Method for pre-heating a bearing which comprises a temperature-dependent lubricant, computer program and / or computer-readable medium, controller, electric drive, turbomachine, and vehicle, in particular utility vehicle

Abstract

The invention relates to a method (100) for pre-heating (Q) a bearing (20), which comprises a temperature-dependent lubricant (25), of an electric drive (15) with a rotor (16), which is designed for an electromagnetic induction (L), and a stator (17) for a turbomachine (11) for a vehicle (10a), in particular a utility vehicle (10b), wherein the bearing (20) can be heated together with the rotor (16) and / or the stator (17), and the bearing (20) is designed to rotatably support the rotor (16). The method (100) has the steps of: detecting (110) a rest state (R) of the rotor (16); and applying (120) an electric alternating current (I) to the rotor (16) and / or stator (17) in the rest state (R) in order to heat (Q') the electric drive (15), said alternating current (I) having a specified frequency (F) such that the rotor (16) remains in the rest state (R).

Description

[0001] Method for preheating a bearing comprising a temperature-dependent lubricant, computer program and / or computer-readable medium, control device, electric drive, turbomachine, vehicle, in particular commercial vehicle

[0002] The invention relates to a method for preheating a bearing comprising a temperature-dependent lubricant of an electric drive, each having a rotor and stator configured for electromagnetic induction, for a turbomachine for a vehicle, in particular a commercial vehicle. The bearing can be heated together with the rotor and / or the stator, and the bearing is configured for rotatably supporting the rotor. The invention also relates to a computer program and / or a computer-readable medium, a control unit, an electric drive, a turbomachine, and a vehicle, in particular a commercial vehicle.

[0003] The invention particularly relates to a cold start of a turbomachine, for example, a compressor and / or expander. The turbomachine is electrically driven and / or comprises a rotor and stator each configured for electromagnetic induction, wherein the electromagnetic induction occurs by applying an electric current to the rotor and / or stator in order to generate a torque and drive the turbomachine.

[0004] It is known that the bearing must reach a predetermined temperature determined by the lubricant for the turbomachine to operate properly. Below the predetermined temperature, the lubricant may exhibit high viscosity and / or be in a non-liquid state, making operation of the turbomachine difficult or even impossible.

[0005] For example, an oil-free, two-stage compressor comprises a plurality of bearings. The bearings contain grease as a lubricant. At temperatures below -40°C, for example, the viscosity of the lubricant increases significantly and friction within the bearing increases. Therefore, a comparatively high torque provided by an electric drive is required to start the compressor. The electric motor can be dimensioned accordingly. However, this is inefficient and cost-effective, as the motor would have to be specifically designed and dimensioned for starting at low temperatures, whereas a different design and dimensioning is advantageous for normal operation.

[0006] Alternatively, it is known from the prior art to preheat a bearing by applying a direct current to the electric drive. This induces ohmic losses in the form of heat and heats the lubricant in the bearing, thus providing a lower viscosity compared to the cold lubricant. However, a direct current leads to a loss density in the windings of the rotor and / or stator that requires improvement. The heating is quite slow and / or occurs in a relatively localized manner, which can lead to insufficient heat transfer from the windings to the bearing.

[0007] DE 10 2015 000 134 T5 discloses an electric compressor and a method for controlling the same. The electric compressor includes a detection unit for detecting a phase of a refrigerant in the electric compressor, a connection unit wound at a position adjacent to a passage of a housing for moving a refrigerant in the electric compressor, and a control unit for performing control according to the phase of the refrigerant by differentially controlling a power applied to the connection unit in response to data detected by the detection unit.The method includes aligning a position of a rotor after an electric compressor is switched on, determining whether a refrigerant is in a liquid phase or a gas phase, preheating the refrigerant by applying power to the electric compressor according to the phase of the refrigerant, and controlling the electric compressor so that the electric compressor operates normally after the refrigerant is preheated. The invention is therefore based on the object of enriching the prior art and creating an improved possibility for preheating a bearing with a temperature-dependent lubricant. In particular, the object can be to achieve the most effective possible preheating of a bearing of an electric drive of a turbomachine.

[0008] This object is achieved by a method according to claim 1 and the subject matter according to the further independent claims. The subclaims specify preferred developments of the invention.

[0009] According to the invention, a method is provided for preheating a bearing comprising a temperature-dependent lubricant of an electric drive, each having a rotor and stator configured for electromagnetic induction, for a turbomachine for a vehicle, in particular a commercial vehicle, wherein the bearing can be heated together with the rotor and / or the stator, and the bearing is configured for rotatably supporting the rotor. The method comprises: detecting a rest state of the rotor; and applying, in the rest state, to the rotor and / or stator an alternating electrical current to heat the electric drive, wherein the alternating current has a predetermined frequency such that the rotor remains in the rest state.

[0010] The bearing is a machine element of the electric drive for the rotatable support of the rotor. The rotor comprises a shaft that is rotatably mounted by means of the bearing. The lubricant is provided to improve the properties of the bearing, for example, reducing friction and increasing the bearing's operational strength. The lubricant can, for example, comprise a non-Newtonian fluid and / or a dispersion, which can lead to a temperature dependence of the lubricant. In particular, the composition and / or application of the lubricant can result in a temperature below which effective operation of the bearing is not ensured.

[0011] The bearing can be heated together with the rotor and / or stator. In other words, heat can be transferred from the bearing to the rotor and / or stator, or from the rotor and / or stator to the bearing. Thus, heating of the rotor and / or stator causes heating of the bearing. This allows heat to be transferred from the rotor and / or stator to the bearing to heat the lubricant.

[0012] It was recognized that, especially with a stationary rotor, there is a possibility that the bearing or its lubricant may be in a condition that prevents effective operation of the bearing because the temperature of the lubricant is too low. Therefore, a stationary state of the rotor is detected to determine that the rotor is not rotating, i.e., that the rotor's angular velocity is zero. Before the electric drive can be operated, the lubricant or bearing is heated, i.e., the bearing is preheated.

[0013] According to the invention, an alternating current is used to heat the electric drive in the idle state. The alternating current can be applied to the rotor and / or the stator. It has been recognized that alternating current enables significantly better heating of the rotor and / or the stator than direct current. The alternating current not only leads to ohmic losses in the windings of the stator and / or rotor, but also to inductive losses or general remagnetization losses, which cause heat input into the stator and / or the rotor.

[0014] The alternating current has a predetermined frequency. The frequency is determined in particular by the geometry and / or the electromagnetic properties of the rotor and / or the stator. With regard to the geometry and / or the electromagnetic properties, the frequency is determined such that the frequency is low enough to achieve sufficient inductive losses for preheating and high enough to prevent vibrations of the electric drive and / or rotation of the rotor.

[0015] For example, frequencies in the range from 500 Hz to 100 kHz are suitable for this. Preferably, an alternating current intensity and / or the predetermined frequency are dependent on a temperature of the electric drive. The temperature of the electric drive can provide information about the temperature of the bearing and / or the lubricant. In particular, the temperature of the electric drive can be a temperature that characterizes a winding of the rotor and / or the stator. By means of an estimate and / or a thermal model of the electric drive, the temperature of the bearing can be deduced from the temperature of the winding. For example, the current intensity can be selected to be higher if the desired temperature increase is greater than if the desired temperature increase is smaller.The current intensity can be set to zero above a first temperature threshold, which means that the application of an alternating current can be omitted, since it can be assumed that the temperature of the lubricant is high enough to ensure effective operation of the electric machine. The frequency can be designed with regard to the geometry and / or electromagnetic properties to impose the power loss on specific sections of the rotor and / or stator, for example, to promote heat transfer to the bearing.

[0016] Preferably, the application of current results in a drive torque, and the drive torque is less than the starting torque of the electric drive. It was recognized that a starting torque is caused by possible solidification of the lubricant. The starting torque is a threshold value for the torque applied to the rotor, whereby the rotor remains at rest at a torque below the starting torque and is set in rotation at a torque above the starting torque. A drive torque can be caused by the application of alternating current. However, the drive torque does not lead to rotation of the rotor if the drive torque is less than the starting torque. In this case, all of the energy applied by the electric current is converted into heat, and the rotor does not rotate.

[0017] Preferably, the method comprises: detecting a temperature relating to the electric drive; and determining a period of time for applying the alternating electric current to the electric drive, taking into account the detected temperature. The temperature can, for example, be measured via a

[0018] Temperature sensors can be used to detect this. For example, the electric drive has a temperature sensor for measuring the temperature of the windings of the rotor and / or stator. Based on estimates and / or model calculations, a period of time can be determined within which the electric drive needs to be supplied with alternating current in order to heat the bearing lubricant to such an extent that effective operation of the electric drive is possible.

[0019] The method preferably comprises: terminating the application depending on a measured and / or calculated temperature of the electric drive. This ensures that the temperature does not exceed a critical temperature. For example, it is to be avoided that the temperatures of the stator and / or the rotor exceed a Curie temperature of a magnetic material of the rotor and / or the stator. Furthermore, the application can be terminated when the temperature of the electric drive has exceeded a second temperature threshold, since it can be assumed that at a temperature above the second temperature threshold, sufficient heat could already have been transported from the rotor and / or stator to the bearing.

[0020] According to a further aspect of the invention, a computer program and / or computer-readable medium is provided. The computer program and / or computer-readable medium comprises instructions that, when executed by a computer, cause the computer to perform the method described here and / or the steps of the method described here. The computer program and / or computer-readable medium may comprise instructions to perform steps of the method described as optional and / or advantageous in order to achieve a corresponding technical effect.

[0021] According to a further aspect of the invention, a control unit for a turbomachine for a vehicle, in particular a commercial vehicle, is provided. The control unit is configured to carry out the method described here. The control unit can be configured to carry out steps of the method described as optional and / or advantageous in order to achieve a corresponding technical effect.

[0022] According to a further aspect of the invention, an electric drive for a turbomachine for a vehicle, in particular a commercial vehicle, is provided. The electric drive comprises a rotor and a stator each configured for electromagnetic induction, a bearing comprising a temperature-dependent lubricant for supporting the rotor, wherein the bearing can be heated together with the rotor and / or the stator, and wherein the bearing is configured for rotatably supporting the rotor, and a control unit described herein. The control unit is configured to carry out the method described herein. The control unit can be configured to carry out steps of the method described as optional and / or advantageous in order to achieve a corresponding technical effect.

[0023] According to a further aspect of the invention, a turbomachine for a vehicle, in particular a commercial vehicle, is provided. The turbomachine has the electric drive described here with the control unit. The control unit can be configured to carry out steps of the method described as optional and / or advantageous in order to achieve a corresponding technical effect.

[0024] According to a further aspect of the invention, a vehicle, in particular a commercial vehicle, is provided. The vehicle has the turbomachine described here with the electric drive and the control unit. The control unit can be configured to carry out steps of the method described as optional and / or advantageous in order to achieve a corresponding technical effect.

[0025] Preferably, the vehicle comprises a heat transfer arrangement for heating the bearing together with the rotor and / or the stator of the electric drive. Further advantages and features of the invention as well as their technical effects emerge from the figures and the description of the preferred embodiments shown in the figures.

[0026] Fig. 1 is a schematic representation of an overview of a vehicle, in particular a commercial vehicle, according to one embodiment of the invention; and Fig. 2 is a schematic representation of an overview of a vehicle, in particular a commercial vehicle, according to a further embodiment of the invention; and

[0027] Fig. 3 is a schematic representation of a flow chart of a method according to an embodiment of the invention.

[0028] Figure 1 shows a schematic representation of an overview of a vehicle 10a, in particular a commercial vehicle 10b, according to an embodiment of the invention.

[0029] The vehicle 10a, in particular the commercial vehicle 10b, is referred to below as the vehicle 10a, 10b. The vehicle 10a, 10b is a land vehicle and, for example, a truck, a bus, a trailer, and / or a multi-unit vehicle.

[0030] The vehicle 10a, 10b is configured to perform the method 100 described with reference to Figure 3. For this purpose, the vehicle 10a, 10b has a turbomachine 11 in the embodiment shown in Figure 1.

[0031] The turbomachine 11 is, for example, a compressor for a pneumatic braking system of the vehicle 10a, 10b. For example, the turbomachine 11 is a scroll compressor.

[0032] The turbomachine 11 comprises one or more impellers (not shown) mounted on a rotatable shaft 18 for rotationally fixed connection to the shaft 18, for compressing air introduced into the turbomachine 11. In particular, the turbomachine 11 can be two-stage, with compressed air being passed from one stage to another for further compression. To drive the impellers, the turbomachine 11 comprises an electric drive 15. The electric drive 15 comprises a rotor 16 and a stator 17 each configured for electromagnetic induction L.

[0033] The rotor 16 is rotatably mounted about a rotational axis defined by the shaft 18. For this purpose, the electric drive 15 has a bearing 20 for rotatably supporting the rotor 16. The bearing 20 is, for example, a rolling bearing or a plain bearing. One bearing 20 is shown in each of the schematic Figures 1 and 2. In other embodiments (not shown), the electric drive 15 has multiple bearings 20 for rotatably supporting the rotor 16. This can improve the support of the rotor 16 and / or increase the operational stability of the electric drive 15.

[0034] The bearing 20 includes a temperature-dependent lubricant 25 for lubricating mutually rotatable components (not shown) of the bearing 20. The lubricant 25 is, for example, a grease. The lubricant 25 is temperature-dependent. Below a temperature determined by the lubricant 25, in a range of, for example, -40°C to -25°C, the lubricant 25 can largely solidify and / or assume such a high viscosity that rotation of the rotor 16 by the electric drive 15 is impossible or only possible with difficulty.

[0035] To enable induction L to occur between the rotor 16 and the stator 17, the rotor 16 and the stator 17 each have one or more laminated cores and windings wound around the laminated core(s) (not shown). The windings comprise, for example, a lacquered and / or coated copper wire. Applying an electric current to the windings induces a magnetic field, and a magnetic field causes an electric current.

[0036] The electric drive 15 has a control unit 14. The control unit 14 is configured to carry out the steps of the method 100 described with reference to Figure 3. For this purpose, the control unit 14 has a processor 31 and a memory 32. The processor 31 is configured to process input information and / or information stored in the memory. The control unit 14 is configured to determine a rest state R of the rotor 16. For this purpose, the control unit 14 is connected to a speed sensor 36. The speed sensor 36 is configured to measure a speed and / or angular velocity of the rotor 16 and / or the shaft 18. Alternatively, the control unit 14 can be connected to a position sensor (not shown). This allows an angular position of the rotor 16 and / or the shaft 18 at a standstill to be identified in order to be able to specifically determine a frequency F.

[0037] The control unit 14 is configured to detect a temperature T of the electric drive 15. For this purpose, the control unit 14 is connected to a temperature sensor 35. The temperature sensor 35 is configured, for example, to measure the temperature T of a winding of the rotor 16 and / or the stator 17.

[0038] The control unit 14 is configured to apply an alternating current I to the rotor 16. For this purpose, the control unit 14 comprises appropriate power electronics or an inverter. The control unit 14 uses pulse width modulation (PWM) control to apply the alternating current I to the rotor 16. At a suitable frequency F of the alternating current I, the rotor 16 can be set in rotation to drive the shaft 18.

[0039] The control unit 14 is configured to supply the rotor 16, in the rest state R, with an alternating electrical current I to heat Q' the electric drive 15, wherein the alternating current I has a predetermined frequency F such that the rotor 16 remains in the rest state R. In the process, ohmic and inductive losses are induced in the stator 17 and in the rotor 16. The losses in the stator 17 and in the rotor 16 result in heating Q' of the electric drive 15, and in particular of the stator 17 and the rotor 16. The heat can, for example, be transported from the stator 17 via housing components of the electric drive 15 to the bearing 20 and heat the bearing 20 and the lubricant 25. In addition, heat is transported from the rotor 16 via the shaft 18 to the bearing 20 to heat Q' the bearing 20 and thus the lubricant 25. This allows preheating Q of the bearing 20 to take place without inducing rotation of the rotor 16.The control unit 14 is configured to apply the alternating current I to the rotor 16 with a current intensity IA over a period of time t.

[0040] Figure 2 shows a schematic representation of an overview of a vehicle 10a, in particular a commercial vehicle 10b, according to another embodiment of the invention. Figure 2 is described with reference to Figure 1 and its description. The differences between the embodiments of Figures 1 and 2 are described.

[0041] The vehicle 10a, 10b according to Figure 2 has a heat transfer arrangement 12. During normal operation, the heat transfer arrangement 12 can be configured as a cooling arrangement to jointly cool the stator 17, the rotor 16, and the bearing 12 during operation. For this purpose, the heat transfer arrangement 12 can comprise a conduit arrangement and a heat transfer fluid movable within the conduit arrangement. The heat transfer arrangement 12 is configured to transport heat from the bearing 20 to the rotor 16 and to the stator 17, or from the rotor 16 and / or the stator 17 to the bearing 20.

[0042] Figure 3 shows a schematic representation of a flow chart of a method 100 according to an embodiment of the invention. The method 100 is a method 100 for preheating Q a bearing 20 comprising a temperature-dependent lubricant 25 of an electric drive 15, each having a rotor 16 and stator 17 configured for electromagnetic induction L, for a turbomachine 11 for a vehicle a, in particular a commercial vehicle 10b, wherein the bearing 20 can be heated together with the rotor 16 and / or the stator 17. Such a vehicle 10a, 10b is shown in Figures 1 and 2. Figure 3 is described with reference to Figures 1 and 2.

[0043] The method 100 includes detecting 110 a rest state R of the rotor 16. For this purpose, for example, a rotational speed of the rotor 16 is detected.

[0044] In the rest state R, the rotor 16 and / or stator 17 is supplied 120 with an alternating electrical current I to heat Q' the electric drive 15. The alternating current I has a predetermined frequency F such that the rotor 16 remains in the rest state R. A current intensity IA of the alternating current I and the predetermined frequency F are dependent on a temperature T of the electric drive 15. The current intensity IA and the frequency F influence the energy of an electromagnetic field induced by induction L.

[0045] The application 120 requires a drive torque M1, and the drive torque M1 is smaller than a starting torque M2 of the electric drive 15. Thus, the rotor 16 remains in the rest state R. The starting torque M2 results from the viscosity of the lubricant 25 and the specific geometry and nature of the electric drive 15.

[0046] A temperature T relating to the electric drive 15 is detected 130. For this purpose, the temperature T of the electric drive 15 is measured by means of the temperature sensor 35.

[0047] A period of time t for applying the alternating electrical current I to the electric drive 15 is determined 140, taking into account the detected temperature T. The determination 140 is performed by estimation and / or by computer-assisted evaluation of a model. The model can be a thermal model that models the energy balance of the electric drive 15 and / or its components.

[0048] The application 120 is terminated 150 depending on a measured and / or calculated temperature T of the electric drive 15. When the lubricant 25 is sufficiently heated, the application 120 is terminated. Whether the lubricant 25 is sufficiently heated can be determined by a temperature measurement and / or by the thermal model.

[0049] The person skilled in the art will recognize that steps of the method 100 may deviate from the order shown in Figure 2. Steps of the method 100 may be carried out simultaneously, i.e. at least partially at the same time, and / or in a different order. For example, the detection 130 of the temperature ? relating to the electric drive 15 may take place at any time, i.e. continuously. The determination 140 of the time period t may take place at any time before the termination 150 of the application 120 and after the detection of the temperature T. In particular, the detection 130 of the temperature ? relating to the electric drive 15

[0050] Temperature T and / or determining 140 the period t before applying 120 in order to induce a well-defined amount of heat and introduce it into the bearing 20.

[0051] Reference symbol (part of the description):

[0052] 10a Vehicle

[0053] 10b Commercial vehicle

[0054] 11 Turbomachine

[0055] 12 Heat transfer arrangement

[0056] 14 Control unit

[0057] 15 electric drive

[0058] 16 Rotor

[0059] 17 Stator

[0060] 18 Wave

[0061] 20 warehouses

[0062] 25 Lubricant

[0063] 31 processors

[0064] 32 memory

[0065] 35 Temperature sensor

[0066] 36 Speed ​​sensor

[0067] 100 procedures

[0068] 110 Detecting a sleep state

[0069] 120 Apply

[0070] 130 Recording a temperature

[0071] 140 Investigate

[0072] 150 Exit

[0073] F Frequency

[0074] I alternating current

[0075] IA current

[0076] L Induction

[0077] M1 drive torque

[0078] M2 starting torque

[0079] Q Preheating

[0080] Q' Heating

[0081] R Rest state t Period

[0082] T Temperature

Claims

Patent claims:

1. A method (100) for preheating (Q) a bearing (20) comprising a temperature-dependent lubricant (25) of an electric drive (15) with a rotor (16) and stator (17) each configured for electromagnetic induction (L) for a turbomachine (11) for a vehicle (10a), in particular a commercial vehicle (10b), wherein the bearing (20) can be heated together with the rotor (16) and / or the stator (17), and the bearing (20) is configured for rotatable mounting of the rotor (16), the method (100) comprising: - detecting (110) a rest state (R) of the rotor (16); and - applying (120), in the rest state (R), the rotor (16) and / or stator (17) with an alternating electrical current (I) for heating (Q') the electric drive (15), wherein the alternating current (I) has a predetermined frequency (F) such that the rotor (16) remains in the rest state (R).

2. Method according to claim 1, wherein a current intensity (IA) of the alternating current (I) and / or the predetermined frequency (F) is dependent on a temperature (T) of the electric drive (15).

3. Method according to claim 1 or 2, wherein the application (120) causes a drive torque (M1), and the drive torque (M1) is smaller than a starting torque (M2) of the electric drive (15).

4. Method according to one of the preceding claims, wherein the method (100) comprises: - detecting (130) a temperature (T) relating to the electric drive (15); and - Determining (140) a period of time (t) for applying (120) the electric drive (15) with the alternating electric current (I) taking into account the detected temperature (T).

5. Method according to one of the preceding claims, wherein the method (100) comprises: - Terminating (150) the application (120) depending on a measured and / or calculated temperature (T) of the electric drive (15).

6. Computer program and / or computer-readable medium comprising instructions which, when the program or instructions are executed by a computer, cause the computer to carry out the method (100) and / or the steps of the method (100) according to one of the preceding claims.

7. Control unit (14) for a vehicle (10a), in particular a commercial vehicle (10b), wherein the control unit (14) is configured to carry out the method (100) according to one of claims 1 to 5.

8. Electric drive (15) for a turbomachine (11) for a vehicle (10a), in particular a commercial vehicle (10b), comprising: - a rotor (16) and a stator (17) each designed for electromagnetic induction (L), - a bearing (20) comprising a temperature-dependent lubricant (25) for supporting the rotor (16), wherein the bearing (20) can be heated together with the rotor (16) and / or the stator (17), and wherein the bearing (20) is designed for the rotatable support of the rotor (16), and - a control device (14) according to claim 7.

9. Turbomachine (11) for a vehicle (10a), in particular a commercial vehicle (10b), comprising an electric drive (15) according to claim 8.

10. Vehicle (10a), in particular commercial vehicle (10b), comprising a turbomachine (11) according to claim 9.

11. Vehicle (10a), in particular commercial vehicle (10b) according to claim 10, comprising a heat transfer arrangement (12) for heating (Q') the bearing (20) together with the rotor (16) and / or the stator (17) of the electric drive

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