DE102019208304A1 - Heat sink for an electrical machine - Google Patents

Abstract

The present invention relates to a heat sink (30) for cooling an electrical machine (10), having: a hollow cylindrical basic shape; a first axially extending and radially extending cooling fin (34) to allow heat exchange; a fluid channel (32) to enable a heat exchange with a cooling fluid (28), the fluid channel having an opening at each of its ends in order to enable a fluid exchange of the fluid channel; a cylindrical recess, the diameter of which is in sections larger than a diameter of an output shaft (12) of the electrical machine, in order to partially accommodate the output shaft in the heat sink; and a connecting section (36) to connect the output shaft of the electrical machine to the heat sink in a rotationally fixed manner, the cooling rib being designed to be arranged non-rotatably on a rotor (14) of the electric machine so that the heat sink between the rotor and the output shaft of the electric Machine is arranged to cool the electrical machine and the output shaft of the electrical machine. The present invention also relates to an electrical machine (10) with such a heat sink and a system (20) for cooling such an electrical machine.

Description

The present invention relates to a heat sink for an electrical machine, an electrical machine and a system for cooling an electrical machine.

Vehicles are increasingly being equipped with hybrid drives or pure electric drives. Hybrid drives can help reduce fuel consumption and pollutant emissions. Drivetrains with an internal combustion engine and one or more electric motors as parallel hybrids or mixed hybrids have largely become established. Since the drive torques of the electric drive and the internal combustion engine can add up depending on the control, a comparatively smaller design of the internal combustion engine and / or its temporary shutdown is possible. This enables a significant reduction in CO2 emissions to be achieved without any significant loss of performance or comfort. Pure electric vehicles can sometimes be operated with no significant emissions.

In particular when using electrical machines that can reach very high speeds, for example in the range of 20,000 revolutions per minute, the components of the electrical machines are exposed to enormous loads and high temperatures. It is therefore known to limit the energy supplied to an electrical machine in order to prevent excessive heating and associated damage to the electrical machine. However, this means that the electrical machine cannot utilize its full potential.

It is also known to cool the electrical machine by means of cooling fins arranged on its housing or a water cooling system arranged on the housing. Such cooling is not very efficient because the cooling takes place at a great distance from the heat source.

From the DE 10 2011 007 254 A1 a drive device is known with at least one housing and at least one electric drive. The electric drive has a rotor arrangement with a rotor shaft which is designed for rotation about an axis of rotation. A bearing arrangement is provided for supporting the rotor arrangement, the bearing arrangement supporting the rotor arrangement radially inward with respect to the axis of rotation and the bearing arrangement supporting the rotor shaft against a support section fixed to the housing. The rotor shaft can have several channel sections which extend in the axial direction and which are preferably regularly distributed in the direction of rotation around the axis of rotation and are designed to cool the rotor shaft, in particular the bearing arrangement or the bearing device. The disadvantage here is that only cooling with gear oil is provided. Furthermore, cooling the electrical machine by means of gear oil is not very efficient, since the gear oil initially cools the bearings which are supported radially on the inside and can therefore absorb less heat from the electrical machine.

From the DE 602 25 725 T2 there is known a magnetic bearing spindle used as a machine tool spindle. The spindle rotates at speeds of up to 70,000 rpm. A peripheral portion of the thrust magnetic bearing rotor is formed in a triangular shape that reduces a variation rate of a pipe resistance or a pipe strength. This is intended to prevent a vortex from being generated so that cooling air can gently pass through the gap in such a way that the cooling air can evenly divide or separate and flow in a load direction and a counterload direction. The disadvantage here is that the magnetic bearing spindle is cooled exclusively by an air stream. A cooling described above is not suitable for lower rotational speeds, which are used, for example, in electric drive machines for motor vehicles. Furthermore, such a spindle cannot be cooled by means of a liquid cooling fluid, or can only be cooled with great technical effort.

In general, it is desirable to cool an electrical machine as efficiently as possible in order to keep a restriction on the energy supplied to the electrical machine as low as possible. Limiting the energy supplied is associated with a loss in the efficiency of the electrical machine. Various operating modes are provided, particularly in the case of electrical machines for motor vehicles. For example, the electrical machine can be operated in a recuperation mode. In this mode, a low efficiency of the electrical machine leads to a loss in energy recovery. As a result, part of the almost freely available energy cannot be recovered and used. It is therefore of particular interest to increase the efficiency of an electrical machine, in particular an electrical machine for a motor vehicle.

Against this background, the object of the present invention is to create a way of improving the cooling of an electrical machine. In particular, a device is to be created which enables cooling with a small distance from the heat source.

• einer hohlzylindrischen Grundform;
• einer ersten axial verlaufenden und sich radial erstreckenden Kühlrippe, um einen Wärmeaustausch zu ermöglichen;
• einem Fluidkanal, um einen Wärmeaustausch mit einem Kühlfluid zu ermöglichen, wobei der Fluidkanal an seinen Enden jeweils eine Öffnung aufweist, um einen Fluidaustausch des Fluidkanals zu ermöglichen;
• einer zylindrischen Aussparung, deren Durchmesser abschnittsweise größer ist als ein Durchmesser einer Ausgangswelle der elektrischen Maschine, um die Ausgangswelle teilweise in dem Kühlkörper aufzunehmen; und
• einem Verbindungsabschnitt, um die Ausgangswelle der elektrischen Maschine drehfest mit dem Kühlkörper zu verbinden, wobei
• die Kühlrippe dazu ausgebildet ist, drehfest an einem Rotor der elektrischen Maschine angeordnet zu werden, sodass der Kühlkörper zwischen Rotor und Ausgangswelle der elektrischen Maschine angeordnet ist, um die elektrische Maschine und die Ausgangswelle der elektrischen Maschine zu kühlen.

To achieve the object, the invention relates to a heat sink for cooling an electrical machine, with:

• a hollow cylindrical basic shape;
• a first axially extending and radially extending cooling fin to enable heat exchange;
• a fluid channel to enable a heat exchange with a cooling fluid, the fluid channel having an opening at each of its ends in order to enable a fluid exchange of the fluid channel;
• a cylindrical recess, the diameter of which is in sections larger than a diameter of an output shaft of the electrical machine, in order to partially accommodate the output shaft in the heat sink; and
• a connecting section to connect the output shaft of the electrical machine to the heat sink in a rotationally fixed manner, wherein
• the cooling rib is designed to be arranged non-rotatably on a rotor of the electrical machine, so that the heat sink is arranged between the rotor and output shaft of the electrical machine in order to cool the electrical machine and the output shaft of the electrical machine.

• einem Stator;
• einem Rotor; und
• einer Ausgangswelle mit einem Kühlkörper wie zuvor beschrieben, wobei der Kühlkörper drehfest mit dem Rotor der elektrischen Maschine und der Ausgangswelle verbunden ist.

The invention also relates to an electrical machine with:

• a stator;
• a rotor; and
• an output shaft with a heat sink as described above, the heat sink being connected in a rotationally fixed manner to the rotor of the electrical machine and the output shaft.

• einem Fluidsumpf zum Speichern eines Kühlfluids;
• einer elektrischen Maschine wie zuvor beschrieben; und
• einer Fluidpumpe zum Fördern des Kühlfluids vom Fluidsumpf zu einem Kühlkörper der elektrischen Maschine, um einen Kühlkreislauf zu bilden.

The invention also relates to a system for cooling an electrical machine, with:

• a fluid sump for storing a cooling fluid;
• an electrical machine as previously described; and
• a fluid pump for conveying the cooling fluid from the fluid sump to a heat sink of the electrical machine in order to form a cooling circuit.

Preferred embodiments of the invention are described in the dependent claims. It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention. It is also understood that the features and advantages mentioned here can be used in any electrical machine, regardless of its intended use.

Cooling fluid can be conducted through the electrical machine at a high flow rate through a fluid channel. A temperature gradient between the cooling fluid and the electrical machine is high. The cooling of the electrical machine by means of cooling fluid is efficient. A further fluid channel can be formed with the rotor of the electrical machine by a cooling rib. The cooling of the electrical machine is further improved. Heat can be dissipated directly from inside the electrical machine. The cooling of the electrical machine is technically simple and efficient. By arranging the heat sink between the rotor and the output shaft of the electrical machine, such an electrical machine can be constructed in a technically simple manner and with few parts. Cooling with air and with cooling fluid is possible.

In a preferred embodiment, the fluid channel runs in the axial direction in sections parallel to the output shaft of the electrical machine. In this way, cooling fluid can be brought close to the rotor of the electrical machine. The cooling is efficient. Furthermore, a high flow rate of the cooling fluid is achieved, so that a higher throughput of fresh or cold cooling fluid is achieved. The optimal fluid velocity can be calculated in CFD (Computational Fluid Dynamics), whereby a slower velocity is sometimes better, since the fluid has more time to absorb the heat and the pressure loss is minimized.

In an advantageous embodiment, the heat sink is made of metal. The cooling fin is preferably forged. In this way, the production of the heat sink is technically simple and inexpensive. A good coefficient of thermal conductivity is achieved.

In an advantageous embodiment, the first cooling rib is formed by two grooves running parallel in the axial direction. The grooves run parallel to a plane containing the central axis of the heat sink. By designing the cooling fins in this way, the cooling fins can be manufactured in a technically simple manner, since a tool which, for example, machining or forging does not have to be turned during the production of the cooling body. Furthermore, the heat sink does not have to be rotated, so that rapid machining of the heat sink is possible.

In an advantageous embodiment, the cooling body has, at one axial end in its radially inner region, the connecting section with driving teeth in order to be connected to the output shaft in a rotationally fixed manner. In this way, a non-rotatable connection between the heat sink and the output shaft can be created cost-effectively. Furthermore, production of the heat sink and assembly of the heat sink are simplified, since the output shaft can simply be plugged or pressed into the heat sink in order to form an output shaft including a heat sink for an electrical machine.

In an advantageous embodiment, the heat sink has at least one second cooling rib. The fluid channel runs in sections through the first cooling fin. Additionally or alternatively, a width of the first cooling fin is different from a width of the second cooling fin. The width of the first cooling fin is preferably greater than the width of the second cooling fin. As a result, cooling can take place efficiently, since the first cooling fin allows both cooling by means of air and cooling by means of cooling fluids. The second cooling fin can be optimized for cooling with air by means of different widths of the cooling fins.

In an advantageous embodiment, the section of the fluid channel running parallel to the output shaft of the electrical machine is formed by a blind hole in the heat sink and is closed in a fluid-tight manner at one end with a sealing plug. This makes the production of the heat sink technically simple and quick.

In an advantageous embodiment, the heat sink has fastening means on an axial end section, preferably in the form of threaded bores, in order to fasten a fan wheel to the heat sink in a rotationally fixed manner. In this way, a fan wheel can be arranged on the heat sink in order to generate an air flow along the cooling fins when the electrical machine is in operation. The cooling of the electrical machine is further improved. In particular, a residual cooling capacity is guaranteed even if a fluid supply fails.

In a preferred embodiment, a radially inner surface of the cooling body forms a gap with the output shaft of the electrical machine, which gap serves as an outlet for the cooling fluid. The gap opens into a feed line to a fluid sump. In this way, an outflow for the heated cooling fluid can be created in a technically simple manner. By directing the cooling fluid into a feed line to a fluid sump, a cooling circuit can be created. Furthermore, heated and moving cooling fluid can settle in a fluid sump. Any bubbles that have formed in the cooling fluid can migrate upwards due to their lower density. When the cooling fluid is sucked in again from the fluid sump by means of a fluid pump and cooled again, fewer splashing losses and a high cooling capacity are possible.

In an advantageous embodiment, the electrical machine has a transmitter wheel, the transmitter wheel being designed to rotate with the output shaft and comprising a bore in order to supply cooling fluid through the transmitter wheel to the heat sink. In this way, the speed and the direction of rotation of the electrical machine can be monitored in a technically simple and reliable manner, with a supply of cooling fluid to the output shaft of the electrical machine being ensured.

In a further advantageous embodiment, the heat sink is connected in a rotationally fixed manner to the rotor of the electrical machine by means of a press fit. In this way, a non-rotatable connection of the heat sink to the rotor of the electrical machine can be created cost-effectively.

In an advantageous embodiment, the electrical machine is designed to be operatively connected to a transmission on the output shaft. The electrical machine preferably has a gap with a heat sink as previously defined. The gap is designed to supply cooling fluid to the transmission in order to lubricate and / or cool the transmission. In this way, it is technically easy to cool and lubricate the operatively connected gear. Additional lubrication and cooling of the transmission can preferably be dispensed with.

In an advantageous embodiment, the system for cooling the electrical machine has a heat exchanger in order to extract heat from the cooling fluid. The heat exchanger is preferably arranged in the fluid flow direction between the fluid sump and the fluid pump. The system preferably has a fan wheel on the heat sink of the electrical machine in order to generate an air flow during operation of the electrical machine and to cool the electrical machine. In this way, the cooling of the electrical machine can be further improved. Additional heat can be extracted from the cooling fluid. In addition, fail-safe air cooling can be created that causes a kind of forced ventilation of the heat sink when the electrical machine is in operation.

Cooling fluids come in many different compositions, depending on the location and area of use. For example, a mineral oil and / or synthetic oil, with or without additives, can be used. It is also conceivable to use water, in particular deionized water, with or without additives. Alcohols or ethers can also be used as cooling fluids with or without additives. In principle, any gas or any liquid, depending on the intended use, can be used as a cooling fluid. There is one over the entire temperature range liquid or flowable substance can be used as a cooling fluid.

Recuperation is the recovery of energy during braking. A recuperation brake, also called regenerative brake, works like any electrodynamic brake without wear. The braking effect is achieved by operating the traction motors as electrical generators. The electrical energy can be stored in the vehicle, for example in an accumulator or high-performance capacitor.

An encoder wheel is a device for generating a signal that correlates with the angular or rotational position of the encoder wheel. For example, an angle or speed signal can be generated on the basis of periodic gaps in a toothed ring or by means of an induction transmitter based on the changes in the magnetic field. A uniform tooth structure corresponds to a sinusoidal stress curve. Furthermore, a specific gear wheel position can be transmitted to a control unit by using gaps of different sizes at specific intervals, which results in a change in the voltage curve. An optical determination of the angular position or speed is also conceivable, for example by means of the teeth of a toothed wheel that pass through a light barrier.

Splash losses are efficiency losses due to rotating components which at least partially run in a fluid. This leads to impairments in the cooling properties of a cooling fluid, which occur due to contamination, preferably air bubbles. The impurities usually have poorer thermal properties than the cooling fluid, so that a contaminated cooling fluid can absorb less heat. Furthermore, if the cooling fluid is contaminated by air inclusion, the viscosity of the cooling fluid can change, so that a fluid pump works less efficiently.

• 1 eine schematische Darstellung einer elektrischen Maschine gemäß der vorliegenden Erfindung;
• 2 eine schematische Darstellung eines Kühlsystems gemäß der vorliegenden Erfindung;
• 3 eine schematische Detaildarstellung des Kühlkörpers der elektrischen Maschine;
• 4 eine perspektivische technische Zeichnung eines Kühlkörpers;
• 5 eine perspektivische technische Schnittzeichnung eines Kühlkörpers;
• 6 eine perspektivische technische Schnittzeichnung einer elektrischen Maschine mit einem Kühlkörper; und
• 7 eine technische Schnittzeichnung einer elektrischen Maschine mit einem Kühlkörper.

The invention is described and explained in more detail below with reference to a few selected exemplary embodiments in conjunction with the accompanying drawings. Show it:

• 1 a schematic representation of an electrical machine according to the present invention;
• 2 a schematic representation of a cooling system according to the present invention;
• 3 a schematic detailed representation of the heat sink of the electrical machine;
• 4th a perspective technical drawing of a heat sink;
• 5 a perspective technical sectional drawing of a heat sink;
• 6th a perspective technical sectional drawing of an electrical machine with a heat sink; and
• 7th a technical sectional drawing of an electrical machine with a heat sink.

In 1 is schematically an electrical machine 10 shown. The electric machine 10 has an output shaft 12th on that with a rotor 14th the electrical machine is rotatably connected. A stator 16 the electric machine 10 is with a housing 18th non-rotatably connected. It goes without saying that the stator 16 also with another component that rotates the stator 16 relative to the rotor 14th prevented, can be effectively connected. The illustration is to be understood as an example; the components are not true to scale. Furthermore, no further details are presented.

When the electrical machine is in operation 10 the rotor turn 14th and the output shaft 12th with the same rotation speed. The stator 16 is with the case 18th connected in such a way that it performs essentially no movement, in particular no rotational movement. The electric machine 10 can be a direct current, alternating current, three phase alternating current machine. In general, the invention can be used with any electrical machine that has an output shaft.

In 2 is schematically a system 20th for cooling the electrical machine 10 shown. The system 20th includes a fluid sump 22nd , a fluid pump 24 and lines 26th .

The fluid pump 24 promotes cooling fluid 28 from the fluid sump 22nd into the output shaft 12th the electric machine 10 . The cooling fluid 28 takes heat from the electrical machine 10 on. By further conveying cooling fluid 28 becomes the cooling fluid 28 from the output shaft 12th the electric machine 10 pushed and flows back into the fluid sump 22nd .

The fluid pump 24 can be any type of pump that is suitable for pumping cooling fluid. It is understood that in the system 20th one or more heat exchangers can be provided to the cooling fluid 28 improves cooling. In addition, a fluid filter can be provided to remove suspended matter from the cooling fluid 28 to filter. One or more temperature sensors can also be provided to measure the temperature of the electrical machine 10 and / or the cooling fluid 28 capture. It is conceivable, the fluid pump 24 depending on the temperature of the electrical machine 10 and / or the cooling fluid 28 to regulate. The representation is to be understood as a functional minimal scheme. It is also conceivable that the fluid pump 24 operated another cooling circuit.

In 3 is a schematic detailed view of the electrical machine 10 shown. The output shaft 12th has a heat sink 30th with a fluid channel 32 and a first cooling fin 34 on. The heat sink 30th is at a connection section 36 with the output shaft 12th non-rotatably connected. The heat sink 30th has a transmitter wheel at a first axial end 38 on. The heat sink surrounds a second axial end opposite the first end 30th the output shaft 12th and forms with the output shaft 12th a crack 40 used as a drain for cooling fluid 28 from the heat sink 30th serves.

The encoder wheel 38 is on the output shaft 12th arranged to the speed of the output shaft 12th and thus the speed of the rotor 14th the electric machine 10 to determine. The encoder wheel 38 has a recess to over the transmitter wheel 38 the heat sink 30th Cooling fluid 28 feed.

4th shows a schematic perspective illustration of a heat sink 30th . The heat sink 30th has a first cooling fin 34 and a second cooling fin 42 on. Furthermore, the heat sink 30th grooves running in the axial direction 44 on that the cooling fins 34 , 42 form. The heat sink 30th points in the first cooling fin 34 a fluid channel 32 on. Depending on the requirements for cooling performance and the torque to be transmitted, the thickness of the cooling fins 34 , 42 or the width of the grooves 44 be adjusted. The cooling fins 34 , 42 have different radial dimensions. Furthermore, the cooling fins 34 , 42 arranged essentially in parallel. The cooling fins 34 , 42 do not lead radially to the center of the heat sink 30th down. This allows the production of the heat sink 30th can be done quickly and cost-effectively as there is no rotation of a tool and / or the heat sink 30th when machining the grooves 44 or cooling fins 34 , 42 must take place.

5 shows a schematic perspective sectional illustration of the heat sink 30th . A section of the fluid channel 32 that is parallel to the output shaft 12th runs, is formed in the example shown as a blind hole. Two obliquely running bores lead to the blind hole in order to feed and discharge cooling fluid 28 to enable. Due to the parallel to the output shaft 12th running section and the obliquely running bores towards the blind hole can be a fluid channel 32 be created that allows cooling fluid 28 close to the rotor 14th the electric machine 10 respectively.

In 6th is a perspective sectional view through an electrical machine 10 shown in detail. The electric machine 10 has an output shaft 12th on that with the heat sink 30th at the connecting portion 36 is rotatably connected. The heat sink 30th has the encoder wheel at a first axial end 38 on, the sections in the heat sink 30th is added and with the heat sink 30th turns. At an axial end opposite the first axial end is a fan wheel 46 non-rotatably with the heat sink 30th connected. When the electrical machine is in operation 10 is caused by the rotating fan wheel 46 a flow of air through the heat sink 30th generated through. The output shaft 12th is with a gear not shown in detail 48 operatively connected and forms with the heat sink 30th the gap 40 that acts as a drain for the cooling fluid 28 serves.

In 7th is a sectional view through an electrical machine 10 shown in detail. When operating the electrical machine 10 becomes cooling fluid 28 , preferably oil, from the fluid pump 24 from the fluid sump 22nd sucked in. The fluid pump 24 brings the cooling fluid 28 through lines 26th and hydraulic fittings back into the heat sink 30th . Between the sender wheel 38 that deals with the output shaft 12th , the heat sink 30th and the rotor 14th turns, and a rigid bearing cap 50 there is a seal. For example, a radial shaft sealing ring or a combination of sealing ring and baffle plate can be provided.

The cooling fluid 28 flows through a hole in the bearing cap 50 inside the sender wheel 38 . From there it gets through several holes in the sender wheel 38 into a space between the output shaft 12th and heat sink 30th brought. From there the cooling fluid 28 Via an inclined hole in another longitudinal hole in the heat sink 30th located close to the surface. This causes a good heat transfer from the electrical machine 10 into the cooling fluid 28 can take place. The longitudinal bore is designed in the form of a blind bore and, for example, with a sealing plug 52 against the space of the electric machine 10 sealed.

After flowing through the longitudinal bore, the cooling fluid arrives 28 again in the space between the output shaft 12th and heat sink 30th and from there back into the fluid sump 22nd .

The electric machine 10 also has air cooling. Here is the fan wheel 46 to the heat sink 30th screwed or otherwise non-rotatably connected to it. The fan wheel 46 rotates accordingly with a speed of the heat sink 30th and blows air through the air channels (grooves 44 ) in the heat sink. The air heated in this way transfers the heat to other housing parts of a motor housing. For improved heat dissipation from the air, the housing can be provided with housing ribs etc. in order to create a large surface area and thus ultimately to be able to give off heat to the environment more quickly. The air ducts (grooves 44 ) in the heat sink 30th can be forged, for example, and do not necessarily have to be machined.

The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as examples and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art after using the present invention and after carefully analyzing the drawings, the disclosure and the following claims.

In the claims, the words “comprising” and “having” do not exclude the presence of further elements or steps. The undefined article “a” or “an” does not exclude the presence of a plural. The mere mention of some measures in several different dependent patent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the claims are not to be understood as restrictive.

List of reference symbols

10

electric machine

12

Output shaft

14th

rotor

16

stator

18th

casing

20th

system

22nd

Fluid sump

24

Fluid pump

26th

management

28

Cooling fluid

30th

Heat sink

32

Fluid channel

34

first cooling fin

36

Connection section

38

Encoder wheel

40

gap

42

second cooling fin

44

Groove

46

Fan wheel

48

transmission

50

Bearing cap

52

Sealing plug

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed 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 102011007254 A1 [0005]
• DE 60225725 T2 [0006]

Claims (15)

Heat sink (30) for cooling an electrical machine (10), with: a hollow cylindrical basic shape; a first axially extending and radially extending cooling fin (34) to allow heat exchange; a fluid channel (32) to enable a heat exchange with a cooling fluid (28), the fluid channel having an opening at each of its ends in order to enable a fluid exchange of the fluid channel; a cylindrical recess, the diameter of which is in sections larger than a diameter of an output shaft (12) of the electrical machine, in order to partially accommodate the output shaft in the heat sink; and a connecting section (36) to connect the output shaft of the electrical machine to the heat sink in a rotationally fixed manner, wherein the cooling rib is designed to be arranged non-rotatably on a rotor (14) of the electrical machine, so that the heat sink is arranged between the rotor and the output shaft of the electrical machine in order to cool the electrical machine and the output shaft of the electrical machine. Heat sink (30) Claim 1 wherein the fluid channel (32) runs in the axial direction in sections parallel to the output shaft (12) of the electrical machine (10). Cooling body (30) according to one of the preceding claims, wherein the cooling body is formed from metal and the first cooling rib (34) is preferably forged. Heat sink (30) according to one of the preceding claims, wherein the first cooling rib (34) is formed by two grooves (44) running parallel in the axial direction; and the grooves run parallel to a plane containing the central axis of the heat sink. Cooling body (30) according to one of the preceding claims, wherein the cooling body has the connecting section (36) with driving teeth at one axial end in its radially inner region in order to be connected to the output shaft (12) in a rotationally fixed manner. Cooling body (30) according to one of the preceding claims, with at least one second cooling rib (42), wherein the fluid channel (32) runs in sections through the first cooling rib (34); and or a width of the first cooling fin is different from a width of the second cooling fin and preferably greater than the width of the second cooling fin. Heat sink (30) according to one of the preceding claims, wherein the section of the fluid channel (32) running parallel to the output shaft (12) of the electrical machine (10) is formed by a blind hole in the heat sink and at one end with a sealing plug (52) is closed fluid-tight. Heat sink (30) according to one of the preceding claims, wherein the heat sink has fastening means, preferably in the form of threaded bores, at an axial end section in order to fasten a fan wheel (46) in a rotationally fixed manner to the heat sink. Heat sink (30) according to the preceding claim, wherein a radially inner surface of the heat sink with the output shaft (12) of the electrical machine forms a gap (40) which serves as an outlet for the cooling fluid (28); and the outflow opens into a feed line to a fluid sump (22). An electric machine (10) comprising: a stator (16); a rotor (14); and an output shaft (12) with a heat sink (30) according to one of the Claims 1 to 9 , wherein the heat sink is rotatably connected to the rotor of the electrical machine and the output shaft. Electric machine (10) according to Claim 10 , with a transmitter wheel (38), wherein the transmitter wheel is designed to rotate with the output shaft (12) and comprises a bore to supply cooling fluid through the transmitter wheel to the heat sink (30). Electric machine (10) according to one of the Claims 10 or 11 , wherein the heat sink (30) is non-rotatably connected to the rotor (14) of the electrical machine by means of a press fit. Electric machine (10) according to one of the Claims 10 to 12th , wherein the electrical machine is designed to be operatively connected to a gear (48) on the output shaft (12) and a heat sink (30) after Claim 9 comprises, wherein the gap (40) is designed to supply cooling fluid (28) to the gearbox in order to lubricate and / or cool the gearbox. A system (20) for cooling an electrical machine (10), comprising: a fluid sump (22) for storing a cooling fluid (28); an electrical machine according to one of the Claims 10 to 13th ; and a fluid pump (24) for conveying the cooling fluid from the fluid sump to a heat sink (30) of the electrical machine in order to form a cooling circuit. System (20) according to the preceding claim, having a heat exchanger in order to extract heat from the cooling fluid (28), the heat exchanger preferably being arranged in the fluid flow direction between the fluid sump (22) and the fluid pump (24); and the system preferably comprises an electrical machine (10) having a heat sink (30) Claim 8 and a fan wheel (46) to generate an air flow during operation of the electrical machine and to cool the electrical machine.

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