Transformer for externally excited synchronous machines: bonding via bearings

Abstract

The invention relates to a contactless energy transfer device for a rotor of an electric machine, in particular an externally excited synchronous machine, in a powertrain of a motor vehicle, comprising: a housing part (6) which can be coupled in a rotationally rigid manner to a housing of the electric machine; and an induction transformer having a primary coil (1), which can be energized, and a secondary coil (2), which is arranged at a distance from the primary coil and can be coupled in an electrically conductive manner to a winding of the rotor; a roller bearing (5), by means of which a rotor shaft (7) is mounted in a rotatable manner relative to the housing part (6), the primary coil (1) of the induction transformer (5) being positioned on the housing part (6) in a rotationally rigid manner relative to the housing part, the primary coil (1) is arranged in the housing part (6), and the roller bearing (5) is arranged in the housing part (6) such that the primary coil (1) and the roller bearing (5) are arranged coaxially, and the secondary coil (2) of the induction transformer is arranged in a transformer housing (8), the transformer housing being connected to the rotor in a rotationally fixed manner.

Description

Technical Field

[0001] The invention relates to a contactless energy transmission device for a rotor of an electric machine, in particular an externally excited synchronous machine, in a powertrain of a motor vehicle. Background Art

[0002] Electric machines are increasingly used to drive motor vehicles in order to create an alternative to fossil fuel-intensive internal combustion engines. Considerable efforts have been made to improve the suitability of electric drives for everyday use and also to be able to provide users with the driving comfort to which they are accustomed.

[0003] A detailed description of the electric drive can be found in an article by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold published in the German automobile magazine ATZ, Vol. 113, May 2011, pages 360 to 365, entitled: Hochintegrativ und Flexibel Elektrische Antriebseinheit für E-Fahrzeuge [Highly Integrative and Flexible Electric Drive Unit for E-Vehicles]. The article describes a drive unit for an axle of a vehicle, which includes an electric motor. Such a drive unit is also referred to as an electric axle or an electrically operable powertrain.

[0004] In addition to purely electrically operated powertrains, hybrid powertrains are also known. Such powertrains of hybrid vehicles generally comprise a combination of an internal combustion engine and an electric motor and enable, for example, a purely electric operating mode in urban areas, while at the same time allowing both sufficient range and usability, in particular also when driving off-road. In addition, in certain operating situations it is also possible to provide drive simultaneously by the internal combustion engine and the electric motor. According to embodiments, both purely electric powertrains and hybrid powertrains have a transmission, which is used, for example, to adjust the speed and power range.

[0005] When developing electric machines intended for electric axles or hybrid modules, there is a need to continuously increase the power density and efficiency of the electric machines while reducing the manufacturing costs, since the cost and weight of the vehicle will be determined to a large extent by the battery size. In this context, it is also known to design the electric machine as an externally excited synchronous machine. The power used to excite the rotor windings must be transferred to the rotor of the externally excited synchronous machine. For traction machines, contact-based transformers are usually used for this purpose. When these windings are energized, a magnetic field is generated, which, in combination with the magnetic field of the stator, generates a torque. The strength of the rotor magnetic field can be adjusted by the strength of the current supply. In this way, the machine behavior can always be adapted to the respective driving situation in an efficient manner.

[0006] The disadvantages of such contact-based transformers are the mechanical and electrical losses in the contact between the stationary and rotating parts. Other disadvantages are the wear of the parts rubbing against each other and the contamination caused by abrasion and the relatively large installation space required.

[0007] As an alternative to such contact-based transformers, contactless induction transformers are also known. An induction transformer is usually a rotationally symmetrical transformer comprising a primary winding and a secondary winding with an air gap. Typically, an induction transformer also has a core, for example made of ferrite. Such a core may consist of one or more parts.

[0008] For example, all parts of the core can be attached to the fixed machine side of the motor, wherein the secondary side winding rotates inside the core. Alternatively, the core part can be attached to the rotating part of the machine. In this case, the primary core part and the secondary core part are separated by an air gap. Taking into account all tolerances and operating conditions, the air gap must then be large enough so that the core parts do not contact each other. For this purpose, the rotary transformer part is usually provided with a coupling or is connected to another component in order to support the rotary transformer part at a fixed speed. Examples of such design variations can be found in DE 10 2017 214 776 A1 or DE201210201826A1. Summary of the invention

[0009] The object of the present invention is now to provide a contactless energy transmission device for an electric machine in a powertrain of a motor vehicle, in particular a rotor of an externally excited synchronous machine, which contactless energy transmission device also has a compact design and a high level of operational reliability when transmitting high levels of electric power.

[0010] This object is achieved by the measures described in the independent claim. Advantageous embodiments can be found in the dependent claims.

[0011] The primary coil of the energy transmission device of the electric machine, which comprises a ferrite core and a winding, is referred to as a transformer for short, and is arranged coaxially around a roller bearing, also referred to as a rotor bearing in the following text, which comprises a bearing outer ring. The bearing outer ring is inserted into a housing part, on which the primary coil is arranged on the outer diameter of the housing part. The housing part is an integral part of the support plate or is connected to the support plate. This arrangement can be realized on both the side of the electric machine facing the transmission and the side facing away from the transmission. The housing part is preferably designed as a substantially rotationally symmetrical body, which can be divided into two cylindrical annular sections. The second cylindrical annular section extends radially outwards from the outer side surface of the first cylindrical annular section.

[0012] The coaxial arrangement of the rotor bearing and transformer makes it possible to save axial installation space and keep the external dimensions of the machine compact. In addition, a design with a radial air gap and a flat but axially long coil cross section can be selected for the motor, which is electromagnetically advantageous.

[0013] The primary coil is thermally connected to the housing part on which it is arranged, so that heat from the primary coil can be dissipated via the housing part, in particular to a machine housing of the electric machine, and thermal overloading can be avoided.

[0014] Inverter electronics for supplying the primary side are incorporated between the housing part and the primary coil and are thermally connected to the housing part, which is in particular designed as a support plate. In this way, heat from the inverter electronics can be dissipated, in particular to the machine housing, and thermal overload can be avoided.

[0015] The arrangement of the primary coil, the inverter electronics and the housing parts represents an independent, manufacturable and testable unit which increases the quality of the machine and reduces waste. In other words, the primary coil, the inverter electronics and the housing parts form a modular structural unit.

[0016] In one embodiment, the housing part, which is designed in particular as a support plate, has at least one channel integrated therein, which extends at least partially radially or tangentially for guiding a cooling liquid, thereby improving heat dissipation. The channel is in particular arranged as a through opening leading to the interior of the housing part. Thus, a heat transfer from the inverter electronics to the cooling medium occurs via the housing part. The inverter electronics are arranged on an axial surface of the housing part. The axial surface preferably faces the electric machine.

[0017] In another embodiment, at least one groove is formed in the support plate, which groove is covered by the inverter electronics and thus forms a channel for guiding the cooling liquid. Elements such as ribs or pins can be formed in the groove to increase the surface area facing the cooling medium. This can further improve the heat dissipation from the primary coil and the inverter electronics.

[0018] In one embodiment, the primary coil and the inverter electronics are cast on the housing part with epoxy or overmolded with plastic, which improves protection against environmental influences, thermal coupling and electrical insulation of the components.

[0019] The secondary coil comprises a ferrite core and a winding and is inserted into a substantially can-shaped housing, also referred to as a transformer housing. In other words, the transformer housing is designed as a hollow cylindrical piece, which preferably has a connection piece at the distal end for being particularly mounted on a rotor, in particular a rotor shaft. Rectifier electronics are also positioned inside the housing, and the rectifier electronics are thermally connected to the housing. The housing is preferably mounted to the rotor housing or the rotor body in the axial direction. The housing has an opening for the passage of a cable. The housing can be made of, for example, aluminum or glass fiber reinforced plastic. The housing can include a plurality of parts. Alternatively, the housing can be integrally connected to the rotor housing or the rotor body or formed by either of the rotor housing or the rotor body.

[0020] This arrangement ensures that the rectifier electronics and secondary coils are securely supported and thermally coupled to the rotor housing at high speeds so that heat can be dissipated. Additionally, heat can be dissipated by convection via the radially outer surface of the transformer housing.

[0021] The secondary side arrangement comprises the secondary coil, the rectifier electronics and the transformer housing. The secondary side arrangement represents an independent, manufacturable and testable unit which improves the quality of the machine and reduces waste. In other words, the secondary coil, the rectifier electronics and the transformer housing form a modular structural unit.

[0022] In one embodiment, the outer surface of the transformer housing is provided with tangential ribs which improve speed stability and convective heat dissipation.

[0023] In one embodiment, the rectifier electronics and secondary coil are cast in the transformer housing with epoxy or overmolded with plastic, which improves protection against environmental influences, thermal coupling, and electrical insulation of the components.

[0024] In a further embodiment, at least one chamber between the rotor housing and the transformer housing forms a channel for conducting a cooling medium, thereby improving the heat dissipation from the secondary-side arrangement.

[0025] The various elements of the claimed subject matter of the present invention are explained below.

[0026] The rotor is the rotating (turning) part of the electric machine. The rotor comprises in particular a rotor shaft. The rotor shaft may be hollow, which on the one hand results in a reduced weight and on the other hand allows a lubricant or coolant to be supplied to the rotor body. Preferably, the hollow shaft of the contactless energy transmission device is a rotor shaft of a rotor of an electric machine, which rotor shaft is at least partially hollow.

[0027] In particular, the electric machine can be designed as a rotary machine. In particular, the rotary machine can be constructed as a radial flow machine. A radial flow machine is characterized by the fact that the magnetic field lines formed in the air gap between the rotor and the stator extend in the radial direction. The gap between the rotor and the stator is called the air gap. In a radial flow machine, this gap is an annular gap with a radial width corresponding to the distance between the rotor body and the stator body.

[0028] The electric machine is particularly intended for use in a powertrain of a hybrid-drive or fully-electric motor vehicle. In particular, the electric machine is dimensioned such that a vehicle speed of more than 50 km / h, preferably more than 80 km / h, and in particular more than 100 km / h can be achieved. The electric motor particularly preferably has an output of more than 50 kW, preferably more than 80 kW, and in particular more than 150 kW. Furthermore, it is preferred that the electric machine provides a speed of more than 8,000 rpm, particularly preferably more than 12,000 rpm, very particularly preferably more than 1,500 rpm.

[0029] For the purposes of this application, a motor vehicle is a land vehicle that moves by machine power without the constraints of railway tracks. The motor vehicle may for example be selected from the group of a passenger car, a truck, a scooter, a light motor vehicle, a motorcycle, a motor bus / coach or a tractor.

[0030] The induction transformer is configured such that preferably more than 1 kW and particularly preferably more than 2 kW of power can be transmitted, at least for a short period of time, without the transformer being electrically or thermally overloaded. Most preferably, the induction transformer is configured to transmit between 0.5 kW and 10 kW of power, preferably between 1 kW and 5 kW, particularly preferably between 2 kW and 4 kW of power.

[0031] The windings of the transformer are made of an electrically conductive but non-ferromagnetic material, such as copper or aluminum, and are electrically insulated from each other. Preferably, the windings are aligned tangentially around the hollow axis, thereby obtaining a cylindrical annular winding body having a diameter and a longitudinal extension in the axial direction. Most preferably, the windings are wound around and / or in a core made of a ferromagnetic material.

[0032] The winding may be formed from one or more electrical conductors having a circular cross section. It is also conceivable that the electrical conductors forming the winding have a cross-sectional shape deviating from a circular shape, in particular a rectangular shape. Particularly preferably, the winding may be formed from insulating copper foils which may be wound around each other in a similar manner to toilet paper rolls.

[0033] According to another advantageous improvement of the present invention, the primary winding can have a higher number of turns than the secondary winding. This means that when transferring electrical energy between the primary winding and the secondary winding, a voltage conversion from a relatively high battery voltage to a lower rotor voltage can be achieved.

[0034] In this context, it is further preferred that a voltage of 40 V to 1500 V, preferably 100 V to 1000 V, most preferably 300 V to 850 V is applied to the primary winding. Furthermore, in this context, it is preferred that a voltage of 70 V to 500 V is applied to the secondary winding.

[0035] The primary core and / or the secondary core are made of a ferromagnetic material, preferably a ferrite material. The primary core and / or the secondary core can be designed in several parts. The respective core parts are preferably substantially rotationally symmetrical, but can contain elements and recesses for fixing or realizing additional components.

[0036] Particularly preferably, the primary core and / or the secondary core each have an annular spatial shape. Most preferably, the primary core and / or the secondary core have / have a U-shaped cross-sectional profile with a circumferential groove. Preferably, the grooves of the U-shaped cross-sectional profiles of the primary core and the secondary core are oriented toward each other. It is also particularly preferred that the primary winding extends in the groove of the primary core and / or the secondary winding extends in the groove of the secondary core. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Both the present invention and the technical field are explained in more detail below with reference to the accompanying drawings. It should be noted that the present invention is not intended to be limited to the exemplary embodiments shown. In particular, unless otherwise explicitly stated, sub-aspects of the subject matter explained in the drawings may also be extracted and these sub-aspects may be combined with other components and knowledge from the present specification and / or the drawings. In particular, it should be noted that the drawings shown and in particular the proportions are only schematic in nature. The same reference numerals indicate the same objects, so that explanations from other drawings may also be used where applicable. Unless different references are explicitly used, terms such as "radial", "axial" or similar refer to the axis of rotation of the motor. In addition, in order to improve the readability of the drawings, in some cases only separate or several identical elements are provided with reference numerals.

[0038] In the attached picture:

[0039] Figure 1An electric machine with a contactless energy transmission device in a first embodiment is shown in a schematic axial cross-sectional view,

[0040] Figure 2 A schematic axial cross-sectional view shows an electric machine with a contactless energy transmission device in a second embodiment,

[0041] Figure 3 A schematic axial cross-sectional view shows an electric machine with a contactless energy transmission device in a third embodiment,

[0042] Figure 4 An electric machine with contactless energy transmission in a fourth embodiment is shown in a schematic axial section. DETAILED DESCRIPTION

[0043] Figure 1 The motor with a contactless energy transmission device in the first embodiment is shown in a schematic axial cross-sectional view. The motor is an externally excited synchronous motor. The rotor 110 includes a rotor shaft 7 designed as a hollow shaft and a rotor body in which a winding is arranged to form a magnetic field. The rotor body is closed by a rotor housing 13 in the axial direction. The rotor shaft 7 is rotatably arranged in a housing part 6 designed as a support plate via a roller bearing 7. The housing part is designed as a rotating body, which has a first cylindrical annular section with an inner lateral surface and an outer lateral surface. The roller bearing is arranged on the inner lateral surface with its outer ring. The primary coil 1 of the induction transformer with an energy transmission device is arranged on the outer lateral surface. The primary coil 1 and the roller bearing 5 overlap at least partially in the axial direction. In addition, the roller bearing 5 and the primary coil 1 are arranged coaxially. The primary coil 1 includes a ferrite core 9 and a winding 10. The second cylindrical annular section of the housing part 6 extends in the radial direction starting from the outer lateral surface of the first cylindrical annular section. Thus, the first cylindrical annular section and the second cylindrical annular section form an L-shaped cross section, wherein one leg is aligned parallel to the axis of rotation of the rotor and the other leg extends radially outward. The inverter electronics 3 are arranged on the first axial surface of the second cylindrical annular section. The first axial surface of the second cylindrical annular section faces the rotor 110. In the illustrated embodiment, the primary coil 1 and the inverter electronics 3 are encapsulated with epoxy compounds to prevent environmental influences and improve thermal coupling and electrical insulation of the components. Thus, the primary coil 1, the inverter electronics 3 and the housing portion 6 form a modular structural unit.

[0044] A transformer housing 8 is arranged in the axial direction on the rotor housing 13 and is connected to the rotor housing 13 in a rotationally fixed manner. A secondary winding 2 is arranged on the inner lateral surface of the transformer housing. The secondary coil 2 comprises a ferrite core 11 and a winding 12. The secondary winding 2 is arranged coaxially with the primary winding 1 and overlaps with the primary winding in the axial direction. The transformer housing 8 has an axial surface facing away from the rotor, on which the rectifier electronics 4 are arranged. The secondary winding is connected to the winding of the rotor (not shown in this view) in an electrically conductive manner via the rectifier electronics 4. In the embodiment shown, the secondary coil 2 and the rectifier electronics 4 are encapsulated with an epoxy compound to prevent environmental influences and improve the thermal coupling and electrical insulation of the components. Therefore, the secondary coil 2, the rectifier electronics 4 and the transformer housing 8 form a modular structural unit.

[0045] Figure 2 The schematic axial cross-sectional view shows an electric machine with a contactless energy transmission device in a second embodiment. Figure 1 The first embodiment of the invention differs only in the channel 16 in the second cylindrical annular section of the housing part 6. The channel is designed to carry the cooling liquid and is connected to a cooling system (not shown). The cooling channel extends partially in the radial direction and in the tangential direction within the housing part 6 and thus forms a tortuous structure. The channel 16 is arranged in the radial direction in the region of the inverter electronics 3 in order to achieve the best possible heat dissipation. The channel 16 is designed as a closed line in the housing part 6 so that the cooling liquid does not come into direct contact with the inverter electronics 3.

[0046] Figure 3 An electric machine with a contactless energy transmission device in a third embodiment is shown in a schematic axial cross-sectional view. The third embodiment allows direct cooling or heat dissipation of the inverter electronics 3. In the second cylindrical annular section, a groove 17 is formed in the first axial surface, which groove is closed by the inverter electronics 3 and thus forms a channel 16 for guiding the cooling liquid. Ribs (18) are formed in the groove to increase the cooling surface. This leads to better heat dissipation. Although the second and third embodiments are shown as alternatives, a combination of the closed channel of the second embodiment and the channel of the third embodiment is possible.

[0047] Figure 4An electric machine with a contactless energy transmission device in a fourth embodiment is shown in a schematic axial cross-sectional view. The fourth embodiment differs from the first embodiment in the following elements. The fourth embodiment can be combined with both the second embodiment and the third embodiment. In the fourth embodiment, the radial outer surface of the transformer housing 8 has ribs 17 extending approximately tangentially. Due to the increased surface area of ​​the radial outer surface, this leads to improved speed stability and improved convection heat dissipation. In addition, a cavity 20 is arranged between the rotor housing and the transformer housing, which cavity forms a channel 16 for guiding a cooling medium and is connected to a cooling system (not shown). This improves heat dissipation, in particular in the area of ​​the rectifier electronics 4 and the secondary coil 2.

[0048] The present invention is not limited to the embodiments shown in the accompanying drawings. Therefore, the above description should not be regarded as limiting, but rather as illustrative. The attached claims should be understood to mean that the stated features exist in at least one embodiment of the present invention. This does not exclude the existence of other features. Where the claims and the above description define a "first" feature and a "second" feature, such naming is used to distinguish between two features of the same type without defining the order of precedence.

[0049] Reference numerals list

[0050] 1. Primary coil

[0051] 2. Secondary coil

[0052] 3. Inverter electronics

[0053] 4. Rectifier electronics

[0054] 5. Roller bearings / rotor bearings

[0055] 6. Shell part / support plate

[0056] 7. Rotor shaft

[0057] 8. Transformer housing

[0058] 9. Ferrite core of primary coil

[0059] 10. Winding of the primary coil

[0060] 11. Ferrite core of secondary coil

[0061] 12. Secondary coil winding

[0062] 13. Rotor housing

[0063] 14. Castings or plastic overmolded parts

[0064] 15. Castings or plastic overmolded parts

[0065] 16. Cooling channel

[0066] 17. Groove

[0067] 18. Rib

[0068] 20. Cavity

[0069] 100. Motor

[0070] 110. Rotor

Claims

1. A contactless energy transmission device for a rotor of an electric machine, in particular an externally excited synchronous machine, in a powertrain of a motor vehicle, the contactless energy transmission device comprising: - a housing part (6) which can be coupled to the housing of the electric machine in a rotationally rigid manner, and an induction transformer having a primary coil (1) which can be energized and a secondary coil (2) which is arranged at a distance from the primary coil and can be coupled to the winding of the rotor in an electrically conductive manner, a roller bearing (5), by means of which the rotor shaft (7) is rotatably mounted relative to the housing part (6), It is characterized in that The primary coil (1) of the induction transformer (5) is positioned relative to the housing part (6) in a rotationally rigid manner relative to the housing part, and The roller bearing (5) is arranged in the housing part (6) such that the primary coil (1) and the roller bearing (5) are arranged coaxially, and The secondary coil (2) of the induction transformer is arranged in a transformer housing (8), wherein the transformer housing is connected to the rotor in a rotationally fixed manner.

2. The contactless energy transmission device (1) according to claim 1, wherein The primary winding (6) and the secondary winding (7) of the induction transformer (5) are arranged coaxially with each other in the transformer housing (8).

3. The contactless energy transmission device (1) according to claim 1 or 2, wherein The roller bearing (5) comprises an inner ring and an outer ring, and a plurality of rolling elements (28) are accommodated between the inner ring and the outer ring, wherein: The inner ring is connected to the rotor shaft (7) in a rotationally fixed manner, and the outer ring is connected to the housing part (6) in a rotationally fixed manner.

4. The contactless energy transmission device according to claim 3, wherein The shell part (6) has a first cylindrical annular section, the primary coil (1) is arranged on the outer lateral surface of the first cylindrical annular section, and the outer ring of the roller bearing (5) is arranged on the inner lateral surface of the first cylindrical annular section so that the roller bearing and the primary coil at least partially overlap.

5. The contactless energy transmission device according to claim 4, wherein The housing portion (6) has a second cylindrical annular section extending radially outwardly from the outer lateral surface of the first cylindrical annular section, wherein Inverter electronics (3) are arranged on a first axial surface of the second cylindrical annular section facing the rotor.

6. A contactless energy transmission device according to any one of the preceding claims, wherein The housing part (6) is a support plate for the electric motor.

7. A contactless energy transmission device according to any one of the preceding claims, wherein The housing part has a channel (16) for conducting a cooling liquid.

8. The contactless energy transmission device according to claim 6, wherein A channel (16) in the second cylindrical annular section is formed by a groove in the first axial surface and the inverter electronics (3) covering the groove.

9. The contactless energy transmission device (1) according to any one of claims 1 to 5, wherein The primary coil (1), the inverter electronics (3) and the housing part (6) form a modular structural unit.

10. The contactless energy transmission device (1) according to any one of claims 1 to 6, wherein The secondary coil (2), the rectifier electronics (4) and the transformer housing (8) form a modular structural unit.

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