Rotor having cooling channel and electric machine having such rotor

Abstract

A rotor (1) for an electric machine (2) of a motor vehicle (4) comprises a rotor body (5) having a plurality of rotor magnets (7) extending axially through the rotor body (5) and located in magnet pockets (6). Each rotor magnet (7) is fixed by means of a plastic body (8) extending in the magnet recess (6). Also located in the rotor body (5) is a plurality of axial cooling channels (9) through which a liquid cooling fluid (10) can flow. Each cooling channel (9) has an outlet opening (11) in an end face of the rotor body (5), and a cooling fluid (10) is discharged from the cooling channel (9) to the periphery of the rotor when the rotor (1) is in operation. In this case, the at least one plastic body (8) axially protrudes out of the rotor body (5) via the fluid guiding element (12) and thus interacts with one of the outlet openings (11), such that the cooling fluid (10) exiting the outlet opening (11) is subjected to an axial force component due to the fluid guiding element (12) of the plastic body (8) when the rotor (1) is in operation.

Description

Technical Field

[0001] The invention relates to a rotor for an electric machine, in particular for a drive train of a motor vehicle, the rotor comprising a rotor body having a plurality of magnet pockets extending axially through the rotor body, in each of which at least one rotor magnet is received and each of which is fixed by means of a plastic body extending in the magnet pockets, the rotor body further comprising a plurality of cooling channels extending axially through the rotor body and through which a cooling fluid can flow, the cooling channels having end-face outlet openings in the rotor body, the cooling fluid being discharged from the cooling channels from the outlet openings to the surroundings of the rotor when the rotor is in operation. The invention also relates to an electric motor. Background Art

[0002] Electric motors are increasingly being used to drive motor vehicles in order to create an alternative to fossil fuel-intensive 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 Antriebseinheitfnt 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 drive train.

[0004] In addition to purely electrically operated drive trains, hybrid drive trains are also known. Such drive trains of hybrid vehicles usually include a combination of an internal combustion engine and an electric motor and enable a purely electric operating mode that simultaneously allows both sufficient range and usability, for example in urban areas, but also in particular when driving off-road. 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 properties, hydraulic fluids such as cooling oils have been established in most concepts for removing heat from the thermally loaded areas of the electric machines.

[0006] For example, for the stator of an electric machine, jacket cooling and winding head cooling of the electric machine using hydraulic fluids are known from the prior art. Jacket cooling is the transfer of heat generated at the outer surface of the laminated rotor core into a cooling circuit, while in the case of winding head cooling, the heat transfer into the fluid takes place directly at the conductor outside the laminated rotor core in the region of the winding head.

[0007] Other 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 the slots outside the conductors (see, for example, Markus Schiefer: Indirekte Wicklungskkicklu 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 hydraulic fluid and conductors in the slots is known per se from the prior art. For example, DE 10 2015 013 018 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 can be manufactured at low cost while providing high cooling performance. The object of the present invention is also to achieve an improved electric machine.

[0011] This object is achieved by a rotor of an electric machine, in particular of a drive train for a motor vehicle, the rotor comprising a rotor body having a plurality of magnet recesses, magnet grooves extending axially through the rotor body, and at least one rotor magnet being received in each of the magnet recesses, the rotor magnets each being fixed by means of a plastic body extending in the magnet recess, the rotor body further comprising a plurality of cooling channels extending axially through the rotor body and through which a cooling fluid can flow, the cooling channels having end face outlet openings in the rotor body, the cooling fluid discharging from the cooling channels through the outlet openings into the surroundings of the rotor when the rotor is in operation, and at least one plastic body protruding axially out of the rotor body by means of a fluid guiding element and thus interacting with one of the outlet openings such that the cooling fluid leaving the outlet opening when the rotor is in operation is subjected to an axial force component by the fluid guiding element of the plastic body.

[0012] This offers the advantage that the fluid guiding element can be integrally formed with the plastic body, for example, during transfer molding or injection molding for fixing the stator magnets, whereby the fluid guiding element can be manufactured in a particularly cost-effective manner.

[0013] As a material, plastic has a further advantage in that it offers many geometric degrees of freedom in its shaping.

[0014] First, the individual elements of the subject matter claimed in the present 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 present invention are described.

[0015] The rotor is the rotating (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.

[0016] Therefore, within the meaning 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 the recesses of the laminated rotor core or circumferentially fixed to the laminated rotor core, and any axial covering part for closing the recesses.

[0017] The rotor preferably has a plurality of rotor bodies. Particularly preferably, the rotor bodies are formed substantially of identical parts, especially substantially identical parts. Highly preferably, the rotor bodies are formed of identical, especially substantially identical, rotor laminations. Thus, the rotor bodies are particularly preferably formed by a laminated rotor core and are composed of a plurality of laminated individual sheets or rotor laminations, which are typically made of electrical steel and 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 sheets can be held together in the laminated rotor core by adhesive bonding, welding or screwing. In particular, the laminated rotor core can also have permanent magnets, which are inserted into recesses of the laminated rotor core or are circumferentially fixed to the laminated rotor core. The laminated rotor cores can be offset relative to each other, i.e., arranged at an angle of rotation relative to each other. This offset can be linear or V-shaped to avoid or at least reduce axial forces. Then, the cooling channels are preferably designed such that no radial undercuts are formed and the cooling fluid can flow out axially.

[0018] The permanent magnets to be introduced into the recesses of the laminated rotor core are understood as rotor magnets. The permanent magnets can preferably be introduced into the recesses 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 recess.

[0019] The laminated rotor core can in particular form the rotor body. The laminated rotor core is understood to mean a plurality of laminated individual sheets or rotor laminations, which are typically made of electrical steel and are layered and stacked one on top of the other to form a stack or a so-called laminated rotor core. Then, the individual sheets can be held together in the laminated core by adhesive bonding, welding or screwing. In particular, the laminated rotor core can also have magnetic elements introduced into recesses of the laminated rotor core or circumferentially fixed to the laminated rotor core, as well as any axial covering parts for closing the recesses, etc.

[0020] 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. 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 called the air gap. In a radial flow machine, the air gap is an annular gap having a radial width corresponding to the distance between the rotor body and the stator body in the cross section.

[0021] The electric machine is particularly intended for use in the driveline of a hybrid-electrically or fully electrically 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 speeds of greater than 8000 rpm, particularly preferably greater than 12,000 rpm, and very particularly preferably greater than 15,000 rpm.

[0022] 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.

[0023] According to an advantageous embodiment of the invention, the cooling channels can be arranged in a circular path in the cross-section of the rotor body. The advantage of this embodiment 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 extend radially below the rotor magnets. Further preferably, the center of the circular path extends coaxially with respect to the axis of rotation of the rotor.

[0024] According to an advantageous embodiment of the invention, the fluid guiding element can be arranged radially above the assigned outlet opening. According to a further preferred refinement of the invention, the fluid guiding element can also be radially aligned with the assigned outlet opening, whereby a particularly short fluid path between the outlet opening and the fluid guiding element can be achieved, which contributes to a particularly good and controlled fluid guiding.

[0025] Furthermore, according to a similarly advantageous embodiment of the invention, the fluid guiding element can be assigned to all the outlet openings on the first end face of the rotor body and / or the fluid guiding element can be assigned to all the outlet openings on the second end face of the rotor body, which contributes to a particularly good cooling effect.

[0026] According to another particularly preferred embodiment of the invention, two magnet recesses adjacent circumferentially in the cross-section of the rotor body can have a V-shaped arrangement with radially inwardly directed tips. Furthermore, the invention can be further improved such that the outlet openings are positioned in the cross-section of the rotor body between the two V-shaped arrangements of the magnet recesses. The advantage of placing the cooling channels between the poles is that the space there has the least negative impact on the strength and electromagnetics of the electric machine.

[0027] In a variant of a similar preferred embodiment of the present invention, the plastic bodies of two circumferentially adjacent V-shaped arrangements can also be axially spaced apart from the magnet recesses on the first end face of the rotor body and form a substantially W-shaped profile in cross section, and the fluid guiding elements are formed on the radially outwardly directed tips of the W-shaped profile. This ensures that the function of the electric machine is not negatively affected. It is also desirable to bring the oil closer to the magnets because this is where the hot spots are located, and this can further improve cooling.

[0028] It is also advantageous to further develop the present invention such that the fluid guiding element is designed as a ramp having a ramp surface that is axially remote from the rotor body and radially outwardly inclined, whereby particularly effective cooling can be achieved.

[0029] According to another preferred embodiment of the subject matter of the present invention, in the case where a plurality of fluid guiding elements are formed on the first end face, their ramp surfaces can be formed differently from one another. This ensures that sufficient cooling of the winding heads can always be ensured depending on the rotational speed of the rotor.

[0030] The object of the present invention is also achieved by an electric machine comprising a hollow cylindrical stator and a rotor rotatably arranged in the stator, in which a stator winding is received, and the stator winding axially exits from both end faces of the stator to form winding heads in each case, the rotor being designed according to one of the preceding claims, and the fluid guiding element being configured such that a cooling fluid is guided to one of the winding heads when the electric machine is in operation. Description of the Drawings

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

[0032] In the drawings:

[0033] Figure 1 A motor vehicle having an electric drive train is shown schematically in a block diagram;

[0034] Figure 2 The electric machine is shown schematically in an axial cross section;

[0035] Figure 3 The electric machine is shown in an axial cross section;

[0036] Figure 4 The rotor is shown in a first three-dimensional axial cross section;

[0037] Figure 5 The rotor is shown in a second three-dimensional axial cross section. Detailed Description

[0038] The invention is explained by means of an electric machine 2 of a powertrain 3 for a motor vehicle 4, which electric machine is shown in the manner of an example from Figure 1 as shown.

[0039] The electric machine 2 is shown in an Figure 2 axial sectional view in

[0040] 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 received in the stator 19 and the stator winding axially exits from two end faces of the stator 19 to form winding heads 21 in each case. A rotor body 5 of the rotor 1 formed by a plurality of stacked rotor laminations 22 is connected in a rotationally fixed manner to a rotor shaft 23 and has a fluid guiding element 12 which is configured such that a cooling fluid 10 is guided to one of the winding heads 21 when the electric machine 2 is in operation. This is explained in more detail based on Figures 2 to 5 as follows.

[0041] The rotor 1 of the electric machine 2 has a rotor body 5 which has a plurality of magnet recesses 6 extending axially through the rotor body 5, and at least one rotor magnet 7 is received in each of the magnet recesses. The rotor magnets 7 are each fixed by means of a plastic body 8 extending in the magnet recess 6. The rotor body 5 also includes a plurality of cooling channels 9 extending axially through the rotor body 5, and the cooling fluid 10 can flow through the cooling channels. Each of the cooling channels 9 has an end face outlet opening 11 in the rotor body 5, and the cooling fluid 10 discharges from the cooling channels 9 through the outlet openings into the surroundings of the rotor when the rotor 1 is in operation.

[0042] One plastic body 8 projects axially out of the rotor body 5 through the fluid guiding element 12 and thus interacts with one of the outlet openings 11 such that the cooling fluid 10 leaving the outlet opening 11 when the rotor 1 is in operation is subjected to an axial force component by the fluid guiding element 12 of the plastic body 8.

[0043] The fluid guiding element 12 is arranged radially above the assigned outlet opening 11 and is positioned radially aligned with the assigned outlet opening 11.

[0044] The fluid guiding element 12 is assigned to all the outlet openings 11 on a first end face 13 of the rotor body 5 and is assigned to all the outlet openings 11 on a second end face 14 of the rotor body 5.

[0045] Two circumferentially adjacent magnet recesses 6 each have a V-shaped arrangement 15 with radially inwardly directed tips in the cross-section of the rotor body 5. The outlet opening 11 is positioned in the cross-section of the rotor body 5 between the two V-shaped arrangements 15 of the magnet recesses 6.

[0046] It can also be seen from Figure 4 that the plastic bodies 8 of the two circumferentially adjacent V-shaped arrangements 15 axially depart from the magnet recesses 6 on the first end face 13 of the rotor body 5 and form a substantially W-shaped profile in cross-section, and the fluid guiding element 12 is formed on the radially outwardly directed tip 16 of the W-shaped profile. The fluid guiding element 12 is designed as a ramp 17 having a ramp surface 18 that axially recedes from the rotor body 5 and is radially outwardly inclined. In the case where a plurality of fluid guiding elements 12 are formed on the first end face 13, their ramp surfaces 18 are designed to be different from each other.

[0047] The 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 are present in at least one embodiment of the invention. This does not exclude the presence of other features. Where the claims and the above description define a "first" feature and a "second" feature, such nomenclature is used to distinguish between two features of the same type and does not define a priority order.

[0048] List of reference numerals

[0049] 1 Rotor

[0050] 2 Electric motor

[0051] 3 Drivetrain

[0052] 4 Motor vehicle

[0053] 5 Rotor body

[0054] 6 Magnet recess

[0055] 7 Rotor magnet

[0056] 8 Plastic body

[0057] 9 Cooling channel

[0058] 10 Liquid cooling fluid

[0059] 11 Outlet opening

[0060] 12 Fluid guiding element

[0061] 13 End face

[0062] 14 End face

[0063] 15 Arrangement

[0064] 16 Tip

[0065] 17 Ramp

[0066] 18 Ramp surface

[0067] 19 Stator

[0068] 20 Stator winding

[0069] 21 Winding head

[0070] 22 Rotor lamination

[0071] 23 Rotor shaft

Claims

1. A rotor (1) of an electric machine (2), in particular of an electric machine for a drive train (3) of a motor vehicle (4), the rotor comprising a rotor body (5) having a plurality of magnet recesses (6) extending axially through the rotor body (5), at least one rotor magnet (7) being received in each of the magnet recesses, and the rotor magnets (7) each being fixed by means of a plastic body (8) extending in the magnet recesses (6), wherein, The rotor body (5) further includes a plurality of cooling channels (9) that axially extend through the rotor body (5) and through which a cooling fluid (10) can flow. Wherein, the cooling channels (9) have end face outlet openings (11) in the rotor body (5), and the cooling fluid (10) discharges from the cooling channels (9) through the outlet openings into the surroundings of the rotor when the rotor (1) is in operation. It is characterized in that, At least one plastic body (8) axially projects from the rotor body (5) through a fluid guiding element (12), and thus interacts with one of the outlet openings (11), such that the cooling fluid (10) leaving the outlet opening (11) when the rotor (1) is in operation is subjected to an axial force component due to the fluid guiding element (12) of the plastic body (8).

2. The rotor (1) according to claim 1, It is characterized in that, The fluid guiding element (12) is radially arranged above the outlet opening (11) assigned to the fluid guiding element.

3. The rotor (1) according to claim 1 or 2, It is characterized in that, The fluid guiding element (12) is positioned radially aligned with the outlet opening (11) assigned to the fluid guiding element.

4. The rotor (1) according to any one of the preceding claims, It is characterized in that, The fluid guiding element (12) is assigned to all the outlet openings (11) on the first end face (13) of the rotor body (5), and / or the fluid guiding element (12) is assigned to all the outlet openings (11) on the second end face (14) of the rotor body (5).

5. The rotor (1) according to any one of the preceding claims, It is characterized in that, Two circumferentially adjacent magnet recesses (6) each have a V-shaped arrangement structure (15) with radially inwardly pointing tips in the cross-section of the rotor body (5).

6. The rotor (1) according to claim 5, It is characterized in that, The outlet openings (11) are positioned between the two V-shaped arrangement structures (15) of the magnet grooves (6) in the cross-section of the rotor body (5).

7. The rotor (1) according to claim 5 or 6, It is characterized in that, The plastic bodies (8) of two circumferentially adjacent V-shaped arrangement structures (15) axially depart from the magnet recesses (6) on the first end face (13) of the rotor body (5) and form a substantially W-shaped profile in cross-section, wherein the fluid guiding elements (12) are formed on the radially outwardly pointing tips (16) of the W-shaped profile.

8. The rotor (1) according to any one of the preceding claims, It is characterized in that, The fluid guiding element (12) is designed as a ramp (17) having a ramp surface (18) that axially departs from the rotor body (5) and is radially outwardly inclined.

9. The rotor (1) according to claim 8, It is characterized in that, Of the plurality of fluid guiding elements (12) formed on the first end face (13), the ramp surfaces (18) of the fluid guiding elements are designed to be different from one another.

10. An electric machine (2), the electric machine 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), and the stator winding axially departs from both end faces of the stator (19) to form a winding head (21) in each case. It is characterized in that the rotor (1) is designed according to any one of the preceding claims, and the fluid guiding element (12) is configured such that the cooling fluid (10) is guided to one of the winding heads (21) when the electric machine (2) is in operation.

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