Electric machine with insulated bearing seat

Abstract

The present invention relates to an electric machine (1) with a housing (2), which in particular comprises a bearing shield (2a), and a rotor (3) rotatable about a rotor axis (100), the rotor shaft (3a) comprising a rotor shaft rotatably mounted in at least one rotary bearing (4), wherein the respective rotary bearing (4) is arranged between a housing seat (5) of the housing (2) and a shaft seat (6) of the rotor shaft (3a) and has two bearing rings (7a, 7b), in particular an outer bearing ring (7a) and an inner bearing ring (7b), wherein a bearing bushing (8) is provided between a bearing ring (4a, 4b), in particular the outer bearing ring (4a), of the rotary bearing (4) and the housing seat (5), characterized in that an insulation gap (9) is provided between the bearing bushing (8) and the housing (2), in which an electrically insulating insulation ring (10) is arranged, in particular injected, to prevent or reduce bearing currents.

Description

State of the art

[0001] The present invention relates to an electric machine. The electric machine has at least one electrically insulated bearing seat on which a rotor shaft can be mounted.

[0002] Insulation measures to prevent bearing current are known from the prior art. Such measures are usually implemented on the bearings of a rotor shaft to protect the bearings, in particular to prevent electrical discharges within the bearing. For example, hybrid bearings are used, which are typically more expensive than conventional bearings. Alternatively, plastic overmolding can be applied to the bearings. An example of insulation is shown in CN 103023190 B. Disclosure of the invention

[0003] The electric machine according to the invention features effective protection against electrical bearing currents, and conventional steel bearings can be used. The use of more expensive hybrid bearings with integrated electrical insulation is unnecessary. The insulation is located outside the mechanical interfaces and is therefore robust; in particular, the thermomechanical properties and wear protection functions of the interface between the bearing and the bearing seat are not affected. Electrical bearing currents flow via the bearings to the housing seat, which represents the mass. By inserting, in particular by injection molding, a plastic bushing into the housing, the current path within the housing is interrupted.

[0004] The electric machine comprises a housing and a rotor rotatable about a rotor axis. The housing includes, in particular, a bearing shield. Alternatively or additionally, the housing preferably includes a housing pot. For example, a housing pot and a bearing shield are provided on the one hand. In another example, the housing has a hollow cylindrical section, at each of the end faces of which a bearing shield is arranged. The rotor includes, in particular, a rotor shaft which is rotatably mounted in at least one rotary bearing.

[0005] The rotary bearing is arranged between a housing seat and a shaft seat on the rotor shaft. The housing seat is formed, in particular, on the bearing shield, or alternatively, on the housing cup. The rotary bearing also has two bearing rings, specifically an outer bearing ring and an inner bearing ring. The outer bearing ring is advantageously not electrically insulated from the inner bearing ring. The bearing rings are made, in particular, of an electrically conductive material, for example, steel. A bearing bushing is provided between a bearing ring, preferably the outer bearing ring, of the rotary bearing and the housing seat. The bearing bushing is preferably rigidly connected to the housing.

[0006] An insulating gap is provided between the bearing bushing and the housing, primarily for electrical insulation. An electrically insulating ring is arranged within this gap to prevent or reduce bearing currents. Particularly advantageously, the insulating ring is injection-molded into the gap. This achieves electrical insulation of the rotor shaft from the housing, minimizing or eliminating the risk of bearing damage from bearing currents.

[0007] In an advantageous embodiment, the insulating ring has a wall thickness in the range of 0.1 mm to 3 mm, particularly between 0.5 mm and 2 mm. This ensures optimal electrical insulation. Furthermore, the insulating ring is robustly designed and can optimally transfer bearing forces from the bearing to the housing.

[0008] The insulating ring also advantageously serves to hold and position the bearing bushing. This allows for optimal alignment of the bearing bushing, compensating for tolerances in the housing seat. This simplifies housing manufacturing, particularly allowing for larger tolerances. Positioning the bearing bushing relative to the housing is simple and reliable thanks to the insulating ring, especially when it is injection-molded into the insulating gap.

[0009] The dependent claims describe preferred embodiments of the invention.

[0010] Preferably, the insulation gap for forming the insulation ring is filled with a hardened molding compound. This molding compound is, in particular, a thermoset. This makes manufacturing the insulation ring simple and cost-effective. The molding compound can be applied directly into the insulation gap, where it hardens within the gap. This allows for optimal compensation of tolerances between the housing seat and the bearing bushing.

[0011] Advantageously, the insulating ring is positively connected to the housing seat and / or the bearing bushing. This positive connection acts as an anti-rotation device in the circumferential direction and / or as protection against displacement in the axial direction. To create this positive connection, the bearing bushing, which is preferably a steel ring, has at least one recess on its outer circumference facing the housing. This recess is, in particular, a flat or groove. In this way, a positive connection between the bearing bushing and the molded insulating ring can be established simply and reliably. At least one projection or recess is formed on the circumferential wall of the housing seat. This allows for undercuts or engagements between the respective components, resulting in high stability of the assembly.

[0012] Preferably, the insulating ring electrically isolates the bearing bushing from the housing. Electrical isolation with respect to high-frequency bearing currents is particularly advantageous. The bearing bushing is therefore electrically isolated from the housing, so that there is no electrical connection between the rotor shaft and the housing through the bearing.

[0013] The insulating ring establishes a distance between the bearing bushing and the housing, particularly at the circumference of the bushing and at the end face of the bushing facing the housing. By adjusting this distance, the bearing bushing is precisely positioned, ensuring optimal support for the rotor shaft. Only minimal accuracy requirements are placed on the housing seat, as the insulating ring compensates for any discrepancies.

[0014] The insulating ring preferably has an annular circumferential section. Furthermore, the insulating ring particularly preferably has an annular shoulder section projecting radially inwards from the circumferential section. The shoulder section serves to electrically insulate the bearing bushing in the axial direction. In addition, the shoulder section preferably serves to fix the position of the bearing bushing in the axial direction.

[0015] The insulating ring is preferably L-shaped or hollow cylindrical in cross-section. The L-shape allows for partial engagement of the bearing bushing, enabling the insulating ring to act not only radially but also axially. The insulating ring's effect is understood to be, in particular, an insulating effect and / or a spacer effect between the housing and the bearing bushing.

[0016] The housing contains at least one injection port. This injection port is designed for injecting the molding compound for the insulating ring. This allows the insulating ring to be produced directly within the housing. Advantageously, the bearing bushing is positioned relative to the housing by a tool, with the tool, bearing bushing, and housing forming the insulating gap. The insulating gap can then be filled with the molding compound through the injection port to create the insulating ring. After injection, the injection port preferably serves as a holder for the insulating ring, as the ring engages with the injection port after the molding compound has hardened.

[0017] The bearing bushing has a bushing seat for the outer race of the rotary bearing. The housing seat and the bushing seat of the bearing bushing are preferably arranged concentrically. In particular, the bushing seat serves solely for insulation from the housing, with the insulating ring positioned between the housing and the bearing bushing. Advantageously, the bushing seat also serves for fine adjustment of the rotor shaft bearing, with the bearing seat providing coarse adjustment. Compensation is achieved via the molding compound between the housing and the bearing bushing.

[0018] In a further advantageous embodiment, an electrically insulating insert is provided. This insert serves, in particular, for the axial positioning of the bearing bushing. For this purpose, the insert is arranged axially between the housing seat and the bearing bushing. It is particularly advantageous for the insert to be made of an elastically deformable material, for example, an elastomer. If axial pressure is applied to the bearing bushing before the insulating ring is inserted or injected, the counter-pressure from the elastically deformable insert allows for highly precise positioning of the bearing bushing. Fixation is then preferably achieved by means of the insulating ring, which is particularly preferably injected into the insulating gap as described.

[0019] Preferably, the rotary bearing is one that faces away from the output side of the electric machine. This ensures that the bearing most at risk of damage from electrical bearing currents is electrically insulated. Brief description of the drawings

[0020] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows: Fig. 1 a schematic illustration of an electrical machine according to an embodiment of the invention, and Fig. 2 A schematic detail view of the electrical machine according to the embodiment of the invention. Embodiments of the invention

[0021] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0022] Fig. Figure 1 schematically shows an electric machine 1 according to an embodiment of the invention. The electric machine 1 has a housing 2 to which a stator 10 of the electric machine 1 is attached. The housing 2 also has at least one bearing shield 2a; in the embodiment shown, two bearing shields 2a are provided. A rotor shaft 3a of a rotor 3 of the electric machine is mounted on the bearing shields 2a. The rotor shaft 3a is rotatably mounted by means of a rotary bearing 4 such that it can rotate about a rotor axis 100. One end of the rotor shaft 3a can be coupled to other components that are to be driven by the electric machine 1, thereby defining an output side 12 of the electric machine 1. The rotary bearing 4 that faces away from the output side 12 of the electric machine 1 is described below.However, a suitably designed rotary bearing 4 can also be provided on the side facing the output side 12, or the electric machine 1 may have an output at both ends of the rotor shaft 3a.

[0023] The rotary bearing 4 is arranged between a housing seat 5 of the housing 2 and a shaft seat 6 of the rotor shaft 3a. The housing seat 5 serves to receive a bearing bushing 8. The bearing bushing 8 is spaced apart from the housing 2, so that an insulation gap 7 is formed between the bearing bushing 8 and the housing 2. An electrically insulating insulating ring 9 is arranged in the insulation gap 7.

[0024] The rotary bearing 4 has two bearing rings 4a and 4b: an outer bearing ring 4a and an inner bearing ring 4b. Rolling elements such as balls, rollers, or cones are arranged between the outer bearing ring 4a and the inner bearing ring 4b. The outer bearing ring 4a is arranged on the bearing bushing 8, so that there is direct contact between the bearing bushing 8 and the outer bearing ring 4a. In this way, the bearing bushing 8 is positioned between the outer bearing ring 4a of the rotary bearing 4 and the housing seat 5. The bushing seat 11 of the bearing bushing 8 is designed for the outer bearing ring 4a of the rotary bearing 4, with the housing seat 5 of the housing 2 and the bushing seat 11 of the bearing bushing 8 being arranged concentrically.

[0025] The insulating ring 9 is preferably injected into the insulating gap 7. For example, the insulating ring 9 has a wall thickness between 0.1 mm and 3 mm, particularly between 0.5 and 2 mm. The insulating ring 9 advantageously serves to position the bearing bushing 8 relative to the housing seat 5. Thus, the tolerance required for the outer bearing ring 4a is achieved solely by the bearing bushing 8, while the housing seat 5 can have larger tolerances, which are compensated for by the insulating ring 9. This simplifies the manufacture of the housing 2, and in particular the bearing shield 2a.

[0026] The insulating ring 9 establishes a distance between the bearing bushing 8 and the housing 2, particularly the bearing shield 2a, at a circumference 8a of the bearing bushing 8 and at an end face 8b of the bearing bushing 8 facing the housing 2. The bearing bushing 8 can, for example, have an L-shaped or rectangular cross-section. By adjusting the distance to the housing 2 using the insulating ring 9, the bearing bushing 8 is positioned relative to the housing seat 5.

[0027] The insulating ring 9 has an annular circumferential section 9a and an annular shoulder section 9b projecting radially inwards from the circumferential section 9a. Therefore, the insulating ring 9 has an L-shaped cross-section. Alternatively, the insulating ring can also be hollow cylindrical and thus have a rectangular cross-section. Due to the shape of the circumferential section 9a and the shoulder section 9b, the insulating ring 9 separates the bearing bushing 8 from the housing 2 in both the axial and radial directions.

[0028] The insulation gap 7 and the insulation ring 9 arranged therein provide electrical insulation between the housing 2 and the rotary bearing 4. This serves to prevent or reduce bearing currents. In particular, the insulation ring 9 electrically insulates the bearing bushing 8 from the housing 2, especially with regard to high-frequency bearing currents. Because the bearing bushing 8 is insulated, the rotary bearing 4 itself does not require electrical insulation. Therefore, the rotary bearing 4 can be designed simply and cost-effectively. The electrical insulation reduces or eliminates the risk of bearing damage and load transmission through the rotary bearing 4.

[0029] The insulating ring 9 is preferably manufactured directly in the housing 2. For this purpose, the insulating ring 9 is injected into the insulating gap 7. In this way, the insulating gap 7 is filled with a hardened molding compound to form the insulating ring 9. The molding compound is, for example, a thermoset. The housing 2 has, as shown in Fig.Figure 2 schematically shows at least one injection port 2b for injecting the molding compound of the insulating ring 9. To manufacture the insulating ring 9, the bearing bushing 8 is held, for example, against a tool that positions the bearing bushing 8 relative to the housing 2 and also seals the insulation gap 7. The molding compound can then be injected through the injection port 2b to fill the insulation gap 7. After the molding compound has hardened, the bearing bushing 8 is positioned and held relative to the housing seat 5, and electrical insulation is formed between the housing 2 and the bearing bushing 8. The assembly of the outer bearing ring 4a onto the bearing bushing 8 does not affect this insulation; in particular, the risk of damaging the insulation during the assembly of the rotary bearing 4 is avoided.

[0030] For optimal retention of the bearing bushing 8 and housing 2, the insulating ring 9 is designed to be positively connected to the housing seat 5 and / or to the bearing bushing 8. This positive connection can be easily achieved by injecting the molding compound and subsequently curing it, as only corresponding undercuts and / or projections and / or recesses need to be provided on the bearing bushing 8 and / or the housing seat 5. The positive connection is formed by inserting the molding compound into the insulating gap 7. 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] CN 103023190

[0002]

Claims

[1] Electric machine (1) with a housing (2), which in particular includes a bearing shield (2a), and a rotor (3) rotatable about a rotor axis (100), which includes a rotor shaft (3a) rotatably mounted in at least one rotary bearing (4), wherein the respective rotary bearing (4) is arranged between a housing seat (5) of the housing (2) and a shaft seat (6) of the rotor shaft (3a) and has two bearing rings (4a, 4b), in particular an outer bearing ring (4a) and an inner bearing ring (4b), wherein a bearing bushing (8) is provided between a bearing ring (4a, 4b), in particular the outer bearing ring (4a), of the rotary bearing (4) and the housing seat (5), characterized by , that an insulation gap (7) is provided between the bearing bushing (8) and the housing (2), in which an electrically insulating insulating ring (9) is arranged, in particular injected, to prevent or reduce bearing currents. [2] Electric machine (1) according to claim 1, characterized by, that the insulation gap (7) is filled with a hardened molding compound, in particular a thermoset, to form the insulation ring (9). [3] Electric machine (1) according to any one of the preceding claims, characterized by , that the insulating ring (9) is positively connected to the housing seat (5) and / or to the bearing bushing (8). [4] Electric machine (1) according to any one of the preceding claims, characterized by , that the insulating ring (9) electrically insulates the bearing bushing (8) from the housing (2), especially with regard to high-frequency bearing currents. [5] Electric machine (1) according to any one of the preceding claims, characterized by , that the insulating ring (9) is on the circumference (8a) and in particular, a distance is set to the housing (2) at an end face (8b) of the bearing bushing (8) facing the housing (2). [6] Electric machine (1) according to any one of the preceding claims, characterized by, that the insulation ring (9) has an annular circumferential section (9a) and in particular an annular shoulder section (9b) projecting radially inwards from the circumferential section (9a). [7] Electric machine (1) according to any one of the preceding claims, characterized by that the insulating ring (9) has an L-shaped or hollow cylindrical cross-section. [8] Electric machine (1) according to any one of the preceding claims, characterized by , that at least one injection opening (2b) is provided in the housing (2) for injecting the molding compound of the insulating ring. [9] Electric machine (1) according to any one of the preceding claims, characterized by , that the bearing bushing (8) has a bushing seat (11) for the outer bearing ring (4a) of the rotary bearing (4), wherein the housing seat (5) of the housing (2) and the bushing seat (11) of the bearing bushing (8) are arranged concentrically. [10] Electric machine (1) according to any one of the preceding claims, characterized by , that the rotary bearing (4) is a bearing that is facing away from an output side (12) of the electric machine (1).

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