Method for determining the wear condition of a concentric release bearing and a concentric release bearing

Abstract

Method for determining the wear condition of a concentric release bearing (10), in which • a tilting movement of a piston (14) relative to a cylinder (12) is detected using a sensor (16) and provided as a sensor signal (34), • wherein the sensor signal (34) is evaluated and a tipping value is thereby determined, • where the tilt value is compared with stored data to determine the wear condition of the concentric release bearing (10).

Description

[0001] The invention relates to a method for determining the wear condition of a concentric release bearing and to a concentric release bearing.

[0002] Various methods for determining the wear condition of a concentric release bearing are known in the prior art. These methods involve visual or measurement testing after removal of the release bearing. Another method detects a pressure drop in the pressure medium. However, in this case, release bearing failure is imminent.

[0003] Similarly, sensor-based methods are known for rod-guided piston-cylinder assemblies, which can be used to determine the wear of individual components. These are based, for example, on pressure sensors, acceleration sensors, capacitive sensors, or displacement sensors. These methods are disclosed in WO 2013 / 152807 A1, DE 10 2015 210716 A1, US 2013 / 0276516 A1, WO 2007 / 115631 A1, and DE 10 2014 225872 A1.

[0004] Especially in commercial vehicles, failures of individual components or assemblies that lead to the vehicle's breakdown are particularly detrimental. This is especially true in the case of a defective release bearing, as the vehicle is then no longer roadworthy.

[0005] The task is therefore to provide a method and a release mechanism that allows the wear condition of the concentric release mechanism to be determined in real time in a simple manner.

[0006] This problem is solved by the method according to claim 1. Advantageous embodiments of the method are explained in the dependent claims.

[0007] This method is particularly suitable for determining the wear condition of a concentric release bearing. It is especially advantageous for pneumatic release bearings.

[0008] Such a release mechanism, particularly a concentric release mechanism, comprises a cylinder and a piston. The piston is arranged to be axially movable relative to the cylinder. Together, the cylinder and piston enclose a pressure chamber. This pressure chamber, or working chamber, is filled with a pressure medium, particularly a hydraulic or pneumatic fluid, which is pressurized to initiate a release process, i.e., to actuate the release mechanism. This causes the piston to perform an axial movement relative to the cylinder. The axial movement of the piston is transmitted via a release bearing to a clutch, usually a diaphragm spring, to actuate the friction clutch. By adjusting the pressure, the friction clutch can be opened and closed as desired.

[0009] The working chamber is sealed by one or more seals located between the cylinder and the piston. These seals wear over the service life of the release bearing due to the numerous axial relative movements and the ingress of dirt between the piston and the cylinder. The piston can tilt relative to the cylinder within a limited range, a phenomenon also known as rocking clearance. This rocking clearance depends, among other things, on the wear condition of the seals and any guide bands. In other words, the piston can perform a rocking motion around a rocking axis, which is perpendicular to a concentric axis of the release bearing.

[0010] The rocker arm play can be measured statically on a removed release bearing in its resting state. This rocker arm play increases with increasing service life or the number of engagement cycles of the release bearing. Beyond a certain value, the seal can no longer fully perform its sealing function, resulting in leaks between the piston and the cylinder. These leaks are an indication of impending release bearing failure.

[0011] Due to the forces introduced into the drivetrain, particularly those of the engine, the piston performs a wobbling or tilting motion. This wobbling or tilting motion of the piston, in turn, depends on the release bearing clearance, i.e., the tilting motion of the piston relative to the cylinder. Accordingly, the wobbling or tilting motion of the piston also increases with increasing release bearing clearance.

[0012] Accordingly, a tilting movement of the piston relative to a cylinder is detected by a sensor and provided as a sensor signal. In particular, it is sufficient if the tilting clearance or the tilting between the piston and cylinder can be extracted from the sensor signal in some way.

[0013] The sensor signal is then evaluated and a tilt value is determined, whereby the tilt value is compared with stored data to determine the wear condition of the concentric release bearing.

[0014] For this purpose, the sensor signal is evaluated, and a tilt value is determined. This tilt value represents the tilting or wobbling movement of the release bearing. The tilt value is then compared with stored data to determine the wear condition. In particular, the tilt value describes the range of variation in the sensor signal.

[0015] The tilt value can also be compared to a defined wear value, which serves as a wear indicator. If the tilt value is lower than the wear value, the wear condition is acceptable. If the tilt value exceeds the wear value, the wear condition is no longer acceptable. The release bearing is therefore worn and must be replaced.

[0016] Alternatively, the sensor signal can be compared with corresponding stored condition signals for different wear states. Such condition signals could, for example, be empirically determined measurement data that serve as a reference.

[0017] This method allows the wear condition of the release bearing, and thus of the actuation system, to be determined in real time. Furthermore, the wear condition can be determined during vehicle operation. The release bearing is preferably in operation during the execution of the method.

[0018] Advantageous implementation variants of the process are explained below.

[0019] It is proposed that stored test data be used when evaluating the sensor signal.

[0020] This test data can, for example, correspond to wear values, which are compared with the sensor signals measured in real time and the resulting tilt values. The determined tilt values ​​can then be compared with wear values. If the tilt value matches the target value, it can be stated that a specific wear state has been reached. Alternatively, the tilt value can also be compared with interpolated target values, a graph, a function, or a table.

[0021] It is proposed that a remaining service life be determined from the wear condition, in particular the tilting value.

[0022] This can be determined, for example, using tables based on experience. Alternatively, the calculation can also be performed mathematically, particularly with knowledge of an initial tilt value, a final tilt value, and, if applicable, a wear function that describes the number of disengagement cycles or service life in relation to the development of the tilt value. This also allows for the calculation of a service life, especially in the form of mileage, until a replacement is necessary. This is particularly advantageous for commercially used motor vehicles or utility vehicles, as upcoming service and maintenance procedures can be planned much more effectively.

[0023] A particular advantage is that the test data is stored locally or externally.

[0024] Locally stored test data is saved, in particular, in a memory unit on the vehicle and / or the release mechanism. This data can then be used at any time to determine the wear condition of the release mechanism. The wear condition can thus be determined at any time, and immediate feedback can be provided to the driver or an information system, such as a digital fleet management system.

[0025] The test data can also be stored externally, for example in a testing device, on the internet, in an intranet, or in the cloud. This allows the test data to be retrieved as needed, i.e., at the time when the wear condition needs to be determined. This is particularly advantageous if the determination is based on empirical data, as it allows the latest findings to be incorporated into the calculation.

[0026] In a particularly advantageous embodiment, when the release bearing reaches a defined wear state, information about the condition of the release bearing and thus of the actuation system is communicated, for example via the device or to an information system.

[0027] This defined wear condition could, for example, be the point at which a replacement or maintenance of the release mechanism is imminent or necessary to prevent system failure and, consequently, vehicle or commercial vehicle failure. This information can be transmitted to the vehicle driver, the owner or keeper, a repair shop, the vehicle manufacturer, or an information system. The information can also include, among other things, the remaining mileage until recommended or necessary maintenance. This ensures that a failure of the release mechanism and the actuation system is avoided.

[0028] It is proposed that the sensor be designed as a displacement sensor of the piston.

[0029] Both hydraulic and pneumatic release mechanisms typically incorporate a position sensor that determines the piston's position relative to the cylinder. This allows the system to be electronically adjusted to the desired release position, enabling automatic shifting. The sensor signal generated by such a position sensor also includes information about the piston's wobble or tilting motion relative to the cylinder. This sensor signal and its associated processing are described and explained in more detail in the figure description.

[0030] In another variant, the sensor can be designed as a tilt sensor. Such a tilt sensor is, in particular, an additional sensor to the displacement sensor, specifically designed to detect the tilting movement of the piston relative to the cylinder. This allows for the reliable detection of even strong wobble or tilting movements. Filtering out the tilt from the displacement sensor's measurement signal is therefore unnecessary.

[0031] The task is also solved via a concentric release mechanism according to the features of claim 7.

[0032] This concentric release mechanism comprises at least one piston, one cylinder, and one sensor. The sensor, and in particular the concentric release mechanism, are configured to perform a method according to any one of claims 1 to 6.

[0033] The concentric release bearing has already been described in detail in the preceding and subsequent sections.

[0034] The procedure and the concentric disengagement mechanism are explained below using several figures as examples. These show: Fig. 1 a concentric release bearing in cross-section; Fig. 2a - f Sensor signals of a concentric release bearing in different wear states over the service life of a concentric release bearing; Fig. 3 a flowchart of a procedure for determining the wear condition of a concentric release bearing.

[0035] In the Fig. Figure 1 shows a cross-sectional view of a concentric release mechanism 10. The release mechanism 10 comprises a cylinder 12, a piston 14, and a sensor 16. The piston 14 and the cylinder 12, which, among other things, provides the guide tube, enclose a working chamber 18. Seals 20 are arranged between the piston 14 and the cylinder 12, sealing the working chamber against the environment.

[0036] The working chamber 18 is filled with a pressure medium, in this case a pneumatic fluid. The fluid pressure can be increased and decreased as desired to cause axial movement of the piston 14 relative to the cylinder. Fig. 1 to the left, to provide. The movement takes place along a concentric axis A of the release lever.

[0037] The axial relative movement of the piston 14 with respect to the cylinder 12 is transmitted via a release bearing 22 to a friction clutch (not shown), in particular to a diaphragm spring of the friction clutch. The friction clutch is actuated by axial movement of the piston 14 and can be opened or closed as desired.

[0038] The actuation of the pneumatic and concentric release 10 is automated, with the sensor 16 providing a signal that enables control of the axial movement of the piston 14. The sensor 16 comprises a position encoder 24 and a position detection device 26. The position encoder 24 is fixed to the piston 14 and moves in concert with it. The position detection device 26 includes electronics and sensors that determine the position of the position encoder 24 and provide it as a sensor signal. In particular, the position of a magnet attached to the position encoder 24 is detected.

[0039] Due to its design and depending on its wear condition relative to cylinder 12, piston 14 can perform a tilting or rocking motion. This is exemplified in the Fig. 1. This is illustrated by lines 28a and 28b, which exemplify the maximum deflection of the tilting states. The tilting occurs about a tilting axis K, which is shown only as an example and for explanatory purposes. The tilting axis K extends perpendicularly to a concentric axis A of the release lever 10.

[0040] Such tilting occurs even when the release bearing is new and changes, particularly increasing, over the release bearing's service life. The seals 20 and the guide bands 21 provide a corresponding elasticity that enables this tilting. The piston 14 can tilt from position 28a to position 28b, as indicated by the lines.

[0041] As the guide bands and seals wear, and thus the number of actuations of the release bearing 10 increases, the tilting play also increases. Due to the increasing wear of the seals and the increasing tilting angle, leaks occur as the seals lift off the corresponding running surface, allowing hydraulic fluid to escape. For example, the radially outer seal 20 lifts off the cylinder's running surface. In this condition, the concentric release bearing is worn and should be replaced as soon as possible. Continued operation can lead to complete sealing failure.

[0042] As already mentioned, this tilting play or tilting angle increases with increasing mileage and increasing wear of the concentric release bearing 10. The tilting play can be measured in particular on a removed release bearing in a static state.

[0043] During operation, corresponding forces act on piston 14 in the drive train, for example, those introduced by a motor. Due to these forces, piston 14 performs a tilting or wobbling motion relative to cylinder 16. Since the position sensor 24 moves in conjunction with the piston, this tilting or wobbling motion is detected by the position sensing device 26 and provided as information within the sensor signal. In particular, the position sensor 24 performs a substantially linear axial movement with respect to the concentric axis A. This movement, which is based on the tilting or wobbling motion, is essentially periodic and can be determined from the sensor signal of sensor 16.

[0044] In the Fig. Figures 2a to f show sensor signals for identical release mechanisms exhibiting different wear states and thus providing different pivoting clearances. These sensor signals and pivoting clearances were determined through measurement tests during dynamic operation of the release mechanism. The pivoting clearances, which characterize the wear state, were determined in a static state. Here, the pivoting clearance corresponds to a measurement taken in a static state, i.e., when the release mechanism was removed and at rest, and represents a measuring length.

[0045] The time is plotted against the respective x-axis (30a to f). The release travel detected by the sensor is plotted against the y-axis (32a to f). The sensor signals (34a to f) show several successive release cycles, in which the piston moves from a rest position in the axial direction, assumes a release position, and then returns to the rest position. The piston remains in the release position for a longer period until another release cycle, represented by the correspondingly rising peaks, is performed.

[0046] As already mentioned, the position sensor 24, depending on the provided tilting clearance and the wear condition of the release bearing, performs an axial movement along the concentric axis A, which essentially describes the tilting or wobbling motion of the piston 14. This tilting or wobbling motion is determined by the width of the sensor signal 34 a to f. During the tilting or wobbling motion of the piston 14, the position sensor 24 periodically travels an axial path, which is expressed by the amplitude 36.

[0047] The fluctuation range 36a to f thus corresponds to the fluctuation provided by the tilting game.

[0048] The range of variation 36a to f is for the Fig. 2a to f are each illustrated by two arrows. Fig. 2a shows a concentric release bearing with a tilting play of 1, which Fig. 2b one with a tilting game of 1.42, which Fig. 2c with a tilting game of 1.72, which Fig. 2d with a tilting game of 2.30, the Fig. 2e with a tilting play of 2.54 and the Fig. 2f with a tilting clearance of 3.13. The tilting clearance here represents a measurement in the removed and static state of the concentric release bearing 10. An increasing tilting clearance indicates increased wear. The values ​​for the tilting clearance are based on the tilting clearance in the new condition, i.e., according to Fig. 2a, standardized.

[0049] A tilting play 1 is essentially provided in the new condition, with increasing wear, see the Fig. 2a to f, the tipping point and the fluctuation range 26a increase. Regarding the Fig. 2a to 2d allows for normal disengagement of the concentric release mechanism. The concentric release mechanism maintains full functionality in this case. In the event of a tilting play according to the Fig. 2e can already be seen from the course of sensor signal 34e, indicating that the fluid pressure within the working chamber drops due to leakage and that the axial movement of the release mechanism is reset due to the pressure loss. This is recognizable by the double peak in the sensor signal during a single release operation. With further increasing wear and play, this effect becomes even more pronounced, as shown in the Fig. 2f is shown on sensor signal 34f. These wear conditions with regard to the Fig. In cases 2e and f, replacing the release bearing is absolutely necessary to prevent failure.

[0050] As already mentioned, the width of the sensor signal 36 increases further with increasing wear, starting from the new state. This width essentially corresponds to the oscillatory movement or the oscillatory motion of the position sensor. In particular, one can see in the Fig. 2f detect the periodic movement of the position sensor, which determines the fluctuation range 36 of the sensor signal.

[0051] The fluctuation range 36 is determined in real time during the operation of the release mechanism 10. The fluctuation range 36 can be determined by evaluating the signal. In particular, a tipping point is provided, which represents a value for the fluctuation range.

[0052] The wear condition of the release bearing is immediately determined from the fluctuation range of 36. As already explained in the general description section, corresponding test data can be stored, which, for example, correspond to previously determined empirical values ​​for fluctuation ranges in various wear conditions.

[0053] The real-time fluctuations of the sensor signal are compared with this test data to determine the wear condition of the release bearing. From this wear condition, a remaining service life can then be calculated. For this purpose, the release bearing's previous wear behavior over its service life can be taken into account. Alternatively, a table can be stored from which the remaining service life can be read or interpolated. Basically, there are various ways to determine the wear condition of the release bearing from the sensor signal and, based on this, to infer the remaining service life.

[0054] In the Fig.Section 3 summarizes the individual steps of the procedure in a flowchart. In the first step, step 40, a sensor signal is provided, which includes information about a tilting movement of the piston 14 relative to the cylinder 12. In particular, the sensor signal is determined during the operation of the release bearing, or during the operation of the drive train.

[0055] In a further step (42), the sensor signal is evaluated to determine the wear condition. This determination is carried out, for example, by comparing the measured range of variation with stored test data. This allows, for instance, the determination of how far the wear has progressed from 0% (new condition) to 100% (discharge clutch failure). Based on the wear condition, a remaining service life can also be calculated, if necessary.

[0056] In a further step (44), information about the wear status is communicated. This could be, for example, a warning light that the driver can read. Alternatively, this information can only be read by a diagnostic system. It can also be transmitted via radio or the internet. This allows the release mechanism to be serviced or replaced in time before failure. Reference sign 10 concentric release bearings 12 cylinders 14 pistons 16 Sensor 18 workroom 20 Seal 21 Guide tape 22 Release bearing 24 position transmitters 26 Position detection device Line 28a 28b line 30a - f x-axis (time) 32a - f y-axis (release path) 34a - f Sensor signal 36a - f Range of variation 40 steps Step 42 Step 44 A concentric axis K tilting axle

Claims

Method for determining the wear condition of a concentric release bearing (10), in which: • a tilting movement of a piston (14) relative to a cylinder (12) is detected using a sensor (16) and provided as a sensor signal (34), • the sensor signal (34) is evaluated and a tilting value is thereby determined, • the tilting value is compared with stored data to determine the wear condition of the concentric release bearing (10). Method according to one of the preceding claims, characterized in that stored test data are used in the evaluation of the sensor signal (34). Method according to claim 2, characterized in that the test data are stored locally or externally. Method according to one of the preceding claims, characterized in that, in the event of a defined wear condition, information about the condition of the release bearing (10) is communicated. Method according to one of the preceding claims, characterized in that the sensor (16) is formed by a displacement sensor of the piston (14). Method according to one of claims 1 to 4, characterized in that the sensor (16) is designed by a tilt sensor. Concentric release mechanism (10) comprising a piston (14), a cylinder (12) and a sensor (16) configured to carry out a method according to one of the preceding claims.

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