Electric machine with actively cooled adsorption element

Abstract

An electric machine (1, 1a, 1b) is described, comprising a machine housing (2), a stator (6) arranged in the machine housing (2), and a rotor (9) rotatably mounted in the machine housing (2) relative to the stator (6). The machine housing (2) encloses an interior space (B) of the electric machine (1, 1a, 1b) and separates it from an exterior space (C). Furthermore, the electric machine (1, 1a, 1b) includes an adsorption element (19) arranged in the interior space (B), which can be actively cooled below the condensation point of the air in the interior space (B) for absorbing water vapor or water. A vehicle (29) with such an electric machine (1, 1a, 1b) and a method for operating such an electric machine (1, 1a, 1b) are also described.

Description

TECHNICAL AREA The invention relates to an electric machine with a machine housing that surrounds an interior space of the electric machine and separates it from an exterior space, as well as with a stator and a rotor rotatably arranged relative to the stator, which are located in the interior space. Furthermore, the invention relates to a vehicle with such an electric machine and to a method for operating such an electric machine. STATE OF THE ART Such an electric machine, such a vehicle, and such a process are fundamentally known from the prior art. The problem is that moisture entering the interior during the manufacture and / or operation of the electric machine can condense on its components and cause damage. Condensation occurs particularly when the electric machine cools down during a break in operation and when it is used in a humid (foggy) environment. REVELATION OF THE INVENTION One object of the invention is therefore to provide an improved electric machine, an improved vehicle, and an improved method for operating an electric machine. In particular, the humidity inside the electric machine should be kept within a favorable range, and specifically, condensation of moisture on components of the electric machine inside its interior should be prevented or at least reduced. The object of the invention is solved with an electric machine of the type mentioned at the outset, which additionally comprises an adsorption element arranged in the interior space and which can be actively cooled below a condensation point of air located in the interior space for the absorption of water vapor or water. The electric machine can be part of a drive unit that also includes a gearbox coupled to the electric machine. The interior of the electric machine can be connected to the interior of the gearbox. Furthermore, the problem of the invention is solved with a vehicle equipped with such an electric machine which is intended to propel the vehicle. Finally, the object of the invention is achieved by a method for operating such an electric machine, wherein the adsorption element, when actively cooled below the condensation point of the air in the interior, absorbs water vapor or water by adsorption. For this purpose, the adsorption element is actively cooled, whereby the surface temperature of the adsorption element is at least temporarily lower than the dew point temperature of the air in the interior. In particular, the adsorption element is cooled to a temperature that is lower than the temperature of other components or surfaces in the interior. The proposed measures enable the repeated drying of the air inside the electric machine, either in a closed loop or by removing condensed liquid (water) from the interior. This allows the humidity inside the electric machine to be maintained within a favorable range. In particular, the proposed measures prevent or at least reduce condensation on components within the electric machine, thereby preventing or at least reducing damage to these components. The proposed measures are particularly advantageous when the interior of the electrical machine is connected to the exterior via a pressure equalization opening or device, which allows for pressure equalization and, in particular, a (controlled) exchange of air between the interior and exterior. However, moisture can still enter the interior of the electrical machine through this pressure equalization opening or device even after its manufacture. In this case, the adsorption element can also reduce or prevent condensation of moisture on components of the electrical machine within its interior. Optionally, the pressure equalization device has an internal section that is part of the interior of the electric machine, with the adsorption element located in this internal section. This allows the adsorption element to be integrated into the electric machine in a particularly space-saving manner. Adsorption is the process by which molecules or ions from a gas or liquid phase are bound to the interface or surface of a solid material. This binding occurs in the liquid or solid state. In the case of water, water vapor or water droplets dispersed in the air can bind to the interface of a body as water or ice. It should be noted that adsorption can also occur inside an absorption element, for example, when water binds to the inner surface of a porous absorption element. However, this form of adsorption within the context of absorption is not what is meant by "adsorption" in the context of the invention. Instead, the invention refers specifically to the binding of water or ice (exclusively) to an outer interface of an adsorption element. For example, the adsorption element can be located on or formed by a region of the electric machine that is actively cooled during operation. Specifically, this region is cooled below the dew point temperature of the air inside the machine. The adsorption element can, for instance, be placed directly on a cooled surface of the electric machine, such as on an outer wall of the machine housing inside the machine. During operation, this region can be permeable to, or be permeated by, a liquid or vaporous heat transfer medium. Advantageously, the temperature of the other components and surfaces inside the electric machine remains above the aforementioned dew point temperature to prevent unwanted condensation away from the adsorption element. It is further advantageous if the electric machine has either a cooling channel arranged in the machine housing, on which the adsorption element is arranged, or a cooling channel arranged in an inverter of the electric machine, on which the adsorption element is arranged, with the inverter closing an opening in the machine housing. The adsorption element can, for example, be arranged on the bottom of the inverter. One possibility would be for the cooling channel to be permeated by a liquid, cooled heat transfer fluid, which would cool the adsorption element. The heat transfer fluid could be, for example, water- or oil-based. It would also be conceivable to cool the adsorption element using a cooling compressor. The cooling channel could then be traversed by a vaporous heat transfer medium (refrigerant). Furthermore, the cooling compressor could be used for other purposes, for example, to cool the interior of a vehicle in which the electric motor is installed. Generally, the adsorption element can be directly adjacent to the cooling channel, but a partition can also be located between the adsorption element and the cooling channel, the partition preferably having a thermal conductivity λ of at least 10 W / (m·K) and being made of metal, for example. In another embodiment, the adsorption element can be arranged on or formed by an electrically operated cooling element. For example, the adsorption element can be arranged on or formed by a Peltier element. In particular, a cooling compressor used to cool the adsorption element can also be electrically operated. The electric machine can also include an inverter, which is attached to the machine housing and has an internal section that is part of the interior of the electric machine. In this way, the humidity level in the internal section of the inverter can be kept within a favorable range, and condensation of moisture on the inverter components can be prevented or at least reduced. In particular, the adsorption element can be located in the internal section of the inverter. It is generally advantageous if the adsorption element protrudes into the interior of the electric machine. This gives the adsorption element a comparatively large surface area to which water or ice can adhere. It is also advantageous if the adsorption element has a grid or rib structure. This provides the adsorption element with a comparatively large surface area to which water or ice can adhere. This is particularly beneficial for an adsorption element that protrudes into the interior of the electric machine. Furthermore, it is advantageous if the adsorption element is located in an area of ​​the electric machine that is surrounded by air flowing from the interior during operation. This ensures that the air to be dried is directed over the adsorption element. For example, the airflow within the interior can be caused by the rotating rotor. In particular, the airflow can also be caused by a fan, which may be driven by the rotor or have its own drive. For instance, a suitable fan wheel can be mounted on the rotor shaft. The airflow can also be caused by diffusion. In particular, the adsorption element can be a dedicated adsorption element, i.e., a separate element specifically designed for the absorption of water vapor or water from the air in the interior. Further advantageous embodiments and developments of the invention will become apparent from the dependent claims and from the description in conjunction with the figures. It is advantageous if the adsorption element is surrounded on the interior side of the electric machine by a waterproof and / or oil-tight, but water vapor-permeable barrier membrane. This prevents coolant and / or lubricant located inside the electric machine from contaminating the adsorption element and impairing its function. Furthermore, a barrier membrane that is vapor-permeable but water-impermeable can prevent condensate from flowing back into the interior of the electric machine. A barrier membrane can, for example, be made of stretched (expanded) polytetrafluoroethylene. Such a membrane has micropores with a diameter of 0.02 to 1 µm and is particularly well-known under the trade name "Gore-Tex." Another type of barrier membrane is a hydrophilic membrane through which water vapor can diffuse and which is particularly well-known under the trade name "Sympatex." It is also advantageous if the adsorption element is connected to a drain line leading from the interior to the exterior. This allows condensate (water) flowing from the adsorption element to be transported to the exterior, where it can drip or evaporate. The water can then flow away by gravity or be pumped or extracted. In one embodiment, a check valve can be installed in the drain line, allowing water to flow outwards but preventing it from flowing back. In particular, an opening in the drain line to the exterior can be located in an area where a negative pressure occurs or is expected during operation of the electric machine. This also facilitates the drainage of the water.For example, such a negative pressure can be caused by an airflow that is directly or indirectly caused by the electric machine, such as by a fan driven by the electric machine which generates the airflow in the outside space (direct causation), or also by the movement of a vehicle for which the electric machine serves as a drive (indirect causation). Furthermore, it is advantageous if the pressure equalization opening or device is integrated into or formed by the discharge line. This results in a particularly compact design for the electric machine. Additionally, due to pressure equalization, incoming air passes through the adsorption element and can thus be dried before reaching the electric machine. Several other implementation variants are conceivable for the proposed procedure.For example, the adsorption element can be: a) not cooled during operation of the electric machine and only cooled after operation of the electric machine or during an operating break; b) not cooled above a first temperature in the interior and cooled below a second, lower temperature in the interior; c) not cooled below a first relative humidity in the interior and cooled above a second, higher relative humidity in the interior; d) not cooled above a first temperature in the exterior and cooled below a second, lower temperature in the exterior; e) not cooled below a first relative humidity in the exterior and cooled above a second, higher relative humidity in the exterior; f) cooled or not cooled based on a combination of at least two of cases a) to e). For example, the adsorption element can be cooled (activated) when the electric machine is switched off or the temperature inside falls below a predetermined level. Instead of a logical OR operation, a logical AND operation can also be used. Accordingly, it can be provided that the adsorption element is cooled (activated) when the electric machine is switched off and the temperature inside falls below a predetermined level. In another embodiment, it can be provided that the adsorption element is cooled (activated) when the electric machine is operated in a cool, foggy environment, etc. The proposed method also offers the advantage that the adsorption element releases water or water vapor into the interior of the electric machine during operation and absorbs water or water vapor from the interior during periods of inactivity. This creates a cycle, and the condensate does not necessarily need to be drained from the interior of the electric machine. In other words, a drain line is not required. While the evaporation of water during operation increases the humidity in the interior, it also prevents or reduces further moisture enrichment of the interior air from outside air due to the reduced diffusion gradient.Therefore, if the adsorption element is appropriately dimensioned, its absorption of water or water vapor during periods of inactivity of the electric machine can be sufficient to prevent or at least reduce condensation of water on (other) components of the electric machine. The absorption of water vapor or water is achieved through active cooling of the adsorption element, while the release of water vapor can be accomplished, in particular, through active heating of the adsorption element. It is also advantageous if the adsorption element is actively heated during operation of the electric machine and actively cooled after operation or during a break. Heating the adsorption element actively supports the evaporation of condensate. In particular, the adsorption element can be actively heated during operation by a section of the electric machine on which it is located. This eliminates the need for active heating of the adsorption element. For example, such a section could be located on a cooling channel within the machine housing, through which a relatively warm heat transfer fluid (e.g., cooling water, cooling oil) flows during operation. This flow is stopped after the electric machine has finished operating. The adsorption element is then cooled (by other means, for example, electrically). For example, a Peltier element designed for active cooling could be located on such a cooling channel. During operation of the electric machine, the Peltier element is switched off and actively heated by a heat transfer fluid flowing through the cooling channel. After operation of the electric machine, the flow through the cooling channel is switched off, and the Peltier element is switched on. Alternatively, it would also be conceivable for such a Peltier element to be arranged on a stator lamination stack of the stator or on a busbar electrically connected to a stator winding of the stator. In this way, too, the adsorption element can be actively heated during operation of the electric machine and actively cooled after the electrical power supply to the stator is switched off, i.e., when the electric machine is switched off.In another embodiment, the adsorption element can be arranged on an inverter, which closes an opening in the machine housing. In this way, waste heat from the inverter can be used to heat the adsorption element. After the inverter is switched off when the electric machine is turned off, the adsorption element is actively cooled again. BRIEF DESCRIPTION OF THE FIGURES Exemplary embodiments of the invention are illustrated in the accompanying schematic figures. These show: Fig. 1 an exemplary, schematically shown half-section electric machine with an active drying element; Fig. 2 a schematic sectional view of an adsorption element with a surrounding barrier membrane; Fig. 3 a schematic sectional view of an electric machine in which the adsorption element is arranged on a cooling channel of an inverter; Fig. 4 an exemplary vehicle with an electric machine of the proposed type; and Fig. 5 a schematic sectional view of an electric machine in which the adsorption element is arranged in a pressure equalization device. DETAILED DESCRIPTION OF THE INVENTION It is stated in the introduction that identical parts in the different embodiments are provided with the same reference numerals or component designations, possibly with different indices. The disclosure of a component contained in the description can be applied analogously to another component with the same reference numeral or component designation. Furthermore, the positional indications chosen in the description, such as "top," "bottom," "back," "front," "side," and so on, refer to the figure directly described and illustrated and must be applied analogously to the new position if the position changes. Fig. 1 shows a half-section through a schematically represented electric machine 1a with a multi-part machine housing 2 comprising a stator housing 3, a front end shield 4, and a rear end shield 5. Alternatively, the stator housing can be pot-shaped and have only one end shield. The machine housing 2 encloses an interior space B of the electric machine 1a and is surrounded by an exterior space C, or rather separates the interior space B from the exterior space C. The electric machine 1a also has a stator 6, which comprises a stator lamination stack 7 (not shown in detail) with several axially stacked stator laminations and stator windings 8 arranged within the stator lamination stack 7. Furthermore, the electric machine 1a includes a rotor 9 with a rotor shaft 10 and a rotor lamination stack 11 (not shown in detail) mounted on the rotor shaft 10. Rotor magnets or rotor windings (not shown) can be arranged within the rotor lamination stack 11. The rotor shaft 10 is rotatably mounted about a rotor axis or stator axis A relative to the stator 6 by means of (rolling) bearings 12a, 12b. Specifically, the first bearing 12a is located in the front bearing shield 4 and the second bearing 12b in the rear bearing shield 5. Furthermore, the electric machine 1a includes an inverter 13, which comprises an inverter housing 14 attached to the machine housing 2 and an electronic inverter circuit 15 arranged therein. This circuit is electrically connected to the stator 6 and is intended for controlling and supplying power to the electric machine 1a. In Fig. 1, the inverter circuit 15 is electrically connected to the stator 6; alternatively or additionally, it could also be electrically connected to the rotor 9. In detail, the inverter circuit 15 in this example comprises a printed circuit board 16 and an electronic circuit 17 arranged thereon. Stator leads 18 are provided for the electrical connection of the inverter circuit 15 to the stator 6. In the example shown in Fig. 1, the inverter 13 closes an opening D in the machine housing 1. However, this is not mandatory; the machine housing 2 can also be continuous in the area of ​​the inverter 13, with a feedthrough for the stator leads 18. Furthermore, in the example shown, the inverter 13 has an internal section E that belongs to the internal space B of the electric machine 1a. This is also not mandatory, and the inverter 13 could also be completely separate from the internal space B. Finally, the electric machine 1a comprises an adsorption element 19 arranged in the interior space B and actively coolable below the condensation point of the air in the interior space B for absorbing water vapor or water, wherein, in the specific example shown, the adsorption element 19 is connected to an optional discharge line 20 leading from the interior space B to the exterior space C. Finally, the electric machine 1a comprises a pressure equalization opening 21 or a pressure equalization device, which connects the interior space B with the exterior space C. The proposed measures enable the repeated drying of the air in interior B, thereby maintaining the humidity in interior B of the electrical machine 1a within a favorable range. In particular, condensation of moisture on components other than the adsorption element 19 in interior B can be prevented or at least reduced, thus preventing or at least reducing damage to these components of the electrical machine 1a. For this purpose, the adsorption element 19 is actively cooled, such that its surface temperature is at least temporarily lower than the dew point temperature of the air in interior B. As a result, the moisture from the air in interior B is absorbed by the adsorption element 19, or the adsorption element 19 absorbs water vapor or water through adsorption.In particular, the adsorption element 19 is cooled to a temperature that is lower than the temperature of other components or surfaces located in the interior B, so that the adsorption preferably takes place on the adsorption element 19 or is limited to it altogether. The proposed measures are particularly advantageous when the interior B of the electrical machine 1a is connected to the exterior C via a pressure equalization opening 21 or a pressure equalization device, as is the case in the example shown in Fig. 1. Moisture can enter the interior B of the electrical machine 1a through this pressure equalization opening 21 or this pressure equalization device even after its manufacture. However, the adsorption element 19 reduces or prevents condensation of moisture on components of the electrical machine 1a within its interior B, even in this case. Condensate (water) flowing from the adsorption element 19 can be conveyed via the drain line 20 into the external chamber C, where it can drip off or evaporate. The water can flow away by gravity or be pumped or suctioned out. In one embodiment, a check valve can be arranged in the drain line 20, allowing water to flow outwards but preventing it from flowing back inwards. In particular, an opening in the drain line 20 into the external chamber C can be located in an area where a negative pressure occurs or is expected during operation of the electric machine 1a. This also facilitates the drainage of the water.For example, such a negative pressure can be caused by an airflow that is directly or indirectly caused by the electric machine 1a, such as by a fan driven by the electric machine 1a, which generates the airflow in the outside space C (direct causation), or also by the movement of a vehicle 24 for which the electric machine 1a serves as a drive (indirect causation - see also Fig. 4). The pressure equalization opening 21 or the pressure equalization device can also be integrated into or formed by the discharge line 20. This results in a particularly compact design of the electric machine 1a. Because the inverter 13 in the example shown has an interior section E which belongs to the interior B of the electrical machine 1a, the interior section E can also be kept in a favorable range with regard to humidity, and in particular condensation of moisture on components of the inverter 13 can be prevented or at least reduced there. For example, the adsorption element 19 can be arranged on or formed by an electrically operated cooling element. For example, the adsorption element 19 can be arranged on or formed by a Peltier element. It would also be conceivable that the adsorption element 19 is cooled by means of a cooling compressor, which is preferably electrically operated. Fig. 2 shows a schematic sectional view of an embodiment in which the adsorption element 19 is surrounded on the interior B side of the electric machine 1a by a waterproof and / or oil-tight, but water vapor-permeable barrier membrane 22. This prevents any coolant and / or lubricant located in the interior B of the electric machine 1a from penetrating the adsorption element 19 and damaging or rendering it unusable. The barrier membrane 22 can, for example, consist of stretched expanded polytetrafluoroethylene and have micropores with a diameter of 0.02 to 1 µm. Such a barrier membrane 22 is known in particular under the trade name "Gore-Tex". Another type of barrier membrane 22 is a hydrophilic membrane through which water vapor can diffuse and which is known in particular under the trade name "Sympatex". In the embodiment shown in Fig.In the embodiment shown in Figure 2, the barrier membrane 22 is recessed in the area of ​​the machine housing 2; however, the adsorption element 19 could also be completely surrounded by the barrier membrane 22 (except for an opening in the area of ​​the discharge line 20). Furthermore, it can be seen from Figure 2 that the discharge line 20 in the example shown is arranged directly below the adsorption element 19 and leads perpendicularly into the external space C. Fig. 3 shows another embodiment of an electric machine 1b, which is very similar to the electric machine 1a shown in Fig. 1, but in which a cooling channel 23 is provided in the inverter housing 14, on which the adsorption element 19 is arranged. For example, the cooling channel 23 can be filled with a liquid, cooled heat transfer fluid. The heat transfer fluid can be, for example, water- or oil-based. It would also be conceivable that the adsorption element 19 is cooled by means of a cooling compressor. In particular, the cooling channel 23 is then filled with a vaporous heat transfer fluid (refrigerant). It is also conceivable that the cooling compressor could be used for other purposes, for example, to cool the interior of a vehicle 24 in which the electric machine 1b is installed (see also Fig. 4). In the example shown in Fig. 3, the adsorption element 19 is arranged on a partition wall encompassed by the inverter housing 14, which lies between the adsorption element 19 and the cooling channel 23. Preferably, the partition wall has a thermal conductivity λ of at least 10 W / (m·K) and is made, for example, of a metal. However, the adsorption element 19 could also be directly adjacent to the cooling channel 23 if a corresponding opening is provided in the inverter housing 14. It should also be noted that the cooling channel 23 can cool not only the adsorption element 19 but also the inverter circuit 15. In particular, a power section of the inverter circuit 15 can be located in the area of ​​the cooling channel 23. Similarly, the adsorption element 19 could alternatively be arranged on a cooling channel 23 located in the machine housing 2, or more generally on a region of the electric machine 1b that is actively cooled during operation of the electric machine 1b. The cooling channel 23 located in the machine housing 2 can, in turn, be supplied with a liquid or vaporous heat transfer fluid. In a further embodiment variant, the adsorption element 19 could be arranged in the interior section E of the inverter 13. It is generally advantageous if the adsorption element 19 projects into the interior B of the electric machine 1a, 1b, as is the case in Figs. 1, 2 to 3. In this way, the adsorption element 19 has a comparatively large surface area to which water or ice can adhere. It is also advantageous if the adsorption element 19 has a lattice or ribbed structure. This also provides the adsorption element 19 with a comparatively large surface area to which water or ice can adhere. This measure is particularly beneficial in combination with an adsorption element 19 that projects into the interior B of the electrical machine 1a, 1b. In particular, the adsorption element 19 can be a dedicated adsorption element, as is the case in Fig. 1, Fig. 2 to Fig. 3, i.e. a separate element specifically designed for the absorption of water vapor or water from air located in the interior B. Furthermore, it is advantageous if the adsorption element 19 is arranged in a region of the electric machine 1a, 1b that is surrounded by air flowing from the interior during operation of the electric machine 1a, 1b. This ensures that the air to be dried is directed over the adsorption element 19. For example, the airflow in the interior B can be caused by the rotating rotor 9. In particular, the airflow can be caused by a fan driven by the rotor 9. For example, a suitable fan wheel can be mounted on the rotor shaft 10. However, the airflow can also be caused by diffusion. Another difference between electric machine 1b and electric machine 1a is that in electric machine 1a, the condensed water is drained from the interior B, whereas electric machine 1b does not have a drain line 20 and the condensed water remains in the electric machine 1b. In other words, the air in the interior B of electric machine 1b is repeatedly dried in a cycle. However, a drain line 20 is not excluded in the arrangement of the adsorption element 19 shown in Fig. 3. Specifically, the adsorption element 19 can be designed to release water or water vapor into the interior B of the electric machine 1b during operation and to absorb water or water vapor from the interior B during periods of inactivity. While the evaporation of water during operation of the electric machine 1b increases the humidity in the interior B, it also prevents or reduces the additional moisture enrichment of the air in the interior B from outside air entering the interior B due to this reduced diffusion gradient. In this way, with appropriate dimensioning, the absorption of water or water vapor by the adsorption element 19 during periods of inactivity of the electric machine 1b may be sufficient to prevent or at least limit condensation of water on components other than the adsorption element 19.As already mentioned, the absorption of water vapor or water is achieved by actively cooling the adsorption element 19. The release of water vapor can be achieved in particular by actively heating the adsorption element 19. Heating can be achieved by the adsorption element 19 itself or by heating a section of the electric machine 1b on which the adsorption element 19 is located during operation of the electric machine 1b. In this context, particular reference is made to the arrangement of the adsorption element 19 on the cooling channel 23. During operation of the electric machine 1b, the adsorption element 19 can be not only cooled but also heated by the heat transfer fluid flowing in the cooling channel 23. This can be accomplished by heating the heat transfer fluid significantly, for example, by absorbing waste heat from the stator 6, thus also heating the adsorption element 19. After operation of the electric machine 1b or during an operating break, the heat transfer fluid can be cooled (significantly), thereby cooling the adsorption element 19 below the condensation point of the air in the interior B.In this context, it is advantageous if the electric machine 1b or a cooling circuit connected to the cooling channel 23 includes valves with which the cooling of the electric machine 1b can be limited to the area in which the adsorption element 19 is also located, so that other areas of the electric machine 1b are not also cooled below the condensation point of the air in the interior B. It is also conceivable that the adsorption element 19 itself includes the means necessary for cooling, which are switched off during operation of the electric machine 1b, causing the adsorption element 19 to be heated by the heat transfer fluid. After operation of the electric machine 1b, these means are activated to cool the adsorption element 19. For example, the adsorption element 19 could be designed as a Peltier element. During operation of the electric machine 1b, the Peltier element is switched off and actively heated by the heat transfer fluid flowing through the cooling channel 23. This is particularly effective if the cooling channel 23, and thus the Peltier element 19, is located in the area of ​​a power section of the inverter circuit 15. After operation of the electric machine 1b, the flow through the cooling channel 23 is switched off, and the Peltier element 19 is switched on.Alternatively, it would also be conceivable that such a Peltier element 19 could be arranged on the stator lamination stack 7 or on the busbars 18. In this way, too, the adsorption element 19 can be actively heated during operation of the electric machine 1b and actively cooled after the electrical power supply to the stator 6 is switched off when the electric machine 1b is switched off. In general, it can be provided that the adsorption element 19 is a) not cooled during operation of the electric machine 1a, 1b and is only cooled after operation of the electric machine 1a, 1b or during an operating break, b) not cooled above a first temperature in the interior B and cooled below a second, lower temperature in the interior B, c) not cooled below a first relative humidity in the interior B and cooled above a second, higher relative humidity in the interior B, d) not cooled above a first temperature in the exterior C and cooled below a second, lower temperature in the exterior C, e) not cooled below a first relative humidity in the exterior C and cooled above a second, higher relative humidity in the exterior C.f) based on a combination of at least two of cases a) to e) is cooled or not cooled. For example, the adsorption element 19 can be cooled (activated) when the electric machine 1a, 1b is switched off or when the temperature in the interior B falls below a predetermined level. A logical AND operation can also be used instead of a logical OR operation. Accordingly, it can be provided that the adsorption element 19 is cooled (activated) when the electric machine 1a, 1b is switched off and when the temperature in the interior B falls below a predetermined level. In a further embodiment, it can be provided that the adsorption element 19 is cooled (activated) when the electric machine 1a, 1b is operated in a cool, foggy environment, etc. Fig. 5 shows a schematic sectional view of an electric machine 1c in which the adsorption element 19 is arranged in a pressure equalization device (or pressure equalization element) DAE. For this purpose, the pressure equalization device DAE has an internal section F that belongs to the interior of the electric machine 1c, with the adsorption element 19 being arranged in this internal section F. This allows the adsorption element 19 to be integrated into the electric machine 1c in a particularly space-saving manner. Figure 4 shows an electric machine 1 installed in a vehicle 24, which, together with a coupled transmission 25, forms a drive unit 26. The vehicle 24 has two axles, one of which is driven. Specifically, the drive unit 26 is connected to the half-axles 27 of the rear axle. The driven wheels 28 are mounted on the half-axles 26. The vehicle 24 is driven, at least partially or temporarily, by the electric machine 1. That is, the electric machine 1 can serve as the sole drive for the vehicle 24 or, for example, be used in conjunction with an internal combustion engine (hybrid drive). In particular, in a drive unit 26, it can generally be provided that the interior B of the electric machine 1 is connected to an interior of the gearbox 25. The proposed measures also ensure that the aforementioned interior of the gearbox 25 remains dry. In conclusion, it is noted that the scope of protection is defined by the patent claims. However, the description and drawings are to be used to interpret the claims. The features depicted in the figures can be freely exchanged and combined. In particular, it is also noted that the devices shown may, in reality, comprise more or fewer components than depicted. In some cases, the devices shown, or their components, may also be depicted not to scale and / or enlarged and / or reduced in size. Reference symbol list 1, 1a, 1b, 1c electric machine 2 machine housing 3 stator housing 4 first bearing shield 5 second bearing shield 6 stator 7 stator lamination stack 8 stator winding 9 rotor 10 rotor shaft 11 rotor lamination stack 12a, 12b (rolling) bearings 13 inverter 14 inverter housing 15 inverter circuit 16 printed circuit board 17 electronic circuit 18 busbar 19 adsorption element 20 drain line / condensate line 21 pressure equalization opening 22 barrier diaphragm 23 cooling channel 24 vehicle 25 gearbox 26 drive unit 27 half shaft 28 wheel A rotor shaft / stator shaft B interior of electric machine C exterior D opening of machine housing E interior section inverter F interior section pressure equalization device DAE pressure equalization device

Claims

Electric machine (1, 1a, 1b), comprising a machine housing (2) which surrounds an interior space (B) of the electric machine (1, 1a, 1b) and separates it from an exterior space (C), as well as a stator (6) arranged in the machine housing (2) and a rotor (9) rotatably mounted in the machine housing (2) relative to the stator (6), characterized by an adsorption element (19) arranged in the interior space (B) and which can be actively cooled below a condensation point of air located in the interior space (B) for the absorption of water vapor or water. Electric machine (1, 1a, 1b) according to claim 1 , characterized by- a cooling channel arranged in the machine housing (2) on which the adsorption element (19) is arranged, or- a cooling channel (23) arranged in an inverter (13) of the electric machine (1, 1a, 1b) on which the adsorption element (19) is arranged, wherein the inverter (13) closes an opening (D) of the machine housing (2). Electric machine (1, 1a, 1b) according to claim 1 or 2, characterized in that the adsorption element (19) is arranged on or formed by an electrically operated cooling element. Electric machine (1, 1a, 1b) according to one of the preceding claims, characterized by an inverter (13) which is attached to the machine housing (2) and has an interior section (E) which belongs to the interior (B) of the electric machine (1, 1a, 1b), wherein the adsorption element (19) is arranged in the interior section (E) of the inverter (13). Electric machine (1, 1a, 1b) according to one of the preceding claims, characterized in that the adsorption element (19) projects into the interior space (B). Electric machine (1, 1a, 1b) according to one of the preceding claims, characterized in that the adsorption element (19) is surrounded towards the interior (B) of the electric machine (1, 1a, 1b) by a waterproof and / or oil-tight, but water vapor-permeable barrier membrane (22). Electric machine (1, 1a, 1b) according to one of the preceding claims, characterized in that the adsorption element (19) connects to a discharge line (20) leading from the interior (B) to the exterior (C). Electric machine (1, 1a, 1b) according to one of the preceding claims, characterized in that the interior (B) of the electric machine (1, 1a, 1b) is connected to the exterior space (C) via a pressure equalization opening (21) or a pressure equalization device. Electric machine (1, 1a, 1b) according to claims 7 and 8, characterized in that the pressure equalization opening (21) or the pressure equalization device is integrated in the discharge line (20). Electric machine (1, 1a, 1b) according to claim 1 , characterized in that the interior (B) of the electric machine (1, 1a, 1b) is connected to the exterior space (C) via a pressure equalization device (DAE), the pressure equalization device (DAE) has an interior section (F) which belongs to the interior (B) of the electric machine (1, 1a, 1b), and the adsorption element (19) is arranged in the interior section (F). Vehicle (24) with an electric machine (1, 1a, 1b) according to one of claims 1 to 10, which is provided for driving the vehicle (24). Method for operating an electric machine (1, 1a, 1b) according to one of claims 1 to 10, characterized in that the adsorption element (19) absorbs water vapor or water by adsorption when actively cooled below a condensation point of air located in the interior (B). The method according to claim 12, characterized in that the adsorption element (19) is: a) not cooled during operation of the electric machine (1, 1a, 1b) and is only cooled after operation of the electric machine (1, 1a, 1b) or during an operating break; b) not cooled above a first temperature in the interior (B) and is cooled below a second, lower temperature in the interior (B); c) not cooled below a first relative humidity in the interior (B) and is cooled above a second, higher relative humidity in the interior (B); d) not cooled above a first temperature in the exterior (C) and is cooled below a second, lower temperature in the exterior (C); e) not cooled below a first relative humidity in the exterior (C) and is cooled above a second, higher relative humidity in the exterior (C).f) based on a combination of at least two of cases a) to e) is cooled or not cooled. Method according to claim 12 or 13, characterized in that the adsorption element (19) releases water or water vapor into the interior (B) of the electric machine (1, 1a, 1b) during operation of the electric machine (1, 1a, 1b) and absorbs water or water vapor from the interior (B) of the electric machine (1, 1a, 1b) during operating breaks of the electric machine (1, 1a, 1b). Method according to claim 14, characterized in that the adsorption element (19) is heated during operation of the electric machine (1, 1a, 1b) and is cooled after operation of the electric machine (1, 1a, 1b) or during an operating break.

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