Rotor

Abstract

The invention relates to a rotor (1) of an electric machine (2), in particular for a power train (3) of a motor vehicle (4), comprising a rotor shaft (5) and a rotor body (6) which is rotationally fixed to the rotor shaft (5) and is formed by a plurality of stacked rotor laminations (13), and a plurality of first cooling channels (7) extending in an axial direction through the rotor body (6) extend through the plurality of rotor laminations. The rotor shaft (5) extends in a radial direction and has a first rotor shaft channel (9) through which a cooling fluid (8) can flow, and the first rotor shaft channel is fluidly connected to a first supply channel (10) extending through the rotor body (6) in the radial direction and leading to one of the first cooling channels (7) extending in the axial direction. The first supply channel (10) in the rotor body (6) has a first channel outlet (11) with a first fluid guide element (12), the first fluid guiding element is designed such that a cooling fluid (8) to which a centrifugal force is applied during operation of the rotor (1) is supplied with a force component acting in the axial direction when the cooling fluid exits the first channel outlet (11).

Description

Technical Field

[0001] The invention relates to a rotor for an electric machine, in particular for a powertrain of a motor vehicle, the rotor comprising a rotor shaft and a rotor body, the rotor body being rotationally fixed to the rotor shaft and being formed by a plurality of rotor laminations which are stacked, and through which a plurality of first cooling channels extending through the rotor body in an axial direction extend, wherein the rotor shaft has a first rotor shaft channel extending in a radial direction and has a first rotor shaft channel through which a cooling fluid can flow and which is fluidically connected to a first supply channel extending through the rotor body in a radial direction and opening into a first cooling channel in the first cooling channels extending in the axial direction. Background Art

[0002] Electric motors are increasingly used to drive motor vehicles, creating an alternative to fossil fuel-demanding internal combustion engines. Considerable efforts have been made to improve the suitability of electric drives for everyday use and also to be able to provide users with the driving comfort they are accustomed to.

[0003] A detailed description of the electric drive can be found in the article by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold in the German automobile magazine ATZ, Vol. 113, May 2011, pages 360 to 365, entitled: Hochintegrativ und Flexibel Elektrische Antriebseinheit für E-Fahrzeuge [Highly Integrative and Flexible Electric Drive Unit for E-Vehicles]. Such a drive unit is also referred to as an electric axle or an electrically operable powertrain.

[0004] In addition to purely electrically operated powertrains, hybrid powertrains are also known. Such powertrains of hybrid vehicles generally include a combination of an internal combustion engine and an electric motor and enable, for example, a purely electric operating mode in urban areas while allowing both sufficient range and usability, in particular also in off-road driving. In addition, in certain operating situations, drive can also be provided simultaneously by the internal combustion engine and the electric motor.

[0005] In the development of electric machines intended for electric axles or hybrid modules, the need to continuously increase the power density of the electric machines makes the cooling of the electric machines required for this increasingly important. Due to the necessary cooling capacity, hydraulic fluids such as cooling oils have been established in most concepts for dissipating heat from the heat-exposed areas of the electric machine.

[0006] For example, for the stator of an electric machine, jacket cooling and winding head cooling are known from the prior art for realizing electric machine cooling by means of a hydraulic fluid. While jacket cooling transfers the heat generated on the outer surface of the laminated rotor core to the cooling circuit, in the case of winding head cooling the heat is transferred directly to the fluid at the conductor in the region of the winding head outside the laminated rotor core.

[0007] Further improvements are provided by separate cooling channels which are introduced both into the stator laminated core (see, for example, EP 3 157 138 A1) and into grooves outside the conductors (see, for example, Markus Schiefer: Indirekte Wicklungskihlung von hochausgenutzten permanenterregten Synchronmaschinen mit Zahnspulenwicklung [Indirect Winding Cooling of Highly Utilized Permanently Excited Synchronous Machines with Toothed Coil Winding], thesis, Karlsruhe Institute of Technology (KIT), 2017).

[0008] The idea of ​​flowing hydraulic fluid directly around the winding to increase the power density is also known. Improving cooling by direct contact of the hydraulic fluid and the conductor in the groove is known from the prior art itself. For example, DE102015013018 A1 describes a solution for an electric machine with a single-tooth winding, in which the fluid flows directly around the winding, which is wound around the tooth.

[0009] In addition to cooling the stator, it is generally also known to cool the rotor of an electric machine. Summary of the invention

[0010] The object of the present invention is to achieve a rotor which is able to provide high cooling performance while having low leakage rate and manufacturing costs.

[0011] This object is achieved by a rotor of an electric machine, in particular of a powertrain for a motor vehicle, the rotor comprising a rotor shaft and a rotor body, the rotor body being rotationally fixed to the rotor shaft and being formed by a plurality of stacked rotor laminations, and a plurality of first cooling channels extending axially through the rotor body extending through the plurality of rotor laminations, wherein the rotor shaft has a first rotor shaft channel extending in the radial direction and having a first rotor shaft channel through which cooling fluid can flow, and the first rotor shaft channel is fluidly connected to a first supply channel leading to a first cooling channel of the plurality of first cooling channels extending in the axial direction, wherein the first supply channel in the rotor body has a first channel outlet, the first channel outlet being provided with a first fluid guiding element, the first fluid guiding element being designed such that the cooling fluid to which a centrifugal force is applied during operation of the rotor is supplied with a force component acting in the axial direction when the cooling fluid leaves the first channel outlet.

[0012] This provides the following advantages: Leakage flow can be prevented by the direct radial load in the gap between two rotor laminations in the rotor body. By subjecting the cooling fluid to an axial force component, the impact velocity of the cooling fluid on the radially outer surface of the cooling channel is also reduced, which can also contribute to minimizing or completely avoiding leakage flow.

[0013] First, the individual elements of the subject matter claimed in the invention are explained in the order of their relevance or mention in the claims, and then particularly preferred embodiments of the subject matter of the invention are described.

[0014] The rotor is the rotating part of the electric machine. The rotor particularly includes a rotor shaft. The rotor shaft can be hollow, which on the one hand results in weight reduction and on the other hand allows the supply of lubricant or coolant to the rotor body. Preferably, the hollow shaft of the non-contact energy transmission device is the rotor shaft of the rotor of the electric machine, which is at least partially hollow.

[0015] For the purposes of the present invention, the rotor body is understood to mean the rotor without the rotor shaft. Thus, the rotor body is particularly made of a laminated rotor core, permanent magnets inserted into recesses of the laminated rotor core or fixed to the circumference of the laminated rotor core, and any axial covering components for closing the recesses.

[0016] The rotor preferably has a plurality of rotor bodies. Particularly preferably, the rotor bodies are formed substantially from the same components, particularly substantially identical components. Highly preferably, the rotor bodies are formed substantially from rotor laminations of the same components, particularly substantially identical rotor laminations. Thus, the rotor bodies are particularly preferably formed from a laminated rotor core, which is composed of a plurality of laminated individual sheets or rotor laminations, which are typically made of electrical steel, and which are layered and stacked one on top of the other to form a stack, which is referred to as a laminated rotor core. The individual laminations can be held together in the laminated rotor core by gluing, welding or screwing. In particular, the laminated rotor core can also have permanent magnets, which are inserted into cavities of the laminated rotor core or are fixed circumferentially to the laminated rotor core.

[0017] The rotor magnets are understood to be permanent magnets introduced into the cavities of the laminated rotor core. The permanent magnets can preferably be inserted into the cavities of the laminated rotor core. A single larger rotor magnet designed as a bar magnet or a plurality of smaller permanent magnet elements can be provided for each cavity.

[0018] The laminated rotor core can in particular be formed as a rotor body. The laminated rotor core is understood to mean a plurality of laminated individual cover layers or rotor laminations, which are typically made of electrical steel sheets and are stacked and encapsulated one on top of the other to form a stack or a so-called "laminated rotor core". The individual cover layers can then be held together in the laminated core by adhesive bonding, welding or screwing. In particular, the laminated rotor core can also have magnetic elements inserted into the cavities of the laminated rotor core or magnetic elements fixed circumferentially to the laminated rotor core, as well as any axial cover components for closing the cavities, etc.

[0019] In particular, the electric machine can be designed as a rotary machine. In particular, the rotary machine can be constructed as a radial flow machine. Thus, the radial flow machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and the stator extend in the radial direction. The gap between the rotor and the stator is referred to as the air gap. In a radial flow machine, the air gap is an annular gap, the radial width of which corresponds to the distance between the rotor body and the stator body.

[0020] The electric machine is in particular intended for use in a powertrain of a hybrid-driven motor vehicle or a fully electric-driven motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds of more than 50 km / h, preferably more than 80 km / h, and in particular more than 100 km / h can be achieved. The electric motor particularly preferably has an output of more than 50 kW, preferably more than 80 kW, and in particular more than 150 kW. Furthermore, it is preferred that the electric machine provides a speed of more than 8000 rpm, particularly preferably more than 12,000 rpm, and very particularly preferably more than 1500 rpm.

[0021] For the purposes of the present application, a motor vehicle is a land vehicle that is moved by machine power and is not restricted to a railway track. The motor vehicle can be selected, for example, from the group consisting of: passenger cars, trucks, scooters, light motor vehicles, motorcycles, buses / coaches or tractors.

[0022] According to an advantageous design of the invention, it can be provided that the cooling channels are arranged on a circular path in the cross-section of the rotor body. The advantage of this design is that a particularly uniform cooling performance can be achieved. Particularly preferably, the diameter of the circular path is selected such that the cooling channels run radially below the rotor magnets. Further preferably, the center of the circular path extends coaxially with the rotational axis of the rotor.

[0023] According to an advantageous embodiment of the invention, it can be provided that the rotor body has a first cover plate that rests on the first front end of the rotor body and the first cover plate forms and / or has a first supply channel. The supply channel can be designed as a partially closed or fully closed channel, or partially or fully as a groove. The advantage of this design is that the supply channel only needs to be formed in the cover plate.

[0024] According to a further preferred refinement of the invention, it can also be provided that the first supply channel includes a first groove formed in the first cover plate, and the first groove together with the rotor laminations of the rotor body resting on the front side of the first cover plate defines the first supply channel. This makes it possible to provide a particularly cost-effective variant of the supply channel in terms of manufacturing technology.

[0025] Furthermore, according to an equally advantageous embodiment of the invention, it can be provided that the first fluid guiding element is formed as a first ramp that is inclined in the axial direction in the first groove. The advantageous effect of this design is based on the fact that the ramp can be manufactured particularly easily and cost-effectively.

[0026] According to another particularly preferred embodiment of the invention, it can be provided that the first fluid guiding element is designed as a ramp that is inclined in the axial direction and projects from the plane of the first cover plate, which has proven to be particularly advantageous for avoiding leakage flow.

[0027] Furthermore, the invention can be further improved such that the rotor shaft has a second rotor shaft channel extending in the radial direction and a first rotor shaft channel through which cooling fluid can flow and is fluidly connected to the first supply channel. The first supply channel extends in the radial direction through the rotor body and leads to one of the second cooling channels extending in the axial direction. The second supply channel in the rotor body has a second channel outlet with a second fluid guiding element designed such that during operation of the rotor, the cooling fluid subjected to centrifugal force is supplied with a force component acting in the axial direction when the cooling fluid exits the second channel outlet. It can also be advantageous to further develop the invention such that the rotor body has a second cover plate that rests on the second front end of the rotor body and forms and / or has a second supply channel. The advantage of this design is that the rotor can be cooled from several sides.

[0028] In a likewise preferred embodiment variant of the invention, it can also be provided that the first supply channel and the second supply channel are configured such that the cooling fluid flows through the cooling channels connected to the first supply channel and the second supply channel in different directions, which also helps to improve the cooling performance.

[0029] According to another preferred embodiment of the subject matter of the invention, it can be provided that the first cover plate has a first outlet opening extending axially through the first cover plate and fluidly connected to the first cooling channel, and / or the second cover plate has a second outlet opening extending axially through the second cover plate and fluidly connected to the second cooling channel, so that a defined outlet point for the cooling fluid from the rotor body can be defined.

[0030] Finally, the invention can also be advantageously designed such that the first cover plate and / or the second cover plate have a sensor reading area through which the rotor speed and / or the rotor position can be determined by a sensor. This provides the advantage of enabling a high degree of system integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will be described in more detail below with reference to the drawings without limiting the general concept of the invention.

[0032] In the drawings:

[0033] Figure 1 A motor vehicle with an electric powertrain is shown in a schematic block diagram,

[0034] Figure 2 A schematic axial cross-sectional view of the electric machine is shown,

[0035] Figure 3 The rotor is shown in an axial sectional view,

[0036] Figure 4 A detailed view of the channel outlet of the supply channel is shown in an axial sectional view,

[0037] Figure 5 A front view of the first cover plate of the rotor is shown,

[0038] Figure 6 A front view of the second cover plate of the rotor is shown,

[0039] Figure 7 A front view of the rotor body is shown,

[0040] Figure 8 The first cover sheet is shown in a first front view, a second front view and a side view. DETAILED DESCRIPTION

[0041] The present invention is explained by using as an example an electric machine 2 of a powertrain 3 for a motor vehicle 4. Such a powertrain 3 is shown as Figure 1 an example in

[0042] As can be seen from Figure 5 the rotor 1 of the electric machine 2, which is rotatably mounted in a hollow cylindrical stator 29, includes a rotor shaft 5 and a rotor body 6 which is rotationally fixed to the rotor shaft 5 and is formed by a plurality of stacked rotor laminations 13, and a plurality of first cooling channels 7 which extend axially through the rotor body 6 extend through the plurality of rotor laminations. The rotor shaft 5 has a first rotor shaft channel 9 which extends in the radial direction and through which a cooling fluid 8 can flow, and the first rotor shaft channel is fluidly connected to a first supply channel 10 which extends in the radial direction through the rotor body 6 and leads to one of the first cooling channels 7 which extends in the axial direction.

[0043] The first supply channel 10 in the rotor body 6 has a first channel outlet 11 which is provided with a first fluid guiding element 12 which is designed such that the cooling fluid 8 which is subject to centrifugal force during operation of the rotor 1 is subject to a force component acting in the axial direction when the cooling fluid leaves the first channel outlet 11. This can be clearly understood from an overview of Figures 2 to 4 as shown in

[0044] Figures 2 to 7It is also shown that the rotor shaft 5 has a second rotor shaft passage 19 extending in the radial direction through which the cooling fluid 8 can flow, and the second rotor shaft passage is fluidly connected to a second supply passage 20 extending in the radial direction through the rotor body 6 and leading to one of the second cooling passages 17 extending in the axial direction. The second supply passage 20 in the rotor body 6 has a second passage outlet 21, and the second passage outlet is provided with a second fluid guiding element 22 which is designed such that during the operation of the rotor 1, the cooling fluid 8 subjected to centrifugal force is acted upon by a force component in the axial direction when the cooling fluid leaves the second passage outlet 21.

[0045] In the illustrated embodiment, the first supply passage 10 and the second supply passage 20 are configured such that the cooling fluid 8 flows through the cooling passage 7 connected to the first supply passage and the cooling passage 17 connected to the second supply passage in different directions.

[0046] For this purpose, the rotor body 6 has a correspondingly designed second cover plate 24 which rests on the second front end portion of the rotor body 6, and the second cover plate 24 forms and / or has a second supply passage 20 clearly visible from Figure 2 The first cover plate 14 has a first outlet opening 25 which axially extends through the first cover plate 14 and is fluidly connected to the first cooling passage 7, so that during the operation of the electric machine 2, the winding head of the stator 29 can be supplied with the cooling fluid 8 via the outlet opening 25.

[0047] Similarly, the second cover plate 24 also has a second outlet opening 26 which axially extends through the second cover plate 24 and is fluidly connected to the second cooling passage 17, so that the second winding head of the stator 29 of the electric machine 2 can also be supplied with the cooling fluid 8.

[0048] As can be clearly seen from Figure 4 the first supply passage 10 is designed such that it only slightly protrudes beyond the radially inner end of the first cooling passage 7. The first cooling passage 7 has a first fluid guiding element 12 which protrudes into the first cooling passage 7 and is designed as a first ramp 16 in the illustrated embodiment. The first fluid guiding element 12 ensures that the radially outward flowing cooling fluid 8 is guided into the first cooling passage 7. Cooling problems caused by leakage losses in the gap above the supply passage 10 in the radial direction can be avoided in this way.

[0049] Accordingly, the first fluid guiding element 12 serves as a flow separation edge. The cooling fluid 8 flies radially outwards on the ramp 16 with an axial vector applied through the ramp 16 until the cooling fluid impinges on the outer radius of the first cooling channel 7. Due to the free flight, the radial velocity is lower than the velocity when the cooling fluid 8 is accelerated to the outer radius of the cooling channel 7 in a purely radial manner, i.e., without the axial deflection through the first fluid guiding element 12. Due to the combination of the lower radial velocity and the forced axial deflection, the cooling fluid 8 flows through the first cooling channel 7 of the rotor 1, rather than such radial-axial deflection occurring at the annular gap on the front contact surface, for example, between the rotor body 6 and the first cover plate 14.

[0050] The ramp 16 can be manufactured cost-effectively, for example, by inserting it into an aluminum stamping part. The passage is preferably located outside the flat surface of the sensor reading area 27.

[0051] In the illustrated embodiment, the cooling of the rotor 1 is achieved by introducing the cooling fluid 8 from both sides into the plurality of star-shaped supply channels 10, 20 in the cover plates 14, 24. The rotor 1 is flowed through alternately from left to right. This allows for symmetric oiling and cooling of the rotor 1 and the stator winding.

[0052] From Figure 3 It is further evident that the rotor body 6 has a first cover plate 14 that rests on the first front end of the rotor body 6, and the first cover plate 14 forms and / or has a first supply channel 10. The first supply channel 10 is formed as a first groove 15 in the first cover plate 14, and the first groove, together with the rotor laminations 13 of the rotor body 6 that rest on the front side of the first cover plate 14, defines the first supply channel 10, as can also be clearly seen in Figure 4 The first fluid guiding element 12 is formed as a first ramp 16 that is inclined in the axial direction in the first groove 15, where the first ramp continues into a ramp 16 that is inclined in the axial direction and protrudes from the plane of the first cover plate 14.

[0053] Finally, Figure 8 It is shown that the first cover plate 14 has an annular sensor reading area 27, and the rotor speed and / or rotor position can be determined by the sensor 28 by means of this sensor reading area.

[0054] The present invention is not limited to the embodiments shown in the drawings. Therefore, the above description should not be considered restrictive, but rather illustrative. The appended claims should be understood to mean that the stated features exist in at least one embodiment of the present invention. This does not exclude the existence of other features. In the case where the claims and the above description define a "first" feature and a "second" feature, such naming is used to distinguish between two features of the same type and does not limit the priority order.

[0055] List of reference numerals

[0056] 1 Rotor

[0057] 2 Electric motor

[0058] 3 Power train

[0059] 4 Motor vehicle

[0060] 5 Rotor shaft

[0061] 6 Rotor body

[0062] 7 Cooling channel

[0063] 8 Cooling fluid

[0064] 9 Rotor shaft channel

[0065] 10 Supply channel

[0066] 11 Channel outlet

[0067] 12 Fluid guiding element

[0068] 13 Rotor lamination

[0069] 14 Cover plate

[0070] 15 Groove

[0071] 16 Ramp

[0072] 17 Cooling channel

[0073] 19 Rotor shaft channel

[0074] 20 Supply channel

[0075] 21 Channel outlet

[0076] 22 Fluid guiding element

[0077] 24 Cover plate

[0078] 25 Outlet opening

[0079] 26 Outlet opening

[0080] 27 Sensor reading area

[0081] 28 Sensor

[0082] 29 Stator

Claims

1. A rotor (1) of an electric machine (2), in particular of a powertrain (3) of a motor vehicle (4), said rotor comprising a rotor shaft (5) and a rotor body (6), said rotor body being rotationally fixed to said rotor shaft (5) and being formed by a plurality of stacked rotor laminations (13), a plurality of first cooling channels (7) extending axially through said rotor body (6) extending through said plurality of rotor laminations, said rotor shaft (5) having a first rotor shaft channel (9) extending in the radial direction through which a cooling fluid (8) can flow, said first rotor shaft channel being fluidly connected to a first supply channel (10) extending in said radial direction through said rotor body (6), said first supply channel leading to one of said first cooling channels (7) extending in said axial direction. Characterized in that, said first supply channel (10) in said rotor body (6) has a first channel outlet (11), said first channel outlet being provided with a first fluid guiding element (12), said first fluid guiding element being designed such that the cooling fluid (8) on which a centrifugal force acts during operation of said rotor (1) is supplied with a force component acting in said axial direction when said cooling fluid leaves said first channel outlet (11).

2. The rotor (1) according to claim 1, Characterized in that, said rotor body (6) has a first cover plate (14), said first cover plate resting on a first front end portion of said rotor body (6), and said first cover plate (14) forming and / or having said first supply channel (10).

3. The rotor (1) according to claim 1 or 2, Characterized in that, said first supply channel (10) comprises a first groove (15) formed in said first cover plate (14), said first groove and the rotor laminations (13) of said rotor body (6) resting on a front side portion of said first cover plate (14) together defining said first supply channel (10).

4. The rotor (1) according to claim 2 or 3, Characterized in that, said first fluid guiding element (12) is formed as a first ramp (16) inclined in said axial direction in said first groove (15).

5. The rotor (1) according to any one of claims 2 to 4, Characterized in that, said first fluid guiding element (12) is designed as a ramp (16) inclined in said axial direction and protruding from the plane of said first cover plate (14).

6. The rotor (1) according to any one of the preceding claims, Characterized in that, The rotor shaft (5) has a second rotor shaft passage (19) extending in the radial direction through which a cooling fluid (8) can flow, and the second rotor shaft passage is fluidly connected to a second supply passage (20) extending in the radial direction through the rotor body (6) and leading to one of the second cooling passages (17) extending in the axial direction. The second supply passage (20) in the rotor body (6) has a second passage outlet (21) with a second fluid guiding element (22), and the second fluid guiding element is designed such that the cooling fluid (8) subjected to centrifugal force during operation of the rotor (1) is supplied with a force component acting in the axial direction when the cooling fluid exits the second passage outlet (21).

7. The rotor (1) according to claim 6, characterized in that, the first supply passage (10) and the second supply passage (20) are configured such that the cooling fluid (8) flows through the cooling passage (7) coupled to the first supply passage and the cooling passage (17) coupled to the second supply passage in different directions.

8. The rotor (1) according to any one of claims 6 to 7, characterized in that, the rotor body (6) has a second cover plate (24) that rests on the second front end of the rotor body (6), and the second cover plate (24) forms and / or has the second supply passage (20).

9. The rotor (1) according to any one of the preceding claims 2 to 8, characterized in that, the first cover plate (14) has a first outlet opening (25) extending axially through the first cover plate (14) and fluidly connected to the first cooling passage (7), and / or the second cover plate (24) has a second outlet opening (26) extending axially through the second cover plate (24) and fluidly connected to the second cooling passage (17).

10. The rotor (1) according to any one of the preceding claims 2 to 9, characterized in that, the first cover plate (14) and / or the second cover plate (24) has a sensor reading area (27), and the rotor speed and / or rotor position can be determined by a sensor (28) via the sensor reading area.

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