WO2013075687A2

WO2013075687A2 - Hydraulic actuating system

Info

Publication number: WO2013075687A2
Application number: PCT/DE2012/001060
Authority: WO
Inventors: Ekkehard Reibold; Martin Vornehm; Markus Baehr; Alexander ESSIG; Lukas Holzer; Johannes Moosheimer; Werner Schmitt; Thorsten ESSIG
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2011-11-24
Filing date: 2012-11-06
Publication date: 2013-05-30
Also published as: CN103975173A; WO2013075687A3; CN103975173B; JP6422928B2; JP6238902B2; JP2014533815A; JP2017062043A

Abstract

Method for checking a correct filling of a hydraulic actuating system, more particularly a hydraulic clutch system, and a method for detecting faults in a hydraulic clutch actuating system and in a friction clutch actuated therewith, wherein the hydraulic clutch actuating system has a piston, which can be actuated by a control unit by means of an actuator, in a cylinder with a pressure means, a first sensor for detecting the pressure of said pressure means and a second sensor for detecting the position of the actuator along an actuator path.

Description

Hydraulic actuation system

The invention relates to a method with the features according to the preamble of

Claim 1 and a hydraulic actuating system with the features according to the preamble of claim 13.

The invention serves to monitor the correct filling of a hydrostatic

Actuating system in particular a hydrostatic clutch system in service so for example in a service workshop.

Hydrostatic clutch systems are designed with a clutch actuator having a pressure sensor, this is shown for example in Figure 1, in DE 10 2010 047 800 A1 and DE 10 2010 047 801 A1. The clutch actuator is a so-called hydrostatic clutch actuator HCA (Hydrostatic Clutch Actuator). Under such a hydrostatic actuator is an actuator with a hydrostatic transmission path, for example, a pressure line with hydraulic fluid to understand. The pressure in the pressure line is detected by the pressure sensor. If an associated element is to be moved by the hydrostatic actuator, hydraulic fluid is moved in the transmission path or the pressure line, for example caused by a master cylinder which moves a slave cylinder coupled by the hydraulic fluid. If the element is to hold its position, the hydraulic fluid in the transmission path rests so that there is a hydrostatic state of the hydraulic fluid that gives its name to this actuator.

Hydraulic clutch systems, such as a Hydraulic Clutch Actuator (HCA) used as a clutch disengaging system, must be air-free to ensure proper operation. It is therefore known to carry out a vacuum filling during initial commissioning of a motor vehicle equipped with a hydraulic clutch release system. In case of service - for example, in a service workshop - such complex tools are usually not available, so that by means of appropriate workshop procedures are specified procedures that allow a comparison with the initial commissioning equivalent refilling the hydraulic clutch release system. Decisive in the filling is always, regardless of the type of filling, that the line to be filled completely filled and thus no residual air is available.

Confirmation copy | Due to component tolerances, the specification of the filling quantity or the filling pressure can only be used to a limited extent here. Befüllvorgänge in which residual air remains in the hydraulic route, according to the prior art - as described for example by the German patent application with the file number 10 2011 087 684.7 and the German patent application with the file number 10 2011 087 652.9 - not sufficiently good of completely filled systems without residual air can be distinguished. However, such residual air should also be able to be detected during operation of the vehicle in the transmission path or the pressure line in which only hydraulic fluid should actually be present. In general, it would be desirable to be able to detect any gaseous components which are or form in the transmission path or the pressure line. Basically, a so-called sniffer opening - also referred to as Schnüffelbohrung - provided to a surge tank for the removal of such gaseous fractions has long been known in the art and also in DE 10 2010 047 800 A1 and DE 10 2010 047 801 A1 but also in the German patent application with the file number 10 2011 103 774.1 is described. For this purpose, the clutch control must drive the clutch actuator into a specific position relative to the sniffer opening so that venting of the transmission path can take place by releasing a connection between the transmission path and expansion tank via the sniffer opening and venting can take place.

The term "residual air" is to be understood in the context of this document as all other gaseous substances in the hydraulic transmission path of a hydraulic actuation system, in particular a clutch or transmission actuators.

The difference between two path differences, which result for each two pressure values P1 and P2, is very low for the cases clutch "standard" (transmission path contains no residual air) and clutch "residual air" (transmission path contains residual air), so that these cases according to the state The technology can not be distinguished with sufficient certainty.

When replacing couplings in service - for example, in a service workshop - no vacuum pressure filling of the hydrostatic coupling system is performed. There, the hydraulic plug is vented by means of a bleeding procedure (position ramps for continuous closing and opening of the coupling). This deaeration process must be monitored and ultimately terminated. The present invention has for its object to provide a method for monitoring the correct filling of a hydraulic actuation system, in particular a hydrostatic clutch system without the use of a vacuum pressure filling in the service - for example, in a service workshop - to propose. In particular, a method for the reliable detection of residual air in the hydraulic actuation system is to be developed.

The object is achieved by a method having the features according to claim 1 and a hydraulic actuating system having the features according to claim 13.

With the method according to the invention and the hydraulic actuating system according to the invention, the detection of gaseous substances, in particular of residual air in a hydraulic transmission path, can be further improved.

In procedural terms, the object is also achieved by the method described below.

The terms position-pressure curve and path-pressure curve are used interchangeably in this document. The terms path or position refer to the Aktorweg along which, the clutch moving part of the actuator - for example, a piston in the master cylinder - moves.

According to the invention, a method for checking a correct filling of a hydraulic actuating system with a piston actuated by a control unit by means of an actuator in a cylinder, a first sensor for detecting the pressure in the cylinder and a second sensor for detecting the position of the actuator along an actuator path, characterized in that for checking a correct filling of the hydraulic actuating system with a pressure medium, the following checking steps are carried out:

Moving the actuator up to a predetermined maximum actuator position and detecting the pressure at the maximum actuator position, comparing the detected pressure with a predetermined maximum pressure value, wherein the checking step is considered successful, if the detected pressure coincides with a predetermined maximum pressure value within a first tolerance range otherwise, the verification step is considered unsuccessful and there is an incorrect fill, • determining the maximum pressure gradient of a position-pressure characteristic in a predetermined range of the characteristic curve, wherein the verification step is considered to be successful if the determined maximum pressure gradient is greater than a predetermined pressure gradient threshold, taking into account a second tolerance range, otherwise the verification step is considered unsuccessful go through and there is an incorrect filling,

• determining position-pressure curves up to two position-pressure curves, comparing the two position-pressure curves, whereby the checking step is considered successful if both position-pressure curves match within a third tolerance range, otherwise the Verification step as unsuccessful and there is an incorrect filling, where there is a correct filling, if all three verification steps are passed successfully.

Falling below the pressure gradient threshold by the maximum pressure gradient is still safe air in the system. The concrete determination of the value of this threshold value must be left to the skilled person since the technical individual case has to be taken into account.

In a particularly preferred embodiment of the invention, it is provided that the comparison of the two position-pressure characteristics is carried out on two temporally successively determined position-pressure curves.

In a further particularly preferred embodiment of the invention, it is provided that the comparison of the two position-pressure characteristics is carried out such that it is determined whether there is a displacement of the two position-pressure characteristics relative to one another.

In a further preferred embodiment of the invention, it is provided that the comparison of the two position-pressure characteristics is carried out such that it is determined whether a shift of the time-later-determined position-pressure characteristic compared to the previously determined position-pressure curve towards smaller actuator positions.

In a further preferred embodiment of the invention, it is provided that the comparison is carried out by comparing two position values, which consist of the two Result position-pressure curves at a common, predetermined reference pressure value respectively.

In a further preferred embodiment of the invention, it is provided that the comparison is carried out by comparing two tactile points, which result from the two position-pressure characteristics in each case.

In a further particularly preferred embodiment of the invention it is provided that a venting is caused by the control unit, if there is an incorrect filling. This will be done immediately afterwards or at the next opportunity.

In a further particularly preferred embodiment of the invention, it is provided that the maximum pressure gradient is determined by moving the clutch in the direction of closing by means of the actuator along the Aktorweges.

In a further preferred embodiment of the invention, it is provided that the maximum pressure gradient is determined by moving the coupling in the direction of closing by means of the actuator along the Aktorweges in a predetermined position range around the sniffer bore. In this case, for example, the fluid-side end face of the piston in the cylinder can be used to determine the actuator travel.

In a further alternative preferred embodiment of the invention, it is provided that the maximum pressure gradient is determined by moving the clutch in the direction of closing by means of the actuator along the Aktorweges at a predetermined pressure value, wherein the predetermined pressure value is preferably between 0.5 bar and 6 bar , The concrete determination of the value of the predetermined pressure value must be left to the skilled person as the technical case is to be considered.

In a further embodiment of the invention is alternatively or additionally provided that the maximum pressure gradient by moving the clutch in the closing direction by means of the actuator along the Aktorweges in a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably from 0 bar to 5 , 5 bar is determined. The concrete determination of the given pressure range must also be left to the skilled person as the technical case is to be considered. In a further preferred embodiment of the invention it is provided that the method for checking the correct filling after a refilling or refilling of the hydraulic actuating system is carried out with the pressure medium.

In a further particularly preferred embodiment of the invention it is provided that the method for checking the correct filling for checking the availability of the hydraulic actuating system is carried out at regular intervals.

In a further preferred embodiment of the invention it is provided that the method for checking during certain driving situations is performed by actuation of the hydraulic actuating system.

In a further preferred embodiment of the invention, it is provided that the method for checking the correct filling by means of a test bench computer or by means of a tester or by means of a control device of the device in which the hydraulic actuating system is installed is performed.

In a further embodiment of the invention it is provided that the result of a correct and / or an incorrect check is stored in a fault memory and / or displayed by a display.

In device technical terms, the object is also achieved by the following

described hydraulic actuation system solved.

According to the invention, a hydraulic actuation system with one of a

Control unit proposed by means of an actuator operable piston in a cylinder, a first sensor for detecting the pressure in the cylinder and a second sensor for detecting the position of the actuator. According to the invention, a method described above is carried out to check a correct filling of the hydraulic actuating system with a pressure medium.

In a particularly preferred embodiment of the invention it is provided that the hydraulic actuation system is a hydraulic clutch actuation system. In a further preferred embodiment of the invention it is provided that the hydraulic actuation system is a hydraulic transmission actuation system.

However, such a hydraulic actuation system can not only be used in hydraulic clutch actuation systems or hydraulic transmission actuation systems, but also in gear actuators in transmission systems, as an actuation system in engine systems for throttle bodies, ancillaries and accessory drives, as an actuation system in Abgasführungs- and charging systems, in brake systems and for use in commercial vehicles or construction machines are usefully used.

Further advantages and advantageous embodiments of the invention are the subject of the following figures and their description.

Figure 1 shows a schematic structure of a hydrostatic coupling system

Figure 2 path-pressure curve at different air flow in the hydraulic route

FIG. 3 Maximum pressure gradient in the lower pressure range of the four path-pressure characteristics from FIG. 2

In Figure 1, the structure of a hydraulic clutch system 1 is shown schematically using the example of a hydraulic, hydrostatic clutch actuator (HCA) shown schematically. The hydraulic clutch system 1 comprises on the encoder side 15, a control unit 2, which drives an actuator 3. In a change in position of the actuator 3 and the piston 19 in the cylinder 4 along the Aktorweges to the right, the volume of the cylinder 4 is changed, whereby a pressure P is built up in the cylinder 4, via a pressure medium 7 via a hydraulic line 9 to the slave side 16 of the hydraulic coupling system 1 is transmitted. The hydraulic line 9 is adapted with respect to its length and shape of the installation space situation of the vehicle. On the slave side 16 causes the pressure P of the pressure means 7 in a cylinder 4 'a path change, which is transmitted to a clutch 8 to actuate this. The pressure P in the cylinder 4 on the encoder side 15 of the hydraulic clutch system 1 can be determined by means of a first sensor 5. The first sensor 5 is preferably a pressure sensor. The path traveled by the actuator 3 along the Aktorweges is determined by means of a second sensor 6. An embodiment of the invention is a method for evaluating the pressure increase when closing the clutch immediately in the area of the sniffer bore.

When closing the clutch, the path-pressure characteristic is determined, four such path-pressure curves are shown in Figure 2 (110, 120, 130, 140). In Figure 2, both the closing (each upper part of the curves) of the clutch as well as the opening (each lower part of the waveforms) of the clutch, each with a typical hysteresis effect is shown. To reduce interference, the displacement and pressure signals are not directly analyzed but slightly filtered (e.g., PT1 filter).

From the filtered signals, the pressure gradient (ratio of pressure difference to

Distance difference). Alternative methods (e.g., Kalman filters) may also be used to determine the pressure gradient.

If there is still air in the hydraulic plug, you will get a small pressure gradient when closing the clutch in the area of the sniffer bore.

Method for evaluating the maximum achievable pressure, the maximum pressure gradient when closing the clutch directly in the area of the sniffer bore and the stability of the path-pressure curve.

As part of the venting procedure, the clutch is regularly opened from fully open, i. Open snuff hole and thus hydraulic compensation possible until fully closed, i. maximum distance or maximum permitted pressure reached, moved and then reopened.

• Level 1: Monitoring the maximum pressure that can be reached

With a lot of air in the hydraulic section, the maximum requested pressure 180 (40 bar in FIG. 2) is not reached at maximum actuator position 170 (22 mm in FIG. 2) (path-pressure curve 140 in FIG. 2). As the amount of air in the hydraulic line decreases, the maximum achievable pressure increases until finally the maximum requested pressure is reached (path-pressure curve 130 in FIG. 2).

• Level 2: Monitoring the maximum pressure gradient when closing the clutch immediately in the area of the sniffer bore When closing the clutch, after closing the sniffer bore, a first increase in pressure occurs up to the area of the leaf spring preload (about 5 bar in FIG. 2). According to the method as described for example in German Patent Application 10 2011 087 652.9, the maximum pressure gradient is determined in this area and used here for monitoring. FIG. 3 shows the maximum pressure gradients 210, 220, 230, 240 determined for the respective path-pressure characteristic 110, 120, 130, 140. The maximum pressure gradient must exceed a predetermined threshold value 250 (eg 3 bar / mm in FIG. 3) to go through this monitoring stage successfully. However, the criterion is not yet sufficient for the detection of an optimal venting (path-pressure curve 120 in Figure 2).

The maximum pressure gradient can be determined as follows:

If there is still air in the hydraulic plug, you will get a small pressure gradient when closing the clutch in the area of the sniffer bore. For evaluation, two alternatives A and B are available:

A. At fixed pressure (eg 2 bar), the pressure gradient is compared to a fixed threshold. When falling below the threshold value is still safe air in the system. This is communicated to the clutch control, so that a further venting can be triggered. According to this course of process A, the clutch actuator 3 is thus moved in the direction of clutch closure into a position, so that a predetermined pressure from the pressure range of preferably 0.5 to 6 bar is particularly preferably a predetermined pressure of 2 bar. In this position, the pressure gradient is determined, for example, from the immediately previously measured travel and pressure values or, alternatively, small movements in the direction of closing the clutch are carried out in the region of the predetermined pressure in order to obtain measured values for determining the pressure gradient in the range of the predetermined pressure. This determined pressure gradient applies to the further course of the process as the maximum pressure gradient. Subsequently, the determined maximum pressure gradient is compared with a predetermined pressure gradient threshold value 250. If the value of the determined maximum pressure gradient is smaller than the predetermined pressure gradient threshold value 250, it can be assumed that gaseous components are present in the transmission path. The concrete definition of the value of the predetermined pressure as well as the concrete definition of the value of the pressure gradient threshold 250 must be left to the skilled person as the technical individual case of the hydraulic actuation system of the clutch so- how the properties of the gaseous fractions are to be considered with regard to pressure. The skilled person will specify a pressure value at which the expected pressure gradient around the sniffer bore is particularly large.

B. In the lower position range (eg extended area around the sniffer bore, ie when the liquid-side face of the piston 19 in the cylinder 4 is in the extended area of the sniffer opening 18) and / or in the lower pressure range (eg 0-5 bar), the maximum pressure gradient 210 of the filtered path-pressure characteristic 110 determines. This is compared to a fixed threshold 250. Falling below the threshold 250 is still safe air in the system. This is communicated to the clutch control, so that a further venting can be triggered. According to this course of process B, therefore, the clutch actuator 3 is moved in the direction of clutch closure into a position, so that the liquid-side end face of the piston 19 in the cylinder 4 is at the beginning of a predetermined position range of the extended region of the sniffer opening 18, wherein under the extended region of the sniffer bore Position range is meant around the sniffer bore, in which experience, the largest pressure gradient is expected, as is the case for example in Figure 2 or Figure 3 preferably in the position range -2.5 mm to +12.0 mm. As an alternative or in addition to specifying the position range, the clutch actuator 3 is moved in the direction of clutch closure into a position in which the lowest pressure (beginning of the predetermined pressure range) from a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably between 0 bar and 5.5 bar is present. In the predetermined position range of the extended range of the sniffer opening or alternatively in the predetermined pressure range or alternatively in the presence of both a position from the predetermined position range and in the presence of pressure from the predetermined pressure range, the maximum pressure gradient present in the respective predetermined range is determined by this predetermined range is traversed by means of the actuators - in the direction of clutch closing - and a path-pressure curve is determined from the then the maximum pressure gradient for the predetermined range is determined. Subsequently, the determined maximum pressure gradient is compared with a predetermined pressure gradient threshold value 250, which preferably has the same value as in process profile A. If the value of the determined maximum pressure gradient is smaller than the predefined pressure gradient threshold value 250, it can be assumed, as in process profile A, that gaseous components are present in the transmission path. The concrete determination of the predetermined position range around the sniffer bore, the concrete specification of the predetermined pressure range and the concrete determination of the value of the pressure gradient threshold 250 must be left to the person skilled in the art the technical individual case of the hydraulic actuation system of the coupling as well as the properties of the gaseous portions with regard to pressure are to be considered. The skilled person will specify areas in which the expected pressure gradient around the sniffer bore is particularly large.

• Level 3: Monitoring the stability of the path-pressure curve

In the next monitoring stage, it checks if it is consecutive

Venting ramps to shifts the path-pressure curve to smaller actuator positions comes (path-pressure curve 110 compared to path-pressure curve 120 in Figure 2). This comparison is made for simplicity at a given pressure (e.g., 20 bar in Figure 2). The associated actuator positions are saved. If these remain constant at successive ventilation ramps or at least within a narrow tolerance range, the vent can be classified as successful.

Instead of a predetermined pressure, alternatively, the position of the path-pressure curves 110, 120 to be compared can also be evaluated along the entire characteristic curve 110, 120.

As a further alternative, the comparison can be evaluated on the basis of the identified contact point of the respective path-pressure characteristic, as can be determined, for example, according to German patent application with the file reference 10 2011 088 430.0.

• Level 4: Ending the deaeration procedure

If the deaeration is classified as successful, the deaeration procedure can be terminated. In addition, this is communicated to the clutch controller as well as to the tester who initiated the bleed procedure.

The multi-stage method described allows reliable monitoring of the correct filling of a hydrostatic coupling system in the service. With the aid of the step method, it is possible to infer the current bleeding state at any time. This would not be possible when using Level 3 alone.

Proposed is a method for monitoring the correct filling of a hydraulic actuation system, in particular a hydrostatic clutch system based on the evaluation of the maximum achievable pressure, the maximum pressure gradient when closing the clutch directly in the area of the sniffer bore and the stability of the path-pressure curve.

The invention also relates to a method having the features according to the preamble of claim 15.

The invention serves to control a hydrostatic actuation system, in particular a hydrostatic clutch actuation system, in an automated manual transmission, in particular in a dual-clutch transmission.

Hydrostatic clutch systems are designed with a clutch actuator having a pressure sensor and a displacement sensor, this is shown for example in Figure 1, in DE 10 2010 047 800 A1 and DE 10 2010 047 801 A1. The clutch actuator is a so-called hydrostatic clutch actuator HCA (Hydrostatic Clutch Actuator). Under such a hydrostatic actuator is an actuator with a hydrostatic transmission path, for example, a pressure line with hydraulic fluid to understand. The pressure in the pressure line is detected by the pressure sensor. If an associated element is to be moved by the hydrostatic actuator, hydraulic fluid is moved in the transmission path or the pressure line, for example caused by a master cylinder which moves a slave cylinder coupled by the hydraulic fluid. If the element is to hold its position, the hydraulic fluid in the transmission path rests so that there is a hydrostatic state of the hydraulic fluid that gives its name to this actuator.

For the actuation of clutches, in particular dual-clutch systems, the hydrostatic clutch actuator HCA is used as a release system. This consists of a piston, which is controlled by corresponding mechanical connections of an electric motor and actuates the release system of the clutch via a hydraulic path. The couplings are usually - by means of spring device without the help of the clutch actuator - self-opening clutches (normaly open clutch) while they are closed by means of the HCA against the spring force of the spring device. The HCA is - as already stated above - equipped with an internal displacement sensor for detecting the Aktorweges and an internal pressure sensor for detecting the pressure in the hydraulic line. The hydrostatic release system is equipped with a sufficiently large actuator travel reserve to guarantee actuation of the non-automatically adjustable clutch over the entire service life. Clutch wear and / or leakage in the hydrostatic system lead to a deviation between the required clutch torque and the actual transmissible clutch torque; Depending on the cause, either the leakage in the hydrostatic system must be repaired in the workshop or the worn coupling parts replaced. Currently there is no method for HCA systems to detect the wear of the clutch or the failure of the hydraulic coupling, ie a leakage between the clutch actuator and clutch engagement device. Also, no distinction is made between the two possibilities of error. For the driver, only the consequence, ie non-compliance with the required clutch torque, is noticeable.

The troubleshooting in the workshop is associated with great effort. There is no

Fault memory entry. In the case of a clutch failure other repair measures are to be initiated than with a defect of the hydraulic line.

The invention is based on the object, a detection and differentiation of

To allow causes of failure in the event of a clutch failure. A solution is sought which will allow detection of premature clutch wear, as well as the detection of a leakage in the clutch system and the differentiation between these two possibilities of error to facilitate error analysis in the workshop.

This object is achieved by a method according to claim 15.

According to the invention, a method for fault detection in a hydraulic

Clutch actuation system and provided in a thus actuated friction clutch, wherein the hydraulic clutch actuation system operable by a controller by means of an actuator piston in a cylinder with a pressure medium, a first sensor for detecting the pressure of the pressure medium and a second sensor for detecting the position of the actuator along a Aktorweges has. According to the invention, it is provided that a fault is detected in the hydraulic clutch actuation system or in the friction clutch actuated therewith if one or more of the following conditions is or are satisfied: The pressure of the pressure medium at a predetermined position of the actuator is smaller than a predetermined minimum pressure limit value,

The distance between the position of the current sensing point of the clutch and a predetermined position on the actuator travel is less than a predetermined position difference limit value,

The rate of change of the values for the touch point of the clutch, determined within a predetermined period of time ending with the time of the last determination, is greater than a predetermined touch point change speed limit, the rate of change of the touch point being the temporal gradient of the time course of the determined values for the Touch point is,

The engine speed exceeds the sum of an output speed and a predetermined engine speed limit when the clutch torque is increased from a predetermined output clutch desired torque to another predetermined desired clutch torque,

If the rate of change of the values for the coefficient of friction of the clutch, determined within a predetermined period ending with the time of the last determination, exceeds a given coefficient of friction change limit, the rate of change of the coefficient of friction being the temporal gradient of the time course of the values determined for the friction coefficient Friction coefficient is.

In this way, advantageously, a fault in the hydraulic Kupplungsbetäti- system, namely a leakage of the hydraulic clutch actuation system and / or a fault in the friction clutch namely a clutch lining wear can be detected.

The individual conditions represent alternatives to one another. The method according to the invention not only envisages carrying out all the alternatives one after the other but, in a particularly preferred embodiment, is advantageously carried out with only one or more conditions. It is up to the skilled person to select the most preferred condition or conditions, taking into account the technical case. In a further particularly preferred embodiment of the invention

Method is provided that a fault in the hydraulic Kupplungsbetäti- system is detected when a temporal pressure drop at a constant actuator position is greater than a predetermined pressure drop limit.

In this way, it is advantageously possible to detect a fault in the hydraulic clutch actuation system, namely a leak.

In a further particularly preferred embodiment of the invention

Method is provided that is detected on a fault in the hydraulic Kupplungsbetäti- system when one or more of the following conditions is met or are:

A temporal pressure drop at the predetermined position of the actuator at a constant actuator position is greater than a predetermined leakage pressure drop limit value,

• The change over time of the distance between the respectively current sensing point (130, 160) of the clutch (8) and a predetermined position on the Aktorweg is greater than a predetermined leakage position difference-change limit (210), wherein the rate of change of Tactile point is the temporal gradient of the time course of the determined values for the touch point,

The rate of change of the values for the touch point of the clutch, determined within a predetermined time period ending with the time of the last determination, is greater than a predefined leakage touch point change speed limit value.

In this way, an error in the hydraulic clutch actuation system, namely a leakage of the hydraulic clutch actuation system can be advantageously detected according to each of the conditions and a fault in the friction clutch, namely a clutch lining wear that is not present according to each of the conditions. The individual conditions represent alternatives to one another. The method according to the invention not only envisages carrying out all the alternatives one after the other but, in a particularly preferred embodiment, is advantageously carried out with only one or more conditions. It is up to the skilled person to select the most preferred condition or conditions, taking into account the technical case.

In a further particularly preferred embodiment of the invention

A method is provided for detecting a fault in the friction clutch actuated by the hydraulic clutch actuating system when one or more of the following conditions is or is satisfied:

The pressure of the pressure medium at a predetermined position of the actuator is smaller than a predefined minimum pressure limit value and a time pressure drop at the predetermined position of the actuator at a constant actuator position is smaller than a predefined leakage pressure drop limit value,

• The distance between the position of the current sensing point of the clutch and a predetermined position on the Aktorweg is smaller than a predetermined position difference limit and the temporal change in the distance between the respective current over time of the coupling point and a predetermined position on the Aktorweg is smaller as a predetermined leakage position difference change limit, wherein the rate of change of the touch point is the time gradient of the time course of the detected values for the touch point,

The rate of change of the values for the touch point of the clutch, determined within a given period of time ending with the time of the last determination, is greater than a predetermined touch point rate limit and the rate of change that ends within a predetermined time period with the time of the last determination , detected values for the sensing point of the clutch is less than a predetermined leakage Tastpunktungsungsslossgrenzwert. In this way, advantageously, an error in the friction clutch, namely a clutch lining wear, can be detected according to each of the conditions and can be distinguished from a failure in the hydraulic clutch actuation system, namely a leakage of the hydraulic clutch actuation system which is not present according to each one of the conditions.

The individual conditions represent alternatives to one another. The method according to the invention not only envisages carrying out all the alternatives one after the other but, in a particularly preferred embodiment, is advantageously carried out with only one or more conditions. It is up to the skilled person to select the most preferred condition or conditions, taking into account the technical case.

In a further particularly preferred embodiment of the invention

Method is provided that the predetermined position on the Aktorweg is the maximum Aktorweg (120) in the direction of clutch close.

In a further preferred embodiment of the method according to the invention, it is provided that only touch point changes between two temporally successive touch point determinations in the direction of coupling closure are taken into account.

In a further preferred embodiment of the method according to the invention, it is provided that the predetermined engine speed limit value is determined as a function of the output rotational speed and / or the torque difference between the predetermined clutch desired torque and the output clutch desired torque.

In a further preferred embodiment of the method according to the invention, it is provided that the leakage pressure drop limit value and / or the minimum pressure limit value are determined as a function of the predetermined position of the actuator.

In a further preferred embodiment of the method according to the invention, it is provided that the touch point change speed limit value is smaller than the leakage touch point change speed limit value. Further advantages and advantageous embodiments of the invention are the subject of the following figures and their description.

They show in detail:

Figure 1 shows a schematic structure of a hydrostatic coupling system;

Figure 4 pressure-way clutch characteristics by means of which several embodiments of the method according to the invention will be explained

In Figure 1, the structure of a hydraulic clutch system 1 is shown schematically using the example of a hydraulic, hydrostatic clutch actuator (HCA) shown schematically. The hydraulic clutch system 1 comprises on the encoder side 15, a control unit 2, which drives an actuator 3. In a change in position of the actuator 3 and the piston 19 in the cylinder 4 along the Aktorweges to the right, the volume of the cylinder 4 is changed, whereby a pressure P is built up in the cylinder 4, via a pressure medium 7 via a hydraulic line 9 to the slave side 16 of the hydraulic coupling system 1 is transmitted. The hydraulic line 9 is adapted with respect to its length and shape of the installation space situation of the vehicle. On the slave side 16 causes the pressure P of the pressure means 7 in a cylinder 4 'a path change, which is transmitted to a clutch 8 to actuate this. The pressure P in the cylinder 4 on the encoder side 15 of the hydraulic clutch system 1 can be determined by means of a first sensor 5. The first sensor 5 is preferably a pressure sensor. The path traveled by the actuator 3 along the Aktorweges is determined by means of a second sensor 6. In this illustration, the hydraulic clutch system 1 is shown schematically for only one clutch. In the case of a dual clutch system, the second clutch is actuated analogously.

Due to the hydrostatic actuation of the clutch by means of HCA, characteristic coupling characteristic curves (pressure and torque characteristic curve) arise for the respective clutch, which can be represented, for example, in a diagram via the actuator travel or via the applied clutch force (pressure). An actuation of the master piston in the HCA by the internal electric motor follows a pressure change in the hydrostatic system and thus a change in position of the clutch to be actuated. The characteristic coupling torque characteristic is reflected in the pressure signal, which is metrologically recorded and evaluated with the internal pressure sensor located in the HCA. A typical pressure-path characteristic curve of a hydrostatically actuated clutch is shown in curve A FIG.

In Figure 4, curve A represents a typical pressure-displacement curve of a functional coupling at room temperature. By increasing the temperature of the hydraulic fluid in the hydrostatic system undergoes the clutch characteristic shift to lower Aktorpositionen, which is represented by curve B - the required clutch torque is through the fluid expansion in the system is already achieved with smaller actuator paths. In the case of a leakage in the hydrostatic system and / or in the event of premature clutch wear, the characteristic pressure-displacement characteristic is shifted to higher actuator positions, which is represented by curve C - the maximum clutch torque demanded by the driver is no longer achieved, which is noticeably reflected in the driving behavior.

For the detection of the cause of the error "leakage in the hydrostatic path" and / or "premature clutch wear" and the differentiation between the two causes of error, several evaluation routines can be considered: a) Observation of the pressure signal as a function of the HCA actuator travel at maximum actuator travel distance:

A worn coupling and / or a leak in the hydrostatic release system is characterized by a reduced maximum pressure P (Smax) 1150, 1180 with the maximum possible actuator path Smax 1120. The pressure value P (Smax) C 1180 of a defective clutch falls short of the maximum possible actuator travel Smax 1120 a defined minimum pressure - a predetermined minimum pressure limit 1200 - caused by escaping fluid and / or premature wear of the relevant coupling components. By contrast, the defined minimum pressure 1200 of a functional clutch in Smax 1120 and even at smaller actuator positions as Smax is exceeded by the pressure signal P (Smax) A 1150. Falling below the defined minimum pressure 1200 at maximum Aktorwegstrecke Smax 1120 can therefore be assumed that a defective coupling. b) Observation of the actuator path between the clutch checkpoint and the maximum possible actuator link: As an alternative to a), the distance between clutch touch point TP 1130, 1160 (which is permanently adapted) and the maximum possible actuator distance Smax 1120 can be evaluated. With intact couplings, this difference distance is considerably larger (S (TP) A 1140) than with a defective coupling (S (TP) C 1170). Analogous to a), consequently, a limit value - here a position difference limit value 1210 - can be defined and predefined, which, when undershot, characterizes a "leakage in the hydrostatic path" and / or a "premature clutch wear" and indicates a functional clutch when it is exceeded.

The definition of both limit values - the minimum pressure limit value 1200 and the position difference limit value 1210 - must be left to the person skilled in the art, taking into account the individual technical case, in particular with consideration of the coupling dimensioning. c) observation of the touch point adjustment taking into account the direction of change

The clutch control adapts the touch point during the operating time of a clutch to respond to changing operating conditions such as temperature changes, clutch wear, and so on. By observing the rate of change of this touch point adaptation taking into account the direction of change (only touch point changes to higher actuator positions are relevant), a defective coupling can be detected. Excessive touch point changes indicate "leakage in the hydrostatic path" and / or "premature clutch wear". Wear is a lifetime effect. Leakage is a short-term effect. d) observation of the pressure signal with an almost constant Aktorwegstrecke

Another way to detect a "leakage in the hydrostatic path" is to observe the pressure signal at a virtually constant Aktorwegstrecke, in case of leakage, a rapid pressure drop can be observed at the same Aktorposition - caused by the exiting fluid in the hydrostatic system maximum pressure drop value at nearly constant position must ultimately be a leak in the system e) Observation of engine speed

As a further parameter for detecting a defective clutch, the engine speed can be evaluated. For a worn coupling and / or leakage In the hydrostatic system, the required clutch torque is not reached and therefore the torque provided by the engine is not transmitted, which results in an increase or a "route" of the engine speed exceeds the engine speed at a different positive and positive torque limit applied to the output speed, a faulty clutch system can be assumed f) Observation of the clutch friction coefficient

If the clutch coefficient of friction change gradient exceeds a threshold value, this can be used to conclude serious errors in the clutch engagement system.

The evaluation methods a) to c) additionally allow the differentiation between the causes of error "leakage in the clutch system" and "Worn clutch"; Rapid changes in the measured quantities (maximum pressure at Smax, differential distance between touch point and Smax, touch point adaptation values) indicate a leak in the system, while a worn out clutch announces itself much more slowly. By taking account of this fact or by evaluating the change gradient of the relevant measured variable, it is thus possible to make a statement about the cause of the error.

By evaluation of various parameters (pressure signal, path signal, engine speed) or

Evaluation of clutch actuation system model parameters (touch point values, coefficient of friction) can be distinguished between a functional and a defective clutch. Taking account of the measured variable history (change gradients), it is possible to differentiate between the cause of the error "leakage in the clutch system" and "worn clutch" and thus facilitate error analysis in the workshop.

The invention also relates to a method having the features according to the preamble of claim 24 and to a hydraulic actuating system having the features according to the preamble of claim 32.

The invention serves to detect the correct filling of a hydrostatic

Actuating system, in particular a hydrostatic clutch system at the end of the belt and / or while driving. Hydrostatic clutch systems are designed with a clutch actuator having a pressure sensor, this is shown for example in Figure 1, in DE 10 2010 047 800 A1 and DE 10 2010 047 801 A1. The clutch actuator is a so-called hydrostatic clutch actuator HCA (Hydrostatic Clutch Actuator). Under such a hydrostatic actuator is an actuator with a hydrostatic transmission path, for example, a pressure line with hydraulic fluid to understand. The pressure in the pressure line is detected by the pressure sensor. If an associated element is to be moved by the hydrostatic actuator, hydraulic fluid is moved in the transmission path or the pressure line, for example caused by a master cylinder which moves a slave cylinder coupled by the hydraulic fluid. If the element is to hold its position, the hydraulic fluid in the transmission path rests so that there is a hydrostatic state of the hydraulic fluid that gives its name to this actuator.

Hydraulic clutch systems, such as a Hydraulic Clutch Actuator (HCA) used as a clutch disengaging system, must be air-free to ensure proper operation. It is therefore known to carry out a vacuum filling during initial commissioning of a motor vehicle equipped with a hydraulic clutch release system. In case of service, such complex aids are generally not available, so that processes are specified by means of appropriate workshop instructions, which allow a comparison with the initial start-up equivalent refilling of the hydraulic clutch release system. Decisive in the filling is always, regardless of the type of filling, that the line to be filled completely filled and thus no residual air is available. Due to component tolerances, the specification of the filling quantity or the filling pressure can only be used to a limited extent here. Filling operations in which residual air remains in the hydraulic line can not be sufficiently distinguished from completely filled systems without residual air according to the prior art - as described, for example, by German Patent Application No. 10 2010 055 906.7. However, such residual air should also be able to be detected during operation of the vehicle in the transmission path or the pressure line in which only hydraulic fluid should actually be present. In general, it would be desirable to be able to detect any gaseous components which are or form in the transmission path or the pressure line. Basically, a so-called sniffer opening - also referred to as Schnüffelbohrung - provided to a surge tank for the removal of such gaseous fractions has long been known in the art and also in DE 10 2010 047 800 A1 and DE 10 2010 047 801 A1 but also in the German patent application with the file number 10 2011 103 774.1 is described. For this purpose, the clutch control must drive the clutch actuator in a certain position relative to the sniffer opening, so that a venting of the transmission path can take place by a connection between the transmission path and expansion tank is released via the sniffer opening and the venting can take place.

The present invention is based on the object of developing a method for the reliable detection of residual air in a hydraulic actuating system, in particular a hydrostatic coupling system.

The object is achieved by a method having the features according to claim 24 and a hydraulic actuating system having the features according to claim 32.

With the method according to the invention and the hydraulic actuation system according to the invention, the detection of gaseous substances, in particular of residual air in a hydraulic transmission path, can be further improved.

In procedural terms, the object is also achieved by the method described below.

According to the invention, a method for checking a correct filling of a hydraulic actuating system (1) with a piston actuatable by a control unit by means of an actuator in a cylinder, a first sensor for detecting the pressure in the cylinder and a second sensor for detecting the position of the actuator an Aktorweges provided. According to the invention, for checking a correct filling of the hydraulic actuating system with a pressure medium, the maximum pressure gradient of a position-pressure characteristic in a predetermined region of the characteristic curve is provided is determined and if the determined maximum pressure gradient is greater than a predetermined Druckgradientenschwellenwert, a correct filling is present.

In a particularly preferred embodiment of the invention it is provided that an incorrect filling is present when the maximum pressure gradient is smaller than that

Pressure gradient threshold is. When falling below the threshold value is still safe air in the system. The concrete determination of the value of this threshold value must be left to the skilled person since the technical individual case has to be taken into account.

In a further preferred embodiment of the invention it is provided that the maximum pressure gradient by moving the clutch in the closing direction by means of the actuator along the Aktorweges in a predetermined position range to the

Sniffing hole is determined. To determine the Aktorweg can be used in the cylinder, for example, the liquid-side end face of the piston.

In a further alternative preferred embodiment of the invention, it is provided that the maximum pressure gradient is determined by moving the clutch in the direction of closing by means of the actuator along the Aktorweges at a predetermined pressure value, wherein the predetermined pressure value is preferably between 0.5 bar and 6 bar , The concrete determination of the value of the predetermined pressure value must be left to the skilled person as the technical case is to be considered. In a further embodiment of the invention, it is alternatively or additionally provided that the maximum pressure gradient by moving the clutch in the direction of closing by means of the actuator along the Aktorweges in a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably from 0 bar to 5 , 5 bar is determined. The concrete determination of the given pressure range must also be left to the skilled person as the technical case is to be considered.

In a further preferred embodiment of the invention, it is provided that the checking of the correct filling after refilling or refilling the hydraulic actuating system with the pressure medium is carried out.

In a further particularly preferred embodiment of the invention it is provided that the checking of the correct filling for checking the availability of the hydraulic actuating system is carried out at regular intervals.

In a further preferred embodiment of the invention it is provided that the check is carried out during certain driving situations by actuation of the hydraulic actuation system.

In device technical terms, the object is also achieved by the following

described hydraulic actuation system solved.

According to the invention, a hydraulic actuation system with one of a

In a particularly preferred embodiment of the invention it is provided that the hydraulic actuation system is a hydraulic clutch actuation system. In a further preferred embodiment of the invention, it is provided that the hydraulic actuation system is a hydraulic transmission actuation system.

Figure 1 shows a schematic structure of a hydrostatic coupling system;

FIG. 5 shows a path-pressure characteristic with a marked area that is relevant for the check;

Figure 6 path-pressure curve in the lower pressure range with maximum pressure gradient

When closing the clutch, the path-pressure characteristic 310 is determined, such is shown in Figure 5. FIG. 5 shows both the closing (upper curve) of the coupling and the opening (lower curve) of the coupling with a typical hysteresis effect. In FIG. 5, the area which is relevant for the check according to the invention is marked with an ellipse 360. In order to reduce interference, the path and pressure signals 310 are not directly analyzed, but are lightly filtered 320 (e.g., PT1 filters) as shown in Figure 6, in which the relevant region is shown enlarged from that in Figure 5.

A. At fixed pressure (eg 2 bar), the pressure gradient is compared to a fixed threshold. When falling below the threshold value is still safe air in the system. This is communicated to the clutch control, so that a further venting can be triggered. According to this course of process A, the clutch actuator 3 is thus moved in the direction of clutch closure into a position, so that a predetermined pressure from the pressure range of preferably 0.5 to 6 bar is particularly preferably a predetermined pressure of 2 bar. In this position, the pressure gradient is determined, for example, from the immediately previously measured travel and pressure values or, alternatively, small movements in the direction of closing the clutch are carried out in the region of the predetermined pressure in order to obtain measured values for determining the pressure gradient in the range of the predetermined pressure. This determined pressure gradient applies to the further course of the process as the maximum pressure gradient. Subsequently, the determined maximum pressure gradient is compared with a predetermined pressure gradient threshold value. If the value of the determined maximum pressure gradient is greater than the predetermined pressure gradient threshold, it is to be assumed that no gaseous components are present in the transmission path. The Concrete determination of the value of the predetermined pressure and the concrete determination of the value of the pressure gradient threshold must be left to the skilled person as the technical individual case of the hydraulic actuation system of the clutch and the properties of the gaseous fractions are to be considered in terms of pressure. The skilled person will specify a pressure value at which the expected pressure gradient around the sniffer bore is particularly large.

B. In the lower position range (eg extended area around the sniffer bore, ie when the liquid-side face of the piston 19 in the cylinder 4 is in the extended area of the sniffer opening 18) and / or in the lower pressure range (eg 0-5 bar), the maximum pressure gradient 330 of the filtered path-pressure curve 320 determines (see Figure 6). This is compared with a fixed threshold. When falling below the threshold value is still safe air in the system. This is communicated to the clutch control, so that a further venting can be triggered. According to this course of process B, therefore, the clutch actuator 3 is moved in the direction of clutch closure into a position, so that the liquid-side end face of the piston 19 in the cylinder 4 is at the beginning of a predetermined position range of the extended region of the sniffer opening 18, wherein under the extended region of the sniffer bore Position range is meant around the sniffer bore, in which experience has shown that the largest pressure gradient is to be expected, as for example in the position range - 2.5 mm to +2.0 mm is preferably the case in Figure 5 or Figure 6. As an alternative or in addition to specifying the position range, the clutch actuator 3 is moved in the direction of clutch closure into a position in which the lowest pressure (beginning of the predetermined pressure range) from a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably between 0 bar and 5.5 bar is present. In the predetermined position range of the extended range of the sniffer opening or alternatively in the predetermined pressure range or alternatively in the presence of both a position from the predetermined position range and in the presence of pressure from the predetermined pressure range, the maximum pressure gradient present in the respective predetermined range is determined by this predetermined range is traversed by means of the actuators - in the direction of clutch closing - and a path-pressure curve is determined from the then the maximum pressure gradient for the predetermined range is determined. Subsequently, the determined maximum pressure gradient with a predetermined Druckgradientenschwellenwert - which preferably has the same value as in the course of the process A - compared. If the value of the determined maximum pressure gradient is greater than the predetermined pressure gradient threshold value, then - as in method profile A - it can be assumed that there are no gaseous components in the transmission path. The Concrete determination of the specified position range around the sniffer bore, the concrete definition of the predetermined pressure range and the concrete determination of the value of Druckgradientschwellenwerts must be left to the skilled person as the technical case of the hydraulic actuation system of the clutch and the properties of the gaseous fractions are to be considered in terms of pressure , The skilled person will specify areas in which the expected pressure gradient around the sniffer bore is particularly large.

This check can be carried out at the end of the tape in the vehicle and / or gearbox as well as while driving.

Alternatively, it can also be checked whether the requested maximum pressure is reached when closing the clutch. This review is relatively simple and effective. However, the apparent amount of residual air in the hydraulic system is significantly larger than in the pressure gradient method.

Proposed is a method for detecting the correct filling of a hydrostatic coupling system based on the evaluation of the pressure gradient and / or the maximum achievable pressure.

LIST OF REFERENCE NUMBERS

Hydraulic coupling system

control unit

actuator

cylinder

first sensor

second sensor

lever

clutch

hydraulic line

Off-pressure characteristic curve

donor side

recipient side

surge tank

sniff port

piston

filtered path-pressure characteristic

maximum pressure gradient of the filtered path-pressure curve

Pressure [bar]

Actuator path [mm]

mark

Off-pressure characteristic curve

Actuator position [mm], way

Pressure [bar]

maximum actuator position

maximum pressure 210 maximum pressure gradient in the lower pressure range of the path-pressure curve 110

220 maximum pressure gradient in the lower pressure range of the path-pressure curve 120

230 maximum pressure gradient in the lower pressure range of the path-pressure characteristic curve 130

240 maximum pressure gradient in the lower pressure range of the path-pressure curve 140

250 threshold

260 index

270 maximum pressure gradient [bar / mm]

A Pressure-displacement curve "Functional coupling at room temperature"

B Pressure-displacement curve "Functional coupling at elevated temperature"

C Pressure-displacement characteristic "Defective coupling"

1100 pressure [bar]

11 10 Actuator path [mm]

1120 Smax

1130 TP A

1140 S (TP) A

1 150 P (Smax) A

1160 TP C

1170 S (TP) C

1180 P (Smax) C

1200 minimum pressure limit

1210 position difference limit

Claims

claims

1. A method for checking a correct filling of a hydraulic actuating system (1) with one of a control unit (2) by means of an actuator (3) operable piston (19) in a cylinder (4), a first sensor (5) for detecting the pressure in the cylinder (4) and a second sensor (6) for detecting the position of the actuator (3) along an actuator path, characterized in that carried out to check a correct filling of the hydraulic actuating system (1) with a pressure medium (7) the following verification steps become:

Moving the actuator (3) up to a predetermined, maximum actuator position (170) and detecting the pressure at the maximum actuator position (170), comparing the detected pressure with a predetermined maximum pressure value (180), wherein the verification step is considered successful if the detected pressure coincides with a predetermined maximum pressure value (180) within a first tolerance range,

Determining the maximum pressure gradient (210, 220, 230, 240) of a position-pressure characteristic curve (110, 120, 130, 140) in a predetermined region of the characteristic line, wherein the verification step is considered successful if the determined maximum pressure gradient (210 , 220, 230, 240) is greater than a predetermined pressure gradient threshold (250) considering a second tolerance range,

• determining position-pressure curves up to two position-pressure characteristics (110, 120) are present, compare the two position-pressure characteristics (110, 120), wherein the checking step is considered successful if both position- Pressure curves (110, 120) within a third tolerance range, wherein a correct filling is present when all three verification steps are passed successfully.

2. The method according to claim 1, characterized in that the comparison of the two position-pressure characteristics (110, 120) at two temporally successively determined position-pressure characteristics (110, 120) is executed.

3. The method according to any one of claims 1 or 2, characterized in that the comparison of the two position-pressure characteristics (110, 120) is performed Darart that it is determined whether a shift of the two position-pressure characteristics (110, 120) to one another.

4. The method according to any one of the preceding claims, characterized in that the comparison of the two position-pressure characteristics (110, 120) darart is carried out, that it is determined whether a shift in the time later determined position-pressure characteristic (110, 120) compared to the earlier determined position-pressure curve (110, 120) comes to smaller actuator positions.

5. The method according to any one of the preceding claims, characterized in that the comparison is performed by comparing two position values resulting from the two position-pressure curves (110, 120) at a common, predetermined reference pressure value respectively.

6. The method according to any one of the preceding claims, characterized in that the comparison is performed by comparing two tactile points, resulting from the two position-pressure characteristics (1 10, 120) respectively.

7. The method according to any one of the preceding claims, characterized in that a venting by the control unit (2) is caused when an incorrect filling is present.

8. The method according to any one of the preceding claims, characterized in that the maximum pressure gradient is determined by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges.

9. The method according to any one of the preceding claims, characterized in that the maximum pressure gradient by moving the clutch in the direction of closing is determined by the actuator (3) along the Aktorweges in a predetermined position range around the sniffer bore (18).

10. The method according to any one of the preceding claims, characterized in that the maximum pressure gradient is determined by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges at a predetermined pressure value, wherein the predetermined pressure value preferably between 0.5 bar and 6 bar.

11. The method according to any one of the preceding claims, characterized in that the maximum pressure gradient by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges in a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably from 0 Bar is determined to 5.5 bar.

12. The method according to any one of the preceding claims, characterized in that the check of the correct filling after refilling or refilling the hydraulic actuating system (1) with the pressure medium (7) is performed.

13. Hydraulic actuating system (1) with one of a control unit (2) by means of an actuator (3) operable piston (19) in a cylinder (4), a first sensor (5) for detecting the pressure in the cylinder (4) and a second sensor (6) for detecting the position of the actuator (3) characterized in that for checking a correct filling of the hydraulic actuating system (1) with a pressure means (7), a method according to one of the preceding claims is performed.

Hydraulic actuation system (1) according to any one of the preceding claims, characterized in that the hydraulic actuation system (1) is a hydraulic clutch actuation system (1) or a hydraulic transmission actuation system.

15. A method for fault detection in a hydraulic clutch actuation system (1) and in a friction clutch operated therewith (8), wherein the hydraulic clutch actuation system (1) by a control unit (2) by means of an actuator (3) operable piston (19) in a cylinder (4) having a pressure means (7), a first sensor (5) for detecting the pressure of the pressure means (7) and a second sensor (6) for detecting the position of the actuator (3) along an actuator path, thereby indicates that a fault is detected in the hydraulic clutch actuation system (1) or in the friction clutch (8) operated therewith, if one or more of the following conditions is or are met:

The pressure of the pressure medium (7) at a predetermined position of the actuator (3) is smaller than a predetermined minimum pressure limit value (1200),

The distance between the position of the current sensing point (1130, 1160) of the clutch (8) and a predetermined position on the actuator travel is less than a predetermined position difference limit value (1210),

The rate of change of the values for the touch point of the clutch, which is determined within a predetermined period of time of the end of the last determination, is greater than a predefined touch point change speed limit value,

• The engine speed exceeds the sum of an output speed and a given engine speed limit when the clutch torque is set from a given output clutch torque to another

Clutch torque is increased,

If the rate of change of the values for the coefficient of friction of the clutch, determined within a predetermined period of time ending with the time of the last determination, exceeds a predefined coefficient of friction rate limit.

16. The method according to claim 15, characterized in that a fault in the hydraulic clutch actuation system (1) is detected when a time pressure drop at a constant actuator position is greater than a predetermined pressure drop limit.

17. The method according to any one of claims 15 or 16, characterized in that a fault is detected in the hydraulic clutch actuation system (1), if one or more of the following conditions is or are met: A temporal pressure drop at the predetermined position of the actuator (3) at a constant actuator position is greater than a predetermined leakage pressure drop limit value,

The change over time of the distance between the respective actual touch point (1130, 1160) of the clutch (8) and a predetermined position on the actuator path is greater than a predetermined leakage position difference change limit value (1210),

The rate of change of the values for the sensing point of the clutch, determined within a predetermined time period ending with the time of the last determination, is greater than a predetermined leakage touch point rate limit.

18. Method according to one of the preceding claims 15 to 17, characterized in that a fault is detected in the friction clutch (8) actuated by the hydraulic clutch actuation system (1) if one or more of the following conditions is or are met:

• The pressure of the pressure medium (7) at a predetermined position of the actuator (3) is smaller than a predetermined minimum pressure limit (1200) and a temporal pressure drop at the predetermined position of the actuator (3) at a constant actuator position is less than a predetermined leakage pressure drop limit .

• The distance between the position of the current sensing point (1130, 1160) of the clutch (8) and a predetermined position on the Aktorweg is smaller than a predetermined position difference limit (1210) and the temporal change of the distance between the respective current over time in the course of time (1130, 1160) of the clutch (8) and a predetermined position on the Aktorweg is smaller than a predetermined leakage position difference change limit (1210),

The rate of change of the values for the sensing point of the clutch, determined within a given period of time ending with the time of the last determination, is greater than a predetermined tactile sensed rate limit and the rate of change of, within a predetermined time Period of the end of the last determination ends, determined values for the sensing point of the clutch is less than a predetermined leakage Tastpunktungsungsslossgrenzwert.

19. The method according to any one of claims 15 or 17, characterized in that the predetermined position on the Aktorweg the maximum Aktorweg (1120) in the direction of the clutch is closing.

20. The method according to any one of claims 15 or 17, characterized in that only touch point changes between two temporally successive Tastpunktermittlungen in the direction of clutch closure are taken into account.

21. The method according to claim 15, characterized in that the predetermined engine speed limit value is determined as a function of the output speed and / or the torque difference between the predetermined desired clutch torque and the output clutch setpoint torque

22. The method according to any one of claims 15 or 17, characterized in that the leakage pressure drop limit and / or the minimum pressure limit (1200) in dependence on the predetermined position of the actuator (3) is determined.

23. The method according to any one of claims 15, 17 or 18, characterized in that the Tastpunktänderungsgeschwindigkeitsgrenzwert is smaller than the leakage Tastpunktänderungsgeschwindigkeitsgrenzwert.

24. Method for checking a correct filling of a hydraulic actuation system (1) with a piston (19) which can be actuated by a control unit (2) by means of an actuator (3) in a cylinder (4), a first sensor (5) for detecting the pressure in the cylinder (4) and a second sensor (6) for detecting the position of the actuator (3) along a Aktorweges, characterized in that for checking a correct filling of the hydraulic actuating system (1) with a pressure medium (7), the maximum pressure gradient a position-pressure characteristic in a predetermined range of the characteristic is determined and if the determined maximum pressure gradient is greater than a predetermined pressure gradient threshold, there is a correct filling.

25. The method according to claim 24, characterized in that an incorrect filling is present when the maximum pressure gradient is smaller than the pressure gradient threshold value.

26. The method according to claim 25, characterized in that a venting by the control unit (2) is caused when an incorrect filling is present.

27. The method according to any one of the preceding claims 24 to 26, characterized in that the maximum pressure gradient (330) is determined by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges.

28. The method according to any one of the preceding claims 24 to 27, characterized in that the maximum pressure gradient (330) by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges in a predetermined position range around the sniffer bore (18) determined becomes.

29. The method according to any one of the preceding claims 24 to 28, characterized in that the maximum pressure gradient (330) is determined by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges at a predetermined pressure value, wherein the predetermined pressure value preferably between 0.5 bar and 6 bar.

30. The method according to any one of the preceding claims, characterized in that the maximum pressure gradient (330) by moving the clutch in the closing direction by means of the actuator (3) along the Aktorweges in a predetermined pressure range of preferably 0 bar to 7.5 bar particularly preferably from 0 bar to 5.5 bar is determined.

31. The method according to any one of the preceding claims, characterized in that the check of the correct filling after refilling or refilling the hydraulic actuating system (1) with the pressure medium (7) is performed.

32. Hydraulic actuating system (1) with one of a control unit (2) by means of an actuator (3) operable piston (19) in a cylinder (4), a first sensor (5) for detecting the pressure in the cylinder (4) and a second sensor (6) for detection the position of the actuator (3), characterized in that for checking a correct filling of the hydraulic actuating system (1) with a pressure medium (7), a method according to one of the preceding claims is performed.

33. Hydraulic actuation system (1) according to any one of the preceding claims, characterized in that the hydraulic actuation system (1) is a hydraulic clutch actuation system (1) or a hydraulic transmission actuation system.