Electric motor

Abstract

The invention describes an electric motor comprising a stator (1), a rotor (2) surrounding the stator (1), a shaft (3) non-rotatably connected to the rotor (2), and a housing (4, 5) surrounding the rotor (2) and the stator (1). The shaft (3) has a first end located within the housing (4, 5) and a second end projecting from the housing (4, 5). The rotor (2) has a short-circuit ring (9) and permanent magnets (8) attached to the inside of the short-circuit ring (9). According to the invention, the rotor (2) has a support (11) through which the short-circuit ring (8) is connected to the shaft (3) and through which the shaft (3) projects. The support (11) is arranged between the second end of the shaft (3) on the one hand and a floating bearing (13) and a fixed bearing (12) on the other.

Description

[0001] The invention relates to an electric motor comprising a stator, a stator surrounding the rotor, a shaft connected to the rotor, and a housing in which a first end of the shaft is arranged and from which a second end of the shaft projects. An electric motor with the features specified in the preamble of claim 1 is known from EP 3 091 637 B1.

[0002] External rotor motors with permanent magnets have mechanical advantages over internal rotor motors, especially since the permanent magnets are pressed against the rotor by centrifugal forces during operation and their mounting can therefore be designed more simply.

[0003] Electric motors in many applications, such as in vehicles, must be protected from environmental influences. In such applications, external rotor motors are advantageous, as one end of the shaft is located within the housing. This reduces the number of points through which environmental influences, particularly moisture, can penetrate and damage the electric motor.

[0004] In the electric motor known from EP 3 091 637 B1, the shaft is supported in the housing opening. The shaft is therefore only supported over a relatively short length and can thus tilt relatively easily.

[0005] The object of the present invention is to show a way in which the bearing of the shaft can be improved in electric motors of the type mentioned above.

[0006] This problem is solved by an electric motor having the features specified in claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

[0007] In an electric motor according to the invention, the rotor has a support via which the short-circuit ring is connected to the shaft and through which the shaft projects. The support is attached to the shaft between a first end of the shaft, which projects from the housing, and a floating bearing and a fixed bearing. The support thus enables the shaft to be supported at two points that are a considerable distance apart, making it difficult for the shaft to tilt.

[0008] A floating bearing, which is movable in the axial direction relative to the shaft, can compensate for manufacturing tolerances, while the fixed bearing can absorb axial forces and thus ensure a stable position of the shaft relative to the stator.

[0009] An advantageous embodiment of the invention provides that the fixed bearing is pressed against a stop by clamping segments. These clamping segments can be fixed by means of screws that protrude through them. The clamping segments can be separate components or extend as radial projections from a ring surrounding the shaft. Regardless of how these clamping segments are designed, the shaft can have a flange by which it is connected to the support, the flange projecting radially further outwards than an outer ring of the fixed bearing, and the flange having recesses through which the screws can be actuated during assembly. In this way, the fixed bearing can be axially fixed during assembly, even though the shaft has a flange that projects further outwards than the outer ring of the fixed bearing and the fixed bearing can only be accessed for assembly from one direction.The flange is therefore located in the housing between the housing opening and the fixed bearing.

[0010] Preferably, the fixed bearing is located between the flange and the floating bearing. This allows the shaft to be robustly constructed where it transmits torque from the rotor, and to be extended into the housing with minimal material usage to allow for a greater distance between the two bearings.

[0011] A further advantageous embodiment of the invention provides that the floating bearing is arranged at the first end of the shaft and that the floating bearing rests against an annular shoulder of the shaft on its side facing the fixed bearing, while the fixed bearing rests against another annular shoulder of the shaft on its side facing the second end of the shaft. Thus, the diameter of the shaft increases from the first end in at least two steps. Preferably, the shaft has a further section between the two bearings in which its diameter increases, for example, a conical section.

[0012] Further details and advantages of the invention are explained using an exemplary embodiment of the invention with reference to the accompanying drawings. These show: Fig. 1 an electric motor in a sectional view; Fig. 2 a detailed view of the electric motor with axial viewing direction with the housing part removed and without the support; Fig. 3 an oblique view to Fig. 2; and Fig. 4 a detailed view according to Fig. 2 without wave.

[0013] The in Fig. The electric motor shown in Figure 1 has a stator 1, a rotor 2 surrounding the stator 1, and a shaft 3 rigidly connected to the rotor 2. The stator 1 and rotor 2 are enclosed in a sealed housing comprising a first housing part 4, which forms a closed base on which the stator 1 sits, and a second housing part 5, which serves as a cover from which the shaft 3 protrudes. Thus, one end of the shaft 3 is located within the housing, and the other end is located outside the housing. The shaft 3 is supported by a fixed bearing 12 and a floating bearing 13. The bearings can be designed as rolling bearings, for example, ball bearings.

[0014] The stator 1 comprises a stack of laminations 6 and stator windings 8. The rotor 2 has a short-circuit ring 9, to the inside of which permanent magnets 10 are attached, and a support 11, via which the short-circuit ring 9 is connected to the shaft 3 and through which the shaft 3 projects. The support 11 is attached to a flange 24 of the shaft 3 between the end of the shaft 3 that projects from the housing and the bearings 12, 13. In other words, the flange 24 is located between the second end of the shaft 3, which is outside the housing, and the two bearings 12, 13.

[0015] The first housing part 5 has an inner part 5a that projects into the stator 1 and surrounds the two bearings 12, 13 in the circumferential direction. This inner part 5a can be hollow and contain a channel 14 for cooling water. For example, an insert 15 can be arranged in the hollow inner part 5a of the housing part 5, which together with the inner part 5a of the housing part 5 defines a channel 14. The insert 15 is covered by a cooling plate 31, which is attached to the first housing part 5, for example by welding, and thus fixes the insert 15 relative to the housing part 5. The first housing part 5 can carry control electronics on its side facing away from the shaft 3, with a circuit board 16 for supplying power to the stator windings 8, which is covered by a cover 18 attached to the first housing part 5, for example in the form of a plate.

[0016] In the illustrated embodiment, a further cooling channel section is formed between the cooling plate 31 and the insert 15, which contributes to cooling the control electronics. High-performance components of the control electronics can be arranged on the side of the circuit board facing the cooling plate 31 and, in particular, may be in contact with the cooling plate 31. For example, the cooling plate 31 can have projections, e.g., ribs or pins, on its side facing away from the control electronics, which extend into the further cooling channel section and improve the thermal coupling between the cooling plate 31 and the coolant in the further cooling channel section.

[0017] In the illustrated embodiment, the fixed bearing 12 is arranged between the floating bearing 13 and the flange 24 of the shaft 3, with which the support 11 is attached to the shaft 3. The floating bearing 13 is arranged at the first end of the shaft 3, i.e., at the end that lies within the housing. Fig. As shown in Figure 1, the shaft 3 forms a stop for an inner ring of the floating bearing 13, for example in the form of a ring shoulder. The floating bearing 13 can be pressed against this stop by a spring ring, which is supported against the housing part 5.

[0018] The fixed bearing 12 is pressed against a stop 23 by clamping segments 20, for example three or more clamping segments 20, through which the screws 22 protrude. The stop 23 is immovable relative to the stator 1 and is formed, for example, by the first housing part 5, in particular by its inner part 5a. The clamping segments 20 can be designed as separate components or as radially outwardly projecting projections extending from a ring surrounding the shaft 3. Such a ring can be integrated into an outer ring of the fixed bearing 12 or be designed as a separate ring that abuts the fixed bearing 12.

[0019] How in particular Fig. Figure 3 shows that the clamping segments 20 each lie in a groove which, in the illustrated embodiment, is formed in the inner part 5a of the housing part 5. The flange 24 of the shaft 3 can thus rotate over the clamping segments 20 and the screws 22 that fix these clamping segments 20.

[0020] As already mentioned, the shaft 3 has a flange 24, via which it is connected to the support 11, for example by means of screws 26. The flange 24 clearly projects radially further outwards than an outer ring of the fixed bearing 12 and the clamping segments 20, with which the fixed bearing 12 is pressed against its stop 23. As the Fig. 2 and Fig. As shown in Figure 3, the flange 24 has recesses through which action can be taken during assembly on the screws 22, which fix the clamping segments 20 that press the fixed bearing 12 against its stop 23. These recesses, through which action can be taken on the screws 22 during assembly, are formed as spaces between radially outwardly projecting projections 25 of the flange 24. The flange 24 can be bolted to the support 11 via these projections 25.

[0021] How Fig.As shown in Figure 1, the shaft 3 thickens between the floating bearing 13 and the fixed bearing 12. The diameter of the shaft 3 increases in several steps from its first end, which is located in the housing, to the flange 24. An initial increase in diameter results from the stop that the shaft 3 forms for the floating bearing 13. A further step-like increase in the diameter of the shaft 3 occurs at the fixed bearing, for which the shaft also forms a stop. Between the floating bearing 13 and the fixed bearing 12, the diameter of the shaft 3 can increase further, for example, in a conical section.

[0022] The two housing parts 4, 5 can be screwed together and press a seal 28 between them. The shaft 3 is held in a bushing 30 in the opening of the housing through which it protrudes, and the opening is sealed with a shaft seal 29. Reference symbol list 1 Stator 2 Rotor 3rd wave 4 Housing part 5 Housing part 5a Inner part 6 stacks of metal sheets 8 stator windings 9 Short-circuit ring 10 permanent magnets 11 carriers 12 fixed camps 13 Lotlager 14-channel 15 deployment 16 circuit board 18 lids 20 clamping segments 22 screws 23 attacks 24 flange 25 protrusions 26 screws 28 Seal 29 Shaft seal 30 socket 31 Cooling plate QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] EP 3 091 637 B1 [0001, 0004]

Claims

[1] Electric motor with a stator (1), a rotor (2) surrounding the stator (1), a shaft (3) connected to the rotor (2) in a rotationally fixed manner, and a housing (4, 5) surrounding the rotor (2) and the stator (1), wherein the shaft (3) has a first end arranged in the housing (4, 5) and a second end protruding from the housing (4, 5), and wherein the rotor (2) has a short-circuit ring (9) and permanent magnets (10) attached to the inside of the short-circuit ring (9), characterized by , that the rotor (2) has a carrier (11) via which the short-circuit ring (8) is connected to the shaft (3) and through which the shaft (3) projects, and the carrier (11) is fastened to the shaft (3) between the second end of the shaft (3) on the one hand and a loose bearing (13) and a fixed bearing (12) on the other hand. [2] Electric motor according to claim 1, characterized byClamping segments (20) which, together with screws (22) projecting through them, press the fixed bearing (12) against a stop (23), wherein the shaft has a flange (24) via which it is connected to the carrier (11), wherein the flange (24) projects radially further outwards than an outer ring of the fixed bearing (12), and the flange (24) has recesses through which the screws (22) can be acted upon during assembly. [3] Electric motor according to claim 2, characterized by that the clamping segments (20) are designed as radial projections which extend from a ring surrounding the shaft (3). n. [4] Electric motor according to claim 2 or 3, characterized by that the flange (24) has a plurality of radially outwardly projecting projections (25) between which the recesses are located. [5] Electric motor according to one of claims 2 to 4, characterized by that the flange (24) is screwed to the support (11). [6] Electric motor according to one of claims 2 to 5, characterized by that the clamping segments (20) lie in radially extending grooves of a housing part (5). [7] Electric motor according to one of the preceding claims, characterized by that the floating bearing (13) is arranged at the first end of the shaft (3) and the floating bearing (13) bears against an annular shoulder of the shaft (3) on its side facing the fixed bearing (12), and the fixed bearing (12) bears against a further annular shoulder of the shaft (3) on its side facing the second end of the shaft (3). [8] Electric motor according to one of the preceding claims, characterized by that the housing has a first housing part (5) which forms a closed bottom, and a second housing part (4) from which the shaft (3) projects, wherein the first housing part (5) has an inner part (5a) which projects into the stator (1) and surrounds both the fixed bearing (12) and the loose bearing (13) in the stator (1). [9] Electric motor according to claim 8, characterized by that the ring (21) is screwed to the first housing part (5). [10] Electric motor according to one of claims 8 or 9, characterized by that the first housing part (5) forms the stop (23) against which the fixed bearing (12) is pressed. [11] Electric motor according to one of the preceding claims, characterized by that the shaft (3) thickens between the loose bearing (13) and the fixed bearing (12).

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