Rotor and electric machine

Abstract

Rotor (1) of an electric machine (2), in particular for a drive train (3) of a motor vehicle (4), comprising a rotor body (5) with a plurality of magnet pockets (6) extending axially through the rotor body (5), in each of which at least one rotor magnet (7) is received, and the rotor magnets (7) are each fixed by means of a plastic body (8) extending in the magnet pockets (6), wherein the rotor body (5) further comprises a plurality of cooling channels (9) extending axially through the rotor body (5), through which a cooling fluid (10) can flow, wherein the cooling channels (9) have an end-face outlet opening (11) in the rotor body (5), from which, during operation of the rotor (1), the cooling fluid (10) is discharged from the cooling channels (9) into the rotor environment, wherein at least one of the plastic bodies (8) with a fluid guide element (12) projects axially out of the rotor body (5) and thus connects with one of the outlet openings (11). interactsthat during operation of the rotor (1) the cooling fluid (10) exiting from the outlet opening (11) is subjected to an axial force component by the fluid guiding element (12) of the plastic body (8), wherein two circumferentially adjacent magnetic pockets (6) in the cross-section of the rotor body (5) each have a V-shaped arrangement (15) with a radially inwardly pointing tip, where The plastic bodies (8) of two circumferentially adjacent V-shaped arrangements (15) emerge axially from the magnet pockets (6) at the first end face (13) of the rotor body (5) and form a substantially W-shaped contour in cross-section, wherein the fluid guide element (12) is formed at the radially outwardly pointing tip (16) of the W-shaped contour.

Description

[0001] The present invention relates to a rotor of an electric machine, in particular for a motor vehicle drive train, comprising a rotor body with a plurality of magnetic pockets extending axially through the rotor body, each pocket containing at least one rotor magnet, and the rotor magnets being fixed by means of a plastic body extending within the magnetic pockets. The rotor body further comprises a plurality of cooling channels extending axially through the rotor body, through which a cooling fluid can flow, and the cooling channels having an outlet opening at the end face of the rotor body, from which the cooling fluid is discharged into the rotor environment during operation of the rotor. The invention further relates to an electric machine.

[0002] Electric motors are increasingly being used for propulsion in motor vehicles to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday usability of electric drives and to offer users the familiar driving comfort.

[0003] A detailed description of an electric drive can be found in an article in the journal ATZ, 113th year, 05 / 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold, entitled: Highly Integrated and Flexible Electric Drive Unit for E-Vehicles. Such drive units are also referred to as e-axles or electrically operated drive trains.

[0004] In addition to purely electric powertrains, hybrid powertrains are also known. Such powertrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling – for example, in urban areas – purely electric operation while simultaneously providing sufficient range and availability, especially on long-distance journeys. Furthermore, it is possible to use both the internal combustion engine and the electric motor simultaneously in certain operating situations.

[0005] In the development of electric motors intended for e-axles and hybrid modules, there is a continuing need to increase their power densities, making the cooling of these electric motors increasingly important. Due to the required cooling capacity, hydraulic fluids, such as cooling oils, have become the standard in most designs for dissipating heat from the thermally stressed areas of an electric motor.

[0006] For the stators of electric machines, for example, shell cooling and end-winding cooling are known from the prior art for implementing cooling of electric machines using hydraulic fluids. While shell cooling transfers the heat generated at the outer surface of the rotor lamination stack into a cooling circuit, in end-winding cooling the heat transfer occurs directly at the conductors outside the rotor lamination stack in the area of ​​the winding ends into the fluid.

[0007] Further improvements are provided by separately designed cooling channels, which are incorporated both into the stator's laminated core (see e.g. EP 3 157 138 A1) and into the slot in addition to the conductors (see e.g. Markus Schiefer: Indirect winding cooling of highly utilized permanent excitation synchronous machines with tooth coil winding, Dissertation, Karlsruhe Institute of Technology (KIT), 2017).

[0008] Concepts are also known in which the windings are directly surrounded by hydraulic fluid to increase power density. Improved cooling with direct contact between hydraulic fluid and the conductor in the slot is already known in principle from the prior art. For example, DE 10 2015 013 018 A1 describes a solution for electric machines with single-tooth windings, where the fluid flows directly around the windings that are wound around the teeth.

[0009] In addition to cooling the stators, it is also generally known to cool the rotors of electric machines. Corresponding designs are disclosed in US 2012 / 0 200 179 A1 and US 2013 / 0 221 772 A1. Both disclose rotors, each comprising a rotor body with a plurality of magnet pockets extending axially through the rotor body, each containing at least one rotor magnet. The rotor magnets are each fixed by means of a plastic body extending within the magnet pockets, the rotor body having a plurality of cooling channels extending axially through it, through which a cooling fluid can flow. The cooling channels have an outlet opening at the end face of the rotor body, from which the cooling fluid is discharged into the rotor environment during operation.

[0010] The object of the invention is to realize a rotor that can provide high cooling capacity while simultaneously offering low manufacturing costs. Furthermore, the object of the invention is to realize an improved electric machine.

[0011] This problem is solved by a rotor of an electric machine, in particular for a drive train of a motor vehicle, comprising a rotor body with a plurality of magnet pockets extending axially through the rotor body, in each of which at least one rotor magnet is received, and the rotor magnets are each fixed by means of a plastic body extending in the magnet pockets, wherein the rotor body further comprises a plurality of cooling channels extending axially through the rotor body, through which a cooling fluid can flow, wherein the cooling channels have an end-face outlet opening in the rotor body, from which, during operation of the rotor, the cooling fluid is discharged from the cooling channels into the rotor environment, wherein at least one of the plastic bodies with a fluid guiding element projects axially out of the rotor body and thus interacts with one of the outlet openings.that, during rotor operation, the cooling fluid exiting the outlet opening is subjected to an axial force component by the fluid guide element of the plastic body. Furthermore, it is provided that two circumferentially adjacent magnet pockets in the cross-section of the rotor body each have a V-shaped arrangement with a radially inwardly pointing tip. Likewise, it is provided that the plastic bodies of two circumferentially adjacent V-shaped arrangements extend axially from the magnet pockets at the first end face of the rotor body and form a substantially W-shaped contour in cross-section, with the fluid guide element being formed at the radially outwardly pointing tip of the W-shaped contour.

[0012] This offers the advantage that the fluid guide element, for example during transfer molding or an injection molding process for fixing the stator magnets, can be integrally formed with the plastic body, making the fluid guide element particularly cost-effective to manufacture. Plastic as a material also has the further advantage of offering many degrees of freedom in terms of its geometric shape. This ensures that the function of the electric machine is not negatively affected. Bringing the oil closer to the magnets is also desirable because this is where the thermal hotspot is located, and this further improves cooling.

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

[0014] A rotor is the rotating part of an electric machine. The rotor includes, in particular, a rotor shaft. The rotor shaft can be hollow, which reduces weight and allows the supply of lubricant or coolant to the rotor body. Preferably, the hollow shaft of the contactless energy transmission device is a rotor shaft of an electric machine that is at least partially hollow.

[0015] For the purposes of the invention, a rotor body is understood to be the rotor without a rotor shaft. The rotor body therefore comprises, in particular, a rotor lamination stack, permanent magnets inserted into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack, and any axial cover parts for closing the pockets.

[0016] The rotor preferably comprises a plurality of rotor bodies. The rotor bodies are particularly preferably formed with substantially the same components, and especially with substantially identical components. It is most preferably that the rotor bodies are formed from rotor laminations of the same components, and especially with substantially identical components. The rotor bodies are therefore particularly preferably formed from a rotor lamination stack, which is composed of a plurality of laminated individual laminations, or rotor laminations, generally made of electrical steel, which are stacked and bundled on top of each other to form a stack, the so-called rotor lamination stack. The individual laminations can be held together in the rotor lamination stack by gluing, welding, or screwing. A rotor lamination stack can also, in particular, include permanent magnets inserted into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack.It is possible that the rotor lamination stacks are interlocked, meaning they are arranged at an angle to each other. This interlocking can be linear or V-shaped to avoid or at least reduce axial forces. The cooling channels are then preferably designed so that no radial undercut is formed and that the cooling fluid can flow out axially.

[0017] The term "rotor magnet" refers to the permanent magnets to be inserted into the pockets of the rotor lamination stack. Permanent magnets can preferably be inserted into the pockets of the rotor lamination stack. Each pocket can contain either a single larger rotor magnet designed as a bar magnet or several smaller permanent magnet elements.

[0018] A rotor lamination stack can, in particular, form a rotor body. A rotor lamination stack is understood to be a plurality of laminated individual sheets, usually made of electrical steel, which are stacked and packaged on top of each other to form a stack, the so-called rotor lamination stack. The individual sheets can then be held together in the stack by gluing, welding, or bolting. A rotor lamination stack can also include, in particular, magnetic elements inserted into the pockets of the rotor lamination stack or fixed around its circumference, as well as any axial cover parts for closing the pockets, and the like.

[0019] The electric machine can be designed, in particular, as a rotary machine. The rotary machine can be configured, in particular, as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and stator extend in a radial direction. The air gap is the gap existing between the rotor and the stator. In a radial flux machine, this is an annular gap with a radial width corresponding to the distance between the rotor bodies.

[0020] The electric machine is intended for use within the powertrain of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned to enable vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h. The electric motor preferably has a power output greater than 50 kW, preferably greater than 80 kW, and especially greater than 150 kW. It is further preferred that the electric machine provides rotational speeds greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, and most preferably greater than 15,000 rpm.

[0021] For the purposes of this application, motor vehicles are defined as land vehicles that are moved by mechanical power and are not bound to railway tracks. A motor vehicle may, for example, be selected from the groups of passenger cars, trucks, mopeds, light vehicles, motorcycles, buses, or tractors.

[0022] According to an advantageous embodiment of the invention, the cooling channels can be arranged in a circular path within the cross-section of the rotor body. The advantage of this embodiment is that a particularly uniform cooling performance can be achieved. It is particularly preferred that the diameter of the circular path is selected such that the cooling channels run radially below the rotor magnets. It is further preferred that the center of the circular path is coaxial with the axis of rotation of the rotor.

[0023] According to an advantageous embodiment of the invention, the fluid guiding element can be arranged radially above its associated outlet opening. According to a further preferred embodiment of the invention, the fluid guiding element can also be positioned radially aligned with its associated outlet opening, thereby enabling a particularly short fluid path between the outlet opening and the fluid guiding element, which contributes to particularly good and controlled fluid flow.

[0024] Furthermore, according to an equally advantageous embodiment of the invention, it can be provided that a fluid guide element is assigned to all outlet openings on a first end face of the rotor body and / or that a fluid guide element is assigned to all outlet openings on a second end face of the rotor body, which contributes to a particularly good cooling effect.

[0025] Furthermore, the invention can also be further developed in such a way that the outlet openings are positioned in the cross-section of the rotor body between two V-shaped arrangements of the magnet pockets. Placing the cooling channel between the poles has the advantage that this location has the fewest negative influences on the electric machine from a strength and electromagnetic perspective.

[0026] It may also be advantageous to further develop the invention in such a way that the fluid guiding element is designed as a ramp which has a ramp surface inclined axially away from the rotor body and radially outwards, thereby making particularly effective cooling possible.

[0027] According to a further preferred embodiment of the invention, it can be provided that the ramp surfaces of a plurality of fluid guide elements formed on a first end face are designed differently from one another. This ensures that sufficient cooling of the winding head can always be guaranteed, regardless of the rotational speed of the rotor.

[0028] The object of the invention is further solved by an electric machine comprising a hollow cylindrical stator and a rotor rotatably arranged in the stator, wherein a stator winding is received in the stator, which extends axially from the two end faces of the stator, forming a winding head in each case, wherein the rotor is designed according to one of the preceding claims and the fluid guide element is configured such that, during operation of the electric machine, cooling fluid is directed to one of the winding heads.

[0029] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0030] It shows: Fig. 1. A motor vehicle with an electric powertrain in a schematic block diagram, Fig. 2 an electrical machine in a schematic axial section view, Fig. 3 an electric machine in an axial section view, Fig. 4 a rotor in a first perspective axial section view, Fig. 5 a rotor in a second perspective axial section view.

[0031] The invention is explained using an electric machine 2 for a drive train 3 of a motor vehicle 4, as is also exemplified in the Fig. 1 is outlined.

[0032] The electric machine 2 is in the Fig. 2 shown in an axial section view.

[0033] The electric machine 2 comprises a hollow cylindrical stator 19 and a rotor 1 rotatably arranged in the stator 19, wherein a stator winding 20 is accommodated in the stator 19, which extends axially from the two end faces of the stator 19, forming a winding head 21 at each end. The rotor body 5 of the rotor 1, formed from a plurality of stacked rotor laminations 22, is non-rotatably connected to the rotor shaft 23 and has a fluid guide element 12 configured such that, during operation of the electric machine 2, cooling fluid 10 is directed to one of the winding heads 21. This is demonstrated by the Fig. 2-5 explained in more detail.

[0034] The rotor 1 of the electric machine 2 has a rotor body 5 with a plurality of magnetic pockets 6 extending axially through the rotor body 5, each containing at least one rotor magnet 7. The rotor magnets 7 are each fixed by means of a plastic body 8 extending within the magnetic pockets 6. The rotor body 5 further comprises a plurality of cooling channels 9 extending axially through the rotor body 5, through which a cooling fluid 10 can flow. The cooling channels 9 each have an outlet opening 11 at their end face in the rotor body 5, from which the cooling fluid 10 is discharged into the rotor environment during operation of the rotor 1.

[0035] One of the plastic bodies 8 protrudes axially from the rotor body 5 with a fluid guiding element 12 and interacts with one of the outlet openings 11 in such a way that, during operation of the rotor 1, the cooling fluid 10 exiting from the outlet opening 11 is subjected to an axial force component by the fluid guiding element 12 of the plastic body 8.

[0036] The fluid guide element 12 is arranged radially above its associated outlet opening 11 and is positioned radially aligned with its associated outlet opening 11.

[0037] All outlet openings 11 are assigned a fluid guide element 12 on a first end face 13 of the rotor body 5, and all outlet openings 11 are assigned a fluid guide element 12 on a second end face 14 of the rotor body 5.

[0038] Each pair of circumferentially adjacent magnetic pockets 6 has a V-shaped arrangement 15 in the cross-section of the rotor body 5 with a radially inwardly pointing tip. The outlet openings 11 are positioned in the cross-section of the rotor body 5 between two V-shaped arrangements 15 of the magnetic pockets 6.

[0039] What the Fig.As can also be seen from Figure 4, the plastic bodies 8 of two circumferentially adjacent V-shaped arrangements 15 protrude axially from the magnet pockets 6 at the first end face 13 of the rotor body 5 and form a substantially W-shaped contour in cross-section, with the fluid guide element 12 being formed at the radially outwardly projecting tip 16 of the W-shaped contour. The fluid guide element 12 is designed as a ramp 17, which has a ramp surface 18 inclined axially away from the rotor body 5 and radially outward. In the case of a plurality of fluid guide elements 12 formed at a first end face 13, their ramp surfaces 18 are shaped differently from one another.

[0040] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Insofar as the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy. Reference symbol list 1 Rotor 2 electric machine 3 Powertrain 4 Motor vehicle 5 rotor bodies 6 magnetic pockets 7 Rotor magnet 8 plastic bodies 9 cooling channels 10 Cooling fluid 11 Exit opening 12 Fluid guide element 13 Front 14 Front 15 Arrangement 16 top 17 Ramp 18 ramp area 19 Stator 20 Stator winding 21 winding heads 22 Rotor plate 23 Rotor shaft

Claims

[1] Rotor (1) of an electric machine (2), in particular for a drive train (3) of a motor vehicle (4), comprising a rotor body (5) with a plurality of magnet pockets (6) extending axially through the rotor body (5), in each of which at least one rotor magnet (7) is received, and the rotor magnets (7) are each fixed by means of a plastic body (8) extending in the magnet pockets (6), wherein the rotor body (5) further comprises a plurality of cooling channels (9) extending axially through the rotor body (5), through which a cooling fluid (10) can flow, wherein the cooling channels (9) have an end-face outlet opening (11) in the rotor body (5), from which, during operation of the rotor (1), the cooling fluid (10) is discharged from the cooling channels (9) into the rotor environment, wherein at least one of the plastic bodies (8) with a fluid guide element (12) projects axially out of the rotor body (5) and thus connects with one of the outlet openings (11) works together,that during operation of the rotor (1) the cooling fluid (10) exiting from the outlet opening (11) is subjected to an axial force component by the fluid guiding element (12) of the plastic body (8), wherein two circumferentially adjacent magnetic pockets (6) in the cross-section of the rotor body (5) each have a V-shaped arrangement (15) with a radially inwardly pointing tip, where The plastic bodies (8) of two circumferentially adjacent V-shaped arrangements (15) emerge axially from the magnet pockets (6) at the first end face (13) of the rotor body (5) and form a substantially W-shaped contour in cross-section, wherein the fluid guide element (12) is formed at the radially outwardly pointing tip (16) of the W-shaped contour. [2] Rotor (1) according to claim 1, where the fluid guiding element (12) is arranged radially above the outlet opening (11) associated with it. [3] Rotor (1) according to claim 1 or 2, where the fluid guiding element (12) is positioned radially aligned with the outlet opening (11) associated with it. [4] Rotor (1) according to any one of the preceding claims, where all outlet openings (11) on a first end face (13) of the rotor body (5) are assigned a fluid guide element (12) and / or all outlet openings (11) on a second end face (14) of the rotor body (5) are assigned a fluid guide element (12). [5] Rotor (1) according to any one of the preceding claims, where the outlet openings (11) are positioned in the cross-section of the rotor body (5) between two V-shaped arrangements (15) of the magnet pockets (6). [6] Rotor (1) according to any one of the preceding claims, where the fluid guiding element (12) is designed as a ramp (17) which has a ramp surface (18) inclined axially away from the rotor body (5) and radially outwards. [7] Rotor (1) according to claim 6, where in a plurality of fluid guiding elements (12) formed on a first end face (13) whose ramp surfaces (18) are formed differently from each other. [8] Electric machine (2) comprising a hollow cylindrical stator (19) and a rotor (1) rotatably arranged in the stator (19), wherein a stator winding (20) is received in the stator (19) which exits axially from the two end faces of the stator (19) forming a winding head (21) in each case, characterized by , that the rotor (1) is designed according to one of the preceding claims and the fluid guide element (12) is configured such that during operation of the electric machine (2) cooling fluid (10) is directed to one of the winding heads (21).

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