ROTOR FOR AN ELECTRIC MACHINE

Abstract

A rotor (1) for an electric machine is provided, wherein the rotor (1) comprises a rotor lamination stack (10) having a central opening (15) and a rotor shaft (20) which is press-fitted into the central opening (15) of the rotor lamination stack (10). The rotor (1) includes at least one insert element (30a-d) which is inserted between the rotor lamination stack (10) and the rotor shaft (20), wherein the press fit is partially interrupted by the at least one insert element (30a-d).

Description

[0001] The present disclosure relates to a rotor for an electric machine, an electric machine comprising the rotor, and / or a motor vehicle comprising the electric machine.

[0002] Electric machines can be used in motor vehicles, for example, as traction machines, each of which comprises a stator and a rotor. Typically, the energy provided by a magnetic interaction between the stator and the rotor is captured via the rotation of the rotor and used, for example, to drive the electrically powered motor vehicle or another machine in the vehicle.

[0003] A rotor typically consists of a laminated core and a rotor shaft, which is housed in a central opening in the laminated core. Currently, the connection between the laminated core and the rotor shaft is achieved by means of a thermal transverse interference fit. This means that the laminated core is heated to approximately +200°C and the rotor shaft is cooled to approximately -190°C. This overcomes the interference (geometric overlap) at the joining surfaces caused by thermal expansion, thus enabling joining without the need for force. Furthermore, the interference fit exists over the entire circumference and along the entire length of the connection.

[0004] For mechanical reasons, the interference between the rotor shaft and the laminated core must be selected so that the maximum torque at zero speed and the torque occurring at maximum speed can be reliably transmitted. It has been shown that the decisive parameter is the effective interference and not the effective joining surface. Another important point when designing this connection, especially for drives with rotor cooling, is to consider the heat conduction from the laminated core via the rotor shaft, e.g. to the cooling medium inside the rotor shaft. For thermal reasons, the largest possible surface area should be aimed for to ensure optimal heat conduction. However, this contradicts the requirement for reliable torque transmission, since higher torque can generally be transmitted with smaller joining diameters.

[0005] Another important point is the ability to convert the joining of the interference fit from a thermal transverse interference fit to another type of interference fit, which generally reduces the energy required for this joining process compared to a thermally joined transverse interference fit, i.e., for heating the laminated core and cooling the rotor shaft. This other type of interference fit can be realized, for example, using a longitudinal interference fit. Since the energy consumption required for a longitudinal interference fit is related to the engaging joining surface of the two joining partners, the aim here is to keep this joining surface as small as possible.

[0006] DE 10 2021 124 316 A1 describes a rotor for an electrical machine, comprising a rotor core and a shaft device, which is inserted into a through-opening of the rotor core oriented along a rotational axis of the rotor and is connected to the rotor core in a rotationally fixed manner. The shaft device comprises a first shaft element, which has a first stop for support on a first end face of the rotor core, and a second shaft element connected to the first shaft element. The second shaft element has a second stop for support on a second end face of the rotor core, which is opposite the first end face in the axial direction of the rotor.

[0007] DE 10 2014 206 848 A1 describes a structural unit for an electrical machine, which comprises an annular laminated core formed from a plurality of axially stacked laminations. The laminated core is secured to a cylindrical receiving portion of a support element by means of an inner or outer cylindrical fastening portion. The support element has two stops between which the laminated core is axially clamped in a force-locking manner. At least one of the stops comprises an annular support element, which is arranged on the receiving portion and supports the laminated core and which is secured to the support element by means of at least one caulking region.

[0008] JP 2000-184645 A describes a motor with a rotor and a stator arranged on the outside of the rotor. A plurality of disc-shaped core sheets having through-holes are stacked to form a stacked core. The core, in which permanent magnets are placed on the through-holes, is enclosed between and held by a pair of disc-shaped end plates having through-holes, pins, and inner rings. The pins are frictionally connected and fixed to the through-holes, and the inner rings are frictionally connected and fixed to the through-holes. A shaft serving as an output shaft is frictionally inserted and fixed into the through-holes in the end plates.

[0009] Against the background of this prior art, the object of the present disclosure is to provide a device and / or a method which are each suitable for enriching the prior art.

[0010] The problem is solved by the features of the independent claims. The subordinate claims and the dependent claims each contain optional developments of the disclosure.

[0011] The task is then solved by a rotor for an electric machine.

[0012] The rotor comprises a rotor core which has a central opening.

[0013] The rotor comprises a rotor shaft which is fitted into the central opening of the rotor core by means of an interference fit (e.g. a longitudinal interference fit).

[0014] The rotor comprises at least one insert element that is inserted between the rotor core and the rotor shaft. The interference fit is interrupted by the at least one insert element in some areas (or in at least one area between the rotor core and the rotor shaft in which the at least one insert element is arranged). In other words, in at least one area between the rotor core and the rotor shaft in which the at least one insert element is arranged, there is no effective interference fit (or no interference and / or no direct contact between the rotor core and the rotor shaft).

[0015] The rotor described above offers a number of advantages. For example, it provides an arrangement that enables the rotor shaft and the rotor laminated core to be joined as an interference fit, e.g., a longitudinal interference fit, without adversely affecting functional properties, e.g., reliable torque transmission and heat dissipation from the rotor for the highest possible continuous power. For this purpose, the interference fit, distributed over the circumference of the joining surfaces, only has direct contact or an interference fit between the rotor shaft and the laminated core in certain areas, i.e., outside of at least one insert element, while still enabling reliable torque transmission and the necessary energy or force for assembly as an interference fit, e.g., a longitudinal interference fit.Thus, the present disclosure advantageously leads to one of the requirements of (continuous) power density for an electrical machine while simultaneously simplifying and reducing the cost of assembly.

[0016] Possible further developments of the rotor described above are explained in detail below.

[0017] The at least one insert element can have a contact surface for contacting the rotor shaft and a contact surface for contacting the rotor core. The contact surface for contacting the rotor shaft and the contact surface for contacting the rotor core can be arranged (or formed) on two opposite sides of the at least one insert element.

[0018] The rotor core and / or the rotor shaft can have at least one groove that is designed to accommodate the at least one insert element and is shaped to match the at least one insert element. A longitudinal direction of the at least one groove can extend in an axial direction of the rotor shaft.

[0019] The at least one groove can be formed in a joining surface of the rotor core and / or in a joining surface of the rotor shaft. It is conceivable that a groove in the joining surface of the rotor core and a groove in the joining surface of the rotor shaft form a receiving pocket (or a gap) for receiving the at least one insert element.

[0020] The at least one groove can be completely filled by the at least one insert element. The at least one insert element can extend along the entire length of the at least one groove.

[0021] The at least one insert element can be slat-shaped (and / or bar-shaped). A longitudinal direction of the at least one insert element can extend in an axial direction (or a longitudinal direction) of the rotor shaft (and / or the rotor or the rotor core).

[0022] The at least one insert element can have a concave and / or inwardly curved contact surface along a circular arc for contact with the rotor shaft.

[0023] The at least one insert element can have at least one (e.g., lateral) undercut, optionally two (e.g., lateral) undercuts, which can be formed in the direction of the rotor shaft (or which can be formed in the direction of the rotor shaft). The at least one undercut can extend in the longitudinal direction of the insert element.

[0024] The at least one insert element can have a contact surface for contact with the rotor shaft. The contact surface can be designed for (e.g., additional) positive engagement with the rotor shaft. This can advantageously serve, for example, as an anti-twist device or to absorb very sudden torque shocks or impulses during operation of the rotor (or electric machine), so that torque can be transmitted reliably.

[0025] The at least one insert element can have an H-shaped cross-section and / or two spaced-apart outer legs, each of which has a contact surface for contacting the rotor shaft or the rotor core. This allows the contact surfaces, e.g., the contact surface for contacting the rotor core, to be advantageously optimized or maximized, wherein the at least one insert element can be arranged as close as possible to a heat source of the rotor (e.g., windings or excitation coils arranged around rotor poles).

[0026] The at least one insert element can be pre-assembled on and / or in the rotor core. Alternatively, or additionally, the at least one insert element can be pre-assembled on and / or in the rotor shaft.

[0027] The at least one insert element can consist of a highly thermally conductive material and / or a material with a thermal conductivity in the range of aluminum or higher.

[0028] The rotor may comprise a plurality of insert elements. The plurality of insert elements may be identical or at least partially different. The plurality of insert elements may be arranged offset from one another in the circumferential direction between the rotor shaft and the rotor core, e.g., at equal intervals from one another.

[0029] The rotor can be a salient-pole rotor and / or the rotor core can be designed for a salient-pole rotor. The rotor core can have multiple salient poles. The salient poles can each consist of a pole core and a pole shoe and / or extend in the radial direction of the rotor core. The salient poles can be spaced (e.g., regularly spaced) from one another in the circumferential direction of the rotor core.

[0030] The rotor core may have a rotor yoke that forms the central opening and / or in which the central opening is formed. The rotor yoke may be hollow-cylindrical. The salient poles may be spaced (e.g., regularly spaced) from one another (in the circumferential direction of the rotor yoke) on the rotor yoke.

[0031] The rotor may include excitation coils and / or windings that can be supplied with an electric current. The excitation coils and / or windings may, for example, be wound around the pole cores of the rotor core stack.

[0032] The above description can be summarized in other words and in a possible more concrete embodiment of the disclosure as described below, whereby the following description is not to be interpreted as limiting the disclosure.

[0033] According to the present disclosure, a joint assembly can be designed such that joining as an interference fit, e.g., a longitudinal interference fit, is possible without adversely affecting the functional properties (safe torque transmission and heat dissipation of the rotor for the highest possible continuous performance).

[0034] For this purpose, the interference fit can have direct contact or an oversize between the rotor shaft and the laminated core only in certain areas distributed over the circumference and still enable a secure torque transmission and the necessary energy or force for the assembly design as an interference fit, e.g. longitudinal interference fit.

[0035] A thermal aspect is taken into account by inserting additional elements or inserts (i.e. the insert elements) that have a high thermal conductivity, e.g. aluminum or copper, into the gaps between the laminated core and the rotor shaft, i.e. where there is no interference fit, which fill the gaps between the laminated core and the rotor shaft.

[0036] These elements or inserts can be pre-assembled either in the laminated core or in the rotor shaft before the joining process. It is also conceivable that these elements could be inserted after the joining process.

[0037] There are various possible designs for these elements or inserts, depending on requirements and needs. The simplest option, for example, could be for the element or insert to have a simple circular cylindrical shape. A shape that anchors this element or insert to the laminated core by means of an undercut is also possible. Another design can provide an additional form-fit connection with the rotor shaft, which can transmit the torque and thus serve, for example, as an anti-twist device or to absorb very sudden torque shocks or impulses. A shape that optimizes and / or maximizes the contact area between the element or insert and the laminated core is also possible, or that brings this element or insert as close as possible to the heat source (e.g. copper windings around a rotor pole or rotor core).

[0038] In addition to the variants mentioned here as examples, other geometries, shapes and contours for these elements or inserts as well as their interfaces and functions with the rotor shaft and laminated core are possible.

[0039] Furthermore, an electric machine (e.g. for a motor vehicle) is provided which comprises the rotor described above.

[0040] The electrical machine can, for example, be a current-excited (or separately excited) synchronous machine.

[0041] The electric machine may comprise a stator which may surround the rotor at least circumferentially or in the circumferential direction.

[0042] The stator may have (electrical) conductors (or coils) which can be supplied with an electric current, e.g. an alternating current and / or three-phase current, to drive the rotor.

[0043] What was described above with reference to the rotor also applies analogously to the electric machine and vice versa.

[0044] Furthermore, a motor vehicle is provided which comprises the electric machine described above.

[0045] The motor vehicle may be an electrically powered vehicle. The electric machine may be designed as a traction motor or traction machine of the motor vehicle.

[0046] The motor vehicle may include an electrical source, e.g., a traction battery, for supplying electrical energy to the stator and / or the rotor (e.g., the conductors or coils of the stator and / or the rotor).

[0047] The motor vehicle may be a passenger car, in particular an automobile, or a commercial vehicle, such as a truck.

[0048] What has been described above with reference to the rotor and the electric machine also applies analogously to the motor vehicle and vice versa.

[0049] Below is an optional embodiment with reference to Fig. 1 to 7 described. Fig. 1 shows schematically an oblique view of a rotor according to the disclosure, Fig. 2a-d show schematic oblique views of four insert elements, Fig. 3 shows a schematic oblique view of a rotor core, Fig. 4 shows a schematic oblique view of the rotor core with three of the insert elements, Fig. 5 shows a schematic sectional view of the rotor core with the four insert elements in cross section, Fig. 6 shows schematically an oblique view of a rotor shaft, and Fig. 7 shows a schematic oblique view of the rotor shaft with one of the insert elements.

[0050] The Fig. 1, the rotor 1, which is shown only schematically, comprises a rotor core 10 and a rotor shaft 20, which is joined into a central opening of the rotor core 10 by means of a press fit, e.g. a longitudinal press fit.

[0051] The rotor 1 comprises four insert elements 30a, 30b, 30c, and 30d, which are inserted between the rotor core 10 and the rotor shaft 20, wherein the interference fit is partially interrupted by the insert elements 30a, 30b, 30c, and 30d. The number of insert elements is chosen merely as an example to illustrate the insert element(s) options described in more detail below. According to the disclosure, the rotor 1 comprises at least one insert element, i.e., the rotor 1 can also comprise fewer than four or more than four insert elements.

[0052] The insert elements 30a, 30b, 30c, 30d (or the at least one insert element) can each consist of a highly thermally conductive material and / or a material with a thermal conductivity in the range of aluminum or higher.

[0053] In the Fig. 2a to 2d, the four insert elements 30a, 30b, 30c, 30d are shown individually, which merely represent possible options of the insert element(s).

[0054] Thus, the insert elements 30a, 30b, 30c, 30d are slat-shaped or bar-shaped, wherein their respective longitudinal direction runs in an axial direction R of the rotor shaft 20 in a state installed or introduced (into the rotor 1).

[0055] Furthermore, the insert elements 30a, 30b, 30c, 30d each have a contact surface 31a, 31b, 31c, 31d for contact with the rotor laminated core 10 and a contact surface 32a, 32b, 32c, 32d for contact with the rotor shaft 20.

[0056] The contact surface 32a of the Fig. The insert element 30a shown in Fig. 2a is concave (in the width direction) or curved inwards along a circular arc.

[0057] The contact surface 32b of the Fig. The insert element 30b shown in Fig. 2b can, analogously to the contact surface 32a, be concave or bent inwards along a circular arc, wherein the insert element 30b additionally has lateral undercuts 33 which are formed in the direction of the contact surface 32b and extend in the longitudinal direction of the insert element 30b.

[0058] The contact surface 32c of the Fig. The insert element 30c shown in Fig. 2c is designed for positive engagement with the rotor shaft 20.

[0059] The Fig. The insert element 30d shown in Fig. 2d has an H-shaped cross section, so that the insert element 30d has two spaced outer legs 34a, 34b and an inner leg 34c which connects the two outer legs 34a, 34b to each other.

[0060] On the outer leg 34b, the contact surface 31d is designed to engage the rotor laminated core 10, and on the outer leg 34a, the contact surface 32d is designed to engage the rotor shaft 20, wherein the contact surface 32d, analogous or similar to the contact surfaces 32a, 32b, can be concave or curved inwards along a circular arc.

[0061] Fig. Figure 3 shows the rotor core 10 in a single view. The rotor core 10 can be configured for a salient-pole rotor and can accordingly have a plurality of salient poles, each consisting of a pole core 13 and a pole shoe 14, which can be arranged, for example, at regular intervals from one another in the circumferential direction. In the fully assembled state of the rotor 1, excitation coils or windings can be wound around the pole cores, which in turn can be supplied with electrical current during operation of an electrical machine comprising the rotor 1.

[0062] The rotor core 10 has a central opening 15 for receiving the rotor shaft 20. The central opening 15 is formed by a closed inner surface 11 of the rotor core 10, wherein this inner surface 11 represents the joining surface 11 of the rotor core 10 in the joined state with the rotor shaft 20.

[0063] Furthermore, four grooves 12a, 12b, 12c and 12d are formed in the inner surface or joining surface 11, which extend in the axial direction (or longitudinal direction) R and are designed to each receive one of the four previously described insert elements 30a, 30b, 30c, 30d.

[0064] Fig. 4 shows the rotor core 10 based on Fig. 3, wherein the three insert elements 30a, 30b and 30d are additionally received in the corresponding grooves 12a, 12b and 12d.

[0065] The insert elements 30a, 30b, 30d can be pre-assembled on or in the rotor core 10, ie in the grooves 12a, 12b, 12d, before the rotor shaft 20 is joined into the rotor core 10 by means of the interference fit, e.g. longitudinal interference fit.

[0066] Fig. 5 shows a sectional view of the rotor laminated core 10 in cross section, wherein additionally all four insert elements 30a, 30b, 30c and 30d are accommodated in the corresponding slots 12a, 12b, 12c and 12d.

[0067] As shown in this sectional view, each of the grooves 12a, 12b, 12c, 12d can be configured to conform to the respective insert element 30a, 30b, 30c, 30d, so that the grooves 12a, 12b, 12c, 12d are completely filled by the insert elements 30a, 30b, 30c, 30d.

[0068] Fig. 6 shows the rotor shaft 20 in a single view, wherein an outer surface 21 represents the joining surface 21 of the rotor shaft 20 in the joined state with the rotor laminated core 10.

[0069] In the outer surface or joining surface 21, for example, a groove 22 is formed which extends in the axial direction (or longitudinal direction) R and is designed to receive the insert element 30c.

[0070] Fig. 7 shows the rotor shaft 20 based on Fig. 6, wherein the insert element 30c is additionally received in the groove 22. The groove 22 can be designed to match the shape of the insert element 30c.

[0071] The insert element 30c can be pre-assembled on or in the rotor shaft 20, ie in the groove 22, before the rotor shaft 20 is joined into the rotor core 10 by means of the interference fit, e.g., longitudinal interference fit.

[0072] In the joined state, the groove 22 of the rotor shaft 20 and the groove 12c of the rotor laminated core can form a receptacle or gap in which the insert element 12c is received and is filled by this, e.g. completely.

[0073] The rotor 1, e.g. in the previously described embodiment, can represent a part of an electric machine, which electric machine can in turn be installed in a motor vehicle, e.g. as a drive motor. List of reference symbols 1 rotor 10 rotor lamination stack 11 Rotor joining surface 12a, 12b, 12c, 12d grooves 13 rotor cores 14 rotor shoes 15 central opening 20 Rotor shaft 21 Joint surface of the rotor shaft 22 grooves 30a, 30b, 30c, 30d insert elements 31a, 31b, 31c, 31d Contact surfaces for contact with the rotor core 32a, 32b, 32c, 32d Contact surfaces for contact with the rotor shaft 33 undercuts 34a, 34b outer thigh 34c inner thigh 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 10 2021 124 316 A1

[0006] DE 10 2014 206 848 A1

[0007] JP 2000-184645 A

[0008]

Claims

[1] Rotor (1) for an electrical machine, the rotor (1) comprising: - a rotor core (10) having a central opening (15); and - a rotor shaft (20) which is fitted into the central opening (15) of the rotor core (10) by means of a press fit, characterized by that the rotor (1) comprises: - at least one insert element (30a-d) which is introduced between the rotor laminated core (10) and the rotor shaft (20), wherein the interference fit is partially interrupted by the at least one insert element (30a-d). [2] Rotor (1) according to claim 1, characterized by that the rotor laminated core (10) and / or the rotor shaft (20) has at least one groove (12a-d; 22) which is designed to receive the at least one insert element (30a-d) in a shape adapted to the at least one insert element (30a-d). [3] Rotor (1) according to claim 1 or 2 characterized bythat the at least one insert element (30a-d) is slat-shaped and / or a longitudinal direction of the at least one insert element (30a-d) runs in an axial direction (R) of the rotor shaft (20). [4] Rotor (1) according to one of claims 1 to 3, characterized by that the at least one insert element (30a; 30b; 30d) has a concave and / or circular arc-curved contact surface (32a; 32b; 32d) for contact with the rotor shaft (20). [5] Rotor (1) according to one of claims 1 to 4, characterized by that the at least one insert element (30c) has a contact surface (32c) for contact with the rotor shaft (20), wherein the contact surface (32c) is designed for positive engagement with the rotor shaft (20). [6] Rotor (1) according to one of claims 1 to 5, characterized bythat the at least one insert element (30d) has an H-shaped cross-section and / or two spaced outer legs (34a, 34b), on each of which a contact surface (31d, 32d) is formed for contact with the rotor shaft (20) or the rotor laminated core (10). [7] Rotor (1) according to one of claims 1 to 6, characterized by that the at least one insert element (30a-d) is pre-assembled on and / or in the rotor laminated core (10) and / or on and / or in the rotor shaft (20). [8] Rotor (1) according to one of claims 1 to 7, characterized by that the at least one insert element (30a-d) consists of a thermally highly conductive material and / or a material with a thermal conductivity in the range of aluminum or higher. [9] Electric machine, characterized by that the electrical machine comprises the rotor (1) according to one of claims 1 to 8. [10] Motor vehicle, characterized bythat the motor vehicle comprises the electric machine according to claim 9.

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