Electric motor

Abstract

It is described an electric motor comprising: a shaft (5); a stator (1) having a stator winding (2); a rotor (3) surrounding the stator (1) and having a back iron ring (12), permanent magnets (4) arranged on the inner side of the back iron ring (12), and a bracket (13) connecting the back iron ring (12) to the shaft (5); a housing enclosing the rotor (3) and the stator (1) and having an opening for the connection of the shaft (5), the housing connecting the back iron 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) protrudes. According to the utility model, the support (13) is provided with a plurality of circulation openings (16) and a plurality of flow guide ribs (17) which are used for air circulation in the end face.

Description

Technical Field

[0001] The invention relates to an external rotor motor with an internally cooled stator and is based on an electric motor which is known, for example, from EP 3 091 637 B1. Background Art

[0002] The electric motor known from EP 3 091 637 B1 has a cooling channel through which a liquid flows and which passes through the inner space surrounded by the stator. However, in this way, cooling of the permanent magnets of the rotor is not achieved or is achieved insufficiently. At elevated temperatures, the magnetic properties of the permanent magnets deteriorate, which leads to a reduction in the efficiency of the electric motor. Utility Model Content

[0003] The object of the invention is to show how the cooling of the permanent magnets of an outer rotor motor of the abovementioned type can be improved.

[0004] The rotor of the electric motor according to the utility model comprises: a back iron ring, a permanent magnet arranged on the inner side of the back iron ring, and a bracket connecting the back iron ring to the shaft. The bracket has a plurality of circulation openings and a plurality of flow guide ribs for air circulation on the axial end face facing away from the stator. In this way, the rotor can cause air circulation during operation, which makes the temperature distribution in the electric motor more uniform and thus reduces the temperature of the permanent magnet.

[0005] For example, the circulation path may start from a circulation opening and extend from the opening in a radial direction between the housing and the rotor to a circumferential edge of the rotor, then extend in an axial direction between the rotor and the housing, and then extend around an end of the rotor's reverse end surface and back to the circulation opening between the rotor and the stator.

[0006] An advantageous further development of the invention is that the stator surrounds an interior in which the channels for the cooling liquid extend. In this way, two cooling mechanisms can be combined to achieve particularly efficient cooling.

[0007] Another advantageous improvement of the utility model proposes that the housing is a sealed housing. For example, the housing can have a first housing part and a second housing part, and an annular seal is arranged between the first housing part and the second housing part. For example, the housing opening through which the shaft protrudes can be sealed with a shaft seal.

[0008] Another advantageous improvement of the utility model proposes to arrange the flow guiding ribs in pairs and a pair of flow guiding ribs defines a flow channel between them, for example, a flow channel leading from one of the circulation openings to the peripheral edge of the support. In this way, a particularly efficient air circulation can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Further details and advantages of the invention are explained with reference to the accompanying drawings.

[0010] Figure 1 A cross-sectional view showing an embodiment of an electric motor according to the present invention; and

[0011] Figure 2 A view of a rotor of an electric motor is shown. DETAILED DESCRIPTION

[0012] Figure 1 The electric motor shown comprises a stator 1 with a stator winding 2, a rotor 3 with permanent magnets 4, and a shaft 5 which is connected in a rotationally fixed manner to the rotor 3. The rotor 3 and the stator 1 are surrounded by a housing having an opening from which the shaft 5 protrudes.

[0013] The housing has 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 which is closed with a gas-permeable membrane that is impermeable to liquid water.

[0014] The stator 1 surrounds an interior space in which a channel 10 for a coolant extends. The channel 10 for the cooling liquid leads from an inlet 11 arranged on the second housing part 7 to the interior space surrounded by the stator 1, the channel extending from a housing opening through which the shaft protrudes at an axial end of the stator 1. In the embodiment shown, the first housing part 6 has an opening through which the shaft 5 protrudes, and the second housing part 7 has an inlet 11 and an outlet for the cooling liquid. However, the opening through which the shaft 5 protrudes and the inlet and outlet can also be provided in the same housing part.

[0015] Figure 2 A rotor 3 of an electric motor is shown. The rotor 3 comprises a back iron ring 12 , for example in the form of a stack of sheet metal, permanent magnets 4 , which are arranged inside the back iron ring 12 , and a bracket 13 , which connects the back iron ring 12 to the shaft 5 .

[0016] The bracket 13 has a hub 14 through which the shaft 5 protrudes. In the embodiment shown, the shaft 5 is attached to the bracket 13 by means of screws 23, but may also be connected to the bracket 13 in other ways, such as by brazing or welding, or even be made in one piece with the bracket 13.

[0017] In the axial end face of the bracket 13 facing the housing side with the opening for the shaft 5, the bracket has several circulation openings 16 and several flow guide ribs 17 for air circulation. The flow guide ribs 17 each extend from the edge of the end face extending in the circumferential direction and bend toward one of the circulation openings 16. The flow guide ribs 17 point to the circulation opening 16 in the direction of rotation at their inner ends, that is, the flow guide ribs extend in the circumferential direction at their inner ends. The flow guide ribs 17 extend in the radial direction at their outer ends. The flow guide ribs 17 are arranged in pairs; each pair of these paired flow guide ribs 17 defines a flow channel 18 between them, which flows from the circulation opening 16 to the circumferential edge of the bracket 13.

[0018] The flow channel 18 is a part of the circulation channel extending from the circulation opening 16. The first part of the circulation path extends in the flow channel 18, that is, between the end surface of the bracket 13 and the housing. The second part of the circulation path extends from the circumferential edge of the bracket 13 in the axial direction between the rotor 3 and the housing. Then, the circulation path leads to the circulation opening 16 around the axial end of the rotor 3 and between the rotor 3 and the stator 1.

[0019] Thus, in the electric motor shown, the circulation path starts from the circulation opening 16, extends between the housing and the rotor 3, around the end of the rotor 3 facing away from the end face and between the rotor 3 and the stator 1 back to the circulation opening 16. Thus, there is a gap with a thickness of less than 5 mm, such as a gap of 1 mm to 3 mm, between the flow guide rib 17 and the inner side of the housing facing the flow guide rib. For example, the height of the flow guide rib 17 can be 2 mm or more, for example 2 mm to 5 mm. In the embodiment example shown, the circulation opening 16 is located within 60% of the outer diameter of the bracket 3.

[0020] Combining air circulation inside the housing with liquid cooling of the 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 for improving the heat dissipation of the ambient air and on its inside for better absorption of heat from the air inside the housing. In the embodiment shown, the channel 10 for the cooling liquid is realized by an insert 15, which is inserted into the stator 1 and defines a section of the cooling channel together with the stator 1. Another section of the channel 10 is defined by a plate 19, which delimits a section of the cooling channel 10 between the plate and the insert 15 and between the plate and the housing part 7. However, the second housing part 7 can also be formed in one piece with the insert 15 and the plate 19.

[0021] Another section of the cooling channel 10 can be used for cooling electronic components 20 of the electronic control unit. A circuit board 21 of the control electronics is attached to the housing part 7 and is covered by a cover plate 22 .

[0022] List of Reference Numerals

[0023] 1 Stator

[0024] 2 stator winding

[0025] 3 rotors

[0026] 4 permanent magnets

[0027] 5-axis

[0028] 6 Shell part

[0029] 7 Shell part

[0030] 8 Washers

[0031] 9-axis seals

[0032] 10 channels

[0033] 11 Coolant inlet

[0034] 12 short circuit rings

[0035] 13 Bracket

[0036] 14 wheels

[0037] 15 Inserts

[0038] 16 loop opening

[0039] 17 Flow guiding ribs

[0040] 18 flow channels

[0041] 19 boards

[0042] 20Electronic components

[0043] 21 Printed Circuit Board

[0044] 22 Cover

[0045] 23 screws.

Claims

1. An electric motor, comprising: Axis (5), A stator (1), comprising a stator winding (2), a rotor (3) surrounding the stator (1) and comprising a back iron ring (12), a permanent magnet (4) arranged on the inner side of the back iron ring (12), and a bracket (13) connecting the back iron 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) protrudes, It is characterized in that The support (13) has a plurality of circulation openings (16) for air circulation and a plurality of flow guide ribs (17) in one end surface.

2. The electric motor according to claim 1, characterized in that The flow guiding ribs (17) each extend in a curved manner from an edge of the end surface extending in the circumferential direction to one of the circulation openings (16).

3. The electric motor according to claim 1, characterized in that The flow guiding ribs (17) are arranged in pairs, and a flow channel (18) is defined between the pair of flow guiding ribs (17).

4. The electric motor according to claim 1, characterized in that The housing comprises a first housing part (6) and a second housing part (7), between which an annular seal (8) is arranged.

5. The electric motor according to claim 4, characterized in that The first housing part (6) has an opening through which the shaft (5) protrudes, and the second housing part (7) has an inlet (11) and an outlet for a cooling liquid.

6. The electric motor according to claim 1, characterized in that The stator (1) surrounds an inner space in which channels (10) for a cooling liquid extend.

7. The electric motor according to claim 5, characterized in that The channel (10) for cooling liquid leads to an inner space surrounded by the stator (1) along one end of the end surface of the stator (1) facing away from the bracket (13).

8. The electric motor according to claim 1, characterized in that The housing has a pressure equalization opening which is closed by a gas-permeable membrane which is impermeable to liquid water.

9. The electric motor according to claim 1, characterized in that A circulation path extends from the circulation opening (16), the circulation path extending between the housing and the rotor (3), around an end of the rotor (3) facing away from the end surface and extending between the rotor (3) and the stator (1) to the circulation opening (16).

10. The electric motor according to claim 1, characterized in that There is a gap with a thickness of less than 5 mm between the flow guide rib (17) and the inner side of the housing facing the flow guide rib.

11. The electric motor according to claim 1, characterized in that The flow guiding rib (17) is directed at its inner end in the direction of rotation towards the circulation opening (16).

12. The electric motor according to claim 1, characterized in that The flow guiding rib (17) extends in a radial direction at its outer end.

13. The electric motor according to claim 1, characterized in that The housing has ribs on its exterior.

14. The electric motor according to claim 1, characterized in that The height of the flow guiding rib (17) is at least 2 mm.

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