Learning method of shift drum in hybrid powertrain

Abstract

The invention relates to a method for learning a shift drum (100) in a hybrid powertrain (10), wherein the hybrid powertrain (10) has a first drive engine in the form of an internal combustion engine (12) and a second drive engine in the form of an electric motor (16) and a transmission device (18), wherein the transmission device can be connected to the first drive engine (12) via a shift element (K0), and the transmission device can be connected to the second drive engine (12) or is already connected to the second drive engine, wherein the transmission device (18) comprises an input shaft (26) and an output shaft (34) and a plurality of gears (40, 46, 56) arranged therebetween, wherein the gears are designed to be shiftable via associated shift elements (K1, K2, K4), wherein the shift elements (K0, K1, K2, K4) are shifted via a shift drum (100) that can be rotated 360 degrees, and the method comprises the following method steps: rotating the shift drum (100) into a first shift state, wherein the first shift state is connected to the first shift state; The invention relates to a transmission device (18) in a neutral position; generating a low speed by means of the electric motor (16), thereby generating a speed difference on at least two shifting elements (K0, K2) of the transmission device (18); rotating the shift drum (100) in a first rotational direction into a second shifting state, wherein the first shifting element (K0) is switched at the speed difference, so that the electric motor (16) is suddenly braked to zero, wherein a speed signal of the electric motor (16) is generated and the speed signal is associated with a first reference position / rotation angle as a virtual end stop; rotating the shift drum (100) back into the first shifting state; and rotating the shift drum (100) in a second rotational direction into another shifting state, wherein the second shifting element (K2) is switched at the speed difference, so that the electric motor (16) is suddenly braked to zero, wherein a speed signal of the electric motor (16) is generated and the speed signal is associated with a second reference position / rotation angle as a virtual end stop.

Description

Technical Field

[0001] The invention relates to a method for learning a shift drum in a hybrid powertrain. Background Art

[0002] Hybrid powertrains for motor vehicles have become popular in recent years. Hybrid powertrains can be implemented in different ways.

[0003] One example is a so-called series hybrid powertrain, in which the output of the internal combustion engine is connected to a generator, in which the output of the hybrid powertrain is connected to an electric motor, and in which the electric motor and the generator are connected to a common battery.

[0004] A parallel hybrid powertrain can be used to transmit the drive power of an internal combustion engine and the drive power of an electric motor to a driven device. In some cases, the electric machine is arranged around a crankshaft, and the crankshaft can be connected to the driven device via a starting clutch, more precisely, usually via a multi-speed transmission.

[0005] Hybrid powertrains are generally known (split-axle), in which an internal combustion engine drives one axle of the vehicle and an electric machine drives another axle of the vehicle.

[0006] Furthermore, parallel hybrid powertrains with a dual clutch transmission are known, in which the electric machine can be connected to the input of one of the sub-transmissions or to the output of the dual clutch transmission. The use of a dual clutch transmission allows gear changes to be made without interrupting traction.

[0007] The transmission device has a plurality of shifting clutches for setting up different gears. The shifting clutches are used to bring the wheel set into the power flow (in this case, the loose wheel of the wheel set is connected to the associated shaft). The shifting clutches are actuated, for example, via a shifting device including a shift drum. The rotation angle of the shift drum must be known exactly.

[0008] The shift drum and the method for referencing the rotational position of the shift drum are known in principle. In this case, the shift drum is usually formed with a so-called end stop, wherein the position sensor can detect the corresponding angular position of the end stop.

[0009] Document WO 2015 / 149797 A1 discloses, for example, an operating device for operating a transmission, which has a rotatable shift drum, wherein an end stop connected to the shift drum in a rotationally fixed manner acts together with a signaling device, so that a position signal can be generated when the signaling device and the end stop are moved relative to each other in a specific rotational position of the shift drum. The position signal can be generated by changing the mechanical resistance of the driving force of the drive motor in a specific rotational position.

[0010] From EP 1 286 088 A1 it is known to fasten a magnetic ring on a shift drum, said magnetic ring being designed for detecting the rotational position of the respective shift drum by means of a suitable sensor.

[0011] As mentioned above, for the reference rotational position, a rotating end stop can be integrated into the shift drum. However, in this case, the rotatability of the shift drum is limited. Wide and solid stops can partially significantly reduce the available rotation angle of the shift drum.

[0012] In known shift drum arrangements with a stop element that is firmly connected to the shift drum body, the maximum rotatability of the shift drum body results from 360° minus the circumferential angle of the stop element and minus the circumferential angle of a reference element, which can be, for example, an element fixed to the housing, such as a housing stop element. If, for example, the stop element extends over 35° and if the housing stop element also extends over 35°, the maximum rotation angle in the prior art is only 290°.

[0013] In particular, the above-mentioned hybridization of the transmission creates new challenges for the shifting device. In certain cases, it is advantageous if the shifting drum can be rotated arbitrarily / continuously in both directions of rotation.

[0014] If the shift drum arrangement requires a rotation of more than 360°, the methods known from the prior art for learning a shift drum which requires an end stop are not feasible in this way. Summary of the invention

[0015] Against this background, the object of the present invention is to provide a method for learning a shift drum in a hybrid drive train, which method can be used in a shift drum which can be rotated continuously in both directions of rotation.

[0016] 14. The invention relates to a method for learning a shift drum in a hybrid powertrain, wherein the hybrid powertrain comprises a first drive engine in the form of an internal combustion engine and a second drive engine in the form of an electric motor, and a transmission device, wherein the transmission device can be connected to the first drive engine via a shift element, and the transmission device can be connected to the second drive engine or is already connected to the second drive engine, wherein the transmission device comprises a transmission input shaft and a transmission output shaft and a plurality of gear stages in the form of wheel sets arranged therebetween, wherein the gear stages are designed to be shiftable via associated shift elements, wherein the shift elements are shifted via at least one shift device, wherein the shift device comprises a shift drum, and wherein the at least one shift drum comprises a shift drum body, wherein the shift drum body is continuously rotatable about a shift drum axis in a first and a second direction of rotation and has a circumferential shift contour extending on the circumference of an outer surface, wherein the method comprises the following method steps:

[0017] - rotating the shift drum into a first shifting state, which corresponds to a neutral position of the transmission device,

[0018] - generating a low rotational speed by means of the electric machine, thereby generating a rotational speed difference at at least two shifting elements of the transmission device,

[0019] - rotating the shift drum in a first rotational direction into a second shifting state, wherein the first shifting element is switched at the rotational speed difference so that the electric machine is braked suddenly to zero, wherein a rotational speed signal of the electric machine is generated and associated with a first reference position / rotational angle as a virtual end stop,

[0020] - turning the shift drum back into the first shift state,

[0021] - generating a low rotational speed by means of the electric machine, thereby generating a rotational speed difference at at least two shifting elements of the transmission device; and

[0022] - Rotating the shift drum in a second rotational direction into a further shifting state, wherein the second shifting element is switched at the speed difference so that the electric motor is braked suddenly to zero, wherein a speed signal of the electric motor is generated and associated with a second reference position / rotation angle as a virtual end stop.

[0023] By means of the above-described method for learning a shift drum, a virtual end stop in a continuously rotatable shift drum can be determined in a simple manner for the purpose of a reference shift angle.

[0024] This is possible because starting from a neutral position of the transmission device of the hybrid drive corresponding to the first shifting state of the shift drum, a low rotational speed is generated by means of the electric machine, thereby generating a rotational speed difference at at least two shifting elements of the transmission device.

[0025] Subsequently, in a further method step, the shift drum is rotated in the first rotational direction into a further shifting state and the first shifting element is switched with a speed difference so that the electric machine is braked abruptly to zero, a speed signal of the electric machine being generated and associated with a first reference position as a virtual end stop.

[0026] In a further method step, the shift drum is thereby rotated back into the neutral position.

[0027] The low rotational speed is then generated again with the aid of the electric motor.

[0028] In a final method step, the shift drum is rotated in a second rotational direction into a further shifting state and the second shifting element is switched with a speed difference so that the electric machine is braked abruptly to zero, wherein a speed signal of the electric machine is generated and associated with a second reference position as a virtual end stop. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the present invention are shown in the drawings and explained in detail in the following description. The drawings show:

[0030] Figure 1 A schematic diagram of a hybrid drivetrain of a motor vehicle is shown, wherein the hybrid drivetrain is designed to carry out the method according to the invention.

[0031] Figure 2 View showing a portion of the shift drum

[0032] Figure 3a-3d The matrix shows the different shifting states of the clutches K0 and K2 when the shift drum rotates in the first rotational direction.

[0033] Figure 4 A schematic diagram showing a shift drum with different shift states S1 - S4 ; and

[0034] Figure 5a-5d The method steps for carrying out the method according to the invention are shown in schematic form. DETAILED DESCRIPTION

[0035] exist Figure 1 A hybrid powertrain for a motor vehicle is shown in schematic form in FIG. 2 and is generally indicated by 10 .

[0036] The hybrid drive train 10 has a first drive machine in the form of an internal combustion engine 12 . The internal combustion engine 12 can be connected to a starter 14 . The hybrid drive train 10 also includes a second drive machine in the form of an electric machine 16 .

[0037] The hybrid drivetrain 10 further includes a transmission device 18 which is connected to the internal combustion engine 12 and the electric machine 16 .

[0038] The transmission device 18 has a transmission input shaft 26. The end region of the transmission input shaft 26 comprises a hollow shaft 54 ​​mounted on the transmission input shaft 26. The connection between the transmission input shaft 26 and the hollow shaft 54 ​​rotatably mounted on the transmission input shaft can be established via the shifting device K4 as will be described in detail below.

[0039] In addition, the input element 28 of the flywheel 32 (output shaft of the internal combustion engine) is connected to the crankshaft of the internal combustion engine 12. The output element 30 of the flywheel 32 can be connected to the transmission input shaft 26 via the shift element K0, which can be configured as a dog clutch. The shift element K0 can occupy two shift positions. The first shift position is a neutral position, in which no connection is established between the internal combustion engine 12 and the transmission input shaft 26. The second shift position is a position in which a connection is established between the internal combustion engine 12 and the transmission input shaft 26. The shifting of the shift element K0 is shown by the double arrow PF0.

[0040] The transmission device 18 also has a transmission output shaft 34 which is oriented in a parallel and offset manner relative to the transmission input shaft 26 .

[0041] On the output side, the transmission device 18 is connected to the differential 2, by means of which the drive power can be distributed to the driven wheels 22L, 22R. For this purpose, a driven gear 36 is fixed at the end to the transmission output shaft 34, which driven gear is engaged with a differential gear 38. The differential gear 38 is connected to the differential case of the differential 20 in a rotationally fixed manner.

[0042] The transmission arrangement 18 comprises three gear stages which, as described below, are formed via three gear sets.

[0043] The transmission input shaft 26 and the transmission output shaft 34 are connected to each other via a first wheel set 40, which comprises a fixed wheel 42 supported on the transmission input shaft 26 and a loose wheel 44 connected to the transmission output shaft 34. The teeth of the loose wheel 44 meshingly engage with the teeth of the fixed wheel 42. The first wheel set 40 is associated with the forward gear 1, which forms the lowest forward gear of the transmission device 18.

[0044] The transmission input shaft 26 is also connected to the transmission output shaft 34 via a second wheel set 46, wherein the second wheel set 46 has a fixed wheel 48 rotatably supported on the transmission input shaft 26 and a movable wheel 50 fixed to the transmission output shaft 34. The teeth of the movable wheel 48 meshingly engage with the teeth of the fixed wheel 50. The second wheel set 46 is associated with the forward gear 3.

[0045] For the purpose of establishing a rotationally fixed connection of the loose gear 44 or the loose gear 50, the shifting element K1 is arranged between these two loose gears on the transmission output shaft 34. The shifting element K1 can assume the following three shifting positions.

[0046] A neutral position, in which neither of the two loose wheels 44, 50 is connected in a rotationally fixed manner to the transmission output shaft 34. A shift position, in which the shift element K1 is shifted into a position displaced axially to the right, thereby establishing a rotationally fixed connection between the loose wheel 44 and the transmission output shaft 34. The transmission input shaft 26 is thus connected to the transmission output shaft 34 via the first wheel set 40 and an optional torque transmission path is realized.

[0047] There is also a shift position in which the shift element K1 is shifted into a position displaced axially to the left, thereby establishing a rotationally fixed connection between the loose wheel 50 and the transmission output shaft 34. The transmission input shaft 26 is thus connected to the transmission output shaft 34 via the second wheel set 46. The axial displacement of the shift element K1 is indicated by the double arrow PF1. The shift element K1 is a double-sided positive clutch. Since its embodiment is well known to those skilled in the art, no further explanation is given on this point. The shift element is usually designed as a synchronization unit.

[0048] In this context, the term connection should mean that drive power can be transmitted via the connection. Thus, the connection can be a connection that is possible (for example, can be produced via a shifting clutch), but can also be a connection that, for example, places the connected elements at a fixed speed ratio.

[0049] When the shift element K0 is adjusted to the second shift position, internal combustion engine operation can be established by means of the first wheel set 40, wherein forward gear 1 is engaged. Alternatively, driving operation by means of the internal combustion engine 12 can be established via the shift element K0, wherein the second wheel set 46 is switched into the power flow in order to engage forward gear 3.

[0050] The transmission input shaft 26 can be connected to the hollow shaft 54 ​​via a bridge clutch BR.

[0051] The transmission device 18 also includes a superposition gear set in the form of a planetary transmission 64. Such planetary transmissions are known in principle and will not be described in detail in this regard. The planetary transmission essentially comprises a ring gear 66, planetary gears 83 supported on a planet carrier, and a sun gear 82.

[0052] The sun gear 82 , which serves as a first input element of the planetary transmission 64 , is connected to the hollow shaft 54 ​​in a rotationally fixed manner.

[0053] A ring gear 66 as a second input element is connected to a hollow shaft section 68 arranged at the end, wherein the hollow shaft section 68 is designed coaxially with the transmission input shaft 26 and is rotatable relative to the transmission input shaft 26 .

[0054] The planetary gears 83 are mounted on a planet carrier which forms a further input element.

[0055] The first loose wheel 58 of the third wheel set 56 is rotatably supported on the planet carrier. The third wheel set 56 also has a second loose wheel 60 rotatably supported on the transmission output shaft 34. The third wheel set 56 forms a second gear.

[0056] The first loose gear 58 can be coupled in a rotationally fixed manner to the hollow shaft 54 ​​by means of a lockup clutch BL. The second loose gear 60 can be coupled in a rotationally fixed manner to the transmission output shaft 34 by means of a shifting element K2. The shifting element K2 can assume the following two shifting positions.

[0057] A neutral position, in which the loose gear 60 is rotatably supported on the transmission output shaft 34. A second shift position, in which the shift element K2 is shifted into a position displaced axially to the left, thereby establishing a rotationally fixed connection between the second loose gear 60 and the transmission output shaft 34. The transmission input shaft 26 or the hollow shaft 54 ​​can thus be connected to the transmission output shaft 34 via the third wheel set 56 and a further optional torque transmission path is realized.

[0058] The axial displacement of the shifting element K2 is indicated by the arrow PF2. The shifting element K2 is a one-sided positive-locking clutch.

[0059] The bridge clutch and the lockup clutch are integrated in a shifting device K4 which has three shifting positions and can be actuated by means of a single operating element, for example a single shift sleeve.

[0060] In the first shift position in which the shift device K4 is shifted to the left, the lockup clutch BL is closed and the bridge clutch BR is open. As a result, the first loose gear 58 is coupled to the planet carrier in a rotationally fixed manner and the connection to the transmission input shaft 26 is disconnected. The planetary transmission 64 is in a locked state.

[0061] In the second position of the shift device K4 , which is shifted to the right, the bridge clutch BR is closed and the lockup clutch BL is open. As a result, the first loose gear 58 is rotatably supported on the planet carrier and the hollow shaft 54 ​​is connected to the transmission input shaft 26 in a rotationally fixed manner.

[0062] In addition, the shifting device K4 can be used to set up an intermediate shifting position. In the intermediate shifting position, the locking clutch and the bridge clutch are closed. In this case, the planetary transmission 64 is in the locked position. In addition, a connection is established between the hollow shaft 54 ​​and the transmission input shaft 26.

[0063] The hollow shaft section 68 is coupled to the electric motor 16 via a gear stage 70. The gear stage 70 has a first gear 72 which is arranged rotationally fixed on the hollow shaft section 68 and a second gear 74 which meshes with the first gear 72. The second gear 74 meshes with a drive pinion 76 of the electric motor 16.

[0064] The second gear wheel 74 is rotatably mounted on an intermediate shaft 78 which is oriented coaxially offset relative to the transmission input shaft 26 and preferably also coaxially offset relative to the transmission output shaft 34 .

[0065] The electric machine 16 has a machine shaft 80 which is oriented coaxially with the drive pinion 76 and is connected thereto in a rotationally fixed manner. The machine shaft 80 is offset in parallel with respect to the transmission input shaft 26 and the transmission output shaft 34 .

[0066] As already discussed above, the shifting elements K0 , K1 and K2 as well as the shifting device K4 are shifted into the shifting positions by means of a shift sleeve.

[0067] In order to axially move the shift sleeves and thus shift the shift sleeves, the transmission device 18 comprises a shifting device with a rotatably mounted shift drum. In the illustrated embodiment which is suitable for carrying out the method according to the invention, Figure 2 The shift drum 100 shown in FIG. 1 shifts the two shift elements K0 and K2 .

[0068] The shift drum 100 has a shift drum body 102 which is mounted rotatably in two rotational directions about an axis of rotation 104 , more precisely rotatably relative to a housing. The housing can be, for example, a housing of the transmission device 18 .

[0069] The shift drum body 102 is connected to a drive element not shown. The drive element can be formed, for example, by a gear with an external toothing. For example, the external toothing of the drive element can engage with a drive pinion of a shift drum motor. For example, the shift drum motor can be an electric motor. Therefore, by operating the shift drum motor, the shift drum body 102 can rotate relative to the housing.

[0070] At least one shifting contour in the form of a shifting drum groove 106 is formed on the outer circumference of the shifting drum body 102, which can be seen from Figure 2 The shift drum groove 106 is formed continuously, so that any rotation of the shift drum 100 in both rotation directions over a rotation angle of 360 degrees is possible.

[0071] The shift fork, which also acts on the associated shift sleeve, engages accordingly in this shift drum groove 106. The shift fork has a slide which engages in the shift drum groove 106. In a suitable design of the shift drum groove 106, the rotation of the shift drum body 102 thus leads to an axial displacement of the shift rod and thus of the shift sleeve, which causes the shift elements K0 and K2 to be adjusted into the shift positions already described.

[0072] As according to Figure 3a-3d As can be seen in the matrix of the shifting states of the shifting elements K0 and K2, when the shift drum 100 rotates 360 degrees, four shifting states can be switched distributedly on the circumference in the order given below:

[0073] - Shifting state 1 (S1): shifting elements K0 and K2 are in neutral position ( Figure 3a ),

[0074] - Shift state 2 (S2): shift element K0 is in the second shift position (internal combustion engine 12 is coupled to transmission input shaft 26 via shift element K0) and K2 is in the neutral position ( Figure 3b ),

[0075] - Shifting state 3 (S3): shifting element K0 is in the second shifting position and shifting element K2 is in the second shifting position (the second loose gear 60 is connected to the transmission output shaft 34 in a rotationally fixed manner) ( Figure 3c )

[0076] - Shifting state 4 (S4): shifting element K0 is in the neutral position and shifting element K2 is in the second shifting position ( Figure 3d ).

[0077] When the shift drum 100 rotates further in the same rotational direction, the shift state 1 ( S1 ) is reached again after the shift state 4 ( S4 ).

[0078] According to the following Figure 5a-5d The schematic diagram of FIG. 1 describes in detail the method according to the invention for learning the shift drum 100 , ie for determining the rotation angle corresponding to the rotation angle 0 .

[0079] exist Figure 5a The initial position shown in the first method step is firstly the shifting state 1 (S1), in which the two shifting elements K0 and K2 are in the neutral position. The above-mentioned other shifting elements or shifting devices have the following shifting states:

[0080] - the shift device K4 is in the middle shift position,

[0081] - The shifting element K1 is in the neutral position.

[0082] In this state of the hybrid drive, the input element 28 , which corresponds to the output shaft of the internal combustion engine 12 , and the crankshaft have a rotational speed of 0. This is independent of the rotational speed of the machine shaft 80 of the electric machine 16 .

[0083] exist Figure 5bIn the subsequent method step shown in , the shift drum 100 is rotated further towards the shift state 2 (S2) in order to determine the first reference position at a low speed of the electric machine 16. This is precisely at the moment when the shift element K0 has overcome the freewheeling phase (Freiflug phase), which can be seen in the speed signal of the electric machine 16. The electric machine 16 remains stationary because it is now connected to the stationary internal combustion engine 12 via the shift element K0, the input shaft 26, the shift device K4 in the intermediate shift position, i.e., when the bridge clutch is engaged and the lockup clutch is engaged, via the superposition gear set, the gear stage 70, the drive pinion 76. This situation defines the first reference position in the corresponding rotation angle of the shift drum 100.

[0084] After the first reference position has been determined, the shift drum 100 is rotated back into the first shifting state S1 , which corresponds to the neutral gear as already explained in the first method step. Figure 5c Shown in.

[0085] Starting from the shifting state 1 (S1), the shift drum 100 is then rotated further into the shifting state 4 (S4) at a low rotation speed of the electric motor 16 to determine the second reference position. Figure 5d . It is precisely at the moment when the shifting element K2 has overcome the coasting phase that this can be seen in the rotational speed signal of the electric machine 16. The electric machine 16 remains stationary because it is now connected to the stationary transmission output shaft 34 via the shifting element K2, the third wheel set 56, the superposition wheel set, the gear stage 70 and the drive pinion 76. This situation defines a second reference position in the corresponding rotation angle of the shift drum 100.

[0086] The learning process is now concluded after the two reference positions corresponding to the virtual end stops in the associated rotational angle of the shift drum 100 have been determined and stored in the associated control unit.

[0087] Reference numerals list

[0088] 10 Hybrid Powertrain

[0089] 12 Internal combustion engine

[0090] 14 Starter

[0091] 16 Motor

[0092] 18 Transmission device

[0093] 20 Differential

[0094] 22R Driven wheels

[0095] 22L Driven wheels

[0096] 26 Transmission input shaft

[0097] 28 Input elements

[0098] 30 Output elements

[0099] 32 Inertia Flywheel

[0100] 34 Transmission output shaft

[0101] 36 Driven gear

[0102] 38 Differential gear

[0103] 40 First round group

[0104] 42 Fixed wheel

[0105] 44 Swivel wheels

[0106] 46 Second round group

[0107] 48 Fixed wheel

[0108] 50 Movable wheels

[0109] 56 Third wheel group

[0110] 58 First Activity Round

[0111] 60 Second active wheel

[0112] 54 Hollow shaft

[0113] 64 Planetary Transmission

[0114] 66 Ring gear

[0115] 68 Hollow shaft section

[0116] 70 gear stages

[0117] 72 First Gear

[0118] 74 Second gear

[0119] 76 Drive pinion

[0120] 80 Machine shaft

[0121] 83 Planetary gear

[0122] 82 Sun gear

[0123] 100 Shift drum

[0124] 102 Shift drum body

[0125] 104 Rotation axis

[0126] 106 Shift drum slot

[0127] BL Lock-up Clutch

[0128] BR Bridge Clutch

[0129] K0 Shift element

[0130] K1 shift element

[0131] K2 shift element

[0132] K4 gear shifter

Claims

1. A method for learning a shift drum (100) in a hybrid drivetrain (10), wherein the hybrid drivetrain (10) has a first drive engine in the form of an internal combustion engine (12) and a second drive engine in the form of an electric machine (16), and a transmission device (18), which can be connected to the first drive engine via a first shifting element (K0) and can be connected to the second drive engine or is already connected to the second drive engine, wherein the transmission device (18) comprises a transmission input shaft (26) and a transmission output shaft (34 ) and a plurality of gear stages in the form of wheel sets (40, 46, 56) arranged therebetween, the gear stages being designed to be shiftable via associated shift elements, wherein the shift elements are switched via at least one shift device, the shift device comprising a shift drum (100), and wherein the at least one shift drum (100) comprises a shift drum body (102), the shift drum body being continuously rotatable about a shift drum axis (104) in a first and a second direction of rotation and having a circumferential shift contour extending on the circumference of an outer surface, the method comprising the following method steps: - rotating the shift drum (100) into a first shift state (S1), which corresponds to a neutral position of the transmission device (18), - generating a low rotational speed by means of the electric machine (16), thereby generating a rotational speed difference at at least two shifting elements of the transmission device (18), - rotating the shift drum (100) in a first rotational direction into a second shifting state (S2), wherein the first shifting element (K0) is switched at the rotational speed difference so that the electric motor (16) is braked suddenly to zero, wherein a rotational speed signal of the electric motor (16) is generated and associated with a first reference position / rotational angle as a virtual end stop, - turning the shift drum (100) back into the first shift state (S1), - generating a low rotational speed by means of the electric machine (16), thereby generating a rotational speed difference at at least two shifting elements of the transmission device (18); and - rotating the shift drum (100) in a second rotational direction into another shifting state, wherein the second shifting element (K2) is switched at the speed difference so that the electric motor (16) is suddenly braked to zero, wherein a speed signal of the electric motor (16) is generated and associated with a second reference position / rotation angle as a virtual end stop.

2. The method for learning a shift drum (100) in a hybrid powertrain (10) according to claim 1, characterized in that: A shiftable connection is established between the internal combustion engine (12) and the transmission input shaft (26) via the first shifting element (K0), and the first shifting element (K0) can be shifted into the following shifting positions: a neutral position in which no connection is established between the internal combustion engine (12) and the transmission input shaft (26), a shift position in which the internal combustion engine (12) is connected to the transmission input shaft (26).

3. The method for learning a shift drum (100) in a hybrid powertrain (10) according to claim 2, characterized in that: The second shifting element (K2) is associated with a wheel set (56) forming a second gear, the wheel set comprising a loose wheel (60) supported on the transmission output shaft (34) and capable of being shifted into the following shifting positions by means of the second shifting element (K2): a neutral position in which the movable wheel (60) is rotatably mounted on the output shaft (34), - a shift position in which the second shift element (K2) is switched to an axially displaced position, thereby establishing a torsionally fixed connection between the loose wheel (60) and the transmission output shaft (34), whereby the transmission input shaft (26) can be connected to the transmission output shaft (34) via the wheel set (56) and another optional torque transmission path can be realized.

4. The method for learning a shift drum (100) in a hybrid powertrain (10) according to claim 1, characterized in that: When the shift drum (100) rotates 360 degrees in the first rotation direction, four shift states can be switched distributedly on the circumference according to the following sequence by means of the shift profile: - Shift state 1 (S1): the first and second shift elements (K0 and K2) are in the neutral position, - shifting state 2 (S2): the first shifting element (K0) is in a second shifting position and the second shifting element (K2) is in a neutral position, wherein in the second shifting position the internal combustion engine is coupled to the transmission input shaft (26), - shifting state 3 (S3): the first shifting element (K0) is in the second shifting position and the second shifting element (K2) is in the second shifting position, Shifting state 4 ( S4 ): the first shifting element ( K0 ) is in the neutral position and the second shifting element ( K2 ) is in the second shifting position.

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