DE102021108905A1 - electrical machine - Google Patents

Abstract

The invention relates to an electrical machine (1), in particular for a hybrid or fully electrically operable drive train (2) of a motor vehicle (3), comprising a stator (4) and a rotor (5) which is rotatably mounted relative to the stator (4) and has a rotor shaft (8) and a rotor body (9) which is non-rotatably connected to the rotor shaft (8), the stator (4) having a large number of stator slots (6) which extend through the stator (4) in the axial direction and into which a stator winding (7 ), wherein the stator slots (6) can be flowed through by a hydraulic fluid (10), wherein at least one pump disk (11) is coupled to the rotor (5) in a rotationally fixed manner and is designed in such a way that the hollow shaft (13) is designed and with the hydraulic fluid (10) fillable rotor shaft (8), the hydraulic fluid (10) can be guided under pressure through the stator slots (6) of the stator (4).

Description

The present invention relates to an electrical machine, in particular for a hybrid or fully electrically operable drive train of a motor vehicle, comprising a stator and a rotor which is rotatably mounted relative to the stator and has a rotor shaft and a rotor body which is non-rotatably connected to the rotor shaft, the stator having a plurality of axial direction through the stator extending stator slots, in which a stator winding is accommodated, wherein the stator slots are traversed by a hydraulic fluid.

Electric motors are increasingly being used to drive motor vehicles in order to create alternatives to internal combustion engines that require fossil fuels. Significant efforts have already been made to improve the suitability for everyday use of electric drives and also to be able to offer users the driving comfort they are accustomed to.

A detailed description of an electric drive can be found in an article in the ATZ magazine, volume 113, 05/2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrative and flexible electric drive unit for electric Vehicles. This article describes a drive unit for an axle of a vehicle, which includes an electric motor that is arranged concentrically and coaxially with a bevel gear differential, with a switchable 2-speed planetary gear set being arranged in the power train between the electric motor and the bevel gear differential, which is also is positioned coaxially to the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and allows a good compromise between climbing ability, acceleration and energy consumption due to the switchable 2-speed planetary gear set. Such drive units are also referred to as e-axles or electrically operable drive train.

In addition to purely electrically operated drive trains, hybrid drive trains are also known. Such drive trains of a hybrid vehicle usually include a combination of an internal combustion engine and an electric motor, and allow - for example in urban areas - a purely electric mode of operation with simultaneous sufficient range and availability, especially for cross-country trips. In addition, there is the possibility, in certain operating situations, to be driven simultaneously by the internal combustion engine and the electric motor.

In the development of electric machines intended for e-axles or hybrid modules, there is a continuing need to increase their power densities, so that the cooling required for this, in particular of the electric machines, is becoming increasingly important. Due to the necessary cooling capacity, hydraulic fluids, such as cooling oils, have prevailed in most concepts for dissipating heat from the thermally stressed areas of an electrical machine.

The gears usually provided in the designated e-axles or hybrid modules are usually lubricated with a gear oil, which is often also used as cooling oil for the electric machine. In order to bring the lubricant or cooling oil reliably to the various lubricating or cooling points, it is known to form a hydraulic fluid circuit in the corresponding drive device. A hydraulic pump is often used for safe operation of the hydraulic fluid circuit.

Such hydraulic pumps are usually implemented as external pumps that are driven, for example, by an electric motor. However, it is also known to drive the hydraulic pump by the drive device, ie the electric machine and/or the transmission itself, in order in this way to be able to dispense with an additional electric motor.

In the pamphlet DE 197 50 675 C1 discloses an oil pump for automatic automobiles, the oil pump being disposed in a housing of a transmission of the automobile. The oil pump is arranged coaxially to an output shaft of the transmission.

The pamphlet U.S.A. 4,922,765 discloses a transmission for a vehicle with an oil pump, a rotor shaft of the oil pump being offset parallel to an output shaft. The rotor shaft is arranged on a further output shaft and is therefore coaxial with it.

The pamphlet US 2003/0002976 A1 discloses a disc pump for various applications. The pamphlet US 1,061,206A is the patent of the inventor of the Tesla pump. The pamphlet US 5,443,130A discloses an electric axle for a vehicle with an oil pump. The pamphlet DE 10 2011 004 698 A1 describes a further configuration of an electric axle which has an oil pump.

The object of the invention is to at least overcome the disadvantages known from the prior art to reduce or completely avoid and provide a compact electrical machine with a stator slot cooling.

This object is achieved by an electrical machine, in particular for a hybrid or fully electrically operable drive train of a motor vehicle, comprising a stator and a rotor which is rotatably mounted relative to the stator and has a rotor shaft and a rotor body which is non-rotatably connected to the rotor shaft, the stator having a plurality of has stator slots extending through the stator in the axial direction, in which a stator winding is accommodated, with hydraulic fluid being able to flow through the stator slots, with at least one pump disk being non-rotatably coupled to the rotor in such a way that the pump disk is designed as a hollow shaft and connected to the Hydraulic fluid fillable rotor shaft, the hydraulic fluid pressurized can be guided through the stator slots of the stator.

According to the invention, a coolant feed pump is integrated in the electrical machine via the pump disk connected to the rotor, as a result of which a very compact design of an electrical machine with hydraulic slot cooling can be implemented. The pump disk and the rotor thus form a radial pump, for example. For this purpose, a pump disk is attached to the hollow shaft of the rotor, which carries a hydraulic fluid such as oil.

By rotating the hollow shaft during operation of the electrical machine, the pump disk is also rotated. Due to, for example, bores, channels or grooves on and/or in the pump disk, the hydraulic fluid is transported radially outwards through the pump disk under the effect of centrifugal force. As a result, the hydraulic fluid is conveyed from the hollow shaft to the inlets of the stator slots. A pressure is built up there, which forces the hydraulic fluid through the cooling grooves of the stator. After the hydraulic fluid has exited after flowing through the stator slots, the hydraulic fluid can be cooled, e.g. by a heat exchanger, after which the hydraulic fluid can then be returned to the hollow shaft again, so that a closed hydraulic circuit can be implemented.

In particular, the pump disk is operatively connected to the stator slots and hydraulically encapsulated in such a way that the hydraulic fluid can flow radially from the impeller to the stator slots to be cooled. Furthermore, the impeller is arranged sealed in the electrical machine that the rotor and the air gap between rotor and stator run dry

Further advantages of the electrical machine according to the invention are the structural simplicity of the proposed solution and the low costs associated therewith. Furthermore, the hydraulic fluid can be distributed uniformly over the entire radial cross section of the stator.

The rotor shaft is preferably designed as a hollow shaft, in which case the hydraulic fluid is routed through the rotor shaft. In this context, it is particularly preferred that radial through-openings are made in the rotor shaft, so that the hydraulic fluid is guided from the hollow shaft through the through-openings to a radial inner diameter of the pump disk and into the channels of the pump disk. Due to a rotation of the rotor shaft and a resulting rotation of the channels, the hydraulic fluid is moved outwards in the direction of circulation and also in the radial direction due to the centrifugal force.

In connection with the invention, the electrical machine can be designed as a radial or axial flow machine. In order to form an axially particularly compact axle drive train, preference should be given to axial flow machines.

The electrical machine is particularly preferably configured as a radial flux machine. The stator of a radial flow machine is usually constructed cylindrically and generally consists of electrical laminations that are electrically insulated from one another and are constructed in layers and packaged to form laminated cores. Distributed over the circumference, grooves or peripherally closed recesses are let into the electrical lamination running parallel to the rotor shaft and accommodate the stator winding or parts of the stator winding. Depending on the construction towards the surface, the slots can be closed with locking elements such as locking wedges or covers or the like in order to prevent the stator winding from being detached.

A stator winding is an electrically conductive conductor whose length is significantly greater than its diameter. In principle, the stator winding can have any desired cross-sectional shape. Rectangular cross-sectional shapes are preferred, since they can be used to achieve high packing densities and consequently high power densities. A stator winding made of copper is very particularly preferably formed. A stator winding preferably has insulation. To insulate the stator winding, for example, mica paper, which for mechanical reasons can be reinforced by a glass fabric carrier, can be wound in the form of a strip around one or more stator windings, which are impregnated with a hardening resin are. In principle, it is also possible to use a hardenable lacquer layer without mica paper in order to insulate a stator winding.

In particular, the stator can comprise a one-piece or segmented stator body. A one-piece stator body is characterized in that the entire stator body is formed in one piece, viewed circumferentially. The stator body is generally formed from a large number of stacked, laminated electrical laminations, each of the electrical laminations being closed to form a circular ring. A segmented stator body is characterized in that it is made up of individual stator segment parts. The stator body can be made up of individual stator teeth or stator tooth groups, with each individual stator tooth or each individual stator tooth group being formed from a large number of stacked, laminated electrical laminations, with each of the electrical laminations being designed as a stator segment sheet metal part.

The electrical machine is intended in particular for use within an electrically operable drive train of a motor vehicle. In particular, the electrical machine is dimensioned in such a way that vehicle speeds of more than 50 km/h, preferably more than 80 km/h and in particular more than 100 km/h can be achieved. The electric motor particularly preferably has an output of more than 30 kW, preferably more than 50 kW and in particular more than 70 kW. Furthermore, it is preferred that the electrical machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, very particularly preferably greater than 12,500 rpm.

According to an advantageous embodiment of the invention, it can be provided that the pump disk has a plurality of radially extending channels, which are hydraulically connected at their respective radially inner end to the interior of the hollow shaft.

According to a further preferred further development of the invention, it can also be provided that the pump disk has at least four essentially identical channels distributed equidistantly over the circumference of the pump disk.

Furthermore, according to a likewise advantageous embodiment of the invention, provision can be made for a plurality of pump disks to be connected to the rotor in a torque-proof manner.

According to a further particularly preferred embodiment of the invention, provision can be made for the plurality of pump disks to be of essentially identical design.

Furthermore, the invention can also be further developed such that the hollow shaft is connected to a fluid circuit at least on one side.

In a likewise preferred embodiment variant of the invention, it can also be provided that the stator is connected to a fluid circuit at least on one side.

It can also be advantageous to further develop the invention such that the stator, the rotor and the at least one pump disk of the electrical machine are accommodated in a motor housing and form a structural unit. The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics. The motor housing can also be part of a cooling system for the electric machine and can be designed in such a way that cooling fluid can be supplied to the electric machine via the motor housing and/or the heat can be dissipated to the outside via the housing surfaces. In addition, the motor housing protects the electrical machine and any electronics that may be present from external influences.

A motor housing can be formed in particular from a metallic material. Advantageously, the motor housing can be formed from a cast metal material, such as gray cast iron or cast steel. In principle, it is also conceivable to form the motor housing entirely or partially from a plastic.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that a heat sink, in particular a heat exchanger, is arranged in the fluid circuit.

Finally, the invention can also be implemented in an advantageous manner in that the pump disk is designed in the manner of a cylinder ring and has a diameter that is smaller than the diameter of the rotor body.

The invention will be explained in more detail below with reference to figures without restricting the general inventive idea.

• 1 eine elektrische Maschine in einer schematischen Axialschnittansicht, und
• 2 ein Kraftfahrzeug mit einer elektrischen Maschine.

Show it:

• 1 an electrical machine in a schematic axial section view, and
• 2 a motor vehicle with an electric machine.

the 1 shows an electric machine 1, in particular for a hybrid or fully electrically operable drive train 2 of a motor vehicle 3, as exemplified in FIG 2 is sketched.

The electrical machine 1 comprises a stator 4 and a rotor 5 which is rotatably mounted relative to the stator 4 and has a rotor shaft 8 and a rotor body 9 which is non-rotatably connected to the rotor shaft 8. The stator 4 has a multiplicity of stator slots which extend through the stator 4 in the axial direction 6, in each of which a stator winding 7 is accommodated and wherein the stator slots 6 can be flowed through by a hydraulic fluid 10.

A pump disk 11 is coupled in a rotationally fixed manner to the rotor 5 and is designed such that the hydraulic fluid 10 can be guided under pressure through the stator slots 6 of the stator 4 from the rotor shaft 8 designed as a hollow shaft 13 and which can be filled with the hydraulic fluid 10 . For this purpose, the pump disk 11 has a plurality of radially running channels 12 which are hydraulically connected to the interior of the hollow shaft 13 at their respective radially inner end. In the embodiment shown, the pump disk 11 has four essentially identical channels 12 distributed equidistantly over the circumference of the pump disk 11.

The figure also shows that the stator 4, the rotor 5 and the pump disk 11 of the electric machine 1 are accommodated in a motor housing 15 and form a structural unit. The pump disk 11 is designed like a cylinder ring and has a diameter that is smaller than the diameter of the rotor body 9. The cylindrical ring-shaped installation space around the pump disk 11 is hydraulically sealed in such a way that hydraulic pressure can be built up in this installation space when the electrical machine 1 is in operation. which can only degrade through the stator slots 6.

The hollow shaft 13 and the stator 4 are each connected to a fluid circuit 14 on one side. A heat sink, in particular a heat exchanger 16 , is arranged in the fluid circuit 14 .

The invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be considered as limiting but as illustrative. The following patent claims are to be understood in such a way that a mentioned feature is present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description define 'first' and 'second' feature, this designation serves to distinguish between two similar features without establishing a ranking.

Reference List

1

electric machine

2

powertrain

3

motor vehicle

4

stator

5

rotor

6

stator slots

7

stator winding

8th

rotor shaft

9

rotor body

10

hydraulic fluid

11

pump pulley

12

channels

13

hollow shaft

14

fluid circuit

15

motor housing

16

heat exchanger

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 19750675 C1 [0008]
• US4922765A [0009]
• US 2003/0002976 A1 [0010]
• US 1061206A [0010]
• US5443130A [0010]
• DE 102011004698 A1 [0010]

Claims (10)

Electrical machine (1), in particular for a hybrid or fully electrically operable drive train (2) of a motor vehicle (3), comprising a stator (4) and a rotor (5) which is rotatably mounted relative to the stator (4) and has a rotor shaft (8) and a rotor body (9) connected in a torque-proof manner to the rotor shaft (8), the stator (4) having a large number of stator slots (6) which extend through the stator (4) in the axial direction and in which a stator winding (7) is accommodated, wherein a hydraulic fluid (10) can flow through the stator slots (6), characterized in that at least one pump disk (11) is coupled to the rotor (5) in a rotationally fixed manner and is designed in such a way that the shaft (13) designed as a hollow shaft and with the rotor shaft (8), which can be filled with hydraulic fluid (10), the hydraulic fluid (10) can be guided under pressure through the stator slots (6) of the stator (4). Electrical machine (1) according to claim 1 , characterized in that the pump disc (11) has a plurality of radially extending channels (12), which is hydraulically connected at its respective radially inner end to the interior of the hollow shaft (13). Electrical machine (1) according to claim 1 or 2 , characterized in that the pump disk (11) has at least four substantially identical channels (12) distributed equidistantly over the circumference of the pump disk (11). Electrical machine (1) according to one of the preceding claims, characterized in that a plurality of pump disks (11) are connected to the rotor (5) in a torque-proof manner. Electrical machine (1) according to claim 4 , characterized in that the plurality of pump discs (11) are substantially identical. Electrical machine (1) according to one of the preceding claims, characterized in that the hollow shaft (13) is connected to a fluid circuit (14) at least on one side. Electrical machine (1) according to one of the preceding claims, characterized in that the stator (4) is connected to a fluid circuit (14) at least on one side. Electrical machine (1) according to one of the preceding claims, characterized in that the stator (4), the rotor (5) and the at least one pump disk (11) of the electrical machine (1) are accommodated in a motor housing (15) and a form a structural unit. Electric machine (1) according to any of the previous ones Claims 6 - 8th , characterized in that in the fluid circuit (14) a heat sink, in particular a heat exchanger (16) is arranged. Electrical machine (1) according to one of the preceding claims, characterized in that the pump disk (11) is designed in the manner of a cylindrical ring and has a diameter which is smaller than the diameter of the rotor body (9).

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