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

Abstract

The invention relates to a rotor (4) of an electric machine (1), wherein the rotor (2) is designed to be received in a cavity (3) in a stator (2) of the electric machine (1), comprising a magnet carrier (6) and permanent magnets (5) received in the magnet carrier (6), wherein the magnet carrier (6) has a rotationally symmetrical carrier element (11) which has receiving openings (7) for receiving the permanent magnets (5), wherein the receiving openings (5) are each at least partially covered with the aid of a covering element (12) of the magnet carrier (6), such that the permanent magnet (5) arranged in the receiving opening (7) is arranged between the covering element (12) and the carrier element (11), and having a support element (13) comprising the magnet carrier (6). According to the invention, to fix the magnet carrier (6), the support element (13) extends at least in an axial direction, along an axis of rotation (10) of the magnet carrier (6), over an outer circumferential surface (14) of the covering element (12), keeping a partial surface portion (23) of the outer circumferential surface (14) free. The invention also relates to an electric machine (1) having a rotor (4).

Description

[0001] Rotor of an electrical machine and electrical machine with a rotor

[0002] The invention relates to a rotor of an electrical machine according to the preamble of patent claim 1. Furthermore, the invention relates to an electrical machine with a rotor according to patent claim 15.

[0003] Electric machines arranged in a motor vehicle drivetrain are generally known. They comprise a stator and a rotor, with the stator enclosing the rotor. In the case of an electric machine configured as a permanent magnet synchronous machine, permanent magnets are arranged in the rotor. The requirements for the electric machine are high torque combined with a high maximum speed, so that preferably high acceleration and a high top speed of the motor vehicle can be achieved.

[0004] Patent EP 2 553 792 B1 discloses a rotor of an electric machine, wherein the rotor comprises a rotor base body and several outer rotor elements. Permanent magnets are arranged in a V-shape between the rotor base body and the outer rotor elements. The outer rotor elements are positively connected to the rotor base body.

[0005] The published patent application DE 10 2021 124 234 A1 discloses a salient pole rotor, wherein a roving or a fiber bundle is wound in pairs in several turns around the energizable windings in such a way that two opposite salient poles are mechanically connected or braced under tension.

[0006] German Patent Application DE 10 2021 212 953 A1 describes a bandaged rotor of an electrical machine, wherein the bandage is made of a fiber composite material and completely surrounds the rotor over its outer surface. The object of the present invention is to provide an improved rotor of an electrical machine. A further object of the invention is to specify an improved electrical machine.

[0007] The object is achieved according to the invention with a rotor of an electrical machine having the features of patent claim 1. The further object is achieved with an electrical machine having the features of patent claim 15.

[0008] Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the respective subclaims.

[0009] A first aspect of the invention relates to a rotor of an electrical machine, wherein the rotor is designed to be received in a cavity of a stator of the electrical machine. The rotor comprises a magnet carrier and permanent magnets received in the magnet carrier. The magnet carrier has a rotationally shaped carrier element which has receiving openings for receiving the permanent magnets, wherein the receiving openings are at least partially covered by a cover element of the magnet carrier, such that the permanent magnet arranged in the respective receiving opening is arranged between the cover element and the carrier element. Furthermore, the magnet carrier has a support element surrounding it. According to the invention, for fixing the magnet carrier, the support element extends at least in the axial direction, along a rotation axis of the magnet carrier, over an outer circumferential surface of the cover element, while keeping a

[0010] Partial surface section of the outer peripheral surface. In other words, this means that the cover element and thus a casing of the magnet carrier is not covered with the support element. A significant advantage of the invention is that, compared to complete coverage of the cover element, a decrease in magnetic flux density caused by coverage with the support element can be significantly reduced. This leads to higher magnet utilization, in addition to the possible increase in speed and torque of the electric machine having the rotor, so that a cost-effective reduction in magnet mass can be realized. The support element extends, in particular along the axis of rotation, centrally, thus along a center of a circumference of the outer peripheral surface, over the cover element, so that the cover element is reliably secured by the support element even at high speeds.Furthermore, the main advantage is that there are equally sized partial surface sections on both sides of the support element, over which the complete magnetic flux can be formed.

[0011] If the support element is band-shaped, it can be wound around the magnet carrier in a simple and cost-effective manner. The band-shaped form is achieved, for example, in the form of a fiber or a fiber composite, which is characterized by a plurality of fibers arranged in a matrix, preferably an epoxy resin matrix. The fiber itself, and thus the support element, is advantageously made of a carbon fiber material or a glass fiber material.

[0012] Applying the carbon fiber material or the glass fiber material to the magnet carrier, wherein the fiber of the carbon fiber material is arranged extending in the axial direction, or in other words aligned, leads to a simple and thus cost-effective “axial” winding technique.

[0013] By applying the carbon fiber only to parts of a rotor surface, thus keeping the partial surface sections free, an improved thermal connection between the rotor and the stator is possible, so that a higher continuous power can be achieved in certain operating ranges.

[0014] If the support element is designed to extend radially over a first end face of the magnet carrier and a second end face of the magnet carrier, the now implemented "axial-radial" winding technology can also be used to axially support individual electrical sheets of the magnet carrier, eliminating the need for axial fixation using, for example, a shaft nut. If, for example, the magnet carrier were wound tangentially with the support element, this could lead to very high prestressing of the usually laminated magnet carrier, which is also referred to as the rotor iron core. If the temperature increases, as occurs during rotor operation, additional mechanical stress can occur in the magnet carrier due to very different thermal expansion coefficients of the magnet carrier and the support element.This can lead to buckling failure under dynamic force excitations, a so-called disc spring effect, with subsequent delamination of the magnet carrier.

[0015] A further significantly improved rotor is achieved if the support element is accommodated in a recess formed in the cover element. The support element can thus be arranged in a guided manner in the recess and is securely accommodated in the recess during operation of the rotor. A further significant advantage of accommodating the support element in the recess is that a magnetic air gap formed between the stator and the rotor, which must be kept as small as possible to increase the torque, can be kept as small as possible. Or in other words, a magnetic air gap height, which is composed of a mechanical air gap height and a support element height, can be reduced because the support element can be accommodated with its entire height in the recess in order to mitigate the effect of a reduction in magnetic flux density.This further increases magnet utilization and thus reduces the use of magnetic mass, which in turn reduces material costs. The smallest possible magnetic air gap height should be provided, since a larger magnetic air gap height could lead to irreversible demagnetization of the permanent magnets.

[0016] The recess is designed in a cost-effective groove shape.

[0017] To prevent excessive stress in the support element in the area where it deflects from the outer peripheral surface to the end face, the recess is rounded along its axial outer edges. If the rotor is designed as an axially laminated rotor lamination stack to reduce eddy current losses in the iron sheet, the outer diameter of the individual iron sheet laminations can also be reduced in very small steps toward the end face to reduce the excessive stress effect. The support element is preferably applied to the magnet carrier using a so-called direct wet winding process.

[0018] If the rotor has a balancing element for simplified balancing, which is preferably in the form of a disk and arranged on an end face of the magnet carrier, the support element extends over the balancing element. In other words, the balancing element is also enclosed by the support element. The balancing element could advantageously also have groove-shaped recesses in which the support element can be arranged.

[0019] If the magnet carrier has a connecting means on its first end face and / or on its second end face for establishing a connection to a shaft, which can also be referred to as a rotor shaft, in the form of a positive fit, it is possible to wind the support element around the magnet carrier in a simple and thus cost-effective manner, since the connecting means can accommodate the support element in these grooves due to its grooves designed to establish a positive fit. The connecting means is advantageously designed in the form of a claw coupling to establish the connection, whereby a positive force transmission can be achieved.

[0020] If the connection is designed to be electrically actuated, there is the advantage of reducing drag losses, since the rotor can be easily uncoupled from the shaft.

[0021] A second aspect of the invention relates to an electric machine with a rotor, wherein the rotor is designed according to one of claims 1 to 14. Thus, the electric machine according to the invention is designed to potentially increase the speed and torque compared to an electric machine according to the prior art. Likewise, with the same torque, the electric machine could be smaller, in particular the permanent magnets could be smaller, thereby creating a cost-effective electric machine.

[0022] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Identical or functionally equivalent elements are assigned identical reference numerals. They show:

[0023] Fig. 1 shows a section through an electrical machine according to the prior art,

[0024] Fig. 2 shows a sectional view of an electrical machine according to the prior art in a variant,

[0025] Fig. 3 shows a perspective view of a rotor according to the invention of an electrical machine according to the invention,

[0026] Fig. 4 shows a section through the rotor. Fig. 3,

[0027] Fig. 5 shows a detailed view of a recess in a cover element of the rotor in a schematic representation. Fig. 3,

[0028] Fig. 6 shows a section through the rotor in Fig. 3 with magnetic flux lines, and

[0029] Fig. 7 shows a schematic diagram of a connection of the rotor according to the invention. Figures 1 and 2 each show a section and a sectional detail of variants of an electric machine 1 for a motor vehicle according to the prior art. The electric machine 1 is designed as an internal rotor and has a sleeve-shaped stator 2, which is designed to accommodate a rotor 4 in its cavity 3.

[0030] The stator 2 has a stator core consisting of a plurality of individual laminations. The stator 2 is designed to accommodate a winding of the electric machine 1 (not shown in detail).

[0031] The rotor 4 of the electric machine 1 according to Fig. 1 has so-called "buried" permanent magnets 5, which are completely enclosed by a magnet carrier 6 of the rotor 4. The permanent magnet 5 is accommodated in a receiving opening 7 formed in the magnet carrier 6, with radial webs 8 and tangential webs 9 being formed between adjacent receiving openings 7. The webs 8, 9 can also be referred to as rotor iron webs. The permanent magnets 5 are arranged in a V-shape.

[0032] As the rotational speed of the rotor 4 increases about its rotational axis 10, the centrifugal force acting on the rotor 4 increases disproportionately, with the centrifugal force also being absorbed by the webs 8, 9. To reduce the mechanical stresses occurring in the webs 8, 9, an increase in the cross-section of the webs 8, 9 leads to an increase in the magnetic leakage flux in the support element 6. However, the magnetic leakage flux represents a reduction in the possible achievable torque of the electric machine 1.

[0033] To increase the maximum speed, it is possible to encase the magnet carrier 6 in order to fix the magnet carrier in the presence of high centrifugal forces caused by a high speed, or in other words, to stabilize it. The encasement allows the elimination of the webs 8, 9. In other words, this means that the webs 8, 9 do not necessarily have to be formed as long as the encasement is present. The magnet carrier 6 is designed in several parts according to the number of magnetic poles, with a rotationally shaped carrier element 11 being designed to accommodate cover elements 12. The cover elements 12 are designed to securely mount the permanent magnets 5 in receiving openings 7 formed in the carrier element 11. Fixing, in particular, of the cover elements 12 and the permanent magnets 5 takes place, as illustrated in Fig. 2, with the aid of a support element 13 that completely encloses the rotor 4.Due to the elimination of the webs 8, 9, the magnetic stray flux is reduced, so that the torque of the electric machine 1 can be increased. Magnetic flux lines and flux density when the electric machine 1 is idling are shown as examples. It can be seen that, compared to a rotor topology as shown in Fig. 1, a reduced magnetic stray flux is formed at the outer edges 24 of the cover elements 12 because the radial webs 9 have been omitted. Likewise, the magnetic stray flux between the permanent magnets 5 is reduced by the elimination of the tangential webs 8.

[0034] A rotor 4 according to the invention of an electrical machine 1 according to the invention is illustrated in a perspective view in Fig. 3. It also has no webs 8, 9. It should be noted that the electrical machine 1 is designed as a permanent magnet synchronous machine.

[0035] The rotationally shaped carrier element 11, which has receiving openings 7 for receiving the permanent magnets 5 of the rotor 4, wherein the receiving openings 7 are each at least partially covered by a cover element 12 such that the permanent magnet 5 is arranged between the cover element 12 and the carrier element 11, has the support element 13 for fixing the cover element 12. This extends at least along the rotation axis 10 over the cover element 12, wherein the cover element 12 is partially uncovered over its outer circumferential surface 14, while keeping a partial surface section 23 of the outer circumferential surface 14 free. In other words, this means that part of the outer circumferential surface 14 of the cover element 12 is kept free and is uncovered opposite the stator 2. The support element 13 is band-shaped. To produce the band-shaped support element 13, a corresponding fiber can be wound multiple times around the magnet carrier 6.Likewise, a finished band, which has a width B of the support element 13 comprising the magnet carrier 6, could be wound once or several times around the magnet carrier 6 to create the support element 13.

[0036] The support element 13 is formed from a carbon fiber, which is wound around the magnet carrier 6, particularly in a so-called wet process, with an epoxy resin preferably being used as the matrix. The support element 13 could also be constructed from a glass fiber material. A fiber of the carbon fiber material, or the glass fiber material, is arranged or wound to extend in the axial direction according to arrow P and in the radial direction.

[0037] The thermal conductivity of the carbon fiber transversely to the fiber direction and of a matrix formed from the epoxy resin is lower than the thermal conductivity of the magnet carrier 6, which is usually made from an iron-containing electrical sheet. Due to the only partial, or in other words partial, arrangement of the carbon fiber in the form of the support element 13 on the outer circumferential surface 14, an improved thermal connection between the rotor 4 and the stator 2 can be realized compared to a complete sheathing, which can lead to a higher continuous power in certain operating ranges of the electrical machine 1.

[0038] To securely fix the rotor 4, support elements 13 are wound in a star shape over the magnet carrier 6. In the present exemplary embodiment, three support elements 13 are arranged around the magnet carrier 6, corresponding to a number of pole pairs, wherein the support elements 13 are designed to clamp the magnet carrier.

[0039] The support element 13 is fixed with its element end (not shown in detail), for example, centrally on a first end face 15 of the magnet carrier, thus centrally on the rotation axis 10, and then wound over the magnet carrier 6. The support element 13 is arranged in a radial direction over the first end face 15, further over the outer circumferential surface 14 of one of the cover elements 12, from there further over a second end face 16 of the magnet carrier 6, which is designed to face away from the first end face 15, over the outer circumferential surface 14 of the cover element 12 opposite one of the cover elements 12, and finally again to its element end over the first end face 15.Depending on a winding material of the support element 13, that is to say in other words, whether the winding material is in the form of a fiber, or whether it is in the form of a fiber composite or fiber composite tape, the above-mentioned process takes place several times.

[0040] The support element 13 extends centrally over the cover element 12. This means that the partial surface section 23 can be formed on both sides of the support element 13, and in particular in equal-sized parts.

[0041] In order to avoid an enlargement of a mechanical air gap 17 formed between the stator 2 and the rotor 4, which would lead to a reduction in the torque of the electrical machine 1, the support element 13 is received in a recess 18 in the cover element 12.

[0042] The recess 18 is preferably groove-shaped. To ensure secure bracing of the magnet carrier 6, the recesses 18 have rounded portions on their axial outer edges 19. In other words, this means that the recesses 18 are not sharp-edged but rounded on their outer edges 19. The rounding is such that the recess 18 is rounded at its axial outer edges 19, facing the rotation axis 10, so to speak, as illustrated in a schematic diagram in Fig. 5. A radius R of the rounding is to be selected such that excessive mechanical stress on the support element 13 is avoided. The rounded portions of the outer edges 19 could also be designed in the form of small steps, wherein a continuous decrease in step height and step width is preferably formed starting from the outer circumferential surface 14.If the magnet carrier 6 has a balancing element (not shown in detail), which is usually in the form of a disk with a thickness of 5 - 10 mm, for example, the support element 13 is designed to extend over the balancing element. The balancing element then also has a recess in an axial continuation of the recess 18. In this exemplary embodiment, the respective end faces 15, 16 of the magnet carrier 6 would be realized with the aid of the balancing disk. The balancing disk could have a radially extending groove in the radial direction, essentially as a continuation of the recess 18, in which the support element 13 is received. Of course, the balancing element here has the rounded outer edge on its groove.

[0043] Fig. 6 shows a sectional view of the rotor 4 according to the invention showing magnetic flux lines M. It can be seen that the magnetic flux lines M advantageously extend directly over the carrier element 11 and the cover element 12 across the mechanical air gap 17 to the opposite stator 2, and only spread over the support element 13 in a small area with reduced effectiveness. This results in low magnetic resistance with high inductance L along a q-axis of the rotor 4 (the magnetic flux lines M are shown in solid lines here), and high magnetic resistance with low inductance L along a d-axis of the rotor 4 (the magnetic flux lines M are shown in dashed lines here).If, however, the magnet carrier 6 were completely wound around its circumference, or in other words, formed with a tangential winding, this would result in a high magnetic resistance with a low inductance L along the q-axis and a low magnetic resistance with a high inductance L along the d-axis. This would result in an increase in the reluctance torque compared to a tangential winding due to the changed inductance ratios.

[0044] For advantageous wrapping of the magnet carrier 6, a connecting means 20 of the rotor 4, which is provided for connection to a shaft 21, which can also be referred to as a rotor shaft, is designed in particular in a claw-shaped manner to bring about the connection in the form of a positive connection with the shaft 21 shown in principle in Fig. 7. Or in other words, the connecting means 20, which can be designed in the form of a shaft journal, also has grooves 25 in which the support element 13 is arranged. The connecting means 20 is arranged on the first end face 15 and / or the second end face 16. Of course, the shaft 21 is complementary to the

[0045] Connecting means 20 are designed to implement the positive locking. Fig. 7 shows the form-locking connection to be achieved in its basic form, advantageously illustrating a so-called claw coupling.

[0046] In a further embodiment, the electric machine 1 according to the invention has an electrical actuation of the positive connection.

[0047] List of reference symbols

[0048] 1 Electric machine

[0049] 2 Stator

[0050] 3 Cavity

[0051] 4 Rotor

[0052] 5 Permanent magnet

[0053] 6 magnetic carriers

[0054] 7 Receiving opening

[0055] 8 Radial bridge

[0056] 9 Tangential bridge

[0057] 10 Rotation axis

[0058] 11 Support element

[0059] 12 Cover element

[0060] 13 Support element

[0061] 14 Outer peripheral surface

[0062] 15 First frontal surface

[0063] 16 Second front surface

[0064] 17 Mechanical air gap

[0065] 18 recess

[0066] 19 Outer edge

[0067] 20 connecting devices

[0068] 21 Wave

[0069] 22 Connection

[0070] 23 sub-area section

[0071] 24 Element outer edge

[0072] 25 grooves

[0073] B Width

[0074] L Inductance

[0075] M magnetic flux line

[0076] P Arrow

[0077] R radius d d-axis q q-axis

Claims

Patent claims 1 . Rotor (4) of an electrical machine (1), wherein the rotor (2) is designed to be received in a cavity (3) of a stator (2) of the electrical machine (1), comprising a magnet carrier (6) and permanent magnets (5) received in the magnet carrier (6), wherein the magnet carrier (6) has a rotationally shaped carrier element (11) which has receiving openings (7) for receiving the permanent magnets (5), wherein the receiving openings (5) are at least partially covered by a cover element (12) of the magnet carrier (6), such that the permanent magnet (5) arranged in the receiving opening (7) is arranged between the cover element (12) and the carrier element (11), and having a support element (13) enclosing the magnet carrier (6), characterized in that for fixing the magnet carrier (6), the support element (13) extends at least in the axial direction, along a rotation axis (10) of the magnet carrier (6), over an outer circumferential surface (14) of the cover element (12),extends, while keeping a partial surface section (23) of the outer peripheral surface (14) free., 2. Rotor (4) according to claim 1, characterized in that the support element (13) extends centrally over the cover element (12).

3. Rotor (4) according to claim 1 or 2, characterized in that the support element (13) is band-shaped.

4. Rotor (4) according to one of the preceding claims, characterized in that the support element (13) is formed from a carbon fiber material or a glass fiber material.

5. Rotor (4) according to claim 4, characterized in that a fiber of the carbon fiber material or the glass fiber material is arranged extending in the axial direction.

6. Rotor (4) according to one of the preceding claims, characterized in that the support element (13) extends in the radial direction over a first end face (15) of the magnet carrier (6) and a second end face (16) of the magnet carrier (6) is formed extending.

7. Rotor (4) according to one of the preceding claims, characterized in that the support element (13) is arranged in a recess formed in the cover element (12) recess (18).

8. Rotor (4) according to claim 7, characterized in that the recess (18) is groove-shaped.

9. Rotor (4) according to claim 7 or 8, characterized in that the recess (18) is rounded at its axial outer edges (19).

10. Rotor (4) according to one of the preceding claims, characterized in that the support element (13) is applied in a direct wet winding process.

11. Rotor (4) according to one of the preceding claims, characterized in that the support element (13) is designed to extend over a balancing element of the rotor (4).

12. Rotor (4) according to one of the preceding claims, characterized in that the magnet carrier (6) has on its first end face (15) and / or on its second end face (16) a connecting means (20) for bringing about a connection (22) with a shaft (21) in the form of a positive connection.

13. Rotor (4) according to claim 12, characterized in that the connecting means (20) for bringing about the connection (22) is designed in the form of a claw coupling.

14. Rotor (4) according to claim 12 or 13, characterized in that the connection (22) is designed to be electrically actuated.

15. Electrical machine (1) with a rotor (4), characterized in that the rotor (4) is designed according to one of claims 1 to 14.

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