DE102020127410A1 - electric motor - Google Patents

Abstract

The present invention relates to an electric motor (1), designed as a three-phase asynchronous machine, comprising a cylindrical motor housing (2) which has a cooling jacket (4) in its ring-cylindrical housing wall (3), over which a cooling jacket (4) is mounted on the inside of the housing wall ( 3) the stationarily arranged annular-cylindrical stator (5) can be cooled, the annular-cylindrical stator (5) having a winding overhang (8) on its two end ring surfaces (6, 7); a rotor shaft (9) which is rotatably mounted in the motor housing (2) via at least two roller bearings (10, 11), a squirrel-cage rotor (12) being arranged in a rotationally fixed manner on the rotor shaft (9) and having a large number of laminated cores (13 ) connected rotor laminations (14) and hollow-shaped rotor bars (15) arranged parallel to the rotor shaft (9) which are electrically conductively connected to each other at the end faces via a short-circuit ring (16, 17), wherein on the first end-side short-circuit ring (16) a first end plate (18) and a second end plate (19) is arranged on the second end-side short-circuit ring (17), the two end plates (18, 19) comprising cooling channels (20, 21) via which a coolant can flow to the rotor bars (15) is conductive.

Description

The present invention relates to an electric motor which is designed as a three-phase asynchronous machine. The electric motor comprises a cylindrical motor housing, which has a cooling jacket in its ring-cylindrical housing wall, via which a ring-cylindrical stator arranged stationary on the inside of the housing wall can be cooled, the ring-cylindrical stator having a winding overhang on its two end ring surfaces. Furthermore, the electric motor comprises a rotor shaft, which is rotatably mounted in the motor housing via at least two roller bearings, with a squirrel-cage rotor being arranged in a rotationally fixed manner on the rotor shaft, which has a large number of rotor laminations connected to form laminated cores and hollow rotor bars arranged parallel to the rotor shaft, which are on the front side are electrically conductively connected to each other via a short-circuit ring.

Due to their high power density, today's high-performance traction machines for electric vehicles generate several KW of waste heat, which must be safely dissipated. Otherwise, the performance must be reduced during operation so that the e-machines are not damaged. Since these e-machines are to be built more and more compactly (due to space and material savings) and thus the power density continues to increase as a result, they are also increasingly being operated with higher power. In order for this to be possible over the long term, the waste heat must be dissipated using additional auxiliary equipment.

From the DE 101 42 642 A1 an air-cooled electric motor in the form of a linear motor is known, in which a module block consisting of a winding body and windings applied thereto is contained in a closed housing. Cooling air is introduced into the housing via an air inlet, where it flows around the windings and is directed into tooth gaps in the winding body in the area of the windings.

In the DE 10 2018 101 078 A1 an apparatus for cooling an electric motor is disclosed. The electric motor has a rotor and a stator. The stator is surrounded by a stator housing in which a cooling circuit for the stator is formed.

The rotor sits on a rotor shaft and the rotor shaft is rotatably mounted in the end shield via at least one roller bearing. At least one cooling circuit for the rotor is formed in the rotor shaft. A heat exchanger couples the cooling circuit for the rotor and the cooling circuit for the stator.

In asynchronous machines, the magnetic field in the rotor is generated by inducing a voltage in the rotor bars, which in turn generates a current. Since the bars are short-circuited at both ends and the length of the bars, unlike coils, is very short and thus the resistance is very low, a large current is induced in the bars. This causes the rods to heat up and the resistance increases, generating even more heat. Above all when starting up asynchronous machines, they have a poor degree of efficiency and heat up considerably due to the high currents that occur.

Against this background, the object of the present invention is to provide an electric motor that is improved over the prior art.

This object is achieved with an electric motor according to the features of independent claim 1.

The electric motor according to the invention is designed as a three-phase asynchronous machine and comprises a cylindrical motor housing, which has a cooling jacket in its ring-cylindrical housing wall, via which a ring-cylindrical stator arranged stationary on the inside of the housing wall can be cooled, the ring-cylindrical stator being at both of its end ring surfaces has a winding head. Furthermore, the electric motor comprises a rotor shaft, which is rotatably mounted in the motor housing via at least two roller bearings, with a squirrel-cage rotor being arranged in a rotationally fixed manner on the rotor shaft, which has a large number of rotor laminations connected to form laminated cores and hollow rotor bars arranged parallel to the rotor shaft, which are on the front side are electrically conductively connected to each other via a short-circuit ring.

The electric motor is characterized in that a first end plate is arranged on the first end-side short-circuit ring and a second end plate is arranged on the second end-side short-circuit ring, with the two end plates comprising cooling channels via which a coolant can be routed to the rotor bars.

Because the coolant can flow directly through the rotor bars, the rotor bars and thus the entire rotor can be actively cooled during operation. This avoids excessive heating and thus an increase in the resistances in the rotor bars, so that the electric machines not only have a higher Performance can be operated continuously, but also has a higher efficiency.

Further advantageous refinements of the invention are specified in the dependently formulated claims. The features listed individually in the dependent claims can be combined with one another in a technologically meaningful manner and can define further refinements of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, with further preferred configurations of the invention being presented.

In a particularly advantageous embodiment, it is provided that the cooling channels have openings distributed over the circumference, via which the winding overhangs can be cooled with the coolant. The active cooling of the end windings with the coolant via the rotor allows a particularly effective heat dissipation from the inside of the stator. In this way, overheating can be effectively avoided and the e-machine can be operated permanently with a higher output.

The rotor shaft preferably has at least one radial first coolant inlet bore arranged outside the motor housing and at least one radial second coolant inlet bore arranged inside the motor housing, which is fluidically connected to the cooling channels of the first end plate. In this context, it is particularly preferred that the rotor shaft comprises at least one radial first coolant outlet borehole arranged inside the motor housing, which is fluidically connected to the cooling channels of the second end plate and which is connected via a sleeve arranged inside the rotor shaft to a radial second coolant outlet borehole arranged outside the rotor shaft is fluidly connected, such that the coolant is conductive in the circuit through the rotor bars.

Such a structure is advantageous in that the cooling can be adjusted as needed via the volume flow and does not have to be operated continuously. Another advantage is that the heat is dissipated exactly where it is generated. This means that the entire rotor, including the laminated core, does not heat up any further. This also has an advantageous effect on the roller bearings, since there can be no temperature difference between the inner and outer ring. On the one hand, this reduces the costs for the roller bearings and, on the other hand, enables a more even bearing clearance at all operating points of the e-machine.

A minimum quantity for cooling the winding overhangs can be set via the diameter and the number of openings distributed over the circumference. The advantage here is that only a low coolant supply pressure is required, which reduces the required coolant pump capacity. The coolant is thrown outwards by centrifugal force and is thus evenly distributed on the winding heads. If a higher cooling capacity is required, the coolant supply pressure can be increased as required in order to increase the coolant volume flow for cooling the rotor and the end windings.

Furthermore, the temperature of hotspots generated in the center of the stator can be effectively lowered. Here the cooled rotor can absorb the heat from the stator. Since this solution additionally cools the stator over its entire length, the e-machine can also be operated permanently with a higher output.

Furthermore, it is advantageously provided that the radial first coolant inlet bore and the radial second coolant outlet bore are arranged axially on one side of the rotor shaft.

• 1 eine Ausführungsvariante des erfindungsgemäßen Elektromotors in einer Schnittdarstellung, und
• 2 einen vergrößerten Bereich des in 1 gezeigten Elektromotors.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be pointed out that the invention should not be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. The same reference symbols designate the same objects, so that explanations from other figures can be used as a supplement if necessary. Show it:

• 1 an embodiment of the electric motor according to the invention in a sectional view, and
• 2 an enlarged area of the in 1 shown electric motor.

In 1 an embodiment variant of the electric motor 1 according to the invention is shown, which is designed as a three-phase asynchronous machine. The electric motor 1 comprises a cylindrical motor housing 2 which has a cooling jacket 4 in its ring-cylindrical housing wall 3 . A stator 5 which is stationary on the inside of the housing wall 3 and is of ring-cylindrical design can be cooled via the cooling jacket 4 .

The stator 5 can be formed, for example, from a large number of laminations and windings (not shown). Once again 1 can be removed, the ring-cylindrical stator 5 has a winding head 8 on each of its two end ring surfaces 6, 7.

Furthermore, the electric motor 1 comprises a rotor shaft 9 which is rotatably mounted in the motor housing 2 via at least two roller bearings 10, 11. A squirrel-cage rotor 12 is arranged in a rotationally fixed manner on the rotor shaft 9, which has a large number of rotor laminations 14 connected to form laminated cores 13 and hollow-shaped rotor bars 15 arranged parallel to the rotor shaft 9, which are electrically conductively connected to one another on the front side via a short-circuit ring 16, 17 in each case.

A first end plate 18 is arranged on the first short-circuit ring 16 on the end face, and a second end plate 19 is arranged on the second short-circuit ring 17 on the end face. Each of the two end plates 18, 19 includes cooling ducts 20, 21, via which a coolant can be routed to the rotor bars 15, as can be seen in particular using the arrows in 2 is recognizable.

In the embodiment variant shown here, the cooling channels 20, 21 have openings 22, 23 distributed over the circumference, via which the winding overhangs 8 can be cooled directly with the coolant, so that overheating can be effectively avoided.

In order to be able to set the cooling as needed via the volume flow, the electric motor 1 has a cooling circuit 24, which in 2 is represented by the arrows. For this purpose, the rotor shaft 9 has a radial first coolant inlet bore 25 arranged outside the motor housing 2 and a radial second coolant inlet bore 26 arranged inside the motor housing 2 , which is fluidically connected to the cooling channels 20 of the first end plate 18 . Furthermore, the rotor shaft 9 has a radial first coolant outlet bore 27 arranged inside the motor housing 2, which is fluidically connected to the cooling channels 21 of the second end plate 19 and which, via a sleeve 28 arranged inside the rotor shaft 9, has a radial second coolant outlet bore arranged outside the rotor shaft 9 29 is fluidically connected so that the coolant can be circulated through the rotor bars 15, as indicated by the arrows in 2 is recognizable.

The invention is not limited to the combinations of features defined in the independent claims, but can also be defined by any other combination of specific features of all the individual features disclosed overall. This means that in principle practically every individual feature of the independent claims can be omitted or replaced by at least one individual feature disclosed elsewhere in the application. In this respect, the independent claim is to be understood merely as a first attempt at formulating the present invention.

Reference List

1

electric motor

2

motor housing

3

housing wall

4

cooling jacket

5

stator

6

front ring surface

7

front ring surface

8th

winding head

9

rotor shaft

10

roller bearing

11

roller bearing

12

squirrel cage runner

13

laminated core

14

rotor laminations

15

runner rods

16

short ring

17

short ring

18

first end plate

19

second end plate

20

cooling channels

21

cooling channels

22

openings

23

openings

24

cooling circuit

25

first coolant inlet hole

26

second coolant inlet hole

27

first coolant outlet hole

28

sleeve

29

second coolant outlet hole

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 10142642 A1 [0003]
• DE 102018101078 A1 [0004]

Claims (5)

Electric motor (1), designed as a three-phase asynchronous machine, comprising a cylindrically designed motor housing (2) which has a cooling jacket (4) in its ring-cylindrical housing wall (3), over which a ring-cylindrical formed stator (5) can be cooled, wherein the ring-cylindrical formed stator (5) has a winding overhang (8) on its two end ring surfaces (6, 7); a rotor shaft (9) which is rotatably mounted in the motor housing (2) via at least two roller bearings (10, 11), a squirrel-cage rotor (12) being arranged in a rotationally fixed manner on the rotor shaft (9) and having a large number of laminated cores (13 ) connected rotor laminations (14) and arranged parallel to the rotor shaft (9), hollow-shaped rotor bars (15) which are electrically conductively connected to each other on the front side via a respective short-circuit ring (16, 17), characterized in that on the first short-circuit ring on the front side ( 16) a first end plate (18) and a second end plate (19) is arranged on the second short-circuit ring (17) on the end face, the two end plates (18, 19) comprising cooling channels (20, 21) via which a coolant can flow to the rotor bars (15) is conductive. Electric motor (1) after claim 1 , wherein the cooling channels (20, 21) have openings (22, 23) distributed over the circumference, via which the winding overhangs (8) can be cooled with the coolant. Electric motor (1) after claim 1 or 2 , wherein the rotor shaft (9) comprises at least one radial first coolant inlet bore (25) arranged outside the motor housing (3) and at least one radial second coolant inlet bore (26) arranged inside the motor housing (2), which is connected to the cooling channels (20) of the first end plate (18) is fluidically connected. Electric motor (1) after claim 3 , wherein the rotor shaft (9) comprises at least one radial first coolant outlet bore (27) arranged inside the motor housing (2), which is fluidically connected to the cooling channels (21) of the second end plate (19) and which is connected via a hole inside the rotor shaft (9) arranged sleeve (28) is fluidically connected to a radial second coolant outlet bore (29) arranged outside of the rotor shaft (9), in such a way that the coolant can be guided in the circuit through the rotor bars (15). Electric motor (1) after claim 3 or 4 , wherein the radial first coolant inlet bore (25) and the radial second coolant outlet bore (29) are arranged axially on one side of the rotor shaft (9).

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