Detection of a switching drum position

Abstract

A method for detecting a shift drum position 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 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, to detect the position of the switching drum, the switching drum is rotated by means of the electric motor towards a first end stop (2) of the switching drum until the switching drum is blocked, wherein the current (I) required for the operation of the electric motor is monitored, wherein a “tip-to-tip” position (4) of the switching sleeve, in which the claws are in contact with the first or second loose gear without entering the associated recesses, thus blocking further rotation of the switching drum, is distinguished from a position of the switching drum at the first end stop (2), in which the first or second loose gear is non-rotatably connected to the shaft and blocks the switching drum, by detecting a different current (I) to be applied, so that, depending on the current to be applied, the position is determined as either the tip-to-tip position (4) or as the first end stop (2).

Description

Field of invention

[0001] The present invention relates to a method for detecting a shift drum position in a dog clutch transmission of a motor vehicle and a method for calibrating a shift drum. State of the art

[0002] 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 of the shift drum beyond the desired angular range.

[0003] The position of the shift unit, in particular the current rotation angle of the shift drum, must be known in order to engage gears. For this purpose, the transmission is calibrated once during production. 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 position of the shift drum is re-calibrated. For this, 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.

[0004] 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. Summary of the invention

[0005] It is an object of the invention to provide a method for detecting a shift drum position in a dog clutch transmission of a motor vehicle, which enables safe and reliable detection of the position. A further object is to provide a safe and reliable method for calibrating such a shift drum.

[0006] The problem is solved by a method for detecting a shift drum position in a dog clutch transmission of a motor vehicle, wherein the dog clutch transmission 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 a shaft, wherein a shift sleeve is 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 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, preferably by means of a shift fork, 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 for the detection of the shift drum position, preferably in a learning mode,The switching drum is rotated by means of the electric motor towards a first end stop of the switching drum until the switching drum is blocked, whereby the current required for the operation of the electric motor is monitored, whereby a "tip-to-tip" position of the switching sleeve, in which the claws rest against the first or second loose gear without entering the associated recesses, thus blocking further rotation of the switching drum, is distinguished from a position of the switching drum at the first end stop, in which the first or second loose gear is rotationally fixed to the shaft and the switching drum is blocked at the end stop, by detecting a different current to be applied, so that depending on the current to be applied the position as the tip-to-tip position or as the first end stop.

[0007] According to the invention, current monitoring is used to detect the current switching drum position in order to be able to distinguish between the possible blockage positions.

[0008] Four potential blockage points are expected: the respective end stops at the bottom and top, as well as the respective tip-to-tip blockage positions. According to the invention, a blockage at the end stop can be distinguished from a tip-to-tip position in order to correctly determine the position of the shift drum. Determining the blockage situation is particularly necessary in symmetrical transmission designs. However, the invention is also applicable to asymmetrical systems to simplify and / or more reliably determine the position.

[0009] By examining the current profile, preferably the increase in current at the beginning of the blockage, a tip-to-tip situation can be distinguished from a "normal" end stop.

[0010] The method for detecting the shift drum position can be carried out, in particular in a claw gearbox without mechanical synchro components, by means of current monitoring.

[0011] This method also enables the shift drum to be moved to a neutral position, even if a tip-to-tip situation in a dog clutch cannot or should not be resolved by rotating the gears relative to each other. For example, such a method can also be performed when the vehicle and / or the drive shaft of the dog clutch are stationary.

[0012] The method can also be used in a 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 the shaft of the dog clutch, i.e. without an intermediate clutch.

[0013] Further developments of the invention are specified in the dependent claims, the description and the accompanying drawings.

[0014] Preferably, the position of the switching drum is determined as a tip-to-tip position or as a first end stop depending on the time course and / or the slope and / or the maximum of the required current. In particular, the time course and the slope of the required current from the beginning of a blockage situation, and preferably until complete blockage and thus a maximum of the required current, are monitored and evaluated.

[0015] Preferably, to detect the position of the switching drum, the switching drum is rotated by means of the electric motor, after rotation to the first end stop, in the direction of the second end stop of the switching drum, which is opposite the first end stop, whereby the current required for the operation of the electric motor is monitored, and the position of the switching drum is determined as either the tip-to-tip position or the second end stop, depending on the required current. In addition to determining the respective blocking position at the first end of the switching drum, namely at the first end stop or its tip-to-tip position, the position at the second end of the switching drum, which is opposite the first end, can also be determined to increase the reliability of the position determination, namely as the position at the second end stop or its tip-to-tip position.For example, based on knowledge of the two blockage positions, a middle position between the two previously determined positions can be determined, depending on the known geometric relationships of the switching drum and the claws, and optionally also approached by the switching drum.

[0016] An inventive method for calibrating a shift drum comprises the steps of determining the shift drum position according to a method as previously described, wherein, depending on the determined position of the shift drum at the tip-to-tip position or at the first end stop, taking into account the geometry of the claw drive, in particular the known distance between the tip-to-tip position and the first end stop as well as the known distance between the two end stops, the shift drum is moved to a central position between the two end stops.

[0017] Preferably, a method for calibrating a shift drum comprises determining the shift drum position in the direction of the first end stop and additionally determining it in the direction of the second end stop. Depending on the determined positions of the shift drum in the first direction – at the tip-to-tip position or at the first end stop – and in the second direction – at the tip-to-tip position or at the second end stop – and taking into account the geometry of the claw drive, in particular the known distance between the tip-to-tip positions and the respective end stops, the shift drum is moved to a central position between the two end stops. Brief description of the drawings

[0018] The invention is described below by way of example with reference to the drawings. Fig. Figure 1 is a schematic representation of switching drum positions of a switching drum for a method according to the invention. Fig. Figure 2 is a schematic representation of a current flow for controlling a switching drum at a tip-to-tip position (left) and at an end-stop position (right). Detailed description of the invention

[0019] In Fig. Figure 1 is a switching drum, in the form of a guide groove 1 of the switching drum, together with certain positions of the switching drum or guide groove during the rotation of the switching drum.

[0020] As in Fig. As can be seen in Figure 1, tip-to-tip situations 4, where 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 and 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 reliable distinction between the tip-to-tip blockage positions 4 and the blockage positions at the end stops 2 and 3 is necessary to determine the position of the shift drum and, if necessary, to be able to approach the center position 7 of the shift drum, in which neither gear 5 nor 6 is engaged.

[0021] In the Fig. Figure 2 on the left shows the current increase, specifically the slope of the current I, in a tip-to-tip situation. The figure on the right shows... Fig. Figure 2 shows the current profile at an end stop (2, 3). The blockage occurs at a different point in the mechanism, resulting in different stiffnesses. The end stop is associated with a significantly higher gradient and a higher final value of the required current I. Reference symbol list 1 Guide groove of a switching drum 2 first end stop 3 second end stop 4 Tip-to-Tip Position 5 first gear 6 second gear 7 Middle position I current t time

Claims

[1] Method for detecting a shift drum position 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 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, characterized by, that to detect the position of the switching drum, the switching drum is rotated by means of the electric motor towards a first end stop (2) of the switching drum until the switching drum is blocked, whereby the current (I) required for the operation of the electric motor is monitored, wherein a “tip-to-tip” position (4) of the switching sleeve, in which the claws are in contact with the first or second loose gear without entering the associated recesses, so that further rotation of the switching drum is blocked, is distinguished from a position of the switching drum at the first end stop (2), in which the first or second loose gear is non-rotatably connected to the shaft and blocks the switching drum, by detecting a different current (I) to be applied, so that depending on the current to be applied the position is determined as tip-to-tip position (4) or as first end stop (2). [2] Method according to claim 1, characterized by, that depending on the time course and / or the slope and / or the maximum of the required current (I) the position of the switching drum is determined as tip-to-tip position (4) or as first end stop (2). [3] Method according to at least one of the preceding claims, characterized by , that to detect the switching drum position, the switching drum is rotated by means of the electric motor, after rotation to the first end stop (2), in the direction of the second end stop (3) of the switching drum opposite the first end stop (2), whereby the current (I) required for the operation of the electric motor is monitored, wherein, depending on the required current (I), the position of the switching drum is determined as tip-to-tip position (4) or as second end stop (3). [4] Method for calibrating a switching drum, wherein the switching drum position is determined according to a method according to at least one of claims 1 to 2, characterized by, that depending on the determined position of the shift drum at the tip-to-tip position (4) or at the first end stop (2), taking into account the geometry of the claw drive, in particular the known distance between the tip-to-tip position (4) and the first end stop (2) as well as the known distance between the two end stops (2, 3), the shift drum is moved to a central position (7) between the two end stops (2, 3). [5] Method for calibrating a switching drum, wherein the switching drum position is determined according to a method according to at least one of claims 1 to 2, wherein the switching drum position is additionally determined in the direction to the second end stop (3) according to a method according to claim 3, characterized by, that depending on the determined positions of the shift drum at the tip-to-tip position (4) or at the first end stop (2) as well as at the tip-to-tip position (4) or the second end stop (3), taking into account the geometry of the claw drive, in particular the known distance between the tip-to-tip positions (4) and the end stops (2, 3), the shift drum is moved to a middle position (7) between the two end stops (2, 3).

Images