Rotor assembly of a DC motor

Abstract

Rotor assembly of a brushless DC motor with a magnet carrier (43) and with a ring magnet (45), wherein the ring magnet (45) has a central, non-circular cylindrical recess (63) and wherein the magnet carrier (43) carries the ring magnet (45) and has a first connecting element (65) and a second connecting element (67) which are designed such that the first connecting element (65) produces a positive connection and the second connecting element (67) produces a non-positive connection to the recess (63) of the ring magnet (45), characterized in that the second connecting element (67) has bending elements (77a, 77b) which deform when the magnet carrier (43) is introduced into the recess (63).

Description

[0001] The invention relates to a rotor assembly of a DC motor, in particular a brushless DC motor.

[0002] A preferred field of application of the invention is actuators with small motors, which require a compact design and low weight, in particular small-sized brushless DC motors, which are used in the automotive sector, e.g. as small motor actuators, fan and radiator motors, drives for flap actuators, for example in air conditioning systems and in engine cooling, etc., whereby the invention is not limited to these.

[0003] US Pat. No. 7,573,169 B2 describes a permanent magnet rotor with a shaft and a ring magnet, with an elastic connecting medium inserted between the shaft and the ring magnet. The shaft is designed such that spaces are formed between the shaft and the inner surface of the magnet ring, which accommodate the elastic material. The elastic medium is preferably an adhesive that creates a firm connection between the shaft and the ring magnet.

[0004] JP H09 - 102 407 A discloses a rotor assembly in which a ring-shaped, cast plastic magnet with a reinforcing material made of carbon or glass fiber is pressed onto a shaft. The reinforcing fibers are intended to prevent the ring magnet from cracking during the pressing process.

[0005] JP 2007 - 330 030 A describes a structure for attaching a ring magnet to a rotor shaft, which is inserted between the ring magnet and the shaft. A positive connection is created by indentations on the inner surface of the ring magnet and corresponding protrusions on the outer surface of the attachment structure.

[0006] JP S64 - 8 849 A describes a rotor assembly in which a circular cylindrical rotor magnet is glued to the outer circumference of a shaft.

[0007] DE 10 2008 022 999 A1 describes a device for holding rotor magnets of a DC motor, comprising a substantially annular laminated core in which holding pockets are formed for inserting the magnets. The magnets are glued into the pockets.

[0008] EP 1 322 023 A1 describes a permanent magnet rotor with a thin-walled permanent magnet ring mounted on a plastic support member into which a rotating plain bearing is integrated. The permanent magnet ring is injected into the plastic support member during production.

[0009] DE 101 52 151 A1 describes a permanent magnet rotor for an electric motor, consisting of a permanent magnet ring held by a plastic support member, and a plain bearing. The permanent magnet ring consists of a pressed, plastic-bonded rare earth magnet. The plain bearing is a rotating member made of a sintered material. The plastic support member can be manufactured in an injection mold, has a cylindrical receptacle for a rotating plain bearing, and is integral with a pinion. The plastic support member at least partially axially and radially encloses the permanent magnet ring. The permanent magnet ring can be injected as an insert.

[0010] DE 103 02 164 A1 relates to an electrical machine comprising a rotor, a stator and a permanent magnetic element which is fastened to the rotor or to the stator, wherein the permanent magnetic element delimits an air gap between the rotor and the stator, wherein the lateral surface of the permanent magnetic element directed towards the air gap has a cylindrical shape so that the air gap has a constant width and wherein the permanent magnetic element has a non-cylindrical lateral surface on the side facing away from the air gap so that the permanent magnetic element has a different thickness in the circumferential direction.

[0011] US 2002 / 0 125 780 A1 discloses a magnetic rotor in which the outer shape of the back yoke is polygonally formed from an electromagnetic steel plate or by laminating ordinary thin magnetic plates, and a permanent magnet is fixed to a mating surface of the back yoke.

[0012] It is therefore known from the prior art to overmold a permanent magnet of a rotor assembly onto a magnet carrier and / or a shaft, or to insert the permanent magnet into an injection mold and bond it to the magnet carrier during production. It is also known to connect the permanent magnet to a shaft using additional components such as adhesives, mounts, clips, housings, inserts, and the like.

[0013] The direct connection of magnet and shaft in the injection molding process creates a good, usually stress-free coupling of magnet and shaft, but requires specially adapted injection molding tools, so that such manufacturing processes are only profitable for very high unit quantities, for example one million or more.

[0014] The construction of a rotor arrangement with a magnetic holder, for example in the form of pockets into which several individual magnets are inserted, is comparatively inexpensive and uncritical with regard to manufacturing tolerances, but requires a high level of effort during assembly and for fastening the individual magnets in the holder.

[0015] When using prefabricated ring magnets, the current state of the art presents the problem of compensating for manufacturing and positioning tolerances and of securing the permanent magnet to the magnet carrier. For this purpose, clips and adhesives are commonly used, or the magnet is pressed onto a shaft. This can lead to stresses in the magnet or loose play in the magnet's fit on the magnet carrier.

[0016] It is therefore an object of the invention to provide a rotor assembly for a DC motor which is simple and cost-effective to manufacture and at the same time achieves a reliable and stress-free mounting of the magnet.

[0017] This object is achieved by a rotor assembly having the features of claim 1. Preferred embodiments of the invention are specified in the dependent claims.

[0018] The invention provides a rotor assembly of a brushless DC motor, comprising a magnet carrier and a ring magnet, wherein the ring magnet has a central, non-circular cylindrical recess, and wherein the magnet carrier carries the ring magnet and has a first and a second connecting element, which are designed such that the first connecting element establishes a non-positive connection to the recess of the ring magnet, and the second connecting element establishes a positive connection. Preferably, the magnet carrier is made of plastic and is formed integrally with the shaft. The first and second connecting elements are molded onto the magnet carrier. Particularly preferably, the magnet carrier, which comprises the shaft, the first and second connecting elements, is produced as an injection-molded part.

[0019] The invention thus creates a rotor assembly consisting of only two parts, whereby the magnet carrier, including the shaft and connecting elements, can be manufactured as a cost-effective injection-molded part, and a simple, prefabricated permanent magnet ring serves as the permanent magnet. The two connecting elements for creating a positive and frictional connection between the magnet carrier and the permanent magnet complement each other, so that they not only securely fix the ring magnet to the magnet carrier but also compensate for manufacturing tolerances and radial play.

[0020] The non-circular cylindrical recess serves the purpose of allowing a simple positive connection between the magnet carrier and the ring magnet. In an advantageous embodiment, the base of the ring magnet's recess is designed in the shape of a regular polygon, for example, a square, hexagon, or octagon. Other base shapes, such as ellipses or even a circle or any other shape with a wavy or serrated edge, are possible. As a rule, the recess should run concentrically and parallel to the axis of the ring magnet. However, it is also conceivable for the recess to extend through the ring magnet at an angle to its axis.

[0021] The first connecting element, which establishes a positive connection to the recess, can be designed to at least partially establish linear contact with the inner surface of the recess. For example, it can have webs extending in the longitudinal direction of the magnet carrier, which protrude from the outer circumference of the magnet carrier and establish linear contact with the inner surface of the recess.

[0022] The second connecting element, which serves to provide a force-locking connection, preferably has bending elements that deform when the magnet carrier is inserted into the recess. These bending elements can, for example, be deformable wings that protrude from the outer circumference of the magnet carrier.

[0023] Additionally, the outer contour of the magnet carrier can be partially adapted to the inner contour of the recess, meaning the two can have partial, but not complete, surface contact with each other. For example, the webs of the first connecting element can be dimensioned such that they rest in corresponding edges or recesses in the inner surface of the recess.

[0024] In the preferred embodiment of the invention, the magnet carrier has two first connecting elements and two second connecting elements.

[0025] The magnet carrier can further comprise extensions, formed, for example, by the first connecting elements, which extend axially beyond the length of the ring magnet when the ring magnet is placed on the magnet carrier. The ring magnet can be fixed to the magnet carrier by hot-staking the extensions. The invention is, of course, not limited to this type of axial fixation of the magnet carrier to the ring magnet.

[0026] One end of the magnet carrier can also be extended beyond the axial length of the ring magnet, forming a shaft stub. A gear can be molded onto this shaft stub.

[0027] In a preferred embodiment of the invention, the shaft is a hollow shaft.

[0028] If the recess is formed in the shape of a regular polygon, the ring magnet is preferably magnetized such that the transitions between the south and north poles of the ring magnet are each located at the edges of the regular polygon.

[0029] In one application example, the rotor assembly according to the invention is part of an actuator for a flap actuator in a motor vehicle, which has a brushless DC motor whose outer circumference is less than or equal to 60 mm, preferably less than or equal to 30 mm. The stator of the DC motor can preferably have a diameter between 12 and 50 mm, particularly preferably approximately 24 mm. Accordingly, the rotor of the DC motor can have a diameter between 8 and 30 mm, preferably approximately 12 mm.

[0030] The invention is explained in more detail below using preferred embodiments with reference to the drawings. The figures show: Fig. 1 is an exploded view of an actuator assembly in which the rotor assembly according to an embodiment of the present invention is used, Fig. 2a and Fig. 2b is a bottom view and a perspective view of a housing with an inserted stator which can accommodate a rotor assembly according to the invention, Fig. 3a to 3c show a longitudinal section through a rotor assembly as well as a perspective view and a front view of the rotor assembly according to an embodiment of the invention, Fig. 4a to 4c show a longitudinal section through a rotor assembly as well as a perspective view and an end view of the rotor assembly according to a further embodiment of the invention; Fig. 5a to 5c show a longitudinal section through a rotor assembly as well as a perspective view and a front view of the rotor assembly according to a modification of the rotor assembly shown in the Fig. 4a to 4c shown embodiment of the invention, Fig. 6 an exploded view of a gearbox of the assembly shown in Fig. 1 is shown, and Fig. 7 a view from below of the assembly of the Fig. 6.

[0031] Fig. 1 shows an actuator assembly in which the rotor assembly according to an embodiment of the present invention is used, in an exploded view. The assembly 1 comprises a DC motor with a stator 3 and a rotor 5, a circuit board 7 for controlling the DC motor, and a gearbox 9 driven by the DC motor. The gearbox 9 comprises several gear wheels 53, 53', 53'', 53''' assigned to successive gear stages. The DC motor, the circuit board 7, and the gearbox 9 are arranged in a housing 11 that can be closed with a cover 11'. The cover 11' can additionally have a seal to protect the interior of the assembly 1 from contamination and other external influences.

[0032] The DC motor is housed in the housing 11 in a pot 13 that is molded onto an inner side of the housing 11. The pot 13 has an inner diameter that largely corresponds to the outer diameter of the stator 3, so that the pot 13 tightly encloses the stator 3. Pins 15 for positioning and fixing the DC motor are molded onto the pot 13. The stator 3 is provided with a slot insulation 17 that has a flange 19 on one end face, on which eyelets 21 are molded that protrude radially from the outer circumference of the slot insulation 17. The pins 15 are guided through the eyelets 21 in order to position the stator 3 in the pot 13 relative to the housing 11 and to fix it to the housing 11. For this purpose, the pins 15 are formed on the edge of the pot 13 in such a way that the pot edge forms a support surface for the flange 19 and the eyelets 21 of the slot insulation 17 and the pins 15 are guided through the eyelets 21.This secures the stator 3 against radial displacement and rotation. The pins 15 guided through the eyelets 21 can be hot-stitched, for example, so that the stator 3 can also be secured against axial displacement.

[0033] To attach the DC motor to the housing 11, neither an additional motor housing is required, nor do any parts of the DC motor need to be specially shaped to enable a positive-locking mounting of the stator 3 in the housing 11. Rather, the stator 3 is positioned directly relative to the housing 11 by the pot 13 and the integrally formed pins 15 and fixed to the housing 11. This significantly simplifies the installation of the DC motor in the housing 11.

[0034] The mounting of the stator 3 can be further optimized by providing a longitudinal groove 27 in a return ring 25 of the stator 3, in which groove a corresponding projection (not shown) in the inner wall of the pot 13 can be guided. Furthermore, on a bottom-side end face of the slot insulation 17 opposite the pot bottom, in the area of ​​the stator slots, evenly spaced recesses 29 are formed, into which correspondingly shaped projections (not shown) in the bottom of the pot 13 can engage. Both the recesses 29 and the longitudinal groove 27, in addition to the eyelets 21 of the slot insulation 17, thus secure the stator 3 against twisting in the pot 13.

[0035] To simplify the assembly and adjustment of the stator 3 and thus of the DC motor in the pot 13, a bearing seat 31 for a shaft or an axle of the gear 9 is also formed on the side wall of the pot 13. Accordingly, the flange 19 of the slot insulation 17 has a recess 33, which at least partially encloses the bearing seat 31 when the stator 3 is inserted in the pot 13. This ensures that the stator 3 inserted in the pot 13 always assumes a predetermined orientation. Furthermore, the bearing seat 31 additionally secures the stator 3 against twisting via the slot insulation 17.

[0036] The DC motor is additionally secured by the circuit board 7, which rests on the end face of the slot insulation 17 and thus secures the stator 3 in the axial direction. The circuit board 7 is attached to the housing 11 via webs 37, which form a support surface for the circuit board 7, with pins of the webs 37 engaging in corresponding openings 39 in the circuit board. The ends of the pins are preferably hot-stitched to achieve permanent fixation of the circuit board 7. However, the assembly is not limited in this respect. Thus, instead of hot-stitched pins, other positive and / or non-positive connections, such as snap connections and press pins, can be used. The slot insulation 17 has a row of L-shaped projections 35 on its end face facing the circuit board 7, which form wire guides for the coil wires.

[0037] The electrical contact between the circuit board 7 and the stator 3 is established via connecting pins 41, which are pressed into the projections 35 of the slot insulation 17 and extend axially from the end face of the slot insulation 17. The connecting pins 41 are guided through corresponding openings in the circuit board 7 and soldered therein. The connecting pins 41 are in turn connected to the respective coils of the stator 3 to establish electrical contact between the circuit board 7 and the coils of the stator 3.

[0038] In addition to a processing unit, the circuit board 7 can comprise several sensors that determine the rotational position of the rotor 5. For example, at least one Hall sensor can be arranged on the circuit board 7 for directly detecting the axial stray field of the rotor 5. The circuit board 7 can also have an interface for communication and / or power supply, for example, a connection to any data bus or a specialized field bus, such as the LIN bus.

[0039] The rotor 5 according to the invention, i.e. the rotor assembly, comprises a magnet carrier 43 on which an annular permanent magnet or ring magnet 45 is arranged. The magnet carrier 43 is formed in one piece with a shaft 47 which is guided through an opening 49 in the circuit board 7. The shaft 47 has a gear 47' which drives the downstream gear 9. Both the shaft 47 and the gears 53, 53', 53'' are mounted on axles 55a and 55b, 55c and 55d, respectively, with the axle 55a being arranged in the pot 13 and the axle 55b being arranged in the bearing seat 31 in the side wall of the pot 13. Furthermore, the shaft of the gear 53''' is mounted directly in a bearing in the housing 11.

[0040] The embodiment of the assembly 1 shown enables material-saving production due to the one-piece construction of the housing 11 and rapid assembly of the DC motor in the housing 11 due to the pot 13 and the molded pins 15.

[0041] The illustrated assembly 1 can be used as an actuator, wherein the rotational speed of the rotor 5 can be, for example, up to 4,000 rpm and preferably in the range of 500 to 2,500 rpm in order to generate an output speed of, for example, 3 to 10 rpm and a torque of, for example, 1 to 2 Nm. One field of application of the invention is in the automotive sector for controlling flap actuators, e.g., in air conditioning systems, or for engine control, although the present invention is not limited thereto.

[0042] The housing 11 and the stator 3 of the assembly 1 according to the Fig. 1 are further shown in a view from below and in a perspective view in Fig. 2a and 2b respectively. As shown in Fig. 2a and Fig. 2b, the stator 3 is inserted in the pot 13 of the housing 11, with the flange 19 resting on the edge of the pot 13 and the pins 15 engaging through the eyelets 21. A number of radially aligned struts 57 are formed in the bottom of the pot 13, which engage in the bottom-side recesses 29 of the slot insulation 17 in order to secure the stator 3 against twisting in the pot 13. Furthermore, in addition to the bearing seat 31, the bearing seat for the axis 55a of the shaft 47 is shown in the bottom of the pot 13. Furthermore, further bearing seats 59 for axes 55c, 55d of the downstream gearbox 9 are formed in the bottom of the housing 11, the bottom of the housing 11 being reinforced by struts 61 running radially to the respective axis 55c, 55d.

[0043] Fig. 3a and Fig. 3b show a section, an exploded view, and a front view of a rotor assembly according to an embodiment of the present invention. Corresponding components are designated by the same reference numerals as in Fig. 1. The rotor 5 has a magnet carrier 43 designed as a hollow shaft and a circular-cylindrical permanent magnet 45, in which a recess 63 is provided through which the magnet carrier 43 can be guided in order to connect the shaft 47 to the permanent magnet 45. A gear 47' is formed onto the free end of the shaft 47. Such a two-part design of the rotor 5 is more cost-effective than, for example, a one-piece production, especially for production in medium quantities, in particular less than 1 million units per year.

[0044] In the illustrated embodiment of the rotor 5, the recess 63 formed by the permanent magnet 45 is designed as a hexagonal recess. However, the recess 63 can also be another polygonal recess, or have an oval contour, or any other non-circular contour. For connection to the permanent magnet 45, the magnet carrier 43 has at least one first connecting element 65, which establishes a positive connection with the recess 63 in the permanent magnet 45, and at least one second connecting element 67, which establishes a frictional connection between the magnet carrier 43 and the permanent magnet 45.

[0045] The positive connection via the first connecting element 65 is established in particular by a linear contact mediated by a protruding rib 69 formed in the first connecting element 65 parallel to the shaft axis, which engages an edge 71 of the recess 63. The protruding rib 69 is preferably so high that a gap is created between the adjacent surfaces of the first connecting element 65 and the surfaces of the recess 63 adjacent to the edge 71, so that the adjacent surfaces do not contact one another at all or only contact one another to a small extent. In addition, the edge 71 of the recess 63 itself can be chamfered to create a distance between the surfaces of the first connecting element 65 and the recess 63. This particularly advantageous design of the first connecting element 65 reduces the risk of jamming when assembling the two components of the rotor 5 due to the slight overlap.

[0046] The first connecting element 65 is delimited at one end by a projection 73, which extends radially from the shaft 47 and forms a support surface for the permanent magnet 45 pushed onto the magnet carrier 43. The first connecting element 65 is longer than the recess 63, so that the first connecting element 65, which is fully inserted into the recess 63, protrudes slightly from the permanent magnet 45 in the axial direction and can be, for example, hot-stitched to the end face of the permanent magnet 45 in order to fasten the magnet carrier 43 to the permanent magnet 45. For this purpose, the permanent magnet 45 has a bevel 75 at the edge of the recess 63, which can accommodate the material of the first connecting element 65 displaced by the hot-stitching. Alternatively or additionally, the magnet carrier 43 can have clips or other fastening means in order to fix the magnet carrier 43 axially to the permanent magnet 45.Regardless of the type of axial fixation of the magnet carrier 43 to the permanent magnet 45, the problem of tension during assembly of the rotor can be effectively solved by the provided first and second connecting elements 65, 67.

[0047] The second connecting element 67, which creates a force connection with the permanent magnet 45, can be designed as a bending or locking element. As shown in Fig. 3b and Fig. 3c, the second connecting element 67 comprises two adjacent wings 77a and 77b and a web running parallel to the shaft axis and projecting radially, which connects the wings 77a and 77b in the manner of a Y-profile. Thus, when the magnet carrier 43 is inserted into the permanent magnet 45, the wings 77a and 77b exert a pressure on the adjacent surfaces of the recess 63 at their exposed longitudinal ends, which pressure is sufficient to hold the magnet carrier 43 in the permanent magnet 45, but sufficiently small that the magnet carrier 43 can be pushed into the permanent magnet 45 by hand. The wings 77a and 77b can be dimensioned such that the exposed longitudinal ends engage the edges 71 of the recess 63 or corresponding bevels of the edges 71 and thus exert pressure on the permanent magnet 45.

[0048] The second connecting element 67 thus particularly advantageously creates a frictional connection in addition to the positive connection, which compensates for the radial play caused by manufacturing tolerances. Particularly with regard to the connection known in the prior art by means of a press fit and injection-molded application of the magnet carrier 43, the illustrated positive and frictional connection enables simplified assembly and increased load capacity during operation.

[0049] In the embodiment shown, the magnet carrier 43 can comprise two opposing first connecting elements 65 and, offset by 90° thereto, two opposing second connecting elements 67, so that in the hexagonal recess 63 shown, the ribs 69 are each inserted into the opposing edges 71 of the recess 63 and the webs of the second connecting elements 67 are each centrally located and perpendicular to a surface of the recess 63. With sufficiently wide wings 77a, 77b, each edge 71 of the recess 63 is thus connected to the magnet carrier 43 either in a form-fitting or force-fitting manner, as in Fig. 3c.

[0050] The permanent magnet 45 can be manufactured as a plastic injection-molded magnet or as a pressed plastic-bonded magnet or as a pressed sintered magnet. The polarization of the permanent magnet 45 is preferably adapted to the recess 63 such that, for example, in a recess 63 with a polygonal contour, the pole transitions of the permanent magnet 45 are formed at the edges 71 or narrow points between the recess 63 and the outer wall of the permanent magnet 45, as shown in Fig. 3c. For example, a hexagonal recess can accommodate a six-pole permanent magnet. The magnet carrier 43 is preferably manufactured in one piece from a thermoplastic material using an injection molding process.

[0051] Fig. 4a to 4c show a section, an exploded view, and a front view of a rotor assembly according to another embodiment of the invention. Corresponding components are designated by the same reference numerals as in the Fig. 3a to 3b. As in the previously described embodiment, the rotor 5 comprises a magnet carrier 43 designed as a hollow shaft and a circular-cylindrical permanent magnet 45, in which a recess 63 is provided through which the magnet carrier 43 can be guided in order to connect the shaft 47 to the permanent magnet 45. Here, too, a gear or transmission wheel 47' is formed onto the free end of the shaft 47. Also as in the previously described embodiment, the recess 63 is designed as a hexagonal bore. Other, non-circular-cylindrical recesses are within the scope of the invention.

[0052] For connection to the permanent magnet 45, the magnet carrier 43 has at least one first connecting element 85, which establishes a positive connection with the recess 63, and at least one second connecting element 87, which establishes a force connection between the magnet carrier 43 and the permanent magnet 45.

[0053] The positive connection of the first connecting element 85 is established in particular by a linear contact, because the first connecting element 85 is designed in the manner of a protruding rib parallel to the shaft axis. This engages with an edge 71 of the recess 63, resulting in tangential contact points or contact lines 93. The second connecting element 87, which establishes a frictional connection with the permanent magnet 45, is designed in the manner of wings, the ends of which rest on the walls of the recess 63 and thereby exert pressure against the inner walls of the permanent magnet. In addition, the longitudinal ends of the wings 87 can engage with further edges 71 of the central recess 63.

[0054] In the second embodiment, the connecting elements 85, 87 form a Y-shaped structure, similar to the first embodiment, but here the rib and wings are integrated. This ensures both axial fastening of the magnet carrier in the recess 63 and centering by the tangential contact points 93. In addition, reference is made to the above description of the Fig. 3a to 3c are referred to.

[0055] In the magnet carrier 43 of this further embodiment, the first connecting elements 85, ie the ribs, are extended in the axial direction and form projecting extensions 89. With the aid of these extensions 89, the magnet carrier 43 can be additionally fixed, e.g., by hot caulking, after it has been inserted into the permanent magnet ring 45. Finally, the magnet carrier 43 in the embodiments of the Fig. 4a to 4c also have radial projections 91, which serve for the additional axial fixation of the magnet carrier 43 to the permanent magnet ring 45.

[0056] The Fig. The modification of the embodiment of the invention just described shown in Figures 5a to 5c does not differ from the design of the magnet carrier 43 and the permanent magnet 45 in the Fig. 4a to 4c. In this respect, reference is made to the above description and the same reference numerals are used. Fig. The modification shown in Figures 5a to 5c additionally has a fastening cap 95, which serves to axially and radially fix the magnet carrier 43 in the permanent magnet ring 45. The fastening cap 95 comprises a first set of clips 97 and a second set of clips 99. The clips 99 of the second set enclose the radial projections 91 in pairs for axially and radially fixing the permanent magnet 45 on the magnet carrier 43. The clips 97 of the first set engage the second connecting elements 87, i.e., the wings, so that these are additionally pressed outward against the inner surface of the recess 63 of the permanent magnet 45. This strengthens the force-fitting connection between the wings 87 and the inner wall of the permanent magnet.

[0057] Regarding the further features of the rotor, please refer to the above description of the Fig. 4a to 4c and the Fig. 3a to 3c are referred to.

[0058] Fig. 6 and Fig. 7 illustrate a gear unit as it can be used in a unit according to the described embodiment. Fig. 6 an exploded view of the gearbox and Fig. 7 a view from below of the assembled gearbox from Fig. 6. Corresponding components in the Fig. 6 and Fig. 7 are designated by the same reference numerals as in Fig. 1. The gear 9 of the assembly 1 comprises a plurality of double gears which are arranged in the Fig. 6 and Fig. 7 are designated 79a, 79b, and 79c. Each of the double gears participates in two gear stages, with a first gear stage being formed between the gear wheel 47' on the shaft of the electric motor and the first double gear wheel 79a, a second gear stage being formed between the first and second double gear wheels 79a, 79b, a third gear stage being formed between the second double gear wheel and the third double gear wheels 79b and 79c, and a third gear stage being formed between the third double gear wheel 79c and the output gear 81. In the embodiment shown, the third double gear wheel 79c comprises two identical double gear wheels 83, 83' connected in parallel, which mesh together with the second double gear wheel 79b to form the third gear stage, and with the output gear wheel 81 to form the fourth gear stage.The torque transmitted by the second double gear 79b is thus evenly distributed between the two third double gears 83, 83' and brought together again by these on the output gear 81.

[0059] As explained above, an increased torque is generated at the output gear 81 under a corresponding load due to the reduction ratio in the respective gear stages. This requires a correspondingly more robust design of the geometry and material of the gears at the output so that they can withstand the higher load. In practice, for example, in the last gear stage, i.e., from the third double gear 79c to the output gear 81, a torque can be transmitted that is ten times the torque transmitted by the first stage.If we assume that, for cost reasons and to limit space requirements, each gear is only designed to be as large and stable as the expected load in its gear stage requires, then in transmission chains with only one gear per stage the gears would have to be made from materials with different load-bearing capacities and / or with different geometries; in particular the gear in the last stage would have to be made from a particularly resilient material and / or with a reinforced tooth geometry and a thicker shaft in order to be able to transmit the maximum torque in all applications. This leads to increased manufacturing costs for component 1. If component 1 is to be used for different applications in which different nominal torques have to be transmitted, it must always be designed for the potentially greatest load.The drive unit according to the invention, on the other hand, allows a high torque to be transmitted to the output gear 81 while simultaneously relieving the load on the individual gears 83, 83' of the last stage. When using the two double gears 83, 83', they are driven in parallel by the preceding double gear 79b and, in turn, drive the output gear 81 in parallel. This halves the torque acting on the two double gears 83, 83', and accordingly, despite a lower load on the individual double gears 83, 83', an increased torque can be transmitted to the output gear 81. This, in turn, allows the use of a comparatively less robust and thus more cost-effective material, as well as a smaller tooth geometry, shaft diameter, etc.

[0060] The invention also allows one of the double gears 83, 83', for example, the double gear 83', to be subsequently removed from the transmission 9 if no increased torque at the output 81 is required. The function of the assembly 1 remains the same, with the only difference being that with a double gear 83, the maximum torque at the output 81 is lower. The transmission 9 is thus particularly versatile.

[0061] In an embodiment with a gear ratio of approximately 4 to 5 per gear stage and a speed at the output 81 between 3 and 10 rpm, for example, a nominal torque of approximately 1.2 Nm can be transmitted with a double gear 83 in the last stage at the output 81, and a nominal torque of approximately 1.75 Nm can be transmitted with two double gears 83 and 83'. This information is intended merely to illustrate the magnitude of the transmission according to the invention.

[0062] Preferably, plastics with a filler are used, for example, polyoxymethylene and various types of polyamide. Fiberglass, glass beads, or mineral fillers are used as fillers, resulting in different strengths of the double gears 83, 83' depending on the plastic or plastic mixture used. Polytetrafluoroethylene can also be used for lubrication.

[0063] Although the gearbox 9 in Fig. 6 and Fig.7 has been described with reference to gears and double gears, the gear mechanism 9 usable in the structural unit 1 according to the invention is not limited to gears and double gears. Rather, any gear mechanism and gear wheels can be used, for example, in a planetary gear mechanism, helical gear mechanism, worm gear mechanism, chain gear mechanism, or in a gear mechanism with a toothed belt drive, and in other gear mechanisms, gears, friction gears, worm gears, and others mounted on different shafts.

[0064] Due to the constant reduction of the gear stages and the resulting increase in torque, it is advantageous to use two gear wheels 83, 83' connected in parallel in front of the output in order to reduce the stress on the gear wheels of the last gear stage.

[0065] The features disclosed in the above description, the claims and the figures may be important both individually and in any combination for the realization of the invention in its various embodiments. List of reference symbols 1 unit 3 Stator 5 Rotor 7 Circuit board 9 gearboxes 11, 11' housing and cover 13 pot 15 pens 17 Slot insulation 19 Flange 21 eyelet 25 Return ring 27 Longitudinal groove 29 Deepening 31 bearing seat 33 Recess 35 lead 37 jetty 39 Opening 41 connecting pin 43 magnetic carriers 45 ring-shaped permanent magnet, ring magnet 47 Wave 47' gear wheel 49 Opening 53, 53', 53'', 53''' gear wheel 55a, 55b, 55c, 55d axes 57 struts 59 warehouse location 61 struts 63 Recess 65 first connecting element 67 second connecting element 69 Rib 71 Edge of the recess 73 lead 75 bending 77a, 77b wings 79a, 79b, 79c first, penultimate and last step 81 downforce 83, 83' double gear 85 first connecting element 87 second connecting element 89 extensions 91 radial projections 93 tangential contact points 95 Mounting cap 97 first clips 99 second clips

Claims

[1] Rotor assembly of a brushless DC motor with a magnet carrier (43) and with a ring magnet (45), wherein the ring magnet (45) has a central, non-circular cylindrical recess (63) and wherein the magnet carrier (43) carries the ring magnet (45) and has a first connecting element (65) and a second connecting element (67) which are designed such that the first connecting element (65) establishes a positive connection and the second connecting element (67) a non-positive connection to the recess (63) of the ring magnet (45), characterized by that the second connecting element (67) has bending elements (77a, 77b) which deform when the magnet carrier (43) is inserted into the recess (63). [2] Rotor assembly of a brushless DC motor with a magnet carrier (43) and with a ring magnet (45), wherein the ring magnet (45) has a central, non-circular cylindrical recess (63) and wherein the magnet carrier (43) carries the ring magnet (45) and has a first connecting element (65) and a second connecting element (67) which are designed such that the first connecting element (65) establishes a positive connection and the second connecting element (67) a non-positive connection to the recess (63) of the ring magnet (45), characterized by that the magnet carrier (43) has extensions which extend in the axial direction beyond the length of the ring magnet (45) when the ring magnet (45) is placed on the magnet carrier (43) in order to fix the ring magnet (45) on the magnet carrier (43) by hot-staking the extensions. [3] Rotor assembly of a brushless DC motor with a magnet carrier (43) and with a ring magnet (45), wherein the ring magnet (45) has a central, non-circular cylindrical recess (63) and wherein the magnet carrier (43) carries the ring magnet (45) and has a first connecting element (65) and a second connecting element (67) which are designed such that the first connecting element (65) establishes a positive connection and the second connecting element (67) a non-positive connection to the recess (63) of the ring magnet (45), characterized by that the base area of ​​the recess (63) of the ring magnet (45) corresponds to a uniform polygon, in particular a hexagon. [4] Rotor assembly according to one of the preceding claims, wherein the magnet carrier (43) is made of plastic. [5] Rotor assembly according to one of the preceding claims, wherein the first and second connecting elements (65, 67) and the shaft (47) are integrally formed on the magnet carrier (43). [6] Rotor assembly according to one of the preceding claims, wherein the first connecting element (65) is designed such that it at least partially makes line contact with the inner surface of the recess (63). [7] Rotor assembly according to one of the preceding claims, wherein the first connecting element (65) has webs (37) extending in the longitudinal direction of the magnet carrier (43), which protrude from the outer circumference of the magnet carrier (43) and establish a line contact with the inner surface of the recess (63). [8] A rotor assembly according to claim 1 and any one of the preceding claims, wherein the flexures are deformable vanes (77a, 77b) projecting from the outer periphery of the magnet carrier (43). [9] Rotor assembly according to one of the preceding claims, wherein the outer contour of the magnet carrier (43) is partially adapted to the inner contour of the recess (63). [10] Rotor assembly according to one of the preceding claims, wherein a gear (47') is formed on the shaft (47). [11] Rotor assembly according to one of the preceding claims, wherein the shaft (47) is a hollow shaft comprising a fixed axis (55a). [12] Rotor assembly according to claim 3 and any one of the preceding claims, wherein the ring magnet (45) is magnetized such that the transitions between south and north poles are located at the edges (71) of the regular polygon.

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