Electric machine, electric machine arrangement and method for assembling an electric machine

Abstract

An electric machine comprising a machine housing (2) and a rotor (5) received therein with a rotor carrier (6) and connecting means for connecting the rotor carrier (6) to a shaft, in particular a crankshaft (16) of an internal combustion engine, characterized in that the rotor carrier (6) is rotatably mounted on the machine housing (2) at one side, and the connecting means provided on the other side comprise at least one first ring disk (18, 28) detachably coupled to the rotor carrier (6), via which the rotor carrier (6) can be connected to the crankshaft (16).

Description

[0001] The invention relates to an electric machine comprising a machine housing and a rotor with a rotor carrier housed therein, as well as connecting means for connecting the rotor carrier to a shaft, in particular a crankshaft of an internal combustion engine. The invention further relates to an electric machine arrangement and a method for assembling an electric machine.

[0002] For example, in automotive applications, it is sometimes necessary to connect an electric machine to a shaft, such as the crankshaft of an internal combustion engine. This is particularly relevant in hybrid vehicles with series drive, where two coaxially or, because they are not connected or coupled, offset electric machines are arranged as a compact drive unit. One of these electric machines is connected to the crankshaft of the internal combustion engine and serves as a generator to produce the current required to operate the second electric machine, which then acts as a motor and is coupled to a gearbox. This gearbox, in turn, is coupled to a driven wheel, shaft, or axle. The current is either supplied directly to the driving machine or temporarily stored in an energy storage device and drawn from it as needed. Such an arrangement is, for example,This is described in WO 2019 / 101 264 A1. For example, in such a configuration, the rotor of the first electric machine must be directly connected to the crankshaft. This is achieved by shaping the rotor carrier so that it is essentially exposed at the entrance of the machine housing and can be bolted to the crankshaft via an inwardly directed radial flange. The assembly of the electric machine, or in the case of a series drive of the package comprising both electric machines and the gearbox, is carried out by the manufacturer during final assembly. It is necessary to remove the rotor of the first electric machine from the machine housing and mount it separately to the crankshaft, i.e., bolt it on, because the rotor, if installed, would not be accessible in a manner that allows for bolting.As part of the further assembly process, the electric motor is then attached, and the stator is slid over the rotor, which is mounted on the crankshaft side. This is a complex process requiring precise and careful assembly to prevent damage to the machine parts as they move relative to each other. Furthermore, exact positioning is crucial to ensure the stator is centered on the rotor. After this assembly, the manufacturer must then "calibrate" the electric motor. This is because the motor typically has a rotor position sensor that accurately and with high resolution detects the rotor's rotational position. This rotor position sensor comprises an encoder component, usually a ring-shaped disc, which is connected to the rotor carrier on which the rotor lamination stack sits, and a sensor fixed to the motor housing or similar structure that detects the encoder disc's position.Due to the removal and separate assembly of the rotor including the encoder ring disc, the position of the encoder ring disc relative to the sensor may be changed after final assembly compared to the initial assembly, which necessitates relearning.

[0003] From DE 11 2008 000 155 B4, an electric machine is known which can be read according to the preamble of claim 1. In this known electric machine, the connection to the crankshaft of an internal combustion engine and the rotary bearing of the rotor carrier are arranged on the same side of the electric machine.

[0004] A rotor carrier for a hybrid module is known from DE 10 2014 220 494 A1. Various drive trains for a motor vehicle with an internal combustion engine and at least one electric machine are known from DE 199 64 504 B4, DE 199 54 325 A1, DE 101 54 147 C1 and DE 10 2017 127 695 A1.

[0005] The invention is based on the problem of providing an improved electric machine, an electric machine arrangement, and a method for assembling such an electric machine.

[0006] According to the invention, this problem is solved by an electric machine according to claim 1. The rotor carrier is rotatably mounted on the machine housing at one side, and the connecting means provided at the other side comprise at least one first ring disk which can be detachably coupled to the rotor carrier and via which the rotor carrier can be connected to the crankshaft.

[0007] Furthermore, the rotor carrier is rotatably mounted on the machine housing via a suitable bearing arrangement, typically a rolling bearing. This bearing plane is located further inside the machine housing on one side of the rotor carrier, while the mounting plane of the rotor carrier to the crankshaft is located on the other side. To achieve this mounting, the corresponding connecting means are provided, which, according to the invention, comprise at least one first ring disk that can be detachably coupled to the rotor carrier, via which the rotor carrier can be connected to the crankshaft. This means that this connecting plane is a detachable connection, i.e., one that can be closed only when necessary, through which the rotor carrier is connected to the crankshaft. This allows, with particular advantage, the first step in assembly to connect this detachable ring disk to the crankshaft, typically by means of an axial screw connection of the ring disk to the crankshaft.The ring disc extends radially away from the crankshaft. During assembly, the electric motor is attached, including the rotor, which is fixed to and supported there. In the final assembly position, the rotor carrier is connected either directly or indirectly to the ring disc fixed on the crankshaft side. This can be easily done again using an axial screw connection, but from the opposite side compared to the crankshaft-side axial screw connection, because the ring disc fixed on the crankshaft side axially overlaps a corresponding mounting section associated with or connected to the rotor carrier, allowing for appropriate screw connections.

[0008] The electric machine, either as a standalone unit or as part of a compact machine arrangement comprising two electric machines, is significantly easier to assemble. This is because the rotor does not need to be removed and mounted separately, nor does the stator need to be repositioned relative to the rotor during final assembly. Furthermore, the manufacturer's calibration of the rotor position sensor is eliminated. This calibration can be performed after the electric machine is fully assembled, as the position remains constant once the stator-rotor arrangement is no longer modified.

[0009] Preferred embodiments are set out in the dependent claims.

[0010] Regarding the coupling of the rotor carrier with the first ring disk, which can be attached to the crankshaft, two variants are conceivable. According to a first alternative of the invention, the ring disk can be axially softer and radially stiffer, detachably arranged on the rotor carrier, and directly connected to the crankshaft. The ring disk itself is a disk that is somewhat axially softer but radially stiffer, and can also be referred to as a flexible disk or flexible disc. This ring disk is detachably arranged on the rotor carrier. During the assembly of the electric machine, the ring disk is first removed from the rotor carrier and fixed to the crankshaft. During the assembly of the electric machine, the rotor carrier is then moved axially against the ring disk with a corresponding connecting section, so that they lie flat against each other and are detachably fastened together, for example, by means of appropriate screw connections.In this design, the rotor carrier is directly connected to the crankshaft via this softer ring disc or flex plate.

[0011] In an alternative embodiment, a second ring disk, which is axially softer and radially stiffer, is fixedly connected to the rotor carrier. The first ring disk, which can be connected to the crankshaft, is detachably attached to this second ring disk. This embodiment of the invention thus employs a two-disc connection between the rotor carrier and the crankshaft. The second ring disk, which is fixed to the rotor carrier and therefore cannot be detached during assembly, is again an axially softer and radially stiffer ring disk—in other words, a flexible disc—which is itself detachably connected to the first ring disk. During assembly, this first ring disk can then be detached from the second ring disk and separately attached to the crankshaft, i.e., bolted axially.During the assembly of the electric machine, the second ring disc, which is fixed on the rotor carrier side, is now guided to the first ring disc, which is fixed on the crankshaft side, so that these two ring discs can now be screwed together axially from the other side.

[0012] Both variants include an axially softer, radially stiffer ring disc, i.e., a flexible plate. During operation, the crankshaft, in addition to its rotational movement, sometimes exhibits slight axial movement, which manifests as a wobble of the ring disc's mounting surface on the crankshaft. These movements must be compensated for by the coupling to the rotor. The softer ring disc or flexible plate offers a particular advantage in this regard, especially in combination with the slightly loose bearing that pivots the rotor carrier at the other end of the machine housing. This allows the assembly to compensate for or follow the movement of the crankshaft. The bearing clearance must be designed to allow the rotor to move slightly, corresponding to the axial movement of the crankshaft, without any contact between the rotor and stator.It is advantageous if the axial distance between the crankshaft or the connecting plane there and the rolling bearing of the rotor carrier is as large as possible, so that the axial movements in the bearing are low and the bearing clearance does not have to be unnecessarily large.

[0013] The removable first ring disc is advantageously connected to the rotor carrier via several bolted connections. For this purpose, the rotor carrier can have corresponding threaded holes or holes into which threaded bushings are inserted. If a two-disc solution is used, the fixed second ring disc is advantageously connected to the rotor carrier via several riveted connections, while the first ring disc is detachably connected to the second ring disc via several bolted connections. Here, too, the second ring disc, i.e., the flexible disc, can either have threaded holes or holes in which threaded bushings are provided. Simple holes for riveting are provided in both the rotor carrier and the second ring disc.

[0014] The rotor carrier is connected on both sides as described. On the side located inside the housing, it is fixed or supported by a rolling bearing, e.g., a single- or multi-row ball bearing or two angular contact ball bearings. On the other, open side, the connection to the crankshaft is provided. To form these two specific interfaces on the rotor carrier, the invention provides that the rotor carrier has a first cylindrical axial flange on which a rolling bearing supporting it to the machine housing is received. A radially outwardly extending first radial flange is connected to this first flange, followed by a second cylindrical axial flange on which a rotor lamination stack is mounted. A second radially outwardly extending second flange is connected to this second axial flange, to which the ring disk, either the removable or the fixed ring disk, is attached.A corresponding stepped geometry is therefore provided, forming the appropriate flanges to supply the bearing seats for the rolling bearing and the laminated core, as well as the connection interface to the ring disc. Alternatively, the ring disc can be attached to the first radial flange, meaning that in this embodiment no second radial flange is provided.

[0015] A sealing element can be arranged between the rolling bearing and the first radial flange, sealing a gap between the first axial flange and the machine housing. In this case, with two electric machines in series and a gearbox coupled to the second electric machine, the rolling bearing would be located in the gearbox's wet chamber and thus lubricated by it, while the sealing element seals this wet chamber from the engine chamber of the first electric machine. Alternatively, the rolling bearing could be located adjacent to the first radial flange, and the sealing element could be located adjacent to the rolling bearing, sealing the gap between the first axial flange and the machine housing. In this case, the rolling bearing would be located in the engine chamber of the first electric machine, i.e., in the dry chamber, which is in turn sealed from the gearbox's wet chamber by the sealing element.In this case, the rolling bearing would need to be grease-filled. The sealing element would be, for example, a radial shaft seal or similar.

[0016] Furthermore, a fixed rotor position sensor, particularly one mounted on the machine housing, can be provided, to which a encoder ring disk is assigned, arranged on the rotor carrier, particularly on the first radial flange. The rotor position sensor and the encoder disk together form the rotor position sensor assembly.

[0017] According to the invention, the aforementioned problem is further solved by an electrical machine arrangement according to claim 9, comprising a first electrical machine of the type described above, and a second electrical machine with a drive-coupled transmission. This machine arrangement is a series arrangement comprising two series electrical machines, the first of which is the machine designed according to the invention, which is arranged on the crankshaft of the internal combustion engine via the corresponding interface arrangement with the detachable ring disk. This electrical machine is driven mechanically by the combustion engine as a generator and supplies the current required for the operation of the second electrical machine, which can of course also be stored or buffered in a corresponding storage device.The second electric machine is connected to the transmission and, via the transmission, to a driven wheel, axle, or the like. This machine arrangement is a compact unit that can be assembled as a single piece and, due to the design of the first machine according to the invention, can be easily connected to the crankshaft of the internal combustion engine. The machine arrangement is therefore a drive unit for the powertrain of an electrically powered vehicle. Such a machine arrangement or drive unit can also be referred to as a two-electric-machine transmission or hybrid transmission and allows for a particularly compact design of a hybrid vehicle powertrain.

[0018] Furthermore, the aforementioned problem is solved according to the invention by a method for assembling an electric machine according to claim 10. In this method, according to the invention, the first ring disk is detached from the rotor carrier or the second ring disk is detached from the first ring disk and connected to the crankshaft, after which the electric machine is positioned and the rotor carrier is connected to the first ring disk or the first ring disk is connected to the second ring disk.

[0019] The invention is explained below with reference to exemplary embodiments and the drawings. The drawings are schematic representations and show: Fig. 1 a schematic representation of an electric machine of a first embodiment, in particular as part of a machine arrangement with another electric machine and gearbox, and Fig. 2 a schematic representation of an electric machine of a second embodiment, in particular as part of a machine arrangement with another electric machine and gearbox.

[0020] Fig. Figure 1 shows a partial view of an electric machine 1 according to the invention, comprising a machine housing 2 in which a stator-rotor arrangement 3 is provided. This includes a stator 4, which is fixedly arranged on the machine housing 2 and can be cooled by means of a cooling fluid circulating in a cooling channel 33. A rotor 5 is also provided, comprising a rotor carrier 6 and a rotor lamination stack 7 arranged on the rotor carrier 6. The rotor carrier 6 includes a first cylindrical axial flange 8, which serves as a bearing seat for a rolling bearing 9. The rotor carrier 6, and with it the entire rotor 5, is rotatably mounted on a corresponding bearing seat 10 of the machine housing 2 via this rolling bearing.The machine compartment, in which the rotor-stator assembly 3 is located, is sealed off from a wet compartment 13, in which a gearbox (not shown in detail) coupled to the second electric machine (also not shown in detail) is located, by means of a sealing element 11, which is arranged between the rolling bearing 9 and a first radial flange 12 adjoining the first axial flange 8. The electric machine 1 is thus part of a machine arrangement or drive unit for the drive train of an electrically powered vehicle and operates as a generator, while the second electric machine operates as an electric motor and drives the gearbox.

[0021] The radially extending first radial flange transitions into an axially extending second axial flange 14, on which the rotor lamination stack 7 is mounted. A second radial flange 15, projecting radially outwards, is then connected to this second axial flange. This radial flange 15 serves as an interface for connecting the rotor carrier 6 to a crankshaft 16 of an internal combustion engine. For this purpose, the second radial flange 15 has a plurality of threaded bores 17, which are arranged equidistantly around its circumference. A (first) annular disk 18 rests against the second radial flange 15 and has corresponding bores 19 through which the annular disk 18 is detachably fastened to the second radial flange 15. This is achieved by means of corresponding screw connections 20, which are screwed into the threaded bores 17. This therefore provides a detachable interface at which the ring disk 18 can be detached from the rotor carrier 6.

[0022] The ring disc 18 is a flexible plate or disc that exhibits some elasticity in the axial direction but is stiffer in the radial direction. This ring disc 18, which has a slight axial elasticity, can absorb any axial movements of the crankshaft 16 that may occur during operation. These axial movements can also be absorbed by any play in the rolling bearing 9, as can minor radial movements that may result from crankshaft movement or wobble of the ring disc 18.

[0023] The ring disc 18 is detachably screwed axially to the crankshaft 16 via corresponding screw connections 21, whereby a cover disc 22 can also be interposed. This means that the second detachable interface of the ring disc 18 is provided here.

[0024] During the assembly of the electric machine 1, or the machine assembly of which it may be a part, the ring disc 18 is detached from the rotor carrier 6 by loosening the screw connections 20 after the vehicle manufacturer has completed the electric machine 1 or the machine assembly. The ring disc 18 is then axially screwed to the crankshaft 16 via the screw connections 21. The electric machine 1 or the machine assembly is then positioned so that the second radial flange 15 rests against the ring disc 18 and the bores 19 align with the threaded bores 17. For this purpose, centering elements such as centering points may be provided on the rotor carrier 6, which engage in centering holes on the ring disc 18 when the parts are pushed together.The screw connections 20 are now tightened, which is easily possible since they are positioned opposite the screw connections 21 of the crankshaft mounting. Although axially oriented screw connections 20 are shown here, the screws can also be angled or, depending on the design of the rotor carrier, radially oriented, according to the installation space constraints for the internal combustion engine.

[0025] The electric machine 1 further comprises a rotor position sensor device 23, including a rotor position sensor 24, which is fixed in position, for example on the machine housing, and a sensor ring 25, which is located on the first radial flange 12. During the manufacture of the electric machine 1, all machine components, in particular the rotor-stator assembly 3 and the rotor position sensor devices 23, are assembled. This arrangement remains unchanged throughout the entire subsequent assembly process. This allows the rotor position sensor device 23 to be calibrated by the electric machine manufacturer. The vehicle manufacturer, who installs the electric machine, only needs to connect it to the crankshaft; no other additional work is required.

[0026] Fig. Figure 2 shows a second embodiment of an electrical machine 1 according to the invention, the basic structure of which is similar to that shown in Figure 2. Fig. 1 is. Only the rotor carrier 6 and its connection to the crankshaft 16 are designed somewhat differently here.

[0027] The rotor carrier 6 has the first axial flange 8, the first radial flange 12, and the second axial flange 14. In the example shown, a second ring disk 26 is permanently attached to this second axial flange by means of corresponding rivet connections 27, which extend through corresponding bores 28 and 29 in the radial flange 12 and in the second ring disk 26. This second ring disk 26 is designed as a flexible disk, meaning it is slightly softer axially than radially, so that any axial crankshaft movements can be easily absorbed.

[0028] A first ring disk 28 serves to connect the rotor carrier 6 to the crankshaft 16. This ring disk is axially screwed to the crankshaft 16 via screw connections 34 and axially connected to the second ring disk 26 via screw connections 30. The second ring disk 26 has corresponding threaded bores 31 into which the screw connections 30 are inserted. This rivet plane is located radially further outward than the screw connection plane of the ring disk 26 with the radial flange 12.

[0029] During assembly, the first ring disc 28 is separated from the second ring disc 26, which, as described, is permanently connected to the rotor carrier 6 during assembly, by loosening the screw connections 30. The first ring disc 28 is then axially screwed to the crankshaft 16 via the screw connections 34 as a separate component. The electric motor 1 is then positioned so that the radial outer edge of the second ring disc 26 overlaps with the first ring disc 28, and the corresponding bores 32 overlap with the respective threaded bores 31 of the second ring disc 26. Finally, the screw connections 30 are tightened, again axially from the opposite side compared to the screw connections 29.

[0030] This design also allows for very simple assembly; in particular, as explained, the rotor 5 itself can no longer be disassembled.

Claims

[1] Electric machine comprising a machine housing (2) and a rotor (5) received therein with a rotor carrier (6) and connecting means for connecting the rotor carrier (6) to a shaft, in particular a crankshaft (16) of an internal combustion engine, characterized by , that the rotor carrier (6) is rotatably mounted on the machine housing (2) on one side, and the connecting means provided on the other side comprise at least one first ring disk (18, 28) which can be detachably coupled to the rotor carrier (6) and via which the rotor carrier (6) can be connected to the crankshaft (16). [2] Electric machine according to claim 1, characterized by , that the ring disc (18) is axially softer and radially stiffer and is detachably arranged on the rotor carrier (6) and can be directly connected to the crankshaft (16). [3] Electric machine according to claim 1, characterized by, that an axially softer, radially stiffer second ring disk (26) is firmly connected to the rotor carrier (6), on which the first ring disk (28) is detachably arranged, which can be connected to the crankshaft (16). [4] Electric machine according to claim 2 or 3, characterized by , that the detachable first ring disc (18) is detachably fastened to the rotor carrier (6) via several screw connections (20), or that the fixed second ring disc (26) is firmly connected to the rotor carrier (6) via several rivet connections (27) and the first ring disc (28) is detachably connected to the second ring disc (26) via several screw connections (30). [5] Electric machine according to any of the preceding claims, characterized by, that the rotor carrier (6) has a first cylindrical axial flange (8) on which a rolling bearing (9) supporting it to the machine housing (2) is received, to which a radially outwardly extending first radial flange (12) is connected, to which a cylindrical second axial flange (14) is connected, on which a rotor lamination stack (7) is seated, wherein either a second radially outwardly extending second radial flange (15) is connected to the second axial flange, to which the ring disk (26) is attached, or wherein the ring disk (26) is attached to the first radial flange. [6] Electric machine according to claim 5, characterized by, that a sealing element (11) is arranged between the rolling bearing (9) and the first radial flange (12), which seals a gap between the first axial flange (8) and the machine housing (2), or that the rolling bearing (9) is arranged adjacent to the first radial flange (12) and the sealing element (11) is arranged adjacent to the rolling bearing (9) and seals the gap between the first axial flange (8) and the machine housing (2). [7] Electric machine according to any of the preceding claims, characterized by , that a position-fixed rotor position sensor (24) is provided, in particular arranged on the machine housing (2), to which a sensor ring disk (25) arranged on the rotor carrier (6) is assigned. [8] Electric machine according to claim 7, characterized by , that the encoder ring disc (25) is arranged on the first radial flange (12). [9] Electrical machine arrangement comprising a first electrical machine (1) according to one of the preceding claims, and a second electrical machine with a drive coupled to the latter. [10] Method for mounting an electric machine (1) according to one of claims 1 to 8 or the first electric machine (1) of an electric machine arrangement according to claim 9 to a crankshaft (16) of an internal combustion engine, characterized by , that the first ring disk (18, 28) is detached from the rotor carrier (6) or from the second ring disk (26) and connected to the crankshaft (16), after which the electric machine (1) is positioned and the rotor carrier (6) is connected to the first ring disk (18) or the second ring disk (26) is connected to the first ring disk (28).

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