Electric machine

Abstract

The present invention relates to an electric machine (1) comprising a rotor (2) with a rotor shaft (3) extending along an axial direction (100), a first bearing element (4), in particular a rolling bearing, and a second bearing element (5), in particular a rolling bearing, each provided for supporting the rotor shaft (3) on a bearing plate (13, 14) of the electric machine (1), wherein the first bearing element (4) is fixedly arranged in a first bearing receptacle (13a) of a first bearing plate (13) with respect to the axial direction (100), wherein the second bearing element (5) is slidably arranged in a second bearing receptacle (14a) of a second bearing plate (14) with respect to the axial direction (100) and is supported against the second bearing plate (14) by at least one elastic return element (7), in particular a return spring, characterized in thatthat the restoring element (7) is designed to apply an elastic restoring force to the second bearing element (5) along an effective direction (200), wherein the effective direction (200) has a predefined angle (α) greater than 0° and less than 90° relative to the axial direction (100) in order to generate both a prestress in the axial direction (100) and a prestress in a radial direction (300) oriented perpendicular to the axial direction (100).

Description

State of the art

[0001] The present invention relates to an electrical machine. In particular, the invention relates to an electrical machine in which concentricity is stabilized.

[0002] Electrical machines comprising a stator and a rotor are known from the prior art. The rotor has a rotor shaft that is rotatably mounted via bearings, often using a fixed-loose bearing arrangement. The loose bearing used in this case has a clearance fit relative to a bearing seat, allowing axial movement of the loose bearing. This allows the loose bearing to compensate for axial expansion of the rotor, thereby preventing stress in the bearings. The loose bearing is preloaded in the axial direction via a spring element. One such design is shown, for example, in DE 195 36 794 A1. Disclosure of the invention

[0003] The electric machine according to the invention exhibits reduced vibrations. Furthermore, a bearing support, in particular of the floating bearing, exhibits reduced wear. Particularly advantageously, wear is reduced on an outer ring of the floating bearing and / or a bearing seat of the floating bearing and / or on an outer ring of a preload element of the floating bearing. A steel bushing used in the prior art for the bearing seat of the floating bearing can be dispensed with.

[0004] The electric machine has a rotor with a rotor shaft, the rotor shaft extending along an axial direction. Furthermore, the electric machine has a first bearing element, in particular a rolling bearing, and a second bearing element, in particular a rolling bearing, each provided for supporting the rotor shaft on a respective bearing plate of the electric machine. Preferably, each bearing element is attached to its own bearing plate. The bearing plate can, in particular, also represent a pot-shaped housing part of the electric machine.

[0005] The first bearing element is arranged in a first bearing receptacle of a first bearing plate, fixed relative to the axial direction. The second bearing element is designed to be displaceable relative to the axial direction in a second bearing receptacle of a second bearing plate. This creates a fixed-loose bearing arrangement, with the first bearing element forming a fixed bearing and the second bearing element forming a loose bearing. This reduces or prevents undesirable axial distortion of the rotor shaft.

[0006] The second bearing element is supported relative to the second bearing plate via at least one elastic return element, in particular a return spring.

[0007] Furthermore, it is provided that the restoring element is designed to apply an elastic restoring force to the second bearing element along an effective direction, wherein the effective direction has a predefined angle greater than 0° and less than 90° with respect to the axial direction. In this way, the restoring force generates both a preload in the axial direction and a preload in a radial direction oriented perpendicular to the axial direction.

[0008] This results in preload of the second bearing element in two directions. For example, when the rotor shaft expands, the second bearing element can be displaced along the axial direction against an elastic restoring force of the restoring element. In addition, the preload in the radial direction causes the second bearing element to be pressed into the second bearing seat. This prevents or reduces an orbital movement, i.e. rotation, of the second bearing element, in particular an outer ring of the second bearing element, in the bearing seat, i.e. in the second bearing seat. An orbital movement of the second bearing element would lead to a shift in the center of gravity of the rotor, which in turn generates vibrations during operation of the electric machine. By avoiding or reducing such an orbital movement due to the preload in the radial direction, vibrations and wear are reduced or avoided.

[0009] The subclaims show preferred developments of the invention.

[0010] The second bearing element is preferably designed as a rolling bearing. The second bearing element has, in particular, an inner ring, an outer ring, and at least one rolling element between the inner ring and the outer ring. Preferably, a plurality of rolling elements is present between the inner ring and the outer ring. The rolling element is, for example, a ball. It is also preferably provided that either the inner ring bears against a projection of the rotor shaft and the restoring element is provided for applying the restoring force to the outer ring, or the outer ring bears against a projection of the rotor shaft and the restoring element is provided for applying the restoring force to the inner ring. The latter case is advantageous, for example, for hollow shafts. In the manner described, a loose bearing with the second bearing element is provided, wherein the second bearing element is preloaded by the restoring force of the restoring element.This achieves an optimal bearing arrangement, which on the one hand allows a firm and reliable bearing and on the other hand allows tolerance compensation of the rotor shaft.

[0011] In an advantageous embodiment, a wedge-shaped ring element is provided, which in particular bears against the inner ring or outer ring of the second bearing element with a first surface. With a second surface, the wedge-shaped ring element preferably bears against the return element. It is advantageously provided that the first surface and the second surface of the ring element have the predefined angle to one another. The wedge-shaped ring element thus preferably serves as an adapter between the return element and the inner ring or outer ring. Since the return element can be inclined both in the axial direction and in the radial direction relative to the central axis of the second bearing element to generate a force, the wedge-shaped ring element enables the compensation of this angular difference between the second bearing element and the return element.This ensures simple assembly and reliable operation of the second bearing element as a preloaded floating bearing. There are no special requirements regarding the shape of the second bearing element. It is only necessary to ensure that a force can be transmitted in the radial direction from the ring element to the outer ring, for example, by a material fit, a positive fit, and / or an adhesive fit. Ideally, a standard outer ring is sufficient as is, with only the ring element being adapted accordingly.

[0012] In a further advantageous embodiment, the inner ring or the outer ring of the second bearing element rests against the return element with a second surface. In this case, it is provided that the second surface of the second bearing element has the predefined angle to the axial direction. This again provides compensation between the effective direction of the return element and the central axis of the second bearing element. In contrast to a separate wedge-shaped ring element, no additional component is necessary. Only the corresponding ring of the second bearing element, i.e. the inner ring or the outer ring, needs to be formed with the corresponding second surface. This simplifies the assembly of the second bearing element, since in particular the number of components is minimized.

[0013] The second bearing support of the second bearing plate preferably has a counter surface against which the return element rests and which is configured substantially parallel to the second surface. As a result, only normal forces act between the surfaces of the second bearing support and the second bearing element, making the design of the electric machine very simple. Forces in the axial and radial directions are generated by the inclined position of the second surface with respect to the axial direction of the second bearing element, rather than a perpendicular arrangement.

[0014] Preferably, the outer ring of the second bearing element has a gap in the radial direction with the second bearing plate. As a result, the second bearing element is not fixed, but rather movable in the axial direction. This makes the second bearing element a floating bearing. Due to the preload due to the reset element, the second bearing element is preloaded in the axial direction on the one hand and in the radial direction on the other. This, in particular, impedes or prevents a circular movement of the outer ring in the gap.

[0015] In a preferred embodiment, a wedge ring arrangement with a first wedge ring and a second wedge ring is provided. The first wedge ring rests against the inner ring or outer ring of the second bearing element. The second wedge ring rests against the second bearing shield. The return element is arranged between the first wedge ring and the second wedge ring. By using the wedge ring arrangement, in particular, no requirements are placed on the second bearing element with regard to the shape of the contact surfaces. The shape of the second contact surface ensures that the outer ring can absorb the radial force. Ideally, the outer ring is designed so that this force transmission is ensured via a groove in the wedge ring. The wedge ring arrangement allows the return force to be applied to the second bearing element in the axial and radial directions.

[0016] Particularly advantageously, several individual springs distributed over the circumference of the wedge ring arrangement are provided as return elements. The individual springs are, in particular, spiral springs. It is provided that the individual springs are oriented along a respective central axis, wherein the central axes have the predefined angle to the axial direction. In particular, the central axes are oriented perpendicular to those surfaces of the wedge ring arrangement against which the individual springs rest. The individual springs are preferably arranged in a respective recess of the first wedge ring and / or the second wedge ring to enable reliable mounting of the individual springs.

[0017] In an alternative embodiment, the return element is particularly advantageously a wave spring or disc spring. The wave spring or disc spring is oriented along a spring axis, with the spring axis having a predefined angle to the axial direction. The wave spring or disc spring can advantageously be held and / or guided on the wedge rings by retaining elements and / or guide elements.

[0018] Preferably, it is also provided that the first wedge ring and the second wedge ring are arranged in a rotationally fixed manner relative to one another by means of an anti-rotation device. The anti-rotation device is, in particular, at least one pin. As a result, the two wedge rings are designed to be displaceable relative to one another only in order to apply the restoring force to the second bearing element via the restoring element.

[0019] Furthermore, it is preferably provided that the wedge ring arrangement has a positioning element. The positioning element is, in particular, a positioning pin. The positioning element allows the first wedge ring and / or the second wedge ring to be held in a predefined position relative to the second bearing plate. This prevents unwanted rotation of the first wedge ring and / or the second wedge ring, in particular of the wedge ring arrangement. This leads to reduced vibration of the electrical machine during operation and to reduced friction of the wedge ring arrangement against the bearing plate.

[0020] In a further preferred embodiment, the second wedge ring has a press fit with the second bearing receptacle of the second bearing plate. This press fit prevents or impedes unwanted rotation of the second wedge ring relative to the second bearing plate. Thus, in particular, rotation of the wedge ring arrangement in the second bearing receptacle is prevented or at least impeded. This leads to reduced vibration of the electrical machine during operation and to reduced friction between the wedge ring arrangement and the bearing plate. Short description of the drawing

[0021] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 is a schematic diagram of an electrical machine according to a first embodiment of the invention, Fig. 2 a schematic detailed view of a bearing of the rotor of the electric machine according to the first embodiment of the invention, Fig. 3 a schematic detailed view of a bearing arrangement for the rotor of an electrical machine according to a second embodiment, Fig. 4 a schematic detailed view of a bearing arrangement for the rotor of an electrical machine according to a third embodiment, and Fig. 5 a schematic detailed view of a bearing arrangement for the rotor of an electrical machine according to a fourth embodiment with press fit Embodiments of the invention

[0022] Fig. 1 schematically shows an illustration of an electric machine 1 according to a first exemplary embodiment of the invention. The electric machine 1 has a rotor 2 with a rotor shaft 3 extending along an axial direction 100. Furthermore, a first bearing plate 13 and a second bearing plate 14 are provided for supporting the rotor shaft 3. A first bearing element 4 serves to support the rotor shaft on the first bearing plate 13. For this purpose, the first bearing element 4 is arranged in a first bearing receptacle 13a of the first bearing plate 13, fixed with respect to the axial direction 100. The first bearing element 4 is a rolling bearing; in the exemplary embodiment shown, the first bearing element 4 is, for example, a ball bearing. The first bearing element 4 has an inner ring 4a, an outer ring 4b, and a plurality of rolling elements 4c, for example, balls. The first bearing element 4 forms a fixed bearing of a fixed-loose bearing arrangement for supporting the rotor shaft 3.

[0023] A second bearing element 5 serves to support the rotor shaft 3 on the second bearing plate 14. The second bearing element 5 is designed as a rolling bearing and has an inner ring 5a, an outer ring 5b, and at least one rolling element 5c between the inner ring 5a and the outer ring 5b. In the illustrated embodiment, the second bearing element 5 is a ball bearing. The second bearing element 5 is designed to be displaceable in a second bearing receptacle 14a of the second bearing plate 14 with respect to the axial direction 100. Thus, the second bearing element 5 forms a loose bearing of the fixed-loose bearing arrangement of the rotor shaft 3.

[0024] Fig. 2 is a schematic detailed view of a bearing of the rotor shaft 3 of the electric machine 1 according to the first embodiment of the invention by the second bearing element 5.

[0025] The second bearing element 5 is supported relative to the second bearing plate 14 via at least one elastic return element 7. This preloads the second bearing element 5, which would otherwise be loosely arranged in the second bearing receptacle 14a. The return element is, in particular, a return spring. In the illustrated embodiment, the inner ring 5a bears against a projection 3a of the rotor shaft 3, and the return element 7 is provided for applying the return force to the outer ring 5b.

[0026] The return element 7 is designed to apply an elastic restoring force to the second bearing element 5 along an effective direction 200. The effective direction 200 has a predefined angle α greater than 0° and less than 90° with respect to the axial direction 100 in order to generate both a preload in the axial direction 100 and a preload in a radial direction 300 oriented perpendicular to the axial direction 100. As a result, the outer ring 5b of the second bearing element 5 is pressed against the second bearing seat 14a in the radial direction 300. By designing the second bearing element 5 as a floating bearing, it is also provided that the outer ring 5b of the second bearing element 5 has a gap 12 with the second bearing plate 14 in the radial direction 300. The preload in the radial direction 300 by the return element 7 prevents or reduces a circular movement of the second bearing element 5 in this gap 12.As a result, on the one hand, vibration of the rotor 2 during operation of the electrical machine 1 is reduced or avoided, and on the other hand, wear of the second bearing plate 14 and / or second bearing element 5, in particular the outer ring 5b and the return element 7, is reduced or prevented.

[0027] In the first exemplary embodiment, the elastic restoring force is applied to the second bearing element 5 along the effective direction 200 by using a wedge-shaped ring element 8, which bears against the outer ring 5b of the second bearing element 5 with a first surface 8a. The wedge-shaped ring element 8 bears against the restoring element 7 with a second surface 8b. The first surface 8a and the second surface 8b of the ring element 8 have the predefined angle α to one another. In an alternative embodiment, the outer ring 5b of the second bearing element 5 could be specially adapted and bear directly against the restoring element 7 with a second surface 8b, in which case the second surface 8b of the second bearing element 5 has the predefined angle α to the axial direction 100. The use of the separate ring element 8, on the other hand, enables the use of commercially available rolling bearings, such as commercially available ball bearings.

[0028] Furthermore, it is provided that the second bearing receptacle 14a of the second bearing plate 14 has a counter surface 6 against which the return element 7 rests. The counter surface is formed essentially parallel to the second surface 8b. Thus, only normal forces act on the counter surface 6 and the second surface 8b. The design of the counter surface 6 and the second surface 8b, i.e. in particular their orientation, cause the normal direction of these surfaces to be the effective direction 200. Thus, the said preload of the second bearing element 5 occurs both in the axial direction 100 and in the radial direction 300. The wedge-shaped ring element 8 serves as an adapter between the return element 7 oriented along the effective direction and the outer ring 5b of the second bearing element 5, the outer surface of which has the axial direction 100 as the normal direction.

[0029] In the first embodiment, the second bearing receptacle 14a is adapted to the desired direction of action 200 of the elastic return element 7 by the specially adapted counter surface 6. In the second and third embodiments described below, a special adaptation of the second bearing receptacle 14a is omitted. This is achieved by a tapered ring arrangement 9. Fig. Figure 3 schematically shows a detailed view of a bearing assembly for the rotor 2 of an electric machine 1 according to the second embodiment of the invention. The basic structure is identical to the first embodiment; the difference lies primarily in the attachment of the return element 7, which in this embodiment is integrated into the said wedge ring assembly.

[0030] The wedge ring arrangement 9 has a first wedge ring 9a and a second wedge ring 9b, wherein the first wedge ring 9a bears against the outer ring 5b of the second bearing element 5. The second wedge ring 9b bears against the second bearing plate 14. The return element 7 is arranged between the first wedge ring 9a and the second wedge ring 9b. In this way, the return element 7 acts along an effective direction 200, which has the predefined angle α with respect to the axial direction 100. In the second exemplary embodiment, a plurality of individual springs 7a distributed over the circumference of the wedge ring arrangement 9 are provided as return elements 7. Each individual spring 7a is oriented along a respective central axis 400, wherein the central axes 400 have the predefined angle α with respect to the axial direction 100. The individual springs 7a are, in particular, spiral springs.

[0031] The use of the tapered ring arrangement 9 makes it possible, particularly in conventionally manufactured bearing shields, to provide preload for the second bearing element 5 in the axial direction 100 and the radial direction 300. Thus, in conventional designs, a return element is oriented along the axial direction and arranged between the second bearing element 5 and the second bearing receptacle 14a. This conventional return element can be replaced by the tapered ring arrangement 9 as described, in order to orient the elastic return force of the return element 7 or the individual springs 7a along the effective direction 200. This makes the design of the electrical machine simple and inexpensive.

[0032] As previously described, the outer ring 5b of the second bearing element 5 has the gap 12 to the second bearing plate 14 in the radial direction 300. A second gap 12a is present between the first wedge ring 9a and the second bearing plate 14, and a third gap 12b is present between the second wedge ring 9b and the bearing plate 14. In this exemplary embodiment, the wedge rings 9a, 9b are thus received in the second bearing receptacle 14a via a clearance fit. To prevent rotation of the wedge rings 9a, 9b relative to one another, the first wedge ring 9a and the second wedge ring 9b are arranged in a rotationally fixed manner relative to one another by an anti-rotation device 10. The anti-rotation device is in particular at least one pin, which engages, for example, both in a bore of the first wedge ring 9a and in a bore of the second wedge ring 9b. The wedge ring arrangement 9 also has a positioning element 11.The positioning element 11 is, in particular, a positioning pin. The positioning element 11 serves to hold the first tapered ring 9a and / or the second tapered ring 9b in a predefined position relative to the second bearing plate 14. This ensures that the effective direction 200 always corresponds to a previously desired and specified direction.

[0033] Fig. 4 schematically shows a detailed view of a bearing arrangement for the rotor 2 of an electrical machine 1 according to the third exemplary embodiment of the invention. The basic structure is identical to the second exemplary embodiment. In the third exemplary embodiment, however, instead of the individual springs 7a, the return element 7 is a corrugated spring 7b or disc spring. The corrugated spring 7b or disc spring is oriented along a spring axis 500, wherein the spring axis 500 has the predefined angle α to the axial direction 100. The corrugated spring 7b or disc spring is held and / or centered in particular by centering elements 16. Functionally, the third exemplary embodiment is identical to the second exemplary embodiment; only the type of generation of the elastic return force differs due to the different design of the return element 7.Also in the third embodiment, the anti-rotation device 10 and / or the positioning element 11 are preferably provided as described above.

[0034] Fig. Figure 5 schematically shows a detailed view of a bearing arrangement for the rotor 2 of an electric machine 1 according to the fourth exemplary embodiment of the invention. The basic structure is identical to the third exemplary embodiment. However, in the fourth exemplary embodiment, instead of the positioning element 11, a press fit 17 is provided between the second wedge ring 9b and the second bearing receptacle 14a, which fixes the second wedge ring 9b in the second bearing plate 14 in a rotationally secure manner. 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] DE 195 36 794 A1

[0002]

Claims

[1] Electrical machine (1) comprising a rotor (2) with a rotor shaft (3) extending along an axial direction (100), a first bearing element (4), in particular a rolling bearing, and a second bearing element (5), in particular a rolling bearing, each of which is provided for supporting the rotor shaft (3) on a bearing plate (13, 14) of the electrical machine (1), wherein the first bearing element (4) is arranged in a first bearing receptacle (13a) of a first bearing plate (13) in a fixed manner with respect to the axial direction (100), wherein the second bearing element (5) is designed to be displaceable in a second bearing receptacle (14a) of a second bearing plate (14) with respect to the axial direction (100) and is supported relative to the second bearing plate (14) via at least one elastic return element (7), in particular a return spring, characterized byin that the restoring element (7) is designed to apply an elastic restoring force to the second bearing element (5) along an effective direction (200), wherein the effective direction (200) has a predefined angle (α) greater than 0° and less than 90° with respect to the axial direction (100) in order to generate both a preload in the axial direction (100) and a preload in a radial direction (300) oriented perpendicular to the axial direction (100). [2] Electrical machine (1) according to claim 1, characterized byin that the second bearing element (5) is designed as a rolling bearing and has an inner ring (5a), an outer ring (5b) and at least one rolling element (5c) between the inner ring (5a) and the outer ring (5b), wherein either the inner ring (5a) bears against a projection (3a) of the rotor shaft (3) and the restoring element (7) is provided for applying the restoring force to the outer ring (5b) or the outer ring (5b) bears against a projection (3a) of the rotor shaft (3) and the restoring element (7) is provided for applying the restoring force to the inner ring (5a). [3] Electrical machine (1) according to claim 2, characterized by a wedge-shaped ring element (8) which bears with a first surface (8a) against the inner ring (5a) or outer ring (5b) of the second bearing element (5) and which bears with a second surface (8b) against the return element (7), wherein the first surface (8a) and the second surface (8b) of the ring element (8) have the predefined angle (α) to one another. [4] Electrical machine (1) according to claim 2, characterized by that the inner ring (5a) or the outer ring (5b) of the second bearing element (5) bears against the return element (7) with a second surface (8b), wherein the second surface (8b) of the second bearing element (5) has the predefined angle (α) to the axial direction (100). [5] Electrical machine according to claim 3 or 4, characterized by that the second bearing receptacle (14a) of the second bearing plate (14) has a counter surface (6) against which the return element (7) rests and which is formed substantially parallel to the second surface (8b). [6] Electrical machine (1) according to one of claims 2 to 5, characterized by that the outer ring (5b) of the second bearing element (5) has a gap (12) to the second bearing plate (14) in the radial direction (300). [7] Electrical machine (1) according to one of claims 2 to 6, characterized bya wedge ring arrangement (9) with a first wedge ring (9a) and a second wedge ring (9b), wherein the first wedge ring (9a) bears against the inner ring (5a) or outer ring (5b) of the second bearing element (5), wherein the second wedge ring (9b) bears against the second bearing plate (14), and wherein the return element (7) is arranged between the first wedge ring (9a) and the second wedge ring (9b). [8] Electrical machine (1) according to claim 7, characterized by that a plurality of individual springs (7a), in particular spiral springs, distributed over the circumference of the wedge ring arrangement (9) are provided as restoring elements (7), which are oriented along a respective central axis (400), wherein the central axes (400) have the predefined angle (α) to the axial direction (100). [9] Electrical machine (1) according to claim 7, characterized bythat the return element (7) is a corrugated spring (7b) which is oriented along a spring axis (500), wherein the spring axis (500) has the predefined angle (α) to the axial direction (100). [10] Electrical machine (1) according to one of claims 7 to 9, characterized by that the first wedge ring (9a) and the second wedge ring (9b) are secured against rotation relative to one another by an anti-rotation device (10), in particular by means of at least one pin. [11] Electrical machine (1) according to one of claims 7 to 10, characterized by that the wedge ring arrangement (9) has a positioning element (11), in particular a positioning pin, in order to hold the first wedge ring (9a) and / or the second wedge ring (9b) in a predefined position relative to the second bearing plate (14). [12] Electrical machine (1) according to one of claims 7 to 11, characterized bythat the second wedge ring (9b) has a press fit (17) to hold the wedge ring arrangement (9) in a predefined position relative to the second bearing plate (14).

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