DE102018008943A1 - Method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator - Google Patents

Abstract

A method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator by means of a piston-cylinder arrangement is disclosed, which is connected to at least one pressure circuit, in which a hydraulic pressure is built up by a pressure generator, by means of a Pressure regulator set and can be relieved via a drain line to a reservoir. In this method, a ventilation cycle is run through with a plurality of cycle sections (ZA), each of which begins with a pressure build-up phase (DAP) and comprises a subsequent pressure relief phase (DEP). The pressure in the pressure circuit is built up slowly in the pressure build-up phase and quickly relieved in the pressure relief phase. This enables rapid, automated venting of such a device without this requiring any additional outlay in terms of device technology.

Description

TECHNICAL AREA

The present invention relates generally to a method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator according to the preamble of claim 1. In particular, the invention relates to a method for venting a device for the hydraulic actuation of a Friction clutch in a transmission for motor vehicles or of friction clutches in a multi-clutch transmission for motor vehicles and / or a device for the hydraulic actuation of actuators in an automated manual transmission for motor vehicles.

Such hydraulic actuation devices are used in large numbers in modern motor vehicles when it comes to automated gearboxes (ASG), double or multi-clutch gearboxes (DKG) or separable transfer and differential gears, gearbox actuators, such as shift forks and gearshift sleeves, with or without a synchronizing device, and (dry - or wet) friction clutches to operate as flexibly and with little friction as possible and with a small space requirement.

STATE OF THE ART

An example of a hydraulic actuating device for actuating clutches in a motor vehicle is from the document EP 2 532 914 A1 known to the present applicant. The publication EP 2 754 911 A1 the present applicant, on the other hand, discloses an example of a hydraulic actuating device for actuating (among other things) at least one transmission actuator in a motor vehicle.

In these actuating devices, piston-cylinder arrangements are used as actuators, which are connected to a pressure generator via a pressure circuit consisting of freely routable pipe and / or hose lines - here in the form of a hydraulic pump connected to a reservoir for hydraulic fluid. In order to generate the mechanical forces to be applied for switching and / or coupling, a hydraulic pressure is generated by means of the pressure generator, the height of which is set by a pressure regulator (valves and / or change in the delivery behavior of the hydraulic pump) and that via the pressure circuit to the piston-cylinder - Arrangement (s) can be created where the hydraulic pressure acts on a hydraulic effective surface of the respective piston in the assigned cylinder. The hydraulic pressure in the pressure circuit can be relieved via a drain line to the reservoir.

Since hydraulic fluids (such as oil or brake fluid in the present case) are incompressible, the pressure acting on the respective hydraulic fluid in the pressure circuit has no influence on its volume and thus on the transmission behavior of the hydraulic fluid in the pressure circuit. As a result, high forces can also be transferred uniformly via the hydraulic fluid in the pressure circuit, so that exact infeed movements for the coupling and switching operations can be effected by means of the actuators hydraulically connected to the pressure circuit.

However, if air bubbles are trapped in such a hydraulic system, the transmission behavior changes or deteriorates. The enclosed air is a compressible gas mixture that is compressed as the pressure increases and acts like a spring. A non-vented hydraulic system therefore has a certain “softness” or compliance, which must be eliminated after initial filling with hydraulic fluid, during maintenance work and, if necessary, during operation by venting the pressure circuit (s). Only then is it possible to effect a uniform, exact infeed movement on the actuators by shifting a defined hydraulic volume in the hydraulic system.

Simple hydraulic systems with only one actuator can usually be easily vented by hand. For this purpose, a vent valve is usually provided at a high point of the hydraulic system, which can be opened if necessary in order to establish a connection between the hydraulic system and the environment. The air in the hydraulic system can then escape to the environment via this connection. On a multi-circuit actuating device with several actuators, however, such manual venting involves considerable effort, both in terms of device technology and in terms of handling, especially since the actuating device is often difficult to access, for example if it is located in the transmission.

In this context the document shows DE 10 2009 002 532 A1 a hydraulic actuating device for a vehicle clutch, with a master cylinder having a master cylinder piston, a container for providing a hydraulic medium and a hydraulic connection between the master cylinder and the container. In this prior art it is proposed to set the master cylinder piston in motion in order to bleed the hydraulic actuating device by means of an active bleeding routine via the hydraulic connection to the container. The movement of the master cylinder piston causes a Fluid flow generated, which should help reduce those adhesive forces through which the air bubbles adhere to a wall of a hydraulic connection between the master cylinder and a slave cylinder for clutch actuation. In this way, the detached air should reach a master cylinder chamber and a sniffer bore in the hydraulic connection to the tank.

A prerequisite for such ventilation is, however, a continuously increasing course of the hydraulic connection between the master cylinder and the slave cylinder in the direction of the master cylinder. Has the hydraulic connection e.g. If there is a high point in front of the master cylinder or only a very slight slope in the direction of the master cylinder, the hydraulic actuation device may not be able to be vented using the active bleeding routine because the air bubbles do not reach the master cylinder space, but only between the master cylinder and the slave cylinder - and be moved back and forth and back.

From the publication US 2009/0032755 A1 Furthermore, a hydraulic system with a hydraulic actuator and a clutch cylinder is known, which are connected to one another via a hydraulic line in which a solenoid valve for holding the hydraulic pressure in the clutch cylinder is provided. A second solenoid valve, which is positioned above the other components of the hydraulic system, is connected to the hydraulic line via a branch. In order to vent air and thus vent the hydraulic system, the second solenoid valve is opened while the hydraulic line and the branch are under pressure by means of the actuator.

A disadvantage of this prior art, however, can be seen in the fact that the second solenoid valve requires a not inconsiderable expenditure in terms of device technology, which is undesirable in the case of such mass-built systems. In addition, a space above the other components of the hydraulic system is required for the second solenoid valve, which space may not be available, which limits the possible uses of such a solution.

The need for adequate ventilation is all the more important for hydraulic actuation devices in which the pressure is not generated via a piston-cylinder arrangement in a quasi-closed system, but according to the dynamic pressure principle by means of a hydraulic pump that continuously supplies hydraulic fluid, as is known from the aforementioned Pamphlets EP 2 754 911 A1 and EP 2 532 914 A1 the applicant is known, who represent the generic state of the art with regard to a preferred structure of the hydraulic actuating device with hydraulic pump and pressure actuator. The supply of hydraulic fluid via the hydraulic pump always carries the risk that air, for example as a result of foam formation, enters the system with the hydraulic fluid that is supplied.

TASK

The invention is based on the object of specifying a method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator, which avoids the above disadvantages and, in particular, compared to the described prior art, rapid, automated venting of such a device enables, without this necessitating an additional expenditure on device technology.

PRESENTATION OF THE INVENTION

This object is achieved by a method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator with the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

A method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator by means of a piston-cylinder arrangement which is connected to at least one pressure circuit in which a hydraulic pressure is built up by a pressure generator, set by means of a pressure actuator and can be relieved via a drain line to a storage container; has, according to the invention, a ventilation cycle with a plurality of cycle sections, each beginning with a pressure build-up phase and comprising a subsequent pressure relief phase, the pressure in the pressure circuit being built up slowly in the pressure build-up phase and being relieved again quickly in the pressure relief phase.

Using venting tests, the inventor was able to verify that hydraulic actuating devices of the above type can be vented particularly well automatically if the pressure in the pressure circuit is changed several times in such a way that the pressure is initially slowly increased (pressure build-up phase) and then quickly decreased again (pressure relief phase). The inventor sees a possible explanation for the resultant, surprisingly strong venting effect in the fact that air present in the pressure circuit, which in the form of air bubbles adheres to wall surfaces of the line sections of the pressure circuit, in the pressure build-up phases is compressed due to the hydraulic pressure present at the phase interfaces between the air bubbles and the hydraulic fluid, each air bubble striving for a spherical shape which offers less contact area to the wall surface of the respective line section. Due to the reduced contact surface to the wall surface, lower adhesive forces act between the air bubble and the wall surface, so that the air bubble can detach from the wall surface and rise upwards. Since the pressure increases only slowly in the pressure build-up phase, there is sufficient time for the above-described process and the air bubbles are not displaced or entrained along the wall surface in the direction of the piston-cylinder arrangement, as would be the case if the pressure increased suddenly would. In the subsequent rapid pressure relief phase, the compressed air bubbles can then expand rapidly, which takes place towards the pressure-relieved side, ie towards the drain line.

Is z. B. in a device for hydraulic actuation of a friction clutch, the hydraulic fluid in a pressure chamber connected to the pressure circuit of the piston-cylinder arrangement against a hydraulic effective surface of the piston, which acts against a clutch spring, can already during the displacement of the hydraulic fluid in the pressure chamber a pressure is built up in the pressure circuit, which - as described above - leads to compression and to an increase in the air bubbles in the pressure circuit. The slowly replenished hydraulic fluid can then infiltrate the compressed and rising or rising air bubbles. When the piston is reset by the clutch spring during or after the rapid pressure relief phase, the air bubbles that were previously infiltrated by the hydraulic fluid and now expanded at the beginning of the pressure relief phase are displaced in the direction of the drain line with the hydraulic fluid displaced out of the pressure chamber.

By repeating the cycle sections according to the invention several times, the air bubbles that are furthest away from the discharge line in the pressure circuit also gradually move in the direction of the discharge line. The venting cycle according to the invention can be automated without any problems, for which purpose only the components of the actuating device (pressure generator, pressure regulator) that are necessary and already present for the hydraulic actuation must be intelligently controlled.

In this way, line sections of the pressure circuit that have a counter-gradient, i.e. do not rise continuously in the direction of the drain line, without venting additional equipment. Costly valves or the like, as provided in the prior art, are therefore also not necessary for this.

In principle, in the ventilation cycle, the pressure build-up phase of a subsequent cycle section can take place directly on the pressure relief phase of the preceding cycle section. However, in particular if the hydraulic fluid tends to foam, the venting process can be accelerated overall if a cycle section includes a pressure-free resting phase after its pressure relief phase before a subsequent cycle section begins its pressure build-up phase. Such pressure-free periods of rest mean that a total of fewer venting cycles are required for venting.

In certain venting cases it can be advantageous if the pressure is maintained for a time between the pressure build-up phase of a cycle section and its pressure relief phase. Particularly with regard to the shortest possible duration of the entire venting cycle, however, it is preferred if the pressure relief phase of a cycle section follows the pressure build-up phase of this cycle section immediately in time.

The hydraulic pressure should preferably be increased continuously in the pressure build-up phase of a cycle section in order to counteract the risk that the air in the pressure circuit will move back. For example, the pressure can be increased degressively or progressively over time. In contrast, with a view to calming the hydraulic fluid, it is preferred, however, if the hydraulic pressure is increased linearly over time in the pressure build-up phase of a cycle section.

Investigations carried out by the inventor have shown that particularly good venting results can be achieved if the pressure build-up phase of a cycle section 10th to 30th times as long as the subsequent pressure relief phase of this cycle section. The pressure build-up phase of a cycle section should particularly preferably last about 20 times as long as the subsequent pressure relief phase of this cycle section.

The aforementioned investigations have also shown that particularly good ventilation results can be achieved in particular with mineral oil as hydraulic fluid if the pressure in the pressure build-up phase of a cycle section over a period of 2 to 10 seconds, e.g. Is increased for 8 seconds while the pressure is briefly released in the pressure relief phase of a cycle section over a period of 0.1 to 0.5 seconds, for example 0.2 seconds.

In addition, it has proven itself in the course of the investigations carried out if the aforementioned pressure-free resting phase of a cycle section lasts 1.5 to 3 times as long as the pressure build-up phase of this cycle section. Expressed in absolute numbers, the pressure-free rest phase of a cycle section should be maintained for a period of at least 3 to 30 seconds in order to obtain good defoaming of the hydraulic fluid.

After a repair or when the hydraulic system is filled for the first time on the assembly line of the automobile manufacturer or the supplier, it is particularly beneficial for a quick filling with hydraulic fluid if a filling process is carried out upstream of the plurality of cycle sections of the ventilation cycle, in which the pressure in the pressure circuit builds up as quickly as is relieved. In this case, a pressure-free holding phase can preferably be maintained between the filling process and the first cycle section of the deaeration cycle in order to promote defoaming of the hydraulic fluid. Since a lot of air is mixed with the hydraulic fluid during the filling process, it has proven to be particularly advantageous if the pressure-free holding phase between the filling process and the first cycle section of the ventilation cycle is longer than the pressure-free rest phase of the cycle sections.

Finally, the invention also includes the use of the above-described method for venting a device for the hydraulic actuation of at least one friction clutch in a gearbox for motor vehicles and / or for venting a device for the hydraulic actuation of actuators in an automated gearbox for motor vehicles.

Figure list

• 1 ein Schaltbild einer Vorrichtung für die hydraulische Betätigung von zwei hier nicht näher gezeigten Reibkupplungen in einem Kraftfahrzeug, mit zwei Druckkreisen, die hydraulisch zwischen einer zweikreisigen Hydraulikpumpe, einem Doppelzentralausrücker für die Reibkupplungen und einem Vorratsbehälter für Hydraulikflüssigkeit geschaltet sind, wobei die Vorrichtung unter Zuhilfenahme eines Entlüftungsverfahrens nach einem ersten Ausführungsbeispiel der Erfindung entlüftet werden kann;
• 2 ein Diagramm zu einem Entlüftungszyklus des Entlüftungsverfahrens nach dem ersten Ausführungsbeispiel der Erfindung, in dem die absoluten Druckverläufe in den zwei Druckkreisen und die normierte Motordrehzahl der Hydraulikpumpe der Vorrichtung gemäß 1 über der Zeit aufgetragen sind, wobei die Teilbilder a) bis e) Vergrößerungen des am höchsten Punkt des zweiten Druckkreises liegenden Details II in 1 zu verschiedenen Zeitpunkten des Entlüftungszyklus zeigen;
• 3 ein Schaltbild einer Vorrichtung für die hydraulische Betätigung von hier nicht näher gezeigten Getriebestellgliedern und einer schematisch angedeuteten Reibkupplung in einem Kraftfahrzeug, mit drei Druckkreisen, die hydraulisch zwischen einer Reversierpumpe, einer Mehrzahl von Stellzylindern für die Getriebestellglieder bzw. einem Kupplungsnehmerzylinder für die Reibkupplung und einem Vorratsbehälter für Hydraulikflüssigkeit geschaltet sind, wobei die Vorrichtung unter Zuhilfenahme eines Entlüftungsverfahrens nach einem zweiten Ausführungsbeispiel der Erfindung entlüftet werden kann; und
• 4 ein Diagramm zu einem Entlüftungszyklus des Entlüftungsverfahrens nach dem zweiten Ausführungsbeispiel der Erfindung, in dem die absoluten Druckverläufe in den den Stellzylindern zugeordneten zwei Druckkreisen und die normierte Motordrehzahl der Reversierpumpe der Vorrichtung gemäß 3 über der Zeit aufgetragen sind, wobei die Teilbilder a) bis f) Vergrößerungen des am höchsten Punkt des ersten Druckkreises liegenden Details IV in 3 zu verschiedenen Zeitpunkten des Entlüftungszyklus zeigen.

The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the attached schematic drawings, the same or corresponding parts being provided with the same reference symbols — optionally supplemented by a dash (') for identifying the second exemplary embodiment. The drawings show:

• 1 a circuit diagram of a device for the hydraulic actuation of two friction clutches in a motor vehicle, not shown here, with two pressure circuits, which are hydraulically connected between a double-circuit hydraulic pump, a double central release for the friction clutches and a reservoir for hydraulic fluid, the device with the aid of a ventilation process can be vented according to a first embodiment of the invention;
• 2nd a diagram of a ventilation cycle of the ventilation method according to the first embodiment of the invention, in which the absolute pressure curves in the two pressure circuits and the normalized engine speed of the hydraulic pump according to the device 1 are plotted over time, the partial images a) to e) enlargements of the detail II in lying at the highest point of the second pressure circle 1 show at different times in the ventilation cycle;
• 3rd a circuit diagram of a device for the hydraulic actuation of transmission actuators not shown here and a schematically indicated friction clutch in a motor vehicle, with three pressure circuits that hydraulically between a reversing pump, a plurality of actuating cylinders for the transmission actuators or a clutch slave cylinder for the friction clutch and a reservoir are switched for hydraulic fluid, wherein the device can be vented with the aid of a venting method according to a second embodiment of the invention; and
• 4th a diagram of a ventilation cycle of the ventilation method according to the second embodiment of the invention, in which the absolute pressure profiles in the two pressure circuits assigned to the actuating cylinders and the normalized engine speed of the reversing pump according to the device 3rd are plotted over time, the partial images a) to f) enlarging the detail located at the highest point of the first pressure circle IV in 3rd show at different times of the ventilation cycle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The 1 shows a device V for the hydraulic actuation of two friction clutches (not shown in detail), as they are in principle from the publication EP 2 532 914 A1 is known to the present applicant. The device V comprises a pressure generator in the form of a two-circuit hydraulic pump P that have an electric pump drive M has two pressure circles DK1 , DK2 that hydraulically to the hydraulic pump P are connected, as well as a storage container VB for hydraulic fluid from which by means of the hydraulic pump P Hydraulic fluid in the pressure circuits DK1 , DK2 is eligible. Starting from the hydraulic pump P has every pressure circle DK1 , DK2 one towards the hydraulic pump P blocking check valve RV1 , RV2 and an electromagnetically actuated Proportional throttle valve PV1 , PV2 as a pressure plate, by means of which the respective pressure circuit DK1 , DK2 to the storage container VB through a drain pipe AL1 , AL2 defined relief can be.

To each of the pressure circles DK1 , DK2 is a piston-cylinder arrangement Z1 , Z2 connected, which are combined in a double central release, ie each of the piston-cylinder arrangements Z1 , Z2 has an annular piston RK1 , RK2 , each a pressure room PC1 , PC2 limit which are independent of each other across the pressure circles DK1 , DK2 are hydraulically loaded. The ring pistons RK1 , RK2 each act in a manner known per se against a diaphragm spring which is only schematically indicated here MF1 , MF2 the otherwise not shown friction clutches. The electric pump drive M who have favourited Proportional Throttle Valves PV1 , PV2 and one pressure sensor each DS1 , DS2 per pressure circle DK1 , DK2 are with a control unit ECU connected, which is the electrical control of the pump drive M and the proportional throttle valves PV1 , PV2 effects and coordinates.

If one of the friction clutches is to be actuated, the following coordination can be briefly referred to this friction clutch: Via the control unit ECU becomes the proportional throttle valve PV1 ( PV2 ) of the corresponding pressure circuit DK1 ( DK2 ) Electromagnetically operated and the pump drive M started, which is in this pressure circle DK1 ( DK2 ) pressure builds up the respective piston-cylinder arrangement Z1 ( Z2 ) acted upon hydraulically, the ring piston RK1 ( RK2 ) via the diaphragm spring MF1 ( MF2 ) actuated the corresponding friction clutch. When the desired pressure is reached in the corresponding pressure circuit DK1 ( DK2 ) can the pump drive M stopped, the pressure between the check valve RV1 ( RV2 ) and the proportional throttle valve PV1 ( PV2 ) of this pressure circuit DK1 ( DK2 ) remains locked and still in the respective piston-cylinder arrangement Z1 ( Z2 ) works. This proportional throttle valve can be adapted to the respective actuation requirements PV1 ( PV2 ) by means of the control unit ECU then be controlled so that the corresponding pressure circuit DK1 ( DK2 ) - and thus the respective piston-cylinder arrangement Z1 ( Z2 ) - to the storage container VB is defined hydraulically relieved. With regard to further details on the structure and function of such a device V at this point be expressly on the publication EP 2 532 914 A1 referred.

In the following, with reference to the 2nd the method for venting the device described above V are explained. In the diagram according to 2nd are the pressure profiles (in bar) for the two pressure circuits DK1 (dotted line "Pressure clutch 1") and DK2 (narrow dashed line "pressure clutch 2") of the device V according to 1 as well as the standardized motor speeds (broad dashed line "motor speed" in% related to the maximum motor speed) of the electric pump drive M the two-circuit hydraulic pump P during a venting of the device V over time ( t in seconds). As will be described in more detail below, the diagram is according to 2nd in particular a ventilation cycle with a plurality n of cycle sections ZA _n according to an essential feature, each with a pressure build-up phase DAP _n begin and a subsequent pressure relief phase DEP _n include, the pressure in the pressure circuit DK1 , DK2 in the pressure build-up phase DAP _n slowly built up and in the pressure relief phase DEP _n is relieved quickly.

The diagram according to 2nd First of all illustrates that when the pressure circuits are filled and vented for the first time DK1 , DK2 with hydraulic fluid of the majority n of cycle sections ZA _n a filling process during the venting cycle BV (Interval t = 0 s to 1.25 s in 2nd ) is connected upstream, at which the pressure in the pressure circuit DK1 , DK2 set up just as quickly as it is relieved.

More specifically, the proportional throttle valve PV1 at time t = 0 s when the hydraulic pump starts P closed quickly, so that in the pressure circuit DK1 existing air in the pressure chamber PC1 the piston-cylinder arrangement Z1 is ousted. Here the air is compressed and collects at the highest point in the pressure chamber PC1 , according to the 1 a line section of the pressure circuit DK1 connected in the direction of a maximum of one point HP1 of the pressure circuit DK1 has a positive slope.

After a short pressure maintenance phase DHP1 in the interval t = 0.25 s to 0.5 s with the hydraulic pump running P the first proportional throttle valve PV1 opened while the second proportional throttle valve PV2 is closed. When opening the first proportional throttle valve PV1 the pressure in the first pressure circuit DK1 via the drain pipe AL1 to the storage container VB relieved quickly. It can be in front of the line section of the first pressure circuit DK1 in the pressure room PC1 Air only in the direction of the drain line AL1 expand. At the same time, the air is by means of the diaphragm spring MF1 preloaded ring piston RK1 from the pressure room PC1 towards the open proportional throttle valve PV1 displaced so that the air mostly through the drain pipe AL1 and the reservoir VB is released to the environment.

The first filling and venting of the second pressure circuit DK2 takes place in an analogous manner, and with a time offset (here: 0.5 s) for the first filling and venting of the first pressure circuit DK1 in the illustrated embodiment. With complete pressure relief of the second pressure circuit DK2 becomes the electric drive M the hydraulic pump P turned off so that the motor speed of the electric drive M dropped to zero at time t = 1.5 s.

Between the filling process BV and the first cycle section ZA _n The venting cycle then becomes a pressure-free holding phase DFHP adhered to in the by the hydraulic pump P no hydraulic fluid in the pressure circuits DK1 , DK2 is promoted. During this interval, the mixtures of air and hydraulic fluid (foams) that may form during the rapid expansion of the air have sufficient time to disintegrate again into their components. At the same time or subsequently, they can still be found in the pressure circles DK1 , DK2 Collect any air bubbles and move up towards the highest points HP1 , HP2 the pressure circles DK1 , DK2 rising up.

Now the cycle sections already mentioned above close ZA _n of the venting cycle. The also in 2nd shown enlargements a) to e) of detail II in 1 show examples of the cycle section ZA _{n + 1} of the ventilation cycle in a schematic manner a line section at the highest point HP2 of the pressure circuit DK2 . Each of the enlargements a) to e) provides a snapshot at the highest point HP2 represent how they are during the cycle section ZA _{n + 1} for the respective print at the respective time t results. Corresponding snapshots at the highest point HP1 of the pressure circuit DK1 also the pressure curve during the cycle section ZA _n assign.

Like the interval from t = 11 s to 13.75 s in the diagram of the 2nd can be seen before the beginning of the cycle section ZA _{n + 1} the electric pump drive M the hydraulic pump P accelerates until it has reached a normalized engine speed of 30% at time t = 11.25 s. Then in the pressure build-up phase DAP _{n + 1} the hydraulic pressure in the second pressure circuit DK2 by slowly closing the proportional throttle valve PV2 over time t continuously, in particular linearly increased. This is a relatively slow pressure build-up phase DAP _{n + 1} takes about 2.5 s in the illustrated embodiment, but can generally take a predetermined time from a preferred range of 2 s to 10 s.

In the snapshot taken at time t = 11.5 s according to the enlargement a), it is at the highest point HP2 of the pressure circuit DK2 to detect air that has already been compressed slightly by the hydraulic pressure of approx. 5 bar that is present at the phase interfaces between air and hydraulic fluid. The enlargements b) and c) at the times t = 12.75 s and t = 13.75 s show that at a pressure of approx. 20 bar and approx. 40 bar to an air bubble LB compressed air. The volume of the air bubble, which decreases with increasing pressure, can be clearly seen here LB .

As the arrows in magnifications b) and c) indicate, it will be at the highest point HP2 air bubble that decreases with increasing pressure LB from which towards the pressure chamber PC2 moving hydraulic fluid slowly infiltrates. The space previously occupied by the air in the line section fills with hydraulic fluid. At the same time, hydraulic fluid is fed into the pressure chamber when the second clutch is actuated PC2 the piston-cylinder arrangement Z2 shifted without being at the highest point HP2 collected air (air bubble LB ) in the direction of the pressure chamber PC2 is transported.

At time t = 13.75 s, the time immediately following the pressure build-up phase DAP _{n + 1} the pressure relief phase DEP _{n + 1} of the cycle section ZA _{n + 1} initiated. For this, the proportional throttle valve PV2 in the pressure circle DK2 opened again quickly. As a result, the hydraulic pressure in the pressure circuit drops DK2 as in the interval t = 13.75 s to 14 s of the diagram in 2nd displayed quickly to zero over a period of 0.25 s, which is in a preferred range of 0.1 s to 0.5 s for the duration of the pressure relief phase DEP _n of a cycle segment ZA _n lies.

In the illustrated embodiment, the pressure build-up phase DAP _{n + 1} of the cycle section ZA _{n + 1} thus 10 times longer than the subsequent pressure relief phase DEP _{n + 1} . This ratio lies at the bottom of a preferred range, which is characterized in that the pressure build-up phase DAP _n of a cycle segment ZA _n 10th to 30th times as long as the pressure relief phase DEP _n this cycle section ZA _n . The relatively small ratio of pressure build-up given in this embodiment DAP _{n + 1} to pressure relief phase DEP _{n + 1} is due in particular to the fact that according to the diagram 2nd to illustrate the vent cycle several cycle sections ZA _n should be presented sufficiently clearly. However, this ratio is more preferably larger, so that the pressure build-up phase DAP _n of a cycle segment ZA _n e.g. 20 times as long as the subsequent pressure relief phase DEP _n this cycle section ZA _n .

Since the in the enlargement c) of 2nd shown, highly compressed air bubble LB from towards the pressure chamber PC2 displaced hydraulic fluid is now in the space in the hydraulic line, which was taken up by the air alone before the compression of the air, the added hydraulic fluid against the air bubble LB at. As a result of the rapid opening of the proportional throttle valve PV2 in the pressure relief phase DEP _{n + 1} hydraulic fluid flows increasingly through the drain line AL2 in the storage container VB off, so the pressure in the hydraulic line from the piston-cylinder assembly Z2 in the direction of the proportional throttle valve PV2 seen drops. At the same time, the diaphragm spring works MF2 the clutch via the piston-cylinder arrangement Z2 a return movement of the hydraulic fluid in the direction of the drain line AL2 .

This is the air bubble LB towards the pressure chamber PC2 the piston-cylinder arrangement Z2 supported by the hydraulic fluid and can as in the enlargement d) 2nd shown only in the direction of the drain pipe AL2 expand. Associated with this is the expanding air corresponding to the enlargement e) of 2nd carried away by the hydraulic fluid due to the force of the diaphragm spring MF2 from the pressure room PC2 the piston-cylinder arrangement Z2 is pushed back.

Should that be in the pressure circle DK2 before the drain pipe AL2 seated proportional throttle valve PV2 are lower than the highest point HP2 of the pressure circuit DK2 , as in the illustrated embodiment, it is useful if the volume of the line section between the highest point HP2 of the pressure circuit DK2 and the proportional throttle valve PV2 is smaller than that from the pressure room PC2 the piston-cylinder arrangement Z2 volume of hydraulic fluid pushed back.

To the hydraulic fluid as already after the filling process BV the pressure circles DK1 , DK2 in the pressure-free holding phase DFHP to calm down, includes every cycle section ZA _n the venting cycle after its pressure relief phase DEP _n a pressure-free resting phase RP _n before a subsequent cycle section ZA _{n + 1} the venting cycle with its pressure build-up phase DAP _{n + 1} begins. According to the diagram 2nd pressure-free resting phase shown in the interval t = 14 s to 17.25 s RP _{n + 1} of the cycle section ZA _{n + 1} For example, it is held over a period of 3.25 seconds, depending on the nature of the hydraulic fluid, it can be advantageous if the pressure-free rest phase RP _n up to 30 seconds. The pressure-free resting phase lasts in the above interval RP _{n + 1} 1.3 times as long as the pressure build-up phase DAP _{n + 1} of the cycle section ZA _{n + 1} . The relatively small ratio of rest phase given here RP _{n + 1} to pressure build-up phase DAP _{n + 1} is in turn due to the fact that according to the diagram 2nd to illustrate the vent cycle several cycle sections ZA _n should be presented sufficiently clearly. However, this ratio is more preferably greater, so that the pressure-free resting phase RP _n of a cycle segment ZA _n eg between 1.5 and 3 times as long as the pressure build-up phase DAP _n this cycle section ZA _n .

As for the rest of the filling process BV a lot of air from the pressure circuits DK1 , DK2 is displaced and the pressure is built up just as quickly as it is relieved, there is increased foaming in the hydraulic fluid, which is countered by the fact that the pressure-free holding phase DFHP longer than the pressure-free resting phase RP _n the cycle sections ZA _n is. The number n the cycle sections ZA _n Finally, a ventilation cycle depends in particular on the size of the hydraulic system and the properties of the hydraulic fluid used and can be, for example, between 2 and 10.

In the following, with reference to the 3rd and 4th the second embodiment will only be described to the extent that it differs from that with reference to FIG 1 and 2nd described first embodiment differs significantly and it seems necessary for an understanding of the ventilation process. While in the first embodiment, the venting method for venting a device V is used for the hydraulic actuation of friction clutches in a multi-clutch transmission for motor vehicles, the venting method is used in the second embodiment, in particular for venting a device V ' used for the hydraulic actuation of actuators in an automated manual transmission for motor vehicles.

The 3rd shows such a hydraulic device V ' for the actuation of a friction clutch FC ' and of three transmission actuators (not shown) with a pressure generator, namely one from an electric pump drive M ' driven hydraulic pump P ' , whose pumping direction by reversing the direction of rotation of the electric pump drive M ' is reversible and the two pump connections PA1 ' , PA2 ' having. The pump connections PA1 ' , PA2 ' are each over a pressure circuit DK1 ' , DK2 ' on parallel, double-acting piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' hydraulically connected as gear actuators. The piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' each have a gear actuator piston GK1 ' , GK2 ' , GK3 ' on, which are operatively connected in a manner known per se to the transmission actuator elements, not shown. The gear actuator pistons GK1 ' , GK2 ' , GK3 ' delimit a print space on opposite sides PC1 ' , PC4 '; PC2 ' , PC5 '; PC3 ' , PC6 ' that with one or the other pressure circuit DK1 ' respectively. DK2 ' is hydraulically connected. More specifically, the pressure rooms PC1 ' , PC4 '; PC2 ' , PC5 '; PC3 ' , PC6 ' each at its highest point with a line section of the respective pressure circuit DK1 ' respectively. DK2 ' hydraulically connected that towards a highest point HP1 ' , HP2 ' of the respective pressure circuit DK1 ' respectively. DK2 ' increases.

Furthermore, the pressure circles DK1 ' , DK2 ' with a storage container VB ' via one suction line each SL1 ' , SL2 ' hydraulically connected to one in the direction of the reservoir VB ' blocking check valve RV3 ' respectively. RV4 ' is provided. Depending on the direction of rotation of the electric pump drive M ' the hydraulic pump P ' is thus via the intake line SL1 ' respectively. SL2 ' Hydraulic fluid from the reservoir VB ' sucked in and via the hydraulic pump P ' to the parallel, double-acting piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' promoted to the gear actuator piston GK1 ' , GK2 ' , GK3 ' to act hydraulically for an actuator movement, depending on the pump direction on one side or the other.

Here is each of the piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' a locking device R1 ' , R2 ' , R3 ' with one locking element each SE1 ' , SE2 ' , SE3 ' assigned functionally, the spring biased in a locking position preventing an actuator movement and by means of an electrically controllable actuator A1 ' , A2 ' , A3 ' is movable from the blocking position into a release position permitting an actuator movement. The electric pump drive M ' the reversing pump P ' and the actuators A1 ' , A2 ' , A3 ' are also electrically connected to a control unit ECU 'which coordinates the electrical control of these components.

In this respect, it is obvious to the person skilled in the art that the gear actuator pistons are used to generate the desired actuator movements GK1 ' , GK2 ' , GK3 ' mechanically held or released and - depending on the pumping direction of the hydraulic pump P ' - over the pressure rooms PC1 ' , PC4 '; PC2 ' , PC5 '; PC3 ' , PC6 ' can be hydraulically loaded on one side or the other.

How to continue 3rd is at the highest point HP1 ' , HP2 ' of the two pressure circles DK1 ' , DK2 ' a branch to a drain pipe AL1 ' , AL2 ' provided in the reservoir VB ' leads. Between the branch and the respective drain line AL1 ' , AL2 ' is a combination of an aperture DR1 ' respectively. DR2 ' and a check valve RV5 ' respectively. RV6 ' intended. Over the bezels DR1 ' , DR2 ' the hydraulic fluid can flow throttled to the respective pressure circuit DK1 ' respectively. DK2 ' to allow pressure to build up. The towards the pressure circles DK1 ' , DK2 ' blocking check valves RV5 ' , RV6 ' on the other hand, prevent air or hydraulic fluid from being sucked in via the drain lines AL1 ' , AL2 ' , ie runs at a given direction of rotation of the hydraulic pump P ' over the one drain pipe AL1 ' ( AL2 ' ) Hydraulic fluid can drain through the other drain line AL2 ' ( AL1 ' ) due to the check valve RV6 ' ( RV5 ' ) from the storage container VB ' neither hydraulic fluid nor air are sucked in.

The actuation of the friction clutch FC ' takes place at the in 3rd shown device V ' analogous to the clutch actuation in the above with reference to the 1 described device V via a combination of a check valve RV1 ' , Proportional throttle valve PV1 ' and pressure sensor DS1 ' , in the present case the clutch actuation via a switching valve SV ' hydraulically to the pressure circuit DK2 ' connected.

With regard to further details on the structure and function of such a device V ' Finally, at this point, expressly refer to the publication EP 2 754 911 A1 referenced, from which a comparable device for actuating gear actuator elements is known.

The following is with reference to the 4th the method for venting the device described above V ' explained according to the second embodiment. In the diagram according to 4th are the pressure profiles (in bar) for the two pressure circuits DK1 ' (narrow dotted line "Print 1") and DK2 ' (dotted line "pressure 2") of the device V ' according to 3rd as well as the standardized motor speeds (broad dashed line "motor speed" in% related to the maximum motor speed) of the electric pump drive M ' the reversible hydraulic pump P ' during a venting of the device V ' over time ( t in seconds). The hydraulic pump turns when the engine speed is positive P ' in 3rd to supply the pressure circuit DK1 ' counterclockwise while the hydraulic pump P ' at negative engine speeds to supply the pressure circuit DK2 ' in 3rd is driven clockwise.

With regard to the basic sequence of the individual phases of the venting method according to the second exemplary embodiment, reference should first be made expressly to the first exemplary embodiment described above. In particular, the individual cycle sections are also distinguished in the second exemplary embodiment ZA _n the venting cycle in that they each with a pressure build-up phase DAP _n begin and a subsequent pressure relief phase DEP _n have, the pressure in the respective pressure circuit DK1 ' respectively. DK2 ' in the pressure build-up phase DAP _n set up quietly and in the pressure relief phase DEP _n quickly, that is, relieved significantly faster.

When the pressure circuits are filled for the first time DK1 ' , DK2 ' the device V ' become the pressure rooms PC1 ' to PC6 ' the piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' first individually filled with hydraulic fluid and vented. The gear actuator pistons GK1 ' , GK2 ' , GK3 ' the piston-cylinder arrangements that are not to be vented Z1 ' , Z2 ' , Z3 ' remain here by means of the respectively assigned blocking elements SE1 ' , SE2 ' , SE3 ' the locking devices R1 ' , R2 ' , R3 ' fixed, ie only one of the gear actuator pistons is ever used GK1 ' , GK2 ' , GK3 ' emotional. In the interval t = 0 s to 1.5 s of the diagram in 4th is an example of the pressure curve during a filling process BV for the two pressure rooms PC1 ' , PC4 ' the first piston-cylinder arrangement Z1 ' shown. The filling of the further pressure chamber pairs PC2 ' , PC5 '; PC3 ' , PC6 ' takes place in an analogous manner, preferably one after the other.

By rapid acceleration of the electric pump drive M ' the reversing pump P ' in a first direction of rotation counterclockwise in 3rd From the point in time t = 0 s the gear actuator piston becomes GK1 ' the piston-cylinder arrangement to be filled or vented Z1 ' in a first, in 3rd left end position in which it is moved by means of the assigned locking element SE1 ' the locking device R1 ' is fixed so that it is in the pressure chamber PC1 ' a pressure builds up. The air compressed to at least one air bubble initially collects at the highest point in the pressure chamber PC1 ' .

Immediately after reaching a maximum pressure of approx. 40 bar at the time t = 0.5 s becomes the speed of the electric pump drive M ' again until the hydraulic pump comes to a standstill P ' reduced. The pressure in the first pressure circuit DK1 ' this is about the throttle DR1 ' , the open check valve RV5 ' and the drain pipe AL1 ' to the storage container VB ' dismantled. Because the pressure room PC1 ' is now filled with hydraulic fluid, which can be at the highest point of the pressure chamber PC1 ' ascended, at least one air bubble with a pressure drop in the pressure circuit DK1 ' only in the direction of the drain pipe AL1 ' , ie from the pressure room PC1 ' expand out.

This is followed by the electric pump drive M ' accelerated in the opposite direction, so the hydraulic pump P ' clockwise in 3rd is driven to the opposite pressure chamber PC4 ' the piston-cylinder arrangement Z1 ' over the pressure circle DK2 ' to be filled with hydraulic fluid and to be bled. When moving by means of the locking device R1 ' unlocked gear actuator piston GK1 ' to the opposite end position, ie to the right, as shown in 3rd , is from the pressure room PC1 ' towards the drain pipe AL1 ' expanded air with the displaced hydraulic fluid further towards the highest point HP1 ' of the pressure circuit DK1 ' postponed. Here, this air can (at least partially) via the branch to the throttle DR1 ' to the drain pipe AL1 ' reach.

To this extent it is apparent to the person skilled in the art that the pressure spaces PC1 ' to PC6 ' the piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' by repeatedly pushing the gear actuator pistons back and forth GK1 ' , GK2 ' , GK3 ' can be filled with hydraulic fluid and vented, preferably in succession.

After observing the above, on the filling process BV following pressure-free holding phase DFHP can the cycle sections ZA _n of the ventilation cycle. The also in 4th shown enlargements a) to f) of the detail IV in 3rd show examples of the cycle section ZA _n of the ventilation cycle in a schematic manner a line section at the highest point HP1 ' of the pressure circuit DK1 ' . Again, each of the enlargements a) to f) provides a snapshot at the highest point HP1 ' of the pressure circuit DK1 ' represent how they are during the cycle section ZA _n for the respective print at the respective time t results. Corresponding snapshots at the highest point HP2 ' of the pressure circuit DK2 ' of course, the pressure curve during the cycle section ZA _{n + 1} assign.

During the cycle sections ZA _n for venting the line sections of the pressure circuits DK1 ' , DK2 ' remain all gear actuator pistons GK1 ' , GK2 ' , GK3 ' the piston-cylinder arrangements Z1 ' , Z2 ' , Z3 ' by means of the associated locking devices R1 ' , R2 ' , R3 ' locked so that when pressure is applied to the pressure circuits DK1 ' , DK2 ' no air bubbles with the hydraulic fluid back into the pressure chambers PC1 ' to PC6 ' can be moved.

The enlargement a) in 4th now shows an air trap near the highest point HP1 ' of the pressure circuit DK1 ' at time t = 5 s before the first cycle section ZA _n the venting cycle. At this point the electric pump drive is stopped M ' and with it the hydraulic pump P ' so the pressure circle DK1 ' is not yet pressurized. As a result of acceleration of the electric pump drive M ' the pressure in the pressure circuit increases DK1 ' during the first pressure build-up phase DAP _n so that the air inclusion becomes an air bubble LB ' is compressed as in 4th in the enlargements b) - at the time t = approx. 6.2 s - and c) - at the time t = approx. 7.1 s - shown. At the same time, as the pressure increases, the air bubble takes on the shape of a sphere and shrinks as it does so LB ' with correspondingly decreasing wall contact along the wall of the line section upwards until it reaches the highest point HP1 ' of the pressure circuit DK1 ' and near the throttle DR1 ' arrives as in 4th in the enlargement d) - at time t = 7.75 s - shown.

The pressure in the pressure circuit DK1 ' now by rapidly lowering the motor speed of the electric pump drive M ' in the subsequent pressure relief phase DEP _n relieved quickly, then the air bubble expands in accordance with the enlargement e) 4th - at time t = 8 s - through the choke DR1 ' towards the drain pipe AL1 ' . Maybe in front of the check valve RV5 ' Retained air becomes the next time pressure is applied to the same pressure circuit DK1 ' with the throttle during pressurization DR1 ' flowing hydraulic fluid according to the magnification f) in 4th - at time t = 17.2 s immediately before or at the beginning of the next cycle section ZA _{n + 2} for the pressure circuit DK1 ' - via the drain line AL1 ' to the storage container VB ' transported there.

The venting of the second pressure circuit DK2 ' takes place in the cycle sections ZA _{n + 1} , ZA _{n + 3} , etc. in an analogous manner. Incidentally, the ratio of the duration of the individual phases of each cycle section ZA _n and their absolute temporal lengths refer to the above description of the first embodiment. The same applies to the venting of the switching valve SV ' to the second pressure circuit DK2 ' connected hydraulic section for actuating the clutch FC ' .

In the regular switching operation of the device V ' according to 3rd every time a gear actuator piston is actuated GK1 ' , GK2 ' , GK3 ' a pressure room PC1 ' , PC2 ' , PC3 ' ( PC4 ' , PC5 ' , PC6 ' ) of the respective piston-cylinder arrangement Z1 ' , Z2 ' , Z3 ' emptied while the opposite pressure chamber PC4 ' , PC5 ' , PC6 ' ( PC1 ' , PC2 ' , PC3 ' ) the piston-cylinder arrangement Z1 ' , Z2 ' , Z3 ' is filled with hydraulic fluid. When emptying the pressure rooms PC1 ' , PC2 ' , PC3 ' respectively. PC4 ' , PC5 ' , PC6 ' in switching operation, it is located at the highest points of the pressure rooms PC1 ' , PC2 ' , PC3 ' respectively. PC4 ' , PC5 ' , PC6 ' collecting air towards the highest points HP1 ' respectively. HP2 ' of the hydraulic system in the respective line sections. Because the gear actuator pistons GK1 ' , GK2 ' , GK3 ' Moving to the desired end positions "without pressure" due to wear and tear builds up in the pressure circuits DK1 ' , DK2 ' little or no pressure. The trapped air is therefore not compressed, but only by moving the hydraulic fluid to rise and escape via the respective drain line AL1 ' , AL2 ' excited.

A method for venting a device for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator by means of a piston-cylinder arrangement is disclosed, which is connected to at least one pressure circuit, in which a hydraulic pressure is built up by a pressure generator, by means of a Pressure regulator set and can be relieved via a drain line to a reservoir. In this method, a ventilation cycle is run through with a plurality of cycle sections, each of which begins with a pressure build-up phase and comprises a subsequent pressure relief phase. The pressure in the pressure circuit is built up slowly in the pressure build-up phase and quickly relieved in the pressure relief phase. This enables rapid, automated venting of such a device without this requiring any additional outlay in terms of device technology.

Reference symbol list

A1 '

Actuator

A2 '

Actuator

A3 '

Actuator

AL1, AL1 '

Drain pipe

AL2, AL2 '

Drain pipe

DK1, DK1 '

Pressure circle

DK2, DK2 '

Pressure circle

DR1 '

Throttle valve

DR2 '

Throttle valve

DS1, DS1 '

Pressure sensor

DS2

Pressure sensor

ECU, ECU '

Control unit

FC '

Friction clutch

GK1 '

Gear actuator piston

GK2 '

Gear actuator piston

GK3 '

Gear actuator piston

HP1, HP1 '

highest point of the pressure circle

HP2, HP2 '

highest point of the pressure circle

LB

Air bubble

M, M '

electric pump drive

MF1

Diaphragm spring

MF2

Diaphragm spring

P, P '

Hydraulic pump (pressure generator)

PV1, PV1 '

Proportional throttle valve (pressure regulator)

PV2

Proportional throttle valve (pressure regulator)

PC1, PC1 '

Pressure room

PC2, PC2 '

Pressure room

PC3 '

Pressure room

PC4 '

Pressure room

PC5 '

Pressure room

PC6 '

Pressure room

R1 '

Locking device

R2 '

Locking device

R3 '

Locking device

RK1

Ring piston

RK2

Ring piston

RV1, RV1 '

check valve

RV2

check valve

RV3 '

check valve

RV4 '

check valve

RV5 '

check valve

RV6 '

check valve

SE1 '

Locking element

SE2 '

Locking element

SE3 '

Locking element

SL1 '

Suction pipe

SL2 '

Suction pipe

SV '

Switching valve

V, V '

contraption

VB, VB '

Storage container

Z1, Z1 '

Piston-cylinder arrangement

Z2, Z2 '

Piston-cylinder arrangement

Z3 '

Piston-cylinder arrangement

n

number

BV

Filling process

DAP _n ,

Pressure build-up phase

DAP _n

Pressure build-up phase

DEP _n

Pressure relief phase

DHP1

Pressure maintenance phase

DHP2

Pressure maintenance phase

DFHP

pressure-free holding phase

RP _n

pressure-free resting phase

ZA _n

Cycle section

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2532914 A1 [0003, 0012, 0029, 0031]
• EP 2754911 A1 [0003, 0012, 0056]
• DE 102009002532 A1 [0008]
• US 2009/0032755 A1 [0010]

Claims (15)

Method for venting a device (V; V ') for the hydraulic actuation of at least one friction clutch and / or at least one transmission actuator by means of a piston-cylinder arrangement (Z1, Z2; Z1', Z2 ', Z3') connected to at least one Pressure circuit (DK1, DK2; DK1 ', DK2') is connected, in which a hydraulic pressure is built up by a pressure generator (P; P '), set by means of a pressure actuator (PV1, PV2; P', DR1 ', DR2') and can be relieved via a drain line (AL1, AL2; AL1 ', AL2') to a storage container (VB; VB '), characterized by a ventilation cycle with a plurality (n) of cycle sections (ZA _n ), each with a pressure build-up phase (DAP _n ) begin and include a subsequent pressure relief phase (DEP _n ), the pressure in the pressure circuit (DK1, DK2; DK1 ', DK2') slowly building up in the pressure build-up phase (DAP _n ) and quickly again in the pressure relief phase (DEP _n ) is relieved. Procedure according to Claim 1 Characterized in that a cycle section (ZA _n) after its pressure relief phase (DEP _n) comprises a pressure-free rest period (RPn) before a subsequent cycle section (ZA _{n + 1) (n} DAP _{+ 1)} with its pressure build-up phase begins. Procedure according to Claim 1 or 2nd Characterized in that the pressure relief phase (DEP _n) of a cycle section (ZA _n) of the pressure increase phase (DAP _n) of this cycle portion (ZA _n) temporally follows immediately. Method according to one of the preceding claims, characterized in that the hydraulic pressure in the pressure build-up phase (DAP _n ) of a cycle section (ZA _n ) is increased continuously, in particular linearly, over time. Method according to one of the preceding claims, characterized in that the pressure build-up phase (DAP _n ) of a cycle section (ZA _n ) lasts 10 to 30 times as long as the subsequent pressure relief phase (DEP _n ) of this cycle section (ZA _n ). Procedure according to Claim 5 , characterized in that the pressure build-up phase (DAP _n ) of a cycle section (ZA _n ) lasts 20 times as long as the subsequent pressure relief phase (DEP _n ) of this cycle section (ZA _n ). Method according to one of the preceding claims, characterized in that the pressure in the pressure build-up phase (DAP _n ) of a cycle section (ZA _n ) is increased over a period of 2 to 10 seconds. Method according to one of the preceding claims, characterized in that the pressure in the pressure relief phase (DEP _n ) of a cycle section (ZA _n ) is released over a period of 0.1 to 0.5 seconds. Procedure according to one of the Claims 2 to 8th , characterized in that the pressure-free resting phase (RP _n ) of a cycle section (ZA _n ) lasts 1.5 to 3 times as long as the pressure build-up phase (DAP _n ) of this cycle section (ZA _n ). Procedure according to one of the Claims 2 to 9 , characterized in that the pressure-free resting phase (RP _n ) of a cycle section (ZA _n ) is maintained over a period of 3 to 30 seconds. Method according to one of the preceding claims, characterized in that when the pressure circuit (DK1, DK2; DK1 ', DK2') is filled for the first time with hydraulic fluid from the plurality (n) of cycle sections (ZA _n ) of the venting cycle, a filling process (BV) is connected upstream, where the pressure in the pressure circuit (DK1, DK2; DK1 ', DK2') builds up as quickly as it relieves pressure. Procedure according to Claim 11 , characterized in that a pressure-free holding phase (DFHP) is maintained between the filling process (BV) and the first cycle section (ZA _n ) of the venting cycle. Procedure according to Claim 12 , characterized in that the pressure-free hold phase (DFHP) is longer than the pressure-free rest phase (RP _n ) of the cycle sections (ZA _n ). Use of the method according to one of the preceding claims for venting a device (V) for the hydraulic actuation of a friction clutch in a transmission for motor vehicles or of friction clutches in a multi-clutch transmission for motor vehicles. Use of the method according to one of the preceding claims for venting a device (V ') for the hydraulic actuation of actuators in an automated manual transmission for motor vehicles.

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