Method for calibrating a selector drum

Abstract

A method for calibrating a selector drum in a dog-type transmission of a motor vehicle, wherein a tip-to-tip position (4) of the shift sleeve, in which dogs bear against a first or second idler gear without passing into associated recesses, such that the further rotation of the selector drum is blocked as a result, can occur during the axial movement of the shift sleeve, wherein, for calibrating the selector drum, with a first downshift angle (d1) being travelled, the selector drum is then rotated by means of the electric motor in a first step in the direction of a first end stop (2) of the selector drum until the selector drum blocks, wherein, with a first upshift angle (u1) being travelled, the selector drum is then rotated in a second step in the direction of a second end stop (3), lying opposite the first end stop (2), of the selector drum until the selector drum blocks, wherein the selector drum is then rotated into a first central position (m1) which is dependent on the first upshift angle (u1), wherein, at least in the presence of a continuation criterion, with a second downshift angle (d2) being travelled, the selector drum is then rotated in a third step in the direction of the first end stop (2) of the selector drum until the selector drum blocks, wherein, in a fourth step, with a second upshift angle (u2) being travelled, the selector drum is then rotated in the direction of the second end stop (3) of the selector drum until the selector drum blocks, wherein the selector drum is then rotated into a second central position (m2) which is dependent on the second downshift angle (d2) and on the second upshift angle (u2).

Description

[0001] Method for calibrating a switching drum

[0002] Field of invention

[0003] The present invention relates to a method for calibrating a shift drum and a motor vehicle with a control unit configured to perform such a method for calibrating the shift drum.

[0004] State of the art

[0005] It is known that a shift unit can be used to engage and disengage gears in a motor vehicle's transmission. This unit uses an electric motor to drive a shift drum into rotation and a mechanism to convert the rotational movement of the shift drum into an axial displacement, in particular an axially movable shift sleeve, thus engaging the desired gear position. For this purpose, the shift drum can have at least one guide groove, and a shift fork can move the shift sleeve axially according to the path of the guide groove. The shift drum and its guide groove can be designed such that, during operation, the shift drum only completes an angle of less than 360 degrees, i.e., not a full rotation, to change from one gear to another. The shift drum can then have fixed end stops to prevent further rotation beyond the desired angular range.

[0006] The position of the shift unit, in particular the current rotation angle of the shift drum, must be known in order to engage the gears. Here-

[0007] 2024P00095 WO 02.10.2025 BZ During production, the transmission is calibrated once. There are situations in which the shift drum position is lost during operation. Afterwards, a gear can no longer be reliably engaged or disengaged. If this occurs, the shift drum position is re-calibrated. For this purpose, the current position of the shift drum can be determined and / or a desired position of the shift drum, in particular a neutral mid-position between two gears, can be approached in a calibration process.

[0008] Typically, the position is determined by moving the shift drum to its end stop. However, with a dog-type gearbox, situations arise where the dog cannot be moved to its end stop because it is locked (so-called "tip-to-tip" position). Applying a differential speed would release this lock, but this may be undesirable, for example, for safety reasons. The position of the shift drum should be determinable even when the end stops cannot be reliably reached.

[0009] Summary of the invention

[0010] It is an object of the invention to provide a method for calibrating a shift drum in a motor vehicle with a dog-type transmission, enabling safe and reliable calibration of the shift drum. A further object is to provide a motor vehicle with a control unit configured to perform such a safe and reliable method for calibrating the shift drum.

[0011] The problem is solved by a method for calibrating a shift drum in a dog clutch transmission of a motor vehicle, wherein the dog clutch transmission has a first loose gear of a first gear stage and a second

[0012] 2024P00095 WO 02.10.2025 BZ comprises a loose gear of a second gear stage, which is axially fixed and rotatably mounted on a shaft, wherein a shift sleeve is arranged axially displaceably on the shaft between the first loose gear and the second loose gear in order to selectively connect either the first loose gear or the second loose gear to the shaft in a rotationally fixed manner by means of an engagement of claws in recesses associated with the claws, wherein the shift sleeve is axially displaced depending on a rotation angle of a shift drum, wherein the claw drive comprises an electric motor, wherein the shift drum is rotatable by means of the electric motor and thus the shift sleeve is axially movable on the shaft, wherein a tip-to-tip position of the shift sleeve, in which the claws bear against the first or second loose gear without entering the associated recesses, so that further rotation of the shift drum is blocked, can occur during the axial movement of the shift sleeve.wherein, to calibrate the switching drum, the switching drum is rotated by the electric motor in a first step towards a first end stop of the switching drum, covering a first downward angle, until the switching drum is blocked, wherein in a second step the switching drum is rotated in the direction of a second end stop of the switching drum opposite the first end stop, covering a first upward angle, until the switching drum is blocked, wherein the switching drum is then rotated to a first intermediate position dependent on the first upward angle, wherein then, at least if a continuation criterion is present, in a third step the switching drum is rotated in the direction of the first end stop of the switching drum, covering a second downward angle, until the switching drum is blocked, wherein in a fourth step the switching drum, covering a second upward angle,is rotated in the direction of the second end stop of the switching drum until the switching drum is blocked, after which the switching drum is moved into one of the second,

[0013] 2024P00095 WO 02.10.2025 BZ Down angle and second middle position dependent on the second up angle is rotated.

[0014] According to the invention, it is thus possible to move the shift drum to a neutral position, even if, in a dog clutch, a blockage due to a tip-to-tip position cannot be distinguished from a blockage at an end stop of the shift drum, and even if a tip-to-tip situation cannot or should not be resolved by rotating the gears relative to each other. For example, such a method can also be carried out when the vehicle and / or the drive shaft of the dog clutch are stationary, and can also be performed with symmetrically constructed dog clutches. However, the invention is also applicable to non-symmetrical systems in order to simplify and / or make calibration more reliable.

[0015] Four potential stops at blockages are to be expected: the respective end stops at the bottom and top, as well as the respective tip-to-tip blockage positions.

[0016] Although the repeated method of the switching drum according to the invention, together with a suitable determination of a central position of the switching drum, does not allow for an exact position determination, it does allow for a reliable approximate central position to be taken which is sufficiently close to the actual center of the switching drum or the switching sleeve and can therefore be reliably used as a starting point for further gear changes.

[0017] The procedure for calibrating the shift drum position can be carried out particularly in a claw gearbox without mechanical synchro components.

[0018] 2024P00095 WO 02.10.2025 BZ Further developments of the invention are specified in the dependent claims, the description and the accompanying drawings.

[0019] Preferably, after the first downward angle d1 has been traversed in the first step, when the switching drum is blocked, the current position of the switching drum is set as the zero position. After the first upward angle u1 has been traversed in the second step, when the switching drum is blocked, the first intermediate position ml is set as half of the first upward angle ul.

[0020] Thus, to determine a first approximate middle position ml: ml = ul / 2, where the position of the blockage after the first step, i.e., after the procedure along dl, is used as the zero position.

[0021] Preferably, the continuation criterion is fulfilled if the first upward angle u 1 is not equal to the distance e between the two end stops 2 and is not equal to the distance t between the two tip-to-tip positions 4. If the first upward angle ul is equal to the distance e between the two end stops 2 or equal to the distance t between the two tip-to-tip positions 4, a clear situation exists and the switching drum and switching sleeve are preferably not moved again.

[0022] Preferably, after the second upward angle u2 has been traversed in the fourth step, when the switching drum is blocked, the second middle position m2 is set as half the sum of the second downward angle d2 plus

[0023] 2024P00095 WO 02.10.2025 BZ second high angle u2, preferably minus a correction factor k, added to the zero position.

[0024] The second middle position m2 is thus calculated as: m2 = (d2+u2) / 2 + k, where the correction factor k is preferably calculated as: k = b / 2 + s, but where k is preferably only applied or calculated as greater than zero if: d2 >= b and u2 >= d.

[0025] The correction factor k is therefore not equal to zero if the second downward angle d2 is greater than or equal to the distance b between the first end stop and its tip-to-tip position, and if the second upward angle u2 is greater than or equal to the distance d between the first end stop and the other tip-to-tip position 4, i.e., the tip-to-tip position of the second end stop.

[0026] If the correction factor k is not equal to zero, then it is equal to half the distance b between the first end stop and its tip-to-tip position, preferably with a safety factor s added.

[0027] The safety factor s may preferably be between 1 degree and b / 2, particularly preferably between 2 degrees and b / 2 or b / 4, in particular s may be between about 2 and 6 degrees.

[0028] 2024P00095 WO 02.10.2025 BZ The geometry of the claw drive can be symmetrical, such that the distance b between the first end stop and its tip-to-tip position is equal to the distance d between the second end stop and its tip-to-tip position.

[0029] A motor vehicle according to the invention preferably comprises an internal combustion engine and / or an electric machine as a drive motor, a dog clutch for selectively transmitting the drive force of the internal combustion engine and / or the electric machine to at least one driven wheel of the motor vehicle, wherein the internal combustion engine and / or the electric machine are rigidly coupled to a shaft, i.e., without an intermediate clutch, wherein the dog clutch comprises a first loose gear of a first gear stage and a second loose gear of a second gear stage, which are axially fixed and rotatably mounted on the shaft, wherein a shift sleeve is arranged axially displaceably on the shaft between the first loose gear and the second loose gear in order to selectively connect either the first loose gear or the second loose gear to the shaft in a rotationally fixed manner by means of an engagement of the dogs in recesses associated with the dogs.wherein the shift sleeve is axially displaced depending on a rotation angle of a shift drum, wherein the claw drive includes an electric motor, wherein the shift drum is rotatable by means of the electric motor and thus the shift sleeve is axially movable on the shaft, wherein a tip-to-tip position of the shift sleeve, in which the claws rest against the first or second loose gear without entering the associated recesses, thus blocking further rotation of the shift drum, can occur during axial movement of the shift sleeve, wherein the motor vehicle has a control unit which is configured to perform a method for calibrating the shift drum as described above.

[0030] 2024P00095 WO 02.10.2025 BZ Short description of the drawing

[0031] The invention is described below by way of example with reference to the drawing.

[0032] Fig. is a schematic representation of switching drum positions of a switching drum for a method according to the invention.

[0033] Detailed description of the invention

[0034] The figure shows a switching drum of a dog clutch of a motor vehicle, in the form of a guide groove 1 of the switching drum, together with certain positions of the switching drum or guide groove 1 during the rotation of the switching drum.

[0035] As can be seen in the figure, tip-to-tip situations 4, in which blockages occur due to tooth-to-tooth engagement of the positive-locking elements of the dog clutch, are clearly distinguishable from the end stops 2, 3. In the illustrated embodiment, the first end stop 2 is located at the end of the shift drum where the first gear 5 is engaged (direction of rotation "down"). The second end stop 3 is located at the opposite end of the shift drum where the second gear 6 is engaged (direction of rotation "up"). A distinction between the tip-to-tip blockage positions 4 and the blockage positions at the end stops 2, 3 is not initially possible; however, by a method according to the invention, the shift drum can be reliably moved at least approximately to a central position 7 of the shift drum in which neither of the two gears 5, 6 is engaged.

[0036] 2024P00095 WO 02.10.2025 BZ In the illustrated exemplary embodiment, the distance b between the first end stop 2 and its tip-to-tip position 4 is 27 degrees. The distance d between the first end stop 2 and the other tip-to-tip position 4, i.e., the tip-to-tip position 4 of the second end stop 3, is approximately 67 degrees. The distance e between the two end stops 2 and 3 is approximately 94 degrees. The distance t between the two tip-to-tip positions 4 is approximately 40 degrees.

[0037] To calibrate a shift drum of a claw drive, especially in a learning process and preferably with loose gears that do not rotate against the shift sleeve, so that a tip-to-tip position is not resolved, a first downward angle dl is covered, in a first step the shift drum is rotated in the direction of the first end stop 2 until the shift drum is blocked, and the current position of the shift drum is set as the zero position.

[0038] Then, in a second step, the switching drum is rotated, covering a first vertical angle ul, in the direction of the second end stop 3 of the switching drum opposite the first end stop 2, until the switching drum is blocked.

[0039] The switching drum is then rotated to a first intermediate position ml, which depends on the first vertical angle u1. The first intermediate position ml is determined as half of the first vertical angle u1.

[0040] Then, if a continuation criterion is met, namely if the first vertical angle u 1 is not equal to the distance e between the two end stops 2 and is not equal to the distance t between the two tip-to-tip positions 4, in a third step the switching drum,

[0041] 2024P00095 WO 02.10.2025 BZ, after covering a second downward angle d2, is rotated again towards the first end stop 2 of the switching drum until the switching drum is blocked. Then, in a fourth step, the switching drum is rotated, after covering a second upward angle u2, towards the second end stop 3 of the switching drum until the switching drum is blocked.

[0042] The switching drum is then rotated to a second intermediate position m2, which depends on the second downward angle d2 and the second upward angle u2. The second intermediate position m2 is calculated as half the sum of the second downward angle d2 plus the second upward angle u2, preferably minus a correction factor k. The calculated value is again measured from the previously determined zero position.

[0043] The correction factor k is non-zero if the second downward angle d2 is greater than or equal to the distance b between the first end stop 2 and its tip-to-tip position 4, and if the second upward angle u2 is greater than or equal to the distance d between the first end stop 2 and the other tip-to-tip position 4.

[0044] The correction factor k, if it is not equal to zero, can be calculated as half the distance b between the first end stop 2 and its tip-to-tip position 4, preferably plus a safety factor s, for example plus about 3 degrees.

[0045] 2024P00095 WO 02.10.2025 BZ Reference List

[0046] 1 Guide groove of a switching drum

[0047] 2 first end stop

[0048] 3 second end stop

[0049] 4 Tip-to-Tip Position

[0050] 5 first gear

[0051] 6 second gear

[0052] 7 Center position b Distance between the first end stop and its tip-to-tip position d Distance between the first end stop and the other tip-to-tip position, i.e., the tip-to-tip position of the second end stop e Distance between the two end stops t Distance between the two tip-to-tip positions dl First downward angle d2 Second downward angle ml First center position m2 Second center position u1 First upward angle u2 Second upward angle k Correction factor s Safety factor

[0053] 2024P00095 WO 02.10.2025 BZ

Claims

Patent claims 1. A method for calibrating a shift drum in a dog clutch transmission of a motor vehicle, wherein the dog clutch transmission comprises a first loose gear of a first gear stage (5) and a second loose gear of a second gear stage (6), which are axially fixed and rotatably mounted on a shaft, wherein a shift sleeve is arranged axially displaceably on the shaft between the first loose gear and the second loose gear in order to selectively connect either the first loose gear or the second loose gear to the shaft in a rotationally fixed manner by means of an engagement of the claws in recesses associated with the claws, wherein the shift sleeve is axially displaced depending on a rotation angle of a shift drum, wherein the dog clutch transmission comprises an electric motor, wherein the shift drum is rotatable by means of the electric motor and thus the shift sleeve is axially movable on the shaft, wherein a tip-to-tip position (4) of the shift sleeve, in which the claws bear against the first or second loose gear without entering the associated recesses,so that further rotation of the switching drum is blocked, which can occur during the axial operation of the switching sleeve, characterized in that, for calibrating the switching drum, the switching drum is rotated by means of the electric motor in a first step towards a first end stop (2) of the switching drum, while covering a first downward angle (dl), until the switching drum is blocked, wherein in a second step the switching drum is rotated in the direction of a second end stop (3) of the switching drum opposite the first end stop (2), while covering a first upward angle (ul), until the switching drum is blocked, wherein da-, 2024P00095 WO 02.10.2025 BZ after the switching drum is rotated into a first intermediate position (ml) dependent on the first up-angle (ul), wherein, at least if a continuation criterion is present, in a third step the switching drum is rotated, overcoming a second down-angle (d2), in the direction of the first end stop (2) of the switching drum until the switching drum is blocked, wherein in a fourth step the switching drum is rotated, overcoming a second up-angle (u2), in the direction of the second end stop (3) of the switching drum until the switching drum is blocked, wherein the switching drum is then rotated into a second intermediate position (m2) dependent on the second down-angle (d2) and the second up-angle (u2).

2. Method according to claim 1, characterized in that after the first downward angle (dl) has been traversed in the first step, when the switching drum is blocked, the current position of the switching drum is set as the zero position, wherein after the first upward angle (ul) has been traversed in the second step, when the switching drum is blocked, the first intermediate position (ml) is set as half of the first upward angle (ul).

3. Method according to at least one of the preceding claims, characterized in that the continuation criterion is satisfied if the first vertical angle (ul) is not equal to the distance (e) between the two end stops (2) and is not equal to the distance (t) between the two tip-to-tip positions (4).

4. Method according to at least one of the preceding claims, 2024P00095 WO 02.10.2025 BZ 14 characterized in that, after the second up-angle (u2) has been traversed in the fourth step, when the switching drum is blocked, the second middle position (m2) is set as half the sum of the second down-angle (d2) plus the second up-angle (u2), preferably minus a correction factor (k), added to the zero position.

5. Method according to at least one of the preceding claims, characterized in that the correction factor (k) is non-zero if the second downward angle (d2) is greater than or equal to the distance (b) between the first end stop (2) and its tip-to-tip position (4) and if the second upward angle (u2) is greater than or equal to the distance (d) between the first end stop (2) and the other tip-to-tip position (4).

6. Method according to at least one of the preceding claims, characterized in that the correction factor (k), if it is not equal to zero, is equal to half the distance (b) between the first end stop (2) and its tip-to-tip position (4), preferably plus a safety factor (s).

7. Method according to at least one of the preceding claims, characterized in that the geometry of the claw drive is symmetrical, such that the distance (b) between the first end stop (2) and its tip-to-tip position (4) is equal to the distance (d) between the second end stop (2) and its tip-to-tip position (4). 2024P00095 WO 02.10.2025 BZ 15 8. Motor vehicle comprising an internal combustion engine and / or an electric machine as a drive motor, a dog clutch for selectively transmitting the drive force of the internal combustion engine and / or the electric machine to at least one driven wheel of the motor vehicle, wherein the internal combustion engine and / or the electric machine are rigidly coupled to a shaft without an intermediate clutch, wherein the dog clutch comprises a first loose gear of a first gear stage (5) and a second loose gear of a second gear stage (6), which are axially fixed and rotatably mounted on the shaft, wherein a shift sleeve is arranged axially displaceable on the shaft between the first loose gear and the second loose gear in order to selectively connect either the first loose gear or the second loose gear to the shaft in a rotationally fixed manner by means of an engagement of claws in recesses associated with the claws, wherein the shift sleeve is axially displaced depending on an angle of rotation of a shift drum.wherein the claw drive comprises an electric motor, wherein the shift drum is rotatable by means of the electric motor and thus the shift sleeve is axially movable on the shaft, wherein a tip-to-tip position (4) of the shift sleeve, in which the claws rest against the first or second loose gear without entering the associated recesses, so that further rotation of the shift drum is blocked, can occur during axial movement of the shift sleeve, wherein the motor vehicle has a control unit which is configured to carry out a method for calibrating the shift drum according to at least one of the preceding claims. 2024P00095 WO 02.10.2025 BZ

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