DE102017200964A1 - Measuring device and measuring method for detecting mixed friction events and / or stick-slip events - Google Patents

Abstract

The invention relates to a measuring device for detecting mixed friction events and / or stick-slip events on and / or in a rotationally movable component (10), characterized by at least one sensor element (1) for detecting movements (B) in the material of the component ( 10), in particular deformations and / or oscillations on and / or in the component (10), wherein the at least one sensor element (1) is coupled to a data processing device (20) and the data processing device (20) has a computing means (21) for evaluating the frequencies the movements (B), the amplitudes of the movements (B), the changes of the frequencies and / or the changes of the amplitudes, whereby in dependence of the evaluation of the frequencies of the movements (B), the amplitudes of the movements (B), the Changes in the frequencies and / or changes in the amplitudes and in the presence of a predetermined condition, in particular a threshold automatically ei n first signal (S1) on the presence of a mixed friction event and / or a slip-stick event in the component (10) can be generated. The invention also relates to a measuring method.

Description

The invention relates to a measuring device for detecting mixed friction events and / or stick-slip events having the features of claim 1 and to a measuring method for detecting mixed friction events and / or stick-slip events having the features of claim 18.

In mixed friction events, there is a coexistence of solid friction and fluid friction, e.g. inadequate lubrication or at the beginning of the movement of two friction partners (i.e., solids) with lubrication. The sliding surfaces touch at points. In mixed friction, part of the load from the lubricating film, which may be generated elastohydrodynamically or hydrodynamically, and another part from the contacting roughening hills are taken up.

The frictional force in the mixed friction region is speed-dependent and can be used in rotationally movable components, such as, for example, Observe sliding bearings. In this case, the friction force or the friction torque decreases with increasing sliding speed until pure fluid friction occurs and separates the friction surfaces.

As the sliding speed increases further, the frictional force / friction torque then increases again. In the mixed friction region, the wear decreases similarly with the friction torque until the sliding speed has reached the almost wear-free fluid friction. The mixed friction is therefore always undesirable in continuous operation of a rotatable component.

Stick-slip events, also known as stick slip events or friction vibrations, occur when slipping backwards against moving solids. Known examples are creaking doors or similar squeaking noises. Stick-slip events occur when the static friction is appreciably greater than the sliding friction. At the sliding surfaces (i.e., contact surfaces) of the solids involved there is a momentary adhesion and stress that dissolves only after a certain time (e.g., 0.1 s or less). After loosening, there is again a (hydrodynamic) sliding friction. Stick-slip events are one way to capture the mixed friction limit.

Like mixed friction events, stick-slip events are undesirable in machine operation.

It is therefore the task of detecting mixed friction events and / or stick-slip events.

The object is achieved by a measuring device with the features of claim 1.

In this case, at least one sensor element is used to detect movements in the material of a component, in particular deformations and / or vibrations on and / or in the component. The at least one sensor element is coupled to a data processing device, wherein the data processing device has a computing means for evaluating the frequencies of the movements, the amplitudes of the movements, the changes of the frequencies and / or changes in the amplitudes. Depending on the evaluation of the frequencies of the movements, the amplitudes of the movements, the changes of the frequencies and / or the changes of the amplitudes and in the presence of a predetermined condition, in particular a threshold value, the computing means automatically generates a first signal regarding the presence of a mixed friction event and / or a slip-stick event generated in the component. The first signal may then be e.g. used for a statistical evaluation or for control interventions.

In one embodiment, the at least one sensor element is designed as a piezoelectric sensor, as a piezoresistive sensor, structure-borne noise sensor or as a strain gauge. With these sensors, the movements in the material of the component, in particular structure-borne sound to capture. For higher temperature applications, in one embodiment, a langasite crystal is used as the piezoelectric sensor element. In principle, a piezoresistive crystal or another deformation-measuring temperature-resistant sensor element can be used.

In one embodiment, the movements in the material of the component are produced by structure-borne noise due to mixed friction events and / or stick-slip events.

For processing the signals detected by the at least one sensor element, filtering and / or spectral analysis of the signals which were transmitted to the data processing device on the basis of the detected movements, in particular by the detected structure-borne noise, are carried out by the computer. By filtering unwanted frequencies can be suppressed. By means of the spectral analysis, the frequencies characteristic for the mixed friction events and / or stick-slip events can be determined.

In a further embodiment, the incoming data can be evaluated by the computing means over a predetermined number of revolutions of the rotationally moved component. With that taken into account periodic influences on the movements in or on the component.

In a further embodiment, at least two sensor elements are arranged on or in the component, it being possible to generate the first signal via the presence of a mixed friction event and / or a slip-stick event in the component as a function of ascertained differences in the movements detected by the respective sensor elements. The spatial distribution of the sensor elements may account for zones (e.g., load areas) having higher probabilities of occurrence of mixed friction events and / or stick-slip events and zones of correspondingly lower likelihood. The zones of lesser probability may thus form a kind of inherent basis against which the occurrence of mixed friction events and / or stick-slip events can be assessed on an ongoing basis. This may be useful if the condition for triggering the first signal may u.U. can not be determined analytically.

Thus, e.g. a predetermined profile of the frequencies and / or amplitudes and / or the exceeding of a certain threshold for a frequency and / or an amplitude is a predetermined condition, based on which generates a first signal on the existence of a mixed friction event and / or a stick-slip event becomes.

Additionally or alternatively, in one embodiment, a previously empirically determined map on the dependence of the onset of the mixed friction events and / or the stick-slip events can be stored in the computing means. In this case, the influence of operating parameters, in particular the rotational speed of the rotationally movable component and / or the temperature can be detected in particular in the map.

In a further embodiment, the at least one sensor element is coupled to a sliding bearing or a roller bearing as a rotatably movable component. The sliding bearing or the roller bearing may in particular be part of a transmission, in particular a planetary gear. It is also possible for a signal to be generated if a current can be detected by a voltage applied through an electrically insulating coating.

It is also possible, in one embodiment, to process with the computing means meshing frequencies of a gear transmission in correlation to the movements. Furthermore, temperature data, in particular of oil, determined in or on the component can be processed in correlation with the computing means. Thus, further influences on the mixed friction events and / or stick-slip events can be taken into account.

In a further embodiment, depending on the empirical evaluation of the frequencies of the movements, the amplitudes of the movements, the changes in the frequencies and / or the changes in the amplitudes and in the presence of a predetermined condition, in particular a threshold automatically a second signal on the presence damage in the component produced. This can e.g. lead to the decommissioning of the affected component.

Due to the loads occurring, an embodiment of the measuring device can be coupled to at least one component in or on a gas turbine, in particular an aircraft engine.

The object is also achieved by a measuring method with the claims of claim 18.

• 1 eine schematische Darstellung einer Ausführungsform einer Messvorrichtung und eines Messverfahrens;
• 2 eine schematische Darstellung einer Ausführungsform eines rotatorisch beweglichen Bauteils mit einem Sensorelement;
• 3 ein Ablaufdiagramm einer Ausführungsform für die Erfassung oder Vorhersage eines Mischreibungsereignisses und / oder eines Stick-Slip-Ereignisses.

In connection with the embodiments illustrated in the figures, the invention will be explained. It shows

• 1 a schematic representation of an embodiment of a measuring device and a measuring method;
• 2 a schematic representation of an embodiment of a rotatably movable component with a sensor element;
• 3 a flowchart of an embodiment for the detection or prediction of a mixed friction event and / or a stick-slip event.

In 1 is schematically a measuring device for detecting mixed friction events and / or stick-slip events on a rotationally movable component 10 shown. With the measuring device can also perform a corresponding measurement method.

In the present embodiment, the component 10 be a sliding bearing, which is arranged for example in a planetary gear of an aircraft engine. In other embodiments, the rotationally movable component 10 also be a rolling bearing, such as a ball bearing. In operation, these rotationally movable components lead 10 Rotary movements, with different lubrication properties may be present. The point here is to recognize whether and / or when a mixed friction event and / or a stick-slip event occurs.

In 1 is shown schematically that I have the component 10 in operation around a rotation axis 11 rotates.

On the component 10 is a sensor element 1 arranged, with the movements B (please refer 2 ) in the material of the component 10 , in particular a deformation and / or a vibration on and / or in the component 10 can be detected. It can also be about the detection of a cyclic rotary motion (triggered by slip stick) go. or in the component 10 but about movements B in the material, which manifests itself for example by deformations or vibrations (structure-borne sound).

The movements B , which may be relatively small and high frequency, in the illustrated embodiment by a sensor element 1 detected, which is designed as a piezoelectric sensor. Alternatively, piezoresistive sensors or strain gauges can be used.

The piezoelectric electrical sensor element 1 makes use of the piezoelectric effect. By piezoelectricity is meant the interaction between electrical quantities (eg polarization, electric field or surface charge) with mechanical quantities (eg mechanical stresses, strains, deformations) in solids. A piezo element as a sensor element 1 As in the present embodiment, a device that uses the described piezoelectricity to detect mechanical quantities due to the movements, in particular deformations B arise.

The sensor element 1 is preferably in the load range of the sliding bearing 10 arranged (see 2 ), ie in the area in which mixed friction events and / or slip stick events can occur frequently.

The movements B (eg as preforming) are from the sensor element 1 recorded and converted into electrical signals sent to a data processing device 20 to get redirected.

The data processing device 20 can be eg a built-in microprocessor or a single computer. In any case, the data processing system points 20 a means of calculation 21 on, with which the frequencies of the movements B , the amplitudes of the movements B and / or the temporal changes of the frequencies and / or the amplitudes can be determined (see 3 ). By means of a spectral analysis (eg with the aid of an FFT), the individual frequencies of the detected movements B and their evolution over time. An incipient mixed friction event and / or an incipient stick-slip-stick event have a special profile of the frequencies and amplitudes of the movements B (eg of structure-borne noise). The height of the frequencies depends, for example, on the materials used and the geometric dimensions of the component 10 from.

Usually, in modern plain bearings 10 a multilayer coating chosen. The different materials in the coating layers, for example, have an influence on the stick-slip events, ie based on the detected frequencies and / or amplitudes, the wear of the respective top layer can be detected. If, for example, the coatings are electrically nonconductive, a current can be detected by an applied voltage when the insulating coatings are "worn through".

The particular profile of the frequencies and / or amplitudes or else only the exceeding of a specific threshold value for a frequency and / or amplitude can be a predetermined condition, based on which a first signal S1 is generated via the presence of a mixed friction event and / or a stick-slip event.

The onset of a mixed friction event and / or the onset of a stick-slip event, i. the beginning, is understood here already by capturing the respective event. Capturing thus enables the prediction of harmful events by means of empirical experiences.

In 2 is an example of a rotationally movable component 10 a plain bearing shown in a side view. There is a bearing gap 13 between an outer ring 12 of the sliding bearing and the rotary member 14 of the component 10 in front. At the bottom of the rotary part 14 Here is a sensor element 1 arranged, ie in the load range of the sliding bearing 10 in which mixed friction events and / or stick-slip events are most likely to occur. In the illustrated embodiment, the sensor element is 1 on the front side of the plain bearing 10 arranged. The movements B are in 2 shown schematically, since vibrations, such as structure-borne noise, in a complex manner in the component 10 spread.

Alternatively, the sensor element 1 also on the outer ring 12 of the plain bearing 10 be arranged. It is also possible to use several sensor elements 1 to use.

Typically, a mounting position of the sensor element 1 chosen, which are opposite to the component 10 not moved. Indicates the plain bearing 10 For example, shells on, so the sensor element 1 eg also be arranged between or under the shells.

The sensor element 1 has a piezoelectric or piezoresistive element with which during operation of the component 10 occurring structure-borne noise in plain bearings 10 can be detected.

Before insertion, and even more after the onset of the mixed friction event and / or the stick-slip event, the structure-borne noise that is radiated into the sliding bearing 10 changes. This depends on the friction partners, in particular on the respective active as a friction partner layer of the different levels of the coating. This change is made by the sensor element 1 detected and to the data processing device 20 (please refer 1 ) slides on.

With the help of sensor elements 1 can be inferred from different frequencies, profiles and / or amplitudes on the onset of a mixed friction event and / or a stick-slip event. Then, depending on predetermined conditions, a first signal S1 that indicates the onset of a mixed friction event and / or stick-slip event. Thus, for example, the lubrication and / or the speed of the component 10 be influenced to suppress or minimize the incipient or present mixed friction event and / or stick-slip event.

It is possible these conditions for a particular component 10 empirically by experimenting with specific, then determined characteristic values then in the computer 21 save. So you would in a component 10 specifically generate mixed friction events and / or stick-slip events and the characteristic structure-borne sound events occurring thereby (eg characterized by amplitudes and / or frequencies of the movements B ) measure up. Thus, a map - also depending on other operating parameters such as the speed or the temperature - are generated, with which then the prediction of the remaining lifetime of a warehouse, is possible.

In 3 a flowchart for an embodiment of the measuring method is shown.

In the first step 301 are here in the operation of the component 10 Stick-slip events and / or mixed friction events by the sensor elements 1 based on the movements B (eg structure-borne noise) in the material of the component 10 measured and to the data processing device 20 transfer. The subsequent steps then take place in data processing device 20 using a calculator 21 for the evaluation of the frequencies of the movements B , the amplitude of the movements B , the changes in the frequencies and / or changes in the amplitudes.

In the second step 302, a known per se anti-aliasing filtering is performed. This is done using a low pass filter.

In the third step 303, the data is selected within a predetermined time-shifting window. The structure-borne sound signals are then obtained from the data in the window in the fourth step 304 by high-pass filtering

Subsequently, in the fifth step 305, the frequencies, profiles and amplitudes of the structure-borne sound are determined. Thus, e.g. serve an FFT analysis.

These determined values are then compared in a sixth step 306 with the previously empirically determined data for the onset of mixed friction events and / or stick-slip events. In the presence of a predetermined condition, in particular a threshold value, a first signal is automatically generated in a tenth step 310 S1 via the presence of a mixed friction event and / or a stick-slip event in the component 10 generated. In the tenth step 310, for example, the frequency of the mixed friction events and / or the stick-slip events can also be detected. Thus, it is possible to obtain statistical statements, on the basis of which by certain countermeasures (eg increase in oil pressure or change in speed) of the mixed friction and / or the stick-slip events can be counteracted.

By counting occurring mixed friction effect by slip-stick events until failure of the camp, a database is built. The knowledge of the number of possible mixed friction (slip-stick events) is used to determine the remaining life by counting down from the previously learned amount (occurring mixed friction ratios to failure).

The first signal S1 can be used to register individual events in a statistic, such as predicting the lifetime of the part 10 can be made (see below). The first signal S1 but can also be used to operating parameters of the component 10 to counteract mixed friction events and / or stick-slip events. This can be effected for example by targeted use of lubricants or temperature changes.

As a result, there are other options. In a seventh step 307, the determined data for the mixed friction events and / or the stick-slip events can be correlated with the structure-borne sound due to other periodic processes, such as at meshing frequencies in transmission applications. The presence of correlated tooth intervention makes it possible to check the function of the monitoring unit. Thus, in an eighth step 308, a self-diagnosis of the component 10 respectively.

Thus, as discussed above, in a ninth step 309, a mixed friction event associated with a coated journal bearing may occur 10 be recognized.

In an eleventh step 311, the data processing device 20 Material data of the component 10 , provided here of the sliding bearing. Together with the running on the slide bearing 10 determined data on mixed friction events and / or stick-slip events can then be made in a twelfth step 312 a forecast for the lifetime. Additionally or alternatively, also a second signal S2 indicate the existence of a claim.

It is possible to count mixed friction events and / or stick-slip events up to and including the failure of the warehouse at an exemplary warehouse and thus to build up an empirical database. For currently monitored warehouses, the achieved value (the possible number of mixed friction events or stick-slip events) counts down the "life" of the onset mixed friction slip sticke effects. The collection of exemplary data can also be done in warehouses in use on identical or similar machine.

LIST OF REFERENCE NUMBERS

1

sensor element

10

rotationally movable component

11

axis of rotation

12

Outer ring sliding bearing

13

bearing gap

14

turned part

20

Data processing device

21

computing means

301-312

steps

B

movements

S1

first signal

S2

second signal

Claims (18)

Measuring device for detecting mixed friction events and / or stick-slip events on and / or in a rotationally movable component (10), characterized by at least one sensor element (1) for detecting movements (B) in the material of the component (10), in particular Deformations and / or vibrations on and / or in the component (10), wherein the at least one sensor element (1) is coupled to a data processing device (20) and the data processing device (20) comprises a computing means (21) for evaluating the frequencies of the movements (B ), the amplitudes of the movements (B), the changes of the frequencies and / or the changes of the amplitudes, whereby in dependence of the evaluation of the frequencies of the movements (B), the amplitudes of the movements (B), the changes of the frequencies and / or the changes in the amplitudes and in the presence of a predetermined condition, in particular a threshold automatically a first signal (S1) over d the presence of a mixed friction event and / or a slip-stick event in the component (10) can be generated. Measuring device after Claim 1 , Characterized in that the at least one sensor element (1) as a piezoelectric sensor, a piezo-resistive sensor, acoustic emission sensor or a strain gauge formed. Measuring device after Claim 2 , characterized in that the piezoelectric sensor element (1) comprises a langasite crystal. Measuring device according to at least one of the preceding claims, characterized in that the movements (B), in particular deformations caused by structure-borne noise due to mixed friction events and / or stick-slip events in the component (10). Measuring device according to at least one of the preceding claims, characterized in that a filtering and / or spectral analysis of the signals can be carried out by the computing means (21), which on the basis of the detected movements (B), in particular by the detected structure-borne noise to the data processing device (20 ) were transferred. Measuring device according to at least one of the preceding claims, characterized in that the incoming data over a predetermined number of revolutions of the rotationally moving component (10) from the computing means (21) are evaluable. Measuring device according to at least one of the preceding claims, characterized in that at least two sensor elements (1) are arranged on or in the component (10), the first signal being dependent on differences in the movements (B) detected by the respective sensor elements (1) (S1) on the existence of a mixed friction event and / or a slip-stick event in the component (10) can be generated. Measuring device according to at least one of the preceding claims, characterized in that a predetermined profile of the frequencies and / or amplitudes and / or the exceeding of a specific threshold for a frequency and / or an amplitude is a predetermined condition, on the basis of which a first signal (S1) is generated via the presence of a mixed friction event and / or a stick-slip event. Measuring device according to at least one of the preceding claims, characterized in that in the computing means (21) a map is stored on the dependence of the onset of the mixed friction events and / or the stick-slip events. Measuring device after Claim 9 , characterized in that the characteristic field also detects the influence of operating parameters, in particular the rotational speed of the rotationally movable component (10) and / or the temperature. Measuring device according to at least one of the preceding claims, characterized in that the at least one sensor element (1) with a sliding bearing or a roller bearing as a component (10) is coupled. Measuring device after Claim 11 , characterized in that a signal can be generated if a current is detectable in a penetration of an electrically insulating coating by an applied voltage. Measuring device after Claim 11 or 12 , characterized in that sliding bearing or the rolling bearing is part of a transmission, in particular a planetary gear. Measuring device according to at least one of the preceding claims, characterized in that with the computing means (21) tooth engagement frequencies in correlation to the movements (B) are processable. Measuring device according to at least one of the preceding claims, characterized in that temperature data, in particular of oil, determined in or on the component (10) can be processed in correlation with the computing means (21). Measuring device according to at least one of the preceding claims, characterized in that taking into account the empirical evaluation of the frequency of the movements (B), the amplitudes of the movements (B), the changes in the frequencies and / or the changes in the amplitudes and in the presence of a predetermined condition , in particular a threshold value, a second signal (S2) can automatically be generated by the presence of a damage in the component (10). Measuring device according to at least one of the preceding claims, characterized by a coupling with at least one component (10) in or on a gas turbine, in particular an aircraft engine. Measuring method for detecting mixed friction on and / or in a rotationally movable component (10), characterized by a) detection of movements (B) in the material of the component (10), in particular deformations and / or vibrations on and / or in the component (10 ) by at least one sensor element (1), b) evaluation of the at least one sensor element (1) detected data and transmission to a data processing device (20) with a computing means (21) for evaluating the frequency of the movements (B), the amplitudes of the movements (B), the changes in the frequencies and / or the changes in the amplitudes, c) in the presence of a predetermined condition, in particular a threshold automatically a first signal (S1) on the presence of a mixed friction event and / or a stick-slip event in the component (10) is generated.

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