Rotor shaft of a rotor of an electric machine, rotor, and electric machine

Abstract

The invention relates to a rotor shaft of a rotor of an electric machine, comprising a shaft component (3) on which a toothing portion (7) having an external toothing (8) is directly formed and on which a first and a second, in each case radial, rolling element raceway (9, 10) are directly formed axially adjacent to the toothing portion (7), wherein: the toothing portion (7) is provided axially between the first and the second rolling element raceway (9, 10); an annular first rolling bearing (11) comprising first rolling elements (16) guided in a first cage (15) is seated on the first rolling element raceway (9), said first rolling elements rolling directly on the first rolling element raceway (9), and an annular second rolling bearing (13) comprising second rolling elements (18) guided in a second cage (17) is seated on the second rolling element raceway (10), said second rolling elements rolling directly on the second rolling element raceway (10); the diameter (dH1) of an envelope circle of the first rolling elements (16) is less than the diameter (dF) of a root circle of the external toothing (8); and the diameter (dH2) of an envelope circle of the second rolling elements (18) is greater than the diameter (dK) of a tip circle of the external toothing (8).

Description

[0001] Rotor shaft of a rotor of an electrical machine, rotor and electrical machine

[0002] The invention relates to a rotor shaft of a rotor of an electrical machine.

[0003] A rotor shaft is known to be part of the rotor of an electrical machine, as described, for example, in DE 10 2021 208 941 A1. The rotor shaft of a rotor, usually housed in a stator, is rotatably mounted in corresponding bearing receptacles of a housing, for which two or more bearing locations are provided. The bearings are provided by suitable rolling bearings, often needle or ball bearings. The rotor rotates when the electrical machine is in operation, generating torque that is transmitted to a downstream mechanism. For this purpose, the rotor shaft is provided with a separate pinion with external teeth that in turn mesh with a further gear. The separate pinion is connected to the rotor shaft via splines.The rolling bearings used to support the rotor shaft in the housing are conventional rolling bearings comprising an inner ring, an outer ring, and rolling elements arranged between them, guided in a cage. The inner ring is pressed onto the rotor shaft, and the outer ring is housed in a suitable bearing seat on the housing. This two-part design results in complex machining of the interfaces on both the rotor shaft and the required additional pinion or gear, as well as increased assembly effort for the assemblies. Likewise, a correspondingly large tolerance chain exists with regard to the gearing, since the spline teeth have a certain tolerance, and the teeth of the pinion to the connecting gear do.Increased manufacturing and assembly costs are also involved with regard to the bearings of the rotor shaft, on the one hand for the design of the shaft-side bearing seats for the inner ring, and on the other hand for the rings of the rolling bearing itself, so that a corresponding total tolerance also results on the part of the bearings.

[0004] The invention is based on the problem of providing an improved rotor shaft. To solve the problem, the invention provides a rotor shaft for a rotor of an electric machine, comprising a shaft component on which a toothed section with external teeth is directly machined, and on which a first and a second, each radial, rolling element raceway are directly machined axially adjacent to the toothed section, wherein the toothed section is provided, viewed axially, between the first and the second rolling element raceway, wherein an annular first rolling bearing comprising first rolling elements guided in a first cage and rolling directly on the first rolling element raceway is seated on the first rolling element raceway, and an annular second rolling bearing comprising second rolling elements guided in a second cage and rolling directly on the second rolling element raceway is seated on the second rolling element raceway.wherein the diameter of an enveloping circle of the first rolling elements is smaller than the diameter of a root circle of the external toothing, and wherein the diameter of an enveloping circle of the second rolling elements is larger than the diameter of a tip circle of the external toothing.

[0005] The rotor shaft according to the invention is simplified in design because only a single shaft component is used, on which the relevant interfaces—namely, the gearing required for the output, on the one hand, and the corresponding bearing options, on the other—are directly machined. This eliminates the need for an additional pinion, since the gearing section with the external gearing is an integral part of the shaft component. Likewise, significantly simplified rolling bearings can be used that do not require a separate inner ring, since the rolling elements roll directly on corresponding raceways, which are themselves integrally machined on the shaft component.

[0006] The shaft component has, on the one hand, a toothed section with external teeth in the form of axially extending teeth, this toothed section being formed directly on the shaft component, i.e., it is a one-piece, integral part of the shaft component. Furthermore, a first and a second, each radial, rolling element raceway are formed on the shaft component, axially adjacent to the toothed section, with the first and second rolling element raceways being provided on either side of the toothed section, axially adjacent to it. The toothed section is thus received between the two rolling element raceways, which are preferably arranged very closely adjacent to it, so that this toothing interface is optimally supported in the housing. The toothed section is formed close to one shaft end of the shaft component, as are the two rolling element raceways.A further bearing mount can be formed near the other end of the shaft component; for example, a commercially available rolling bearing can be pressed onto it in order to support the rotor shaft on this side as well.

[0007] The rolling elements of both bearings roll directly on the rolling element raceways, which have corresponding surface properties. Thus, a simple rolling element ring is used in each case, comprising only a cage and the rolling elements guided within it. This leads to a simplified design because, on the one hand, there is no need to produce an interface between the shaft component and the bearing inner ring, which could be subject to tolerances and would be complex to machine, and, on the other hand, the rolling bearing does not have such an interface. The outer bearing support of the rolling element ring in the housing can be achieved, for example, via a pressed-in sleeve or a pressed-in bearing ring.

[0008] Furthermore, a specific diameter geometry is provided on the part of the bearing elements and the gearing elements. According to the invention, the diameter of an enveloping circle of the first rolling element of the first rolling bearing, which is arranged adjacent to the end of the shaft component, is smaller than the diameter of a root circle of the external toothing, i.e., a first step is provided in the transition from the first rolling bearing to the toothing root circle. Furthermore, the diameter of an enveloping circle of the second rolling element is larger than the diameter of the tip circle of the external toothing. i.e., a second step is provided in the transition from the tip circle of the toothing to the second rolling bearing. This stepped design enables the rotor having this rotor shaft to be axially inserted into the stator, combined with the simplified design of the rotor shaft already described and the omission of the separate pinion and the bearing inner ring.The design of the recessed raceways formed directly on the shaft component, as well as the corresponding diameter dimension, allows the rotor components to be assembled from one assembly direction, as well as the rotor itself. In a further development of the invention, the diameter of the second rolling element raceway can be smaller than the diameter of the root circle of the external gearing. This design enables axial runout of the tool used to produce the external gearing, for example, a broaching tool, since it can easily run over the second rolling element raceway during its axial movement without coming into contact with it.

[0009] Furthermore, it can be provided that the diameter of the second rolling element raceway is smaller than the diameter of a receiving section for a rotor lamination stack machined directly on the shaft component. Axially adjacent to the second rolling element raceway is an elongated, cylindrical receiving section for a rotor lamination stack, which is, for example, shrunk onto this receiving section. Since the outer diameter of this receiving section is slightly larger than the outer diameter of the second rolling element raceway, the tool used to form the cylindrical receiving section integrally on the shaft component can, in turn, taper axially.

[0010] A particularly advantageous development provides that the first cage and the second cage are radially expandable. As described, ultimately only rolling element rings are used, comprising a plurality of individual rolling elements, in particular needles, which are accommodated in a cage. According to the invention, each cage or rolling element ring is slightly expandable, so that it can be easily placed on the respective rolling element raceway during assembly as a result of this expansion. In the assembled position, the cage narrows again accordingly, ensuring the best possible enclosure of the rolling element raceway.

[0011] The first cage and / or the second cage can have a lock, i.e. there is a corresponding lock geometry that allows the cage to be opened locally and thus expanded and closed again in the assembly position. In a further development of the invention, it can be provided that the first and / or the second cage has a U-shaped cross-section with two lateral cage legs that axially engage around the first and / or second rolling element raceway that is raised on the shaft component. This axial engagement enables the assembly position of the respective rolling bearing or rolling element ring to be axially fixed in a simple manner. One or both of the rolling element raceways are slightly radially raised on the shaft component, i.e. corresponding circumferential grooves or recesses are formed on both sides of the rolling element raceways, into which the cage legs engage.One or more radial projections can be formed on one or both cage legs to provide radial cage guidance on the shaft component.

[0012] As an alternative to the design of a U-shaped cage, it is also conceivable for ribs to be formed on the shaft component adjacent to the first and / or second rolling element raceway, along which the first and / or second cage are axially guided. This also allows for the axial fixing of the mounting position of the rolling element ring.

[0013] The first and / or second rolling elements are preferably needles or rollers, meaning that needle or roller bearings are used as rolling bearings, and needle or roller rings are used as rolling element assemblies. The first and second needles or rollers can be the same or different in length and / or diameter, depending on the given installation space.

[0014] In addition to the rotor shaft itself, the invention further relates to a rotor for an electrical machine, comprising a rotor shaft of the type described above and a rotor laminated core arranged thereon.

[0015] Finally, the invention relates to an electrical machine comprising a stator and a rotor of the type described above, which is inserted into the stator. The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

[0016] Figure 1 is a schematic diagram, sectioned, of a rotor according to the invention with a rotor shaft according to the invention,

[0017] Figure 2 is an enlarged partial view of the rotor shaft of Figure 1, and

[0018] Figure 3 is a perspective view of part of the rotor shaft of Figure 2.

[0019] Figures 1-3 show a rotor 1 according to the invention, which is part of an electrical machine. Figure 1 shows the entire rotor 1 in section, while Figure 2 shows an enlarged partial view of the rotor from Figure 1 in the area of ​​the left shaft end, while Figure 3 shows a perspective view of the shaft section according to Figure 2.

[0020] The rotor 1 comprises a hollow-cylindrical rotor shaft 2 according to the invention, comprising a shaft component 3, on which a cylindrical receiving section 4 is formed directly and integrally, extending over a substantial part of the length of the shaft component 3, and on which a rotor lamination stack 5 is seated, shown here in dashed lines. In Figure 1, adjacent to the rotor lamination stack 5 on the right, a bearing seat 6 is formed for receiving a rolling bearing, via which the right end of the rotor shaft 2 is rotatably mounted on a housing (not shown).

[0021] In the area of ​​the left end of the shaft component 3, a toothed section 7 with external teeth 8 in the form of axially extending radial teeth is formed directly and integrally on the shaft component 3. To the left and right, adjacent to the toothed section 7, a first rolling element raceway 9 and a second rolling element raceway 10 are also formed directly and integrally on the shaft component 3, on which a first rolling element bearing 11 in the form of a first needle roller and cage 12 and a second rolling element bearing 13 in the form of a second needle roller and cage 14 are arranged. The left end of the rotor shaft 2 is supported in the housing via these two bearing points. The toothed section 7 serves to mechanically couple the rotor shaft 1 to an output gear, which transmits the torque supplied via the rotor shaft 1.

[0022] As Figure 1 already shows, the two rolling bearings 11, 13 are designed as simple needle roller and cage assemblies 12, 14. The first rolling bearing 11 comprises an expandable or expandable first cage 15, on which first rolling elements 16 in the form of needles are received or guided. The second rolling bearing 13 likewise comprises an expandable or expandable second cage 17, on which second rolling elements 18, also in the form of needles, are received or guided. Each rolling bearing 11, 13 therefore has no inner ring; rather, the rolling elements 16, 18 roll directly on the two rolling element raceways 9 and 10, respectively. In the assembled position, the rolling elements 16, 18 roll on the outside on corresponding raceways of outer rings, which are pressed into the housing (not shown) in a suitable manner.

[0023] To axially fix the respective mounting position, as shown in Figure 1, each cage 15, 17 is U-shaped in cross-section. The first cage 15 has a central region 19 in which corresponding pockets are formed, in which the rolling elements 16, i.e. the needles, are received. Radially extending cage legs 20 are provided on both sides of this region 19, which axially surround or engage over the raised first rolling element raceway, as shown in Figure 2. Radial projections 21 formed on the cage legs 20 provide radial guidance of the cage 15 on the shaft component 3, as shown in particular in Figure 3. The second cage 17 is designed in the same way. It also has a central region 22 in which corresponding pockets are formed, in which the needles are received.On both sides of the region 22, corresponding radially extending cage legs 23 are formed, which also axially surround or overlap the raised second rolling element raceway 10, as clearly shown in Figure 2. Here, too, radial projections 24 are formed on the two cage legs 23, which also serve for radial guidance on the shaft component 3.

[0024] As explained, the toothed section 7 with the external toothing 8 is formed between the two rolling element raceways 9, 10 or the rolling elements 11, 13, as clearly shown in Figure 3. The toothed section 7 as well as the rolling element raceways 9, 10 are, as explained, integrally formed on the shaft component 3, i.e., they are formed in one piece and from a single material; no separate components are provided for the realization of these elements.

[0025] As Figure 2 in particular shows, defined geometric relationships exist with regard to both the respective bearings and the gearing. Figure 2 shows various diameters as follows: dL1 : Diameter of the first rolling element raceway 9 dL2 : Diameter of the second rolling element raceway 10 dH1 : Diameter of the enveloping circle of the first rolling elements 16 dH2 : Diameter of the enveloping circle of the second rolling elements 18 dF : Diameter of the root circle of the external gearing 8 dK : Diameter of the tip circle of the external gearing 8 dA : Diameter of the receiving section 4

[0026] Overall, the training is clearly structured in stages, as follows:

[0027] The diameter dH1 of the enveloping circle of the first rolling element 16 is smaller than the diameter dF of the root circle of the external gear 8, so that a first step is formed here. Therefore, dH1 < dF applies.

[0028] Furthermore, the diameter dH2 of the enveloping circle of the rolling elements 18 is larger than the diameter dK of the tip circle of the external gearing 8, so that a second step is formed here. Therefore, dH2 > dK.

[0029] Furthermore, the diameter dL2 of the second rolling element raceway 10 is smaller than the diameter dF of the root circle of the external toothing 8. Therefore, dL2 < dF applies.

[0030] Finally, the diameter dL2 of the second rolling element raceway 10 is also smaller than the diameter dA of the receiving section 4. Therefore, dL2 < dA applies. It is also clear that the diameter dLI of the first rolling element raceway 9 is smaller than the diameter dL2 of the second rolling element raceway 10. Therefore, dL1 < dL2 applies.

[0031] This stepped design allows the individual rotor components, be it the laminated core or the rolling bearings, to be mounted on the shaft component 3 from one side. Furthermore, this stepped design allows the assembly of the finished rotor in the stator while simultaneously coupling the external gearing 8 with a driven gear and completing the bearing positions with the respective bearing ring pressed into the housing by pushing it in from one direction, thus also facilitating this assembly.

[0032] As described, the two rolling elements 11, 13 have expandable or expandable cages 15, 17, which enable easy assembly of the rolling bearings 11, 13, since they can be guided over sections of larger diameter if necessary, after which they narrow again. It is conceivable that each cage 15, 17 has a lock, with such a lock 25 being shown as an example in Figure 3 on the first cage 15. At this point, the cage 15, 17 can be opened and closed again.

[0033] List of reference symbols

[0034] Rotor Rotor shaft Shaft component Mounting section Rotor lamination package Bearing seat Toothing section External toothing Rolling element raceway Rolling element raceway Rolling bearing Needle roller and cage Rolling bearing Needle roller and cage Cage Rolling element Cage

[0035] Rolling element central area Cage leg projection Central area Cage leg projection Lock

Claims

Patent claims 1 . Rotor shaft of a rotor of an electrical machine, with a shaft component (3), on which a toothed section (7) with an external toothing (8) is directly machined, and on which a first and a second, respectively radial rolling element raceway (9, 10) are directly machined axially adjacent to the toothed section (7), wherein the toothed section (7) is provided axially between the first and the second rolling element raceway (9, 10), wherein on the first rolling element raceway (9) there is an annular first rolling bearing (11) comprising first rolling elements (16) guided in a first cage (15) and rolling directly on the first rolling element raceway (9), and on the second rolling element raceway (10) there is an annular second rolling bearing (13) comprising second rolling elements (18) guided in a second cage (17) and rolling directly on the second rolling element raceway (10), wherein the diameter (dH1) of a Enveloping circle of the first rolling elements (16) is smaller than the diameter (dF) of a root circle of the external toothing (8),and wherein the diameter (dH2) of an enveloping circle of the second rolling elements (18) is greater than the diameter (dK) of a tip circle of the external toothing (8)., 2. Rotor shaft according to claim 1, characterized in that the diameter (dL2) of the second rolling element raceway (10) is smaller than the diameter (dF) of the root circle of the external toothing (8).

3. Rotor shaft according to claim 1 or 2, characterized in that the diameter (dL2) of the second rolling element raceway (10) is smaller than the diameter (dA) of a receiving section directly machined on the shaft component (4) for a rotor core (5).

4. Rotor shaft according to one of the preceding claims, characterized in that the first cage (15) and the second cage (17) are radially expandable.

5. Rotor shaft according to one of the preceding claims, characterized in that the first cage (15) and / or the second cage (17) have a lock (25).

6. Rotor shaft according to one of the preceding claims, characterized in that the first and / or the second cage (15, 17) have a U-shaped cross-section with two lateral cage legs (20, 23) which axially encompass the first and / or second rolling element raceway (9, 10) which is provided in raised form on the shaft component (3).

7. Rotor shaft according to one of claims 1 to 5, characterized in that rims are machined on the shaft component (3) adjacent to the first and / or second rolling element raceway (9, 10), on which rims the first and / or the second cage (15, 17) are axially guided.

8. Rotor shaft according to one of the preceding claims, characterized in that the first and / or the second rolling elements (16, 18) are needles or rollers.

9. Rotor for an electrical machine, comprising a rotor shaft (2) according to one of the preceding claims and a rotor laminated core (5) arranged thereon.

10. An electrical machine comprising a stator and a rotor (1) according to claim 9, which is inserted into the stator.

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