Brushless electric machine, and machining device driven by electric motor

Abstract

In a brushless electric machine (10), in particular a brushless DC motor, having a stator (14) and a rotor (18) arranged inside the stator (14) in a manner able to move in rotation relative thereto, the rotor (18) having a cylindrical main body (20) that is connected to a machine shaft (16) for conjoint rotation and carries a plurality of permanent magnets (24n) on its outer circumference (22), the plurality of permanent magnets (24n) of the rotor (18) being fixed by way of at least one sleeve (40) that radially surrounds them, the at least one permanent magnet (24) of the plurality of permanent magnets (24n) has a first circular-section-shaped side (24i) that faces the main body (20) and that has a first radius, and a second circular-section-shaped side (24a) that is remote from the main body (20), spaced from the first circular-section-shaped side (24i) and has a second radius, the first radius being equal to the second radius.

Description

[0001] R.410008

[0002] - 1 -

[0003] Description

[0004] title

[0005] Brushless electric machine and electrically driven processing device

[0006] State of the art

[0007] The present invention relates to a brushless electric machine, in particular a brushless DC motor, with a stator and a rotor arranged rotatably within the stator relative thereto, wherein the rotor has a cylindrical base body which is non-rotatably connected to a machine shaft and carries a plurality of permanent magnets on its outer circumference, wherein the plurality of permanent magnets of the rotor is fixed by means of at least one sleeve radially surrounding them.

[0008] A brushless electric machine is understood to be, in particular, an electric machine with a stator-side three-phase winding that can be controlled or regulated in such a way as to generate a rotating magnetic field which interacts with a permanent magnet rotor. Alternatively, it is also conceivable to use the rotor in conjunction with a generator.

[0009] Rotors for brushless electric machines, especially brushless direct current (BLDC) or electronically commutated (EC) machines, with permanent magnets are generally manufactured in two different designs. Firstly, the permanent magnets of different polarities can be embedded in so-called pockets within a cylindrical base body. Secondly, the magnets, or a correspondingly alternately polarized magnetic ring, can be applied externally to the base body as surface magnets. (R.410008)

[0010] - 2 -

[0011] The rotor body typically consists of numerous rotor laminations stacked to form a rotor lamination stack, each lamination being stamped from a soft magnetic sheet. However, other rotor designs for electric machines, particularly for EC machines, are also conceivable. For example, the cylindrical rotor body can be constructed from composite materials (Soft Magnetic Composites - SMC). SMC materials consist of high-purity iron powder with a special surface coating on each individual particle. This electrically insulating surface ensures high electrical resistance even after pressing and heat treatment, which in turn minimizes or eliminates eddy current losses. SMC materials are well-known to those skilled in the art, so their composition will not be discussed further here.

[0012] The permanent magnets of the magnetic ring consist in particular of a hard magnetic material, for example, an iron, cobalt, or nickel alloy. If the permanent magnets are designed as surface magnets, they can be magnetized either before or after mounting on the rotor. Alternatively, polymer-bonded permanent magnets are conceivable, the magnetic powder of which is embedded in a matrix of polymer binder. The magnetic powder can consist, for example, of hard ferrite, SmCo, and / or NdFeB, or be designed as an AINiCo alloy. Preferably, the polymer binder is designed as a thermoplastic binder, for example, of polyamide or polyphenylene sulfide. Alternatively, it is also conceivable that the polymer binder is designed as a thermosetting binder, for example, an epoxy resin.

[0013] Surface magnets, despite their numerous advantages over buried magnets, have the disadvantage of lower mechanical strength against centrifugal forces acting on them during the operation of the electric motor. To prevent defects and failures, the mounting of the surface magnets to the base body is therefore just as important as their mechanical strength. R.410008

[0014] - 3 -

[0015] From DE 102023205332 A1, a brushless electric machine is known, in particular a brushless DC motor, comprising a stator and a rotor arranged within the stator so as to be rotatable relative to it. The rotor has a cylindrical base body which is non-rotatably connected to a machine shaft and carries a plurality of permanent magnets on its outer circumference. The stator has a stator winding with a plurality of single-tooth windings for driving the rotor by means of an electrically generated rotating magnetic field. The permanent magnets of the rotor are fixed by means of a thin-walled reinforcement radially surrounding them, the reinforcement having a modulus of elasticity of at least 150 GPa and / or a yield strength of at least 600 MPa.

[0016] Disclosure of the invention

[0017] The present invention relates to a brushless electric machine, in particular a brushless DC motor, with a stator and a rotor arranged within the stator so as to rotate relative to it, wherein the rotor has a cylindrical base body which is non-rotatably connected to a machine shaft and which carries a plurality of permanent magnets on its outer circumference, wherein the plurality of permanent magnets of the rotor is fixed by means of at least one sleeve radially surrounding it. At least one permanent magnet of the plurality of permanent magnets has a first circular segment-shaped side facing the base body with a first radius and a second circular segment-shaped side facing away from the base body and spaced apart from the first circular segment-shaped side, wherein the first radius is equal to the second radius.

[0018] Therefore, the permanent magnets advantageously comprise partial cylindrical surfaces with the same radii. This allows the permanent magnets to be stacked directly on top of each other, i.e., without a gap.

[0019] In one variant, at least one of the multiple permanent magnets has side surfaces oriented transversely to the circumferential direction of the rotor, which are plane-parallel to each other. R.410008

[0020] - 4 -

[0021] This means that the permanent magnets can be arranged directly next to each other, i.e., without a gap.

[0022] Preferably, the base body of the rotor is rotationally symmetrical and its outer circumference has at least one partial area that is identical in shape to the first circular segment-shaped side.

[0023] This allows for a positive-locking connection between the rotor's base body and the permanent magnets.

[0024] In one variant, the majority of permanent magnets have at least two permanent magnets arranged adjacent to each other in the radial direction of the rotor.

[0025] This allows for the storage of multiple permanent magnets in the radial direction of the rotor.

[0026] Preferably, the majority of permanent magnets have sintered magnet segments.

[0027] This means that permanent magnets can be manufactured without waste and without material loss.

[0028] In one variant, at least one sleeve is force-fitted to the majority of permanent magnets.

[0029] In this process, at least one sleeve surrounds the majority of the rotor's permanent magnets and securely and reliably fixes them against the centrifugal forces acting during operation.

[0030] Preferably, the at least one sleeve is attached to the majority of permanent magnets via a longitudinal press fit. R.410008

[0031] - 5 -

[0032] This allows at least one sleeve to be attached to the rotor in a stable and robust manner.

[0033] In one variant, at least one sleeve is connected to the permanent magnets in a form-fit and / or force-fit manner.

[0034] This allows for a secure and reliable fixing of the permanent magnets to the rotor.

[0035] Preferably, the at least one sleeve is made of brass, stainless steel, aluminum and / or plastic.

[0036] Thus, the permeability number for the sleeve can be kept small, so that the losses of magnetic flux in the gap between the rotor and stator remain small.

[0037] Preferably, the majority of permanent magnets are stacked on top of each other parallel to a rotational axis of the rotor.

[0038] This means the permanent magnets can be mounted together without any gap.

[0039] Preferably, the majority of permanent magnets are attached to the rotor without any auxiliary materials. In the context of the invention, an auxiliary material-free attachment is understood to mean an attachment in which the use of auxiliary materials, such as adhesives, potting compounds, resins, or plastic overmolding, is omitted.

[0040] Therefore, when attaching the majority of permanent magnets to the rotor, the use of auxiliary materials can be advantageously avoided.

[0041] Furthermore, the present invention relates to an electrically driven processing device, in particular an electric hand-held power tool, with a brushless electric motor designed as described above. AlsR.410008

[0042] - 6 -

[0043] In the context of the invention, an electrically driven machining device is understood to include, among other things, battery-powered and / or mains-powered machine tools for machining workpieces using an insert tool driven by a brushless electric motor. The electrically driven machining device can be designed as either a handheld or stationary machine tool. Typical machine tools in this context are hand-held or bench drills, screwdrivers, impact drills, planers, angle grinders, orbital sanders, polishing machines, and the like. However, appropriately powered garden and construction equipment, such as lawnmowers, string trimmers, pruning saws, rotary tillers and trenchers, blowers, robotic breakers and excavators, and the like, are also suitable machining devices. Furthermore, the invention is applicable to brushless electric motors in household appliances such as vacuum cleaners, blenders, etc.

[0044] Brief description of the drawings

[0045] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show:

[0046] Fig. 1 shows a schematic cross-sectional view of a brushless electric machine with a rotor,

[0047] Fig. 2 is a schematic cross-sectional view of a permanent magnet from Fig. 1.

[0048] Fig. 3 shows a schematic cross-sectional view of several permanent magnets stacked on top of or next to each other, and

[0049] Fig. 4 is a perspective view of the rotor from Fig. 1.

[0050] Description of the exemplary implementations

[0051] In the figures, elements with the same or comparable function are given identical reference symbols and described in detail only once.

[0052] Fig. 1 shows a brushless electric machine 10, which is designed as an example as a brushless DC motor and has a stator 14 and an R.410008

[0053] - 7 -

[0054] The stator 14 has a rotor 18 arranged to rotate relative to it. The brushless DC motor 10 serves to drive an electrically driven processing device (not shown in detail), such as a vacuum cleaner, a machine tool, or the like. Instead of a BLDC or EC motor 10, an AC motor, for example in the form of an asynchronous or synchronous motor, can also be used.

[0055] The rotor 18 of the brushless DC motor 10 has a cylindrical base body 20 which is non-rotatably connected to a machine shaft 16 and carries a plurality of permanent magnets 24n on its outer circumference 22. For example, the plurality of permanent magnets 24n can have sintered magnet segments.

[0056] The majority of permanent magnets 24n of the rotor 18 are fixed by means of at least one sleeve 40 radially surrounding them. Preferably, the majority of permanent magnets 24n are attached to the cylindrical base body 20, and thus to the rotor 18, without the use of any auxiliary materials. In the context of the invention, "auxiliary material-free attachment" means an attachment in which the use of auxiliary materials, such as adhesives, potting compounds, resins, or plastic overmolding, is omitted, which can also be referred to as "glueless assembly." In other words, the fixing and fastening of the majority of permanent magnets 24n to the rotor 18 is thus achieved without adhesives.

[0057] Preferably, the plurality of permanent magnets 24n are connected to the sleeve 40 by a force-fit and / or form-fit connection. In one embodiment, the plurality of permanent magnets 24n can comprise at least two permanent magnets 24 arranged adjacent to each other in the radial direction of the rotor 18.

[0058] At least one permanent magnet 24 of the plurality of permanent magnets 24n has a first circular segment-shaped side 24i facing the base body 20 with a first radius (Ri in Fig. 2), and a second circular segment-shaped side 24a facing away from the base body 20 and spaced apart from the first circular segment-shaped side 24i with a second radius (Ra in Fig. 2)R.410008

[0059] - 8 -

[0060] The first radius (Ri in Fig. 2) is equal to the second radius (Ra in Fig. 2). For illustrative purposes, the majority of permanent magnets 24n have longitudinal axes 25 that are aligned parallel to each other and parallel to a rotor longitudinal axis or to the rotation axis 17.

[0061] In other words, the majority of permanent magnets 24n have, for example, inner and outer partial cylindrical surfaces with the same radius. Here, the first circular segment-shaped side 24i forms an inner partial cylindrical surface, and the second circular segment-shaped side 24a forms an outer partial cylindrical surface. Therefore, the majority of permanent magnets 24n can be stacked directly on top of each other, i.e., without a gap, as shown in Fig. 3.

[0062] Preferably, the base body 20 of the rotor 18 is rotationally symmetrical with an outer circumference 22. This outer circumference 22 of the base body 20 preferably has partial areas 23, each of which is identical in shape to the inner partial cylindrical surface 24i facing the base body 20.

[0063] Fig. 2 shows the permanent magnet 24 of the plurality of permanent magnets 24n from Fig. 1, with the first circular segment-shaped side 24i, which for illustrative purposes forms the inner partial cylindrical surface with a first radius Ri, and with the second circular segment-shaped side 24a, which for illustrative purposes forms the outer partial cylindrical surface with a second radius Ra, wherein the first radius Ri is equal to the second radius Ra. For the sake of simplicity and clarity, the first radius Ri will subsequently also be referred to as "the inner radius Ri" and the second radius Ra will subsequently also be referred to as "the outer radius Ra".

[0064] For illustrative purposes, a first circular center Ci is assigned to the inner radius Ri, and a second circular center Ca is assigned to the outer radius Ra. The first circular center Ci and the second circular center Ca are not congruent, but rather spaced apart from each other in the radial direction of the rotor 18 of Fig. 1, starting from its axis of rotation 17. R.410008

[0065] - 9 -

[0066] Fig. 3 illustrates four permanent magnets from the majority of permanent magnets 24n in Fig. 1, of which only two permanent magnets are separately labelled with reference numerals 24u and 24v. In contrast to Fig. 1, here two permanent magnets are arranged stacked on top of each other for illustrative purposes. The permanent magnets 24u and 24v are arranged stacked on top of each other for illustrative purposes.

[0067] The permanent magnets shown have plane-parallel side surfaces 26. Therefore, they can be stacked next to each other without a gap.

[0068] Fig. 4 shows the rotor 18 with the plurality of permanent magnets 24n from Fig.

[0069] Figure 1 illustrates the at least one sleeve 40 radially surrounding it, which fixes the majority of permanent magnets 24n to the rotor 18. As described in Figure 1, the base body 20 of the rotor 18 has the partial areas 23, each of which is identical in shape to the inner partial cylindrical surface (24i in Figure 1).

[0070] The at least one sleeve 40 can be attached to the plurality of permanent magnets 24n via a longitudinal press fit. Preferably, the at least one sleeve 40 comprises brass, stainless steel, aluminum and / or plastic.

Claims

R.410008 - 10 - Claims 1.Brushless electric machine (10), in particular a brushless DC motor, with a stator (14) and a rotor (18) arranged rotatably within the stator (14) relative thereto, wherein the rotor (18) has a cylindrical base body (20) which is non-rotatably connected to a machine shaft (16) and carries a plurality of permanent magnets (24n) on its outer circumference (22), wherein the plurality of permanent magnets (24n) of the rotor (18) is fixed by means of at least one sleeve (40) radially surrounding them, characterized in that at least one permanent magnet (24) of the plurality of permanent magnets (24n) has a first circular segment-shaped side (24i) facing the base body (20) with a first radius (Ri) and a second circular segment-shaped side (24a) facing away from the base body (20) and spaced apart from the first circular segment-shaped side (24i) with a second radius (Ra). exhibits, where the first radius (Ri) is equal to the second radius (Ra).

2. Brushless electric machine according to claim 1, wherein the at least one permanent magnet (24) of the plurality of permanent magnets (24n) has side surfaces (26) oriented transversely to the circumferential direction of the rotor (18) which are plane-parallel to each other.

3. Brushless electric machine according to claim 1 or 2, wherein the base body (20) is rotationally symmetrical and its outer circumference (22) has at least one partial area (23) which is identical in shape to the first circular segment-shaped side (24i).

4. Brushless electric motor according to one of the preceding claims, wherein the plurality of permanent magnets (24n) are at least two inR.410008 - 11 - has permanent magnets (24u, 24v) arranged adjacent to each other in the radial direction (29) of the rotor (18).

5. Brushless electric machine according to one of the preceding claims, wherein the plurality of permanent magnets (24n) comprise sintered magnet segments.

6. Brushless electric machine according to one of the preceding claims, wherein the at least one sleeve (40) is force-fit connected to the plurality of permanent magnets (24n).

7. Brushless electric machine according to claim 6, wherein the at least one sleeve (40) is attached to the plurality of permanent magnets (24n) via a longitudinal press fit.

8. Brushless electric machine according to one of the preceding claims, wherein the at least one sleeve (40) is positively and / or force-fit connected to the permanent magnets (24).

9. Brushless electric motor according to one of the preceding claims, wherein the at least one sleeve (40) comprises brass, stainless steel, aluminium and / or plastic.

10. Brushless electric machine according to one of the preceding claims, wherein the plurality of permanent magnets (24n) are stacked on top of each other parallel to a rotation axis (17) of the rotor (18).

11. Brushless electric machine according to one of the preceding claims, wherein the plurality of permanent magnets (24n) are attached to the rotor (18) without auxiliary material.

12. Electrically driven processing device, in particular electric hand tool, with a brushless electric motor (10) according to claim 1.

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