DE102021205801A1 - Electrical machine with a stator and a rotor - Google Patents

Abstract

The invention relates to an electrical machine (100, 200) with a stator (2) and a rotor (3), the rotor (3) being designed as an external rotor and extending in the area of an axis of rotation (DA) of the rotor (3). central shaft (3a), a sleeve (3c) arranged radially on the outside of the electrical machine (100, 200) and surrounding the stator (2) and a circular disk (3b) connecting the central shaft (3a) and the sleeve (3c). , wherein surfaces (5a) cooperating with the stator (2) for driving the rotor (3) are formed on the radially inner side (3d) of the sleeve (3c). In order to achieve efficient cooling with such a system, it is proposed that at least one cooling channel (7) through which a coolant can flow is formed in the rotor (3) and extends at least partially through the central shaft (3a), the circular disk (3b ) and the sleeve (3c) extends.

Description

The invention relates to an electrical machine with a stator and a rotor, the rotor being designed as an external rotor and having a central shaft extending in the region of an axis of rotation of the rotor, a sleeve arranged radially on the outside of the electrical machine and enclosing the stator, and a central shaft The circular disk connecting the shaft and the sleeve, surfaces cooperating with the stator for driving the rotor being formed on the radially inner side of the sleeve. The invention also relates to a motor vehicle with such an electric machine for driving the motor vehicle.

An electric machine as described above is known from the prior art and has the advantage of a higher torque density compared to a so-called internal rotor in which the rotor is designed to lie radially on the inside and has surfaces on its radially outer side that interact with the stator to drive the rotor. With a rotor designed as an external rotor, for example when using the electric machine to drive a motor vehicle, a torque sufficient for the drive is generated over a larger speed range than with an internal rotor, so that a gearbox downstream in the drive train can be constructed more simply or smaller and more compactly can, for example with fewer gears.

Known electrical machines with an external rotor are disadvantageously limited in their performance in that heat generated during operation in the area of the rotor is only insufficiently dissipated. Because the magnets arranged on the rotors, by means of which surfaces interacting with the stator for driving the rotor are formed, are temperature-sensitive and demagnetize at excessively high temperatures, the temperatures applied to the magnets must be kept within controlled limits.

It is known from the prior art to ensure cooling of the rotor by means of an air flow. For this purpose, for example, a fan is provided axially in front of or behind the rotor, which is driven in particular by the rotor and generates a draft around and/or through the rotor. Such an arrangement is, for example, from DE 38 20 857 C2 famous. It is also known to use ambient air for cooling in electrical machines with external rotor rotors installed in vehicles and to use the flow generated by the vehicle speed for good heat dissipation, which, however, requires a sufficient vehicle speed. At low vehicle speeds, the disadvantage is that adequate cooling of the electric machine is not guaranteed.

Furthermore, it is known from the prior art to arrange cooling ribs on the rotor in order to achieve improved heat transfer between the rotor and the surrounding air or cooling air.

Disadvantageously, the air cooling systems mentioned cannot provide sufficient cooling capacity, especially for high-power electrical machines, have poor heat transfer and are also associated with significant losses, in particular due to air turbulence and the drag torques generated as a result on the rotor. The latter applies all the more if the rotor has cooling fins. The losses lead to a further deterioration in engine efficiency, particularly at load points where the engine already has only low efficiency values, such as at very low speeds.

the end EP 0 623 988 A2 it is known to provide a cooling jacket with cooling liquid and a cooling channel through which air flows in a stator of an electrical machine with an external rotor. The disadvantage here, however, is that the heat generated on the rotor is not absorbed directly, but only indirectly via the air circulating between the stator and the rotor, so that the rotor and the magnets arranged on it cannot be efficiently cooled. In addition, air flows around the rotor by means of fan blades, which leads to losses as described above.

In view of the prior art, it is an object of the present invention to propose an aforementioned electrical machine with efficient cooling.

This object is achieved according to the invention with an electric machine according to claim 1 and according to a further aspect of the invention with a motor vehicle according to claim 15. Advantageous configurations result from the dependent claims.

According to the invention, at least one cooling channel through which a coolant can flow is formed in the rotor of the electrical machine, which cooling channel extends at least in regions through the central shaft, the circular disk and the sleeve.

For the purposes of the invention, an electrical machine is understood to be a device for converting electrical energy into mechanical energy or vice versa, with a rotating magnetic field on a lateral surface of the stator is generated, through which a torque is exerted on the rotor. An outer cylinder peripheral surface or an inner cylinder peripheral surface is to be understood here as a lateral surface. The stator also has an outer surface, which is arranged opposite the outer surface of the rotor and interacts magnetically with it to generate the torque. In the case of an external rotor, the rotor is arranged radially outside the stator, so that the effective lateral surface of the stator is an outer surface and the effective lateral surface of the rotor is an inner surface. In the case of an internal rotor, on the other hand, the rotor is arranged radially inside the stator, so that the effective lateral surface of the stator is an inner surface and the effective lateral surface of the rotor is an outer surface.

Surfaces that interact with the stator to drive the rotor can be formed by a plurality of magnets that are arranged on the rotor and are, for example, glued or pressed into the radially inner side of the sleeve. A rotor lamination with magnets pressed into it can also be provided on the radially inner side of the sleeve, in which case the radially inner side of the rotor lamination is understood to be surfaces cooperating with the stator to drive the rotor, even if this appears as a single surface.

A shaft is to be understood as meaning a component which is arranged rotationally symmetrically about an axis of rotation and is intended for rotation about this axis of rotation. A shaft is used to transmit a speed and a torque, in particular a drive power of the electric machine. The shaft extends over a greater length in the axial direction than in the radial direction. A sleeve is understood to be a component which is also designed to be rotationally symmetrical about an axis of rotation and which, viewed in axial cross section, forms a circular ring. A circular disk is understood to mean a component which is also rotationally symmetrical about an axis of rotation and which extends in the radial direction over a greater length than in the axial direction and in the axial direction has the cross section of a largely full circle. The sleeve and the circular disc together form a pot shape here, with the sleeve forming the pot wall and the circular disc the pot bottom. In this case, the cup shape or the sleeve has such a large internal diameter that the stator of the electrical machine can be arranged inside.

With the electrical machine according to the invention, direct liquid cooling of the rotor designed as an external rotor is advantageously possible, with which significantly improved heat dissipation is achieved compared to air cooling, in particular air cooling acting only from the outside on the rotor. In particular, the sleeve, on which the surfaces that interact with the stator for driving the rotor are formed, is cooled directly on this surface, and thus directly on the most temperature-sensitive point of the electrical machine, with good heat transfer. The electrical machine can thus advantageously be operated with a higher continuous output. In order to form a particularly powerful electric machine, materials for the magnets of the rotor can also be selected which have particularly good magnetic properties, but which, due to their temperature sensitivity, could not previously be used in external rotors with high performance requirements.

In one embodiment of the invention, water is used as the coolant. Water has a very good heat capacity and thermal conductivity and is therefore particularly suitable as a coolant. In an alternative embodiment, oil is used as the coolant. Oil also has good heat capacity and thermal conductivity and, unlike water, is non-conductive. In the event of an oil leak, there is therefore a lower risk of a short circuit and thus possible damage to the electric machine than with water. In a further embodiment, the electrical machine is designed in such a way that the oil used as a coolant can be used elsewhere for mechanical lubrication.

In a preferred embodiment of the invention, the rotor is designed in one piece or monolithically, which means that the shaft, sleeve and circular disk form a single component. The cooling duct is then formed on the inside and no sealing of the cooling duct along its path through the rotor is necessary. Alternatively, the rotor is composed of several parts, in which case seals are provided between the individual parts or the individual parts are tightly connected to one another, so that an undesired escape of coolant from the cooling channel is prevented. For example, the rotor is made in one piece by means of 3D printing, with complex geometries of the cooling channel being able to be easily formed in a one-piece rotor. Alternatively, the rotor is a lost core casting, where the rotor is cast around a negative of the cooling channel geometry and the negative is removed afterwards. In a multi-part variant, the rotor is composed of two half-shells which are sealed against one another, for example with a flat seal, or welded tightly to one another. In this case, the cooling channel is formed in the surface of a half-shell or in both surfaces of the half-shells that are joined together. The half-shell is formed, for example, by a solid part det, in which the cooling channel is milled or by a sheet metal part, in which the cooling channel is embossed. In a further composite variant, the cooling channel is provided as a bore in a single sleeve, a single circular disk and a single shaft, the sleeve, circular disk and shaft then being assembled and sealed or tightly joined together.

In one embodiment, the cooling channel has a simple geometry of a bore in each of the individual components: shaft, circular disk and sleeve. In a further, preferred embodiment, the cooling channel has a meandering geometry or another type of geometry with a number of changes in direction and/or cross section in the individual components of the shaft, circular disk and sleeve. In this way, the area between the cooling channel and the components is advantageously enlarged and improved heat transfer is achieved.

The central shaft is designed to be rotationally symmetrical about the axis of rotation of the rotor and, in one embodiment, extends partially or entirely through the stator of the electrical machine, the central shaft then being mounted opposite the stator. In a further embodiment, the central shaft extends in the axial direction without intersecting the stator. In one embodiment, the central shaft is formed integrally with the circular disc and does not extend beyond the axial length of the circular disc, in which case the shaft can also be described as the inner area of the circular disc.

The cooling channel in the sleeve preferably extends at least in the axial direction and in the circumferential direction over a large part of the area of the surfaces interacting with the stator for driving the rotor or even over this entire area in order to ensure efficient cooling of these surfaces. In one embodiment, the cooling channel is designed with interruptions in the circumferential direction of the sleeve. A plurality of individual cooling ducts, which extend axially and through which flow occurs in parallel, are therefore formed in the circumferential direction. In particular, the cooling channel extends over the entire radial length of the circular disc in order to connect the part of the cooling channel in the shaft with the region of the cooling channel in the sleeve. Due to the rotation of the rotor in the circular disk, centrifugal forces have a particularly advantageous effect on the coolant, as a result of which the coolant is accelerated in the radial direction and is thus pressed through the entire cooling channel. In this respect, no pressure-increasing means is necessary in order to ensure that the coolant is conveyed through the cooling channel. The choice of the cross section of the cooling channel in the circular disk determines the force and thus the possible delivery rate with which the coolant in the cooling channel is acted upon.

In a first preferred embodiment of the invention, the cooling channel on the central shaft is designed to be rotationally symmetrical about the axis of rotation of the rotor. The coolant is then subject to only slight centrifugal forces in the area of the shaft and is therefore not prevented by such forces from flowing in the axial direction. In the case of a cooling channel arranged rotationally symmetrically in the shaft, transfer of a coolant from a stationary component to the rotating shaft is advantageously possible with a corresponding seal. In a correspondingly more advanced embodiment, the central shaft has an inlet to the cooling channel for receiving coolant. Since the shaft extends in the area of the axis of rotation of the rotor, an inlet to the cooling channel is particularly useful here. This inlet is preferably arranged on an axial end face of the shaft. In the case of a rotationally symmetrical cooling channel in the shaft, a fixed component is then connected axially to the shaft, for example, which is sealed off from the shaft with a corresponding seal that ensures a sealing effect even when there is relative movement between the component and the shaft. Coolant is fed into the cooling channel from the stationary component.

In a further development of this embodiment, an outlet for the coolant to escape from the cooling channel is formed on the sleeve. The coolant thus flows through the cooling channel from the inlet to the outlet and cools the entire rotor in the process. The outlet is preferably arranged on an axial end face of the sleeve, so that the coolant flows out of the sleeve in the axial direction. The coolant is preferably ejected at the outlet without pressure into the surroundings of the electrical machine and can then be collected and fed back into a coolant circuit. It is then not necessary to transfer the sleeve to another component that rotates with the sleeve and/or has to be sealed off from the sleeve.

In a previously described embodiment with several parts of the cooling channel arranged next to one another in the circumferential direction of the sleeve, at least some or all parts of the cooling channel each have a partial outlet, the several partial outlets then being understood as a single outlet.

In a further development of this embodiment, the electric machine includes a storage device for collecting coolant escaping from the outlet. This is designed, for example, as a coolant sump. advantage With the outlet arranged on the sleeve and the storage device, a simple and cost-effective design is created in order to lead coolant out of the cooling channel and collect it. In a variant in which oil is used as the coolant, a storage device designed as a coolant sump serves as a storage device for a cooling circuit of the electrical machine and for lubricating at least one additional component, for example if the electrical machine is equipped with such additional components that require lubrication , is installed in a motor vehicle. For example, the coolant sump is also used to lubricate and cool bearing elements and/or transmission elements.

In a further development of the aforementioned embodiment, the electric machine particularly preferably has a delivery device for delivering the coolant from the storage device to the inlet. The conveying device is formed, for example, from corresponding lines, and may also comprise a fixed component which abuts the shaft and in which coolant is transferred to the shaft as described above. In one embodiment, the conveying of the coolant by the conveying device is caused by the forces acting on the coolant in the circular disk; the coolant is then sucked in by the rotor.

In a second, likewise preferred embodiment, the cooling channel comprises a forward path and a return path, each of which extends at least in regions through the central shaft, the circular disk and the sleeve, with the forward path being designed for the flow of the coolant in a first direction away from the central shaft and the return path is formed for flow of the coolant in a second direction opposite to the first direction toward the central shaft, and the forward path in the sleeve is connected to the return path.

A direction is understood here to be a direction related to the cooling channel, which does not coincide with a single spatial direction of the overall system. The outward and/or return path can also change the spatial direction within each of the components sleeve, central shaft and circular disk and can be arranged, for example, in a meandering shape. The direction then relates in each case to a normal on the cross-sectional area of this cooling channel. The way there and the way back are preferably guided in parallel along the route over which they pass through the rotor. The coolant flows from the center shaft to the sleeve on the way out and from the sleeve to the center shaft on the way back. At the junction of the outward and return paths, the coolant transitions from the outward path to the return path.

In a preferred configuration of this embodiment, the forward path has a larger cross-section than the return path, at least in the circular disc, and/or the forward path is formed in the central shaft on the inside opposite the return path. In both ways, the centrifugal force can achieve a greater force on the coolant in the outward path, so that a flow is established which is directed in the outward path from the central shaft to the sleeve and in the opposite direction on the return path. Advantageously, no additional means for generating a flow then has to be used.

An inlet for the outward path for supplying coolant and an outlet for the return path for the coolant to escape are preferably formed on the central shaft. The coolant can thus be guided out of the rotor and back into the rotor, for example in order to flow through other components, or in order to dissipate heat from the cooling system to the outside at a heat exchanger. The arrangement of the inlet and the outlet on the central shaft, in particular on one or more axial end faces of the central shaft, allows the coolant to be fed in and/or removed from or to stationary components in a sealed manner. A closed circuit can thus be created, which is also impervious to the environment outside the rotor. In such a closed system, the use of water as a coolant is preferred over the use of oil because of its better heat capacity. For this purpose, in the case of the closed system, in contrast to an open system, for example in accordance with the first embodiment described above, it is easy to ensure that no coolant gets outside the cooling circuit. In one embodiment, the outward path and the return path are formed coaxially on the shaft.

In a further development of the aforementioned embodiment, the electrical machine preferably has a delivery device for delivering the coolant from the outlet to the inlet. The conveying device is formed, for example, from corresponding lines and can also comprise stationary components which adjoin the shaft and between which and the shaft coolant is passed as described above. The conveying device is particularly preferably designed to be closed with respect to the environment and forms an overall closed system with the cooling channel. The promotion of the coolant through the conveyor is in one embodiment by in the Circular disc due to forces acting on the coolant.

In both of the aforementioned embodiments, ie both in an open system with an outlet on the sleeve and in a closed system with an outlet on the shaft, it is preferred that the delivery device includes a pressure-increasing means. With such a coolant is pressed into the rotor, wherein the coolant flow can be determined and regulated independently of the rotation of the rotor. The pressure increasing means is preferably a pump.

It is also preferred in both of the aforementioned embodiments that a further cooling channel is provided in the stator, which has an inlet and an outlet. The stator is then integrated into the cooling circuit with this additional cooling channel, so that waste heat produced on the stator can advantageously also be dissipated directly and efficiently. The connection of the cooling circuit to the stator is possible in a simple manner, since the stator is a stationary component.

In a preferred embodiment, the inlet of the stator is connected to the conveying device and the outlet of the stator is connected to the inlet of the rotor. In this respect, the stator is connected in series between the outlet and the inlet of the rotor in a structurally simple manner. In an alternative embodiment, the delivery device is connected to the inlet of the rotor on the one hand and to the inlet of the stator on the other hand, with the outlet of the rotor on the one hand and the outlet of the stator on the other hand being connected to the delivery device. The stator and the rotor are then connected in parallel in the cooling circuit. In one embodiment, a valve is provided in at least one of the parallel parts of the cooling circuit, with which the ratio of the flow rates in the branches of the cooling circuit can be controlled depending on the cooling requirement of the rotor and the stator.

In a particularly preferred embodiment of the invention, a heat exchanger for dissipating thermal energy from the coolant is arranged between the conveying device and the inlet of the rotor. The thermal energy absorbed from the rotor and/or the stator can be dissipated to the environment particularly efficiently via a heat exchanger. The heat exchanger is arranged, for example, between a pressure increasing means and the inlet of the rotor or between an outlet of the stator and an inlet of the rotor.

A further aspect of the invention relates to a motor vehicle with an electric machine as described above for driving the motor vehicle. The stated advantages of the electrical machine are particularly important when it is used as a drive means in a motor vehicle, since high power at high torque densities are required here. When using oil as a coolant, the cooling circuit of the electrical machine is preferably integrated into an existing oil circuit that is provided for lubricating mechanical components on the motor vehicle.

• 1 eine stark vereinfachte schematische Schnittdarstellung einer ersten Ausführungsform der Erfindung mit einem offenen Kühlkreislauf;
• 2 eine stark vereinfachte schematische Schnittdarstellung einer Variante der in 1 gezeigten ersten Ausführungsform der Erfindung;
• 3 eine stark vereinfachte schematische Schnittdarstellung einer zweiten Ausführungsform der Erfindung mit einem geschlossenen Kühlkreislauf;
• 4 eine stark vereinfachte schematische Schnittdarstellung einer Variante der in 2 gezeigten zweiten Ausführungsform der Erfindung; und
• 5 ein stark vereinfachte schematische Darstellung eines erfindungsgemäßen Kraftfahrzeugs.

The invention is described below with reference to figures which show different embodiments of the invention, identical or similar elements being provided with the same reference symbols. In detail shows:

• 1 a greatly simplified schematic sectional view of a first embodiment of the invention with an open cooling circuit;
• 2 a highly simplified schematic sectional view of a variant of in 1 shown first embodiment of the invention;
• 3 a greatly simplified schematic sectional view of a second embodiment of the invention with a closed cooling circuit;
• 4 a highly simplified schematic sectional view of a variant of in 2 shown second embodiment of the invention; and
• 5 a greatly simplified schematic representation of a motor vehicle according to the invention.

1 shows a schematic and not to scale cross section of an electrical machine 100 with a stator 2 shown only in outline and a rotor 3, wherein the rotor 3 is formed from a central shaft 3a, a circular disk 3b and a sleeve 3c, which are connected to one another in one piece. The rotor 3 is rotatably mounted by means of bearings 4 relative to the fixed stator 2 about an axis of rotation DA and has magnets 5 on the radially inner side 3d, which are connected to the stator 2 or to an outer surface 2a formed on the stator 2 for driving the rotor 3 form magnetically interacting surfaces 5a.

A cooling channel 7 is formed in the rotor 3 and extends through the shaft 3a, the circular disk 3b and the sleeve 3c. In the area of the shaft 3a, the cooling channel 7 is rotationally symmetrical about the axis of rotation DA and has a first axial end face 3e of the shaft 3a has an inlet 8. Starting from the shaft 3, the cooling channel 7 extends further through the circular disk 3b and the sleeve 3c and extends in the sleeve 3c, in particular in the area of the magnets 5, so that when a coolant flows through the cooling channel 7, the magnets are cooled effectively is reached. Several parts of the cooling channel 7 are arranged one behind the other in the circumferential direction of the circular disk 3b and the sleeve 3c so that they result in a star-shaped distribution and a stable rotor 3 is created, with only one of these parts being visible in the section shown here. On an axial end face 3f of the sleeve 3c, the cooling channel 7 has an outlet 9 or a plurality of partial outlets distributed around the circumference, which, however, are regarded as one outlet 9.

Due to its rotationally symmetrical arrangement about the axis of rotation DA, the inlet 8 of the cooling channel 7 can be connected to a stationary component (not shown) and sealed with a corresponding movement seal in order to transfer coolant to the inlet 8 .

To cool the rotor 3 during operation of the electric machine 100, a coolant, for example oil, is supplied to the cooling channel 7 at the inlet 8, which then flows from the inlet 8 in the direction of the arrow shown in the cooling channel 7 to the outlet 9 through the cooling channel 7 and in the process absorbs thermal energy , in particular in the area of the magnets 5. The coolant is driven through the cooling channel 7 by the radial centrifugal forces acting on the coolant in the area of the circular disc 3b when the rotor 3 rotates.

The coolant escapes from the cooling channel 7 at the outlet 9 by being ejected into the environment of the electrical machine 100 without pressure. It is then fed to a coolant circuit, which is only shown in a greatly simplified manner here and which includes a storage device 11 in the form of a coolant sump. The coolant sump is arranged so that the coolant ejected from the outlet 9 is collected. The coolant is conveyed back to the inlet 8 from the storage device 11 by means of a conveying device 12 . The conveying device 12 here comprises a pressure-increasing means 13 in the form of a pump and a heat exchanger 14 for dissipating heat from the cooling circuit to the outside.

In a variant of the embodiment according to 1 , in the 2 is shown, the coolant circuit is branched and includes the previously described part in which coolant is conveyed from the storage device 11 to the inlet 8, through the cooling channel 7 and from the outlet 9 back to the storage device 11. Furthermore, on a second flow path 15, coolant is conveyed from the storage device 11 to the stator 2, in which a further cooling channel (not shown here) is formed. The coolant flows through this further cooling channel from an inlet of the stator 2 to an outlet of the stator 2 and from there, like the coolant ejected at the outlet 9 , is likewise fed back to the storage device 11 . Consequently, the coolant flows through the rotor 3 and the stator 2 in parallel.

3 shows a cross-section, again schematic and not to scale, through a second embodiment of an electric machine 200 according to the invention. The rotor 3 consists of a shaft 3a, a circular disk 3b and a sleeve 3c, with magnets 5 for interacting with the stator 2 being arranged on the radially inner side 3d of the sleeve 3c.

The rotor 3 has a cooling channel 7 which is divided into a forward path 7a and a return path 7b. On the shaft 3a, the cooling channel 7 comprises an inner first section 7c assigned to the outward path 7a, on which an inlet 8 is provided on a first axial end face 3e of the shaft 3a. The cooling channel 7 is formed in the circular disk 3b and the sleeve 3c with the outward path 7a and the return path 7b extending next to one another and over the same path. The outward path 7a starts from the first section 7c of the cooling channel 7 in the shaft 3a and is connected in the sleeve 3c to the return path 7b, which extends through the sleeve 3c and the circular disc 3b back to the shaft 3a. A second section 7d of the cooling channel 7 is formed on the shaft 3a, which is assigned to the return path 7b and is connected to the section in the circular disk 3b. The second section 7d is radially further outward than the first section 7c, the second section 7d of the cooling channel 7, like the first section 7c of the cooling channel 7, being rotationally symmetrical about the axis of rotation DA. The second section 7d of the cooling channel 7 includes an outlet 10 on a second axial end face 3g of the shaft 3a.

Both the inlet 8 and the outlet 10 of the cooling channel 7 can be connected to stationary parts (not shown) and sealed with corresponding movement seals due to their rotationally symmetrical arrangement about the axis of rotation DA, in order to form a transfer of coolant at the inlet 8 and the outlet. In this way a closed system is created.

To cool the rotor 3 during operation of the electrical machine 200, the cooling channel 7 a coolant is supplied at the inlet 8, which then flows through the cooling channel 7 from the inlet 8 through the outward path 7a and then through the return path 7b of the cooling channel 7 towards the outlet 10 in accordance with the arrow directions shown. Due to the radial centrifugal forces acting on the coolant in the area of the circular disk 3b when the rotor 3 rotates, the coolant is driven through the cooling channel 7, with a longer path in the circular disk through the radially inner first section 7a of the cooling channel 7 in the outward path 7a 3b is created than in the return path 7b, so that the coolant experiences a greater acceleration there than in the return path 7b in the area of the circular disc 3b, where the centrifugal forces accelerate the coolant against the intended conveying direction. In addition to the radially longer path in the circular disc 3b in the outward path 7a, the outward path 7a in the circular disc 3b is also designed with a larger cross-section than in the return path 7b in the circular disc 3b, so that the acceleration in the outward path 7a is in addition to the opposite acceleration in the return path 7b is enlarged.

The coolant escapes from the cooling channel 7 at the outlet 10 and is fed to a closed coolant circuit, which is only shown schematically here. The coolant circuit in turn includes a delivery device 12 with a pressure-increasing means 13 in the form of a pump and with a heat exchanger 14 for dissipating heat from the cooling circuit to the outside. The coolant circuit extends from the outlet 10 via the pressure-increasing means 13 and the heat exchanger 14 back to the inlet 8 of the rotor.

In a variant of the embodiment according to 3 , in the 4 is shown, the coolant circuit is additionally routed through the stator 2, in which a further cooling channel, not shown here, is formed. After the pressure-increasing means 13, the coolant circuit first flows through the stator 2 and then through the heat exchanger 14 and the rotor 3.

5 shows a motor vehicle 300 according to the invention with a front axle 20 and a rear axle 21 in a highly simplified schematic representation, with an electric machine 100 as described above being arranged on the front axle 20 to drive it.

Reference List

2

stator

2a

outer surface of the stator

3

rotor

3a

central wave

3b

circular disc

3c

sleeve

3d

radially inner side of the sleeve

3e

first axial face of the shaft

3f

axial face of the sleeve

3g

second axial face of the shaft

4

camp

5

magnets

5a

surface interacting with the stator to drive the rotor

7

cooling channel

7a

away

7b

way back

7c

first section of the cooling channel

7d

second section of the cooling channel

8th

inlet of the wave

9

outlet of the sleeve

10

outlet of the wave

11

storage device

12

conveyor

13

pressure increasing means

14

heat exchanger

15

second flow path

20

front axle

21

rear axle

100

electric machine

200

electric machine

300

motor vehicle

THERE

axis of rotation

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 3820857 C2 [0004]
• EP 0623988 A2 [0007]

Claims (15)

Electrical machine (100, 200) with a stator (2) and a rotor (3), the rotor (3) being designed as an external rotor and a central shaft (3a) extending in the area of an axis of rotation (DA) of the rotor (3). ), a sleeve (3c) arranged radially on the outside of the electrical machine (100, 200) and surrounding the stator (2) and a circular disc (3b) connecting the central shaft (3a) and the sleeve (3c), wherein at the radially inner side (3d) of the sleeve (3c), surfaces (5a) cooperating with the stator (2) for driving the rotor (3) are formed, characterized in that in the rotor (3) at least one cooling channel ( 7) which extends at least partially through the central shaft (3a), the circular disc (3b) and the sleeve (3c). Electric machine (100, 200) after claim 1 , wherein the cooling channel (7) on the central shaft (3a) is rotationally symmetrical about the axis of rotation (DA) of the rotor (3). Electric machine (100, 200) after claim 1 or 2 , wherein the central shaft (3a) has an inlet (8) to the cooling channel (7) for receiving coolant. Electric machine (100, 200) after claim 3 , An outlet (9) for the coolant to escape from the cooling channel (7) being formed on the sleeve (3c). Electric machine (100, 200) after claim 4 comprising a storage device (11) for collecting coolant escaping from the outlet (9). Electric machine (100, 200) after claim 5 , comprising a conveying device (12) for conveying the coolant from the storage device (11) to the inlet (8). Electrical machine (100, 200) according to one of Claims 1 until 3 , wherein the cooling channel (7) comprises a forward path (7a) and a return path (7b), each of which extends at least partially through the central shaft (3a), the circular disc (3b) and the sleeve (3c), the forward path ( 7a) is designed for the flow of the coolant in a first direction away from the central shaft (3a) and the return path (7b) is designed for the flow of the coolant in a second direction opposite the first direction towards the central shaft (3a), and wherein the outward path (7a) in the sleeve (3c) is connected to the return path (7b). Electric machine (100, 200) after claim 7 , wherein the outward path (7a) has a larger cross section than the return path (7b) and/or the outward path (7a) is formed in the central shaft (3a) on the inside opposite the return path (7b), at least in the circular disc (3b). Electric machine (100, 200) after claim 7 or 8th , An inlet (8) to the outward path (7a) for supplying coolant and an outlet (10) to the return path (7b) for the escape of the coolant being formed on the central shaft (3a). Electric machine (100, 200) after claim 9 , comprising a conveying device (12) for conveying the coolant from the outlet (10) to the inlet (8). Electric machine (100, 200) after claim 6 or 10 , wherein the conveying device (12) comprises a pressure increasing means (13). Electric machine (100, 200) after claim 6 , 10 or 11 , wherein a further cooling channel is provided in the stator (2), which has an inlet and an outlet, the inlet of the stator (2) being connected to the conveyor (12) and the outlet of the stator (2) being connected to the inlet ( 8) of the rotor (3) is connected. Electric machine (100, 200) after claim 6 , 10 or 11 , wherein a further cooling channel is provided in the stator (2), which has an inlet and an outlet, the conveying device (12) being connected on the one hand to the inlet (8) of the rotor (3) and on the other hand to the inlet of the stator, and wherein the outlet (9, 10) of the rotor (3) on the one hand and the outlet of the stator on the other hand are each connected to the conveying device (12). Electric machine (100, 200) after a Claims 6 or 10 until 13 , wherein between the conveyor (12) and the inlet (8) of the rotor (3) a heat exchanger (14) for dissipating thermal energy from the coolant is arranged. Motor vehicle (300) with an electrical machine (100, 200) according to one of the preceding claims for driving the motor vehicle (300).

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