WO2018015022A1 - Hydraulic flight control actuator having a double seal device and defined leakage - Google Patents

Abstract

The invention relates to a hydraulic flight control actuator, comprising a piston-cylinder device, which has a piston and a cylinder, and comprising a double seal device, which has at least one primary seal (1) and at least one piston ring (2) as a secondary seal (2), wherein the primary seal (1) and the piston ring (2) are provided between the piston and the cylinder, characterized in that at least one throttle point (21) is provided in the region of the secondary seal (2) in order to introduce a defined leakage at the secondary seal (2).

Description

 Hydraulic flight control actuator with double seal device and defined

 leakage

The invention relates to a hydraulic Flugsteueraktuator with a piston-cylinder device with a piston and a cylinder and a double sealing device with at least one primary seal and at least one piston ring as a secondary seal, wherein the primary seal and the piston ring between the piston and the cylinder are provided.

When known from the prior art in particular hydraulic actuators of aircraft such as helicopters or aircraft overhaul corresponding actuator components such as the seals is performed after defined time intervals for safety reasons. In particular, the internal seals of hydraulic components are regularly replaced. This happens according to the prior art usually even if the seals are not worn out and their replacement would actually not be required because a secure check of generic sealing concepts or devices so far is not possible. As a result, according to the prior art, the potential of the corresponding piston seals disadvantageously not exhausted, which in the known construction and approach associated with unnecessary effort, especially during maintenance, which are taken too early and thus too often too often. Furthermore, by the known use of redundant seals on the piston according to the prior art, the failure of a seal can not be detected. This is acceptable in the prior art only because the seals are exchanged at sufficiently short intervals as mentioned above.

Against this background, it is an object of the invention to provide an improved hydraulic Flugsteueraktuator in which the targeted installation of a defined and at least short-term tolerable leakage of a secondary seal or secondary seal failure of a primary seal or primary seal is made visible without the reliability of the device to endanger. In particular, the object of the invention is to provide a flight control actuator which requires less intensive maintenance and which can be checked more easily for any leaks.

This object is achieved by a hydraulic Flugsteueraktuator with the features of claim 1 and by a method for testing a corresponding actuator according to claim 10. Advantageous embodiments of the invention are the subject of the dependent claims.

Accordingly, a hydraulic Flugsteueraktuator is provided comprising a piston-cylinder device with a piston and a cylinder and a double-sealing device with at least one primary seal and at least one piston ring as a secondary seal. The primary seal and the piston ring are in this case provided between the piston and the cylinder, wherein at least one throttle point in the region of the secondary seal is provided for introducing a defined leakage at the secondary seal. The throttle in the Area of the secondary seal can be designed in any way and serves to reduce the sealing effect of the secondary seal defines.

The restriction may be part of the secondary seal and / or be separate therefrom and adjacent to the secondary seal. The reduction of the sealing effect may be so low that, in a case where the primary seal fails, the flight control actuator may function solely by sealing through the secondary seal and with a defined defined leakage at the secondary seal. If a leakage at the flight control actuator is detected during maintenance or diagnostic work, which corresponds to the defined leakage, this is a sign of the wear of the primary seal.

As a result of such leakage, which does not endanger the operational safety, it is determined that the primary seal is now actually damaged and must be replaced. The primary seal is thus advantageously replaced only when there is damage or replacement is actually required.

In a preferred embodiment, it is conceivable that the throttle point comprises at least one groove provided on the end face on the secondary seal, and / or at least one groove provided on the outer diameter of the secondary seal, and / or a throttle provided on the piston. When the throttle body is designed as a groove, there is the advantage that it can be produced particularly easily in the context of the production of the corresponding seal or the piston ring without additional work steps. If the throttle point additionally or alternatively is designed as a throttle or recess provided on the piston, this can be, for example, a groove running on a piston outer surface, which groove is correspondingly incorporated in the piston structure. It is also conceivable to provide a passage on the piston with a corresponding throttling action. Advantageously, so can customary piston rings be used, which need not be specially provided with the exemplified grooves.

In a further preferred embodiment, it is conceivable that the throttle point comprises at least two end-side grooves on the secondary seal, which are arranged in particular offset by 180 ° in the circumferential direction of the secondary seal. Usually, the seal can be circular or hollow cylindrical, whereby a related circumferential direction is clearly specified.

Any concentricity errors between the piston and the cylinder in which a single throttle point is greatly varied in the relative movement between the piston and the cylinder can thus be minimized. This makes it possible to ensure that the defined leakage remains within the most precisely defined range possible. In the arrangement of the throttle bodies in mutually offset by 180 ° positions possible concentricity error of the piston can be compensated particularly well because 180 ° offset areas of the piston known to have opposite concentricity errors.

In a further preferred embodiment, it is conceivable that the grooves are provided on both sides or on one side of the secondary seal. Depending on the size of the respective Flugsteueraktuators or the pressure regimes occurring thereon can be defined by the corresponding arrangement of the grooves a different size leakage. Furthermore, it can be provided in a further preferred embodiment that the grooves are designed to generate turbulent flows. The person skilled in the art dimensioned the grooves in such a way that turbulent flows are generated in the respective pressure regimes of the flight control actuator at the throttle points or at the grooves. The throttle points or grooves can be sized accordingly large or small. When turbulent flows occur in the case of a flow at the throttle points, this has the advantage that the turbulent flows are more uniform compared to laminar flows with respect to different temperatures. This means that the defined leakage, regardless of the temperature of the Flugsteueraktuators or the hydraulic fluid is in a narrower range and thereby can be detected more accurately.

In a further preferred embodiment, it is conceivable that the piston ring is designed as a double piston ring and has a stepped overlap between the two sections of the double piston ring. Due to the corresponding overlap, the leakage at the double piston ring can be further reduced.

The invention also relates to a piston ring for a hydraulic Flugsteueraktuator according to one of claims 1 to 8, wherein the piston ring comprises at least one frontally provided thereon groove, and / or at least one provided on the outer diameter of the piston ring groove, in particular at least two end-side grooves on the piston ring are provided, which are arranged offset by 180 ° in the circumferential direction of the piston ring, wherein further in particular the two grooves together have a constant cross-section errors constant cross-section, further more particularly the grooves are provided on both sides or on one side of the on the piston ring, and wherein Furthermore, in particular, the grooves for generating turbulent flows are formed.

The invention is also directed to a method for testing the tightness of a hydraulic flight control actuator according to any one of claims 1 to 8, comprising at least one piston ring according to claim 9, wherein a differential pressure is applied to the piston; an occurring leakage is measured; the measured leakage is compared with a stored target leakage; and wherein an impermissible leakage is detected when the measured leakage is above the desired leakage.

Further details and advantages of the invention are explained with reference to the exemplary embodiments shown in the figures. Showing: Figure 1: diagram for explaining the inventive

 Flight control actuator occurring leaks;

Figure 2: Detail view of the provided on Flugsteueraktuator

 Piston ring as secondary seal;

Figures 3a and 3b: views of the secondary seal with throttling points; and

FIG. 4a: a sectional view of a partial region of a device according to the invention

 Flugsteueraktuators; and

FIG. 4b: top view of a piston ring according to the invention.

Figure 1 shows the leakage behavior of the device according to the invention in its time course (abscissa). In this case, the leakage quantity and the critical leakage are indicated on the ordinate, at the crossing of which a critical state of the flight control actuator or the corresponding seal occurs. The leakage is determined in corresponding measurement intervals, for example by pressure measurement at the appropriate Flugsteueraktuator. The measured leakage is indicated as measurable leakage in its time course. If leakage occurs at the primary seal 1, the measured leakage value rises to a level which is predetermined by the defined mean leakage of the secondary seal 2. Achieving this mean leakage plateau, which lies between the critical leakage amount (upper horizontal line) and the leak when the flight control actuator is functioning properly (left portion of the measurable leakage curve), means that the primary seal 1 is leaking and sealing the flight control actuator now takes place via the secondary seal 2 with its defined leakage. An exchange of the primary seal 1 and optionally the secondary seal 2 is therefore indicated. This results in three inventively conceivable leakage cases. The first case is shown in the left-hand portion of FIG. 1 and occurs when the primary seal 1 functions correctly and the secondary seal 2 is not or hardly stressed thereby and is therefore not activated. This corresponds to the level 0.

The second case is shown in the central region of FIG. 1 and is present when there is a fault or defect at the primary seal 1, in which case the secondary seal 2 is active and the leakage defined thereon occurs. This corresponds to level 1. If this level or leakage level is detected, this is an indication to carry out a maintenance action.

The third case is shown in the right-hand area of FIG. 1 and is present when both seals 1, 2 are defective. The corresponding Flugsteueraktuator is then no longer fully operational, which can lead to the loss of the corresponding hydraulic system.

A prerequisite for a correspondingly defined leakage is a piston ring 2 which permits virtually no or as little as possible leakage at the opening 24 of the ring 2 or at its slot 24 (see FIGS. 2 and 4b). This can be realized by a double ring 2 ', which is arranged so that the two slots 24 of the two double-ring parts 22, 23 are offset from each other. A double ring 2 'can in this case comprise two, in particular identical, circumferentially offset and axially spaced-apart piston rings 2. Also, the opening or the slot 24 may be designed so that changes in length, which may occur due, for example, due to tolerances or temperature changes, do not affect the tightness of the piston ring 2. This can be realized by a stepped overlap of the double ring 2 ', which prevents a flow of hydraulic fluid in the radial and / or axial direction even with changes in length.

As can be seen in FIGS. 3 a, 3 b and 4 b, grooves 11, 21 may be provided on the secondary seal 2 at the end or otherwise, which are characterized by their size determine the flow. To compensate for radial displacements of the secondary seal 2, two grooves 11, 21 can be provided per side and offset by 180 °, which together provide a constant cross section, which remains independent of any concentricity errors of the piston also constant or approximately constant. Otherwise, concentricity errors can otherwise lead to a groove 11, 21 which lies in a region in which the distance between the piston and cylinder is reduced due to the concentricity error, being deformed more strongly and thus for example has a smaller cross-section or a cross-section with a smaller cross-sectional area ,

By appropriate arrangement of a plurality of grooves 21 of the secondary seal 2 such cross-sectional deviations can be compensated. The grooves 21 can be mounted on both sides to allow a flow in both directions, or they can also be mounted only on one side to allow only one-way flow.

The grooves 21 can be designed so that turbulent flows occur during the flow of hydraulic fluid and thereby the flow over the entire temperature range of the hydraulic fluid remains as constant as possible. To carry out the leakage measurement and thus to assess the condition of the primary seal 1, a differential pressure can be applied to the piston or in the piston-cylinder device.

Instead of or in addition to the throttle bodies formed as grooves 21, which may be provided on all outer surfaces of the secondary seal 2, the throttle body 21 and thus the defined leakage can also be realized by a throttle in the piston itself or on the piston itself.

FIG. 3 b shows an enlarged view of a groove 11, which is provided on an end region of a secondary seal 2. Also conceivable are grooves 11, 21, which are arranged on the lateral surfaces of the optionally hollow cylindrical secondary seal 2. It can also be seen in FIG. 3b that a circumferential groove 12 running in the circumferential direction can be provided on the secondary seal 2. This can separate or partially separate the secondary seal 2 into two subregions, or alternatively can be present only within the structure of the integrally manufactured secondary seal 2.

Claims

claims A hydraulic Flugsteueraktuator comprising a piston-cylinder device with a piston and a cylinder and a double sealing device with at least one primary seal (1) and at least one piston ring (2) as a secondary seal (2), wherein the primary seal (1) and the piston ring ( 2) are provided between the piston and the cylinder, characterized in that for introducing a defined leakage at the secondary seal (2) at least one throttle point (21) in the region of the secondary seal (2) is provided. 2. Hydraulic Flugsteueraktuator according to claim 1, characterized in that the throttle point (21) at least one end face of the secondary seal (2) provided groove (21), and / or at least one on the outer diameter of the secondary seal (2) provided groove (21), and / or a throttle (21) provided on the piston. 3. Hydraulic Flugsteueraktuator according to claim 1 or 2, characterized in that the throttle point (21) at least two end-side grooves (21) on the secondary seal (2), in particular offset by 180 ° in the circumferential direction of the secondary seal (2) are arranged. 4. Hydraulic Flugsteueraktuator according to claim 3, characterized in that the two grooves (21) together have an independent of concentricity constant cross-section. 5. Hydraulic Flugsteueraktuator according to one of claims 2 to 4, characterized in that the grooves (21) are provided on both sides or on one side of the secondary seal (2). 6. Hydraulic Flugsteueraktuator according to one of claims 2 to 5, characterized in that the grooves (21) are designed for generating turbulent flows. 7. Hydraulic Flugsteueraktuator according to any one of the preceding claims, characterized in that the piston ring (2) is designed as a double-piston ring with two openings (24), wherein the openings (24) of the piston ring (2) are offset from each other. 8. A hydraulic Flugsteueraktuator according to claim 7, characterized in that the double piston ring (2) has a stepped overlap between the two sections (22, 23) of the double piston ring (2). 9. piston ring (2) for a hydraulic Flugsteueraktuator according to one of claims 1 to 8, characterized in that the piston ring (2) at least one end face provided thereon groove (21), and / or at least one on the outer diameter of the piston ring (2) provided Groove (21), wherein in particular at least two end grooves (21) on the piston ring (2) are provided, which are arranged offset by 180 ° in the circumferential direction of the piston ring (2), wherein more particularly the two grooves (21) together men have a constant cross-section of constant errors, further in particular the grooves (21) on both sides or on one side of the piston ring (2) are provided, and further wherein in particular the grooves (21) are designed for generating turbulent flows. 10. A method for testing a hydraulic Flugsteueraktuators according to any one of claims 1 to 8 with at least one piston ring (2) according to claim 9, characterized in that a differential pressure is applied to the piston; an occurring leakage is measured; the measured leakage is compared with a stored target leakage; and an impermissible leakage is detected when the measured leakage is above the target leakage.