Axial flow machine, in particular for a motor vehicle

Abstract

The invention relates to an axial flow machine (10), comprising a rotor (14) having a rotor carrier (18), magnets (20) retained on the rotor carrier (18) and cooling channels (22) running inside the rotor carrier (18), which have cooling air flowing through them to cool the rotor (14) and which each have a inlet (24) via which the cooling air can be introduced into the respective cooling channel (22), and an outlet (28) via which the cooling air can be discharged from the cooling channel (22). Also provided is a valve device (32) associated with the inlets (24) with which a flow cross-section of the respective inlet (24) through which the cooling air flows can be adjusted.

Description

[0001] Axial flux machine, in particular for a motor vehicle

[0002] The invention relates to an axial flux machine, in particular for a motor vehicle, according to the preamble of patent claim 1.

[0003] Such an axial flux machine is already known, for example, from WO 2015 / 019107 A2, WO 2016 / 185173 A1, EP 2 835 895 A2, and EP 1 559604 A1. The axial flux machine has a rotor with a rotor carrier, magnets held on the rotor carrier, and cooling channels running within the rotor carrier. Cooling air can flow through each of the cooling channels to cool the rotor. Each cooling channel has an inlet through which the cooling air can be introduced into the respective cooling channel. Furthermore, each cooling channel has at least one outlet through which the cooling air can be discharged.

[0004] The object of the present invention is to further develop an axial flow machine of the type mentioned at the outset in such a way that a particularly advantageous and demand-oriented cooling of the rotor can be realized.

[0005] This object is achieved by an axial flow machine having the features of patent claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0006] In order to further develop an axial flow machine of the type specified in the preamble of patent claim 1 such that particularly advantageous and needs-based cooling of the rotor can be achieved, the invention provides that the axial flow machine has a valve device assigned to the inlets, by means of which a flow cross-section of the respective inlet through which the cooling air can flow can be adjusted, i.e. changed. In particular, the valve device is movable, in particular rotatable, relative to the rotor between a closed position closing the inlets and thus reducing the respective flow cross-section to zero, and at least one open position releasing the inlets, so that in the open position the flow cross-section is greater than zero. Thus, in the open position, cooling air can flow through the respective inlet and thus flow into the respective cooling channel via the respective inlet.In the closed position, no cooling air can flow through the respective inlet and thus flow into the respective cooling channel via the inlet.

[0007] The invention is based in particular on the following findings: Electromagnetic losses in electrical machines generate heat. This heat should be dissipated to avoid a reduction in performance, damage to or destruction of the machine. Especially with axial flux machines (AFM), a maximum temperature should not be exceeded in order to avoid undesirable impairment of the strength of adhesive bonds between the magnets, which can be designed as permanent magnets, for example, and the rotor carrier. At high power levels, natural convection is not sufficient for this. Liquid-cooled rotors are very complex. External ribs on the rotor would lead to high ventilation losses. According to the invention, the valve device is therefore provided which can, for example, open and close automatically and / or depending on the temperature, or can adjust the flow cross-sections.Since the cooling channels run within the rotor carrier, they are internal cooling channels through which heat can be dissipated from the rotor particularly advantageously. In operating states in which cooling of the rotor via the cooling channels is not required or desired, the valve device is, for example, in the closed position. This allows for particularly low-loss operation. In operating states in which cooling of the rotor via the cooling channels is advantageous or desired, the valve device can be in the open position, whereby heat can be dissipated from and in particular from the rotor particularly effectively and efficiently.

[0008] The valve device is, for example, a disk, in particular a closure orifice plate, which is rotatable, for example, about an axis of rotation about which the rotor of the axial flow machine can be rotated relative to a stator of the axial flow machine. For example, the valve device is assigned an actuator, also referred to as an actuator, by means of which the valve device can be moved, in particular rotated, relative to the rotor. The actuator can be automatic and / or temperature-controlled. For example, the actuator can be designed as a bimetal or made of a shape memory alloy. Furthermore, it is conceivable for the actuator to be an electrically operated actuator, in particular an electric motor, so that the valve device can be moved relative to the rotor, for example by means of the actuator using electrical energy.The invention enables demand-based cooling and thus increases the performance and reliability of the axial flux machine compared to conventional solutions. In particular, a reduction in losses allows for particularly efficient operation of the axial flux machine. The previous and following explanations can be readily applied to radial flux machines, so the invention can also be applied to radial flux machines.

[0009] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0010] The drawing shows:

[0011] Fig. 1 shows a partial schematic front view of a first embodiment of a rotor of an axial flow machine;

[0012] Fig. 2 shows a partial schematic longitudinal sectional view of the rotor of the axial flow machine according to Fig. 1;

[0013] Fig. 3 shows a partial schematic longitudinal sectional view of an upper half of a rotor of an axial flow machine in a second embodiment and

[0014] Fig. 4 shows a partial schematic longitudinal sectional view of an upper half of a third embodiment of a rotor of an axial flux machine. In the figures, identical or functionally equivalent elements are provided with the same reference numerals.

[0015] Fig. 1 shows a section in a schematic front view of a rotor 14 of an electrical machine designed as an axial flux machine 10, in particular for a motor vehicle. This means, for example, that the axial flux machine 10 is designed to drive the motor vehicle, in particular purely electrically. Figs. 1 and 2 show a first embodiment of the rotor 14 of the axial flux machine 10. As can be seen in conjunction with Fig. 4, the axial flux machine 10 has a stator 12 and a rotor 14, which can be driven by means of the stator 12 and is therefore rotatable about an axis of rotation 16 relative to the stator 12. Fig. 4 shows only a schematic section of such an axial flux machine 10, which has at least one stator 12 and at least one rotor 14, so that the illustration does not result in any restriction to the type of axial flux machine 10 and is to be seen purely as an example.1 and 2 it can be seen that the rotor 14 has a rotor carrier 18 and magnets 20. For example, the magnets 20 are formed separately from the rotor carrier 18 and held on the rotor carrier 18, in particular by the respective magnet 20 being connected to the rotor carrier 18 by a respective adhesive connection. In particular, the respective magnet 20 is a respective permanent magnet. The rotor 14 also has cooling channels 22 running within the rotor carrier 18. Since the cooling channels 22 run within the rotor carrier 18, respective partial regions of the cooling channels 22 are not visible in Fig. 1, wherein these partial regions are illustrated in Fig. 1 by dashed lines. Cooling air can flow through the respective cooling channel 22, in particular in the radial direction of the rotor 14 from the inside to the outside.For this purpose, the respective cooling channel 22, also referred to as a cooling air channel, has a respective inlet 24, through which the air, in particular from an environment 26 of the rotor 14, can be introduced into the respective cooling channel 22. Furthermore, the respective cooling channel 22 has a respective outlet 28, via which the cooling air flowing through the respective cooling channel 22 can be discharged from the respective cooling channel 22 and guided, for example, into the environment 26. It can be seen that the respective outlets 28 are located further outward in the radial direction of the rotor 14 than the respective inlets 24, which are also referred to as inlets. The respective inlet 24, also referred to as an inlet, runs parallel to the axial direction or obliquely to the axial direction of the rotor 14 and thus to the axial flow machine 10.

[0016] It can also be seen in Fig. 1 that in the first embodiment the cooling channels 22 are divided in the rotor carrier 18, so that each inlet 24 with a starting cooling channel 22 is then assigned a plurality of outlets 28 with a respective cooling channel 22 and thus a plurality of cooling channels 22 and is fluidically connected. For example, in the first embodiment the one inlet 24 with the one cooling channel 22, which then splits into two cooling channels 22, is also assigned two outlets 28 and fluidically connected. Depending on the size and design of a rotor, the branching ratio of the cooling channels can be determined here, since cooling is to take place over the entire circumference, which increases outwards with the radius, so that here the cooling channels 22 cannot be widened arbitrarily for stability reasons and therefore branch out in order to be able to cover the increasing circumference outwards.

[0017] From Fig. 2, it can be seen that the rotor 14 also has a rotor shaft 30, also referred to simply as a shaft. For example, the rotor carrier 18 is connected to the rotor shaft 30 in a rotationally fixed manner. It is conceivable that the rotor carrier 18 is separate from the rotor shaft 30 and connected to the rotor shaft 30 in a rotationally fixed manner.

[0018] In order to be able to realize particularly advantageous and needs-based cooling of the rotor 14, the rotor 14 of the axial flow machine 10, as can be seen particularly well in Fig. 1, has a valve device 32 which is assigned to the inlets 24 and common to the inlets 24 and by means of which a respective flow cross-section of the respective inlet 24 through which the cooling air can flow can be passed. The valve device 32 is rotatable about the axis of rotation 16 relative to the rotor 14, whereby the flow cross-sections of the inlets 24, in particular all of the inlets 24, can be adjusted, in particular simultaneously. In particular, the valve device 32 can be rotated and thus moved about the axis of rotation 16 relative to the rotor 14 between a closed position and at least one open position. In the closed position, the inlets 24 are fluidically blocked by the valve device 32, so that the flow cross-sections are reduced to zero.Thus, no cooling air from the environment 26 can flow through the inlets 24. In the open position, the valve device 32 releases the inlets 24, so that in the open position the flow cross-sections are greater than zero. Thus, air can flow as cooling air from the environment 26 through the inlets 24 and thus into the cooling channels 22. In particular, the valve device 32 can be rotated into several different open positions, in which the flow cross-sections have respective values ​​greater than zero.

[0019] From Fig. 1 it can be seen that the valve device 32 is assigned an actuator 34, by means of which the valve device 32 can be rotated about the axis of rotation 16 relative to the rotor 14 in order to thereby adjust the flow cross-sections. The actuator 34 is, for example, a bimetal. It is also conceivable for the actuator 34 to be formed from a shape memory alloy. Thus, for example, the actuator 34 can be non-destructively deformed by temperature changes in the rotor 14, the temperature changes of which accompany temperature changes in the actuator 34, wherein by deforming the actuator 34 the valve device 32 can be rotated about the axis of rotation 16 relative to the rotor 14. As a result, the flow cross-sections are adjusted, i.e. changed, automatically and as a function of the temperature changes in the rotor 14, so that particularly simple, cost-effective and needs-based cooling of the rotor 14 can be achieved.Overall, it can be seen that the valve device 32 functions as a valve by means of which the flow cross sections and thus a respective quantity of cooling air flowing through the flow cross sections can be adjusted.

[0020] In the first embodiment, the valve device 32 is designed as a perforated orifice plate or as a type of perforated orifice plate. For each inlet 24, the valve device 32 has at least one or exactly one through-opening 36. In the open position, the respective inlet 24 is overlapped by a respective one of the through-openings 36, thereby exposing the respective inlet 24. In the closed position, the inlets 24 are closed by respective wall regions of the valve device 32 adjoining the through-openings 36, in that the inlets 24 are covered by the wall regions in the axial direction of the axial flow machine 10 toward the environment 26.

[0021] In the first embodiment, the respective inlet 24 runs obliquely to the axial direction of the rotor 14, such that the cooling air can flow through the respective inlet 24 along a first flow direction, wherein the first flow direction thus also runs obliquely to the axial direction of the rotor 14. In the first embodiment, the respective outlet 28 also runs obliquely to the axial direction of the rotor 14, such that the cooling air can flow through the respective outlet 28 along a respective second flow direction. The second flow direction thus also runs obliquely to the axial direction of the rotor 14, wherein the second flow direction has a different obliqueness to the axial direction of the rotor 14 than the first flow direction. In particular, the axial component of the two obliques of the flow directions is reversed and in particular, for example, the radial component of the two obliques of the flow directions is the same.Furthermore, it is conceivable that at least one of the two respective flow directions runs parallel to the axial direction of the rotor 14, as is shown at the inlet 24 in a second embodiment in Fig.3.

[0022] Fig. 3 shows a section of a second embodiment of the rotor 14, in which the respective inlet 24 runs in the axial direction of the rotor 14 and the respective outlet 28 runs in the radial direction of the rotor 14, so that the respective first flow direction runs in the axial direction of the rotor 14, illustrated by the arrow 40, and the respective second flow direction runs in the radial direction of the rotor 14, illustrated by the arrows 38.

[0023] In the second embodiment of the rotor 14 in Fig. 3, the valve device 32 is designed, for example, as a cylindrical thin-walled pipe section with radial openings.

[0024] Finally, Fig. 4 shows a section of a third embodiment of a rotor 14 of an axial flow machine 10. In the third embodiment, at least one of the outlets 28 is assigned a heat pipe 44, also referred to as a heat pipe, which, as illustrated by an arrow 46, can be flowed through by the cooling air flowing through the at least one outlet 28 and thus flowing out of the associated cooling channel 22 via the at least one outlet. The heat pipe 44 is a possible embodiment of a heat sink which can absorb heat from or from the cooling air flowing through the at least one outlet 28 and transfer it, for example, to another, in particular liquid, cooling medium or working medium, in particular via cooling fins 48 with which the heat pipe 44 can be provided.The other coolant or working medium can be, for example, water (i.e., cooling water), or oil, so that water or oil cooling is possible. For example, the heat pipe 44 and, for example, the cooling fins 48 are arranged in a circuit.

[0025] In an advantageous further embodiment, the rotor 14 can be cooled not only by the cooling channel 22, but also by an air flow through the air gap 50 between the stator 12 and the rotor 14, which is formed in a disc shape in axial-flow machines. The air gap 50, in its disc shape, can also be used as an additional cooling channel, whereby air gap cooling can be realized or is realized. The air flow through the air gap 50 as a cooling channel is guided along the outer circumference of the rotor 14 back to a rear side of the rotor 14, wherein the cooling air in the circuit can be guided to the rear side of the rotor.The heat can, for example, be extracted directly in the circuit mentioned within a housing of the axial flow machine 10 through the heat pipe 44 and optionally the cooling fins 48 and led to the outside, that is to say to an environment of the housing, in particular of the axial flow machine 10 as a whole, and there dissipated in a heat exchanger, for example to air, oil or water, that is to say to another or the previously mentioned, other coolant.

[0026] For example, the rotor carrier 18 has at least one connecting channel 52, for example designed as a bore, via which the air gap 50 is fluidly connected to the cooling channel 22. Thus, for example, downstream of the heat pipe 44, the cooling air can be divided into a first partial flow and a second partial flow. The first partial flow flows through the cooling channel 22, and the second partial flow flows through the connecting channel 52 and thus through the air gap 50. Upstream of the heat pipe 44, the partial flows are combined, for example, into an overall flow, which is then divided downstream of the heat pipe 44 into the first partial flow and the second partial flow. Thus, through the connecting channels 52, for example designed as connecting bores, at least a portion of the cooling air can be supplied to the air gap 50 between the stator 12 and the rotor 14, thereby realizing the air gap cooling.This air gap cooling is supported by a suction effect of an escaping skin cooling air flow, in particular on a front side of the rotor 14 facing the heat pipe 44.

[0027] List of reference symbols

[0028] 10 axial flux machine

[0029] 12 Stator

[0030] 14 Rotor

[0031] 16 axis of rotation

[0032] 18 rotor carriers

[0033] 20 magnets

[0034] 22 Cooling channel

[0035] 24 entry

[0036] 26 Surroundings

[0037] 28 Exit

[0038] 30 Rotor shaft

[0039] 32 Valve device

[0040] 34 Actuator

[0041] 36 passage opening

[0042] 38 Arrow

[0043] 40 Arrow

[0044] 42 Arrow

[0045] 44 heat pipe

[0046] 46 Arrow

[0047] 48 cooling fins

[0048] 50 air gap

[0049] 52 connecting channel

Claims

Patent claims Axial flux machine (10), with a rotor (14) which has a rotor carrier (18), magnets (20) held on the rotor carrier (18) and cooling channels (22) running within the rotor carrier (18), each of which can be flowed through by cooling air for cooling the rotor (14) and each having an inlet (24) via which the cooling air can be introduced into the respective cooling channel (22), and an outlet (28) via which the cooling air can be discharged from the respective cooling channel (22), characterized by a valve device (32) assigned to the inlets (24), by means of which valve device a flow cross section of the respective inlet (24) through which the cooling air can flow can be adjusted. Axial flow machine (10) according to claim 1, characterized in that the valve device (32) is movable relative to the rotor (14) between a closed position closing the inlets (24) and at least one open position releasing the inlets (24).Axial flow machine (10) according to claim 1 or 2, characterized in that, for adjusting the flow cross-sections, the valve device (32) is rotatable relative to the rotor (14) about a rotational axis (16) about which the rotor (14) is rotatable relative to a stator (12) of the axial flow machine (10). Axial flow machine (10) according to one of the preceding claims, characterized in that. the respective outlet (28) extends in the radial direction or in the axial direction of the axial flow machine (10). Axial flow machine (10) according to one of the preceding claims, characterized in that at least one of the outlets (28) is assigned a heat pipe (44), which can be flowed against by the cooling air flowing through the at least one outlet (28) at least in a partial region.

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