Electric machine for motor vehicle, rotor for electric machine, and motor vehicle

Abstract

The invention relates to an electric machine (2), in particular a separately excited synchronous machine, for a motor vehicle (1), comprising a stator (4) and a rotor (3) which is mounted so as to be rotatable relative to the stator (4) and which has rotor windings (15) for generating a rotor magnetic field, an active rectifier (19) being provided on the rotor (3), an active rectifier (19) electrically connects a power source present on the rotor (3) to the rotor winding (15), by means of which an alternating voltage provided by the power source can be converted into a direct voltage which can be used during the generation of a rotor magnetic field by means of the rotor winding (15), the rectifier (19) being arranged on or in a cooling section (27) of the rotor (3), the cooling section forms a heat sink, and a cooling fluid can flow through the cooling section.

Description

Technical Field

[0001] The present invention relates to an electric motor for motor vehicles, particularly a separately excited synchronous motor, the motor comprising a stator and a rotor supported in a manner rotatable relative to the stator, the rotor having rotor windings for generating a rotor magnetic field. Background Technology

[0002] Electric motors are commonly used as power motors in motor vehicles, which can be pure electric vehicles or hybrid electric vehicles. An electric motor includes a stator and a rotor supported in a manner rotatable relative to the stator. Windings composed of conductor wires are provided in both the stator and rotor, and, if necessary, permanent magnets are also provided. Electromagnetic interaction between the magnetic fields generated by the windings and, if necessary, the permanent magnets results in driving torque or braking torque. Especially in electric motors used as power motors, the power transmission is typically very high, necessitating active cooling of the components involved. Examples related to cooling in electric motors are known from the prior art, for example from publications DE 10 2010032 827A1 and US2015 / 0280 525A1.

[0003] In electric motors, such as separately excited synchronous motors, permanent magnets are typically omitted from the rotor side. Instead, windings are provided on the rotor side to generate the required rotor magnetic field, thereby providing additional degrees of freedom in the adjustment and design of the motor. However, the rotor windings on the rotor side necessitate energizing them. For this purpose, power is transferred from the stationary part of the motor (which can also be understood as the stator) to the rotor, for example via slip ring contact or non-contact via an inductive transmission component. When using an inductive transmission component in this context, an AC voltage is generated on the rotor side, which must be converted to the DC voltage required to generate the rotor magnetic field by means of the rotor windings. Such a system is known from DE 10 2021213 736 A1, in which cooling is also performed on the passive rectifier provided on the rotor side in this context. Summary of the Invention

[0004] The purpose of this invention is to provide an improved design solution in conjunction with cooling of the motor rotor.

[0005] According to the present invention, the objective is achieved by a motor of the type described at the beginning in the following manner: an active rectifier is provided on the rotor side, which electrically connects the power supply present on the rotor side to the rotor windings, and the active rectifier can convert the AC voltage provided by the power supply into a DC voltage, which can be used in the process of generating a rotor magnetic field through the rotor windings, wherein the rectifier is arranged on or in the cooling section of the rotor, the cooling section forming a heat sink, and the cooling section can be traversed by cooling fluid.

[0006] This invention is specifically based on the concept of an active rectifier on the rotor, which generates more heat and must be cooled, particularly compared to a passive rectifier. Due to the heat generated, the rectifier is often a component that limits the maximum power output of a motor. To improve this, the active rectifier is arranged on a heat sink, enabling or enhancing thermal coupling between the heat sink and the rectifier to dissipate heat from the rectifier. For this purpose, in addition to providing a heat-conducting medium for fixing the rectifier, the rectifier preferably has direct contact, preferably touch contact, with the heat sink. A cavity for guiding the cooling fluid, particularly a cooling channel, is preferably located directly below the rectifier. The cooling fluid is preferably a cooling liquid, such as water or oil.

[0007] The rotor is rotatably supported relative to the stator, which typically has stator windings to generate a stator magnetic field. For this purpose, the rotor shaft can be supported by appropriate bearings, such as ball bearings or rolling bearings. The rotor and stator are preferably arranged inside the motor housing, wherein the stator is preferably positioned fixed relative to the housing.

[0008] The rotor winding and / or stator winding has at least one conductive wire, which is wound, for example, around rotor teeth or stator teeth. The winding serves as an excitation coil, which generates a magnetic field, i.e., a rotor magnetic field or a stator magnetic field, when energized.

[0009] An active rectifier can be understood in particular as an electrical component comprising multiple controllable semiconductor elements, especially transistors. Therefore, an active rectifier, or at least a portion of its semiconductor elements, can be controlled by a control signal, which can be used to control the operation of the rectifier, for example, to implement the rectifier and (if necessary) an inverter. In contrast, a passive rectifier typically only has semiconductor diodes, so regardless of the control signal, the AC voltage applied to the rectifier input is always converted into a DC voltage appearing at the rectifier output.

[0010] The following describes the definitions of relevant spatial directions in the motor according to the present invention. That is, the rotor is rotatably supported about a rotational axis extending along the longitudinal direction of the motor. The radial direction extends perpendicular to the longitudinal direction. The circumferential direction is perpendicular to the radial direction. In other words, a point rotating about the rotational axis moves along the circumferential direction. The longitudinal, radial, and circumferential directions of the rotor correspond to the longitudinal, radial, and circumferential directions of the motor.

[0011] The electric motor according to the invention preferably includes an induction rotary transformer comprising at least one rotor-side excitation coil present on the rotor and forming a power source, and at least one stator-side excitation coil present on the stator, wherein electrical energy can be induced from the stator-side excitation coil to the rotor-side excitation coil. The induction rotary transformer enables non-contact and, consequently, low-loss or lossless power transfer from the stator or stationary section to the rotor. During rotor rotation, the rotor-side and stator-side excitation coils move alternately, wherein the magnetic field generated on the stator-side excitation coil induces a voltage on the rotor-side excitation coil via electromagnetic induction. Therefore, the rotor-side excitation coil serves as a power source, in which the generated voltage exists as an alternating current (AC) voltage. This AC voltage is converted to a direct current (DC) voltage required to operate the stator windings by means of a rectifier. Preferably, a plurality of excitation coils are provided, which are arranged concentrically around the rotor's axis of rotation and thus circumferentially.

[0012] Particularly preferably, in the case of rotor de-excitation via a rectifier, particularly rapid de-excitation, the DC voltage present in the rotor windings can be converted to AC voltage, wherein the electrical energy extracted from the rotor windings can be induced from the rotor-side excitation coil to the stator-side excitation coil. Although power is typically transferred from the stator to the rotor during normal motor operation, it is conceivable that in certain situations, the reverse power transfer is necessary or advantageous. Such situations include fault conditions or accident conditions, in which it is necessary to reduce the rotor magnetic field. For this purpose, the current present in the rotor windings must be reduced. To this end, the rectifier is brought into a state by a corresponding control command, in which the DC voltage present in the rotor windings is converted to AC voltage, which is then applied to the rotor-side excitation coil. Power is correspondingly dissipated to the stator-side excitation coil. Therefore, within the scope of this embodiment, bidirectional power or energy transfer can be achieved by means of a rotary transformer and a rectifier.

[0013] According to the invention, it is conceivable that an electric motor has an inductive communication rotary transformer comprising at least one rotor-side communication coil present on the rotor and at least one stator-side communication coil present on the stator, wherein electrical control signals for controlling the operation of the rectifier can be induced and transmitted from the stator-side communication coil to the rotor-side communication coil. The aspects described in conjunction with the inductive rotary transformer are substantially similarly applicable to the communication rotary transformer. Therefore, it is conceivable, particularly for electric motors or related motor vehicles, to have a control device connected to the stator-side communication coil, configured to generate control signals for the operation of the rectifier, present on the stator side, and output them to the stator-side communication coil for transmission to the rotor.

[0014] For heat sinks, it can be specified that the cooling section has at least one cooling channel through which cooling fluid can flow. The cooling channel can be understood as an elongated cavity or corresponding chamber through which cooling fluid flows in its longitudinal direction.

[0015] Particularly preferably, at least one channel wall defining the cooling channel is provided in the cooling channel, or in at least one cooling channel, said at least one channel wall having a deflection structure that deflects the fluid flowing along the channel wall, particularly forming vortices / turbulence. Generally, the deflection structure can be a geometrical structure of the channel wall surface, deviating from a smooth or flat structure. The deflection structure may have protrusions on its inner side arranged in the cooling channel and protruding or extending from the channel wall. The deflection structure may particularly be provided only in the section of the cooling channel located directly below the rectifier. The deflection structure transforms the laminar flow of the cooling fluid, which is necessary in the cooling channel, into turbulent flow, thereby making heat transfer to the cooling fluid more efficient.

[0016] The deflection structure may have at least one cooling fin and / or at least one cooling rib. The cooling fin or rib can be understood in particular as a tabular, elongated structure extending longitudinally along the channel wall. This longitudinal direction may be arranged perpendicularly or obliquely relative to the flow direction of the cooling fluid, thereby correspondingly enhancing the deflection effect on the cooling fluid. The deflection structure may have multiple cooling fins or ribs arranged sequentially along the flow direction.

[0017] The motor according to the invention may have a rotor shaft connected to or forming part of a rotor, the rotor shaft having at least one shaft channel that at least partially extends through the rotor shaft and along a longitudinal direction, and through which cooling fluid may flow, wherein the cooling fluid may be delivered to a cooling section and / or discharged from a cooling section via the shaft channel or one of the shaft channels. The shaft channels or one of the shaft channels may be arranged concentrically or eccentrically with respect to the axis of rotation. If multiple shaft channels are provided, these shaft channels may extend through different longitudinal sections of the rotor shaft. If these shaft channels at least partially extend through the same longitudinal section of the rotor shaft, they may be staggered from each other in a radial and / or circumferential direction. An inlet spray gun may be provided to introduce cooling fluid into the shaft channels. To introduce cooling fluid into and / or discharge cooling fluid from the shaft channels, the rotor shaft may have at least one transverse hole communicating with a corresponding shaft channel and extending in a radial direction.

[0018] The cooling section can be a disc / disc body. This disc preferably extends concentrically about the axis of rotation. The disc can have a circular shape (viewed longitudinally). This disc can be a balancing disc for the rotor. The balancing disc helps prevent any imbalance in the rotor, for example, by removing material within it, thus achieving the smoothest possible operation of the rotor. This disc can be arranged on the end side of the rotor, i.e., on one of the two axial ends of the rotor.

[0019] The hollow interior of the disc, which specifically forms at least one cooling channel, is preferably shaped such that cooling fluid flows radially outward within the disc and then radially inward. The hollow interior or the corresponding cooling channel may be U-shaped, wherein two longitudinal beams of the U-shape extend radially outward and are connected by a crossbeam of the U-shape, which is arranged radially outward within the disc and extends circumferentially.

[0020] The rectifier is preferably defined as comprising at least one circuit board and semiconductor elements disposed on the at least one circuit board and usable within the range of AC voltage rectification. The circuit board particularly has conductive traces, and the circuit board is fixed to a cooling section. The circuit board can be understood as a printed circuit board on which the semiconductor elements are disposed. The circuit board may be made of plastic. The semiconductor elements may be fixed to the circuit board by means of soldering and / or press-fitting. The circuit board preferably has a planar, particularly flat, extension that extends parallel to the outer surface of the cooling section carrying the circuit board to achieve the most efficient thermal connection possible.

[0021] A thermally conductive medium can be arranged between the circuit board and the cooling section. The thermally conductive medium can be understood as a material with a sufficiently high thermal conductivity to achieve the most efficient possible heat transfer from the rectifier to the cooling section. The thermal conductivity can have a value of at least 10 W / (m·K). The thermally conductive medium is preferably a thermally conductive adhesive, which, in addition to achieving the most efficient heat transfer, can also serve as a fixing component to secure the rectifier to the cooling section.

[0022] Additionally or alternatively, the circuit board may have a metal core. Since metals generally have higher thermal conductivity, heat transfer via the circuit board is more efficient over the range of heat transfer from the semiconductor element to the cooling fluid. This is advantageous, for example, when the supporting structure of the circuit board (besides the metal core and, if necessary,, conductor traces) is made of plastic. The metal core can be made of aluminum and / or copper. The metal core is particularly covered by a layer of plastic in the direction towards the semiconductor element. In principle, the same applies to the direction towards the cooling section, where the metal core can also be in an open manner, allowing for direct contact between the metal core and the cooling section (in addition to the possible thermally conductive medium).

[0023] Preferably, the motor can be connected to the drivetrain of a motor vehicle, wherein the motor, in connection with the drivetrain, can generate traction torque and transmit this traction torque to the wheels of the motor vehicle via the drivetrain. Therefore, for example, an open end of a rotor shaft extending along the axis of rotation, particularly extending from the motor housing, can be provided. This end and the drivetrain components can each have connecting parts, such as connecting flanges, by which a mechanical connection, particularly a rotationally fixed mechanical connection, can be established between the shaft and the drivetrain. The drivetrain can be essentially understood as all the components through which a mechanical connection can be established between the motor and the wheels. Therefore, the drivetrain can include a drive shaft and / or a transmission, particularly a switching transmission and / or a differential transmission and / or a clutch.

[0024] The present invention also relates to a rotor for an electric motor for a motor vehicle, wherein the rotor is supported in a manner rotatable relative to the stator of the motor, and wherein the rotor includes rotor windings for generating a rotor magnetic field. According to the invention, this objective is achieved by a rotor having a power supply and an active rectifier electrically connecting the power supply to the rotor windings, by means of which an AC voltage supplied by the power supply can be converted into a DC voltage, which can be used in the process of generating a rotor magnetic field through the rotor windings, wherein the rectifier is arranged on or in a cooling section of the rotor, the cooling section forming a heat sink, and the cooling section being traversable by a cooling fluid. All the advantages, features, and aspects described in conjunction with the motor according to the invention are equivalently applicable to the rotor according to the invention, and vice versa.

[0025] Furthermore, the present invention relates to a motor vehicle. The objective is achieved by means of a motor vehicle according to the invention by having a power motor designed as an electric motor according to the above description. The motor is connected to the transmission system of the motor vehicle, wherein a traction torque can be generated by means of the motor and transmitted to the wheels of the motor vehicle via the transmission system. All advantages, features, and aspects described in conjunction with the motor and rotor according to the invention are equally applicable to the motor vehicle according to the invention, and vice versa.

[0026] Preferably, the motor vehicle according to the invention includes a cooling system by means of which cooling fluid can be guided, wherein a cooling section forming a heat sink is integrated into the cooling system. Therefore, the cooling system can be configured to form a cooling loop, in which cooling fluid can be conveyed by means of a conveying component. In this embodiment, the cooling fluid circulates from the conveying component to the cooling section and then returns, and thus circulates again. The conveying component may be a cooling fluid pump. A cooling device, such as a heat exchanger, for cooling the cooling fluid can be integrated into the cooling system.

[0027] Preferably, the motor vehicle according to the invention includes an energy storage device in which energy required during traction can be stored. This energy exists in the form of electrical energy and is converted into kinetic energy by means of a motor. Conversely, it is conceivable that the motor operates in a regeneration mode, in which the kinetic energy of the motor vehicle is converted into electrical energy, which is specifically stored in the energy storage device. DC voltage can typically be provided by means of the energy storage device, particularly a lithium-ion battery. However, the operation of the motor requires AC voltage, therefore a power electronics unit can be provided in the motor to convert the DC voltage provided in the energy storage device into AC voltage. A control device already described or another can be configured to generate control signals for the operation of the power electronics unit and output them to the power electronics unit. Attached Figure Description

[0028] Other advantages, features, and details of the invention will become apparent from the embodiments described below and from the accompanying drawings. The drawings schematically illustrate:

[0029] Figure 1 A schematic diagram of a motor vehicle according to the invention, shown in a side view according to one embodiment, is presented. The motor vehicle includes an electric motor according to one embodiment, together with a rotor according to one embodiment.

[0030] Figure 2 Show Figure 1 A simplified schematic diagram of the motor principle of a motor vehicle.

[0031] Figure 3 Show Figure 1 A longitudinal cross-sectional view of the motor section of a motor vehicle, and

[0032] Figure 4 Show Figure 3 A cross-sectional view of the rectifier section of the motor rotor. Detailed Implementation

[0033] Figure 1 A motor vehicle 1 according to an embodiment of the invention is shown, comprising a motor 2 according to an embodiment of the invention. The motor 2 includes a rotor 3 and a stator 4 according to an embodiment of the invention. The motor 2 is an internal rotor designed as a separately excited synchronous motor. Therefore, the rotor 3 is arranged radially further inward in a region of the motor 2 than the region in which the stator 4 is arranged. The rotor shaft 5 of the rotor 3 is rotatably supported on a housing 6 of the motor 2, for example by means of ball bearings or rolling bearings.

[0034] Motor 2 is configured to operate in a drive mode, in which electrical energy stored in the battery 7 of vehicle 1 is converted into kinetic energy of vehicle 1. The resulting driving torque for propelling vehicle 1 can be transmitted from motor 2 to the transmission system 8 of vehicle 1. The driving torque can only be transmitted to the rear wheels, however, it can also be additionally or alternatively transmitted to the front wheels. Motor 2 can also operate in a regeneration mode, in which the kinetic energy of vehicle 1 is converted into electrical energy by means of motor 2, which can be used, for example, to charge battery 7.

[0035] The definitions of the relevant spatial directions will now be explained in conjunction with motor 2. Therefore, rotor shaft 5 is rotatably supported about rotation axis 9, which extends along the longitudinal direction 10 of motor 2. Radial direction 11 extends perpendicular to longitudinal direction 10. Circumferential direction 12 is perpendicular to radial direction 11. That is, a point rotating about rotation axis 9 moves along circumferential direction 12.

[0036] The following is for reference. Figure 2 and Figure 3 Details regarding motor 2 are explained. Figure 2 A schematic diagram of the height of motor 2 is shown, specifically illustrating that the components of motor 2 are divided into rotor 3 and stator 4. Therefore, a power electronics unit 13 is provided in the stator 4 or the fixed section, by means of which the DC voltage supplied to the energy storage device 7 can be converted into AC voltage. For this purpose, a control device 14 is provided, configured to generate control signals for controlling the operation of the power electronics unit 13 and output them to the power electronics unit. With the AC voltage generated by the power electronics unit 13, the stator windings of the stator 4 (not shown in detail in the drawing) and the rotor windings 15 of the rotor 3 can be energized. Figure 2 Only one rotor winding is shown schematically. The stator winding and rotor winding 15, each composed of conductor wires, generate magnetic fields when energized, namely the rotor magnetic field and the stator magnetic field, which interact with each other in the process of generating driving torque or retraction torque.

[0037] Details regarding the transfer of electrical energy or power from the energy storage unit 7 to the stator winding 15 will be explained below. First, the DC voltage provided in the energy storage unit 7 is converted into AC voltage by means of the power electronics unit 13. This AC voltage is transmitted to the excitation coil 16 on the stator side of the stator 4, and through this stator-side excitation coil, induced energy is transmitted to the excitation coil 17 on the rotor side of the rotor 3. Therefore, the excitation coils 16 and 17 form an induction rotary transformer 18, through which non-contact energy transfer from the fixed section of the stator 4 or motor 2 to its rotor 3 can be realized.

[0038] The excitation coil 17 on the rotor side provides power to the rotor 3, generating an alternating current (AC) voltage. This AC voltage is supplied to the input of an active rectifier 19 on the rotor 3, which converts the AC voltage into a direct current (DC) voltage applied to its output. Therefore, the rectifier 19 connects the excitation coil 17 on the rotor side to the rotor winding 15, such that the voltage supplied via the excitation coil 17 and converted to DC by the rectifier 19 is supplied to the rotor winding 15 to generate a rotor magnetic field.

[0039] The active rectifier 19 includes a semiconductor element 35, wherein the AC voltage supplied by the excitation coil 17 on the rotor side is rectified according to a control signal. Therefore, the active rectifier 19 includes a controllable semiconductor element 35, i.e., in particular a transistor, although in Figure 2 The semiconductor diode is only symbolically shown in this context. In the present case, with the help of the active rectifier 19, not only can the AC voltage present on the input side, or in terms of the excitation coil 17 on the rotor side, be converted into the DC voltage present on the output side, or in terms of the rotor winding 15, but also, if a corresponding control signal is available for the active rectifier 19, the DC voltage can be converted back into the AC voltage.

[0040] The opposite situation—where the DC voltage present in the rotor winding 15 is converted into an AC voltage present in the excitation coil 17 on the rotor side by means of the active rectifier 19—is particularly important during the de-excitation range of the rotor 3. This de-excitation, or rapid de-excitation, is necessary, for example, in fault- or accident conditions and results in a weakening of the rotor magnetic field. During the de-excitation range, a control signal is generated and output to the active rectifier 19, which causes the DC voltage present in the rotor winding 15 to be converted into an AC voltage, which in turn induces energy transfer from the excitation coil 17 on the rotor side to the excitation coil 16 on the stator side.

[0041] In addition to generating control signals for the power electronics unit 13, the control device 14 is also configured to generate the aforementioned control signals for the operation of the active rectifier 19 and output them to the active rectifier via the induction communication rotary transformer 20. The communication rotary transformer 20 includes a stator-side communication coil 21 located on the stator 4 and a rotor-side communication coil 22 located on the rotor 3. The control signals from the control device 14, configured for the operation of the active rectifier 19, are inductively transmitted from the stator-side communication coil 21 to the rotor-side communication coil 22. The operating principle of the communication rotary transformer 20 is essentially the same as that of the rotary transformer 18.

[0042] The following is for reference. Figure 3Details regarding the cooling system 23 of the motor vehicle 1 are described below. The cooling system 23 guides cooling fluid and forms a cooling circuit. Accordingly, the cooling system 23 includes a delivery component 24, such as a delivery pump, by means of which the circulation of the cooling fluid is driven. Furthermore, the cooling system 23 includes a cooling device 25, i.e., a heat exchanger, for cooling the cooling fluid.

[0043] In addition to the cooling system 23, which is shown in a very schematic manner, Figure 3 The upper half of a longitudinal section of a portion of the motor 2 is also shown. Only a portion of the rotor 3 and the stator 4 are shown here, with particular emphasis on the upper half of the rotor shaft 26 extending along the axis of rotation 9.

[0044] An important aspect related to the cooling effect achieved by means of cooling system 23 involves the cooling of rectifier 19 present in rotor 3. This is necessary because rectifier 19, as an active control component, is more susceptible to heat dissipation than, for example, passive rectifiers. For this purpose, rectifier 19 is arranged on cooling section 27 of rotor 3, which forms a heat sink and is integrated into cooling system 23 and traversed by cooling fluid. The specific flow path of the cooling fluid is as follows... Figure 3 As shown by the arrow in the image.

[0045] Therefore, the cooling fluid arrives from the delivery component 24 at the inlet opening 28 arranged on the end side of the rotor 3 or rotor shaft 26. The cooling fluid is introduced through this inlet opening into the input shaft channel 29, which partially penetrates the rotor shaft 26 and extends along the longitudinal direction 10, via an inlet spray gun (not specifically shown). Next, the cooling fluid reaches the cooling section 27, which is here a disc 30 arranged on the end side of the rotor 3, serving as a balancing disc.

[0046] The input shaft channel 29 leads into the hollow interior of the disc 30, which forms the cooling section 27 or the cooling channel 31 of the disc 30. (Reference) Figure 3 In the longitudinal cross-sectional view, the cooling channel 31 has an inverted U-shape, so that the cooling channel first extends radially outward from the input shaft channel 29 to the radially outer region of the disc 30, and then radially inward, finally entering the output shaft channel 32. This output shaft channel also partially penetrates the rotor shaft 26 and extends along the longitudinal direction 10. Regarding the cooling section 27, the input shaft channel 29 extends on one side of the rotor shaft 26, while the output shaft channel 32 extends on the other side of the rotor shaft 26. Cooling fluid exits the motor 2 or rotor 3 through the discharge opening 33, which is opposite the end of the inlet opening 28. After exiting the discharge opening, the cooling fluid reaches the cooling device 25 and then the conveying component 24.

[0047] Specifically, regarding the cooling specifications of the rectifier 19, a portion of the cooling channel 31 extending through the cooling section 27 is arranged directly below the rectifier 19, i.e., the corresponding U-shaped radially inward section in this case. In order to achieve the most efficient heat transfer possible from the rectifier 19 to the cooling fluid, the thickness of the material remaining between the cooling channel 31 and the rectifier 19 in the cooling section 27 is as small as possible, preferably only a few millimeters.

[0048] In the region of the cooling channel 31 directly below the rectifier 19, a deflection structure 34 is provided on the channel wall defining the cooling channel 31. This deflection structure deflects the cooling fluid flowing through the cooling channel 31 and forms a vortex. This makes the heat transfer from the rectifier 19 to the cooling fluid more efficient. The deflection structure includes multiple elongated, plate-like structures arranged sequentially perpendicular to the flow direction, which can also be called cooling fins or cooling ribs.

[0049] The following describes the details of the structure of rectifier 19. For this purpose, refer to... Figure 4 It shows a cross-sectional view of a section of the rectifier 19, wherein the section is vertically arranged on a flat and planar printed circuit board or circuit board 36. The cooling section 27 carrying the rectifier 19 is... Figure 4 Not shown in the diagram. Therefore, the rectifier 19 includes a circuit board 36 on which semiconductor elements 35 are arranged. The circuit board 36 is fixed to the cooling section 27 or the tray 30 by means of a thermally conductive medium 37 (which is a thermal adhesive). This layer is disposed between the circuit board 36 and the cooling section 27.

[0050] Furthermore, the circuit board 36 includes a metal core 38 made of aluminum and / or copper, disposed between two layers 39 made of plastic. The layer 39 facing the cooling section 27 can also be omitted, thus the metal core 38 is open and can directly contact the thermally conductive medium 37 or the cooling section 27. The thermally conductive medium 37 and the metal core 38 improve or enhance the efficiency of heat transfer from the rectifier 19 or semiconductor element 35 to the cooling fluid.

Claims

1. An electric machine (2), in particular a separately excited synchronous electric machine, for a motor vehicle (1), comprising a stator (4) and a rotor (3) which is rotatably supported relative to the stator (4), the rotor having rotor windings (15) for generating a rotor magnetic field, wherein An active rectifier (19) is provided on the rotor (3), which electrically connects an electrical power source present on the rotor (3) to the rotor winding (15), by means of which an alternating voltage supplied by the electrical power source can be converted into a direct voltage, which can be used in the production of a rotor field by the rotor winding (15), wherein the rectifier (19) is arranged on or in a cooling section (27) of the rotor (3), which forms a heat sink, which can be flowed through by a cooling fluid.

2. The electric machine (2) according to claim 1, characterized in that An inductive rotary transformer (18) is provided, which comprises at least one rotor-side field winding (17) present on the rotor (3) and forming an electrical power source and at least one stator-side field winding (16) present on the stator (4), wherein electrical energy can be inductively transferred from the stator-side field winding (16) to the rotor-side field winding (17).

3. The electric machine (2) according to claim 2, characterized in that In the context of de-excitation of the rotor (3) by means of the rectifier (19), a direct voltage present on the rotor winding (15) can be converted into an alternating voltage, wherein electrical energy extracted from the rotor winding (15) here can be inductively transferred from the rotor-side field winding (17) to the stator-side field winding (16).

4. The electric machine (2) according to any one of the preceding claims, characterized in that, An inductive communication rotary transformer (20) is provided, which comprises at least one rotor-side communication coil (22) present on the rotor (3) and at least one stator-side communication coil (21) present on the stator (4), wherein electrical control signals for a control operation of the rectifier (19) can be inductively transferred from the stator-side communication coil (21) to the rotor-side communication coil (22).

5. The electric machine (2) according to any one of the preceding claims, characterized in that, The cooling section (27) has at least one cooling channel (31), which can be flowed through by a cooling fluid.

6. The electric machine (2) according to claim 5, characterized in that In the cooling channel (31) or in the at least one cooling channel (31), at least one channel wall delimiting the cooling channel (31) is provided, which has a deflection structure (34) deflecting the fluid flowing along the channel wall, in particular forming a vortex.

7. The electric machine (2) according to claim 6, characterized in that The deflection structure (34) has at least one cooling fin and / or at least one cooling rib.

8. The electric machine (2) according to any one of the preceding claims, characterized in that, A rotor shaft (26) is provided, which is connected to the rotor (3) or forms part of the rotor (3), the rotor shaft having at least one shaft channel (29, 32) which extends at least partially through the rotor shaft (26) in the longitudinal direction (10) and can be flowed through by a cooling fluid, wherein the cooling fluid can be fed to the cooling section (27) and / or can be discharged from the cooling section (27) via the shaft channel (29) or one of the shaft channels (29).

9. The electric machine (2) according to any one of the preceding claims, characterized in that, The cooling section (27) is a disc piece (30), which is arranged in particular on an end side of the rotor (3).

10. The electric machine (2) according to claim 9, characterized in that The geometry of the hollow interior of the disc piece (30), which forms the at least one cooling channel (31), is shaped in such a way that the cooling fluid flows in the disc piece (30) outwards in the radial direction (11) and then inwards in the radial direction (11).

11. The electric machine (2) according to any one of the preceding claims, characterized in that The rectifier (19) comprises at least one circuit board (36) and semiconductor elements (35) arranged on the at least one circuit board and usable in the range of the rectification of the alternating voltage, wherein the circuit board (36) is fixed on the cooling section (27).

12. The electric machine (2) according to claim 11, characterized in that A thermally conductive medium (37), in particular a thermally conductive adhesive, is arranged between the circuit board (36) and the cooling section (27), and / or the circuit board (36) has a metal core (38), in particular made of aluminum and / or copper.

13. A rotor (3) for an electric machine (2) of a motor vehicle (1), wherein The rotor (3) is rotatably supported relative to a stator (4) of the electric machine (2), the rotor comprising rotor windings (15) for generating a rotor magnetic field, an electrical power source and an active rectifier (19) electrically connecting the electrical power source to the rotor windings (15), by means of which an alternating voltage provided by the electrical power source can be converted into a direct voltage, which can be used in the generation of the rotor magnetic field by the rotor windings (15), wherein the rectifier (19) is arranged on or in a cooling section (27) of the rotor (3), the cooling section forming a heat sink, which can be flowed through by a cooling fluid.

14. Motor vehicle (1), characterized in that A motor vehicle (1) is provided with a drive machine designed as an electric machine (2) according to any one of claims 1 to 12, wherein the electric machine (2) is connected to a drive train (8) of the motor vehicle (1), wherein a traction torque can be generated by means of the electric machine (2) and can be transmitted to a wheel of the motor vehicle (1) via the drive train (8).

15. Motor vehicle (1) according to claim 14, characterized in that A cooling system (23) is provided, in particular forming a cooling circuit, by means of which a cooling fluid can be guided, wherein the cooling section (27) forming a heat sink is integrated into the cooling system (23).

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