DE102020105403A1 - Method for determining the degree of contamination of a filter element - Google Patents

Abstract

A method is proposed for determining the degree of contamination of a filter element in a component of a fluid power system, comprising the steps of measuring a differential pressure present in the component, measuring a temperature of a fluid flowing through the filter element, and determining a tolerable differential pressure using a value matrix , in which experimentally determined differential pressures and temperatures are correlated with at least one predetermined tolerable degree of filter contamination, comparing the measured differential pressure with the determined tolerable differential pressure, and issuing a maintenance notice if the measured differential pressure reaches or exceeds the tolerable differential pressure.

Description

TECHNICAL AREA

The invention relates to a method for determining the degree of contamination of a filter element in a component of a fluid power system, a fluid power system, and an aircraft with at least one such fluid power system.

BACKGROUND OF THE INVENTION

Fluid power systems, which include hydraulic and pneumatic systems, have a large number of interconnected, fluid-carrying components. In this case, filter elements are usually provided which filter the fluid flowing in the relevant system and in doing so take up contamination. These could arise, for example, from material abrasion in the system. Since a filter element has a limited capacity to absorb such contaminants, the fluid mechanical resistance over the filter element changes over time. A fluid power system can have a tolerable limit for contamination of the filter element in order to ensure proper operation. If a degree of pollution is reached or if it threatens to be exceeded, measures must be taken. This includes, for example, replacing the filter element or a component that houses the filter element.

In the case of complex designs of the fluid power system, for example in an aircraft in the form of one or more hydraulic systems, it is desirable to always be able to reliably check the degree of contamination of a filter element. For example, mechanical devices are known which move out of a hydraulic control block when a certain differential pressure is reached and which can be visually recognized when the system is visually inspected. Alternatives are known which, based on the measurement of the pressure drop across the hydraulic control block, generate a maintenance signal when a certain differential pressure is exceeded. It should be noted, however, that the pressure drop across the component housing the filter element does not necessarily correspond to the differential pressure across the filter element itself. For example, there are valves in the component that also influence the flow resistance and thus the pressure drop to a certain extent. A geometry of the component, for example a valve block, can also bring about an additional throttle effect or diaphragm effect.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to propose an alternative method for determining the degree of contamination of a filter element in a component of a fluid power system, which is particularly precise and causes as few false reports as possible.

The object is achieved by a method with the features of independent claim 1. Advantageous embodiments and developments can be found in the subclaims and the following description.

A method is proposed for determining the degree of contamination of a filter element in a component of a fluid power system, comprising the steps of measuring a differential pressure present in the component, measuring a temperature of a fluid flowing through the filter element, and determining a tolerable differential pressure using a value matrix , in which experimentally determined differential pressures and temperatures are correlated with one another at at least one predetermined tolerable degree of filter contamination, comparing the measured differential pressure with the determined tolerable differential pressure, and issuing a maintenance notice if the measured differential pressure reaches at least a threshold value dependent on the tolerable differential pressure .

The method according to the invention is therefore based on a completely different approach than known methods. The individual steps that make sense for this purpose as well as preparatory measures are explained in more detail below.

First, a differential pressure in the component is measured. This can be a pressure difference across the filter element or across the component having the filter element. This is referred to below as the filter differential pressure or component differential pressure. The component could for example be a control block and in particular a filter control block. The filter element could, if desired, be in fluid communication with an input and an output of the component via one or more check valves. The component differential pressure could largely correspond to the filter differential pressure in the case of low volume flows.

The filter differential pressure can be measured by a differential pressure sensor that is connected to filter connections directly upstream and directly downstream. The measurement of the component differential pressure could be via a Differential pressure sensor, which is connected to the input and the output of the component. The relevant differential pressure sensor can transmit a measured value to a control unit or another electronic component in a wireless or wired manner. The measurement of a differential pressure can alternatively also take place by subtracting the measured values of two pressure sensors, which each measure an absolute pressure.

Furthermore, the temperature of the fluid is determined at the same time or at a short time interval. This can be done with a temperature sensor which is provided directly upstream and / or directly downstream and / or within the filter element. Numerous different temperature sensors are known which require direct material contact with the fluid or which can work without contact. It is also conceivable, instead of directly measuring the temperature of the fluid, also to measure a surface temperature of the filter element, in particular a surface facing the fluid, and to infer the fluid temperature from this from characteristic curves or the like. The temperature sensor can also transmit a measured temperature wirelessly or by wire to the above-mentioned control unit or other electronic component.

Several differential pressures can be recorded in the value matrix, which could be recorded for example over several volume flows, temperatures and at least one tolerable degree of contamination of the filter element. The value matrix is multi-dimensional and can provide information about the relationship between differential pressure and degree of contamination under certain operating conditions. In particular, from the knowledge of the fluid temperature, a tolerable differential pressure can be determined as a maximum value from the value matrix. If possible, the value matrix could also map several operating cases of the fluid power system under consideration. For example, there could be defined operating cases in a hydraulic system of an aircraft, each of which can be assigned a known volume flow. The tolerable differential pressure could be different for several operating cases. The determination of the tolerable differential pressure could therefore be carried out not only on the basis of the measured temperature, but also on the basis of information about the respective operating case.

The filter element is defined for a certain tolerable degree of contamination. This is determined implicitly via a self-defined, tolerable maximum differential pressure, which in turn depends on an operating state in which the volume flow and temperature are known. For this purpose, a specific operating case, dimensioning the system, can be selected in which a high volume flow is expected. In a commercial aircraft, this could be, for example, during the retraction or extension movement of a landing gear or when extending or retracting slats or trailing edge flaps. Since the differential pressure resulting from the flow through a contaminated filter element depends, among other things, on the volume flow rate, the temperature and the contamination of the filter element, a maximum tolerable differential pressure can result, which corresponds to tolerable contamination of the filter element.

By measuring the temperature, for example, the mechanical power to be expended with the fluid system can be estimated. With higher mechanical power, the temperature of the fluid could rise. In addition, the fluidic properties of the fluid depend on the temperature, among other things, since the density and viscosity in particular change with the temperature and thus the flow resistance and the resulting pressure difference are also influenced. The measurement of the temperature can therefore be representative of the current operating state of the fluid mechanical system, among other things. The determination of the tolerable differential pressure is consequently supported by the temperature measurement and allows the existing contamination of the filter element to be checked more precisely.

Furthermore, reaching a threshold value can be used to issue the maintenance notice. The threshold value can correspond to a specific, predefined proportion of the respective tolerable differential pressure. The comparison of the measured differential pressure with the ascertained, tolerable differential pressure for an operating condition represented by the temperature is consequently more precise than in known methods in which only an absolute value of a differential pressure is taken into account. The generation of a maintenance notice is therefore improved and incorrect assessments can be prevented.

In an advantageous embodiment, the experimentally determined differential pressures and temperatures are correlated with one another in the case of a plurality of filter contamination levels, which also include the tolerable level of contamination. Accordingly, different degrees of pollution for a given operating state could also be determined from the value matrix.

In an advantageous embodiment, the method includes determining a degree of contamination of the filter element from the value matrix on the basis of the measured temperature and the measured differential pressure. With a measured Temperature and a measured differential pressure, a degree of contamination of the filter element can be deduced in order to obtain information about an upcoming maintenance in good time. It is particularly advantageous to do this in certain operating cases in which the volume flow through the fluid power system is essentially known, as already mentioned above.

The method preferably provides for the recording of the determined degrees of pollution and the issuing of a first maintenance instruction when a first degree of pollution is exceeded, the first degree of pollution corresponding to pollution that is less than the tolerable pollution.

The first level of pollution is roughly a threshold value. Several threshold values can also be defined so that several degrees of pollution are queried in stages, e.g. 1/4 of a permissible pollution, 1/2, 3/4, etc. In particular, this can be smoothed in order to remove any remaining uncertainties from the curve. In this way, the accuracy for a statement about the degree of contamination and the approximation of a maintenance instruction to be issued can be improved even further.

It is preferred if measuring the differential pressure comprises measuring a filter differential pressure. The filter differential pressure is measured directly above the filter, so that uncertainties regarding other fluid-mechanical components in the component comprising the filter element are excluded. If a differential pressure sensor or an arrangement of two absolute pressure sensors is already provided on the filter element in question, the method according to the invention in this embodiment is also suitable for subsequent implementation in a fluid power system with the help of a software update.

Nonetheless, measuring the differential pressure can also include measuring a component differential pressure. This is dimensioning for the fluid power system and implicitly also contains the filter differential pressure, to which differential pressures are added that result from other components that are arranged upstream or downstream of the filter element. This is useful if only one differential pressure sensor or an arrangement of two absolute pressure sensors is provided for the component in question and a modification of the filter element is to be avoided.

Accordingly, the tolerable differential pressure could also be a tolerable component differential pressure.

However, the variant of the tolerable component differential pressure could also be combined with the measurement of a filter differential pressure. If the filter differential pressure is present, an equivalent component differential pressure can be obtained from this, which is then compared with the tolerable component differential pressure. This could be done by means of suitable characteristic curves which, for example, indicate an axial offset between a filter differential pressure curve and a component differential pressure curve at different temperatures of the fluid, preferably in representative operating cases. However, it would also be possible to fill the value matrix with filter differential pressures which are correlated with tolerable component differential pressures also contained in the value matrix.

In a particularly preferred embodiment, the determined component differential pressure is compared with a value of a component differential pressure which is assigned to the measured filter temperature in the value matrix.

The invention further relates to a fluid power system for transmitting mechanical power, having at least one fluid actuator, a component with a filter element, at least one pressure sensor and at least one temperature sensor, and at least one control unit, the at least one pressure sensor being designed to measure a differential pressure in to measure the component, wherein the temperature sensor is designed to measure a temperature of a fluid flowing through the component, and wherein the at least one control unit is designed to calculate a tolerable differential pressure using a value matrix in which experimentally determined differential pressures and temperatures at at least are correlated with a predetermined tolerable filter contamination level, to determine, to compare the measured differential pressure with the determined tolerable differential pressure, and to issue a maintenance notice when the measured differential pressure exceeds t olerable differential pressure reached or exceeded. In this context, it should be understood that the term “fluid actuator” stands for a fluid consumer that is supplied with a pressurized fluid and thereby performs work.

The fluid power system can in particular be a hydraulic system which is arranged in a vehicle. In an advantageous embodiment, the vehicle is an aircraft. The aforementioned control unit can be arranged outside of the fluid power system. Furthermore, the control unit does not have to be implemented as an independent component, but could also be integrated in an on-board computer of the aircraft in the form of a suitable algorithm. The measured values provided by the at least one pressure sensor and the temperature sensor can be communicated to the relevant control unit via a data bus, a network connection or an independent signal line.

The at least one pressure sensor could preferably be arranged above the filter element and be designed to measure a filter differential pressure. Alternatively, the at least one pressure sensor could also be arranged above the component and measure the differential pressure across the entire component. In addition to the filter element, this could also have, for example, a check valve, a valve or the like. As shown above, the at least one pressure sensor could be designed as a differential pressure sensor. Alternatively, two pressure sensors could also be used, each measuring an absolute pressure. The differential pressure is determined by subtracting the absolute pressures.

In an advantageous embodiment, as mentioned above, the experimentally determined filter differential pressures and temperatures are correlated with one another in the case of several filter contamination levels, which also include the tolerable level of contamination. As mentioned above, the value matrix could also contain information on specific operating cases to which known or largely known values for volume flows can be assigned.

The control unit could then also be designed to determine a degree of contamination of the filter element from the value matrix on the basis of the measured temperature and the measured differential pressure. This is particularly preferred when a current operating case is known.

The control unit could also be designed to record the degrees of pollution determined and to output a first maintenance notice when a first degree of pollution is exceeded, the first degree of pollution corresponding to pollution that is less than the tolerable pollution.

Finally, the invention also relates to an aircraft having at least one system according to the preceding description. The aircraft could be a commercial aircraft which has at least one and preferably two or more such systems.

Figure list

• 1 zeigt eine blockbasierte Darstellung eines Verfahrens zum Ermitteln des Verschmutzungsgrades eines Filterelements in einer Komponente eines fluidtechnischen Systems.
• 2 zeigt eine blockbasierte Darstellung eines Teils eines Hydrauliksystems.
• 3 zeigt ein Flugzeug.

Further features, advantages and possible applications of the present invention emerge from the following description of the exemplary embodiments and the figures. All of the features described and / or shown in the figures, individually and in any combination, form the subject matter of the invention, regardless of their composition in the individual claims or their references. In the figures, the same reference symbols continue to be used for the same or similar objects.

• 1 shows a block-based illustration of a method for determining the degree of contamination of a filter element in a component of a fluid power system.
• 2 shows a block-based representation of part of a hydraulic system.
• 3 shows an airplane.

DETAILED REPRESENTATION OF EXEMPLARY EMBODIMENTS

1 shows a procedure 2 for determining the degree of contamination of a filter element in a component of a fluid power system in a schematic, block-based representation. Some of the steps shown are run through at the same time, in quick succession or after other steps have been carried out. First, a differential pressure across the filter element or the component having the filter element is measured 4. At the same time, shortly before or shortly after, a temperature of a fluid flowing through the filter element is measured 6. To assess whether the filter element has a degree of contamination that is no longer tolerable A tolerable differential pressure is determined from the measured values, in particular the measured temperature. This is done using a schematically indicated, in this case simplified, two-dimensionally drawn value matrix 10 , in which experimentally determined differential pressures and temperatures are correlated with one another at at least one predetermined tolerable degree of filter contamination and preferably one or more known operating cases with a known or largely known volume flow. The measured differential pressure is then compared with the determined tolerable differential pressure 12th . If the measured differential pressure exceeds the tolerable differential pressure, a maintenance notice is given 14th . The procedure 2 can after the block 12th or 14th start all over again.

Optionally, a degree of contamination of the filter element could be taken from the value matrix on the basis of the measured temperature and the measured Differential pressure can be determined 16 . This is exemplary as one aspect of the block 8th specified.

Furthermore, the determined degrees of soiling could optionally be recorded 18th and a first maintenance notice is issued when a first degree of pollution is exceeded 20th , the first degree of pollution level corresponding to pollution which is less than the tolerable pollution.

2 shows in a completely exemplary, schematic, block-based representation a fluid power system 22nd for transmitting mechanical power. Since the invention relates in particular to the determination of the degree of contamination of a filter element 24 are only a few components of the system 22nd shown. The system 22nd is shown by way of example as a hydraulic system and, by way of example, has a reservoir 26th on, which houses a hydraulic fluid. One pump 28 , which is an example with an engine 30th is operated, the hydraulic fluid is pressurized into a hydraulic line 32 leading to one or more actuators (not shown).

A control block 34 is provided as a component that the filter element 24 having. The control block 34 has an entrance 36 and an exit 38 on. The hydraulic fluid flows through the inlet 36 in the control block 34 inside, through the filter element 24 and about the exit 38 into the reservoir 26th . Dirt is filtered out of the hydraulic fluid. One look over the filter element 24 The resulting filter pressure difference depends on the degree of contamination of the filter element 24 addicted. This can be done using a filter differential pressure sensor, for example 40 above the filter element 24 be measured. Instead of the filter differential pressure sensor 40 An arrangement of two absolute pressure sensors could also be used, the measured values of which are subtracted in order to determine the differential pressure. Furthermore, a component differential pressure across the component 34 be measured. A component differential pressure sensor is used for this purpose 41 provided which one with the entrance 36 and the exit 38 connected is. Instead of the component differential pressure sensor 41 An arrangement of two absolute pressure sensors could also be used, the measured values of which are subtracted in order to determine the differential pressure. At the same time is a temperature sensor 42 provided that the temperature of the through the filter element 24 measuring the flowing hydraulic fluid. The determined measured values are sent to a control unit 44 fed which is part of the hydraulic system 22nd can be or could be arranged in an external processing unit.

The control unit 44 is designed to determine a tolerable filter or component differential pressure using a value matrix in which experimentally determined differential pressures and temperatures are correlated with one another for at least one predetermined tolerable filter contamination level. The control unit 44 has for this purpose a memory and a processor which are connected to a data interface. From the ascertained, tolerable differential pressure, it is possible to determine whether the tolerable differential pressure has been reached or exceeded by comparing it with the filter differential pressure and / or the component differential pressure.

For this purpose, preparatory measures are first necessary in order to create the value matrix. By way of example, these are provided in the form of preparatory process steps. Because the differential pressure across the component 34 for the system 22nd can be a dimensioning factor, measurements of the component differential pressure between the input are first 36 and the exit 38 performed and as a function of a volume flow between the input 36 and the exit 38 , a temperature of the hydraulic fluid and possibly a predetermined contamination of the filter element 24 recorded. This can be done under laboratory conditions in order to have precise knowledge of the fluidic properties of the entire component 34 to obtain. The measurements can be restricted to specific operating cases, which can each be assigned to a specific volume flow. A degree of contamination could be implicitly defined for the design of the filter element 24 dimensioning maximum value for a pressure difference across the filter element 24 result. If desired, measurements of the filter differential pressure can then be carried out in the same way. These are not necessarily identical to the measurements of the component differential pressure, since the component is a check valve, for example 46 may have, which also makes a contribution to the component pressure difference. From the measurements of the component pressure difference and, if desired, the measurements of the filter pressure difference, pressure difference curves are determined in the form of entries or components of the value matrix. From this, tolerable pressure differences can be determined, taking into account the simulated operating cases under which the measurements are carried out. These can include tolerable component pressure differentials and filter pressure differentials. The knowledge of a tolerable component pressure difference that is necessary for the system 22nd is specified, allows for example the reading or determination of an associated tolerable filter pressure difference. This can be in the filter element 24 measured and sent to the control unit 44 communicated.

In the control unit 44 an associated component pressure difference can be determined from a transmitted filter pressure difference and compared with the tolerable component pressure difference in order to issue a maintenance signal if this is exceeded. Furthermore, a measured component differential pressure can also be used for comparison with the tolerable component pressure differential.

If the preparatory measures explained above have been carried out for several different degrees of pollution, a statement about a current degree of pollution can also be determined from the filter pressure difference and / or the component pressure difference.

3 finally shows an airplane 48 , which with at least one such system 22nd can be equipped.

In addition, it should be noted that “having” does not exclude any other elements or steps, and “a” or “an” does not exclude a plurality. It should also be pointed out that features that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features of other exemplary embodiments described above. Reference signs in the claims are not to be regarded as a restriction.

List of reference symbols

2

procedure

4th

Measuring a differential pressure across the filter element

6th

Measuring a temperature of the fluid

8th

Determine tolerable differential pressure

10

Value matrix

12th

Compare with tolerable differential pressure

14th

Submit a maintenance notice

16

Determine the degree of soiling

18th

Record degrees of pollution

20th

Submission of an initial maintenance notice

22nd

Hydraulic system

24

Filter element

26th

reservoir

28

pump

30th

engine

32

Hydraulic line

34

Control block

36

entry

38

exit

40

Filter differential pressure sensor

41

Component differential pressure sensor

42

Temperature sensor

44

Control unit

46

check valve

48

plane

Claims (13)

Method (2) for determining the degree of contamination of a filter element (24) in a component (34) of a fluid power system, comprising the steps: - measuring (4) a differential pressure present in component (34), - measuring (6) a temperature of a fluid flowing through the filter element (24), - Determination (8) of a tolerable differential pressure using a value matrix (10) in which experimentally determined differential pressures and temperatures are correlated with one another at at least one predetermined tolerable degree of filter contamination, - Comparing (12) the measured differential pressure with the determined tolerable differential pressure, and - Issuing (14) a maintenance notice when the measured differential pressure reaches or exceeds the tolerable differential pressure. Procedure (2) according to Claim 1 In the value matrix (10) the experimentally determined filter differential pressures and temperatures are correlated with a plurality of filter pollution degrees, which also include the tolerable degree of pollution. Procedure (2) according to Claim 2 , further comprising determining (16) a degree of contamination of the filter element (24) from the value matrix (10) on the basis of the measured temperature and the measured differential pressure. Procedure (2) according to Claim 3 , further comprising recording (18) determined degrees of pollution and issuing (20) a first maintenance instruction when a first degree of pollution is exceeded, the first degree of pollution corresponding to pollution that is less than the tolerable pollution. Method (2) according to one of the preceding claims, wherein measuring (4) the differential pressure comprises measuring a filter differential pressure. The method (2) according to any one of the preceding claims, wherein measuring (4) the differential pressure comprises measuring a component differential pressure. Method (2) according to one of the preceding claims, wherein the tolerable differential pressure is a tolerable component differential pressure. Fluid power system (22) for transmitting mechanical power, comprising: at least one fluid actuator, a component (34) with a filter element (24), at least one pressure sensor (40, 41) and at least one temperature sensor (42), and at least one control unit (44), wherein the at least one pressure sensor (40, 41) is designed to measure a differential pressure in the component (34), wherein the temperature sensor (42) is designed to measure a temperature of a fluid flowing through the component (34), and wherein the at least one control unit (44) is designed to determine a tolerable differential pressure using a value matrix (10) in which experimentally determined differential pressures and temperatures are correlated with at least one predetermined tolerable filter contamination level, the measured differential pressure with the to compare the tolerable differential pressure determined and to issue a maintenance notice if the measured differential pressure reaches or exceeds the tolerable differential pressure. System (22) according to Claim 8 , wherein the at least one pressure sensor (40, 41) is arranged above the filter element (24) and is designed to measure a filter differential pressure. System (22) according to Claim 8 or 9 In the value matrix (10) the experimentally determined filter differential pressures and temperatures are correlated with a plurality of filter pollution degrees, which also include the tolerable degree of pollution. System (22) according to Claim 10 , wherein the control unit (44) is further designed to determine a degree of contamination of the filter element (24) from the value matrix (10) on the basis of the measured temperature and the measured differential pressure. System (22) according to Claim 11 , wherein the control unit (44) is further designed to record determined degrees of pollution and to output a first maintenance notice when a first degree of pollution is exceeded, the first degree of pollution corresponds to pollution that is less than the tolerable pollution. Airplane (48), having at least one system (22) according to one of the Claims 8 until 12th .

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