Device for an inductively electrically excited synchronous machine for driving a vehicle, rotor shaft, electric motor and vehicle

Abstract

The invention relates to a device (2) for an inductively electrically excited synchronous machine for driving a vehicle, wherein the device (2) comprises a first portion that is stationary with respect to a housing (26) of the synchronous machine and a second portion that is non-stationary with respect to the housing (26). A transformer (8) having an air gap is located between the first and the second portion, which transformer contactlessly transmits the electrical energy, wherein a control unit having a printed circuit board (12) and an energy storage means that is activatable as required for increasing inductively provided electrical energy is provided in the second portion. The invention also relates to a rotor shaft, to an electric motor and to a vehicle.

Description

[0001] Description

[0002] Device for an inductively excited synchronous machine for driving a vehicle, rotor shaft, electric motor and vehicle

[0003] The invention relates to a device for an inductively excited synchronous machine for driving a vehicle. The invention further relates to a rotor shaft with such a device, an electric motor with such a device or rotor shaft, and a vehicle with such an electric motor.

[0004] Synchronous machines are rotating-field electrical machines that require a constant magnetic field on a rotor to operate. This constant magnetic field can be provided either by permanent magnets or by an energized electrical rotor winding, also called a (rotor) coil.

[0005] Such permanent magnets are referred to as permanent magnet synchronous motors. This type of synchronous motor is currently the most commonly used motor type in electric vehicles. The key advantages of this type of motor are high power density and excellent efficiency at low to medium speeds and torques. However, the disadvantage of this type of motor is that permanent magnets are temperature-sensitive and, due to the use of rare earth metals, their price is difficult to calculate. Furthermore, the non-controllable DC magnetic field of the permanent magnets has a negative impact on the efficiency of the motor, especially at high speeds.

[0006] In the context of an energized electrical rotor winding, however, one speaks of an electrically excited or separately excited synchronous machine, in which electrical energy must be transferred from a stator to a rotating rotor. For this purpose, slip rings are used on the rotor side, which are contacted by associated brushes fixed to the stator, so that the excitation current is transferred via contact or friction. Due to the principle of operation, this is accompanied by abrasion of the slip rings, which eventually wear out and therefore require replacement.

[0007] Such contacting devices require a corresponding amount of space. At higher speeds and in the case of externally induced shocks—for example, due to uneven road surfaces—brief contact losses can occur between the slip rings and the brushes. This manifests itself in the formation of electrical arcs, which in turn represent thermal hot spots.

[0008] The use of an inductive transformer system provides a contactless and thus wear-free alternative to the excitation or external excitation of a rotor's DC magnetic field. A coil system of the inductive transformer system can be integrated into a rotor shaft to save space.

[0009] An object underlying the invention is to provide an improved contactless excitation or external excitation of a DC magnetic field of a rotor of such a synchronous machine.

[0010] This object is achieved by a proposed device having the features of claim 1. The subclaims relate to advantageous developments.

[0011] The proposed device enables the smallest possible design and construction of an inductive transformer. This, in turn, enables optimal utilization of the inductive transformer system and transformer, thus achieving improved efficiency of the inductive transformer system and transformer in a partial load range of the synchronous machine. Furthermore, the smallest possible design and construction also allows the costs of such a transformer system and transformer to be significantly reduced (cost savings). The proposed device thus also increases the efficiency of the synchronous machine. Furthermore, the thermal load on the transformer system and transformer can be reduced.

[0012] The proposed energy storage or buffer storage, which can be activated separately on the rotor side as needed, provides the necessary additional excitation power when needed, for example, during start-up of the synchronous machine or during an acceleration phase of the synchronous machine. Outside of these phases or times, this energy storage or buffer storage recharges.

[0013] The transformer can thus advantageously be designed for continuous operation, whereas the energy storage or buffer storage can be designed in such a way that it can - in such a case of need - provide a power difference compared to this continuous operation for a required time (duration) or period of time of, for example, up to 10s, in which an increased excitation power or even a maximum power or maximum excitation power is required.

[0014] Thus, the transformer can be designed in such a way that it can, for example, contribute or provide approximately half or at most half of the maximum excitation power that can be input or output.

[0015] It is proposed to design the energy storage device rotationally symmetrical to a longitudinal axis of the rotor shaft in order to avoid the effects of imbalances in the form of the energy storage device.

[0016] It is further proposed to implement the energy storage device in the form of at least one capacitor. It is proposed to arrange the capacitor on the circuit board, which is orthogonal to the longitudinal axis of the rotor shaft.

[0017] The proposed device can be arranged within a hollow shaft section of a rotor shaft of the synchronous machine, wherein the first, stationary section can be arranged entirely and the second, non-stationary section can be arranged at least partially in the hollow shaft section.

[0018] Furthermore, a rotor shaft (claim 12) with the device described above, an electric motor (claim 13) in the form of an inductively electrically excited synchronous machine with a rotor shaft of this type and a vehicle (claim 14) with an electric motor of this type are proposed.

[0019] Furthermore, the use of a device of the type described above in an oil-cooled synchronous machine is proposed, in which an oil penetrates into the device up to the circuit board during operation of the synchronous machine in order to also cool this device.

[0020] Further advantages and features emerge from the subclaims and the exemplary embodiment described below. The sole embodiment shows:

[0021] Fig. 1 a rotor shaft with a proposed external excitation module of inductive type.

[0022] The device 2 shown in Fig. 1 is used for inductive electrical excitation of a rotor of an externally excited synchronous machine for driving a vehicle.

[0023] The proposed device 2 is arranged within a hollow shaft section 6 of a rotor shaft 4, which as such forms the rotor.

[0024] This rotor shaft 4 carries a rotor winding (not shown) [also called coil winding] distributed over its circumference or along its circumference, which is to be excited or magnetized and which forms the rotor.

[0025] When excited or magnetized, this rotor can interact magnetically with a stator of the synchronous machine (not shown) surrounding the rotor, whereby the rotating magnetic field generated by the stator drives the rotor and thus the rotor shaft 4.

[0026] A pot-shaped or cup-shaped receiving body 14, approximately in the form of a deep-drawn sheet, is pressed into this hollow shaft section 6 up to a stop or stop section of the hollow shaft section 6. Within this receiving body and on its base section 16, a printed circuit board 12 (PCB) is mounted, on which a capacitor 10 in the form of a supercapacitor is mounted or provided. This printed circuit board 12 is arranged orthogonally to a longitudinal axis of the rotor shaft 4 and is contacted with the rotor winding (not shown) via a contacting element in the form of a pin 18.

[0027] The supercapacitor 10 is designed to be rotationally symmetrical to the longitudinal axis of the rotor shaft 4 in order to avoid an imbalance in the form of the capacitor and thus the associated vibrations and wear.

[0028] In a region of the open end of the receiving body 14, a transformer 8 is provided, the air gap of which can be arranged or oriented longitudinally or parallel or transversely or orthogonally to the longitudinal axis X - X of the rotor shaft.

[0029] While a first section 8a of the transformer 8 with a first coil winding is arranged on a hollow shaft 22 which is arranged stationary relative to a housing 26 of the synchronous machine and is thereby stationary relative to this hollow shaft 22, a second section 8b of the transformer 8 with a second coil winding is arranged stationary relative to the receiving body 14 and thus stationary relative to the hollow shaft section 6 or to the rotor shaft 4.

[0030] The hollow shaft 22 extends into a receiving section of the housing 26. The first coil winding or the first section 8a of the transformer 8 is electrically contacted via a line 20. The proposed device 2 accordingly has a first, stationary section connected to the housing 26 of the synchronous machine and a second, non-stationary section connected to the housing 26, wherein these two sections are operatively connected or can be operatively connected to one another without contact via the transformer 8, 8a, 8b.

[0031] In this case, a control unit with the circuit board 12 and the supercapacitor 10 is integrated into the second section, which can be switched on if necessary in order to be able to increase or amplify an excitation current provided inductively by the transformer 8 on the rotor side or in this second section accordingly.

[0032] The rotor shaft 4 is supported by two support points on or opposite the housing 26. According to Fig. 1, one of these support points is arranged within the hollow shaft section 6 and is designed in the form of a rolling bearing 24. This rolling bearing 24 is arranged between the hollow shaft section 6 and a receiving section of the housing 26 that projects annularly toward or into the hollow shaft section 6. In the illustrated embodiment, this rolling bearing 24 functions as a floating bearing.

[0033] At the other or opposite end of the rotor shaft 4, in the area of ​​the offset section shown, a further - not shown - rolling bearing is provided, which in the embodiment shown functions as a fixed bearing.

[0034] Furthermore, a rectifier circuit is formed or provided on the circuit board 12, which rectifies the alternating current induced in the second section 8b of the transformer 8 or converts this into a direct current. The contact between the circuit board 12 and the second coil winding of the transformer 8 or the second transformer section 8b is represented in the form of a line section or an electrical line, which extends from the second coil winding of the transformer 8 or the second transformer section 8b to the circuit board 12. The capacitance of the supercapacitor is designed such that it can significantly increase the inductively electrically provided energy, for example by at least a factor of approximately 1.5, but preferably by at least a factor of approximately 2 or 3. This is where the term supercapacitor comes from.

[0035] In one embodiment, a passive capacitor activation circuit can also be implemented or formed on the circuit board 12, via which the supercapacitor 10 is contacted with the second coil winding of the transformer 8 and which as such can be triggered or activated via a definable current threshold, so that from a definable current threshold value, an additional excitation current is generated by the supercapacitor 10, by which an excitation current generated inductively via the transformer 8 increases to a required maximum possible value.

[0036] Alternatively, an active capacitor activation circuit with a microprocessor can be implemented or formed on the circuit board 12. Such an implementation requires a communication interface between the said first, stationary section, or section fixed to the housing 26, and the said second, non-stationary section, or section fixed to the hollow shaft section 6 or the rotor shaft 4, of the proposed device 2. This advantageously opens up the possibility of transmitting rotor state parameters, such as temperature. This could further increase or improve the efficiency of the electric motor.

[0037] Although exemplary embodiments are explained in the foregoing description, it should be noted that numerous modifications are possible. Furthermore, it should be noted that the exemplary embodiments are merely examples and are not intended to limit the scope of protection, applications, or structure in any way. Rather, the foregoing description provides the skilled person with a guide for implementing at least one exemplary embodiment, whereby various modifications, particularly with regard to the function and arrangement of the described components, can be made without departing from the scope of protection as it results from the claims and equivalent combinations of features.

Claims

Patent claims 1. Device (2) for an inductively electrically excited synchronous machine for driving a vehicle, wherein the device (2) has a first, stationary section relative to a housing (26) of the synchronous machine and a second, non-stationary section relative to the housing (26), wherein a transformer (8) with an air gap is arranged between the first and second sections, which transformer transmits the electrical energy in a contactless manner, wherein a control unit with a printed circuit board (12) and an energy store which can be activated as needed for increasing an inductively provided electrical energy is provided in the second section.

2. Device (2) according to claim 1, wherein the device (2) is arranged within a hollow shaft section (6) of a rotor shaft (4) of the synchronous machine, wherein the first, stationary section is arranged entirely and the second, non-stationary section is arranged at least partially in the hollow shaft section (6).

3. Device (2) according to claim 1 or 2, wherein the energy storage device is designed to be rotationally symmetrical to a longitudinal axis of the rotor shaft (4).

4. Device (2) according to one of the preceding claims, wherein the energy storage device is designed in the form of at least one capacitor (10).

5. Device (2) according to claim 4, wherein the capacitor (10) is arranged on the circuit board (12) which is orthogonal to the longitudinal axis of the rotor shaft (4).

6. Device (2) according to one of the preceding claims 2 to 5, wherein the circuit board (12) is mounted within a pot-shaped receiving body (14) and thereby on its bottom section (16), wherein the receiving body (14) is inserted into the hollow shaft section (6).

7. Device (2) according to claim 6, wherein the transformer (8) is provided in a region of the open end of the receiving body (14), wherein the receiving body (14) at least partially encloses the transformer (8).

8. Device (2) according to one of the preceding claims 2 to 7, wherein at least one rolling bearing (24) is also provided within the hollow shaft section (6) for supporting the rotor shaft (4) relative to the housing (26).

9. Device (2) according to one of the preceding claims, wherein the energy storage device is designed such that it increases an inductively provided excitation current by a factor of at least approximately 1.

5.

10. Device (2) according to one of the preceding claims, wherein a passive capacitor activation circuit is formed on the circuit board (12), via which the capacitor (10) is contacted with a second coil winding of the transformer (8) and which as such can be triggered via a definable current intensity threshold, so that from a definable current intensity threshold value an additional excitation current can be generated through the capacitor (10), by which an excitation current generated inductively via the transformer (8) increases to a required greatest possible value.

11. Device (2) according to one of the preceding claims 1 to 9, wherein an active capacitor activation circuit with a microprocessor is formed on the circuit board (12), wherein a communication interface is provided between the first, stationary section and the second, non-stationary section of the device (2).

12. Rotor shaft with a device (2) according to one of the preceding claims.

13. Electric motor in the form of an inductively electrically excited synchronous machine with a rotor shaft according to claim 12.

14. A vehicle having an electric motor according to claim 13.

15. Use of a device (2) according to one of the preceding Claims 1 to 11 in an oil-cooled synchronous machine, in which an oil penetrates into the device up to the printed circuit board (12) during operation of the synchronous machine in order to also cool this device (2).

Images