CN113346653A

CN113346653A - Rotor for an electric machine, electric machine and motor vehicle

Info

Publication number: CN113346653A
Application number: CN202011307822.6A
Authority: CN
Inventors: M·卢克斯; L·韦特劳; P·苏斯; M·施罗德; V·切诺戈斯基; K·韦伯
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2020-02-18
Filing date: 2020-11-20
Publication date: 2021-09-03
Also published as: DE102020104149A1

Abstract

A rotor for an electrical machine (1) having a rotor shaft (15), a carrier (8) which is coupled to the rotor shaft in a rotationally fixed manner and at least one squirrel cage winding (9) or winding which is arranged on the carrier, the rotor shaft comprising a cavity (10) for conducting a coolant through the rotor shaft, a radial shaft outer wall (7) of which has at least one through-opening (14) through which a cooling fluid can flow out of the cavity, which opens into a channel system, which comprises at least one annular channel and at least one carrier channel which is flow-coupled to the annular channel and which extends in the axial direction inside the carrier, a respective annular channel which extends annularly around the rotor shaft outside the carrier and is formed jointly with the shaft outer wall and/or the carrier by a respective guide member which is arranged on the outside on the shaft outer wall, the respective guide member having at least one discharge opening, which radially penetrates the guide element and through which the coolant can flow out of the channel system into the environment of the rotor.

Description

Rotor for an electric machine, electric machine and motor vehicle

Technical Field

The invention relates to a rotor for an electric machine, comprising a rotor shaft, a carrier, which is coupled to the rotor shaft in a rotationally fixed manner, and at least one squirrel cage winding arranged on the carrier or a winding arranged on the carrier, wherein the rotor shaft comprises a cavity for conducting a coolant through the rotor shaft, wherein a radial shaft outer wall of the rotor shaft has at least one through-opening, through which a cooling fluid can flow out of the cavity. The invention further relates to an electric machine and a motor vehicle.

Background

A rotary electric machine can be composed of a stator and a rotor, wherein the rotor can carry windings or, for example in an asynchronous machine, cage windings. For example, the rotor can be formed by a rotor shaft and a carrier which carries windings or squirrel cage windings and can be constructed, for example, as a lamination stack. When the electric machine is operated as a motor or a generator, power losses occur not only on the stator side but also on the rotor side. The waste heat thus generated results in the continuous power of the electric machine being limited by the amount of heat that can be dissipated, since the maximum temperature determined cannot be exceeded without damaging the electric machine.

In the simplest case, only the stator is cooled, for example by a water jacket. However, in order to achieve a high continuous power, it is advantageous to cool the rotor directly. Different solutions are known for this purpose.

In a first variant, the cooling of the rotor can be achieved solely by flowing a coolant through the rotor shaft, for example by means of a tube cooling device. In this case, it is disadvantageous that heat must be conducted from the winding or the cage winding via a plurality of heat transfer points, namely on the one hand to the rotor laminations and on the other hand from the rotor laminations to the shaft, as a result of which the cooling power is reduced.

Therefore, in order to improve the cooling of the squirrel cage windings, it is known to spray or splash the short-circuit rings of the squirrel cage windings directly with coolant. Different solutions are known for this. For example, the coolant can be supplied via the rotor shaft and, due to the centrifugal force, can flow out through the openings of the rotor shaft in order to wet the short-circuit rings. Alternatively, the coolant can be sprayed axially in the region of the short-circuit ring close to the end of the shaft by means of a fixed small tube or the like. A disadvantage of these solutions is that the coolant first reaches the short-circuit ring in the circumferential direction of the rotor at low or no speed, and the short-circuit ring moves at a great speed in the circumferential direction, in particular at high rotational speeds. This results in the short-circuit ring accelerating the coolant in contact therewith, whereby a braking torque must be exerted on the short-circuit ring and thus on the rotor. Therefore, spraying the short-circuit loop directly with coolant necessarily results in a braking torque, whereby additional losses can occur and the performance of the electric machine can be reduced.

Disclosure of Invention

The object of the present invention is therefore to provide an improved possibility for cooling an electric machine, which avoids or at least reduces the above-mentioned problems.

This object is achieved by a rotor of the type mentioned at the outset in that the through-openings open into a channel system which comprises at least one annular channel and at least one carrier channel which is flow-coupled to the annular channel and which extends in the axial direction inside the carrier, wherein the respective annular channel extends annularly around the rotor shaft outside the carrier, which annular channel is formed by a respective guide part which is arranged on the outside on the shaft outer wall and/or the carrier, wherein the respective guide part has at least one outlet opening which extends radially through the guide part and through which coolant can flow out of the channel system into the environment of the rotor.

The design of the rotor according to the invention enables, on the one hand, the direct removal of heat from the carrier, i.e. for example the stator lamination, by conducting the coolant through the carrier channels, without additional heat transfer from the carrier to the shaft being required. Thus, an improved heat dissipation is achieved with respect to the initially discussed guiding of the coolant only through the shaft.

On the other hand, the coolant is guided by collecting the coolant in the annular channel or by the guide element with a relatively small radius, at which the rotor has a lower speed in the circumferential direction of the rotor at the same rotational speed than in the region of the windings or the cage windings. As a result, the coolant is accelerated significantly less by the rotation of the rotor than in the case of the above-described direct spray short-circuit ring, so that the above-described braking of the rotation by the coolant is largely avoided. By selecting the outer radius of the annular channel or arranging the carrier channel in the radial direction of the rotor, it is possible in the design of the rotor or the electric machine to balance whether the coolant is to be conducted very close to the shaft, and therefore whether the shaft is to be avoided almost completely because of braking of the coolant, or whether the coolant is to be conducted on a larger radius, which may improve the cooling performance, but may also lead to a stronger braking of the rotor.

As will be explained in more detail below, the outlet opening is preferably arranged such that at least a large part of the discharged coolant cannot contact the rotor with a large radius and thus brake the rotor. The carrier passage may preferably extend axially completely through the carrier. In this case, preferably, annular channels or guide means forming annular channels are provided on both sides of the carrier to guide the coolant and to discharge it in a controlled manner through the discharge opening.

In principle, however, it is also possible that the carrier channel does not extend completely through the carrier in the axial direction and is open, for example, only at an axial end face of the carrier and opens into the annular channel. For example, the through-holes can open into the carrier channel, and the coolant can flow from this point through the carrier channel to the end side, where the carrier channel is open and is collected there by the annular channel.

The carrier channels can extend in particular linearly in the axial direction of the rotor. However, it is also possible that it extends at least partially also in other directions, for example in a radial direction or in a circumferential direction. For example, the carrier channel may helically surround the rotor shaft or the like.

The supply of coolant into the rotor can be achieved by means of a cavity. In particular, a stationary or co-rotating tube may be provided which introduces the coolant into the cavity. By the rotation of the shaft, the coolant is then accelerated and, due to centrifugal forces, is pressed against the shaft outer wall or through the through-opening. The coolant may be a liquid, such as oil or water. The coolant is preferably conducted out of the rotor only via one or more outlet openings.

The at least one outlet opening is preferably arranged axially spaced apart from the carrier and the winding or squirrel cage winding. The coolant flowing out of the discharge opening moves substantially perpendicular to the axial direction due to the inertia or centrifugal force of the fluid. Thus, at least a substantial part of the discharged coolant passes by the carrier and the winding or the cage winding and impinges, for example, on the winding heads of the stator, the housing of the electric machine, etc., by means of the axial spacing. Thereby, the coolant does not contact the rotor on a larger radius and further does not cause the above-mentioned braking.

The at least one through hole may be spaced apart from the carrier in the axial direction. In particular, the through-holes therefore do not open into the carrier channel, but rather collect the outflowing coolant via the annular channel or the guide member. This results in a relatively simple design of the carrier on the one hand, and the cavity for supplying the coolant does not have to extend, or does not have to extend too far, into the region in which the carrier is arranged on the rotor shaft on the other hand.

The cavity can be connected to the channel system by at least one through-opening only on one side of the carrier. In particular, the coolant can thus enter the channel system on one side of the carrier, be guided through at least one carrier channel to the other side of the carrier, and be discharged there, for example via an annular channel and a discharge opening provided thereon. The axial transport of the coolant along the carrier channels can thereby be achieved by centrifugal forces acting on the coolant as a result of the rotation of the rotor.

The rotor may in particular comprise a first annular channel and a second annular channel, which are arranged on axially opposite sides of the carrier and are connected by at least one carrier channel. In particular, the at least one through-opening opens into the first annular channel. If the through-opening or through-openings all end in the first annular channel, the second annular channel is connected to the cavity inside the rotor only via the first carrier channel and the first annular channel. Thereby, as mentioned above, the axial transport of the coolant through the carrier channels can also be achieved on the basis of the centrifugal forces acting on the coolant.

It may also be advantageous to use a first annular channel and a second annular channel arranged on axially opposite sides of the carrier if the through-hole or through-holes open into the carrier channel or channels. The coolant can then be guided in both directions in the axial direction into the respective annular channel adjacent to the axial end of the carrier and can be discharged in this annular channel through the discharge opening, so that in this case the coolant transport can also be driven by centrifugal force.

The respective guide member may comprise a blocking element extending radially outwards from a radially outer wall of the annular channel through which the at least one discharge opening of the guide member extends, wherein the carrier and the at least one discharge opening of the guide member are arranged on opposite sides of the blocking element. The blocking element may in particular have a disc shape. By using the blocking element, the coolant can be substantially completely prevented from coming into contact with the other rotor components after being discharged through the discharge opening. The squirrel cage winding or windings are in particular also arranged on the side of the blocking element facing away from the discharge opening. The blocking element can additionally or alternatively be used to support or cool the short-circuit ring or the winding, for example in such a way that the blocking element contacts an end face of the short-circuit ring.

The at least one through opening may be arranged offset in the circumferential direction with respect to the at least one outlet opening and/or with respect to a respective axial end of the at least one carrier channel. Additionally or alternatively, the axial ends of the respective carrier channels may be staggered in the circumferential direction with respect to the at least one discharge opening. In particular, the discharge openings and the channel inlets may be arranged alternately in the circumferential direction. Depending on which through-opening the coolant flows out of, the coolant can thus be supplied, for example, primarily to the carrier channel or primarily to the discharge opening.

In addition to the rotor according to the invention, the invention also relates to an electric machine, in particular a drive motor for a motor vehicle, having a stator and a rotor according to the invention. In particular, the axial position of the outlet opening on the rotor can be selected such that the outlet opening is located in the region of the winding heads of the stator, whereby the winding heads can be additionally cooled by the discharged coolant.

The invention also relates to a motor vehicle comprising an electric machine according to the invention. The electric machine according to the invention can be used in particular as a drive machine, wherein energy can also be recovered, for example, by operating as a generator. When used as a drive motor, the continuous power performance of the motor is particularly important, so that effective cooling of the rotor, as it is achieved by the design according to the invention, is also particularly important.

Drawings

Further advantages and details of the invention emerge from the following exemplary embodiments and from the accompanying drawings. Here, it is schematically shown that:

fig. 1 shows an embodiment of an electrical machine according to the invention, comprising an embodiment of a rotor according to the invention,

FIG. 2 shows a cross-sectional view of the rotor shown in FIG. 1, taken along the line II-II, an

Fig. 3 shows an exemplary embodiment of a motor vehicle according to the invention.

Detailed Description

Fig. 1 shows an electric machine 1, which comprises a stator 2 and a rotor 3 which is mounted so as to be rotatable relative to the stator 2. Fig. 1 shows a section through an electric machine 1, wherein only a part of the electric machine 1 on the side of the axis of rotation 30 is shown for reasons of clarity and on account of the symmetrical construction of the electric machine 1. The stator 2 comprises a stator-side carrier 4, for example a lamination stack, and a winding 5, of which only the winding head 6 is shown in fig. 1. The stator 2 may be cooled, for example, by a water jacket cooling device, not shown.

The rotor 3 comprises a rotor shaft 15 and a carrier 8, for example a lamination stack, which is coupled in a rotationally fixed manner to the rotor shaft 15 and which carries a squirrel cage winding 9 formed by conductor bars 22 and short-circuit rings 31 connecting the conductor bars. Instead of the squirrel cage windings 9, at least one rotor-side winding can also be provided.

In order to achieve sufficient heat dissipation of the rotor 3, in particular of the cage winding 9, and thus a high continuous performance of the electric machine 1, a coolant is conducted through the rotor 3, as is indicated schematically in fig. 1 by the arrow 11. The components relating to the coolant guidance are explained below with additional reference to fig. 2, which fig. 2 shows a section through the rotor 3 along the line II-II. For a clearer illustration, the through-openings 14, the outlet openings 18 and the carrier channels 24 are illustrated here in fig. 1 at the same position in the circumferential direction of the rotor 3, although they are arranged offset from one another in the circumferential direction, as can be seen in fig. 2. For the same reason, the through opening 14 and the outlet opening 18 are shown in fig. 2 in a sectional plane, although they are arranged offset to one another in the axial direction as shown in fig. 1.

The coolant is fed into the cavity 10 inside the rotor shaft 15 via a pipe 12. The tube 12 can be stationary relative to the stator 2, i.e. does not rotate with the rotor 3. Alternatively, however, co-rotating tubes 12 may be used.

The inflowing coolant impinges on the intermediate wall 13 inside the rotor shaft 15. By the rotation of the rotor shaft 15, the coolant is also brought into rotation and is thus guided to the shaft outer wall 7 of the rotor shaft 15. At the shaft outer wall, the coolant flows from the cavity 10 through a plurality of through-openings 14 spaced apart in the circumferential direction into the channel system 25, wherein the coolant is first collected in a first annular channel 16 by the guide member 17, which is formed by the guide member 17, the shaft outer wall 7 and the carrier 8 together.

The coolant received in the first annular channel 16 is transported out of the first annular channel 16 due to centrifugal forces. In this case, a portion of the coolant is discharged directly through the outlet opening 18. The discharge openings 18 are axially spaced from the carrier 8 and the squirrel cage windings 9 so that the coolant is substantially guided to the winding heads 6 of the stator 2 without further contact with components of the rotor 3. This prevents the rotor from being braked due to the contact of the coolant with the rotor parts over a large radius, as already explained at the outset.

Furthermore, the first annular channel 16 is coupled by a carrier channel 24 with a second annular channel 19, which is formed by the further guide part 27, the shaft outer wall 7 and the carrier 8. Through the further outlet opening 20, which extends through the outer wall 28 of the annular channel 19, the coolant can be discharged from the second annular channel 19 onto the winding head 6 of the stator 2 on the basis of centrifugal force. As already explained for the discharge from the annular channel 16, further contact with components of the rotor 3 is avoided by the corresponding axial arrangement of the discharge openings 20. By continuously discharging the coolant via the discharge opening 20, the coolant is further sucked from the first annular channel 16 by the carrier channel 24, so that the entire coolant transport can be achieved by centrifugal force.

Upon discharge from the

discharge openings

18, 20, the coolant is distributed over a certain spatial angular range. Depending on the specific design of the electric machine 1 or of the rotor 3, a portion of the coolant can collect in this case in a region 26 which is located radially inside the respective short-circuit ring 31. Since this may lead to a braking of the rotor 3, it is advantageous to provide a blocking element 21, for example in the form of a disk, which substantially completely prevents coolant from entering the region 26 or spraying the carrier 3 or the short-circuit ring 31.

As shown in fig. 2, the through-openings 14 are arranged offset in the circumferential direction both with respect to the outlet openings 18 and with respect to the axial ends 29 of the carrier channels 24. By selecting the arrangement of these elements, a desired distribution of the coolant over the discharge openings 18 and the carrier channels 24 can be achieved.

Fig. 3 shows an exemplary embodiment of a motor vehicle 23, which comprises an electric machine 1 constructed as described above with a corresponding stator 2 and rotor 3. The electric machine 1 can be in particular a drive motor of a motor vehicle 23. It is particularly important for the drive motor to achieve a high continuous power performance, so that sufficient cooling of the rotor is particularly important, which can be achieved with little effort by the measures described.

Claims

1. A rotor for an electrical machine (1), having a rotor shaft (15), a carrier (8) which is coupled to the rotor shaft (15) in a rotationally fixed manner and at least one squirrel cage winding (9) which is arranged on the carrier (8) or a winding which is arranged on the carrier, wherein the rotor shaft (15) comprises a cavity (10) for guiding a coolant through the rotor shaft (15), wherein a radial shaft outer wall (7) of the rotor shaft (15) has at least one through-opening (14) through which a cooling fluid can flow out of the cavity (10),

it is characterized in that the preparation method is characterized in that,

the through-hole (14) opens into a channel system (25) which comprises at least one annular channel (16, 19) and at least one carrier channel (24) which is flow-coupled to the annular channel (16, 19) and which extends in the axial direction inside the carrier (8), wherein the respective annular channel (16, 19) extends annularly around the rotor shaft (15) outside the carrier (8), the annular channel is formed by corresponding guide parts (17, 27) and the shaft outer wall (7) and/or the carrier (8) together, the guide parts are arranged on the outer side of the shaft outer wall (7), wherein the respective guide member (17, 27) has at least one discharge opening (18, 20), the at least one outlet opening, through which the coolant can flow out of the channel system (25) into the environment of the rotor (3), radially extends through the guide part (17, 27).

2. The rotor as recited in claim 1, characterized in that the at least one discharge opening (18, 20) is arranged axially spaced apart from the carrier (8) and the winding or squirrel cage winding (9).

3. The rotor according to claim 1 or 2, characterized in that the at least one through hole (14) is spaced apart from the carrier (8) in the axial direction.

4. The rotor as recited in claim 3, characterized in that the cavity (10) is connected with the channel system (25) only on one side of the carrier (8) by the at least one through hole (14).

5. The rotor according to any one of the preceding claims, characterized in that it comprises a first and a second of the annular channels (16, 19) arranged on axially opposite sides of the carrier (8) and connected by at least one carrier channel (24).

6. The rotor as recited in claim 5, characterized in that the at least one through hole (14) opens into the first annular channel (16).

7. The rotor according to any one of the preceding claims, characterized in that the respective guide member (17, 27) comprises a blocking element (21) extending radially outwards from a radially outer wall (28) of the annular channel (16, 19) which is penetrated by the at least one discharge opening (18, 20) of the guide member (17, 27), wherein the carrier (8) and the at least one discharge opening (18, 20) of the guide member (17, 27) are arranged on opposite sides of the blocking element (21).

8. The rotor as recited in any one of the preceding claims, characterized in that the at least one through hole (14) is arranged offset in the circumferential direction with respect to the at least one discharge opening (18, 20) and/or with respect to a respective axial end (29) of the at least one carrier channel (24), and/or the axial end (29) of the respective carrier channel (24) is offset in the circumferential direction with respect to the at least one discharge opening (18, 20).

9. An electric machine, in particular a drive motor of a motor vehicle (23), having a stator (2), characterized in that it comprises a rotor (3) according to any one of the preceding claims.

10. A motor vehicle, characterized in that it comprises an electric machine (1) according to claim 9.