Rotor, method for manufacturing a rotor, and an electric machine

Abstract

The invention relates to a rotor (1) for an electric machine (2), comprising a cylindrical rotor body (4) formed from a laminated rotor core (3) and having a plurality of pockets (5) for receiving rotor magnets (6), at least a first group (7) of the pockets (5) extending substantially tangentially, the rotor magnets (6) being fixed in the pockets (5) of the first group (7) by means of injected plastic (8), the pockets (5) of the first group (7) having, radially above the pockets (5) of the first group (7), in each case a radially outer contour (9) which substantially corresponds to the radially outer arcuate contour of the cylindrical rotor body (4), the plastic (8) being provided in each case between the radially outer contour (9) of one of the pockets (5) of the first group (7) and the rotor magnets (6) fixed in the pockets (5).

Description

Technical Field

[0001] The present invention relates to a rotor of an electromechanical machine, comprising a cylindrical rotor body formed from a laminated rotor core having a plurality of pockets for receiving rotor magnets, at least a first group of pockets extending substantially tangentially, and rotor magnets being fixed within the pockets of the first group by injection plastic. The present invention further relates to a method of manufacturing the rotor and an electromechanical machine.

Background Art

[0002] In order to form an alternative to internal combustion engines that require fossil fuels, electric motors are increasingly being used for the purpose of driving motor vehicles. Considerable efforts have already been made to improve the suitability of electric drive systems for daily use and to provide users with a comfortable driving experience to which they are accustomed.

[0003] A detailed description of the electric drive unit is given in the article "Hochintegrativ und Flexibel Elektrische Antriebseinheit fuer E-Fahrzeuge [Highly Integrative and Flexible Electric Drive Unit for E-Vehicles]" by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, published on pages 360 - 365 of Volume 113 (May 2011) of the German automotive magazine ATZ. This article describes a drive unit for a vehicle axle that includes an electric motor arranged concentrically and coaxially with a bevel gear differential, and a shiftable two-speed planetary gear set arranged in the drive train between the electric motor and the bevel gear differential and also arranged coaxially with the electric motor and the bevel gear differential or a spur gear differential. This drive unit is very compact, and the shiftable two-speed planetary gear set enables a good compromise between climbing ability, acceleration, and energy consumption. Such a drive unit is also called an E-axle or an electric drive train.

[0004] In addition to purely electrically operated drive trains, hybrid drive trains are also known. The drive train of such a hybrid vehicle usually includes a combination of an internal combustion engine and an electric motor, enabling, for example, a pure electric driving mode in urban areas while allowing for both sufficient range and availability, especially during suburban driving. Furthermore, in certain driving situations, it is also possible to drive the internal combustion engine and the electric motor simultaneously.

[0005] During operation, an electric machine is subject to losses due to magnetic reversal and eddy currents, which are grouped together as iron losses and reduce the efficiency of the machine. When using an electric machine in a mobile application, especially in the drive train of a hybrid vehicle or a fully electric vehicle, a low efficiency of the electric machine can lead to a shorter vehicle range or an increased need for battery capacity.

[0006] As an example of such an electromechanical machine, there is a "permanent magnet excitation type" synchronous machine that can be used in the drive train of a hybrid vehicle or a fully electric vehicle. Since this has a higher output density compared to other types of machines, it is suitable for use in the field of electromobility where installation space is often a limiting factor. The excitation field of the machine is usually generated by permanent magnets arranged on the rotor of the machine. In a permanent magnet excitation type synchronous machine, it is possible to omit the slip ring contacts required in an electrically excited synchronous machine in order to supply power to the excitation coil arranged on the rotor.

[0007] When developing an electromechanical machine for an e-axle or a hybrid module, there is a continuous need to increase its output density, and forming the air gap between the rotor and the stator as accurately as possible becomes an important variable that determines performance. The noise generated from the drive device and its weight play particularly important roles, especially in the case of hybrid or fully electric drive concepts. However, these two requirements are mutually contradictory, and usually, the higher the sound insulation of the drive, the greater the weight increase. High electromagnetic excitation, which can also lead to the acoustic vibration of the structural parts of the electromechanical machine or the drive train, may occur during the operation of the electromechanical machine for a hybrid or fully electric drive train for system-related reasons. This may be audible inside the vehicle and is usually recognized as annoying. Summary of the Invention Problems to be Solved by the Invention

[0008] Therefore, one object of the present invention is to provide a rotor of an electromechanical machine that can provide improved output density and low noise during operation. A further object of the present invention is to provide an improved method for manufacturing the rotor. Also, the ultimate object of the present invention is to provide an improved electromechanical machine. Means for Solving the Problems

[0009] This object is achieved by a rotor for an electric machine, comprising a cylindrical rotor body formed from a laminated rotor core having a plurality of pockets for receiving rotor magnets, wherein at least a first group of pockets extends substantially tangentially, and wherein the rotor magnets are fixed in the pockets of the first group by injection plastic, and wherein the pockets of the first group have, in any case, a radially outer contour that substantially corresponds to the radially outer arcuate contour of the cylindrical rotor body above the first group of pockets in the radial direction, and wherein the plastic is provided, in any case, between the radially outer contour of one of the pockets of the first group and the rotor magnet fixed in the pocket.

[0010] Thereby, the advantage is obtained that the radially outer side of the rotor has a very accurate roundness, and a corresponding accurate and homogeneous air gap is provided between the rotor and the stator. In this way, undesirable vibrations and the associated noise can be reduced or completely avoided.

[0011] The individual elements of the claimed subject matter of the invention will first be explained in the order in which they are named in the claims, and thereafter preferred embodiments of the subject matter of the invention will be described.

[0012] An electric machine is used to convert electrical energy into mechanical energy and / or to convert mechanical energy into electrical energy, and generally comprises a stationary part, generally called a stator or stationary armature, and a rotor or moving armature, which is movably arranged relative to the stationary part.

[0013] The electric machine can be configured in particular as a rotating machine. The electric machine can be configured as a radial flux machine or an axial flux machine. The radial flux machine is characterized in that the magnetic field lines extend radially in the air gap formed between the rotor and the stator, and in the case of the axial flux machine, the magnetic field lines extend axially in the air gap formed between the rotor and the stator. In the context of the present invention, it is particularly preferred that the electric machine is configured as a radial flow machine.

[0014] The gap between the rotor and the stator is called an air gap. In a radial flux machine, this gap is an annular gap having a radial width corresponding to the distance between the rotor body and the stator body.

[0015] The electric machine can preferably have a motor housing. The motor housing can enclose the electric machine. The motor housing can further accommodate a control unit, in particular control and power electronics. The motor housing can further be part of the cooling system of the electric machine, and can be configured such that a cooling fluid can be supplied to the electric machine through the motor housing and / or heat can be dissipated to the outside through the housing surface. Furthermore, the motor housing protects the electric machine and any potential electronic devices from external influences.

[0016] The motor housing can in particular be formed from a metallic material. Advantageously, the motor housing can be formed from a cast metallic material such as grey cast iron or cast steel. In principle, it is also conceivable to form all or part of the motor housing from plastic.

[0017] The rotor according to the present invention can include a rotor body. The rotor body for the purposes of the present invention is understood to mean a rotor without a rotor shaft. Thus, the rotor body is in particular composed of a laminated rotor core, magnetic elements introduced into the pockets of the laminated rotor core or circumferentially fixed to the laminated rotor core, and axial cover parts present for closing the pockets.

[0018] Permanent magnets introduced into the pockets of the laminated rotor core are understood as rotor magnets. A single large rotor magnet configured as a bar magnet or a plurality of small permanent magnet elements can be provided in each pocket.

[0019] The laminated rotor core generally means a plurality of laminated individual laminates or rotor laminates made from electrical metal sheets and packaged by being stacked on top of each other to form a stack or "laminated rotor core". The individual laminates can be held in the laminated core by adhesion, welding, or screwing.

[0020] The rotor laminate can have one or more notches, which can also be called recesses or openings, and the individual notches of the individual rotor laminates form pockets provided axially in the rotor laminate stack for receiving magnetic elements.

[0021] The rotor preferably includes a rotor shaft and one or more rotor bodies non-rotatably arranged on the rotor shaft. The rotor shaft can be hollow, which on the one hand results in weight reduction while enabling the supply of lubricating oil or cooling water to the rotor body.

[0022] The electromechanical device can further have a control unit. The control unit used in the present invention functions in particular in the open-loop electronic control and / or closed-loop electronic control of one or more technical systems of a motor vehicle.

[0023] The control unit in particular has a wired or wireless signal input for receiving electrical signals, such as sensor signals for example. Furthermore, the control unit preferably in particular has a wired or wireless signal output for transmitting electrical signals to, for example, an axel drive train that operates electrically, or an electric actuator of a motor vehicle, or an element that consumes electricity.

[0024] Within the control unit, an open-loop control operation and / or a closed-loop control operation can be carried out. It is highly particularly preferred that the control unit comprises hardware configured to execute software. The control unit preferably comprises at least one electronic processor for executing a program sequence defined in software.

[0025] The control unit can further have one or more electronic memories that can store and read out again the data contained in the signals transmitted to the control unit. Furthermore, the control unit can have one or more electronic memories that can store data in a changeable and / or unchangeable manner.

[0026] The control unit can in particular comprise a plurality of control devices that are spatially separated from each other within a motor vehicle. The control devices, also called electronic control units (ECUs) or electronic control modules (ECMs), preferably in particular have an electronic microcontroller for executing computational operations for processing data, using software. The control devices can preferably be interconnected with each other such that wired and / or wireless data exchange between the control devices is possible. In particular, it is also possible to interconnect the control devices with each other via a bus system present in the motor vehicle, such as, for example, a CAN bus or a LIN bus.

[0027] Very particularly preferably, the control unit has at least one processor and at least one memory, in particular containing computer program code, the memory and the computer program code being configured such that the processor causes the control unit to execute the computer program code.

[0028] The control unit can particularly preferably comprise a power electronics module for energizing the stator or the rotor. The power electronics module is preferably a combination of different components that provides open-loop or closed-loop control of the current to the electromechanical machine, and preferably includes peripheral components necessary for this purpose, such as a cooling element or a power supply unit. In particular, the power electronics module includes one or more power electronics components configured to provide open-loop or closed-loop control of the current. These are particularly preferably one or more power switches, such as power transistors. The power electronics unit particularly preferably has three or more, particularly preferably four or more, separate phases or current paths, each having at least one separate power electronics component. The power electronics unit is preferably configured to provide open-loop or closed-loop control of the power for each phase having a peak power, preferably a continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W.

[0029] This electromechanical machine is particularly intended for use in the drive train of a hybrid vehicle or a fully electric vehicle. In particular, this electromechanical machine has dimensions such that vehicle speeds above 50 km / h, preferably above 80 km / h, particularly above 100 km / h can be achieved. Very particularly preferably, the electric motor has an output above 30 kW, preferably above 50 kW, particularly above 70 kW. Furthermore, it is preferable that this electromechanical machine provides speeds above 5,000 rpm, particularly preferably above 10,000 rpm, very particularly preferably above 12,500 rpm.

[0030] The electric machine can be mounted in an electric axle drivetrain. The electric axle drivetrain of a motor vehicle comprises an electric machine and a transmission, which form a structural unit. In particular, the electric machine and the transmission can be arranged in a common drivetrain housing. Alternatively, it is of course possible for the electric machine to have a motor housing and the transmission to have a transmission housing, in which case the structural unit can be formed by fixing the transmission to the electric machine. This structural unit is sometimes called an E-axle.

[0031] The electric machine may be intended in particular for use in a hybrid module, in which the structural and functional elements of a hybridized drivetrain can be spatially and / or structurally combined and preconfigured in such a way that the hybrid module can be integrated into the drivetrain of a motor vehicle in a particularly simple manner. In particular, an electric motor and a clutch system, in particular with a disconnect-type clutch for engaging and / or decoupling the electric motor from the drivetrain, can be present in the hybrid module.

[0032] According to an advantageous embodiment of the invention, the radially inner contour of the pocket can have a substantially tangential linear extension, which allows advantageous magnetic excitation to occur.

[0033] According to a further preferred development of the invention, the first group of pockets can have a rectangular basic shape. Furthermore, according to an equally advantageous embodiment of the invention, the rotor magnets can be configured as bar magnets with a substantially rectangular cross-sectional profile, so that they can be inserted axially into the rectangular pockets in an easily assembled manner.

[0034] According to a further particularly preferred embodiment of the invention, the pockets of the first group can be arranged on a pitch circle corresponding to 0.8 to 0.97 times the diameter of the cylindrical rotor body, which also proves to be advantageous for magnetic excitation.

[0035] Furthermore, the invention can be further developed so that the pockets of the first group each have a plastic injection zone at their tangential ends, which facilitates fixing the rotor magnets in the pockets in a correspondingly defined manner.

[0036] The object of the present invention is also to provide a method for manufacturing a rotor for an electric machine comprising a substantially cylindrical rotor body formed from a laminated rotor core having a plurality of pockets for receiving rotor magnets, at least a first group of pockets being arranged substantially tangentially, the method comprising the following steps: providing a rotor body, the rotor body having an outer contour portion radially above the first group of pockets, the contour portion having a contour that deviates from the arcuate contour of the cylindrical rotor body; Inserting rotor magnets into the first group of pockets; injecting plastic into the first group of pockets such that the rotor magnets are fixed within the first group of pockets; The injection pressure and temperature of the plastic during injection, as well as the radially outer contour and outer contour portion of the first group of pockets before the plastic is injected, This is achieved by a method in which the injected plastic is selected to have a contour that substantially corresponds to the arcuate contour of the cylindrical rotor body due to the offset of material between the outer contour of the pocket and the outer contour portion.

[0037] This ensures that the radially outer flank of the rotor has very accurate roundness, with as few and small deviations from circularity as possible.

[0038] It may also be advantageous to further develop the invention so that, before the plastic is injected, the outer contour portions are each straight lines extending substantially parallel to the tangential extension of the pocket, which has proven to be particularly advantageous from a production engineering point of view.

[0039] The plastic can be preferably introduced into the pockets of the rotor body using a transfer molding process. The plastic is preferably injected into the pockets of the rotor body at a pressure of 10 to 150 bar, in particular 20 to 100 bar. When injected into the pockets of the rotor body, the plastic particularly preferably has a temperature of 120 to 250°C, preferably 140 to 200°C. The flow rate of the plastic when injected into the pockets is preferably 0.5 to 20 mm / s, more preferably 1 to 15 mm / s.

[0040] The object of the invention is also achieved by an electric metal sheet for forming a laminated rotor core of a rotor body of an electric machine rotor, the electric metal sheet having a plurality of pockets for receiving rotor magnets, at least a first group of pockets extending substantially tangentially, the electric metal sheet having an outer contour portion radially above the first group of pockets, the outer contour portion having a contour that deviates from the arcuate contour of the circular outer contour of the electric metal sheet and is offset radially inward. Such an electric metal sheet is particularly intended for use in a method according to claim 7.

[0041] The object of the invention is also achieved by an electric machine, in particular an electric machine for the drive train of a hybrid or fully electric vehicle, comprising a rotor according to one of claims 1 to 6.

[0042] Without limiting the general concept of the invention, the invention will now be explained in more detail with reference to the drawings. [Brief description of the drawings]

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0044] FIG. 1 shows an electric machine 2, particularly for a drive train of a hybrid vehicle or a fully electric vehicle, comprising a rotor 1 rotatably mounted relative to a stator 15. The electric machine 2 is configured as a radial flux machine, the stator 15 has a structure like a cylindrical ring, and the rotor 1 is coaxially arranged within the stator 15. The rotor 1 further has a rotor shaft 16 on which a rotor body 4 is arranged.

[0045] FIG. 2 shows the assembly recognized from FIG. 1 in a cross-sectional view. The rotor comprises a cylindrical rotor body 4 formed from a laminated rotor core 3 having a plurality of pockets 5 for receiving rotor magnets 6. A first group 7 of pockets 5 of substantially the same shape arranged equidistantly on the circumference of the rotor 1 extends substantially in a tangential direction. The pockets 5 of the first group 7 have a basic rectangular shape. The rotor magnets 6 are each configured as bar magnets having a substantially rectangular cross-sectional contour 10.

[0046] The rotor magnets 6 can be inserted axially into the pockets 5 with play, but are fixed in the pockets 5 of the first group 7 by the injected plastic 8. The pockets 5 of the first group 7 have a radially outer contour 9 which, as is readily apparent from the detailed view in FIG. 4 , essentially corresponds to the radially outer arcuate contour of the cylindrical rotor body 4 in each case radially above the pockets 5 of the first group 7. In contrast to the radially outer contour 9, the radially inner contour 12 of the pockets 5 extends substantially tangentially and linearly. Each pocket 5 of the first group 7 has an injection zone 13 of the plastic 8 at its tangential end.

[0047] In the space formed by the play between the rotor magnets 6 and the pockets 5, the injected plastic 8 is located between the radially outer contour 9 and the rotor magnets 6. In other words, the plastic 8 is present between the radially outer contour 9 of one of the pockets 5 of the first group 7 and the rotor magnet 6 fixed in the pocket 5, so that the corresponding rotor magnet 6 is also completely fixed in the pocket 5 without any radial play. The rotor magnet 6 is also held by the injected plastic 8 against the radially inner contour 12 of the pocket 5.

[0048] In the embodiment of rotor 1 shown in Figures 2-4, a second, V-shaped group 14 of pockets 5 with a rotor magnet 6 is located radially below each pocket 5 of the first group 7. As is readily apparent from Figures 2-4, the V-shaped group 14 of pockets 5 is formed by two rectangular pockets 5 that are spaced apart from each other and have a V-shaped relationship to each other. The apexes of the V-shaped arrangement of the pockets 5 of group 14 point radially inward. Thus, the number of pockets 5 in group 14 is twice the number of pockets 5 in the first group 7.

[0049] FIG. 2 further shows that the pockets 5 of the first group 7 are arranged on a pitch circle 11 which corresponds to 0.8 to 0.97 times the diameter of the cylindrical rotor body 4 .

[0050] As can be seen from FIG. 2, a method for manufacturing the rotor 1 of the electric machine 2 will now be described in detail with reference to FIGS.

[0051] First, a rotor body 4 is provided, which in each case has outer contour portions 20 radially above the pockets 5 of the first group 7, which, as is readily apparent from FIG. 3, have a contour that deviates from the arcuate contour 21 of the cylindrical rotor body 4. Before the plastic 8 is injected, these outer contour portions 20 are each formed as a straight line extending substantially parallel to the tangential extension of the pockets 5. The contour portions 20 can be formed, for example, by punching or milling.

[0052] The rotor magnets 6 can then be inserted with some play into the pockets 5 of the first group 7. Then, in this manufacturing state, plastic 8 is injected into the pockets 5 of the first group 7 via the injection zone 13, and the rotor magnets 6 are fixed in the pockets 5 of the first group 7.

[0053] The injection pressure and temperature of the plastic 8 during injection, as well as the radially outer contour 9 and outer contour portion 20 of the pockets 5 of the first group 7 before the plastic 8 is injected, are selected so that, once the plastic 8 is injected, the outer contour portion 20 has a contour with a material offset between the outer contour 9 of the pockets 5 and the outer contour portion 20 that substantially corresponds to the arcuate contour 21 of the cylindrical rotor body 4. In other words, the linear contour portion 20 is displaced radially outward by the injection pressure of the plastic 8 into the pockets 5, causing a bulge in the contour portion 20 that corresponds to the arcuate contour 21 of the rotor body 4, as is readily apparent in FIG.

[0054] In this case, the plastic 8 is injected into the pockets 5 of the first group 7 of the rotor body 4 by a transfer molding process at an injection pressure of 20 to 100 bar and a temperature of the plastic 8 during injection of 140 to 200 °C. The flow rate of the plastic 8 during injection into the pockets 5 is preferably 1 to 15 mm / s.

[0055] FIG. 3 shows a top view of the electrical metal sheet of the laminated rotor core 3 of the rotor body 4 used in the manufacturing method described above. The electrical metal sheet has a plurality of pockets 5 for receiving the rotor magnets 6, at least the pockets 5 of the first group 7 extend substantially in the tangential direction, the electrical metal sheet has an outer contour portion 20 radially above the pockets 5 of the first group 7, and this contour portion deviates from the arc-shaped contour 21 of the circular outer contour of the electrical metal sheet and has a contour offset radially inward. In the illustrated exemplary embodiment, the contour deviating from the circular outer contour of the electrical metal sheet is configured as a straight tangential portion extending parallel to the inner contour 12 of the pocket 5. In the illustrated exemplary embodiment, the straight tangential portion extends completely circumferentially over the entire longitudinal range of the pocket 5.

[0056] The present invention is not limited to the embodiments shown in the figures. Therefore, the above description does not limit the present invention, but rather is to be regarded as exemplary. It should be understood that the following claims are meant to mean that the described features exist in at least one embodiment of the present invention. This does not exclude the existence of further features. In the claims and the above description, when “first” features and “second” features are defined, this designation serves to distinguish two features of the same kind without defining a priority order.

Explanation of reference numerals

[0057] 1 Rotor 2 Electromechanical 3 Laminated rotor core 4 Rotor body 5 Pocket 6 rotor magnet 7 Groups 8. Plastic 9. Contour 10 Cross-sectional profile 11 Pitch circle 12 Contour 13 Launch Zone 14 groups 15 Stator 16 rotor shaft 20 Outline 21 Contour

Claims

1. A method for manufacturing a rotor (1) for an electromechanical machine (2), comprising a substantially cylindrical rotor body (4) formed from a laminated rotor core (3) having a plurality of pockets (5) for receiving rotor magnets (6), wherein a first group (7) consists of pockets (5) that extend substantially tangentially among the plurality of pockets (5), a step of providing the rotor body (4), wherein the rotor body (4) has an outer contour portion (20) radially above the pockets (5) of the first group (7), and the outer contour portion (20) has a contour deviating from the arcuate contour (21) of the cylindrical rotor body (4), a step of inserting the rotor magnets (6) into the pockets (5) of the first group (7), a step of injecting plastic (8) into the pockets (5) of the first group (7) so that the rotor magnets (6) are fixed within the pockets (5) of the first group (7), including, the injection pressure and temperature of the plastic (8) during injection, and the contour (9) radially outside the pockets (5) of the first group (7) and the outer contour portion (20) before the plastic (8) is injected are, selected such that when the plastic (8) is injected, the outer contour portion (20) has a contour substantially corresponding to the arcuate contour (21) of the cylindrical rotor body (4) due to the offset of the material between the outer contour (9) of the pocket (5) and the outer contour portion (20).

2. The method according to claim 1, wherein before the plastic (8) is injected, each of the outer contour portions (20) is a straight line extending substantially parallel to the tangential extension of the pocket (5).

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