Cooling device for an electric motor

Abstract

Cooling device (100) for an electric motor, comprising a rotor (200) and a stator (210) and a gap (220) formed between them, in which a fluid flow (F) is guided for cooling the rotor (200), and with a rear axial end (202) of the rotor (200) seen in the direction of flow of the fluid flow (F), to which a diffuser (110) with guide vanes (111, 111') arranged circumferentially is attached, characterized in that a support (150) with guide vanes (112) attached to it runs between the rotor (200) and the stator (210), which is slidably mounted along the axial length of the rotor (200) by means of an actuator (160 ... 162).

Description

[0001] The invention relates to the technical field of drive technology and in particular to a cooling device for an electric motor according to claim 1, a method for cooling such a motor according to claim 19 and a preferred use of the cooling device according to claim 20.

[0002] Electric motors are constantly being further developed. Their efficiency has been significantly increased in recent decades. However, it is not possible to develop a loss-free electric motor. Losses always occur, such as copper losses (ohmic power losses) which, depending on the motor type, can occur in both the rotor and the stator; iron losses due to remagnetization caused by eddy currents in ferromagnetic materials; and friction losses due to air and bearing friction.

[0003] All these losses are converted into heat. In short-term operation, the components of the electric motor can absorb this heat without cooling. Heat capacity plays a crucial role here. However, in continuous operation, a cooling system must be provided to prevent temperatures from exceeding permissible limits. Electric motors can be cooled by surface cooling, internal cooling, or closed-loop cooling.

[0004] In surface cooling, the heat output from the components is transferred to the closed outer surface of the machine via a closed primary cooling circuit, either through an internal air circuit or by conduction. The simplest method of surface cooling is self-cooling, where cooling occurs solely through natural convection and radiation at the closed motor surface. Self-cooled machines are typically large, stationary electric motors. In self-cooling, the coolant is circulated by the machine itself. Here, the coolant is moved across the closed motor surface depending on the motor speed. This is made possible by a fan mounted on a rotor shaft. An extension of this is external surface cooling. The fan can be driven by its own motor, independent of the rotor speed.

[0005] In internal cooling, also known as forced-air cooling, air flows directly through the machine's interior as a coolant. The coolant absorbs the heat almost directly at the source and dissipates it to the outside. This cooling method is significantly more intensive than surface cooling. Here, too, a distinction is made between self-cooling and external cooling, based on the type of fan drive.

[0006] Closed-loop cooling describes a cooling method in which the primary coolant circulates in a closed loop, and the heat is transferred to the secondary coolant via a heat exchanger. The primary and secondary coolants can be either gaseous or liquid. Closed-loop cooling enables intensive heat dissipation despite the enclosed design and high degree of protection. A classic example of closed-loop cooling in electric vehicles is the use of a water jacket housed within the vehicle's casing. The cooling fluid absorbs the heat in the water jacket and releases it to the ambient air via the heat exchanger.

[0007] The standard for "Rotating electrical machines" DIN EN 60034-6 (VDE 0530-6) describes these three main cooling methods. The present invention relates to internal cooling.

[0008] Due to the high power density of permanent magnet synchronous motors (PMSM), cooling is of particular importance. The rotor, in particular, is at risk of overheating during operation. If a certain temperature limit is exceeded, the permanent magnets can become partially or completely demagnetized. In most cases, the rotor is then unusable and must be replaced.

[0009] To dissipate the heat generated by the rotor, various cooling systems have become established. A radial fan mounted on a rotor shaft is frequently used. The higher the rotational speed, the greater the cooling effect. However, this principle reaches its limits at a certain speed. The materials must be selected to withstand centrifugal forces, the cooling capacity becomes difficult to regulate, and the rotor's inertia increases.

[0010] The current trend towards downsizing for cost reasons exacerbates these problems. In this case, downsizing means significantly increasing the rotor speed. To deliver the same power output, the electric motor needs to generate less torque. The lower the torque, the smaller and lighter the copper windings and permanent magnets can be, thus saving costs.

[0011] However, the high rotational speeds also present challenges, as special bearings are required. Lubrication methods also need to be adapted. Furthermore, mechanical stresses arise, because the rotor should not suffer any plastic deformation in the radial direction, even if the rated speed is only slightly exceeded. Regarding rotor dynamics, the rotor must be precisely balanced to prevent any imbalance, as these effects are more pronounced at high speeds. Finally, conventional internal cooling methods reach their limits or even cause significant losses, for example, with direct oil cooling of the rotor.

[0012] A cooling device of this type is known from DE 297 16 977 U1. Further cooling devices or methods for cooling are disclosed in DE 10 2017 128 856 A1, DE 10 2011 012 454 A1 and WO 2016 / 041 873 A1.

[0013] One object of the present invention is therefore to provide a cooling system that is as simple and cost-effective as possible, provides sufficient cooling capacity and, in addition, does not or only minimally affects the rotor itself.

[0014] This problem is solved by a cooling device for an electric motor according to claim 1, comprising a rotor and a stator and a gap formed between them in which a fluid flow is guided for cooling the rotor, and a rear axial end of the rotor seen in the direction of flow of the fluid flow, to which a diffuser with guide vanes arranged circumferentially is attached, wherein a support with guide vanes attached to it runs between the rotor and stator, which is slidably mounted along the axial length of the rotor by means of an actuator.

[0015] The present invention assumes that a fluid such as air flows directly through the interior of the machine as a coolant during internal cooling or forced-air ventilation. The coolant absorbs the heat almost directly at the source and dissipates it to the outside. The cooling is significantly more intensive than with surface cooling. Here, too, a distinction is made between self-cooling and external internal cooling, which is based on the type of fan drive. In self-cooling, the rotor directly drives the coolant delivery system, while in external internal cooling, an additional, independent coolant delivery system is provided.

[0016] Internal cooling is preferred here because it is less expensive. An example of internal cooling is a radial fan on a rotor shaft. This fan delivers a corresponding mass flow of coolant depending on the rotational speed. While internal cooling is still a good solution for low and medium power densities, external cooling would be more suitable for high power densities of electric motors to ensure adequate cooling. However, this is usually associated with significantly more effort and higher costs. In contrast, the cooling device according to the invention, with a diffuser and guide vanes mounted around it, can utilize internal cooling even for high power densities.The guide vanes are attached to a frustoconical, tapered circumferential wall of the diffuser, i.e., in an area where the cross-section through which the fluid flows widens in the direction of flow. This reduces the flow velocity and builds up a static pressure that promotes heat transfer from the fluid to the stator.

[0017] The energy to operate the cooling device is supplied to the fluid or cooling medium, in whole or in part, by the rotor of the electric motor through friction. The rotor accelerates the fluid primarily through friction, and its kinetic energy is converted into static pressure, i.e., potential energy, in the diffuser and / or guide vanes. The pressure difference across the diffuser creates a suction effect, drawing in fresh, cold fluid and expelling warm fluid. The diffuser itself does not dissipate heat. The increase in static pressure serves to force the fluid through the gap between the rotor and stator / canning tube. Due to the build-up of static pressure, the diffuser acts like a suction pipe, drawing in fresh fluid through the gap between the rotor and stator. The heat is then primarily absorbed by the fluid and dissipated via the fluid flow. Heat transfer to the stator also occurs.

[0018] Advantageous further developments of the cooling device according to the invention are specified in the dependent claims.

[0019] In a first advantageous embodiment of the cooling device according to the invention, the guide vanes are located wholly or partially outside the gap between the rotor and the stator, or alternatively, within a canned tube. If the guide vanes are located only on the diffuser, the diffuser can be manufactured particularly easily as a single piece. On the other hand, guide vanes can also be provided within the gap to effect a pressure increase and increased heat dissipation there. The advantage of guide vanes in the diffuser, however, lies in the fact that the flow is deflected outside the gap, and the heat loss is thereby transferred not to the rotor, but to the guide vanes and diffuser. The canned tube is not strictly necessary, as this effect also occurs without a canned tube between the rotor and stator or stator winding.

[0020] In a first advantageous embodiment of the cooling device according to the invention, the guide vanes are arranged at selected axial positions of the rotor, preferably at the inlet of the fluid flow into and / or outlet of the fluid flow from the gap, in a midway between this inlet and outlet, and may be arranged in multiple groups or distributed uniformly along the length of the gap. The diffuser itself does not dissipate heat, but rather generates a suction effect to draw fresh, cold fluid or cooling medium through the gap and expel warm fluid.

[0021] In a further advantageous embodiment of the cooling device according to the invention, a canned tube with guide vanes attached to it runs between the rotor and the stator. The guide vanes are inserted into the canned tube as a profile, with the guide vanes and the canned tube forming an inseparable component that is easy to assemble.

[0022] In a further advantageous embodiment of the cooling device according to the invention, the guide vanes have a uniform pitch or a variable pitch that can change axially but is fixed. This allows, in particular, the individual design characteristics of an electric motor to be taken into account for the optimal use of thermal bridges.

[0023] In a further advantageous embodiment of the cooling device according to the invention, the rotor is provided with at least one impeller blade or one blade is attached to it. This also makes a classic axial fan design possible. Here, the rotor's shape is modified so that it acts like one or more impeller blades. Alternatively, classic impeller blades can also be attached directly to the rotor. The guide vanes are the same as in the previous versions.

[0024] In a further advantageous embodiment of the cooling device according to the invention, the stator is provided with at least one guide vane, or the guide vane is attached to it. In this design, there is no canned tube. The guide vanes are attached to the stator winding, or the stator winding is given a correspondingly shaped surface, thus forming a counterpart to the impeller blades of the rotor in a particularly simple manner. In principle, the fluid conveyed can be air, oil, or another medium.

[0025] According to the invention, a support structure with guide vanes attached to it (externally and / or internally) runs between the rotor and the stator and is slidably mounted along the axial length of the rotor by means of an actuator. This allows the fluid flow to be manipulated, for example, depending on the rotor speed and / or temperature, in order to accelerate heat dissipation.

[0026] In a further advantageous embodiment of the cooling device according to the invention, a sleeve with a funnel-shaped interior runs between the rotor and the stator, and is slidably mounted along the axial length of the rotor by means of an actuator. Such a sleeve, or throttle, at the fluid flow inlet to the gap is used to reduce the fluid flow. An actuator motor actuates the throttle, with the advantage that a vacuum is created only in the gap between the rotor and the can tube. Alternatively, a simple, controllable throttle valve can also be installed at an inlet opening of the fluid flow in a bearing shield of a rotor shaft.

[0027] Preferably, the actuator is designed as a servo motor, a thermal expansion element, or a spring. A servo motor axially displaces the holder with the guide vanes, thus varying the fluid flow rate depending on the axial position of the holder. A thermal expansion element, also known as a thermal actuator, expands when the temperature rises and pushes the holder with the guide vanes into the gap between the rotor and the canned tube. This increases the fluid flow rate as the temperature increases. The thermal expansion element preferably extends through a fluid flow outlet in a bearing shield of a rotor shaft. The guide vanes are never completely withdrawn from the canned tube so that at least a small airflow is maintained, allowing the expansion element to respond to temperature increases. At low rotational speeds, a spring pulls the guide vanes largely out of the gap between the rotor and the canned tube.This minimizes the flow rate of the fluid. At high speeds, the deflection of the flow results in an axial force on the guide vanes. This force pulls the guide vanes into the gap, thereby increasing the flow rate of the fluid.

[0028] In a further advantageous embodiment of the cooling device according to the invention, the guide vanes are designed to be flexible, and their geometry can be changed by moving the mounting. This allows the inlet and outlet angles of the fluid stroma at the individual guide vanes to be adjusted. The efficiency of heat dissipation can be increased by optimizing the flow of fluid. An actuator presses the guide vanes against an edge, similar to metal sheets. The further the actuator is extended, the more the sheets are bent at the tip. This allows the inlet angle of the guide vanes to be adapted to the flow, thereby reducing losses.

[0029] In a further advantageous embodiment of the cooling device according to the invention, the diffuser opens radially inwards and outwards with increasing distance from the rear axial end of the rotor. Different diffuser variants are possible, such as a diffuser similar to that used on a radial compressor, or an axial diffuser with an axially opening cross-section. Modifications could affect the canned tube and the rotor, only the canned tube, or only the rotor. Alternatively, neither the canned tube nor the rotor could be modified, but only the housing. In this case, the diffuser would have to be housed within the housing due to its size.

[0030] Ideally, the diffuser is formed by a frustoconical taper of the rotor and / or a funnel-shaped widening of a slotted tube between the rotor and stator and / or of a housing of the rotor and stator, which is easy to achieve in terms of design.

[0031] Alternatively, it is preferred that a diffuser is arranged at an outlet opening and / or a nozzle at an inlet opening of the fluid flow on a bearing shield of a rotor shaft, preferably radially circumferentially on the bearing shield, similar to a radial compressor. Conversely, a nozzle can also be arranged at an inlet opening of the fluid flow on the bearing shield of the rotor shaft, in the reverse principle of a radial compressor.

[0032] In a further advantageous embodiment of the cooling device according to the invention, it is provided that a nozzle, preferably a nozzle with guide vanes, is formed at a forward axial end of the rotor as seen in the direction of the fluid flow, which can be achieved particularly easily by a funnel-shaped inlet of a slotted tube in this area.

[0033] In a further advantageous embodiment of the cooling device according to the invention, the fluid flow in the gap is guided over riblets. Since the flow conditions in the gap are either laminar or turbulent, so-called riblets are suitable for reducing friction in turbulent flow. These are found naturally on the skin of sharks and reduce the flow resistance of turbulent flow. Artificially produced structures are available for technical applications. The riblets are located either along the entire length of the moving and stationary surfaces of the rotor and / or the stator and / or a slot tube, or they are applied only to certain areas. The objectives are to reduce friction losses in the gap and to partially or completely laminarize the flow before it enters the guide vanes in order to reduce flow losses.

[0034] In a further advantageous embodiment of the cooling device according to the invention, the fluid flow in the gap is guided over turbulators. The turbulators transition a laminar flow into a turbulent flow. This increases the heat transfer between the rotor and the fluid flow. Shortly before the guide vanes, the flow is returned to a laminar state to ensure the most optimal flow towards the guide vanes. Turbulators, or turbulence or vortex generators, are known from aircraft construction. Various types of turbulators are conceivable, such as cylindrical protrusions and / or indentations, similar to dimples on golf balls.

[0035] It is preferred that the riblets and / or turbulators are formed on the rotor and / or the stator and / or on a canned tube. In particular, in an electric motor with a canned tube, the turbulators and / or riblets can be located on the rotor and / or on the canned tube, and in an electric motor without a canned tube, on the rotor and / or on the stator winding.

[0036] In a further advantageous embodiment of the cooling device according to the invention, an open or closed cooling circuit is provided in which the fluid flow occurs. The open circuit is characterized by the fact that the fluid, such as air, is drawn in from the environment and the heated air is discharged back into the environment. Filters are provided at an inlet and outlet opening on a bearing shield of a rotor shaft to prevent the ingress of foreign matter. The closed circuit is characterized by the fact that the fluid does not leave the circuit. The excess heat is dissipated via a heat exchanger.

[0037] The above problem is also solved by a method for cooling an electric motor according to claim 19, in which a fluid flow guided in a gap between the rotor and stator of the electric motor is manipulated by deceleration and / or deflection and / or turbulence formation, and heat is removed from the velocity-decelerated fluid flow via the stator and / or the fluid flow itself.

[0038] A key aspect of the method is its ease of implementation and efficiency, which is also reflected in low realization costs. The method is preferably carried out using the cooling device described above according to the invention.

[0039] In principle, the cooling device according to the invention can be used to cool any electric motors, however, it is intended to be used specifically for high-speed electric motors that require particularly effective cooling.

[0040] Further advantages, objectives, and features of the present invention are explained with reference to the accompanying figures. Similar components may have the same reference numerals in the different embodiments. Fig. Figures 1 to 9 show aspects of different embodiments of the cooling device according to the invention, all of which follow a fundamentally similar structure of rotor and stator, rotor shaft and rotor bearing with or without a canned tube and / or housing.

[0041] The Fig. Figure 1 shows aspects of an embodiment of the cooling device 100 according to the invention, in which a rotor 200 of an electric motor is rotatably mounted on rotor bearings 250 on both sides via a rotor shaft 260, and in a gap 220 between the rotor 200 and a (not shown here for clarity) Fig. 5 - The stator 210 shown is enclosed by a canned tube 230. A cooling fluid flow F enters a gap 220 between the rotor 200 and the canned tube 230 via an inlet opening 251 of the rotor bearing 250, flows over the rotor 200, and exits again via an outlet opening 252. The fluid flow can be an air flow, but it can also comprise another suitable cooling medium. The rotor bearing 250 is shown here as a rolling bearing, but it can also be a plain bearing or another suitable bearing.

[0042] At the rear axial end 252 of the rotor 200, the fluid flow F passes through a diffuser 110, around the circumference of which guide vanes 111, 111' are mounted. These vanes deflect and slow down the fluid flow F, thereby increasing the static pressure in the fluid flow and promoting heat transfer via the can 230 to the stator 210. The diffuser itself does not dissipate heat. The static pressure serves to pump the fluid through the air gap. Due to the build-up of static pressure, the diffuser acts like a suction pipe, drawing in fresh fluid through the gap between the rotor and stator. The heat is primarily absorbed by the fluid and also dissipated via the fluid flow. Heat transfer to the stator also occurs.

[0043] It can also be seen that at least one guide vane 111" is located in the area of ​​the adjacent gap 220 and is attached to the gap tube 230. The guide vanes 111, 111' on the diffuser 110 can also be additionally connected to the gap tube 230, resulting in a combination of gap tube 230 and diffuser 110 with attached guide vanes. Although this is not strictly necessary, it creates a component that is easy to assemble, consisting of gap tube 230, diffuser 110, and guide vanes 111 ... 111". The diffuser 110 with guide vanes 111, 111' can also be axially displaceable and thus have its performance adjustable.

[0044] This embodiment of the cooling device 100 according to the invention is the fundamentally preferred embodiment and solves the problem set even without a slotted tube 230 and guide vanes 111" attached to it in the slot 220, or by guide vanes 111' attached to the stator 210 in the slot 230; the diffuser alone with guide vanes 111, 111' attached around its circumference is sufficient.

[0045] The Fig. Figure 2 shows aspects of an embodiment of the cooling device 100 according to the invention, which provides that guide vanes 112 ... 112" are attached to the canned tube 230 at a front, middle, and end position of the rotor 200, and these guide vanes have a variable pitch. This slows down the fluid flow F and increases the static pressure, thereby effectively cooling the rotor 200 even at these positions. The cooling does not occur directly by building up the static pressure but indirectly through the flowing fluid itself. The fluid flow only arises from the pressure difference across the guide vanes. Of course, this embodiment can also function without a canned tube 230 if the guide vanes 112 ... 112" are attached to or formed with the stator 210 itself.

[0046] The Fig. Figure 3 shows aspects of an embodiment of the cooling device 100 according to the invention, which is fundamentally similar to that of the Fig. The system is constructed as shown in Figure 2, but includes guide vanes 113 ... 113" attached to the canned tube 230, each with the same pitch similar to a screw thread. Guide vanes designed in this way also serve the purpose of redirecting the fluid flow F and slowing it down by increasing the static pressure in order to achieve better heat dissipation via the canned tube 230 to the stator 210. Here, too, heat dissipation via the stator or the canned tube is not the primary objective. The cooling medium, such as air, absorbs the rotor heat and conducts it away via a bearing shield 253 of the rotor shaft 260. The canned tube is not necessarily required here either; it is sufficient to attach the guide vanes 112 ... 112" to the stator 210 or to give the stator itself a corresponding shape.

[0047] The Fig. Figure 4 shows aspects of an embodiment of the cooling device 100 according to the invention, which provides a rotor 200 with impeller blades 114 attached to it and a guide vane 112 at the end, which is attached to the canned tube. Here, the impeller blades 114 have a uniform pitch, while the guide vane 112 at the end has a variable pitch, which, in addition to compressing the fluid flow F along the length of the rotor 200, provides a final pressure increase of the fluid flow F at the axial end 202 of the rotor 200. Thus, the rotor 200 is cooled along its length, and the heat that cannot yet be dissipated at its end 202 is carried away by the fluid flow F and, to a lesser extent, also by the canned tube 230 and the stator 210. Here too, a slotted tube 230 is not absolutely necessary if the guide vanes 112 are attached to the stator 210 or are formed with it.

[0048] The Fig. Figure 5 shows aspects of an embodiment of the cooling device 100 according to the invention, in which the rotor 200 and the stator 210 are enclosed in a housing 240, and the rotor 200 is supported on both sides of the housing via the rotor shaft 260. The fluid flow F can enter the housing 240 through an inlet opening 251, flow over the rotor 200 in a gap 220, and exit the housing 240 again through an outlet opening 252. In this embodiment of a cooling device 100 according to the invention, no channel tube is explicitly provided, and the guide vanes 112 are attached to the stator 210 itself or are formed by it. The closed design of this cooling device 100 makes it particularly easy to use a medium other than air for cooling.

[0049] The Fig. Figure 6a shows aspects of an embodiment of the cooling device 100 according to the invention, in which a cylindrical holder 150 is provided which is axially displaceable around the rotor 200. This holder 150 contains internal guide vanes 112 and can be moved by an actuator, here a servo motor 160. Depending on the position of the holder 150 on the rotor 200, the flow rate of the fluid can be varied, for example, depending on the rotational speed of the rotor 200, or on the temperature of the rotor 200 and / or the stator 210, or similar measured variables that allow conclusions to be drawn about the required heat dissipation. Alternatively or simultaneously, the holder 150 can also be equipped with external guide vanes 112.

[0050] The Fig. Figure 6b shows aspects of an embodiment of the cooling device 100 according to the invention, in which an expansion element 161 is used that extends through the outlet opening 252 of the bearing shield 253 of the rotor shaft 260. This expansion element 161 expands when the temperature increases and pushes the holder 150 with the guide vanes 112 into the gap 220 between the rotor 200 and the can 230. This increases the fluid flow F as the temperature rises, allowing more heat to be extracted and transferred.

[0051] The Fig. Figure 6c shows aspects of an embodiment of the cooling device 100 according to the invention, in which a spring 162 is used which, at low rotational speeds of the rotor 200, pulls the guide vanes 112 largely out of the gap 220 between the rotor 200 and the slot tube 230. This minimizes the flow rate of the fluid flow F. At high rotational speeds, the deflection of the fluid flow F results in an axial force on the guide vanes 112. This force pulls the guide vanes 112 into the gap and thus increases the flow rate of the fluid flow F.

[0052] The Fig. Figure 6d shows aspects of an embodiment of the cooling device 100 according to the invention, in which a sleeve 163 with a funnel-shaped inner form extends along the axial length of the rotor 200 and is slidably mounted by means of an actuator 160. This sleeve 163 acts as a throttle at the inlet of the fluid flow F into the gap 220 and can reduce the fluid flow F depending on its position on the rotor 200. The throttle is controlled by an actuator 160. The advantage of this is that a vacuum is created only between the rotor 200 and the gap tube 230.

[0053] The Fig. Figure 7a shows aspects of an embodiment of the cooling device 100 according to the invention, in which a diffuser 120 is formed at the rear axial end 202 of the rotor 200 by widening the slotted tube 230 and simultaneously tapering the rotor 200 into a frustoconical shape. A nozzle 130 is formed in a very similar manner at the front axial end 201 of the rotor 200. Such a diffuser 120 and / or such a nozzle 130 can be achieved by modifying the slotted tube 230 and the rotor 200, by modifying only the slotted tube 230, or by modifying only the rotor 200.

[0054] The Fig. Figure 7b shows aspects of an embodiment of the cooling device 100 according to the invention, in which a diffuser 140 is arranged at the outlet opening 252 and, due to its size, outside the rotor bearing 250 or a housing 240. The diffuser 140 is designed similarly to a diffuser on a radial compressor and, conversely, can also be arranged as a nozzle at the inlet opening 251, likewise outside the rotor bearing 250.

[0055] The Fig. Figure 7c shows aspects of an embodiment of the cooling device 100 according to the invention, in which an inlet and an outlet angle of the fluid flow F can be adjusted at the individual guide vanes 112. The optimized flow direction increases the cooling efficiency. In contrast to Fig. Here, the guide vanes 112 are flexible and are bent at their tips by axial movement of the holder 150, allowing the entry angle of the guide vanes 112 to be adapted to the fluid flow F and thus reducing losses. The holder 150 can be used as shown in Fig. 6a shown is controlled by a servomotor 160.

[0056] The Fig. Figure 8 shows aspects of an embodiment of the cooling device 100 according to the invention, which is basically the same as that of the Fig. The device is constructed as shown in Figure 1, but additionally features riblets 170, 170' which are arranged in the gap 220, on the rotor 200 on one side and on the gap tube 230 on the other. These reduce the flow resistance of a turbulent flow, thereby enabling a lower-friction fluid flow F. These riblets 170, 170' are structured similarly to sharkskin and are available as artificially produced structures. They can be located either along the entire length of the moving and stationary surfaces, or they can be applied only to specific areas.

[0057] The Fig. Figure 9 shows aspects of an embodiment of the cooling device 100 according to the invention, which is similar to the Fig.4, but equipped only with guide vane 112. Additionally, turbulators 171 ... 171" are provided on the canned tube 230 over a section of the rotor 200, which convert a laminar fluid flow F into a turbulent fluid flow F. Shortly before the guide vane 112, the fluid flow F is returned to a laminar state to ensure the optimal flow towards the guide vanes 112. The turbulators 171 ... 171" are designed as cylindrical protrusions and / or indentations and are attached to the canned tube 230 and / or the rotor 200 of an electric motor with a canned tube 230. In contrast, for an electric motor without a canned tube 230, the turbulators 171 ... 171" are attached to or formed on the rotor 200 and / or the stator 210, preferably on its stator winding.

[0058] Based on the exemplary embodiments of the cooling device 100 described and shown above, the heat dissipation can be optimally adapted to each application of an electric motor. This is simple and cost-effective to implement and is particularly suitable for high-speed electric motors in electric vehicles.

[0059] It should be noted that the aspects of each individual embodiment of the cooling device 100 described and shown here can also be combined in a common embodiment 100, insofar as this should be required by an application of the cooling device; such combinations of the embodiments described and shown here are familiar to those skilled in the art. Reference symbol list 100 Cooling device 110 Diffuser 111 ... 111" guide vanes 112 ... 112" guide vanes 113 ... 113''' Guide vanes 114 Wheel blade 120 Diffuser 130 nozzle 140 Diffuser 150 bracket 160 actuator 161 Expansion element 162 spring 163 Sleeve 170, 170' Riblets 171 ... 171 Turbulators 200 Rotor 201 Front end of the rotor 202 Rear end of the rotor 210 Stator 220 gap 230 split tube 240 cases 250 rotor bearings 251 Entrance opening 252 Exit opening 253 Storage sign 260 Rotor shaft F Fluid flow

Claims

[1] Cooling device (100) for an electric motor, comprising a rotor (200) and a stator (210) and a gap (220) formed between them, in which a fluid flow (F) is guided to cool the rotor (200), and with a rear axial end (202) of the rotor (200) seen in the direction of flow of the fluid flow (F), to which a diffuser (110) with guide vanes (111, 111') arranged circumferentially is attached, characterized by , that between rotor (200) and stator (210) a support (150) with guide vanes (112) attached to it runs, which is slidably mounted along the axial length of the rotor (200) by means of an actuator (160 ... 162). [2] Cooling device (100) according to claim 1, characterized by , that the guide vanes (111, 11') are located wholly or partially outside the gap (220) between the rotor (200) and the stator (210). [3] Cooling device (100) according to claim 1 or 2, characterized by, that the guide vanes (112 ... 112") are attached at selected axial positions of the rotor (200). [4] Cooling device (100) according to any one of the preceding claims, characterized by , that between the rotor (200) and the stator (210) a slotted tube (230) with guide vanes (113 ... 113''') attached to it runs. [5] Cooling device (100) according to claim 4, characterized by , that the guide vanes (113 ... 113''') have a uniform slope or a variable slope. [6] Cooling device (100) according to any one of the preceding claims, characterized by that the rotor (200) forms at least one impeller blade (114) or that one is attached to it. [7] Cooling device (100) according to any one of the preceding claims, characterized by that the stator (210) forms at least one guide vane (211) or that one is attached to it. [8] Cooling device (100) according to any one of the preceding claims, characterized by, that between rotor (200) and stator (210) a sleeve (163) with a funnel-shaped inner form runs, which is slidably mounted along the axial length of the rotor (200) by means of an actuator (160). [9] Cooling device (100) according to any one of the preceding claims, characterized by that the actuator is designed as a servo motor (160), a wax element (161) or a spring (162). [10] Cooling device (100) according to claim 8 or 9, characterized by , that the guide vanes (112) are designed to be flexible and their geometry can be changed by moving the holder (150). [11] Cooling device (100) according to any one of the preceding claims, characterized by , that the diffuser (120) opens radially inwards and outwards with increasing distance from the rear axial end (202) of the rotor (200). [12] Cooling device (100) according to claim 10, characterized by, that the diffuser (120) is formed by a conical taper of the rotor (200) and / or a funnel-shaped widening of a slotted tube (230) between rotor (200) and stator (210) and / or a housing (240) of rotor (200) and stator (210). [13] Cooling device (100) according to any one of claims 1 to 10, characterized by , that a diffuser (140) is arranged at an outlet opening (252) and / or a nozzle at an inlet opening (251) of the fluid flow (F) on a bearing shield (253) of a rotor shaft (260), preferably radially circumferentially on the bearing shield (253). [14] Cooling device (100) according to any one of the preceding claims, characterized by , that a nozzle (130), preferably a nozzle (130) with guide vanes, is formed at a forward axial end (201) of the rotor (200) as seen in the direction of flow of the fluid flow (F). [15] Cooling device (100) according to any one of the preceding claims, characterized by, that the fluid flow (F) in the gap (220) is guided over riblets (170, 170'). [16] Cooling device (100) according to any one of the preceding claims, characterized by , that the fluid flow (F) in the gap (220) is guided over turbulators (171 ... 171'''). [17] Cooling device (100) according to claim 15 or 16, characterized by , that the riblets (160, 160') and / or turbulators (161 ... 161''') are formed on the rotor (200) and / or on the stator (210) and / or on a slotted tube (230). [18] Cooling device (100) according to any one of the preceding claims, characterized by that an open or closed cooling circuit is provided in which the fluid flow (F) runs. [19] Method for cooling an electric motor with a cooling device (100) according to any one of claims 1 to 18, in which a fluid flow (F) guided between rotor (200) and stator (210) of the electric motor in a gap (220) is manipulated by deceleration and / or deflection and / or turbulence formation, and heat is removed from the velocity-decelerated fluid flow (F) via the stator (210) and / or the fluid flow itself. [20] Use of a cooling device (100) according to one of the preceding claims for cooling high-speed electric motors.

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