DE102014208384A1 - A power train and method for reducing a meshing noise of an electrically driveable powertrain having a gear transmission - Google Patents

Abstract

A drive train and a method for reducing gear meshing noise in an electrically drivable drive train (10) with a gear transmission (2) and an electric motor (1) are proposed. The method comprises the following steps: - determining an operating state of the drive train (10), - reading out a data record assigned to the determined operating state from a data memory (3), and - adjusting a torque of the electric motor (1) according to the data record.

Description

State of the art

The present invention relates to a power train and a method for reducing a meshing noise of an electrically drivable drive train with a gear transmission. In particular, the present invention relates to the avoidance of expensive and expensive encapsulations for noise isolation of the gear transmission.

One of the most dominant noises of transmissions under load is that of meshing (ingress and egress jerk), by noise meaning a sound signal having one or more superimposed frequencies. The fact that transmissions produce noise under load is repeatedly reported in the literature, see Naunheimer, H .; Bertsche, B .; Lechner, G .: Vehicle transmission basics, selection, design and construction. Springer Verlag Berlin Heidelberg, 1st edition, 2007 such as Linke, H .: Spur Gears, Haser Verlag München Wien, 2010 , In particular, in machines where the noise from the transmission is perceived as particularly disturbing, such as in the automotive sector or electrically powered bicycles (eBikes, pedelecs) play noise reduction measures a major role.

• – die Anpassung der Zahngeometrie und/oder der Verzahnungsqualität,
• – die Anpassung der Lagerung der Getriebestufen,
• – eine weiche Lagerung der Zahnräder,
• – die Dämmung des Getriebegehäuses von innen und/oder der Lageraufnahmen,
• – die Verringerung der Schwingungsankopplung des Getriebes,
• – eine akustische Kapselung des Getriebes oder
• – der Einbau von Schwingungstilgern.

The noise is due in particular to the process of meshing. The process is understood as "Parameter-excited oscillation", see Naunheimer, page 266 , In the case of a loaded transmission, this vibration is stimulated by the change in the tooth stiffness itself, which depends on the engagement position of the gears. Linke describes in his work "Spurradverzahnung" (see above) for spur gear toothing the course of the toothing stiffnesses over a complete tooth engagement. The diagrams shown there are as 1 played. Therein, the tooth stiffness of the tooth pairs c _ZP and tooth stiffness c _Z for a degree toothing (partial diagrams a, c) and for a helical toothing (partial diagrams b / d) over the radian measure are shown. As can be seen, the spring stiffness c _Z (of t) depends on the engagement position of the gear teeth. This behavior is significantly influenced by the geometry and the elasticity of the gearing as well as by production-related gearing deviations and interference. Intervention disturbances occur during a load-related premature intervention. The meshing sound is heard in the airborne noise near the machine as howling or whistling. The type of noise and thus the frequency and amplitude spectrum of the sound signal depends on the type of toothing. In the prior art both passive measures and active measures are used to counteract the noise of gears. Among the passive measures include

• The adaptation of the tooth geometry and / or the tooth quality,
• - the adaptation of the bearing of the gear stages,
• A soft bearing of the gears,
• The insulation of the transmission housing from the inside and / or the bearing receptacles,
• The reduction of the vibration coupling of the transmission,
• - An acoustic encapsulation of the transmission or
• - the installation of vibration absorbers.

• – die Anpassung der Last und/oder der Drehzahl sofern möglich,
• – der Einbau von Aktuatoren im Lager eines Zahnrades (siehe Rebbechi, B.; Howard, C.; Hansen, C.: Active Control of Gearbox Vibration, Proceedings of the active control of sound and vibration conference, Fort Lauderdale, 1999, Seite 295 bis 304 ) oder
• – die Aufschaltung eines wechselnden Drehmomentes auf die Antriebsseite des Getriebes (siehe US 5,809,843 : Active cancellation of noise at gear mesh frequency for a gear assembly under load).

These measures entail complex design changes of the components and thus expensive tool changes, which can result in high costs in a series of large numbers. Another constructive measure is to select the number of teeth of the motor pinion as far as possible so that the frequency f _{0 is} equal to / 60 outside (usually below) a sensitive to the ear frequency range, where f ₀ the meshing frequency, n the engine speed and z is the number of engine pinion teeth. Among the active measures for noise compensation include

• - the adaptation of the load and / or the speed, if possible,
• - the installation of actuators in the bearing of a gear (see Rebbechi, B .; Howard, C .; Hansen, C .: Active Control of Gearbox Vibration, Proceedings of the Active Control of Sound and Vibration Conference, Fort Lauderdale, 1999, pages 295-304 ) or
• - The connection of a changing torque to the drive side of the transmission (see US 5,809,843 : Active cancellation of noise at a gear mesh frequency for a gear under load).

In the above scripture US 5,809,843 an electrical machine is used to counteract the vibrations and / or the noise of the meshing. The vibrations / noises are measured on the gear housing and passed as a fault signal to a controller that compensates for the vibrations and / or noise.

It is an object of the present invention to reduce the vibrations and / or the noises by the meshing of a transmission with the least possible effort.

Disclosure of the invention

The above object is achieved by a drive train and a method for reducing a meshing noise of an electrically drivable drive train with a gear transmission and an electric motor. The basic idea of the invention is the Actuation of the transmission with a torque signal which counteracts the vibration or the noise of the transmission. The signal of the compensation torque is added to other desired torques, such as a static drive torque. The advantage of the invention is that with the connection of the torque signal vibrations and / or noises emanating from the meshing process, without vibration sensor or noise sensor can be significantly reduced. To achieve this, a suitable torque signal is determined before operation, which is adjusted depending on the operating state of the electric machine and the transmission and provided as a control of the electric machine.

In other words, an operating state of the drive train is first determined. The operating state can be characterized by a torque to be transmitted by means of the transmission and / or a rotational speed. The geometry of the gear transmission or the teeth contained in it is of course known a priori. A temperature of the components of the drive train, in particular of the gears and a transmission ratio or a gear combination used can characterize the operating state. Subsequently, a data record associated with the determined operating state is read from a data memory. In other words, a previously stored data set is consulted as a function of the operating state in order to adapt the torque of the electric motor according to the data set in a further step. In this case, the data set represents a measure by means of which the disturbing alternating variables of the operating vibrations can be reduced in such a way that the acoustic impression of the drive train improves for the human ear. A metrological determination of vibrations and generation of a compensation signal determined on the basis of this can be omitted according to the invention. This reduces the hardware expenditure within the drive train according to the invention and reduces the computing power required during operation.

The dependent claims show preferred developments of the invention.

• – eine Temperatur des Zahnradgetriebes,
• – eine Drehzahl des Antriebsstrangs,
• – ein von dem Elektromotor angefordertes Drehmoment,
• – eine Fahrstufe beziehungsweise ein Übersetzungsverhältnis, beziehungsweise eine Zahnradkombination,
• – ein Strom durch den Elektromotor,
• – eine Winkellage des Antriebsstrangs und
• – eine zum Betrieb des Elektromotors erforderliche Spannung.

umfasst. Die vorbenannten Betriebszustandskenngrößen können messtechnisch einfach ermittelt und beispielsweise in Form eines Kennfeldes zur Erzeugung eines Kompensationssignals verwendet werden. The operating state can be determined, for example, on the basis of an operating state parameter which is from the group

• A temperature of the gear transmission,
• A speed of the drive train,
• A torque requested by the electric motor,
• A gear stage or a gear ratio, or a gear combination,
• A current through the electric motor,
• - An angular position of the drive train and
• - A voltage required for operation of the electric motor.

includes. The abovementioned operating state parameters can be easily determined metrologically and used, for example, in the form of a characteristic diagram for generating a compensation signal.

Preferably, the generation of the compensation signal can be carried out at the factory, so that a large number of signal forms coming into question for the compensation signal can be assigned to a respective operating state parameter combination and stored in the data memory. During operation of the drive train according to the invention, a suitable compensation signal can be read from the data memory and / or generated on the basis of parameters stored in the data memory by a metrologically simple determination of the operating state. A known in the art recording and analysis of vibration signals of the operating noise can therefore be omitted.

A required during operation of the drive train according to the invention torque (which is substantially constant over time or slowly variable) can be superimposed to reduce the meshing noise according to the invention with a torque change signal generated according to the record. In particular, the tooth stiffness that varies over the angle of rotation of the transmission can be taken into consideration, which in 1 is shown. In other words, the torque change signal is generated such that in the superposition with the current desired torque results in a reduced meshing noise. In this way, the gear transmission is acted upon by the electric motor with an input torque, which reduces the generation of operational meshing noise.

The drive train may be designed for an electrically drivable means of locomotion. Since the electrification of passenger transport in the form of bicycles and cars is currently progressing rapidly, a cost-effective and due to low additional masses environmentally friendly measure to reduce the traffic noise is thus provided.

According to a second aspect of the present invention, a power train is proposed, which includes an electric motor, a gear transmission, a data memory and a control unit includes. The control unit is configured according to the invention to determine an operating state of the drive train and to read out a data record associated with the determined operating state from the data memory. Based on the data set, the control unit generates an electrical input signal for the electric motor, by means of which it exerts a torque on the gear transmission, which causes over the prior art, a reduction of the meshing noise of the drive train. In this case, the data record in the data memory represent a time signal or include parameters for generating a suitable torque change signal, which is superimposed on the desired torque of the electric motor for reducing the meshing noise. The features, combinations of features and the advantages resulting therefrom, in accordance with those set out in connection with the first aspect of the invention, can be seen in such a way that, in order to avoid repetition, reference is made to the above statements.

The data memory may preferably be factory-described with a plurality of data records, which is assigned to different operating states of the drive train. In this way, costly measurements and investigations of dependencies between operating state characteristics can be made in the determination of suitable adjustments of the desired torque of the electric motor. In the operation of the individual drive train optionally not available for evaluating the operating state computing power can thus be used in the factory to reduce the meshing noise of the drive train by appropriate records.

According to a third aspect of the present invention, a means of transportation is proposed, which may be designed, for example, as an electrically drivable bicycle or as an electrically drivable passenger car / van / truck. According to the invention, the means of locomotion comprises a drive train as described according to the second aspect of the present invention. Also with regard to the relevant features, feature combinations and advantages, reference is made to the above statements.

Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

1 an overview of tooth stiffnesses over a complete tooth engagement over the angle of rotation in radians as well as to the energies of corresponding meshing noises;

2 an overview of components of an embodiment of a drive train or vehicle according to the invention; and

3 a flowchart illustrating a step of an embodiment of a method according to the invention.

Embodiments of the invention

1a shows a diagram of the tooth stiffness of the tooth pairs c _ZP and the toothing stiffness c _Z on the example of a degree of toothing. Due to the tooth geometry results in a comparatively strong stroke of the tooth stiffness c _Z over the rotation angle. As shown in partial diagram c, this leads to high energies in the corresponding vibration spectrum of the operating noise. Partial diagrams b) / d) show corresponding diagrams for the example of helical gearing, which is much less noticeable acoustically. The stroke of the toothing stiffness c _Z takes over angle of rotation Φ is just as clearly reduced as the energy of the harmonically corresponding vibration spectrum

2 shows a car 20 with a powertrain 10 , by means of which the effect of the present invention on the vibration behavior of a drive train is to be explained. Starting from a desired torque 5 which originates, for example, from a motor control unit (not shown) becomes a control unit 4 , which information technology with a data memory 3 is used to provide a torque change signal, by means of which the meshing noise of the illustrated powertrain 10 should be reduced. The torque change signal is in a summer 6 the desired torque 5 superimposed and a motor controller 7 fed. The engine governor 7 generates a power signal, by means of which the phases of an electric motor 1 be charged with electrical energy. The motor controller may be provided with any required adjustment of the phase voltages 7 via a feedback branch 8th an information regarding the phase currents of the electric motor 1 , The output side is the electric motor 1 via a first shaft with a gear transmission 2 coupled, which on the output side via a second shaft 11 with a mechanical load 12 is coupled. Of course, more gear stages between the gear transmission 2 and the mechanical load 12 be provided without this would affect the applicability of the method according to the invention. The operating noise of the transmission 2 is due to a modified according to the invention torque of the electric motor 1 reduced, which based on a current operating state by the control unit 4 being affected. The control unit receives this 4 via a feedback branch 14 Information about the Operating status of the motor controller 7 in response to which a suitable record from the data store 3 , which has been factory filled, retrieved and converted into a suitable torque change signal. The closed circle of engine governor 7 and control unit 4 over the feedback branch 14 provides an active damping of the parameter-excited vibration in the transmission 2 , Thus, the invention enables the reduction of vibration and / or noise, since the vibration / noise source itself is compensated.

3 shows steps of an embodiment of a method according to the invention for reducing a meshing noise of an electrically driven drive train with a gear transmission and an electric motor. In step 100 At the factory, data sets for different operating states are written in a data memory of the drive train, which represent compensation signals for reducing the meshing noise of the respective operating states. These can be time signals for torque change signals or parameter sets by means of which the torque change signals can be generated. In step 200 During operation of the drive train according to the invention, an operating state is determined and in step 300 an associated record is read from the data store. Subsequently, in step 400 adapted to reduce the meshing noise, the torque of the electric motor corresponding to the record by superimposing a suitable torque change signal, whereby the operating noise of the drive train is reduced.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5809843 [0004, 0005]

Cited non-patent literature

• Naunheimer, H .; Bertsche, B .; Lechner, G .: Vehicle transmission basics, selection, design and construction. Springer Verlag Berlin Heidelberg, 1st edition, 2007 [0002]
• Linke, H .: Spur gear toothing, Haser Verlag München Wien, 2010 [0002]
• "Parameter-excited oscillation", see Naunheimer, page 266 [0003]
• Rebbechi, B .; Howard, C .; Hansen, C .: Active Control of Gearbox Vibration, Proceedings of the Active Control of Sound and Vibration Conference, Fort Lauderdale, 1999, pages 295-304. [0004]

Claims (9)

Method for reducing meshing noise of an electrically drivable drive train ( 10 ) with a gear transmission ( 2 ) and an electric motor ( 1 ), comprising the steps - determining ( 200 ) an operating state of the drive train ( 10 ), - readout ( 300 ) of a data record associated with the determined operating state from a data memory ( 3 ), and - Customize ( 400 ) of a torque of the electric motor ( 1 ) according to the data set for reducing the meshing noise of the drivetrain ( 10 ). Method according to claim 1, wherein the operating state is determined on the basis of an operating state parameter which - a temperature of the gear transmission ( 2 ), and / or - a rotational speed of the drive train ( 10 ), and / or - one of the electric motor ( 1 ) requested torque, and / or - a drive stage, and / or - a current through the electric motor ( 1 ), and / or - an angular position of the drive train ( 10 ), and / or - one for operating the electric motor ( 1 ) includes required voltage. Method according to one of the preceding claims, further comprising - storing ( 100 ) of the determined operating state associated record. Method according to one of the preceding claims, wherein adjusting the torque of the electric motor ( 1 ) comprises overlaying a current torque with a torque change signal generated in accordance with the data set. Method according to one of the preceding claims, wherein the drive train ( 10 ) for an electrically driven means of transportation ( 20 ) is designed. Drive train comprising: - an electric motor ( 1 ), - a gear transmission ( 2 ), - a data memory ( 3 ), and - a control unit ( 4 ), the control unit ( 4 ), - an operating state of the drive train ( 10 ) to investigate ( 200 ), - and a data record associated with the determined operating state from the data memory ( 3 ) read out ( 300 ), and - a torque of the electric motor ( 1 ) according to the data set for reducing a meshing noise of the drive train ( 10 ) ( 400 ). Drive train according to one of the preceding claims, wherein the data memory ( 3 ) is factory described with a variety of data sets corresponding to different operating conditions. Drive train according to one of the preceding claims, which is suitable for an electrically drivable means of locomotion ( 20 ) is designed. Means of transport, in particular electrically driven bicycle, comprising a drive train ( 10 ) according to one of the preceding claims 6 to 8.

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