Transmission unit with torque damping control

Abstract

A transmission device for driving a vehicle, comprising an electric motor (EM) as the vehicle's drive motor and a transmission for translating the drive torque of the electric motor (EM) into 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 sensing device with which the speed (n2) of the transmission output gear (e) can be detected, and wherein, depending on the speed (n2) of the transmission output gear (e) determined by the speed sensing device, the active torque damping is effected by the torque damping control of the control device (h), characterized in thatthat the speed detection device with which the speed (n2) of the transmission output gear (e) can be detected comprises a so-called "virtual sensor", wherein the speed (n2) is determined by a computational 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

[0001] 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 unwanted 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

[0002] Due to driving maneuvers, which can occur intentionally or unintentionally during the operation of a motor vehicle, high torque peaks develop in the drivetrain due to, among other things, the associated wheel decelerations or wheel accelerations. These peaks can be many times the axle torque in magnitude. In contrast to conventional main transmissions powered by combustion engines, electric primary or secondary drives typically do not use frictional clutches or brakes in the power transmission path, which – depending on the degree of overlock – have a torque-limiting effect due to their function. Furthermore, significantly higher overall transmission ratios are used in electric main drives, which in turn can result in significantly reduced mass moments of inertia.

[0003] Since the mechanical design and dimensioning of gearboxes 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, as well as the implementation of corresponding shaft diameters and gear widths. This results in poorer efficiency—i.e., higher mechanical power losses—as well as higher weight, larger required installation space, and higher costs.

[0004] 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.

[0005] Due to bus signal propagation times and torsional stiffness of the side shafts, existing backlash on running and plug-in gears and influences of elasticities of the transmission suspension in the vehicle, torque peaks at the EM rotor shaft level occur with a more or less time delay to the wheel speed signals, which means that reliable counteraction by active control of the electric machine is only possible to a limited extent.

[0006] DE 102 37 710 A1 discloses a drive train comprising 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. An automatically actuated friction clutch is provided between the at least one transmission input shaft and a drive shaft of the drive unit, the disengagement and engagement processes of which are controlled by a control unit at least as a function of signals from a sensor device detecting a rotational speed of the transmission input shaft and a rotational speed of the at least one drive wheel. Vibrations occurring in a torque transmission are damped via friction surfaces of the friction clutch. A variable formed from the rotational speed of a transmission output component and the rotational speed of the transmission input shaft serves as a control parameter for damping the vibrations.

[0007] 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 the operation of a clutch to generate a damping torque in a transmission based on the torque difference.

[0008] From DE 103 01 869 A1 a method for vibration damping of 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.

[0009] The document DE 10 2013 113 658 A1 teaches a method for operating a drive train of a motor vehicle comprising at least one control unit for transmitting a target data set corresponding to a target torque, which is driven by at least one detection component detecting a respective drive train vibration, at least one electric motor generating a drive torque corresponding to the target torque, and a drive component of the drive train comprising power electronics supplying the at least one electric motor with electrical drive energy, comprising the steps of: 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 different from the control unit and integrated in the power electronics,wherein the compensation data set comprises control commands designed to compensate for the drive train vibrations for a control unit of the power electronics that controls an energy flow to the electric motor, execution of the control commands by the control unit so that a compensation torque that reduces the drive train vibrations is superimposed on the drive torque. Summary of the invention

[0010] It is an object of the invention to provide a transmission device for driving a vehicle, which comprises a 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.

[0011] The problem is solved by a transmission device for driving a vehicle having the features according to claim 1.

[0012] The transmission device comprises an electric motor as the drive motor of the vehicle and a gearbox for translating the drive torque of the electric motor to an output torque of a driven axle of the vehicle, wherein the gearbox comprises a gearbox output gear, wherein the transmission device comprises a control device, wherein the control device comprises an active torque damping control so that undesired 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 gearbox output gear can be detected and wherein the active torque damping is carried out by the torque damping control of the control device depending on the speed of the gearbox output gear determined by the speed detection device.

[0013] 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 computer model based on the vibration behavior of a specific vehicle in which the transmission device is installed, which vibration behavior is known from an end-of-line test.

[0014] 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 unwanted torque peaks or resonance frequencies in an electrified powertrain is enabled, which preferably forms a closed control loop.

[0015] By sensing the speed on the transmission output side, a closed control loop can be implemented within the electric drive module. This enables flexible, software-based protection against externally induced torque peaks as well as active peak load reduction for all transmission components. Depending on the transmission architecture and the current operating state, the protective measure can be implemented by actively controlling a decoupling clutch, preferably at or near the zero torque crossing, and / or by actively controlling the electric traction motor.

[0016] Simulations conducted on a reference vehicle with a selected driving maneuver show that, with precise knowledge of the wheel speed and consideration of the electric motor characteristics, a peak load reduction of the order of approximately 2500 Nm at axle level can be achieved. Even with a speed signal delayed by just 20 ms and a sampling rate of 10 ms, an effective reduction in the peak load can no longer be achieved. If the signal delay time is more than 20 ms, however, the peak load is amplified in an undesirable manner, since the torque built up at the electric motor is already half the period out of phase with the disturbance torque and amplifies it. Interactions with vehicle stability systems (ABS, ESP) were not considered in these studies. The influence of the delayed torque build-up at the electric motor, on the other hand, is considered to be rather minor.

[0017] In order to limit the design and dimensioning to the nominal axle torque and still ensure sufficient safety against all misuse loads, a system is specified that actively counteracts the torque peaks or interrupts the power path and thus reliably prevents the introduction of undesirable load peaks into the transmission mechanism.

[0018] According to the invention, this active peak load reduction is achieved in-situ through targeted interventions depending on the angular velocities of all rotating machine elements and electronic components, with only short latency times between detection, transmission, and actuation. A significant contributor to the overall latency is the detection and transmission of the wheel speed signals. This is usually done via a signal bus, such as the CAN bus in a vehicle. Since time delays of up to 300 ms can occur due to signal detection and transmission, and the sampling rate is often insufficient 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 to keep the signal delay time to a minimum, regardless of the respective vehicle architecture.

[0019] 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 the axis level. • a reduction in latency times. • Independent of the vehicle architecture such as data bus and wheel speed sensors.

[0020] 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 increased accuracy in the implementation of 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.

[0021] Further developments of the invention are specified in the dependent claims, the description and the accompanying drawings.

[0022] 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.

[0023] Preferably, the incremental encoder geometry on the transmission output gear is incorporated into the transmission output gear during the molding process of the transmission output gear. In another embodiment, the incremental encoder geometry is implemented as an insert, in particular as a plastic insert, in the transmission output gear.

[0024] Preferably, the incremental geometry is additionally configured as part of a conveying device for an oil circuit. The increments can serve as a guide and conveying device for the oil, particularly through suitable inclination.

[0025] Preferably, the active torque damping control of the transmission device, i.e., the prevention of a parasitic, externally acting power flow, can be achieved 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 disengaging a differential bevel gear from a sideshaft, preferably at or near a zero torque crossing. The active torque damping control can optionally also be achieved by activating a vehicle-mounted driving dynamics control system.

[0026] The active torque damping control preferably forms a closed control loop together with the speed detection device.

[0027] 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 of the vehicle, are required.

[0028] 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.

[0029] A method according to the invention for torque damping 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. It comprises, after detecting at least the rotational speed of the transmission output gear as an input variable, active torque damping, depending on the rotational speed of the transmission output gear determined by the rotational speed detection device, taking place by actively controlling the electric motor and / or by actively controlling a separating clutch. Optionally, a vehicle-side driving dynamics control system can also be activated depending on the rotational speed of the transmission output gear determined by the rotational speed detection device. Brief description of the drawings

[0030] The invention is described below by way of example with reference to the drawings. Fig. 1 is a schematic representation of a transmission device according to the invention. Fig. 2 is a schematic representation of another transmission device according to the invention. Fig. 3a is a rough schematic representation of a method according to the invention with a transmission device according to Fig. 1 or Fig. 2. Fig. 3b is a more detailed schematic representation of a method according to the invention with a transmission device according to Fig. 1 or Fig. 2. Fig. 4 is an exemplary curve 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 for torque damping according to the invention. Detailed description of the invention

[0031] In the Fig. 1 and Fig. 2 shows a transmission device according to the invention.

[0032] Fig. Figure 1 shows a two-stage eDrive system with an offset architecture. This consists of the electric motor EM, rolling bearings a, and 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, the final gear, at axle level, so that the axle speed corresponds to the speed of the transmission output gear e.

[0033] Using a suitable detection / counting instrument f and g, the actual speed of the transmission output gear e can be read instantly. This has the advantage that the signal can be directly integrated into the Electric Drive Unit (EDU) as the control unit h and can be used for active torque control or for the actuation of a DC separating clutch unit ( Fig. 2) necessary period of time can be granted.

[0034] Furthermore, it is possible to eliminate all downstream disturbances of the eDrive actual speed (e.g. sideshaft compliance, play in the differential and in the splines) and increase the accuracy.

[0035] Due to the virtually latency-free speed detection of the output, the control of an existing DC separating clutch unit can be carried out in order to specifically prevent the introduction of load peaks into the mechanics - see DC in Fig. 2.

[0036] For example, if the electric drive unit (EDU) h is not equipped with a DC separating clutch unit, the introduced parasitic load can be significantly reduced or completely eliminated by actively implementing targeted control interventions (=active torque adjustment) of the EM through 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, externally acting torque. The resulting differential torque is thus significantly lower than in the case without active damping.

[0037] The incremental geometry f can, for example, be integrated as a negative mold in a forging die or a casting die and introduced into the gear body of the transmission output gear e during the gear forming process without the need for additional or post-processing. Only a pickup or sensor g integrated into the housing, such as a Hall sensor, needs to sense the increments.

[0038] 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.

[0039] Furthermore, the functional extension of the incremental geometry f can be realized by a conveying device for the oil circuit. By appropriately tilting the increments, they can serve as a combined guide and conveying device for the oil.

[0040] By additionally integrating a passive drivetrain decoupling or damping element at a suitable location in the drivetrain and considering the corresponding parameters in the control loop, the power required by the electric motor to actively dampen torque peaks can be reduced. With precise knowledge of all parameters relevant to vibration behavior in the eDS system, such as backlash, mass moments of inertia, torsional stiffness, friction, and damping parameters, the closed control loop can be precisely mapped in the control and regulation software. The availability of the input and output speeds enables precise control intervention without relying on the quality of signals provided by the vehicle.

[0041] To Fig. 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, using 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 system ESC. When an external disturbance is detected, the control chain becomes active (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.

[0042] Fig. Figure 3b shows possible steps in a method V according to the invention, which forms a closed-loop control mode for active peak load reduction.

[0043] 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: |dn 2 / dt|>Limit?

[0044] If “No” N, step 2 follows: No action required, therefore no damping.

[0045] If "yes" Y, step 3 follows: Request for active peak load reduction. In step 4, a query is made: Is a change in the torque direction detectable? |n 1 / n 2 | > Limit?

[0046] If “yes” Y, the DC decoupling clutch is activated in step 5.

[0047] 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 |?

[0048] If “yes” Y, “Active Peak Load Damping” is activated in step 7, i.e. the electric motor EM for damping.

[0049] If “No” N, step 8 follows, a request for intervention by the active vehicle dynamics management (ESC).

[0050] Fig. 4 shows an example of a qualitative curve of the speed signals n measured at the transmission input shaft, i.e. at the electric motor EM, and at the transmission output shaft, i.e. at the axis A. EM and n A , where the speed n is given in rpm (y-axis) and the course 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 1A torque peak introduced by an external disturbance leads to a speed fluctuation at the gearbox output gear e. Due to the backlash and elasticity present in the system, a short-term 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 Fig. 4. If relative speed changes between the transmission output shaft and the transmission input shaft are detected, active control intervention is triggered immediately, and countermeasures are initiated within the time window Δt. If an action is taken to open the DC separating clutch unit, it must be fully released within the time window Δt (torque zero crossing).

[0051] 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. 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 undergoes a so-called "end-of-line test." Each finally assembled Electric Drive Unit (EDU) undergoes a defined test run to ensure compliance with 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 (stiffness, damping, backlash).Finally, the calculations are written to the Electric Control Unit (ECU) using the created look-up tables. During operation, the wheel speed is thus available in every operating state and can be used as a "virtual 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 known as a "resolver"—when controlling the EM torque at the wheel speed level using look-up tables, which can provide additional cost savings. List of reference symbols a rolling bearing 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 n 1 Pinion speed n 2Speed ​​of the transmission output gear n EM Speed ​​of the electric motor n A Axis speed EM electric motor ESC Electronic Stability Control, driving dynamics control system DC disconnect coupling ΔA0 speed difference without presence of a disturbance torque ΔA1 Speed ​​difference in the presence of a disturbance torque Δt time window 1 Query 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. is: |dn 2 / dt|>Limit? 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 separating clutch 6 Query whether there is sufficient power reserve of the electric motor EM: |Pact|<|Ppeak|? 7 Activation of “Active Peak Load Damping”, i.e. the electric motor EM for damping 8 Request for intervention by the active vehicle dynamics management (ESC) N No Y Yes

Claims

[1] A 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 (n2) of the transmission output gear (e) can be detected and wherein, depending on the speed (n2) of the transmission output gear (e) determined by the speed detection device, the active torque damping is carried out by the torque damping control of the control device (h), characterized bythat the speed detection device with which the speed (n2) of the transmission output gear (e) can be detected comprises a so-called “virtual sensor”, wherein the speed (n2) is determined by a computer model on the basis of the vibration behavior of a specific vehicle in which the transmission device is installed, said vibration behavior being known from an end-of-line test. [2] Transmission device according to claim 1, characterized by 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. [3] Transmission device according to at least one of the preceding claims, characterized by that the active torque damping control together with the speed detection device forms a closed control loop. [4] Transmission device according to at least one of the preceding claims, characterized by that the transmission device 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 dynamics control system (ESC), are required. [5] Transmission device according to at least one of the preceding claims, characterized by 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. [6] 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 by that after detecting at least the rotational speed (n2) of the transmission output gear (e) as an input variable, an active torque damping, depending on the rotational speed (n2) 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).

Images