DE102022211852B4 - transmission device with torque damping control - Google Patents

Abstract

Transmission device for driving a vehicle, comprising an electric motor (EM) as the drive motor of the vehicle and a transmission for translating the drive torque of the electric motor (EM) to an output torque of a driven axle of the vehicle, wherein the transmission comprises a transmission output gear (e), wherein the transmission device comprises a control device (h), wherein the control device (h) comprises an active torque damping control so that undesirable torque peaks can be reduced by the active torque damping control, wherein the transmission device comprises a speed detection device with which the speed (n ₂ ) of the transmission output gear (e) can be detected and wherein, depending on the speed (n ₂ ) of the transmission output gear (e) determined by the speed detection device, the active torque damping takes place by the torque damping control of the control device (h), characterized in that the speed detection device with which the speed (n ₂ ) of the transmission output gear (e) can be detected comprises a so-called "virtual sensor", wherein the rotational speed (n ₂ ) is determined by a calculation model based on the vibration behavior of a specific vehicle in which the transmission device is installed, as known from an end-of-line test.

Description

field of the invention

The present invention relates to a transmission device for driving a vehicle, wherein the transmission device comprises a control device, wherein the control device comprises an active torque damping control, so that undesirable torque peaks can be reduced by the active torque damping control. The invention also relates to a method for torque damping of a drive train.

State of the art

Due to driving maneuvers that can occur intentionally or unintentionally when a motor vehicle is in operation, high torque peaks form in the drive train, including the associated wheel decelerations or wheel accelerations. These can be many times higher than the axle torque. In contrast to conventional main transmissions operated by combustion engines, electric primary or secondary drives do not usually use frictional clutches or brakes in the power transmission path, which - depending on the degree of overlocking - have a torque-limiting effect due to their function. In addition, significantly higher overall transmission ratios are used in electric main drives, which in turn can result in highly reduced mass moments of inertia.

Since the mechanical design and dimensioning of gears is based on such maximum possible torque peaks ("abuse torques") for generically defined and worst-case misuse maneuvers, this leads to the selection of large rolling bearings or correspondingly massive bearing types and the implementation of corresponding shaft diameters and gear widths. This leads to poorer efficiency behavior - i.e. higher mechanical power loss, as well as higher weight, larger required installation space and higher costs.

Known methods for torque damping are also referred to as “active damping” and use the signals available on the vehicle bus, for example the wheel speed signals, or use torque estimators to calculate the effective axle torques.

Due to bus signal propagation times and torsional stiffness of the side shafts, existing rotational flank play on running and plug gears and influences of elasticity of the transmission suspension in the vehicle, torque peaks at the EM rotor shaft level occur more or less delayed from the wheel speed signals, which means that reliable counteraction by active control of the electric machine is only possible to a limited extent.

From the DE 102 37 710 A1 A drive train is known, consisting of a drive unit, a transmission with at least one transmission input shaft and at least one transmission output shaft operatively connected to at least one drive wheel. Between the at least one transmission input shaft and a drive shaft of the drive unit, an automatically actuated friction clutch is provided, the disengagement and engagement processes of which are controlled by means of a control unit at least as a function of signals from a sensor device detecting a speed of the transmission input shaft and a speed of the at least one drive wheel, wherein vibrations that occur in a torque transmission are dampened via friction surfaces of the friction clutch, wherein a variable formed from the speed of a transmission output component and from the speed of the transmission input shaft serves as a control parameter for dampening the vibrations.

The DE 10 2010 023 710 A1 discloses a control system for a powertrain of a vehicle, comprising: a torque module that determines a first output torque of an engine, determines a second output torque of the engine after determining the first output torque, and determines a torque difference based on the first output torque and the second output torque; and a damping control module that controls operation of a clutch to produce a damping torque in a transmission based on the torque difference.

From the DE 103 01 869 A1 A method for damping vibrations in a drive train with an engine, at least one clutch and a transmission, in particular for a motor vehicle, is known, wherein the drive train has a plurality of sensors for recording measured variables and a plurality of actuators controlled by means of manipulated variables, wherein a drive control of the drive train controls the actuators in a coordinated manner by means of the manipulated variables using the measured variables of the plurality of sensors.

The document DE 10 2013 113 658 A1 teaches a method for operating a drive train of at least one control unit for transmitting a target data corresponding to a target torque set, which is driven by at least one detection component which detects a respective drive train vibration, at least one electric motor which generates a drive torque corresponding to the target torque, and a drive component of the drive train which supplies the at least one electric motor with electrical drive energy, with the steps: determining a vibration data set describing the drive train vibrations by means of the detection component, determining a compensation data set based on the vibration data set by means of a compensation component which is different from the control unit and integrated in the power electronics, wherein the compensation data set has control commands designed to compensate for the drive train vibrations for a control unit of the power electronics which controls an energy flow to the electric motor, executing the control commands by the control unit so that a compensation torque which reduces the drive train vibrations is superimposed on the drive torque.

Summary of the Invention

It is an object of the invention to provide a transmission device for driving a vehicle, which comprises reliable torque damping and thus enables better efficiency, lower mechanical power loss, lower weight, installation space and costs of the transmission device and the vehicle.

The object is achieved by a transmission device for driving a vehicle with the features according to claim 1.

The transmission device comprises an electric motor as the drive motor of the vehicle and a transmission for translating the drive torque of the electric motor to an output torque of a driven axle of the vehicle, wherein the transmission comprises a transmission output gear, wherein the transmission device comprises a control device, wherein the control device comprises an active torque damping control so that undesirable torque peaks can be reduced by the active torque damping control, wherein the transmission device comprises a speed detection device with which the speed of the transmission output gear can be detected and wherein, depending on the speed of the transmission output gear determined by the speed detection device, the active torque damping is carried out by the torque damping control of the control device.

According to the invention, the speed detection device, with which the speed of the transmission output gear can be detected, comprises a so-called “virtual sensor”, wherein the speed is determined by a calculation model based on the vibration behavior of a specific vehicle in which the transmission device is installed, as known from an end-of-line test.

According to the invention, a transmission architecture is thus specified with an additional speed detection on the transmission output side, so that on the basis of this speed detection on the transmission output side, a new method for actively damping undesirable torque peaks or resonance frequencies in an electrified drive train is made possible, which preferably forms a closed control loop.

A closed control loop can be represented within the electric drive module via the speed measurement on the gearbox output side. This enables flexible, software-based protection against torque peaks introduced from the outside as well as active load peak reduction for all gearbox components. The protective measure can be implemented in particular, depending on the gearbox architecture and the current operating state, by actively controlling a decoupling clutch, preferably at or close to the torque zero crossing, and/or by actively controlling the electric traction machine.

Simulations carried out using a reference vehicle with a selected driving maneuver show that, with exact knowledge of the wheel speed and taking into account the characteristics of the electric motor, a load peak reduction of the order of around 2500Nm at axle level can be achieved. Even with a speed signal delayed by just 20ms and a sampling rate of 10ms, an effective reduction in the load peak can no longer be achieved. If the signal delay time is more than 20ms, the load peak is amplified in an undesirable way, since the torque built up on the electric motor is already half the period out of phase with the disturbance torque and amplifies it. Interactions with vehicle stabilization systems (ABS, ESP) are not taken into account in these studies. The influence of the delayed torque build-up on the electric motor, on the other hand, is to be classified as rather small.

In order to limit the design and dimensioning to the nominal axle torque, and yet ensure sufficient safety against all misuse loads, a system is specified which actively counteracts the torque peaks or reduces the power path and thus reliably prevents the introduction of unwanted load peaks into the transmission mechanism.

According to the invention, this active peak load reduction takes place in-situ through targeted interventions, depending on the angular speeds of all rotating machine elements and electronic components, with only short latency times between detection, transmission and actuation being accepted. A major contributor to the overall latency is the detection and transmission of the wheel speed signals. This usually takes place via a signal bus, for example the CAN bus in a vehicle. Since time delays of up to 300ms can occur as a result of signal detection and transmission and the sampling rate is often not sufficient for highly dynamic control, reliable active control intervention or the actuation of a separating clutch unit is very difficult to implement. To counteract this, the solution according to the invention can be used to increase the quality of the speed information and keep the signal delay time to a minimum, regardless of the respective vehicle architecture.

• • ein geschlossener Regelkreis mit hoher Genauigkeit und kurzen Signalverzugsszeiten, durch direkte Einbindung des tatsächlich gemessenen Drehzahlsignals auf Achsniveau.
• • eine Reduktion von Latenzzeiten.
• • Unabhängig von der Fahrzeugarchitektur wie bspw. von Datenbus und Raddrehzahlsensorik.

Depending on the design, the following advantages can be achieved by a solution according to the invention:

• • a closed control loop with high accuracy and short signal delay times, through direct integration of the actually measured speed signal at axle level.
• • a reduction in latency times.
• • Independent of the vehicle architecture such as data bus and wheel speed sensors.

• • Ermöglicht die Erhöhung der Genauigkeit bei der Umsetzung von Active Damping Methoden.
• • Ermöglicht die Reduzierung von Sicherheiten bei der Auslegung der mechanischen Komponenten.
• • Ermöglicht die Reduktion von Gewicht und Kosten sowie die Erhöhung von Effizienz und Leistungsdichte.

The in-situ actuator control thus specifically counteracts misuse torques and thus has a positive effect on the dimensioning and design of the machine elements. The design limit can therefore refer to the nominal torque and not to an expected misuse torque or to possible torque peaks.

• • Enables to increase the accuracy when implementing Active Damping methods.
• • Enables the reduction of safety factors in the design of mechanical components.
• • Enables the reduction of weight and costs as well as the increase of efficiency and power density.

Further developments of the invention are specified in the dependent claims, the description and the accompanying drawings.

Preferably, the speed detection device, with which the speed of the transmission output gear can be detected, comprises an incremental encoder geometry on the transmission output gear and a housing-fixed sensor, for example a Hall sensor.

Preferably, the incremental encoder geometry on the transmission output gear is introduced into the transmission output gear during the manufacturing molding process of the transmission output gear. In another embodiment, the incremental encoder geometry is designed as an insert, in particular as a plastic insert, in the transmission output gear.

Preferably, the incremental geometry is additionally designed as part of a conveying device for an oil circuit. The increments can serve as a guide and conveying device for the oil, in particular by means of a suitable inclination.

Preferably, the active torque damping control of the transmission device, i.e. the prevention of a parasitic, externally acting power flow, can be carried out by actively controlling the electric motor, i.e. by corresponding active EM control intervention, in particular by setting a torque in the direction of the externally introduced torque peak, and/or by actively controlling a decoupling unit, preferably by separating a differential bevel gear from a side shaft, preferably at or close to a zero crossing of the torque. The active torque damping control can optionally also be carried out by activating a vehicle-side driving dynamics control system.

The active torque damping control preferably forms a closed control loop together with the speed detection device.

Preferably, the transmission device forms a closed subsystem, in particular an EDU subsystem (Electric Drive Unit), so that the compensation of externally introduced disturbances takes place exclusively within the transmission device and no electronic interfaces to other vehicle-side subsystems, such as a vehicle dynamics control system, are required.

In one embodiment, the transmission device additionally comprises a passive drive train decoupling or damping element, preferably arranged in the drive train between a transmission output shaft and the differential carrier of the transmission device.

A method according to the invention for torque damping of a drive train, so that undesirable torque peaks are reduced by active torque damping control, is carried out by means of a transmission device as described above, and comprises that after detecting at least the speed of the transmission output gear as an input variable, active torque damping takes place, depending on the speed of the transmission output gear determined by the speed detection device, by actively controlling the electric motor and/or by actively controlling a separating clutch. Optionally, an activation of a vehicle-side driving dynamics control system can also take place, depending on the speed of the transmission output gear determined by the speed detection device.

Short description of the drawings

• 1 ist eine schematische Darstellung einer erfindungsgemäßen Getriebeeinrichtung.
• 2 ist eine schematische Darstellung einer weiteren erfindungsgemäßen Getriebeeinrichtung.
• 3a ist eine grobe schematische Darstellung eines erfindungsgemäßen Verfahrens mit einer Getriebeeinrichtung gemäß 1 oder 2.
• 3b ist eine detailliertere schematische Darstellung eines erfindungsgemäßen Verfahrens mit einer Getriebeeinrichtung gemäß 1 oder 2.
• 4 ist ein beispielsweiser Verlauf der an der Getriebeantriebswelle und an der Getriebeabtriebswelle gemessenen Drehzahlsignale n über der Zeit t, vor, während und nach einer Drehmomentstörung, bei Ausführung eines erfindungsgemäßen Verfahrens zur Drehmomentdämpfung.

The invention is described below by way of example with reference to the drawings.

• 1 is a schematic representation of a transmission device according to the invention.
• 2 is a schematic representation of another transmission device according to the invention.
• 3a is a rough schematic representation of a method according to the invention with a transmission device according to 1 or 2 .
• 3b is a more detailed schematic representation of a method according to the invention with a transmission device according to 1 or 2 .
• 4 is an example of the course of the speed signals n measured at the transmission input shaft and at the transmission output shaft over time t, before, during and after a torque disturbance, when carrying out a method according to the invention for torque damping.

Detailed description of the invention

In the 1 and 2 a transmission device according to the invention is shown in each case.

1 shows a two-stage eDrive system in offset architecture. This consists of the electric motor EM, rolling bearings a, the pinion b, which meshes with the first gear on the intermediate shaft c. The second gear stage in turn consists of the second gear on the intermediate shaft d and the transmission output gear e, i.e. the final gear, at axle level, so that the speed of the axle corresponds to the speed of the transmission output gear e.

With the help of a suitable detection/counting instrument f and g, the actual speed of the transmission output gear e can be read immediately. This has the advantage that the signal size can be directly integrated into the Electric Drive Unit (EDU) as a control unit h and can be used for active torque control or for the actuation of a DC separating clutch unit ( 2 ) necessary period of time.

Furthermore, it is possible that all downstream disturbances of the eDrive actual speed (e.g. side shaft compliance, play in the differential and in the splines) can be eliminated and the accuracy increased.

Due to the virtually latency-free speed detection of the output, the control of an existing separating clutch unit can be carried out DC in order to specifically prevent the introduction of load peaks into the mechanics - see DC in 2 .

If, for example, the electric drive unit (EDU) h is not equipped with a DC separating clutch unit, the parasitic load introduced can be significantly reduced or completely eliminated by actively using targeted control interventions (=active setting of torques) of the EM due to the slight time shift of the actual speed signal - without a vehicle-side signal bus delay. This control intervention, or active damping, generates a torque that is aligned with the parasitic torque acting from the outside. The resulting differential torque is therefore significantly lower than in the case without active damping.

The incremental geometry f can, for example, be integrated as a negative form in a forging die or in a casting die and can be introduced into the gear body of the transmission output gear e during the forming process to form the gear, without any additional or post-processing being required. Only a pickup or sensor g integrated in the housing, for example a Hall sensor, has to scan the increments.

Alternatively, the incremental geometry f can be designed as a plastic insert, which in turn can have positive effects on design freedom and the adoption of series wheel body designs.

Furthermore, the functional extension of the incremental geometry f can be implemented by a conveying device for the oil circuit. The increments can serve as a combined guide and conveying device for the oil by being suitably inclined.

By additionally integrating a passive drive train decoupling or damping element at a suitable point in the drive train and taking the corresponding parameters into account in the control loop, the power required by the electric machine for actively damping the torque peaks can be reduced. Due to the exact knowledge of all parameters in the eDS system that are relevant to the vibration behavior, such as rotational flank play, mass moments of inertia, torsional stiffness, friction and damping parameters, the closed control loop can be precisely mapped in the control and regulation software and the presence of the input and output side speeds enables precise control intervention without having to rely on the quality of signals provided by the vehicle.

To 3a : The dynamic input variables IN (torque, speed) recorded in the control unit h ECU (electronic control unit) or EDU (electric drive unit) are analyzed and subsequently, by means of a method V according to the invention, one or a combination of possible intervention measures is activated, namely 1) opening the DC separating clutch unit 2) setting a counter torque with the EM (active peak load damping) or optionally also 3) the high torque peak using the vehicle's driving dynamics control systems ESC. When an external disturbance is detected, the control chain is activated (closed-loop control mode for active peak load reduction), whereby one or more of the possible actions 1 and/or 2 and/or 3 are initiated.

3b shows possible steps in a method V according to the invention, which forms a closed-loop control mode for active peak load reduction.

Step 1 is a query as to whether the temporal change of the axle speed, i.e. the speed n ₂ of the transmission output gear e, is above a permissible limit value: |dn ₂ /dt|>limit value?

If “No” N, step 2 follows: No action required, therefore no attenuation.

If "yes" Y, step 3 follows: request for active load peak reduction. In step 4 a query is made: Can a change in the torque direction be detected? |n ₁ /n ₂ | > limit value?

If “yes” Y, the DC decoupling clutch is activated in step 5.

If “No” N, step 6 follows, a query as to whether there is sufficient power reserve of the electric machine EM: |P _act |< |P _peak |?

If “yes” Y, “Active Peak Load Damping” is activated in step 7, i.e. the electric motor EM for damping.

If “No” N, step 8 follows, a request for intervention by the active vehicle dynamics management (ESC).

4 shows an example of a qualitative curve of the speed signals n _EM and n _A measured on the transmission input shaft, i.e. on the electric motor EM, and on the transmission output shaft, i.e. on the axis A, where the speeds n are given in rpm (y-axis) and the curve over time t in seconds s (x-axis). n _A generally corresponds to the speed of the transmission output gear n ₂ , n _EM generally corresponds to the speed of the pinion n ₁ . A torque peak introduced by an external disturbance leads to a speed fluctuation on the transmission output gear e. In the short term, due to the rotational backlash and elasticity present in the system, a speed difference arises between the output speed and the EM input speed. An example of such a speed difference ΔA1 due to an external disturbance is shown in 4 visible. If relative speed changes between the gearbox output shaft and gearbox input shaft are detected, the active control intervention is triggered immediately and the countermeasures are initiated within the time window Δt. If a measure is taken to open the DC separating clutch unit, it must be fully released within the time window Δt (torque zero crossing).

According to the invention, the hardware speed sensor can be replaced by a virtual sensor if the vibration behavior of the system is sufficiently known. In this case, a calculation model is implemented which, based on look-up tables, determines the corresponding wheel speed without delay in every operating state. This combination of calculation operation and underlying data packets is referred to as a "virtual sensor". As part of the quality assurance process, each product is subjected to a so-called "end of line test". Each finally assembled Electric Drive Unit "EDU" undergoes a defined test run to ensure the above-mentioned process. During these "end of line" tests, defined speed/torque combinations can be approached in order to create data tables, also known as look-up tables, for the vibration-relevant system parameters (rigidity, damping, torsional backlash). Finally, the calculation operations are written to the Electric Control Unit "ECU" using the created look-up tables. During operation, the wheel speed is available in every operating state and can be used as a “virtual ler sensor”, for example for active damping interventions or as a road-level control variable for the electric motor. It is also possible to dispense with the rotor-side speed sensor - also called a "resolver" - when controlling the EM torque at wheel speed level using look-up tables, which can bring an additional cost advantage.

list of reference symbols

a

rolling bearings

b

pinion

c

intermediate shaft

d

second gear on intermediate shaft

e

transmission output gear

f

Incremental encoder geometry

G

sensor

h

control unit of the Electric Drive Unit

n1

pinion speed

n2

speed of the transmission output gear

nEM

speed of the electric motor

n/a

speed of the axle

EM

electric motor

ESC

Electronic Stability Control, driving dynamics control system

DC

separating clutch

ΔA0

speed difference without the presence of a disturbance torque

ΔA1

speed difference in the presence of a disturbance torque

Δt

time frame

1

Query whether the change in the axle speed over time, i.e. the speed n ₂ of the transmission output gear e, is above a permissible limit value. is: |dn ₂ /dt|>limit value?

2

No action required

3

requirement for active peak load reduction

4

Query: Is a change in the torque direction detectable? |n1/n2|> limit?

5

Activation of the DC clutch

6

Query whether there is sufficient power reserve of the electric machine EM: |Pact|<|Ppeak|?

7

Activation of “Active Peak Load Damping”, i.e. the EM electric motor for damping

8

Request for intervention by the active vehicle dynamics management (ESC)

N

No

Y

Yes

Claims (6)

Transmission device for driving a vehicle, comprising an electric motor (EM) as the drive motor of the vehicle and a transmission for translating the drive torque of the electric motor (EM) to an output torque of a driven axle of the vehicle, wherein the transmission comprises a transmission output gear (e), wherein the transmission device comprises a control device (h), wherein the control device (h) comprises an active torque damping control so that undesirable torque peaks can be reduced by the active torque damping control, wherein the transmission device comprises a speed detection device with which the speed (n ₂ ) of the transmission output gear (e) can be detected and wherein, depending on the speed (n ₂ ) of the transmission output gear (e) determined by the speed detection device, the active torque damping takes place by the torque damping control of the control device (h), characterized in that the speed detection device with which the speed (n ₂ ) of the transmission output gear (e) can be detected, a so-called "virtual sensor" wherein the rotational speed (n ₂ ) is determined by a calculation model on the basis of the vibration behavior of a specific vehicle in which the transmission device is installed, as known from an end-of-line test. Gearbox according to claim 1 , characterized in that the active torque damping control of the transmission device can be carried out by active control of the electric motor (EM) and/or by active control of a separating clutch (DC), preferably at or close to a zero crossing of the torque. Transmission device according to at least one of the preceding claims, characterized in that the active torque damping control together with the speed detection device forms a closed control loop. Transmission device according to at least one of the preceding claims, characterized in that the transmission device is a forms a closed subsystem, so that the compensation of externally introduced disturbances takes place exclusively within the transmission device and no electronic interfaces to other vehicle-side subsystems, such as a vehicle's driving dynamics control system (ESC), are required. Transmission device according to at least one of the preceding claims, characterized in that the transmission device additionally comprises a passive drive train decoupling or damping element, preferably arranged in the drive train between the transmission output gear (e) and a differential carrier of the transmission device. Method for torque damping of a drive train, so that undesirable torque peaks are reduced by an active torque damping control, by means of a transmission device according to at least one of the preceding claims, characterized in that after detecting at least the rotational speed (n ₂ ) of the transmission output gear (e) as an input variable, an active torque damping, depending on the rotational speed (n ₂ ) of the transmission output gear (e) determined by the rotational speed detection device, takes place by actively controlling the electric motor (EM) and/or by actively controlling a separating clutch (DC) and/or by activating a vehicle-side driving dynamics control system (ESC).

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