Electric motor

Abstract

The invention describes an electric motor comprising a shaft (5), a stator (1) having stator windings (2), a rotor (3) surrounding the stator (1) and comprising a short-circuit ring (12), permanent magnets (4) arranged on an inner side of the short-circuit ring (12), and a support (13) connecting the short-circuit ring (12) to the shaft (5), and a housing enclosing the rotor (3) and the stator (1) and having an opening through which the shaft (5) projects. According to the invention, the support (13) has several circulation openings (16) and several flow guide fins (17) for air circulation in one end face.

Description

[0001] The invention relates to an external rotor motor with an internally cooled stator and is based on an electric motor with the features specified in the preamble of claim 1, as known, for example, from EP 3 091 637 B1.

[0002] The electric motor known from EP 3 091 637 B1 has a cooling channel through which fluid flows, passing through an interior space surrounded by the stator. However, this method provides no or only insufficient cooling of the rotor's permanent magnets. At elevated temperatures, the magnetic properties of the permanent magnets deteriorate, leading to a decrease in the efficiency of the electric motor.

[0003] The object of the invention is to show a way in which the cooling of the permanent magnets of an external rotor motor of the type mentioned at the beginning can be improved.

[0004] This object is achieved by an electric motor having the features specified in the preamble of claim 1. Advantageous developments of the invention are the subject of subclaims.

[0005] The rotor of an electric motor according to the invention has a short-circuit ring, permanent magnets arranged on an inner side of the short-circuit ring, and a support that connects the short-circuit ring to the shaft. This support has several circulation openings and several flow guide ribs for air circulation on an axial end face facing away from the stator. In this way, the rotor can effect air circulation during operation, which leads to a more even temperature distribution in the electric motor and thus reduces the temperature of the permanent magnets.

[0006] For example, a circulation path may emanate from the circulation openings, which runs from the housing openings in a radial direction between the housing and the rotor to a circumferential edge of the rotor, then in an axial direction between the rotor and the housing, then around an end of the rotor facing away from the front side and between the rotor and the stator to the circulation openings.

[0007] An advantageous development of the invention provides that the stator surrounds an interior space in which a channel for the coolant runs. This allows two cooling mechanisms to be combined, thus achieving particularly efficient cooling.

[0008] A further advantageous development of the invention provides for the housing to be a sealed housing. For example, the housing may comprise a first housing part and a second housing part, between which an annular seal is pressed. The housing opening through which the shaft protrudes may be sealed, for example, with a shaft seal.

[0009] A further advantageous development of the invention provides that the flow guide ribs are arranged in pairs, and that each pair of flow guide ribs defines a flow channel between them, for example, a flow channel leading from one of the circulation openings to a peripheral edge of the support. In this way, particularly efficient air circulation can be achieved.

[0010] Further details and advantages of the invention are explained using an exemplary embodiment with reference to the accompanying drawings. They show: Fig. 1 an embodiment of an electric motor according to the invention in a sectional view; and Fig. 2 a view of the rotor of the electric motor.

[0011] The Fig. The electric motor shown in Figure 1 has a stator 1 with stator windings 2, a rotor 3 with permanent magnets 4 and a shaft 5 connected to the rotor 3 in a rotationally fixed manner. The rotor 3 and stator 1 are surrounded by a housing which has an opening from which the shaft 5 protrudes.

[0012] The housing comprises a first housing part 6 and a second housing part 7, between which a seal 8 is pressed. The opening through which the shaft 5 protrudes is sealed with a shaft seal 9. The housing is thus sealed against the ingress of liquid water. The first housing part 6 or the housing part 7 can have a pressure equalization opening closed with an air-permeable membrane that is impermeable to liquid water.

[0013] The stator 1 surrounds an interior space in which a channel 10 for cooling liquid runs. The channel 10 for cooling liquid leads from an inlet 11, which is arranged on the second housing part 7, at one axial end of the stator 1, along the housing opening through which the shaft protrudes, to the interior space surrounded by the stator 1. In the exemplary embodiment shown, the first housing part 6 has the opening through which the shaft 5 protrudes, and the second housing part 7 has an inlet 11 and an outlet for cooling liquid. However, it is also possible to provide the opening through which the shaft 5 protrudes, as well as the inlet and outlet, in the same housing part.

[0014] In Fig.Figure 2 shows the rotor 3 of the electric motor. The rotor 3 has a short-circuit ring 12, for example in the form of a stack of laminations, permanent magnets 4 arranged on an inner side of the short-circuit ring 12, and a carrier 13 connecting the short-circuit ring 12 to the shaft 5. The carrier 13 has a hub 14 through which the shaft 5 extends. In the illustrated embodiment, the shaft 5 is fastened to the carrier 13 by means of screws 23, but can also be connected to the carrier 13 in another way, for example by soldering or welding, or even be formed integrally with the carrier 13.

[0015] The carrier 13 has, on its axial end face facing the housing side containing the opening for the shaft 5, a plurality of circulation openings 16 and a plurality of flow guide ribs 17 for air circulation. The flow guide ribs 17 each extend in a curve from a circumferentially extending edge of the end face to one of the circulation openings 16. At their inner end, the flow guide ribs 17 point toward the circulation openings 16 in the direction of rotation, i.e., they extend in the circumferential direction. At their outer end, the flow guide ribs 17 extend in a radial direction. The flow guide ribs 17 are arranged in pairs; the flow guide ribs 17 of each of these pairs define a flow channel 18 between them, which leads from one circulation opening 16 to a circumferential edge of the carrier 13.

[0016] The flow channels 18 are part of a circulation channel that originates from the circulation openings 16. A first part of the circulation path runs within the flow channels 18, i.e., between the end face of the carrier 13 and the housing. A second part of the circulation path runs from a circumferential edge of the carrier 13 in the axial direction between the rotor 3 and the housing. The circulation path then leads around an axial end of the rotor 3 and between the rotor 3 and the stator 1 to the circulation openings 16.

[0017] In the electric motor shown, a circulation path emanates from the circulation openings 16, which runs between the housing and the rotor 3, around an end of the rotor 3 facing away from the front end, and between the rotor 3 and the stator 1 back to the circulation openings 16. Thus, there is a gap between the flow guide ribs 17 and the inner side of the housing facing them, for example, a gap of less than 5 mm, approximately a gap of 1 mm to 3 mm. The flow guide ribs 17 can, for example, have a height of 2 mm or more, approximately 2 mm to 5 mm. In the exemplary embodiment shown, the circulation openings 16 are located within 60% of the outer diameter of the carrier 3.

[0018] The combination of air circulation inside a housing with a liquid-cooled stator 1 enables particularly efficient cooling and thus a powerful electric motor with a compact design. The housing, for example the first housing part 6, can have ribs on its outside to improve heat dissipation to the ambient air, and ribs on its inside to better absorb heat from the air inside the housing. In the exemplary embodiment shown, the channel 10 for the coolant is realized with an insert 15 that is inserted into the stator 1 and, together with the stator 1, defines a section of the cooling channel. A further section of the channel 10 is defined by a plate 19 that delimits a section of the cooling channel 10 between itself and the insert 15 and between itself and the housing part 7. The second housing part 7 can, however, also be formed integrally with the insert 15 and the plate 19.

[0019] The further section of the cooling channel 10 can be used to cool electronic components 20 of a control electronics system. A circuit board 21 of the control electronics is attached to the housing part 7 and covered by a cover plate 22. List of reference symbols 1 stator 2 stator windings 3 Rotor 4 permanent magnets 5 Wave 6 Housing part 7 Housing part 8 Seal 9 Shaft seal 10 channel 11 Coolant inlet 12 short-circuit ring 13 carriers 14 Hub 15 deployment 16 circulation openings 17 flow guide ribs 18 flow channels 19 plate 20 electronic components 21 Circuit board 22 Cover plate 23 Screw QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] EP 3 091 637 B1 [0001, 0002]

Claims

[1] Electric motor with a wave (5), a stator (1) having stator windings (2), a rotor (3) surrounding the stator (1), which has a short-circuit ring (12), permanent magnets (4) arranged on an inner side of the short-circuit ring (12) and a carrier (13) connecting the short-circuit ring (12) to the shaft (5), and a housing which encloses the rotor (3) and the stator (1) and has an opening through which the shaft (5) protrudes, characterized by , that the support (13) has in one end face a plurality of circulation openings (16) and a plurality of flow guide ribs (17) for air circulation. [2] Electric motor according to claim 1, characterized by that the flow guide ribs (17) each extend in a curved manner from an edge of the end face extending in the circumferential direction to one of the circulation openings (16). [3] Electric motor according to one of the preceding claims, characterized by that the flow guide ribs (17) are arranged in pairs and flow guide ribs (17) of a pair define a flow channel (18) between them. [4] Electric motor according to one of the preceding claims, characterized by that the housing has a first housing part (6) and a second housing part (7), between which an annular seal (8) is pressed. [5] Electric motor according to one of the preceding claims, characterized by that the stator (1) surrounds an interior in which a channel (10) for cooling liquid runs. [6] Electric motor according to claims 4 and 5, characterized by that the first housing part (6) has the opening through which the shaft (5) projects, and the second housing part (7) has an inlet (11) and an outlet for cooling liquid. [7] Electric motor according to claim 5 or 6, characterized bythat the channel (10) for cooling liquid leads along an end of the stator (1) facing away from the end face of the carrier (13) to the interior space surrounded by the stator (1). [8] Electric motor according to one of the preceding claims, characterized by that the housing has a pressure equalization opening which is closed with an air-permeable membrane which is impermeable to liquid water. [9] Electric motor according to one of the preceding claims, characterized by that a circulation path emanates from the circulation openings (16), which runs between the housing and the rotor (3), around an end of the rotor (3) facing away from the front side and between the rotor (3) and the stator (1) to the circulation openings (16). [10] Electric motor according to one of the preceding claims, characterized by that there is a gap with a thickness of less than 5 mm between the flow guide ribs (17) and the inner side of the housing facing them. [11] Electric motor according to one of the preceding claims, characterized by that the flow guide ribs (17) point at their inner end in the direction of rotation towards the circulation openings (16). [12] Electric motor according to one of the preceding claims, characterized by that the flow guide ribs (17) run in a radial direction at their outer end. [13] Electric motor according to one of the preceding claims, characterized by that the housing has ribs on its outside. [14] Electric motor according to one of the preceding claims, characterized by that the flow guide ribs (17) have a height of at least 2 mm.

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