DE102023003074A1 - Method for operating an actuating device for actuating a shift element of a transmission for a drive train of a motor vehicle and actuating device - Google Patents

Abstract

The invention relates to a method for operating an actuating device (12) for actuating a shifting element of a transmission (10) for a drive train of a motor vehicle, in which the actuating device (12) has an actuating piston (18) which can be displaced relative to a housing (14) of the actuating device (12) in a first direction (22) and in a second direction (24) opposite to the first direction (22) in order to actuate the shifting element. A first pressure chamber (16) is provided into which an actuating fluid can be introduced, as a result of which the actuating piston (18) can be acted upon with the actuating fluid and can therefore be displaced in the first direction (22) from a first position (ST1) into a second position of the actuating piston (18) relative to the housing (18). A second pressure chamber (20) is provided which is opposite the first pressure chamber (16) along the first direction (22), into which the actuating fluid can be introduced, whereby the actuating piston (18) can be acted upon by the actuating fluid and can thereby be displaced in the second direction (24) from the second position into the first position (ST1) of the actuating piston (18) relative to the housing (14).

Description

The invention relates to a method for operating an actuating device for actuating a shifting element of a transmission for a drive train of a motor vehicle, in particular a motor vehicle. The invention also relates to such an actuating device.

Motor vehicles with drive trains are well known from the general state of the art and in particular from series vehicle construction, whereby the respective motor vehicle can be driven by means of the respective drive train. The respective drive train has, for example, a respective transmission which has at least one or more switching elements. The respective switching element is used, for example, to connect a transmission element of the transmission, which can basically be rotated about an axis of rotation relative to an element, to the element in a rotationally fixed manner. The element is, for example, a housing of the transmission or another transmission element. In order to optionally connect the transmission element to the element in a rotationally fixed manner by means of the switching element or to decouple it from the element so that the transmission element can be rotated relative to the element, an actuating device is usually used by means of which the switching element can be switched. The switching element can thus be switched, for example, between a coupling state in which the transmission element is connected to the element in a rotationally fixed manner by means of the switching element, and an uncoupling state in which the transmission element can be rotated relative to the element.

The object of the present invention is to provide a method for operating an actuating device for actuating a shifting element of a transmission for a drive train of a motor vehicle and such an actuating device so that the shifting element can be actuated particularly advantageously.

This object is achieved by a method having the features of patent claim 1 and by an actuating device having the features of patent claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

A first aspect of the invention relates to a method for operating an actuating device for actuating a shifting element of a transmission for a drive train of a motor vehicle, also referred to as a motor vehicle drive station. This means that the motor vehicle, also referred to simply as a vehicle and designed, for example, as a motor vehicle, in particular as a passenger car, in its fully manufactured state has the drive train and thus the transmission and the actuating device and the shifting element. In particular, the motor vehicle can be driven by means of the drive train. The drive train has, for example, at least or exactly one motor, by means of which the motor vehicle can be driven via the transmission. The motor can be an internal combustion engine or an electrical machine, thus an electric motor. For example, the shifting element is arranged in a transmission area of the transmission and thus of the drive train. For example, the transmission has a first transmission element and a second transmission element. For example, the first gear element can be optionally connected to the second gear element in a rotationally fixed manner or decoupled from the second gear element by means of the switching element, wherein when the first gear element is decoupled from the second gear element, the first gear element can be rotated relative to the second gear element. In particular, for example, the switching element can be switched between a coupled state and an uncoupled state. In the coupled state, for example, the first gear element is connected to the second gear element in a rotationally fixed manner by means of the switching element, whereby relative rotations between the gear elements about an axis of rotation are prevented. In the uncoupled state, the first gear element can be rotated about the axis of rotation relative to the second gear element. In other words, for example, in the uncoupled state the switching element releases the gear elements for relative rotation about the axis of rotation between the gear elements. For example, the first gear element is a gearwheel. For example, the second gear element is a gear housing of the transmission. For example, the first gear element is arranged in the gear housing. By operating the switching element, for example, the switching element can be switched between the coupling state and the decoupling state. Thus, for example, by means of the actuating device, the switching element can be switched either into the coupling state or into the decoupling state by operating the switching element.

In the method, the actuating device has an actuating piston which can be displaced relative to a housing of the actuating device in a first direction and in a second direction opposite to the first direction in order to actuate the switching element. For example, the housing is the aforementioned transmission housing. For example, the actuating piston is arranged in the housing. The piston is also simply referred to as a piston. The actuating piston referred to above can thus be moved optionally in the first direction or in the second direction relative to the housing, that is to say moved translationally. In particular, the switching element can be actuated by moving the actuating piston in the first direction, and for example the switching element can be actuated by moving the piston in the second direction. For example, the switching element can be engaged or closed, that is to say in particular it can be brought or transferred from the uncoupled state to the coupled state, by moving the actuating piston in the first direction. For example, the switching element can be disengaged or deactivated, that is to say in particular it can be brought or transferred or switched from the coupled state to the uncoupled state, by moving the piston in the second direction. The reverse is of course conceivable. It is conceivable that the second transmission element can be rotated about the axis of rotation relative to the transmission housing, so that in the coupled state the first transmission element and the second transmission element can be rotated together or simultaneously about the axis of rotation relative to the transmission housing. In the uncoupled state, for example, the first gear element and the second gear element are rotatable about the axis of rotation relative to one another and relative to the housing. It is also conceivable that the second gear element is the gear housing, so that, for example, in the coupled state, in particular by means of the switching element, the first gear element is fixed to the housing in a rotationally fixed manner. In the uncoupled state, the first gear element is rotatable about the axis of rotation relative to the housing.

The actuating device has a first pressure chamber, arranged in particular in the housing, into which an actuating fluid can be introduced, i.e. can be introduced. The actuating fluid is preferably part of the actuating device in the method. The actuating fluid is very preferably a liquid, thus a hydraulic fluid. For example, the actuating device has a first line element, also referred to as a first line, through which the actuating fluid can flow, wherein the actuating fluid flowing through the first line element can be introduced into the first pressure chamber via the first line element.

By introducing the actuating fluid into the first pressure chamber, the first actuating piston can be at least indirectly, in particular directly, supplied with the actuating fluid and can thus be displaced in the first direction and thus from a first position into a second position of the actuating piston relative to the housing. For example, by introducing the actuating fluid into the first pressure chamber, the actuating piston can be at least indirectly, in particular directly, supplied with the actuating fluid in that the first pressure chamber is partially and directly delimited by the actuating piston, so that the actuating fluid received in the first pressure chamber can directly touch the actuating piston.

In the method, the actuating device also has a second pressure chamber, which is arranged in particular in the housing and is opposite the first pressure chamber along the first direction. The actuating fluid can be introduced into the second pressure chamber, i.e. can be introduced, whereby the actuating piston can be acted upon by the actuating fluid at least indirectly, in particular directly, and can thus be displaced in the second direction opposite to the first direction and thus from the second position to the first position of the actuating piston relative to the housing. For example, by moving the actuating piston from the first position to the second position, the switching element can be engaged, i.e. in particular transferred, brought or switched from the uncoupled position to the coupled position, and/or for example, by moving the actuating piston from the second position to the first position, the switching element can be disengaged or deactivated, i.e. in particular transferred, brought or switched from the coupled state to the uncoupled state. The reverse is of course easily possible. For example, the actuating piston can be at least indirectly, in particular directly, supplied with the actuating fluid by introducing the actuating fluid into the second pressure chamber in that the second pressure chamber is partially and directly delimited by the actuating piston. As a result, the actuating fluid introduced into the second pressure chamber and thus received in the second chamber can directly touch the actuating piston. In particular, it is conceivable that the first direction and the second direction coincide with a common straight line, which runs, for example, parallel to the aforementioned axis of rotation or coincides with the axis of rotation. Thus, for example, the piston can be displaced in the axial direction of the switching element and the actuating device relative to the housing. For example, the respective pressure chamber is delimited, in particular directly, by the piston in a delimiting direction that runs perpendicular to the respective direction and thus, for example, perpendicular to the axis of rotation. The delimiting direction runs, for example, in the radial direction of the actuating device, the radial direction of which runs perpendicular to the axial direction of the actuating device and thus perpendicular to the axis of rotation and in particular perpendicular to the respective direction. runs. In particular, it is conceivable that the actuating piston has a jacket surface on the outer circumference, by which the respective pressure chamber is delimited in the delimiting direction, in particular directly. It is conceivable that the outer circumference jacket surface of the piston is cylindrical at least in its length region running along the respective direction, thus having the shape of a right circular cylinder, wherein it is preferably provided that the outer circumference jacket surface is completely cylindrical at least in the length region in the circumferential direction of the piston running around the respective direction.

In order to be able to move the piston particularly advantageously and thereby actuate and thus switch the switching element particularly advantageously and in particular quickly, the method according to the invention provides that after a first displacement of the actuating piston in the second direction and thereby into the first position and before a second displacement of the actuating piston in the first direction and thus into the second position immediately following the first displacement and while the actuating piston is in the first position as a result of the first displacement, a first pressure increase is brought about in the second pressure chamber by means of the actuating fluid, during which or through which the actuating piston is at least indirectly, in particular directly, actuated with the actuating fluid, whereupon the second displacement, which immediately follows the first displacement, is brought about by a second pressure increase being brought about in the first pressure chamber by means of the actuating fluid, during which or through which the actuating piston is at least indirectly, in particular directly, actuated with the actuating fluid. The feature that the second displacement immediately follows the first displacement is to be understood as meaning that no other displacement of the piston in the first direction occurs between the first displacement and the second displacement. It should be explicitly noted at this point that the ordinals, also known as ordinal numbers, which refer to the displacement of the actuating piston, such as "first" and "second", are not to be understood in such a way that the wording "first displacement" means that the first displacement is the very first displacement of the piston that occurs after the actuating device has been manufactured, and that the wording "second displacement" is not to be understood in such a way that the second displacement is the second displacement that occurs after the actuating device has been manufactured and follows the first displacement. Rather, with regard to the displacements, the ordinal numbers are used in order to conceptually distinguish the displacements and thus to be able to clearly refer to the displacements of the actuating piston. In particular, with regard to the displacements of the actuating piston, the ordinal number words are used in order to be able to clearly describe a temporal sequence of the displacements, in this case in particular such that the second displacement immediately follows the first displacement, thus the first displacement immediately precedes the second displacement in time. The same applies to the pressure increases.

The first pressure increase is to be understood in particular as meaning that after the first displacement and before the first pressure increase, a pressure prevailing in the second pressure chamber has a first value, wherein during or as a result of the first pressure increase, the pressure prevailing in the second pressure chamber is increased from the first value to a second value that is higher than the first value. It is conceivable that after the first displacement and before the first pressure increase, the actuating fluid is taken up into the second pressure chamber, or the second pressure chamber is at least partially or completely filled with the actuating fluid, or the second pressure chamber no longer contains any actuating fluid. Accordingly, the second pressure increase is to be understood as meaning that due to or during the second pressure increase, a pressure prevailing in the first pressure chamber is increased from a third value to a fourth value that is greater than the third value, in order to thereby move the actuating piston in the first direction and thus from the first position to the second position. Before the second pressure increase, the first pressure chamber can be at least partially or completely filled with the actuating fluid, or before the second pressure increase, no actuating fluid is taken up into the first pressure chamber.

• Während eines Betriebs des Kraftfahrzeugs soll der auch als Hydraulikkolben bezeichnete oder als Hydraulikkolben ausgebildete Kolben das Schaltelement hochdynamisch betätigen. Somit ist es wünschenswert, den Kolben schnell und reproduzierbar relativ zu dem Gehäuse verschieben zu können, um das Schaltelement schnell und vor allem reproduzierbar betätigen zu können. Die jeweilige, eine jeweilige Betätigung des Schaltelements bewirkende Verschiebung des Betätigungskolbens wird auch als Schaltvorgang des Betätigungskolbens bezeichnet. Somit sind die erste Verschiebung und die zweite Verschiebung Schaltvorgänge des Kolbens. Wenn im Folgenden die Rede von einem Schaltvorgang ist, so ist darunter ein Schaltvorgang des Betätigungskolbens zu verstehen, falls nichts anderes angegeben ist. Da die zweite Druckerhöhung die zweite Verschiebung bewirkt, bewirkt die zweite Druckerhöhung einen Schaltvorgang des Betätigungskolbens. Die erste Druckerhöhung bewirkt keinen Schaltvorgang des Betätigungskolbens, kann jedoch für eine solche insbesondere relativ zu dem Gehäuse erfolgende Bewegung, insbesondere Verschwenkung, des Kolbens sorgen, dass der Kolben nach der ersten Verschiebung und vor der zweiten Verschiebung vorteilhaft relativ zu dem Gehäuse ausgerichtet ist, um bei der oder durch die zweite Verschiebung des Betätigungskolbens den Betätigungskolben schnell, reibungsarm und ohne Verklemmung zu verschieben. Dies ist insbesondere dann vorteilhaft, wenn das Schaltelement als ein formschlüssiges Schaltelement, insbesondere als eine Klauenkupplung, ausgebildet ist.
• Durch das erfindungsgemäße Verfahren ist eine vorteilhafte Ausrichtung des Kolbens vor einem jeweiligen Schaltvorgang des Kolbens realisierbar, ohne eine bauraum- und
• kostenintensive Lagerung des Kolbens verwenden zu müssen. Es wurde gefunden, dass beispielsweise dann, wenn der Betätigungskolben vor einem Schaltvorgang des Betätigungskolbens nicht vorteilhaft insbesondere relativ zu dem Gehäuse ausgerichtet ist, so dass beispielsweise der Betätigungskolben vor einem Schaltvorgang des Betätigungskolbens eine Schiefstellung aufweist, es zu einem ungleichmäßigen Druckaufbau im jeweiligen Druckraum sowie gegebenenfalls zu einem Verkanten des Betätigungskolbens kommen kann. Dies kann zu einer übermäßig langen, für den jeweiligen Schaltvorgang des Betätigungskolbens und somit für das jeweilige Betätigen des Schaltelements erforderliche, auch als Schaltzeit oder Schaltdauer bezeichnete Zeitdauer führen, was zu Komforteinbußen führen kann. Die zuvor genannten Nachteile und Probleme können nun durch das erfindungsgemäße Verfahren vermieden werden.
• Die etwaige Schiefstellung des Betätigungskolbens vor der zweiten Verschiebung und
• nach der ersten Verschiebung kann beispielsweise durch Vibrationen bewirkt werden, die beispielsweise während der ersten Verschiebung und/oder nach der ersten Verschiebung und vor der zweiten Verschiebung auftreten. Ferner kann beispielsweise eine etwaige Schiefstellung des Betätigungskolbens nach der ersten Verschiebung und vor der zweiten Verschiebung durch die erste Verschiebung selbst, mithin durch vorangegangene, das heißt der zweiten Verschiebung vorhergehende Schaltvorgänge des Betätigungskolbens bewirkt werden. Derartige Schiefstellungen sowie anderweitige, ungünstige Lagen des sich in der ersten Stellung befindenden Betätigungskolbens können durch die erste Druckerhöhung korrigiert, das heißt aufgehoben werden, so dass sich nach der ersten Druckerhöhung und vor der zweiten Druckerhöhung und somit insbesondere vor der zweiten Verschiebung der Kolben in der ersten Stellung und in einer vorteilhaften Lage oder Ausrichtung, insbesondere Soll-Lage und/oder Soll-Ausrichtung, befindet, so dass die zweite Verschiebung schnell durchgeführt werden kann. Zusammenfassend ausgedrückt wird der Betätigungskolben durch die erste Druckerhöhung unmittelbar vor der zweiten Verschiebung ausgerichtet, damit der Betätigungskolben schnell und reproduzierbar betätigt werden und somit die zweite Verschiebung ausführen kann. Die Ausrichtung des Betätigungskolbens erfolgt dabei durch oder über die erste Druckerhöhung in dem zweiten Druckraum, der dem ersten Druckraum gegenüberliegt, mittels welchem die eigentlich durchzuführende, zweite Verschiebung bewirkt wird, und zwar durch Durchführen der zweiten Druckerhöhung in dem ersten Druckraum. Die jeweilige Druckerhöhung in dem jeweiligen Druckraum wird auch als Bedruckung des jeweiligen Druckraums bezeichnet. Unter der Bedruckung des jeweiligen Druckraums ist zu verstehen, dass in dem jeweiligen Druckraum herrschender Druck erhöht wird, beispielsweise dadurch, dass eine zunächst außerhalb des jeweiligen Druckraums angeordnete Menge des Betätigungsfluids in den jeweiligen Druckraum eingebracht, das heißt eingeleitet, dabei insbesondere hineingefördert wird und/oder dadurch, dass ein Druck des bereits im jeweiligen Druckraum aufgenommenen Betätigungsfluids erhöht wird.

Since the actuating piston can be moved either in the first direction or in the second direction, the piston is a double-acting piston, which is also referred to as a double-acting hydraulic piston. The method enables an advantageous alignment of the actuating piston, in particular relative to the housing after the first displacement and before the second displacement, which is or causes an actuation of the switching element, also referred to as a switching process. The switching element is actuated by both the first displacement and the second displacement, for example in such a way that the switching element is disengaged by the first displacement and engaged by the second displacement, or vice versa. The switching element is thus actuated by the second pressure increase, in particular in particular in such a way that the switching element is inserted or disengaged. However, during the first pressure increase which takes place before the second pressure increase, the switching element is not actuated because the first pressure increase takes place, and is therefore carried out, while the actuating piston is already in the first position. The first pressure increase can, however, cause a movement and thus an alignment of the actuating piston, in particular relative to the housing, as a result of which an unfavorable alignment or position of the piston, for example a skewed position of the actuating piston, relative to the housing is corrected or canceled before the second displacement and after the first displacement, so that the actuating piston is in the first position after the first pressure increase and before the second pressure increase and in an advantageous position, in particular relative to the housing. As a result, the second displacement can take place without any problems, without, for example, excessive friction or tilting of the piston. In particular, the method according to the invention enables an advantageous alignment of the piston after the first displacement and before the second displacement, without the need for a complex, costly and space-intensive mounting of the piston. For example, the first pressure increase that takes place after the first displacement and before the second displacement and before the second pressure increase can cause such a pivoting movement of the actuating piston relative to the housing that an unfavorable position of the actuating piston relative to the housing, such as a slanted position of the piston, is eliminated, so that the second displacement can be advantageously carried out. The invention is based in particular on the following findings and considerations:

• When the motor vehicle is in operation, the piston, also known as a hydraulic piston or designed as a hydraulic piston, is intended to actuate the switching element in a highly dynamic manner. It is therefore desirable to be able to move the piston quickly and reproducibly relative to the housing in order to be able to actuate the switching element quickly and, above all, reproducibly. The respective displacement of the actuating piston which causes a respective actuation of the switching element is also referred to as the switching process of the actuating piston. The first displacement and the second displacement are therefore switching processes of the piston. When a switching process is mentioned below, this is to be understood as a switching process of the actuating piston, unless otherwise stated. Since the second increase in pressure causes the second displacement, the second increase in pressure causes a switching process of the actuating piston. The first pressure increase does not cause a switching operation of the actuating piston, but can ensure such a movement, in particular pivoting, of the piston, in particular relative to the housing, that the piston is advantageously aligned relative to the housing after the first displacement and before the second displacement in order to move the actuating piston quickly, with little friction and without jamming during or as a result of the second displacement of the actuating piston. This is particularly advantageous when the switching element is designed as a positive switching element, in particular as a claw clutch.
• The method according to the invention enables an advantageous alignment of the piston before each switching operation of the piston, without requiring a space-saving and
• cost-intensive bearing of the piston. It has been found that, for example, if the actuating piston is not advantageously aligned, particularly relative to the housing, before a switching operation of the actuating piston, so that, for example, the actuating piston is at an angle before a switching operation of the actuating piston, this can lead to an uneven pressure build-up in the respective pressure chamber and possibly to a jamming of the actuating piston. This can lead to an excessively long time period required for the respective switching operation of the actuating piston and thus for the respective actuation of the switching element, also referred to as the switching time or switching duration, which can lead to a loss of comfort. The disadvantages and problems mentioned above can now be avoided by the method according to the invention.
• The possible misalignment of the actuating piston before the second displacement and
• after the first shift can be caused, for example, by vibrations that occur, for example, during the first shift and/or after the first shift and before the second shift. Furthermore, any misalignment of the actuating piston after the first shift and before the second shift can be caused, for example, by the first shift itself, and thus by previous switching operations of the actuating piston, i.e. prior to the second shift. Such misalignments and other unfavorable positions of the in the first position can be corrected, that is to say canceled, by the first pressure increase, so that after the first pressure increase and before the second pressure increase and thus in particular before the second displacement, the piston is in the first position and in an advantageous position or orientation, in particular the target position and/or target orientation, so that the second displacement can be carried out quickly. In summary, the actuating piston is aligned by the first pressure increase immediately before the second displacement so that the actuating piston can be actuated quickly and reproducibly and thus carry out the second displacement. The alignment of the actuating piston takes place by or via the first pressure increase in the second pressure chamber, which is opposite the first pressure chamber, by means of which the second displacement to be carried out is actually brought about, namely by carrying out the second pressure increase in the first pressure chamber. The respective pressure increase in the respective pressure chamber is also referred to as the pressure in the respective pressure chamber. Pressurization of the respective pressure chamber means that the pressure prevailing in the respective pressure chamber is increased, for example by introducing a quantity of the actuating fluid initially arranged outside the respective pressure chamber into the respective pressure chamber, i.e. by introducing it, in particular by conveying it in, and/or by increasing the pressure of the actuating fluid already contained in the respective pressure chamber.

• - reproduzierbare Schaltzeiten und Loslaufzeiten
• - Gefahr eines Verkantens des Kolbens wird vermieden
• - ein schiefes Loslaufen, das heißt Losbewegen des Kolbens wird vermieden.

If the actuating device is designed, for example, in such a way that the switching element can be engaged by moving the actuating piston in the first direction, i.e. can be transferred from the uncoupled state to the coupled state, and if the actuating device is designed or configured, for example, in such a way that the switching element can be disengaged by moving the actuating piston in the second direction, i.e. can be transferred from the coupled state to the uncoupled state, then the first pressure chamber is also referred to, for example, as the “pressure chamber engaged” and the second pressure chamber is also referred to as the “pressure chamber disengaged”. The respective pressure chamber is also referred to as the respective piston chamber. Thus, for example, the switching element is disengaged by the first displacement, and thus, for example, the switching element is engaged by the second displacement. Thus, for example, in the method according to the invention it is provided that after the switching element has been laid out by the first displacement and before the switching element has been inserted by the second displacement, the second pressure chamber actually designed for laying out is pressurized in order to advantageously align the actuating piston in the first position and then to move it in the first direction by pressing on the first pressure chamber, thus inserting the switching element. In other words, if the switching element is to be inserted by pressing on the first pressure chamber, the opposite “pressure chamber laid out” is printed before the switching element is inserted, i.e. before the “pressure chamber inserted” is printed, and only then is the “pressure chamber inserted” printed to effect the second displacement. The opposite can occur. If, for example, the actuating piston is initially in the second position and the switching element is to be disengaged, then before the “pressure chamber disengaged” is printed, the “pressure chamber engaged” is printed in order to advantageously align the actuating piston in the second position, whereupon the “pressure chamber disengaged” is printed and thus the actuating piston is moved from the second position to the first position and in the second direction and the switching element is disengaged. Since, for example, a respective switching process of the actuating piston and thus a respective actuation of the switching element is always triggered, in particular, by an electronic computing device also referred to as a control unit, the respective printing of the respective pressure chamber intended for aligning the actuating piston can take place without any problems before the respective switching process of the piston. The respective pressure chamber that is opposite the respective pressure chamber that is to be printed or is printed in order to cause a switching process of the actuating piston is also referred to as the counter chamber or opposite side, so that by printing on the respective opposite side the actuating piston is aligned before a switching process of the actuating piston is caused. The method according to the invention thus enables in particular the following advantages:

• - reproducible switching times and start times
• - The risk of jamming the piston is avoided
• - A crooked start, i.e. loose movement of the piston, is avoided.

Overall, it can be seen that the second pressure increase causes the second displacement of the actuating piston and thus the second actuating piston is displaced from the first position to the second position and thus in the first direction relative to the housing. The first pressure increase does not cause the actuating piston to switch, since the actuating piston is already in the first position during the first pressure increase. The first pressure increase therefore does not cause the switching element to be actuated. The first pressure increase therefore does not serve to actuate the switching element, but rather, as previously described, to align the actuating piston after the first displacement and before the second displacement, in particular relative to the housing, and thus to bring it into an advantageous position or alignment, while the actuating piston remains in the first position.

In order to be able to align and move the actuating piston particularly as required, so that the switching element can be actuated particularly advantageously, one embodiment of the invention provides that the actuating device has a first valve device that can be supplied with the actuating fluid and can be switched, in particular moved, between a first switching position and a second switching position. In the first switching position, the actuating fluid supplied to the first valve device is supplied to the first pressure chamber via the first valve device, thus introduced into the first pressure chamber and thus introduced into the first pressure chamber. In the second switching position, the actuating fluid supplied to the first valve device is supplied to the second pressure chamber via the first valve device, thus introduced into the second pressure chamber. A second valve device that can be supplied with the actuating fluid and can be switched, in particular moved, between a third switching position and a fourth switching position is also provided. In the third switching position, the actuating fluid supplied to the second valve device is supplied via the second valve device to the first valve device, which can thereby be supplied with the actuating fluid and can thus subsequently forward the actuating fluid supplied to the first valve device either into the first pressure chamber or into the second pressure chamber. In the fourth switching position, the first valve device is not supplied with the actuating fluid via the second valve device. For example, in the fourth switching position, the actuating fluid supplied to the second valve device is supplied via the second valve device to a cooling device of the motor vehicle. For example, at least a partial area of the engine can be cooled by means of the cooling device. For example, the partial area of the engine, also referred to as the drive motor, is or comprises a rotor and/or a stator of the drive motor, particularly when the drive motor is designed as the aforementioned electrical machine.

In order to be able to align and also move the actuating device in a particularly advantageous manner, it is provided in a further embodiment of the invention that, in order to effect the first pressure increase, the second valve device is in the third switching position and, in particular, at the same time, the first valve device is in the second switching position. In addition, it is provided that, in order to effect the second pressure increase, the second valve device is in the third switching position and, in particular, at the same time, the first valve device is in the first switching position.

A further embodiment of the invention is characterized in that, in order to effect the first pressure increase, the second valve device is switched from the fourth switching position to the third switching position at a first point in time, whereby, in order to effect the second pressure increase and while the second valve device remains in the third switching position, the first valve device is switched from the second switching position to the first switching position at a second point in time following the first point in time. As a result, the actuating piston can be initially aligned and then moved in a short time and thus particularly quickly.

In order to achieve a particularly advantageous actuation of the switching element, it has been shown to be particularly advantageous if a time period between the first point in time and the second point in time and thus, for example, the second point in time is dependent on a temperature and/or is set, i.e. varied, depending on the temperature. The actuating piston can thus be quickly aligned and in particular moved accordingly, so that the switching element can be actuated particularly advantageously.

In a further embodiment of the invention, it is provided that a second time period is determined which lies between the first time and a determination time following the first time, at which a movement of the switching element following the first time is determined. The determined second time period is compared as the actual time period with at least one reference time period which characterizes the second time period determined in at least one previous, past implementation of the method. The time period between the first time and the second time period, also referred to as the first time period, is increased if the comparison determines that the actual time period is longer than the reference time period. This allows the actuating piston to be aligned quickly, i.e. in a short time, and subsequently moved.

In a further, particularly advantageous embodiment of the invention, it is provided that a first time period is determined which lies between the first time and a determination time following the first time, at which a movement of the switching element following the first time is determined. The determined first time period is compared as the actual time period with at least one reference time which characterizes the first time period determined in at least one previous, past implementation of the method. In this case, a second time period between the first time and the second time is set depending on the comparison, in particular such that the second time period is increased if the comparison determines that the actual time period is longer than the reference time. As a result, the actuating piston can be advantageously aligned and, in particular, subsequently moved, so that the total time required for aligning the actuating piston and for a subsequent switching process of the actuating piston can advantageously be kept low.

In order to be able to move the actuating piston in both the first direction and the second direction in a highly dynamic and thus particularly fast manner, a further embodiment of the invention provides that after the second displacement of the actuating piston in the first direction and before a third displacement of the actuating piston in the second direction immediately following the second displacement, during which the actuating piston is in the second position as a result of the second displacement, a third pressure increase is brought about in the first pressure chamber, which is now the opposite side, by means of the actuating fluid, during which the actuating piston is actuated by the actuating piston and a switching process of the actuating piston, thus an actuation of the switching element, does not take place, whereupon the third displacement is brought about and thus the switching element is actuated by a fourth pressure increase being brought about in the second pressure chamber by means of the actuating fluid, during which the actuating piston is actuated by the actuating fluid.

Finally, it has proven to be particularly advantageous if the respective pressure increase is brought about by introducing, i.e. introducing, a quantity of the actuating fluid initially arranged outside the respective pressure chamber into the respective pressure chamber.

A second aspect of the invention relates to an actuating device for actuating a shifting element of a transmission for a drive train of a motor vehicle, wherein the actuating device is designed to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention and vice versa.

Further advantages, features and details of the invention emerge from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention.

• 1 ausschnittsweise eine schematische Längsschnittansicht eines Getriebes für ein Kraftfahrzeug, mit einer Betätigungsvorrichtung zum Betätigen eines Schaltelements des Getriebes;
• 2 ausschnittsweise eine weitere schematische Längsschnittansicht des Getriebes;
• 3 eine schematische Darstellung der Betätigungsvorrichtung;
• 4 ein Diagramm zum Veranschaulichen eines Verfahrens zum Betreiben der Betätigungsvorrichtung;
• 5 eine weitere schematische Darstellung der Betätigungsvorrichtung; und
• 6 eine weitere schematische Darstellung der Betätigungsvorrichtung.

The drawing shows in:

• 1 a detail of a schematic longitudinal sectional view of a transmission for a motor vehicle, with an actuating device for actuating a shift element of the transmission;
• 2 a further schematic longitudinal sectional view of the transmission;
• 3 a schematic representation of the actuating device;
• 4 a diagram illustrating a method of operating the actuator;
• 5 another schematic representation of the actuating device; and
• 6 another schematic representation of the actuating device.

In the figures, identical or functionally identical elements are provided with identical reference symbols.

1 and 2 each show a partial schematic longitudinal sectional view of a transmission 10 of a drive train for a motor vehicle. This means that the motor vehicle, also referred to simply as a vehicle and preferably designed as a motor vehicle, in particular as a passenger car, in its fully manufactured state has the drive train, also referred to as a motor vehicle drive train, and can be driven by means of the drive train. The drive train comprises the transmission 10, via which, for example, the motor vehicle can be driven in particular by a drive motor of the drive train. The transmission 10 has an actuating device 12, by means of which, as in the following explained in more detail below, a switching element of the transmission 10 can be actuated. The transmission 10 has, for example, a first transmission element (not visible in the figures), which can be or comprise a gearwheel, for example. The transmission 10 also has a second transmission element, wherein the transmission elements can be connected to one another in a rotationally fixed manner by means of the switching element mentioned. This is to be understood in particular that the switching element can be switched between a coupled state and an uncoupled state. In the coupled state, the transmission elements are connected to one another in a rotationally fixed manner, in particular by means of the switching element. In the uncoupled state, the transmission elements can be rotated relative to one another, in particular about an axis of rotation. The second transmission element is, for example, a transmission housing of the transmission 10, so that, for example, in the coupled state, the first transmission element is fixed to the transmission housing in a rotationally fixed manner, in particular by means of the switching element, as a result of which rotations of the first transmission element about the axis of rotation relative to the transmission housing are avoided. In the uncoupled state, the first transmission element is rotatable about the axis of rotation relative to the transmission housing. Thus, the switching element is, for example, a brake switching element, in particular a brake claw.

The actuating device 12 has a housing 14, which can be, for example, the transmission housing or a part of the transmission housing. The actuating device 12 also has a first pressure chamber 16, which is arranged in the housing 14. An actuating fluid, preferably in the form of a liquid, in particular oil, can be introduced into the first pressure chamber 16, in particular via a first line element of the actuating device 12. The actuating device 12 also has an actuating piston 18, which is also simply referred to as a piston. The actuating device 12 also has a second pressure chamber 20, into which the actuating fluid can be introduced and thus introduced, in particular via a second line element of the actuating device 12. The actuating piston 18 can be displaced, and thus moved in a translational manner, relative to the housing 14 in order to actuate the switching element, either in a first direction illustrated by an arrow 22 or in a second direction illustrated by an arrow 24 and opposite to the first direction. The piston (actuating piston 18) can thus be displaced in the first direction and in the second direction relative to the housing 14. By introducing the actuating fluid into the first pressure chamber 16, the actuating piston 18 can be directly actuated with the actuating fluid and can therefore be displaced in the first direction and from a first position ST1 to a second position of the actuating piston 18 relative to the housing 14. It can be seen that the pressure chambers 16 and 20 are opposite one another, in this case such that the second pressure chamber 20 is opposite the first pressure chamber 16 along the first direction. By introducing, i.e. introducing the actuating fluid into the second pressure chamber 20, the actuating piston 18 can be directly acted upon with the actuating fluid and can thus be displaced in the second direction and from the second position to the first position of the actuating piston 18 relative to the housing 14. The respective displacement of the actuating piston 18 from the first position ST1 to the second position and from the second position to the first position ST1, also referred to as displacement, is also referred to as a respective switching process of the actuating piston 18. The switching element can be actuated or actuated, i.e. switched, by a or the respective switching operation of the actuating piston 18, so that the respective switching operation of the actuating piston 18 is accompanied by a respective switching operation of the switching element, which is actuated during the respective switching operation of the switching element. The respective switching operation of the actuating piston 18 is thus to be understood as synonymous with the respective switching operation of the switching element and vice versa.

In the embodiment shown in the figures, the switching element is engaged, i.e. brought, transferred or switched from the uncoupled state to the coupled state, by moving the actuating piston 18 in the first direction from the first position ST1 to the second position. In addition, the switching element is disengaged, i.e. brought, transferred or switched from the coupled state to the uncoupled state, by moving the actuating piston 18 in the second direction from the second position to the first position ST1.

The directions illustrated by the arrows 22 and 24 coincide with a straight line that runs, for example, parallel to the axis of rotation or coincides with the axis of rotation. In particular, the axis of rotation runs in the axial direction of the switching element and/or the transmission 10 and/or the actuating device 12.

For example, the switching element can be moved relative to the housing 14 between two switching element positions. A first of the switching element positions is a coupling position, which causes the coupling state, and a second of the switching element positions is a decoupling position, which causes the decoupling state. In other words, if the switching element is in the coupling position, the switching element is in the Coupling state. If the switching element is in the uncoupling state, the switching element is in the uncoupling position. Thus, for example, the first position of the actuating piston 18 goes hand in hand with the uncoupling position, so that, for example, and in particular whenever the actuating piston 18 is in the first position ST1, the switching element is in the uncoupling position. Furthermore, for example, the second position of the actuating piston 18 goes hand in hand with the coupling position, so that, for example, and in particular whenever the actuating piston 18 is in the second position, the switching element is in the coupling position. Thus, for example, by moving the actuating piston 18 from the first position ST1 to the second position, the switching element can be moved from the uncoupling position to the coupling position. Furthermore, for example, by moving the actuating piston 18 from the second position to the first position ST1, the switching element can be moved from the coupling position to the uncoupling position. The respective pressure chamber 16, 20 is also referred to as piston chamber or actuation chamber.

Viewed along the respective direction, a respective seal 26, 28 is arranged on this side and the other side of the first pressure chamber 16, wherein the seal 26 is also referred to as the first seal and the seal 28 is also referred to as the second seal. It can be seen that the first seal 26 is arranged on a first side of the pressure chamber 16 and the second seal 28 is arranged on a second side of the pressure chamber 16, wherein the sides are also referred to as axial sides and lie opposite one another along the respective direction. The seals 26 and 28, which are also referred to as sealing elements, are spaced apart from one another when viewed along the respective direction, in particular such that the first pressure chamber 16 is arranged between the seals 26 and 28 along the respective direction. By means of the seals 26 and 28, the actuating piston 18 is sealed against the housing 14, in particular such that the seal 26 rests on the one hand, in particular directly, on the actuating piston 18, in particular on an outer peripheral surface 30 of the actuating piston 18, and on the other hand, in particular directly, on the housing 14, in particular in the radial direction of the actuating device 12, the radial direction of which runs perpendicular to the axial direction of the actuating device 12 and perpendicular to the axis of rotation and perpendicular to the respective direction. Accordingly, for example, the seal 28 rests on the one hand, in particular directly, on the actuating piston 18, in particular on the outer peripheral surface 30, and on the other hand, in particular directly, on the housing 14, in particular in the radial direction. Furthermore, 1 and 2 It can be seen that the outer peripheral surface 30 faces the pressure chamber 16 in the radial direction of the actuating device 12, in particular of the gear 10 as a whole, wherein the pressure chamber 16 is delimited in a delimiting direction illustrated by an arrow 32 and in particular in the radial direction of the actuating device 12 inwards directly by the outer peripheral surface 30 of the actuating piston, which is also simply referred to as the piston. This is to be understood in particular that the actuating fluid received in the first pressure chamber 16 directly touches the outer peripheral surface 30 or the actuating piston 18. The delimiting direction illustrated by the arrow 32 runs perpendicular to the respective direction and thus perpendicular to the axis of rotation and to the axial direction of the actuating device 12.

In the 1 and 2 In the embodiment shown, the actuating piston 18 is displaced in the first direction, illustrated by the arrow 22, relative to the housing 14 when the actuating fluid is introduced into the pressure chamber 16 and in particular when a pressure increase is thus caused in the pressure chamber 16 and the actuating piston 18 is initially in the first position ST1. The actuating piston 18 is displaced in the second direction, illustrated by the arrow 24, relative to the housing 14 when the actuating fluid is introduced into the second pressure chamber 20 and in particular when this causes a pressure increase in the pressure chamber 20 and the actuating piston 18 is initially in the second position.

The actuating piston 18 has a first actuating surface B1, which can be acted upon, in particular directly, by the actuating fluid introduced into the first pressure chamber 16. By acting on the first actuating surface B1, the actuating piston 18 can be moved in the first direction and thereby from the first position ST1 into the second position. The actuating surface B1 partially and directly delimits the first pressure chamber 16, at least in the first position ST1. The actuating piston 18 also has a second actuating surface B2, which in this case can be acted upon directly by the actuating fluid introduced into the second pressure chamber 20. By acting on the second actuating surface B2, the actuating piston 18 can be moved from the second position into the first position ST1 and thus in the second direction relative to the housing 14. The second pressure chamber 20 is partially and directly delimited by the second actuating surface B2.

In the embodiment shown in the figures, the actuating piston 18 has, in particular precisely, a step 34 arranged at least in the first position ST1 along the respective direction between the seals 26 and 28 with the, in particular precisely one, first actuating surface B1 arranged at least in the first position ST1 along the respective direction between the seals 26 and 28 and also referred to as the active surface, which extends obliquely or perpendicularly to the respective direction. The actuating surface B2 also extends obliquely or perpendicularly to the respective direction. If the actuating fluid is now introduced into the first pressure chamber 16, the actuating fluid can flow directly onto the first actuating surface B1 and thus act directly on the first actuating surface B1, which is thereby, in particular directly, acted upon by the actuating fluid introduced into the first pressure chamber 16, i.e. introduced, and can thus be acted upon. As a result, the actuating piston 18 can be moved along the first direction, i.e. in the first direction relative to the housing 14, in order to actuate the switching element. If the actuating fluid is introduced into the second pressure chamber 20, i.e. introduced, the actuating fluid can flow directly onto the second actuating surface B2 and thus act directly on the second actuating surface B2, which is thereby actuated, in particular directly, by the actuating fluid introduced into the second pressure chamber 20, i.e. introduced, and can thus be actuated. As a result, the actuating piston 18 can be moved in the second direction relative to the housing 14 in order to actuate the switching element. The first direction is referred to as the first sliding direction, the second direction is also referred to as the second sliding direction.

In order to be able to move the actuating piston 18 in a highly dynamic and thus particularly fast manner and subsequently switch, i.e. actuate, the switching element in a highly dynamic and thus particularly fast manner, the actuating device 12 is operated by means of a method which is carried out, for example, by means of an electronic control system and is explained below. In the method for operating the actuating device 12, after a first displacement of the actuating piston 18 in the second direction and thus into the first position and before a second displacement of the actuating piston 18 in the first direction and thus into the second position immediately following the first displacement and while the actuating piston is in the first position ST1 as a result of the first displacement, a first pressure increase is brought about in the second pressure chamber 20 by means of the actuating fluid, during which the actuating piston 18, in particular the actuating surface B2, is actuated with the actuating fluid and an actuation of the switching element, thus a switching process of the actuating piston 18 and a switching process of the actuating element, does not take place or do not take place, whereupon the second displacement is brought about by a second pressure increase being brought about in the first pressure chamber 6 by means of the actuating fluid, during which the actuating piston 18, in particular the first actuating surface B1, is actuated with the actuating fluid. Both the first displacement and the second displacement are thus switching operations of the actuating piston 18, so that the switching element is actuated during both the first displacement and the second displacement. The switching element is thus actuated by the second pressure increase, in this case in such a way that the switching element is engaged. However, the switching element is not actuated during the first pressure increase. This means that the first pressure increase prevents the switching element from switching from the coupled state to the uncoupled state and the switching element from the uncoupled state to the coupled state, i.e. does not occur. The first displacement is or was caused, for example, by a further pressure increase in the second pressure chamber 20, wherein the actuating piston 18 and in particular the second actuating surface B2 is or was actuated by the actuating fluid during the further pressure increase. Between the first displacement and the second displacement, the switching element is not actuated and thus the actuating piston 18 is not moved from the first position ST1 to the second position. The first pressure increase therefore does not serve to cause a switching operation of the actuating piston 18, i.e. the first pressure increase does not serve to actuate the switching element, but by means of the first pressure increase the actuating piston 18 located in the first position ST1 can be advantageously aligned relative to the housing 14 in order to then be moved quickly and with little friction from the first position ST1 to the second position and subsequently to be able to actuate the switching element.

2 shows the actuating piston 18 in the first position ST1, wherein the actuating piston 18 is in an unfavorable alignment or position, designed as a slant, relative to the housing 14. Thus, after the first displacement, before the second displacement, the second pressure chamber 20 is pressurized, for example by introducing a quantity of the actuating fluid initially arranged outside the pressure chamber 20 into the pressure chamber 20 and/or by increasing the pressure of the actuating fluid received in the pressure chamber 20. As a result, the actuating piston 18 can be moved from the position in 2 shown tilt into one in 1 shown advantageous alignment relative to the housing 14, while the actuating piston 18 remains in the first position ST1, thus a displacement of the actuating piston 18 from the first position ST1 to the second position does not occur. The second pressure increase is then brought about and, for example, a pressure reduction in the pressure chamber 20 is permitted, for example in such a way that a discharge of the actuating fluid from the pressure chamber 20 is permitted and/or in such a way that a pressure reduction of the actuating fluid received in the pressure chamber 20 is permitted.

3 shows the actuating device 12 in a schematic representation. A reservoir in which the actuating fluid can be received or is received is designated by 36. The actuating device 12 has a first valve device 38 and a second valve device 40. The first valve device 38 can be supplied with the actuating fluid and can be switched between a first switching position S1 and a second switching position S2. In the first switching position S1, the actuating fluid supplied to the first valve device 38 is introduced into the first pressure chamber 16 via the first valve device 38. In the second switching position of the first valve device 38, the actuating fluid supplied to the first valve device 38 is introduced into the second pressure chamber 20 via the first valve device 38, so that in 3 the valve device 38 is in the second switching position S2. The valve device 40 can be switched between a third switching position S3 and a fourth switching position S4. In the third switching position, the actuating fluid supplied to the second valve device 40 is supplied via the second valve device 40 to the first valve device 38, which can then optionally forward the actuating fluid supplied to the valve device 38 into the first pressure chamber 16 or into the second pressure chamber 20. In the fourth switching position S4, the first valve device 38 is not supplied with the actuating fluid via the second valve device 40. In the fourth switching position S4, the actuating fluid supplied to the valve device 40 is fed via the valve device 40 to a 3 The cooling device 42 is shown particularly schematically and can be used to cool the drive motor, which is designed as an electric motor, using the actuating fluid. 3 the valve device 40 is in the third switching position S3. A pump 44, preferably designed as an electric pump, is also provided, by means of which the actuating fluid can be conveyed from the reservoir 36 and conveyed to the valve device 40, whereby the valve device 40 can be supplied with the actuating fluid, and thus whereby the actuating fluid can be fed to the valve device 40. In the third switching position S3, the actuating fluid conveyed by means of the pump 44 and thereby supplied to the valve device 40 is fed to the valve device 38 via the valve device 40. In the fourth switching position S4, the actuating fluid conveyed by means of the pump 44 and thereby conveyed to the valve device 40 is guided by means of, i.e. via the valve device 40 to the cooling device 42, so that the valve device 38 is not supplied with the actuating fluid conveyed by means of the pump 44 via the valve device 40.

4 shows a diagram on whose abscissa 46 the time is plotted. On the ordinate 47 a pressure prevailing in the pressure chamber 20 is plotted, so that a curve 48 illustrates as a temporal curve the pressure prevailing over time in the second pressure chamber 20, for example caused by the actuating fluid. In 4 is a total time period designated by G, which is also referred to as the total time duration. The total time period G comprises, in this case precisely, two time periods Z1 and Z2 as partial time periods, whereby the time periods Z1 and Z2 are also referred to as time durations. The total time period G begins at a first time t1 and ends at a second time t2, which follows the time t1. The time period Z1 begins at the time t1 and ends at a third time t3, which follows the time t1 and is before the time t2 and thus lies between the times t1 and t2. The second time period Z2 begins at the time t3 and ends at the time t2.

The respective valve device 38, 40 can be supplied with electrical energy, i.e. with electrical current, and can thereby be switched from one of the respective switching positions to the other of the switching positions. Supplying the respective valve device 38, 40 with electrical energy, i.e. with electrical current, is also referred to as energizing the respective valve device 38, 40. If the respective valve device 38, 40 is not supplied with electrical current, the respective valve device 38, 40 is in a de-energized state, and thus the respective valve device 38, 40 is de-energized. In the present case, by energizing the valve device 38, the valve device 38 can be switched from the switching position S2 to the switching position S1, so that the valve device 38 assumes the second switching position S2 when the valve device 38 is de-energized. By energizing the valve device 40, the valve device 40 can be switched from the fourth switching position S4 to the third switching position S3, so that the valve device 40 assumes the fourth switching position S4 when the valve device 40 is not energized.

Thus, to effect the first pressure increase, the second valve device 40 is in the third switching position S3 and the first valve device 38 is in the second switching position S2. To effect the second pressure increase, the second valve device 40 is in the third switching position S3 and the first valve device 38 is in the first switching position S1.

As in 3 As can be seen and shown, for example, at time t1 the valve device 40 is energized and thereby switched to the third switching position S3, while the valve device 38 is and remains de-energized. For example, in the first switching position S1 the actuating fluid can flow from the valve device 38 into the first pressure chamber 16 via the first line element, for example in the second switching position S2 the actuating fluid can flow from the valve device 38 into the second pressure chamber 20 via the second line element.

As a result, for example, during the time period Z1, the second line element and, for example, also the second pressure chamber 20 are pre-filled with the actuating fluid. Thus, during the time period Z1, the valve device 40 is energized and the valve device 38 is de-energized. During the time period Z2, the valve device 40 is and remains energized and the valve device 38 remains de-energized, thereby causing the first pressure increase in the second pressure chamber 20. As a result, the actuating piston 18 is aligned relative to the housing 14, in particular as a result of a circumferential pressure and thus application of force, resulting from the first pressure increase. In this case, for example, the actuating piston 18 is positioned at an end stop of the housing 14. In order to effect the second pressure increase and thus the second displacement after the first pressure increase, the valve device 38 is energized, for example, at the second time t2 and is thereby switched from the second switching position S2 to the first switching position S1, while the valve device 40 remains energized. This is in 5 illustrated. The valve device 38 is thereby supplied with the actuating fluid via the valve device 40, and the actuating fluid is introduced into the first pressure chamber 16 by the valve device 38, thereby causing the second pressure increase in the first pressure chamber 16. This causes a switching operation of the actuating piston 18 and a switching operation of the switching element, which takes place, for example, during a second total time period G2, which begins at the time t2 and ends, for example, at a fourth time t4 following the time t2. The time t2 is therefore between the times t3 and t4. After the second displacement of the actuating piston 18, the energization of the valve device 40 is terminated, thus the valve device 40 is switched to its non-energized state, so that the valve device 40 is switched from the switching position S3 to the switching position S4, and for example the energization of the valve device 38 is also terminated, which is thus switched from the switching position S1 to the switching position S2. This is in 6 Then, the actuating fluid conveyed to the valve device 40 by means of the pump 44 is guided via the valve device 40 to the cooling device 42, whereby the valve device 38 is not supplied with the actuating fluid via the valve device 40.

The time t2 can, for example, be set, i.e. varied, in particular depending on a temperature, in particular of the actuating fluid, and/or the actuating device 12 and/or the drive motor. The time t2 can, for example, be determined by a reproducible pre-filling behavior and a pressure increase rate, in particular such that, for example, the time t2 is read out from a characteristic map depending on the pre-filling behavior and depending on the pressure increase rate. By means of regular switching, i.e. switching processes during operation, a pre-filling time and thus the pre-filling behavior can be continuously learned and remains precise over the service life despite any deviations. A residual pressure resulting in particular from the first pressure increase and, for example, still prevailing in the second pressure chamber 20 during the second pressure increase keeps the actuating piston 18 stable in its advantageous orientation, so that the second displacement can then be carried out quickly.

list of reference symbols

10

transmission

12

actuator

14

Housing

16

first printing room

18

actuating piston

20

second pressure chamber

22

Arrow

24

Arrow

26

seal

28

seal

30

outer peripheral surface

32

Arrow

34

Level

36

reservoir

38

first valve device

40

second valve device

42

cooling device

44

pump

46

abscissa

47

ordinate

48

Course

G

total time span

G2

total time span

B1

first actuation surface

B2

second actuation surface

S1

first switch position

S2

second switch position

S3

third switch position

S4

fourth switch position

ST1

first position

t1

point in time (small t in the text)

t2

time

t3

time

t4

time

Z1

time span

Z2

time span

Claims (10)

Method for operating an actuating device (12) for actuating a shifting element of a transmission (10) for a drive train of a motor vehicle, in which: - the actuating device (12) has: ◯ an actuating piston (18) which can be displaced relative to a housing (14) of the actuating device (12) in a first direction (22) and in a second direction (24) opposite to the first direction (22) for actuating the shifting element; ◯ a first pressure chamber (16) into which an actuating fluid can be introduced, whereby the actuating piston (18) can be actuated with the actuating fluid and can thereby be displaced in the first direction (22) from a first position (ST1) into a second position of the actuating piston (18) relative to the housing (18); and ◯ a second pressure chamber (20) opposite the first pressure chamber (16) along the first direction (22), into which the actuating fluid can be introduced, whereby the actuating piston (18) can be acted upon by the actuating fluid and can thereby be displaced in the second direction (24) from the second position to the first position (ST1) of the actuating piston (18) relative to the housing (14); - after a first displacement of the actuating piston (18) in the second direction (24) and before a second displacement of the actuating piston (18) in the first direction (22) immediately following the first displacement and while the actuating piston (18) is in the first position (ST1) as a result of the first displacement, a first pressure increase is brought about in the second pressure chamber (20) by means of the actuating fluid, during which the actuating piston (18) is acted upon with the actuating fluid, whereupon the second displacement is brought about by a second pressure increase being brought about in the first pressure chamber (16) by means of the actuating fluid, during which the actuating piston (18) is acted upon with the actuating fluid. procedure according to claim 1 , characterized in that: - a first valve device (38) which can be supplied with the actuating fluid is provided, which can be switched between: o a first switching position (S1), in which the actuating fluid supplied to the first valve device (38) is introduced into the first pressure chamber (16) via the first valve device (28); and o a second switching position (S2), in which the actuating fluid supplied to the first valve device (38) is introduced into the second pressure chamber (20) via the first valve device (38); and - a second valve device (40) which can be supplied with the actuating fluid is provided, which can be switched between: o a third switching position (S3), in which the actuating fluid supplied to the second valve device (40) is supplied via the second valve device (40) to the first valve device (38), which is thereby supplied with the actuating fluid; and o a fourth switching position (S4), in which a supply of the first valve device (38) with the actuating fluid supplied to the second valve device (40) via the second valve device (40) is omitted. procedure according to claim 2 , characterized in that: - to effect the first pressure increase, the second valve device (40) is in the third switching position (S3) and the first valve device (38) is in the second switching position (S2); and - to effect the second pressure increase, the second valve device (40) is in the third switching position (S3) and the first valve device (38) is in the first switching position (S1). procedure according to claim 3 , characterized in that to effect the first pressure increase, the second valve device (40) is switched from the fourth switching position (S4) to the third switching position (S3) at a first time (t1), wherein to effect the second pressure increase and while the second valve device (40) remains in the third switching position (S3), the first valve device (38) is switched from the second switching position (S2) to the first switching position (S1) at a second time (t2) following the first time (T1). procedure according to claim 4 , characterized in that a time period (G) between the times (t1, t2) is dependent on a temperature and/or is set depending on the temperature. procedure according to claim 5 , characterized in that: - a second time period is determined which lies between the first time (t1) and a determination time following the first time (t1), at which a movement of the switching element following the first time is determined; - the determined second time period is compared as the actual time period with at least one reference time which characterizes the second time period determined in at least one previous, past implementation of the method; and - the time period (G) is increased if it is determined by the comparison that the actual time period is greater than the reference time. procedure according to claim 4 , characterized in that: - a first time period is determined which lies between the first time (t1) and a determination time following the first time (t1), at which a movement of the switching element following the first time (t1) is determined; - the determined first time period is compared as the actual time period with at least one reference time which characterizes the first time period determined in at least one previous, past implementation of the method; and - a second time period (G) between the first time (t1) and the second time (t2) is set depending on the comparison. Method according to one of the preceding claims, characterized in that after the second displacement of the actuating piston (18) in the first direction (22) and before a third displacement of the actuating piston (18) in the second direction (24) immediately following the second displacement, and while the actuating piston (18) is in the second position as a result of the second displacement, a third pressure increase is brought about in the first pressure chamber (16) by means of the actuating fluid, during which the actuating piston (18) is acted upon with the actuating fluid, whereupon the third displacement is brought about by a fourth pressure increase being brought about in the second pressure chamber (20) by means of the actuating fluid, during which the actuating piston (18) is acted upon with the actuating fluid. Method according to one of the preceding claims, characterized in that the respective pressure increase is brought about by introducing a quantity of the actuating fluid into the respective pressure chamber (16, 20). Actuating device (12) for actuating a shifting element of a transmission (10) for a drive train of a motor vehicle, wherein the actuating device (12) is designed to carry out a method according to one of the preceding claims.

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