be varied, so that the weld spots each have a diameter D of approximately 0.2 to 2 mm. S . For a material-locked connection, the sleeve 64 and the permanent magnet 24 must consist of a corresponding weldable material. In the sleeve 64, this is ensured in particular by paramagnetic metals, but there are also plastics and composite materials suitable for welding to the permanent magnet 24. The material of the permanent magnet 24 should preferably be sintered or hot-pressed. Here, however, plastic-bonded permanent magnets 24 can also be used. The same applies to possible coatings and coverings of the sleeve 64 and the permanent magnet 24. In addition, the number, shape and distribution of the weld spots 72 can also compensate for possible imbalances of the rotor 18 to a certain extent, so that the weld spots 72 do not have to be distributed symmetrically on the outer circumference 58 of the sleeve 64.

[0044] exist Fig. 9 , a second exemplary embodiment for a material-locking and / or form-locking connection of the sleeve 64 and the permanent magnet 24 by means of a plurality of weld points 72 is shown in a perspective view. Figure 8 , two welding spots 72 are arranged on each permanent magnet 24 substantially centrally along the longitudinal axis A in the circumferential direction of the sleeve 64. Here, the welding spots 72 are located near the open end 66 of the sleeve 64. However, it is also conceivable that more welding spots can be arranged along the longitudinal axis A depending on the length of the sleeve 64. It is also conceivable that at a smaller outer diameter D of the rotor 18 R In this case, not every permanent magnet 24 is connected to the sleeve 64 in a form-fitting and / or force-fitting manner via a weld point 72 .

[0045] Fig.10 A third exemplary embodiment for connecting sleeve 64 and permanent magnet 24 by means of a plurality of weld spots 72 is shown. Four weld spots 72 are provided per permanent magnet 24 so that they are close to pole gap 60 in the edge region of permanent magnet 24 near open end 66 of sleeve 64 .

[0046] Fig.11 A fourth exemplary embodiment for connecting a sleeve 64 and a permanent magnet 24 is shown. Here, when the sleeve 64 is pushed onto one of its open ends 66, in particular onto the open end 66 opposite the open end 66 with the introduction stage 68, a ring 74 is mounted so that it is materially connected to the permanent magnet 24 at the end face and to the sleeve 64 at its circumferential edge 76 by a plurality of weld spots 72. In this case, the permanent magnet 24 can be provided with one weld spot 72. However, it is also possible to provide a plurality of weld spots 72 depending on the outer diameter D of the rotor 18. R The number of permanent magnets 24 and the number of welding spots 72 are considered to be greater or less. Preferably, the ring 74 consists of the same material as the sleeve 64. It is also possible to provide a ring 74 at each open end 66 of the sleeve 64. Instead of a ring 74, the sleeve 64 can also have a single tab at at least one of its open ends 66, which tab is bent after being pushed onto the permanent magnet 24 and welded to the permanent magnet 24 at the end.

[0047] Finally, it should be pointed out that the present invention is not limited to Figures 3 to 11 The embodiments shown in the drawings are to be understood only as examples. Therefore, the number, shape and size of the permanent magnets 24 can be varied in particular. The size of the rotor 18 and the configuration of the stator 14 of the brushless DC motor 12 shown in the drawings are also not to be understood as restrictive. The same applies to the brushless DC motor 12 and the electronic components for controlling the brushless DC motor, which must be adapted accordingly when the brushless motor 10 is designed as a generator.

Claims

1. A brushless motor (10), in particular a brushless direct current motor (12), comprising a stator (14) and a rotor (18) arranged within the stator (14) so ​​as to be rotatable relative to the stator, wherein: The rotor (18) has a cylindrical base body (20) which is connected to the motor shaft (16) in a rotationally fixed manner and carries a plurality of permanent magnets (24) on the outer circumference (22) of the base body, wherein the stator (14) has a stator winding (32) with a plurality of single-tooth windings (28) for driving the rotor (18) by means of an electromagnet, characterized in that the permanent magnets (24) of the rotor (18) are fastened by means of a thin-walled reinforcement (56) radially surrounding the permanent magnets, wherein the reinforcement (56) is connected to the permanent magnets (24) by a plurality of weld points (72) in a materially and / or form-locking manner.

2. The brushless motor (10) according to claim 1, characterized in that: The reinforcement (56) is constructed as at least one hollow cylindrical sleeve (64, 64', 64"), wherein the number, shape and distribution of the welding points (72) depend on operating parameters of the brushless motor (10) and / or the sleeve (64, 64', 64").

3. The brushless motor (10) according to any one of the preceding claims, characterized in that Each permanent magnet (24) is provided with 1 to 10, in particular 2 to 4, welding points (72).

4. The brushless motor (10) according to any one of the preceding claims, characterized in that The weld (72) has a diameter of approximately 0.2 to 2 mm.

5. The brushless motor (10) according to any one of the preceding claims, characterized in that The welding point (72) is arranged in the middle of the permanent magnet (24) in the circumferential direction of the rotor (18) and / or is arranged near or on a pole gap (60) between two adjacent permanent magnets (24).

6. The brushless motor (10) according to claims 2 to 5, characterized in that The at least one sleeve (64, 64', 64") has a seam (70) which runs essentially perpendicular to the longitudinal axis (A) of the motor shaft (16).

7. A brushless motor (10) according to any one of the preceding claims, characterized in that The reinforcement (56) is composed of a paramagnetic metal, such as aluminum, brass, stainless steel or the like.

8. The brushless motor (10) according to any one of claims 1 to 6, characterized in that: The reinforcement (56) consists of a plastic having a magnetic permeability (μm) of at most 15, in particular at most 2. r ), or a composite material consisting of plastic and paramagnetic metal, in particular aluminum, brass, stainless steel or the like.

9. The brushless motor (10) according to any one of claims 2 to 8, characterized in that: The at least one sleeve (64, 64', 64") has, at the open end (66), an inner diameter (D) of the sleeve (64, 64', 64") I ) widened introduction stage (68), the inner diameter (D P ) is greater than the outer diameter (D R ).

10. An electrically powered machining tool, in particular an electric handheld power tool, having a brushless electric motor (10) according to any one of the preceding claims.

11. A method for producing a brushless motor (10) according to any one of claims 1 to 9, characterized in that: The reinforcement (56) is pushed onto the permanent magnet (24) of the rotor (18) in the direction of the longitudinal axis (A) of the motor shaft (16) and is subsequently welded to the permanent magnet (24) in a material-locking and / or form-locking manner by means of a welding device, in particular a laser of an assembly device.

12. The method according to claim 11, characterized in that The welding device is used to heat the focal point intensively for a short time, thereby generating a melt column which softens or liquefies parts of the reinforcement (56) and the permanent magnet (24), so that after the melt column solidifies, undercuts and / or projections are generated between the reinforcement and the permanent magnet, which cause a positive fit.

13. The method according to any one of claims 11 or 12, characterized in that The reinforcement (56) is connected to the permanent magnet (24) in a non-positive manner by means of a longitudinal press connection before welding.

14. The method according to claim 13, characterized in that The reinforcement (56) is formed during the longitudinal extrusion connection by the inner diameter (D I ) widens and deforms irreversibly due to plastic deformation.

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