A method for operating a drive train and a vehicle drive train having an electric drive

Abstract

A vehicle drive train and a method for operating a drive train having an electric drive (4), wherein the rotational speed and the drive torque of the drive (4) are manipulated with a manipulation signal (40), which can be varied via a toothed transmission stage (12) for a driven wheel (19), wherein a periodic torque variation signal (5) is superimposed on the manipulation signal (40), which is in phase with a variation in the stiffness of the teeth of the toothed transmission stage (12), wherein the signal strength of the torque variation signal (5) is smaller in the case of a reduction in the stiffness of the teeth than in the case of an increase in the stiffness of the teeth.

Description

Technical Field

[0001] This invention relates to a method for operating a drive system according to the preamble of claim 1. Furthermore, this invention relates to a vehicle drive system having an electric drive according to the preamble of claim 9.

[0002] In electric vehicle drive systems, the internal combustion engine, as a noise source, is omitted compared to vehicles with internal combustion engines, and is replaced by a significantly quieter electric motor. Consequently, noises that are not noticeable in internal combustion engine drive systems are now also present, as the internal combustion engine or its auxiliary units have masked the noise. This is especially true at low vehicle speeds, where tire rolling noise and wind noise dominate and mask any potential additional noise at high speeds. Background Technology

[0003] DE 10 2015 207 632 A1 relates to an apparatus for reducing gear noise in a drive gear meshing with a driven gear, wherein force can be introduced from the gear via a support into a housing, wherein the apparatus has a sensor device, an adjustment device, and an actuator, and wherein a dynamic vibration signal can be detected by means of the sensor device, and the vibration signal can be transmitted to the adjustment device, wherein a vibration reduction signal can be generated by means of the adjustment device, and the vibration reduction signal can be transmitted to the actuator, wherein the actuator is arranged on or in the support such that force can be transmitted from the gear via the actuator into the housing, wherein the actuator can actively induce relative movement and / or force loading of components supported by the support. The apparatus also includes a means of using the actuator as a sensor device. Summary of the Invention

[0004] The object of the present invention is to provide a method and an apparatus that enable the operation of a drive system, particularly one that operates only electrically.

[0005] The problem upon which this invention is based is solved by a method having the features of claim 1 and a vehicle drive system having the features of claim 9. Advantageous improvements of the invention are given in the dependent claims.

[0006] According to the present invention, a method for operating a drive system having an electric actuator specifies that: the rotational speed and driving torque of the actuator can be varied via a toothed transmission stage for the driven actuator, and the actuator is controlled using a control signal. A periodic torque variation signal is superimposed on the control signal, the periodic torque variation signal alternately decreasing and amplifying the driving torque and being in phase with the tooth stiffness variation of the toothed transmission stage, wherein the signal strength of the torque variation signal is less when the tooth stiffness decreases than when the tooth stiffness increases.

[0007] The advantage of this method is that it generates little to no interfering noise during the rolling of the two transmission gears due to the variable tooth stiffness. This noise will be modulated and increases with increasing torque transmitted through the transmission stage. That is, the tooth stiffness varies periodically on each individual tooth pair just as they are engaged. Therefore, in a simple spur gear stage, the frequency of this variation is the gear's rotational speed multiplied by its number of teeth.

[0008] One advantage of this invention is that it incurs neither additional cost nor weight, and can be implemented purely through software expansion. This software can also be implemented late in the development process, or even later, for example, as a software update for field vehicles. Therefore, the computational resource consumption on the controller is minimal. Only the rotor position and gear position, determined by the structure, are needed as signals, along with an estimate of the torque. The motor torque can be estimated by the field-oriented adjustment unit, and the rotor position is similarly measured or estimated with respect to the field-oriented adjustment unit. Therefore, in principle, no additional sensors are required.

[0009] The method according to the invention can also be used in other drive systems with an electric motor having a transmission mechanism but no internal combustion engine. Such drive systems can be, for example, drive systems from industrial technology or white goods. White goods particularly relate to refrigerators, freezers, etc., whose refrigerant compressors are electrically driven. However, white goods also include washing machines and dishwashers, whose pumps or drums are electrically driven. Furthermore, the drive system according to the invention can also be applied to power tools with transmission mechanisms. Drilling rigs are particularly examples of such power tools with transmission mechanisms. However, for example, chainsaws and grinding machines can also have such drive systems, each with its own transmission mechanism.

[0010] According to one improved design, the control signal is either a torque adjustment signal from the torque regulator or an output voltage signal from the torque regulator. This type of control signal is advantageous in typical electric drives.

[0011] According to one improved design, the output voltage signal or torque regulation signal of the torque regulating unit belongs to a field-oriented torque regulating unit or current regulating unit. By implementing a field-oriented torque regulating unit or current regulating unit, the speed and positioning accuracy of the electric drive are improved using a frequency converter.

[0012] According to one improved scheme, a periodic torque variation signal is superimposed on the control signal based on the torque rating or the rotor position of the drive. This dependence on torque is particularly advantageous because the effect of tooth stiffness variation varies with the torque transmitted by the transmission mechanism. In this respect, the amplitude of the torque variation signal can be matched to the torque variation as needed.

[0013] According to one improved scheme, the periodic torque variation signal has a sinusoidal shape. The sinusoidal signal can be adjusted very easily.

[0014] According to one improved scheme, the periodic torque variation signal has a rectangular shape. Such a rectangular shape can be easily represented digitally.

[0015] To achieve improved noise reduction, periodic torque variation signals can be specified to simulate tooth stiffness and stored in a table or described by a mathematical function.

[0016] Similarly, to improve noise reduction, it can be stipulated that the equivalent value of the periodic torque variation signal is equal to zero.

[0017] For field-oriented torque regulation to function particularly well across the entire speed range, it can be specified that, in order to regulate the drive system by a suitable road segment model and subtract its output signal from the measured signal of the actual road segment, the influence of noise attenuation on the actual road segment can be suppressed for the field-oriented torque regulation of the drive.

[0018] According to the present invention, a vehicle drive system having an electric drive includes:

[0019] The driver has variable driving torque and variable speed.

[0020] A toothed transmission stage, connectable to the driver to convert the rotational speed and the driving torque, is used to control a controller of the driver via a control signal. Here, by means of the controller, a periodic torque variation signal is superimposed on the control signal, this periodic torque variation signal alternately decreasing and amplifying the driving torque and being in phase with the tooth stiffness variation of the toothed transmission stage, wherein the signal strength of the torque variation signal is less when the tooth stiffness decreases than when the tooth stiffness increases.

[0021] To further reduce interference noise, various other design measures can be implemented. For example, the overlap of gear teeth can be increased. Furthermore, the transmission housing can be reinforced. The additional costs associated with housing reinforcement can be reduced through the design scheme according to the invention.

[0022] This invention enables a drivetrain that operates smoothly despite having straight teeth, thus saving the additional costs associated with helical teeth. However, helical teeth can also be used in the drivetrain according to the invention. Compared to straight teeth, helical teeth achieve better smoothness and lower noise generation because each tooth pair engages and disengages in a continuous transition. Consequently, torque is transmitted more evenly than in the case of straight teeth.

[0023] Both the method and the apparatus described can be applied to vehicle drive systems that operate only electrically. That is, the transmission stage cannot be connected to an internal combustion engine. Attached Figure Description

[0024] Possible embodiments of the present invention will now be explained with reference to the accompanying drawings.

[0025] Figure 1 A vehicle drive system is shown, which has a driver and an associated controller with noise attenuation.

[0026] Figure 2 The block diagram illustrates the integration of the noise attenuation unit into... Figure 1 In the vehicle drive system, the torque change signal is simulated in steady state;

[0027] Figure 3 Another embodiment is illustrated with a block diagram, in which the integration of the noise attenuation section is performed as a superposition on the stator voltage rating of the inverter for the driver;

[0028] Figure 4 Another embodiment is illustrated with a block diagram, wherein the integration of the noise attenuation section is performed as a superposition of a periodic torque variation signal onto the torque rating; and

[0029] Figure 5 Another embodiment is illustrated with a block diagram, in which the integration of the noise attenuation section is performed as a superposition on the voltage rating of the pulse inverter for the driver. Detailed Implementation

[0030] Figure 1The vehicle drive system 2 of an electric motor vehicle is schematically shown. The electric motor vehicle does not have an internal combustion engine drive and, for this purpose, only has an electric drive 4. The drive 4 is specifically implemented as a converter-guided synchronous motor. Depending on the type of motor vehicle, the electric drive 4 can also be implemented as a DC motor or a converter-guided asynchronous motor. Another alternative to the drive 4 is a switched reluctance mechanism, also known as a "switched reluctance motor," or SRM for short. Furthermore, a transverse flow motor can be used as the drive 4.

[0031] The driving torque and speed of the drive 4 are variable by means of a controller 6, which is configured to operate the drive 4.

[0032] The output shaft 8 of the drive unit 4, rotatably supported by rolling bearings 7, is connected in a non-rotating manner to the first gear 10 of a toothed transmission stage 12, which is arranged within a transmission housing 13. The first gear 10 meshes with a second gear 14 of the transmission stage 12. The second gear 14 is connected via a differential to two drive shafts 16, which are supported in rolling bearings 17 and connected in a non-rotating manner to wheels 18.

[0033] The diameter of the first gear 10 is smaller than that of the second gear 14, thus forming a pinion. The rotational speed and driving torque of the driver 4 are converted via a toothed transmission stage 12 for the driven 19 having a drive shaft 16. By means of the transmission stage 12, the rotational speed of the driver 4 is converted into a lower transmission-output speed, and the driving torque is converted into a higher transmission-output torque. In this respect, a driver 4 can be used that has a relatively high maximum speed but excessively low torque.

[0034] The second gear 14 includes a differential that distributes the transmission output torque evenly to the two wheels 18.

[0035] Alternatively, transmission stage 12 may be implemented as a planetary gear transmission mechanism and / or as a switchable transmission mechanism with multiple stages, especially two stages, having different transmission ratios. Vehicle drive system 2 may also be implemented as a hub motor that drives only a single wheel 18.

[0036] Gears 10 and 12 are either spur or helical. The teeth 20 and 22 of gears 10 and 12 mesh with each other regardless of their orientation. The system consisting of two meshing gears 10 and 12 with variable tooth stiffness forms a bimass oscillator with a variable spring constant.

[0037] The first gear 10 has a first inertia and the second gear 12 has a second inertia. Therefore, the two gears 10 and 12 form a dual-mass oscillator that vibrates at a variable frequency related to the rotation path, i.e., the gear meshing frequency.

[0038] The variable tooth stiffness of the teeth excites vibrations on the meshing gears 10 and 12 during rotation. These vibrations are transmitted through gears 10 and 12, shafts 8 and 16, and rolling bearings 7 and 17 to the transmission housing 13, where they are radiated as noise by the vibrating surfaces. In addition to rotational vibrations, gears 10 and 12 also vibrate translationally relative to the transmission housing 13 using bearings 7 and 17, thereby generating noise. Here, the transmission housing 13 is excited into translational vibrations via bearings 7 and 17, causing sound waves to propagate in the air as fluctuations in pressure and density. The variable tooth meshing force engages at the intersection of the two gears 10 and 12 and acts tangentially on the respective gear 10 or 12. This force must be supported via the corresponding bearing 7 or 17.

[0039] The controller 6 features imprint-based regulation, which involves superimposing periodic additional torque vibrations onto the electric drive 4 to attenuate undesirable noise with gear meshing frequencies during the operation of the electric vehicle. For this purpose, a periodic torque variation signal is superimposed with the control signal of the drive 4. The periodic torque variation signal alternately decreases and amplifies the driving torque. Here, the periodic torque variation signal is phased with the tooth stiffness of the transmission stage 12 switched in the force flow. The control signal can be, in particular, a torque adjustment signal or an output voltage signal from a torque adjustment unit. The torque adjustment unit can be, in particular, field-oriented, i.e., vector regulation. Through field-oriented regulation, the speed and positioning accuracy are improved using a frequency converter located in the controller 6.

[0040] Ideally, this torque variation signal has no DC component or a zero DC component. The torque variation signal increases or decreases the transmitted total torque, which is adjusted at the driver 4 due to the torque adjustment signal and the drive control signal. Here, the tooth stiffness of the teeth 20 and 22 currently in mesh determines whether the total torque increases or decreases. Therefore, on average, the output torque requested by the driver and adjusted by the parallel-operating torque adjustment unit remains unchanged. The periodic torque variation signal can simulate a precise curve of torque fluctuations or, for example, be approximated by a sinusoidal signal with the same phase and frequency.

[0041] Because the effect of gear stiffness variation varies with the transmission output torque required by the driver, the amplitude, i.e. the signal strength of the torque adjustment signal, must accordingly match the required transmission output torque.

[0042] The following section details the adjustment using controller 6 based on the parameters of the adjustment technology.

[0043] By applying a periodic steady-state torque rating—or voltage rating signal—to the output signal of, for example, a field-oriented torque—or current regulator, transmission noise is attenuated at the gear meshing frequency. Stiffness variations along the rotational path act like vibration excitation on a dual-mass oscillator under constant torque. That is, the teeth meshing with each other are excited to vibrate relative to each other. Now, the modulation of the torque of driver 4 reacts to this excitation. Therefore, when the tooth stiffness decreases, the signal strength of the drive control signal decreases slightly. Conversely, the signal strength of the drive control signal increases slightly when the tooth stiffness increases.

[0044] exist Figure 2 The first embodiment of the method is illustrated in the block diagram. The torque variation signal 5 is simulated in a steady state. There is no feedback adjustment parameter, so in this example it is a control unit. The input parameters are the torque 23 and the rotor position 24 of the driver. An offset position 26 is added to the rotor position 24. The number of teeth 30 of the gear is input to the control unit. The torque 23, as an input parameter, can be represented in the model by the transfer function 32 of the rotation amplitude. The main determining parameter of the steady-state torque variation signal is the sine function 33. The output parameter is the torque variation signal 5 used to dampen vibration.

[0045] Figure 3 The integration of the noise attenuation unit 34 is shown in the second embodiment as a connection to the stator voltage rating 40 of the controller for the driver 4, which is implemented as an inverter. Here, a two-dimensional table is used instead of a sine function, which outputs the matched torque rating 36 of the driver with respect to rotor position and torque. Different periodic signals can be considered for this purpose. Preferably, a rectangular function or a sine function stored in tabular form is used. Both sine and rectangular functions are easy to implement. However, alternatively, the tooth stiffness can be simulated as accurately as possible and stored in a table. Alternatively, the tooth stiffness can be approximated by a function. Therefore, the noise attenuation unit 34 can be integrated into the existing field-oriented torque regulation unit 38 or current regulation unit. Figure 3 As shown in the image.

[0046] The rated torque 36 is input as an input parameter to the field-oriented torque regulating unit 38. The rated stator voltage 40 is output as an output parameter by the field-oriented torque regulating unit 38; in this respect, the rated stator voltage is the control signal of the driver 4. The rated stator voltage 40 is added together with the torque change signal 5, which is the output value of the noise attenuation unit 34, at the summing node 41. The result of this summation is sent to the electric driver 4 as an input value, which can be described by means of a transfer function for modeling. The electric driver 4 has a driving torque 44. Gear meshing acts on this driving torque 44 as an interference parameter 46. The frequency of the vibration excitation of the meshing gears of the transmission stage can be described in the model by the transfer function 48. The output parameter of the transfer function 48 is the output signal of the mechanical system, which can be, in particular, the speed 50 of the electric vehicle or the surface speed of the transmission stage. Furthermore, the output signal of the mechanical system is the input parameter of the noise attenuation unit 34.

[0047] From Figure 4 A third embodiment is shown, which is a further development of the second embodiment. The noise attenuation unit 34 is integrated into the controller by summing the periodic torque variation signal 5 to the torque rating 36. The rotor position and torque ratings are used as input values. (Compared to...) Figure 3 Unlike the second embodiment, the torque variation signal 5 output by the noise attenuation unit 34, together with the torque rating 36, is guided to the summing node 52, the output value of which forms the input value of the field-oriented torque adjustment unit 38. This prevents the field-oriented torque adjustment unit 38 from re-tuning the signal of the noise attenuation unit 34, since vibrations in speed or torque are interferences for the field-oriented torque adjustment unit 38. If the effect of the noise attenuation unit 34 on the speed signal is simulated using a model and subtracted from the measured value used by the field-oriented torque adjustment unit 38, then the field-oriented torque adjustment unit 38 does not consider the noise attenuation unit 34 as an interference parameter and tunes it. This tuning is especially important at low speeds, as the dynamics of the field-oriented torque adjustment unit 38 are sufficient for tuning in this case. Furthermore, unlike the second embodiment, no summing node is provided between the field-oriented torque adjustment unit 38 and the driver 4.

[0048] Figure 5 A fourth embodiment is shown, which is also a further development relative to the second embodiment. The noise attenuation unit 34 is integrated into the controller of the driver 4.

[0049] The noise attenuation unit 34 superimposes the torque change signal 5 onto the stator voltage rating 40 used in the pulse inverter 53. The rotor position and torque value of the field-oriented torque adjustment unit 38 are used again as input parameters.

[0050] Unlike the second and third embodiments, the output signal of the field-oriented torque regulation unit 38 is directly supplied to the noise attenuation unit 34. Furthermore, unlike the second embodiment, the voltage 55 applied to the driver 4 is intercepted and fed back to another summing node 54, where the voltage 55 is summed with the rated current intensity 56 of the driver 4. The result of this summation is then directed as an input value to the field-oriented torque regulation unit 38. The pulse inverter 53 obtains the sum of the rated stator voltage 40 and the torque variation signal 5 of the noise attenuation unit 34 from the summing node 41 as an input value. The pulse inverter 53 controls the driver 4.

[0051] The method for operating a vehicle drive system shown above can be implemented as part of an axle system or as a software option with a pulse inverter or controller, and in this regard constitutes a vehicle component.

Claims

1. Method for operating a drive train with an electric drive (4), wherein the rotational speed and the drive torque of the drive (4) can be varied via a toothed transmission stage (12) for a driven machine (19), and the drive (4) is operated with an operating signal (40), characterized in that a periodic torque variation signal (5) is superimposed on the operating signal (40), which alternately reduces and increases the drive torque and is in phase here with a variation in the stiffness of the teeth of the toothed transmission stage (12), wherein the signal strength of the torque variation signal (5) is smaller in the case of a reduction in the stiffness of the teeth than in the case of an increase in the stiffness of the teeth, wherein the periodic torque variation signal (5) models the stiffness of the teeth and is stored in a table or described by a mathematical function. The operating signal (40) is a torque regulation signal of a torque regulation (38) or an output voltage signal of a torque regulation (38). The output voltage signal of the torque regulation or the torque regulation signal belongs to a field-oriented torque regulation (38) or a current regulation.

2. The method of claim 1, wherein, The periodic torque variation signal (5) is superimposed on the operating signal (40) depending on a torque rating (36) of the drive (4) or a rotor position (24).

3. The method of claim 2, wherein, The periodic torque variation signal (5) has a sinusoidal shape.

4. The method according to any one of claims 1 to 3, characterized in that, The periodic torque variation signal (5) has a rectangular shape.

5. The method according to any of the preceding claims, characterized in that, The equivalent of the periodic torque variation signal (5) is equal to zero.

6. The method according to any one of claims 1 to 4, characterized in that, Drive (4), the drive torque and the rotational speed of which are variable, toothed transmission stage (12), which can be coupled to the drive (4) to convert the rotational speed and the drive torque, controller (6) for operating the drive (4) with an operating signal (40), characterized in that a periodic torque variation signal (5) can be superimposed on the operating signal (40) by means of the controller (6), which alternately reduces and increases the drive torque and is in phase here with a variation in the stiffness of the teeth of the toothed transmission stage (12), and the signal strength of the torque variation signal (5) is smaller in the case of a reduction in the stiffness of the teeth than in the case of an increase in the stiffness of the teeth, wherein the periodic torque variation signal (5) models the stiffness of the teeth and is stored in a table or described by a mathematical function.

7. The method according to any of the preceding claims, characterized in that, The operating signal (40) is a torque regulation signal of a torque regulation (38) or an output voltage signal of a torque regulation (38).

8. A vehicle drive train having an electrically powered drive, comprising: ​ 9. The vehicle drive line of claim 8, wherein, ​

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