Inverter motor and method for cooling an inverter motor

Abstract

Inverter motor, wherein a stator is arranged in a first tubular housing part and a second tubular housing part radially surrounds the first tubular housing part, wherein an annular flow channel for cooling air is formed between the housing parts, characterized in that the first tubular housing part and the second tubular housing part are connected by radially extending webs (14) and that the radially extending webs (14) have axial bores through which a screw is inserted, wherein the screw connects the A-bearing shield (6) with the B-bearing shield (7) of the inverter motor.

Description

The invention relates to an inverter motor and a method for cooling an inverter motor. In this document, an inverter motor is understood to be an electrically operated drive unit comprising at least one motor unit and an electronic assembly, the inverter unit, for controlling the motor unit, in particular for regulating the speed and / or torque. The motor unit may comprise a permanent magnet rotor, a squirrel-cage rotor, or a combination of both, or it may be designed as an external rotor. From DE 10 2004 048 461 A1, it is known to design the housing of an electric machine more compactly despite efficient cooling. This is achieved by leaving the cooling channels of a housing, preferably designed as an extruded aluminum profile, open to the inside. The inner walls of the cooling channels are then formed by an inserted stator core. This allows the corner areas of the housing to be kept clear for assembly and saves material in the housing's manufacture. Furthermore, the open cooling air channels enable thin wall thicknesses in the profile, thus allowing for small motor dimensions with a simultaneously large cooling channel cross-section. DE 103 40 325 A1 describes an electric motor and a modular system of electric motors, comprising at least a stator housing, a rotor and a fan wheel, wherein the stator housing includes a B-bearing flange, in particular for receiving a B-side bearing of the rotor, wherein the fan wheel is connected to the rotor, in particular rotating with the rotor, wherein the fan wheel has a receptacle on its side facing the B-bearing flange, to which a ring is connected with the fan wheel, wherein evaluation electronics are detachably connected to the stator housing and sensors are connected and arranged with the evaluation electronics in such a way that the sensors interact with the ring in such a way that information about the angular position of the rotor can be transmitted from the evaluation electronics by means of a data line. DE 36 42 724 A1 describes an electric motor whose operating parameters speed and / or torque can be changed with a static frequency converter, in particular an electric motor in combination with a working unit driven by it, such as a pump, a fan, a machine tool or a tool. GB 2 220 800 A describes a brushless, electrically commutated motor for a barrel or container pump for operation on an AC power supply. US 2 769 105 A describes an electric motor that can be used in an environment containing magnetic particles. JP H07 - 59 292 A describes a rotating electronic machine suitable for improving the cooling efficiency of a rotor in a lathe. The invention is based on the objective of improving the heat dissipation of an inverter motor. According to the invention, the problem is solved in the case of the inverter motor according to the features specified in claim 1 and in the case of the method for cooling an inverter motor according to the features specified in claim 24. Key features of the invention of an inverter motor are that a stator is arranged in a first tubular housing part, and a second tubular housing part radially surrounds the first tubular housing part, with an annular flow channel for cooling air or a coolant being formed between the housing parts. Radially surrounded means that the radial jets passing through the first tubular housing part always also pass through the second tubular housing part. In this document, "tubular" generally refers to a part that is essentially discretely or continuously rotationally symmetrical about an axis, hollow inside, and has a wall thickness that is thin compared to its diameter. Thus, the flowing cooling air or coolant is surrounded on all sides by housing parts that can be used to dissipate heat from components of the inverter motor.The flow channel also forms a thermal barrier between the two housing parts. Each housing part can therefore be thermally connected to various components or assemblies of the inverter motor with low thermal resistance, without significant heat transfer from the components connected to one housing part to those connected to the other. The tubular design of the housing parts results in favorable flow conditions and low flow resistance. Furthermore, the arrangement of the second tubular housing part advantageously ensures that the coolant flow is directed over the entire axial length of the first tubular housing part, which forms part of the stator housing. This improves the cooling of the inverter motor. In an advantageous embodiment, a fan wheel is arranged on the rotor shaft, wherein the first tubular housing part is tightly sealed against the cooling air or coolant moved by the fan wheel. An advantage of this is that the stator is tightly sealed against contaminants transported by the coolant. In particular, even a liquid coolant can be used. In an advantageous embodiment, the first tubular housing section is closed by a B-type end shield, with a holding brake arranged between the B-type end shield and the fan wheel. The B-type end shield is the end shield of the motor unit located opposite the output side. The B-type end shield protects the interior of the stator housing from the flowing coolant. The coolant, whether air or a cooling liquid, therefore does not reach the stator winding and cannot cause contamination there. The arrangement of a holding brake between the motor unit and the fan wheel also allows the fan wheel to be cooled and thus used as a substitute for a braking resistor, since the holding current for the armature winding's holding coil is used to convert mechanical energy into heat during generator operation. According to the invention, the first tubular housing part and the second tubular housing part are connected by radially extending webs. This provides a connection between the housing parts that can withstand torque, for example, when the second tubular housing part is to be attached to a base or frame. Simultaneously, a thermal barrier between the housing parts is formed, because, on the one hand, the contact area of ​​the housing parts is small compared to the total area of ​​the housing parts, and on the other hand, the webs are cooled by the coolant flow. Therefore, heat transfer from the stator to the second tubular housing part is very low. According to the invention, the radially extending webs have axial bores through which a screw is inserted, the screw connecting the A-bearing shield to the B-bearing shield of the inverter motor. The A-bearing shield is the motor's bearing shield through which the output shaft protrudes. Preferably, a gear flange is formed on the A-bearing shield. Thus, the components necessary for connecting the stator housing are concealed within the webs and do not obstruct the coolant flow. In particular, the webs can be smooth and designed with a flow-dynamically favorable shape, preventing any residues of contaminants in the coolant from adhering to the housing parts. The formation of a gear flange on the A-bearing shield decouples the first housing part from the second housing part during power generation in the motor unit. This relieves the radially extending webs of stress.They can therefore be made thinner, which improves the flow conditions in the flow channel. In an advantageous embodiment, additional radially extending webs connect the first and second tubular housing parts, wherein these additional radially extending webs do not have axial bores for receiving a screw. The additional webs can therefore be manufactured with a reduced material thickness. This reduces the overall weight and flow resistance of the flow channel while still providing a sufficiently stable connection between the housing parts. In an advantageous embodiment, the first tubular housing part is arranged concentrically within the second tubular housing part. This creates a flow channel that cools the stator from all sides. The entire stator housing surface is thus available for cooling. In an advantageous embodiment, the first tubular housing part, the second tubular housing part, and the radially extending webs are manufactured from a single casting. This provides a simple and cost-effective manufacturing process. Aluminum is preferably used. The housing parts are slightly conical on the surfaces facing the flow channel. To form the inverter motor, the stator core is inserted or pressed into the first tubular housing part, the motor shaft is inserted, and the bearing shields are fitted. In an advantageous embodiment, a terminal box extension for a motor terminal box is formed on the second tubular housing section, with the base of the terminal box extension being formed by a portion of the second tubular housing section. An advantage of this design is the provision of a mounting area for the electronics of the inverter unit. Due to the turbine-like design of the flow channel, the otherwise conventional cooling fins on the motor unit are unnecessary. This allows the motor terminal box to be mounted directly onto the outer housing. This saves material, as the motor terminal box does not require a separate base but can utilize the outer housing to form its base. In a preferred embodiment, the second tubular housing section and the terminal box attachment are manufactured from a single casting. An advantage of this design is that the motor terminal box housing is thermally very well connected to the second tubular housing section and is thus also cooled. Furthermore, the motor terminal box does not need to be mounted separately; only a cover needs to be fitted to close off the interior of the motor terminal box. In an advantageous embodiment, the motor terminal box contains electronic power components for motor control, wherein the area of ​​the second tubular housing part has a flat surface against which the electronic power components are mounted for heat dissipation. This provides a thermal connection with low thermal resistance between the main heat sources and the cooling surfaces of the cooling system, i.e., the inner surface of the second tubular housing part. The flat surface is preferably formed in the casting and is made particularly smooth and flat by milling, grinding, or another machining process. Power components, especially power semiconductors, can thus be easily mounted on it for heat dissipation. Preferably, thermal paste is also applied between the power components and the flat surface.The power components preferably have a metallic contact surface which is used for contacting and heat dissipation. In an advantageous design, the electronic power components are mounted on a printed circuit board and pressed onto the flat surface by the board's inherent tension. This allows for simple installation of the power components in the inverter unit. Additional means for fixing the power components to the contact surface are unnecessary. In an advantageous embodiment, the flat surface is arranged in the axial region of the annular flow channel. Thus, the main heat sources of the converter unit are located in the area of ​​the cooling system where the cooling capacity is greatest. In an advantageous embodiment, a radially extending web has a cable entry through which a motor connection cable is routed, connecting the motor windings to the power electronics. An advantage of this design is that the cables between the control electronics of the inverter unit and the motor unit do not obstruct the coolant flow. In a preferred embodiment, the second tubular housing part is axially closed on one side by a fan cover. This has the advantage of protecting the fan wheel against accidental external contact. Furthermore, larger particles cannot enter the flow channel and clog it. In an advantageous embodiment, the radially extending webs with axial bores terminate in axial ribs in the axial region of the fan. These ribs feature a blind hole at their end for receiving mounting screws for the fan cover. This reinforces the second tubular housing section without significantly increasing flow resistance in the airflow channel. The reinforcement can be used for the stable mounting of the fan cover or for the secure attachment of additional options, such as a tachometer, a rotary encoder, or an additional external fan. In an advantageous embodiment, an annular receptacle is formed on the first tubular housing section. An annular insert of the B-bearing shield is inserted into this receptacle, with a circumferential edge of the annular receptacle being chamfered. This chamfer creates a circumferential gap between the receptacle and the annular insert, and a rubber ring is placed in this gap. Before assembly, the rubber ring is clamped onto the B-bearing shield insert. The B-bearing shield, with the rubber ring, is then inserted into the receptacle, thus creating a tight seal. Assembly can be performed with one hand; applying or holding a sealant during assembly of the B-bearing shield with the stator housing is unnecessary. The flow channel can therefore be designed with a narrower profile, and access to the connection point on the first tubular housing section is not required. In an advantageous embodiment, the second tubular housing part has an approximately square cross-section, wherein the radially extending webs with axial bores are arranged in the corners of the square cross-section, and the radially extending webs without axial bores are arranged in the circumferential direction between the radially extending webs with axial bores. Preferably, the first tubular housing part is designed with a circular cross-section and conforms to the stator core shape. The radially extending webs can thus be made thinner, as they only need to bridge a small gap between the housing parts. In a preferred embodiment, a manual release lever for the holding brake is guided through a lateral opening in the second tubular housing part. An advantage of this is that the holding brake can be released when de-energized. Key features of the invention of a method for cooling an inverter motor are that a fan impeller moves an airflow or a coolant flow through a flow channel, wherein the flow channel is formed and bounded by an inner housing part and an outer housing part, the power electronics of the inverter motor transfer heat to the outer housing part, the inner housing part encloses the motor unit of the inverter motor, the motor unit transfers heat to the inner housing part, and the fan impeller is driven by the motor unit. Thus, a cooling method is provided in which the power electronics and the motor unit are cooled together without the components interfering with each other. The cooling surfaces are directed inwards; cooling fins on the outer surfaces are unnecessary.Since the airflow or coolant flow is routed through the flow channel between the two main heat sources of the inverter motor, the motor unit on the one hand and the power electronics on the other, it represents an effective thermal barrier between these main heat sources. According to the invention, the flow channel surrounds the inner housing part in a ring-like manner. This provides a method in which the entire surface of the stator housing can be used for cooling. Cooling fins on the surface of the stator housing are therefore unnecessary. In an advantageous embodiment, the flow channel runs in the axial direction. Thus, the inverter motor's own fan can be used to drive the coolant. According to the invention, the outer housing part is connected to the inner housing part by radially extending webs, which form a thermal barrier between the outer and inner housing parts. A turbine-shaped channel is thus used to direct the coolant flow. The coolant flow therefore encounters minimal flow resistance. Consequently, large quantities of coolant can be passed over the cooling surfaces of the housing parts per unit of time. This increases the cooling capacity. Furthermore, the thermal barrier prevents the power electronics from also overheating if the motor unit overheats, or vice versa. In an advantageous embodiment, the airflow cools a holding brake, whereby in generator mode, a coil of the holding brake is supplied with a higher current than in motor mode. In particular, the current in generator mode is significantly higher than the current required to hold the brake, with the additional current flowing through the holding brake coil being supplied from the DC link of the motor control. Thus, an additional braking resistor is unnecessary, or at least a smaller resistor can be used than would otherwise be required by the application. The inverter motor can be used in four-quadrant operation. Since the holding brake is arranged on the motor shaft and connected to the B-bearing shield of the motor unit, the coolant flow even forms a thermal barrier between the holding brake and the power electronics.This protects the inverter electronics from overheating during generator operation due to the braking energy released as heat. Further advantages arise from the dependent claims. The invention is not limited to the combination of features of the claims. For those skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art. The invention will now be explained in more detail with the help of illustrations: It shows: - Fig. 1 a sectional view of a motor according to the invention with electronics and fan, - Fig. 2 another view of the motor from Fig. 1, - Fig. 3 the motor from Fig. 1 with a view of the output shaft, - Fig. 4 the motor from Fig. 1 with a view of the fan wheel and - Fig. 5 a detail from Fig. 2 . Fig. 1 shows an axial section through a motor 1. The motor 1 is designed as an inverter motor and comprises a motor unit 50 and an inverter unit 51 with power electronics. The motor unit 50 comprises a motor shaft 2 with a magnet carrier 3, onto which permanent magnets 4 are bonded. The motor shaft 2 is fixed in a bearing 8 and a bearing 9. The motor unit 50 further comprises a stator lamination stack 5 with the stator winding. The stator lamination stack 5 is clamped and held in a stator housing 10. The stator housing 10 has a tubular shape and is closed at one end by an A-bearing shield 6 and at the other end by a B-bearing shield 7. A bearing 8, 9 is arranged in each of the bearing shields 6, 7. The bearing shields 6, 7 and the stator housing 10 thus seal the stator interior 26 tightly against the outside. For a tight seal, a chamfer 25 is formed on an annular edge of the tubular stator housing 10 facing the B-bearing shield, which creates an annular space into which a rubber ring is inserted for sealing.A gearbox flange is formed on the A-bearing shield 6 of the motor unit 50. A holding brake 12 is arranged on the motor shaft 2 outside the B-bearing shield 7. The holding brake 12 comprises coils 48 through which an armature disk 49 can be released. The coils 48 are controlled via a brake control unit 43. The cable of the brake control unit 43 is routed through the B-bearing shield 7 into the stator interior 26. The holding brake is sealed against the outside by a shaft seal 23 and a brake seal 24. The brake seal 24 is designed as a rubber sleeve that surrounds the sliding area of ​​the anchor disc 49 in an annular manner and is formed from two frustoconical sections, like the fold of a round bellows. This allows the brake seal 24 to vary in length. Furthermore, a fan wheel 11 is arranged on the motor shaft 2. Thus, an intrinsic fan is formed on the inverter motor 1.The motor unit 50, holding brake 12, and fan wheel 11 are enclosed by an outer housing 13. The outer housing 13 has a tubular shape. The concentric, nested arrangement of the tubular stator housing 10 and the tubular outer housing 13 forms a turbine-like flow channel 27 through which the fan wheel 11 moves cooling air. The outer housing 13 and the stator housing 10 are connected by a radially extending web 14, which penetrates the annular, turbine-like flow channel 27 at a narrow angle. The web 14 extends axially from the base of the stator housing 10 for the B-bearing shield 7 to the gearbox-side opening of the tubular outer housing 13. The tight seal of the stator interior 26 and the interior of the holding brake 12 protects sensitive parts of the inverter motor 1 from contamination, which may be transported, for example, by the cooling air in the flow channel 27.The cooling air cools at least the motor unit 50 and the holding brake 12. The cooling air escapes through the annular opening of the outer housing on the gearbox side. A sensor 35 is mounted on the outer side of the holding brake 12, which detects and counts the passage of sensor flags 36 on the inner side of the fan wheel 11. Thus, the rotational speed and angular position of the motor shaft 2 can be determined. The tubular outer housing 13 is closed off on the fan side by a fan cover 22. A terminal box extension 15 is formed on the top of the outer housing 13 to accommodate the electronics of the inverter unit 51 of the inverter motor. The base of the terminal box extension 15 is formed by the outer housing 13, and the side wall of the terminal box extension 15 is integrally formed with the outer housing 13. A cover 16 is placed on the terminal box extension 15. The cover 16 has connection holes for routing connecting cables, for example, for connection to a power supply or a communication bus. Thus, the connection cable extension 15 and the cover 16 enclose a terminal box interior 52 and form a housing for the inverter electronics that is tightly sealed to the outside. The inverter electronics are arranged on a printed circuit board 17. Electronic power semiconductors 18, as well as other electronic components 41 and connectors 21, are mounted on the printed circuit board 17. The power semiconductors 18 are supplied from the intermediate circuit of the inverter unit and generate a rotating magnetic field, which drives the winding of the motor unit 50. A flat contact surface 19 is formed on the base of the terminal box extension 15, onto which a metallic surface of the power semiconductor 18 is placed. Thermal paste is applied between the power semiconductor 18 and the contact surface 19 to improve thermal contact. Connector 21 is provided for connecting the stator winding. A DC link capacitor is located behind connector 21. Thus, the DC link capacitor is positioned in close proximity to the power semiconductors 18 on the underside of the circuit board 17. A connection channel 20 surrounds connector 21 and the DC link capacitor. Fig. 5 shows a section of Fig. 1 of a power semiconductor 18, which is placed on the mounting surface 19 for thermal connection. The mounting surface 19 is formed as a flat, machined surface on the outside of the outer housing 13. Further power semiconductors are placed together in the same manner on the rectangular mounting surface 19 behind the power semiconductor 18 shown. The mounting surface 19 is laterally bounded by projections 44, which fix the position of the power semiconductors 18. The circuit board 17 in Fig. 1 is designed as a flat plate and rests on further support surfaces 40 on the base of the terminal box attachment 15. The elastic internal stress of the circuit board presses the power semiconductors 18 onto the support surface 19, resulting in good thermal contact between the power semiconductors 18 and the outer housing 13. Thus, the power semiconductors 18 are cooled by the outer housing 13, with the heat being distributed over the entire circumference of the tubular outer housing 13. The cooling air moved inside the outer housing 13 by the fan wheel 11 further cools the power semiconductors, since the support surface 19 for the power semiconductors 18 is located in the axial region of the flow channel 27. To protect the electronics of the inverter unit 51, a shell-shaped mounting frame 37 is inserted into the terminal box extension 15. The circuit board 35 is attached to a mounting frame 37 by tabs. The mounting frame 37 completely covers the circuit board 17, except for a few openings for connectors 38. The mounting frame 37 is screwed to the base of the lower part. Thus, the electronics are protected from accidental contact or damage from above, i.e., towards the opening of the terminal box extension. After installation in the mounting frame 37, the circuit board 17 is potted with a thermally conductive potting compound. This potting compound provides thermal coupling between other electronic components 41 of the circuit board 17 and further flat contact surfaces 40 in the base of the terminal box. A protective film, perforated at the contact surfaces, is inserted between the potting compound and the base. The mounting frame 37 has reinforcements extending across its upper surface. This allows the clamping force to be transferred to the circuit board after the mounting frame is screwed on, and from there to the power components 18. The latter are thus pressed against the contact surface 19 and fixed in place. A layer of elastomer is arranged between the power semiconductors 18 and the circuit board 17, pressing the power semiconductors 18 onto the contact surface 19. This ensures good heat dissipation from the power components 18 via the outer housing 10. The interior of the terminal box 52 and the interior of the stator 26 are connected by a connection channel 20 and a cable gland 42 for routing the cables for the motor control and the brake control. In generator mode, at least one coil 48 of the holding brake 12 is supplied with a current from the intermediate circuit that is greater than the current required to hold the brake disc 49. The additional heat generated in the holding brake 12 by the increased current is dissipated by the cooling air. The mounting frame 37 has a flange with tongues. A further circuit board (not shown) for signal electronics, the rectifier, and the DC link capacitor of the inverter can be inserted into this flange. The tongues engage with the tabs when the further circuit board is inserted, thus holding it in place. The further circuit board is electrically connected to the circuit board 17 via connectors 38. The further circuit board includes means for connecting the inverter's power supply and means for connecting the data communication lines. Fig. 2 shows another, partially cutaway view of the inverter motor 1 from Fig. 1. Visible is a further web 29, which connects the outer housing 13 to the stator housing 10. An axially extending bore 30 is provided in the web 29, extending from one end of the tubular stator housing 10 to the other, and a screw 31 is inserted through this bore. The screw 31 is inserted through a bore in the B-bearing shield 7 and screwed into a threaded hole 34 with a thread 32. Four more such screws are provided in further webs and, together with the screw 31, hold the A-bearing shield and B-bearing shield firmly together with the stator housing 10. Fig. 5 shows a detail from Fig. 1 of the tight connection between the B-bearing shield 7 and the stator housing 10. A connecting area 54 connects the stator housing 10 to the outer housing 13. The connecting area 54 encloses the connection channel 20. At the transition of the connecting area 54 to the stator housing 10, an annular receptacle 47 is formed for an annular insert 46, the annular insert 46 being encompassed by the B-bearing shield 7. The insert 46 fits into the receptacle 47. On the receptacle 47, a chamfer 25 is formed on an annular edge, circumferencing the motor shaft 2. This chamfer, together with a groove on the B-bearing shield of the insert 46, forms an annular recess 45 into which a rubber ring, circumferencing the motor shaft 2, is inserted.The rubber ring can be clamped onto the insert 46 before the B-bearing shield is inserted into the outer housing 13, making it possible to seal the connection between the B-bearing shield 7 and the stator housing 10 with one hand. The web 29 shown in Fig. 2 extends axially into a reinforcing rib 28, which reaches to the end of the tubular outer housing 13. A blind hole is provided in the end of the reinforcing rib 28 to receive a screw 33, which holds the fan cover 22 in place. Connectors 38 and 39 are mounted on the top side of the circuit board 17, protruding through cutouts in the cover 37. This allows the power supply and a communication connection to be connected to the circuit board 17 without having to remove the protective cover 37. Fig. 3 shows the inverter motor 1 from the gearbox side with the A-end shield 6 removed. The outer housing has an approximately square cross-section, with the sides of the square slightly curved outwards and the corners of the square rounded. The outer housing 13 is connected to the stator housing 10 at each of the four corners by a web 29. A through axial bore 30 is provided in each web 29, through which screws are inserted to connect the A-end shield 6 to the B-end shield 7. To provide space for the bores 30 and to ensure a minimum stability of the connection between the housings, each web 29 extends over a certain angular range. The outer housing 13 is connected to the stator housing 10 by three further webs 14. These webs 14 have no bores and are therefore thinner than the webs 29.They extend over a smaller angular range in the depicted radial plane than the webs 29. Each web 14 is adjacent to webs 29. The connecting area 54, which encloses the connection channel 20, establishes a further connection between the stator housing 10 and the outer housing 13. The webs 14, 29, the connection area 54, the stator housing 10, and the outer housing 13 form axially extending cavities that together create a turbine-like flow channel 27 for cooling air, extending annularly around the entire circumference of the stator housing 10. Thus, the motor unit 50 is cooled from all radial directions along the entire outer surface of the stator housing 10. The outer housing 13 also confines this flow channel 27 in all radial directions. Heat from the power semiconductors of the inverter unit 51 is therefore distributed around the entire circumference of the flow channel 27, resulting in high cooling capacity. Fig. 4 shows the inverter motor 1 from Fig. 1 with the fan cover 22 removed. The B-bearing shield with the mounted brake 12 is attached to the stator housing 10 by the four screws 31. The four reinforcing ribs 28 are reinforced, meaning they have a material thickness in the circumferential direction that allows the mounting of additional motor options in place of the fan cover 22. This creates a stable mechanical interface onto which standardized additional modules, such as a more precise encoder, can be mounted. A hand-operated air lever 56 protrudes through a lateral opening 55 in the outer housing 13. The outer housing 13, stator housing 10, terminal box extension 15, and webs 14, 29 are manufactured as a single casting. Since the A-bearing shield 6 is directly connected to the stator housing 10, the motor unit 50 is supported only via the stator housing 10 to generate an output torque. Similarly, the holding brake 12 is mounted on the B-bearing shield 7, and the latter on the stator housing 10. Thus, in its retracted state, the holding brake 12 is also supported only by the stator housing 10 and further by the gearbox flange of the A-bearing shield 6. Only when the inverter motor is mounted on a base which is mounted via feet additionally attached to the outer housing 13 are the webs 14, 29 included in the torque transmission. Reference symbol list 1 Motor 2 Motor shaft 3 Magnet carrier 4 Permanent magnet 5 Stator lamination stack 6 A-bearing shield 7 B-bearing shield 8 Bearing 9 Bearing 10 Stator housing 11 Fan wheel 12 Holding brake 13 Outer housing 14 Web 15 Terminal box attachment 16 Cover 17 Circuit board 18 Power semiconductor 19 Contact surface 20 Connection channel 21 Connector 22 Fan cover 23 Shaft seal 24 Brake seal 25 Chamfer 26 Stator interior 27 Flow channel 28 Reinforcing rib 29 Web 30 Bore 31 Screw 32 Thread 33 Screw 34 Threaded hole 35 Sensor 36 Sensor tab 37 Mounting frame 38 Connector plug 39 Connector plug 40 Contact surface 41 Component 42 Cable entry 43 Brake control 44 Attachment 45 Recess 46 Insert 47 Receptacle 48 Coil 49 Anchor disc 50 Motor unit 51 Inverter unit 52 Terminal box interior 53 Opening 54 Connection area 55 Opening 56 Manual release lever

Claims

Inverter motor, wherein a stator is arranged in a first tubular housing part and a second tubular housing part radially surrounds the first tubular housing part, wherein an annular flow channel for cooling air is formed between the housing parts, characterized in that the first tubular housing part and the second tubular housing part are connected by radially extending webs (14) and that the radially extending webs (14) have axial bores through which a screw is inserted, wherein the screw connects the A-bearing shield (6) with the B-bearing shield (7) of the inverter motor. Inverter motor according to claim 1, characterized in that a gear flange is formed on the A-bearing shield (6). Inverter motor, wherein a stator is arranged in a first tubular housing part and a second tubular housing part radially surrounds the first tubular housing part, wherein an annular flow channel for cooling air is formed between the housing parts, characterized in that a fan wheel (11) is arranged on the rotor shaft, wherein the first tubular housing part is tightly sealed against the cooling air moved by the fan wheel (11), and that the first tubular housing part is closed off by a B-bearing shield (7) and a holding brake (12) is arranged between the B-bearing shield (7) and the fan wheel (11). Inverter motor according to claim 1 or 2, characterized in that the first tubular housing part, the second tubular housing part and the radially extending webs (14) are made from a single casting, in particular are formed in one piece. Inverter motor according to claim 1, 2, or 4, characterized in that a fan wheel (11) is arranged on the rotor shaft, wherein the first tubular housing part is tightly sealed against the cooling air moved by the fan wheel (11). Inverter motor according to 2, 4, or 5, characterized in that the first tubular housing part is closed off by a B-bearing shield (7) and a holding brake (12) is arranged between the B-bearing shield (7) and the fan wheel (11). Inverter motor according to claim 3, characterized in that the first tubular housing part and the second tubular housing part are connected by radially extending webs (14). Inverter motor according to claim 7, characterized in that the radially extending webs (14) have axial bores through which a screw is inserted, wherein the screw connects the A-bearing shield (6) with the B-bearing shield (7) of the inverter motor, in particular wherein a gear flange is formed on the A-bearing shield (6). Inverter motor according to claim 1, 2, 4, 5 or 8, characterized in that additionally radially extending webs (14) connect the first tubular housing part and the second tubular housing part, which do not have axial bores for receiving a screw. Inverter motor according to one of claims 1 to 9, characterized in that the first tubular housing part is arranged concentrically in the second tubular housing part. Inverter motor according to one of claims 1 to 10, characterized in that a terminal box extension (15) for a motor terminal box is formed on the second tubular housing part, wherein the bottom of the terminal box extension (15) is formed by a region of the second tubular housing part. Inverter motor according to claim 11, characterized in that the second tubular housing part and the terminal box attachment (15) are made from a single casting. Inverter motor according to claim 11 or 12, characterized in that the motor connection box contains electronic power components for motor control, wherein the area of ​​the second tubular housing part has a flat surface on which the electronic power components are attached for heat dissipation. Inverter motor according to claim 13, characterized in that the electronic power components are mounted on a printed circuit board (17) and are pressed onto the flat surface by the residual voltage of the printed circuit board (17). Inverter motor according to claim 13 or 14, characterized in that the flat surface is arranged in the axial region of the annular flow channel. Inverter motor according to claim 1, 2, 4, 5, 6, or 7, characterized in that a radially extending web (14) has a cable passage (42) through which a motor connection cable is routed, which connects the windings of the motor (1) to the power electronics. Inverter motor according to claim 16, characterized in that a connector for the motor connection cable is arranged in the radially extending web (14) with cable passage (42). Inverter motor according to claim 16 or 17, characterized in that an intermediate circuit capacitor is arranged in the radially extending web (14) with cable passage (42). Inverter motor according to one of claims 1 to 18, characterized in that the second tubular housing part is axially closed on one side by a fan cover. Inverter motor according to claim 1, 2, 4, 5, 6, 7, or 8, characterized in that the radially extending webs (14) with axial bore in the axial area of ​​the fan terminate in axial ribs which have a blind bore at their end for receiving fastening screws for the fan cover. Inverter motor according to one of claims 1 to 20, characterized in that an annular receptacle (47) is formed on the first tubular housing part, into which an annular insert (46) of the B-bearing shield (7) is inserted, wherein a circumferential edge of the annular receptacle (47) is provided with a chamfer, by which a circumferential gap between annular receptacle (47) and annular insert (46) is left open, wherein a rubber ring is inserted into the circumferential gap. Inverter motor according to claim 1, 2, 4, 5, 6, 7, or 8, characterized in that the second tubular housing part has an approximately square cross-section, wherein the radially extending webs (14) with axial bore are arranged in the corners of the square cross-section and the radially extending webs (14) without axial bore are arranged in the circumferential direction between the radially extending webs (14) with axial bore. Inverter motor according to claim 3 or 6, characterized in that a hand release lever (56) of the holding brake (12) is guided through a lateral opening of the second tubular housing part. A method for cooling an inverter motor according to one of the preceding claims, characterized in that a fan wheel (11) moves an airflow or a coolant through a flow channel, wherein the flow channel is formed by an inner housing part and an outer housing part, power electronics of the inverter motor transfer heat to the outer housing part, the inner housing part encloses the motor unit (50) of the inverter motor, the motor unit (50) transfers heat to the inner housing part, the fan wheel (11) is driven by the motor unit (50), the flow channel surrounds the inner housing part in an annular manner, and the outer housing part is connected to the inner housing part by radially extending webs (14), wherein the webs (14) form a thermal barrier between the outer housing part and the inner housing part. Method according to claim 24, characterized in that the flow channel runs in the axial direction. Method according to one of claims 24 or 25, characterized in that the airflow cools a holding brake (12), wherein in generator operation a coil (48) of the holding brake (12) is supplied with a higher current than in motor operation. Method according to one of claims 24 to 26, characterized in that the inner housing part, outer housing part and the radially extending webs (14) are made from a single casting, in particular are formed in one piece. Method according to one of claims 26 to 27, characterized in that the current in generator operation is significantly higher than the current required to hold the holding brake (12). Method according to one of claims 26 to 28, characterized in that in generator operation the additional current flowing through the coil (48) of the holding brake is supplied from the intermediate circuit of a motor control.

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