Method for controlling an electric drive motor of a motor vehicle, control device for a drive motor and motor vehicle

Abstract

The invention relates to a method for controlling an electric drive motor of a motor vehicle, with a rotor shaft which is connected to an output shaft of the motor vehicle via a gear transmission (10), wherein in the method, during a load change of the drive motor, a torque (MZ) provided by the drive motor is adjusted by accelerating and decelerating the drive motor by a torque (MZ) provided by the drive motor in order to bridge a backlash (22) between teeth (16) of meshing gears (12, 14) during a change between the tensile flank (20) and the shear flank (18).

Description

[0001] The invention relates to a method for controlling an electric drive motor of a motor vehicle, a control device for a drive motor and a motor vehicle.

[0002] WO 2022 / 233535 A1 discloses a method for controlling an electric drive motor of a motor vehicle, the rotor shaft of which is connected to an output shaft of the motor vehicle by means of a gear transmission, for reducing transmission noise. During a load change of the drive motor before a flank change of the gear transmission, a torque surge of the drive motor is provided to adapt the joint rotational movement of the gears of the gear transmission. This torque surge is completed before the beginning of the flank change. The torque surge is specified by a deviation function, and this deviation function replaces or overlays the torque specification of an output torque curve of the drive motor provided for the load change for a surge duration between the start and end of the surge.

[0003] The object of the present invention is to provide a solution which enables a particularly fast flank change of a gear wheel of a transmission between a pulling flank and a pushing flank with particularly low noise generation.

[0004] This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0005] The invention relates to a method for controlling an electric drive motor of a motor vehicle. The electric drive motor is in particular part of an electric drive train of the motor vehicle and is designed to drive the motor vehicle using electrical energy. The electric drive motor can also be referred to as a traction motor. The motor vehicle is thus a purely electrically driven motor vehicle or a hybrid-electrically driven motor vehicle. The electric drive motor comprises a rotor shaft which is connected to an output shaft of the motor vehicle via a gear transmission. The electric drive motor can be permanently coupled to this gear transmission for torque transmission or can be coupled to or decoupled from one another, for example by means of a clutch or the like.The gear transmission may comprise a first gear and a second gear, which together form a gear stage arrangement. In other words, the first gear and the second gear may mesh directly with each other, whereby the gear stage arrangement then has a gear stage.

[0006] The method provides that, when the load of the drive motor changes, acceleration of the drive motor and deceleration of the drive motor are adjusted by a torque provided by the drive motor in order to bridge the backlash between the teeth of meshing gears when switching between the traction flank and the thrust flank. During the load change, a flank change of the meshing gears thus occurs. A flank change is understood to mean a transition of contact between the gears from one flank of an initially meshing tooth to the respective opposite flank of the subsequently meshing tooth of one of the gears.This flank change is usually subject to play, so that when the torque changes on one of the gears, an audible impact can occur when the new flank contact is formed. If the torque applied to the gears differs, this impact depends on the respective relative speed when passing through the play. A common rotary movement of two meshing gears is understood in particular to be the rotary movement that the two gears undergo dependently on one another, i.e. when they are in contact with one another, especially when no flank change is taking place. The method therefore does not merely apply a torque impact in one direction to the torque provided by the rotor shaft, but rather increases the torque provided by the rotor shaft from an initial value and then reduces it below this initial value.If a torque surge were to occur, the torque provided by the rotor shaft would simply be either increased or decreased, depending on the direction of the torque surge. However, the method according to the invention provides that the torque provided by the rotor shaft via the gear transmission for the output shaft is successively positive and negative during the period of the load change. The torque provided by the rotor shaft can first be negative and then positive, or first positive and then negative. The period of the load change corresponds to the time required to bridge the play between the teeth during the changeover. This play can also be referred to as the so-called tooth meshing play.

[0007] For example, it can be provided that the electric machine is towed along when the motor vehicle is moving, in particular because the motor vehicle is driven by an internal combustion engine or another electric machine. As a result of the pushing of the electric machine, the first gear assigned to the output shaft rests on a thrust flank of the second gear assigned to the rotor shaft. The second gear is set in rotation via this thrust flank. If the electric drive machine is now to be switched on and thus also used to drive the motor vehicle, a load change must be carried out in which the first gear is placed on the pulling flank of the second gear.An angle adjustment between the first gear and the second gear must therefore be adjusted to bridge the play between the thrust flank and the traction flank, thus switching from the thrust flank to the traction flank. If the vehicle is no longer to be driven by the electric motor, a further load change must be performed in the gear transmission, switching back from the traction flank to the thrust flank. The first gear should thus be adjusted from the engagement with the traction flank to the engagement with the thrust flank of the second gear.

[0008] To enable the adjustment between the traction flank and the thrust flank within a particularly short period of time, the torque provided by the electric motor is adjusted. This allows the backlash between the gears to be bridged particularly quickly by actively accelerating and decelerating the second gear.

[0009] In a possible further development of the invention, it is provided that if the teeth are switched from the pushing flank to the pulling flank for the load change, the drive motor is first accelerated and then decelerated. This means that if, during the load change, the first gear is to be brought from contact with the pushing flank to contact with the pulling flank, the second gear is first accelerated by providing the positive torque and then decelerated by providing the negative torque from the electric drive motor. This has the effect that the angular adjustment of the second gear relative to the first gear, which is necessary to bring the first gear from contact with the pushing flank to contact with the pulling flank, can be implemented particularly quickly. In addition, the deceleration of the second gear as a result of the provision of the negative torque brakes the second gear.This means that the second gear, starting from an initial speed during the load change, is first accelerated and then decelerated back to the initial speed. As a result, the relative speed of the teeth of the second gear to the teeth of the first gear is as low as possible at the moment the first gear is brought into contact with the pull flank of the second gear, thereby minimizing noise generated by the first gear striking the pull flank of the second gear.

[0010] In a further possible embodiment of the invention, it is provided that if the teeth are switched from the pulling flank to the pushing flank for the load change, the drive motor is first decelerated and then accelerated. This means that if the first gear is to be moved from the contact with the pulling flank to the contact with the pushing flank during the load change, the electric drive motor first provides a negative torque and then a positive torque. The negative torque provided by the electric drive motor causes the speed of the second gear to slow down, starting from an initial speed of the second gear. By slowing down the second gear, the play when switching from the pulling flank to the pushing flank is bridged particularly quickly.During the load change, following the deceleration of the electric drive motor, the electric drive motor is accelerated again, whereby a positive torque is applied to the second gear. As a result, the reduced speed of the second gear is increased again to the initial speed so that when the first gear engages the thrust flank of the second gear, relative movement between the gear teeth is as small as possible. This makes it particularly easy to prevent clattering as a result of the teeth of the first gear striking the thrust flanks of the teeth of the second gear. The described method therefore enables the play between the gears to be bridged particularly quickly and, in addition, the gears to engage one another particularly smoothly after the play has been bridged.

[0011] In the cases described above, in which the load change of the teeth takes place from the thrust flank to the traction flank or in which the load change of the teeth is switched from the traction flank to the thrust flank, the electric drive machine has the same direction of rotation in both cases, wherein in the first case the electric drive machine is first accelerated and then decelerated during the load change and in the second case the electric drive machine is first decelerated and then accelerated during the load change.

[0012] In a further possible embodiment of the invention, it is provided that the torque provided by the drive motor follows a sinusoidal curve between a positive torque range and a negative torque range during the load change. This means that the torque provided by the electric drive motor changes over the period of the load change according to the course of a sinusoidal curve. Over the period of the load change, the torque follows a course that corresponds exactly to a sinusoidal wave with a negative amplitude and a positive amplitude. The wavelength of the sinusoidal torque curve thus corresponds to the period of time required to carry out the load change and thus bridge the play between the tension flank and the thrust flank.A sine function is thus imposed on the torque provided by the electric drive motor, whereby the output torque provided by the electric drive motor before the load change and the torque provided by the electric drive motor immediately after the end of the load change are the same. During the load change, the torque of the electric drive motor is increased starting from the output torque according to a sinusoidal curve, reduced below the output torque, and adjusted to the output torque at the end of the load change. Changing the torque provided by the electric drive motor during the load change according to the shape of the sinusoidal curve enables the backlash between the gears to be bridged as quickly and easily as possible.The process therefore not only applies a torque pulse in one direction, but also imposes a sinusoidal curve on the torque, so that the torque provided by the drive motor is both increased and decreased.

[0013] In this context, it can be provided, in particular, that an amplitude level, a phase, and a wavelength of the sinusoidal curve are selected depending on a predetermined time period for the load change. In other words, the sinusoidal curve of the torque provided by the electric drive motor is selected such that the load change can be carried out within the predetermined time period. If, for example, it is specified that the load change should occur within 10 milliseconds and thus the backlash between the gears should be bridged within 10 milliseconds, then the sinusoidal curve of the torque provided by the electric drive motor is adjusted in terms of amplitude level and wavelength such that this time specification for the load change can be met.The phase specification for the sinusoidal curve is selected depending on whether the changeover is from the tension flank to the shear flank or from the shear flank to the tension flank. In particular, the phase specification can be selected as 0 or 0.5 times the wavelength, and thus the time period. In particular, it is intended that 0 is selected as the phase specification for the sinusoidal curve for the load change from the shear flank to the tension flank, and half the wavelength is selected as the phase specification for the sinusoidal curve for the changeover from the tension flank to the shear flank.

[0014] The method enables particularly convenient gear flank changes in the shortest possible time. By specifying the changeover time for the load change, the sinusoidal curve of the torque to be set for the electric drive motor is determined. The method is thus particularly designed to allow a time specification of how quickly the gear flank change should occur. In addition, the differential speed when the respective gear flanks meet can be reduced.

[0015] By adjusting the sinusoidal curve of the torque provided by the electric drive unit, it is possible to ensure that the load change occurs reliably within the specified time and, moreover, that the load change can be implemented particularly quickly. Furthermore, the risk of noisy contact between the gears at the end of the load change can be minimized.

[0016] In a further possible embodiment of the invention, it is provided that a speed of a change in the torque provided by the drive machine depends on a maximum possible torque gradient of the drive machine. A maximum torque gradient of the electric drive machine is thus used. In particular, the course of the sine function is set according to the maximum possible torque gradient of the electric machine. The maximum torque degree of the electric drive machine characterizes a steepest possible course of the change in torque, in particular the maximum possible gradient or the maximum possible increase in the torque of the electric machine. The greater the maximum possible torque gradient of the electric machine, the faster or more strongly the electric drive machine can be accelerated or decelerated.The greater the maximum possible torque gradient of the electric drive motor, the higher the respective amplitude of the sinusoidal curve can be selected, or the shorter the respective wavelength of the sinusoidal curve can be selected for the torque provided by the electric drive motor. This means that the higher the maximum possible torque gradient of the electric drive motor, the shorter the minimum time required for the load change. The higher the maximum possible torque gradient of the electric drive motor, the faster the load change can be carried out. By selecting the sinusoidal curve of the torque change of the electric drive motor in such a way that the maximum possible torque gradient of the drive motor is utilized, the full potential of the electric drive motor can be utilized with regard to the speed of the load change to be carried out.

[0017] The invention further relates to a control device for an electric drive motor of a motor vehicle. The control device is configured to control the electric drive motor using a method as already described in connection with the method according to the invention. In particular, the torque provided by the electric drive motor can be adjusted by controlling the electric drive motor. The control device thus enables a load change between a traction flank and a thrust flank to be implemented particularly quickly and, at the same time, particularly quietly in the gear transmission.

[0018] The invention further relates to a motor vehicle having an electric drive motor and having a control device as already described in connection with the control device according to the invention. The control device is configured to control the electric drive motor of the motor vehicle using a method as already described in connection with the method according to the invention. The motor vehicle is, in particular, a motor vehicle, in particular a passenger car. In particular, the motor vehicle is designed as a fully electrified motor vehicle or as a hybrid electrified motor vehicle.

[0019] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0020] The drawing shows: Fig. 1 is a schematic side view of a gear transmission, wherein a first gear abuts a thrust flank of a second gear; Fig. 2 a schematic side view of the gear transmission according to Fig. 1, wherein the first gear abuts a pulling flank of the second gear; Fig. 3 a partial schematic sectional view of the gear transmission with the first gear and the second gear; Fig. 4 is a graph illustrating a change in torque provided by an electric drive machine during a load change; Fig. 5 a graph showing a curve of the rotational speed of the second gear during the load change in relation to an output rotational speed; and Fig. 6 a graph showing a course of the angular offset of the second gear to the first gear during the load change.

[0021] In the figures, identical and functionally identical elements are provided with the same reference numerals.

[0022] In the Fig. 1 and Fig. 2 shows a gear transmission 10 of an electric drive train of a motor vehicle. In addition to the gear transmission 10, the electric drive train comprises an electric drive motor which is designed to provide a torque for driving the motor vehicle. The drive train further comprises an output shaft which is connected to wheels of the motor vehicle in a torque-transmitting manner. This means that the torque provided by the electric drive motor is provided to the output shaft via the gear transmission 10. The gear transmission 10 is designed to translate the torque provided by the electric drive motor. The output shaft is connected to a first gear 12 in a torque-transmitting manner. The electric drive motor is connected to a second gear 14 of the gear transmission 10 in a torque-transmitting manner.In particular, the second gear 14 can be connected in a rotationally fixed manner to a rotor shaft of the electric drive motor. The first gear 12 and the second gear 14 mesh with each other. During overrun of the electric drive train of the motor vehicle, a torque M is transmitted via the first gear 12. Sintroduced. The second gear 14 is thus pushed along by the first gear 12. In this overrun mode, the motor vehicle is not driven by the electric drive motor. In overrun mode, the motor vehicle can be driven, for example, by an internal combustion engine or by another electric drive motor. In particular, the electric drive motor can be pushed along via the gear transmission 10 in overrun mode. In overrun mode, the respective teeth 16 of the first gear 12 rest against respective thrust flanks 18 of the second gear 14. Power is therefore transmitted within the gear transmission 10 via the thrust flanks 18 in overrun mode. For reasons of clarity, only individual teeth 16 of the respective gears 12, 14 are provided with the associated reference numerals.

[0023] In Fig. Figure 2 shows the gear transmission 10 in traction mode of the electric drive train. In this traction mode, the motor vehicle is driven by the electric drive motor. This means that a torque M Z into the gear transmission 10. The direction of rotation of the respective gears 12, 14 is for the Fig. 1 and the thrust operation shown in Fig. 2. In the pulling operation, the teeth 16 of the first gear 12 rest on the respective pulling flanks 20 of the teeth 16 of the second gear 14. In the pulling operation, the torque M Zvia the second gear 14 into the gear transmission 10, whereby the first gear 12 is driven by the second gear 14. In order to be able to switch from push operation to pull operation or to switch from pull operation to push operation, the teeth 16 of the first gear 12 must be adjusted between a contact with the respective push flanks 18 and a contact with the respective pull flanks 20.

[0024] As in Fig. 3, there is a play 22 between the gear wheels 12, 14, which can also be referred to as tooth engagement play. In order to switch between push operation and pull operation, this play 22 must be bridged. This means that in order to switch between push operation and pull operation, the angular position of the second gear wheel 14 with respect to a rotational axis of the second gear wheel 14 and a rotational direction of the second gear wheel 14 relative to the first gear wheel 12 are changed in order to bridge the play 22. In other words, the relative speed between the gear wheels 12, 14 must be changed in order to enable the teeth 16 of the first gear wheel 12 to be brought from the contact with the respective push flanks 18 to the contact with the respective pull flanks 20 or from the contact with the respective pull flanks 20 to the contact with the respective push flanks 18.

[0025] The gear transmission 10 is in Fig. 3 shows a section of the electric drive train in overrun mode. Here, the respective teeth 16 of the first gear 12 rest against the respective thrust flanks 18 of the teeth 16 of the second gear 14. In order to release the teeth 16 of the first gear 12 from the respective thrust flanks 18 of the respective teeth 16 of the second gear 14 and to bring them into contact with the respective tensile flanks 20 of the teeth 16 of the second gear 14, the play 22 must be overcome by adjusting the angular position of the second gear 14 with respect to the axis of rotation of the second gear 14 by changing the rotational speed. This bridging of the play 22 is also referred to herein as load change. During the load change, the clearance 22 between the teeth 16 of the meshing gears 12, 14 is bridged when switching between the pulling flank 20 and the pushing flank 18.This means that at the start 24 of the load change, the teeth 16 of the first gear 12 rest against the respective thrust flanks 18 of the teeth 16 of the second gear 14, and at the end 26 of the load change, they rest against the respective tension flanks 20 of the teeth 16 of the second gear 14. Alternatively, the teeth 16 of the first gear 12 rest against the tension flanks 20 of the teeth 16 of the second gear 14 at the start 24 of the load change, and against the respective thrust flanks 18 of the teeth 16 of the second gear 14 at the end 26 of the load change.

[0026] It is intended that the torque provided by the electric drive motor will be modified for the load change. Fig. 4, Fig. 5 and Fig. 6 shows the respective graphs for an exemplary load change explained below. Within the scope of the Fig. 4 to 6, the electric drive train is switched from overrun to traction mode. The graphs show the respective parameters from the start of the load change 24 to the end of the load change 26. Fig. 4 shows the torque provided by the electric drive motor.

[0027] In other words, in Fig. 4 the output torque 28 of the electric machine of 0 Nm is shown on the ordinate. Time is plotted on the abscissa. In Fig. 5, for the same load change, the time is also plotted on the abscissa and the speed of the second gear 14 is shown on the ordinate relative to an output speed 30. In other words, the value 0 along the ordinate describes the output speed 30 of the second gear 14. In Fig. 6 an angle by which the second gear 14 is adjusted about its axis of rotation relative to an initial angular position 32, wherein the second gear 14 has the initial angular position 32 at the start of the load change 24, as well as the time are plotted.

[0028] As in Fig. 4, the torque provided by the electric drive unit during the load change, and thus from the start of the load change 24 to the end of the load change 26, follows a sinusoidal curve. This means that during the load change, the electric drive unit first provides a positive torque and then a negative torque. Thus, the electric drive unit is first accelerated and then decelerated for the load change. As shown in Fig. 5, the speed of the second gear 14 increases from the initial speed 30 over the load change and finally decreases back to the initial speed 30. This means that the second gear 14 is accelerated from its initial speed 30, which corresponds to the value 0 on the ordinate, and then decelerated back to its initial speed 30.

[0029] In this case, the speed change of the second gear 14 during the load change, starting from the initial speed 30, at least essentially follows a cosine function with an offset. This allows the gap 22 to be bridged particularly quickly by accelerating the second gear 14. After acceleration, the second gear 14 is decelerated again to prevent a clearly audible impact of the teeth 16 of the second gear 14 against the teeth 16 of the first gear 12.

[0030] In Fig. Figure 6 shows the angle adjustment of the second gear 14 relative to an initial angle position 32 of the second gear 14 at the beginning of the load change over time and thus over the course of the load change. The gradient of the curve shows that at the beginning of the load change, the angle of the second gear 14 is adjusted slowly, then the angle of the second gear 14 is adjusted more quickly in comparison, and subsequently the remaining angle adjustment of the second gear 14 is again slower.

[0031] The described method enables particularly rapid switching between overrun and pull operation. In particular, a time period can be specified within which the load change is to be carried out. Depending on this specified time period, the sinusoidal curve of the torque provided by the electric drive motor can in turn be selected. In particular, an amplitude level, a phase and an angular length of the sinusoidal curve can be adjusted such that the load change can be carried out within the specified time period. In order to enable the shortest possible time period for the load change, the speed of the change in the torque provided by the drive motor and thus the course of the sinusoidal curve can be selected depending on a maximum possible torque gradient of the drive motor.In other words, the shape of the sinusoidal curve is selected such that the maximum possible torque gradient of the electric drive motor is utilized, in particular by achieving the maximum possible torque gradient of the electric drive motor during load changes when the torque changes according to the sinusoidal shape of the curve. The torque provided by the drive motor follows the sinusoidal curve between the positive torque range and the negative torque range during the load change.

[0032] If, instead of as in the example described, it is provided that for the load change the teeth 16 of the first gear 12 are brought from the contact with the traction flank 20 into contact with the thrust flank 18 of the teeth 16 of the second gear 14, then the electric drive motor is first decelerated and then accelerated. In particular, the torque provided by the drive motor follows the sinusoidal curve during this load change, wherein the torque first runs in the negative torque range and then runs in the positive torque range. In other words, the torque provided by the electric drive motor during this second alternative load change follows a sinusoidal curve, which in comparison to the Fig. 5 is mirrored on the abscissa or multiplied by -1.

[0033] Within the scope of the method, a pre-control of a torque curve of the torque provided by the electric drive motor takes place in order to be able to move the second gear 14, which is connected to the electric drive motor in a rotationally fixed manner, through a specific angle. The described method enables the second gear 14 driven by the electric drive motor to be adjusted particularly quickly between the pulling flank 20 and the pushing flank 18. With a simple linear torque curve of the torque provided by the electric drive motor, a differential speed between the second gear 14 and the first gear 12 when the teeth 16 of the first gear 12 impact the pushing flank 18 or the pulling flank 20 of the second gear 14 will be not equal to 0.Furthermore, with the linear torque curve, the maximum available dynamics of the electric drive motor would not be used to travel through the play 22. By specifying the behavior of the electric drive motor not via the linear torque curve, but via the sinusoidal torque curve, both the impact speed of the teeth 16 of the first gear 12 and the second gear 14 at the load change end 26 can be minimized and the dynamics of the electric drive motor can be utilized particularly well.

[0034] Overall, the invention shows how a system change function can be implemented, in which a pre-controlled passage through a play 22 of the gear transmission 10 takes place when the sign changes. List of reference symbols 10 gear transmissions 12 first gear 14 second gear 16 tooth 18 Thrust flank 20 train flank 22 game 24 Load change start 26 Load change end 28 Output torque 30 Output speed 32 Initial angle position QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] WO 2022 / 233535 A1

[0002]

Claims

[1] Method for controlling an electric drive machine of a motor vehicle, having a rotor shaft which is connected to an output shaft of the motor vehicle via a gear transmission (10), wherein in the method, in the event of a load change of the drive machine, an acceleration of the drive machine and a deceleration of the drive machine are effected by a torque (M Z ) is set to bridge a play (22) between teeth (16) of meshing gears (12, 14) when switching between the pulling flank (20) and the pushing flank (18). [2] Method according to claim 1, characterized by that if the teeth (16) are switched from the thrust flank (18) to the pull flank (20) for the load change, the drive machine is first accelerated and then decelerated. [3] Method according to claim 1 or 2, characterized bythat if the teeth (16) are switched from the pulling flank (20) to the pushing flank (18) for the load change, the drive machine is first decelerated and then accelerated. [4] Method according to one of the preceding claims, characterized by that the torque provided by the prime mover (M Z ) follows a sinusoidal curve between a positive torque range and a negative torque range during the load change. [5] Method according to claim 4, characterized by that an amplitude level, a phase and a wavelength of the sinusoidal waveform are selected depending on a predetermined time period for the load change. [6] Method according to one of the preceding claims, characterized by that a speed of change of the torque provided by the prime mover (M Z ) depending on a maximum possible torque gradient of the drive machine. [7] Control device for an electric drive machine of a motor vehicle, which is designed to control the electric drive machine in a method according to one of the preceding claims. [8] Motor vehicle, with an electric drive machine and with a control device according to claim 7.

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