FR2862887A1 - Bi-directional filter for hydraulic control system, has channel producing helical movement to generate centrifugal force on particles, to project them on sleeve, where leakage current is produced between channel turns to move particles - Google Patents

Abstract

The filter has a body with a lateral wall and two end walls delimiting a chamber (11). The chamber has a mandrel delimiting a helical channel (15) circulating fluid, at its periphery. Helical movement produced by the channel generates a centrifugal force on particles transported by the fluid, to project the particles on a sleeve. A leakage current is produced between turns of channel to move the particles beyond channel zone. The filter is connected to a hydraulic system by threaded orifices (12, 13). An independent claim is also included for a hydraulic system comprising a filter.

Description

The present invention relates to the field of filtration and more

  particularly that of bidirectional filters for hydraulic control system, especially for aeronautics.

  Currently, most hydraulic actuator control systems such as cylinders are of centralized type. These systems comprise in a central part a pump now under pressure a network go. Through a set of mode valves, this pressurized network feeds an actuator. The system also comprises a return network to the tank at low pressure.

  In the context of aeronautics, this network is doubled or even tripled so that a failure of the hydraulic system can not disrupt the piloting of the aircraft.

  To protect these hydraulic systems against pollution of the fluid, barriers or mechanical filters are arranged on the network, the size of the mesh defining the minimum threshold of the particle size of the arrested particles.

  These filters are essentially unidirectional, so as not to reintroduce into the circuit particles stopped in one direction and which would be by pressure difference pushed back into the circuit in the opposite direction of the flows.

  Furthermore, to prevent a blockage unacceptable circuit, these filters generally include a clogging indicator and, where appropriate, a bypass device to divert all or part of the fluid out of the filtration zone.

  For effective protection of the circuit, a high pressure filter is generally placed at the pump outlet and, where appropriate, at the inlet of each receiver, an additional barrier with a looser mesh in order to protect the adjacent receiver with respect to accidental pollution.

  These centralized systems however have the major disadvantage of being heavy because they require long lengths of piping.

  The aerospace industry, which has strong weight constraints in its devices, therefore begins to use new concepts of hydraulic systems. These so-called decentralized hydraulic systems are such that the power hydraulic is generated closer to the actuator instead of being connected to a centralized pressure source.

  In addition to the switching components, they basically comprise an electropump connected directly to a cylinder. Thus, according to the direction of rotation of the electric pump, the discharge branch of the pump feeds a chamber of the cylinder which determines a direction of movement. The other cylinder chamber feeds the pump on the suction branch.

  Inversion of the rotation of the electric pump generates the reverse movement of the cylinder.

  Thus, this concept generates in the hydraulic circuit a bidirectional circulation of the fluid.

  Moreover, the operation is not at constant pressure, the latter depending on the forces experienced by the cylinder during its movement. Indeed, the movement of the rudder actuated by the cylinder is the object of various resistances.

  The protection vis-à-vis pollution self-generated by these bodies operating in closed circuit is necessary. However, the traditional filtration devices, such as those described above, can not be installed in such a system, because of the bidirectional circulation and the alternation of pressure and frequency.

  In addition, the conventional bidirectional filters comprise a double circuit with non-return valves making it possible to specialize a circuit by direction of the fluid. Such filters have the disadvantage of being heavy, bulky and complex in construction causing unacceptable reliability problems, particularly in circuits intended for aeronautics.

  The object of the present invention is to provide a bi-directional, mechanically simple filter which can not be clogged so as to obtain improved reliability.

  More specifically, the invention relates to a bidirectional filter for a hydraulic circuit, characterized in that it comprises a body having a side wall and two end walls defining a chamber, this body being provided in the vicinity of each of its two ends of connection means to the hydraulic circuit; static means for guiding and rotating the fluid, arranged in said chamber, and means for retaining the particles contained in the fluid, arranged around the static means for guiding and rotating the fluid, the latter means being adapted to circulate the fluid from one end to the other of the filter, along the retention means and to generate a centrifugal force which causes a propulsion of said particles towards the retention means.

  According to other features of the invention - the static means for guiding and rotating the fluid comprise at least one mandrel fixed in the body and defining at its periphery at least one open channel of helical shape, said channel communicating with its two ends with the connecting means, - the mandrel further comprises retention grooves on its periphery, - the mandrel comprises at each end a recess communicating, on the one hand with the channel and on the other hand with the connection means the end walls comprise threaded ends extending in the direction of the mandrel and adapted to cooperate with threads located at each end of said mandrel, gaskets are arranged between the side wall and each wall of the wall; ends, the retention means comprise a trapping sleeve, the trapping sleeve is constituted by a metal mesh, the means of In addition, the magnetic field generator is arranged between the metal mesh sleeve and the body side wall. The magnetic field generator comprises at least one electrical coil, the magnetic field generator comprises at least one magnetic field generator. less a permanent magnet, the retention means are connected to means for measuring the electrical characteristics thereof, these characteristics being representative of the clogging of said retention means, the measuring means are able to determine the impedance variations of the trapping sleeve.

  The invention also relates to a hydraulic circuit comprising a pump connected to a jack via a network of pipes in which a fluid circulates, at least one filter according to the invention being interposed in said network, so as to that the fluid passes through the filter while circulating in the network.

  The invention will be better understood on reading the description which follows and with reference to the accompanying drawings and in which - Figure 1 shows the diagram of a decentralized control hydraulic circuit; FIG. 2 is an end view of a device according to the invention; - Figure 3 is a sectional view along the line 3-3 of Figure 2; Figure 4 is a side elevational view of the mandrel; and Figures 5 and 6 show two further embodiments of the mandrel.

  A decentralized control hydraulic circuit, as shown in Figure 1, comprises a pump 1 feeding a cylinder 2 through a set of valves 3, said mode valve, allowing different modes of operation.

  In such a hydraulic circuit, several elements are likely, due to their displacements and / or their aging, to generate particles in the fluid. Thus, the pump 1 generates magnetic metal particles and particles of insulation or varnish by wear of its blades and its bearings. Similarly, the cylinder 2 generates elastomer particles by wear of its joints.

  For proper operation over time, it is important to filter the fluid to remove these suspended particles.

  Thus, a filter according to the invention can be installed on such a circuit, at the outlet of the pump 1, at 4, or in the vicinity of the cylinder 2, at 6, or at 5 to protect the valve mode 3.

  The filter according to the invention, fig. 2 and 3, comprises a sealed body 7 formed of a cylindrical side wall 8 and two end walls 9 and 10 delimiting a chamber 11. Two threaded holes 12 and 13 make it possible to connect the filter to the hydraulic circuit.

  This chamber contains a mandrel 14 (FIGS 3 and 4) delimiting at its periphery a helical channel 15 for circulating the fluid. This channel 15 opens at its ends into two recesses 17 and 18 of the mandrel, which communicate with the orifices 12, 13.

  The inner wall of mandrel 14 is threaded in the vicinity of the end faces thereof, to cooperate with externally threaded tips 19 and 20 which extend from the end walls 9 and 10. Sealing 21 are arranged between the side wall 8 and each end wall 9 and 10.

  The mandrel is surrounded by a trapping sleeve 22, made of a preferably multilayer metal mesh and an electric coil 23 disposed between this trapping sleeve 22 and the outer casing 8. The coil is connected to a circuit of FIG. power supply via conductors which pass through the end wall 10 in a sealed manner.

  In one embodiment of the invention corresponding to an application, for example in the aeronautical field, the filter being intended to hold for example particles mainly comprised between 5 and 15 m, the trapping sleeve 22 is made, for example, in the form of a magnetizable steel fabric whose square meshes have an opening of 600 m by 300 m.

  The operation of such a filter is as follows.

  The fluid arrives at the first orifice 12 and flows towards the second orifice 13, or vice versa, according to the direction of circulation of the fluid in the hydraulic circuit. It passes successively into the recess 17, then into the helical channel 15, before joining the second orifice 13 via the second recess 18.

  The helical movement produced by the channel 15 generates a centrifugal force on the particles carried by the fluid, force which projects them on the trapping sleeve 22.

  In addition, since the trapping sleeve 22 is not completely sealed between two turns of the helical channel, a leakage current is created between the turns and moves the particles out of the channel zone, thus preventing them from returning to the channel. the hydraulic circuit.

  The filter according to the invention thus allows a circulation of the fluid without mechanical barrier, and therefore without risk of clogging, the particles being retained by the retention means 22 when the fluid flows in the helical channel 15.

  Such a result is obtained in a first mode of operation, without the electric coil being energized and generating a magnetic field.

  This result can be improved, in a second mode of operation, by the creation of a magnetic field whose function is to attract the metal particles on the trapping sleeve 22.

  To do this, an electrostatic field is created by the coil 23 when it is powered. By passing through the multilayer metal fabric 22, this field is transformed in the zone of the channel 15 of the mandrel 14 into an electromagnetic and static mesh field capable of retaining polluting particles of different particle sizes and natures.

  In a variant, FIG. 5, of the embodiment described above, the mandrel 14 has two channels 15 and 15 'helical. The number and pitch of these channels can thus be adapted to the flow rate of the fluid and the size of the particles to be trapped.

  The impurities retained in the metallic fabric 22 migrating out of the channel zone by the effect of leakage current, it is possible to provide (FIG 6) retention grooves 24 machined in the mandrel and which allow to increase the life of the filter.

  It is of course possible to adapt the materials, shape, mesh size and method of obtaining the trapping sleeve 22 depending on the type of retention to obtain. It is thus possible to use a perforated plate or a single-layer metal fabric. Similarly, the trapping sleeve may be of non-magnetic material if the filter is used only in its first mode of operation.

  Compared to the preferred embodiment of the invention described above, it is conceivable that, if the filter is intended to be used continuously without power supply of the coil, as in the first mode of operation, it becomes unnecessary. An alternative embodiment of the filter then consists in suppressing it.

  The magnetic field of the coil can be enhanced by the presence of permanent magnets. It is also possible to replace the coil with permanent magnets. This makes it possible to maintain a magnetic field inside the circulation channel without needing to provide a power supply.

  The variations of the electrical characteristics of the retention means can be measured in 25 to detect the clogging of these retention means, and in particular of the metallic mesh and thus to deduce the need for a maintenance operation.

  Indeed, each grid mesh sees its gap evolve depending on the amount of particles retained. The trapping sleeve 22 therefore has its impedance which changes as a function of its clogging.

  Conventionally, the use of a voltmeter and an ammeter combined with a power supply of the trapping sleeve 22 in direct current, then in alternating current, makes it possible to determine the resistance and the inductance of the sleeve.

  As an illustration, the Applicant has found that the resistance of a sleeve can vary by about 10 mil and its inductance of 20pH between a new state and a clogged state.

  In the embodiment shown, the threaded orifices 12 and 13 are positioned on the end walls 9 and 10. However, the filter of the invention can also be made with the two connections to the hydraulic network positioned on the side wall 8 Only the communication with the channel 15 then require a modification, made in a conventional manner, without the principle of the invention being altered.

  It can be seen that such a bidirectional filter is mechanically simple and that, being unable to clog, it is highly reliable.

Claims (15)

  1. bidirectional filter for hydraulic circuit, characterized in that it comprises a body (7) having a side wall (8) and two end walls (9) and (10) delimiting a chamber, this body being provided with near each of its two ends of connection means (12, 13) to the hydraulic circuit; static means (14, 15) for guiding and rotating the fluid, arranged in said chamber, and retention means (22, 23) for the particles contained in the fluid, arranged around the static means (14, 15) for guiding and rotating the fluid, the latter means being adapted to circulate the fluid from one end to the other of the filter, along the retention means (22, 23) and to generate a centrifugal force which causes propelling said particles towards the retention means (22, 23).   Bidirectional filter according to Claim 1, characterized in that the static means (14, 15) for guiding and rotating the fluid comprise at least one mandrel (14) fixed in the body (7) and delimiting at its periphery. at least one open channel (15) of helical shape, said channel (15) communicating at its two ends (17, 18) with said connecting means.   3. bidirectional filter according to claim 2, characterized in that the mandrel (14) further comprises retention grooves (24) on its periphery.   4. bidirectional filter according to claim 2 or 3, characterized in that the mandrel (14) comprises at each end a recess (17, 18) communicating, on the one hand with the channel (15) and on the other hand with the connecting means (12, 13).   5. bidirectional filter according to one of claims 2 to 4, characterized in that the end walls (9, 10) comprise threaded ends (19, 20) extending towards the mandrel (14) and adapted to cooperate with threads located at each end of said mandrel (14).   Bidirectional filter according to one of the preceding claims, characterized in that sealing gaskets are arranged between the side wall (8) and each end wall (9, 10).   Bidirectional filter according to one of the preceding claims, characterized in that the retention means (22, 23) comprise a trapping sleeve (22).   8. bidirectional filter according to claim 7, characterized in that the trapping sleeve (22) consists of a metal mesh.   9. Bidirectional filter according to one of the preceding claims, characterized in that the retention means further comprises a magnetic field generator (23).   Bi-directional filter according to claim 9, characterized in that the magnetic field generator (23) is arranged between the metal mesh sleeve (22) and the body side wall (8).   Bidirectional filter according to Claim 9 or 10, characterized in that the magnetic field generator comprises at least one electric coil (23).   Bidirectional filter according to claim 9, 10 or 11, characterized in that the magnetic field generator further comprises at least one permanent magnet.   13. Bidirectional filter according to one of the preceding claims, characterized in that the retention means (22, 23) are connected to measuring means (25) of the electrical characteristics thereof, these characteristics being representative of the clogging of said means of retention.   Bidirectional filter according to one of Claims 7 to 12 and Claim 13, characterized in that the measuring means (25) are able to determine the impedance variations of the trapping sleeve (22). 15. A hydraulic circuit comprising a pump (1) connected to a jack (2) via a network of pipes in which a fluid circulates, characterized in that it comprises at least one filter (4, 5, 6). according to one of the preceding claims inserted in said network, so that the fluid passes through the filter circulating in the network.