FR2891361A1 - Variable reluctance device for e.g. aircraft`s turbo-machine, has detection module and excitation element associated with wheel to form closed magnetic circuit with air gap, where module has detection element with cells receiving coils - Google Patents

Abstract

The device (5) has a detection module (7) with a magnetic shielding sheath arranged between a protector tube and a polar detection element. The element protected by the tube has isolated cells for receiving pick-up coils forming a set of detection elements (13). The module and a magnetic excitation element (9) are associated with a ferromagnetic toothed wheel (11) for forming a closed magnetic circuit with an air gap varying according to a running frequency of tooth of the wheel. Each detection element delivers an electrical signal representative of a rotation speed of a rotary element (6).

Description

2891361 1

  TECHNICAL FIELD OF THE INVENTION The invention relates to a device with variable reluctance for measuring the speed of rotation of a rotating member, and in particular for measuring the rotation speed of an aircraft engine.

  BACKGROUND OF THE INVENTION A variable reluctance speed sensor is a generator whose magnetic circuit includes a toothed wheel of ferromagnetic material coupled to a rotating member whose rotation speed is to be measured. A sensor of this type is known for example from French patent FR2366572.

  Figure 9 schematically illustrates a variable reluctance device 105 having three probes 106 variable reluctance. Indeed, to control the proper operation of a rotary machine 101 requiring a high operational safety, in particular an aircraft engine, it is essential to have at least two probes 106 variable reluctance to provide independent signals to control means 103.

  Each probe 106 with variable reluctance comprises a coil 113 surrounded around a pole piece 125 fixed to a permanent magnet 109. The pole piece 125 is mounted facing a toothed wheel 111 of magnetic material with a determined air gap. When the toothed wheel 111 rotates, the coil 113 which is subjected to the flux of the permanent magnet 109, is excited by the variations in flux in the polar mass generated by the passage of the teeth of the wheel 111, thus delivering to means of 2891361 2 control 103 an alternating electric current whose frequency is proportional to the speed of rotation of this wheel 111.

  However, an assembly of three or four probes variable reluctance has a significant diameter especially for mounting in a cumbersome and difficult local environment such as an aircraft engine. In addition, it is not easy to increase the number of probes in the same housing to provide more independent signals to the control means.

  OBJECT AND SUMMARY OF THE INVENTION The object of the invention is to overcome these drawbacks by means of a variable reluctance device for measuring the speed of rotation of a rotating member coupled to a toothed wheel made of ferromagnetic material, the device comprising at least a detection module comprising a plurality of detection elements and a magnetic excitation element disposed in the vicinity of said detection module, the detection module and the magnetic excitation element being associated with the toothed wheel so as to form a closed magnetic circuit with variable gap according to the running frequency of the teeth of the toothed wheel, each detection element of said detection module thus delivering an electrical signal representative of the speed of rotation of the rotating member.

  Thus, this device for associating a plurality of speed detection elements with a single magnetic excitation element ensures a better compactness of the assembly.

  According to an exemplary embodiment of the invention, the device comprises a housing comprising at least first and second housings and in that the magnetic excitation element is fixed integrally in said first housing, an end of said magnetic excitation element. being positioned opposite the periphery of the toothed wheel 289 with a first predetermined air gap and in that the detection module is housed removably in said second housing, one end of said detection module being positioned facing the periphery of the wheel toothed with a second determined air gap.

  Thus, the detection module can be disassembled to allow its repair in case of failure.

  Advantageously, said at least first and second housings are formed in a screen of conductive material.

  Thus, by interposing between the magnetic excitation element and the detection module, the conductive material screen makes it possible to reduce magnetic leakage fluxes.

  According to a feature of the invention, the detection module comprises a non-magnetic protective tube protecting a polar detection element made of ferromagnetic material, said polar detection element comprising a plurality of isolated cells intended to receive a plurality of coils forming said plurality of elements. detection.

  Thus, the detection module comprises a compact, secure and removable a plurality of speed detectors.

  The detection module may also comprise a magnetic shielding sleeve disposed between the non-magnetic protective tube and the polar detection element.

  Thus, the magnetic sleeve reduces the electromagnetic coupling between the different elements.

  Advantageously, the magnetic excitation element comprises a polar excitation element and a transverse yoke of ferromagnetic material, fixed at both ends of a permanent magnet. Thus, the magnetic excitation element has a great robustness guaranteeing a very long life.

  Advantageously, the device comprises positioning means intended to support the detection module against the transverse yoke 20 of the magnetic excitation element and to guarantee the positioning of one end of the polar detection element opposite. around the toothed wheel according to the second determined air gap.

  Thus, by this precise and stable positioning the device has a high measurement reliability.

  For a simple and good feasibility of the device, the first and second predetermined gaps are equal.

  According to another embodiment, the device comprises a magnetic circuit closure element, one end of which is positioned facing the toothed wheel so as to form an additional closed magnetic circuit between this element and the magnetic excitation element in function. the running frequency of the teeth of the toothed wheel, said additional closed magnetic circuit being out of phase with that formed between the detection module and the magnetic excitation element. Thus, the sensitivity of the device is greatly increased.

  This magnetic circuit closure element may be an additional detection module. Thus, the number of speed detectors is increased.

  According to a variant, said magnetic circuit closure element is a polar element made of ferromagnetic material. Thus, magnetic leakage fluxes are minimized.

  Advantageously, the device comprises a connecting tube for guiding electrical connection cables of the plurality of detection elements to control means of the rotating member. Thus, the electrical connection cables are well protected.

  The device can be attached to a motor housing. Thus, this assembly can be performed in a simple and secure manner.

  The invention also relates to a system for controlling the operation of an engine, in particular an aircraft engine, comprising a variable reluctance device according to the above characteristics.

Brief description of the drawings

  Other features and advantages of the invention will become apparent on reading the description given below, by way of indication but not limitation, with reference to the accompanying drawings, in which: - Figure 1 is a schematic view illustrating a system; operating control system of an engine, according to the invention; FIG. 2 is a view illustrating a first embodiment of a device with variable reluctance, according to the invention; FIG. 3 is a view illustrating the casing of the variable reluctance device according to FIG. 2; FIG. 4 is a view illustrating a magnetic excitation element of the variable reluctance device of FIG. 2; FIG. 5A is a view illustrating a longitudinal section of a detection module of the variable reluctance device according to FIG. 2; FIG. 5B is an exploded view illustrating the detection module according to FIG. 5a; FIG. 6 is a view illustrating the mounting of the variable reluctance device according to FIG. 2 on the housing of an engine; FIGS. 7A to 8B are views illustrating other embodiments of the variable reluctance device according to the invention; and FIG. 9 is a schematic view illustrating a variable reluctance sensor according to the prior art.

  Detailed description of embodiments

  FIG. 1 illustrates a schematic example of a system for controlling the operation of a rotary machine or a motor 1, for example an aircraft turbomachine, according to the invention. This system comprises motor rotation speed control means 3 and a multi-directional variable reluctance device 5 for measuring the speed of rotation of a rotating member 6 of the engine 1.

  The variable reluctance device 5 comprises at least one detection module 7 (only one in the illustrated example) and a magnetic excitation element 9. In addition, the device 5 comprises a phonic wheel 11, that is to say say a coding wheel or toothed magnetic material coupled to or constituted by the rotating member 6 of the engine. Indeed, the sound wheel 11 may itself be constituted by the rotating member, for example a motor gear. Furthermore, the rotating member 6 may be the shaft of the motor 1 and in this case, the toothed wheel 11 is integral in rotation with the shaft whose rotational speed is to be measured.

  The detection module 7 comprises a plurality of independent detection elements 13 delivering a plurality of channels. Thus, the detection module 7 may comprise for example three or four detection elements 13 formed by insulated coils surrounded around a pole piece of ferromagnetic material with high magnetic permeability. It will be noted that according to the desired number of channels, a part of these detection elements 13 can be coupled together.

  The magnetic excitation element 9 comprises a permanent magnet and is disposed near the detection module 7. The assembly constituted by the detection module 7 and the magnetic excitation element 9 is associated with the toothed wheel 11 of the in order to form a closed magnetic circuit with a variable air gap as a function of the running frequency of the teeth of the toothed wheel 11. Naturally, this assembly is mounted opposite the periphery of the toothed wheel 11, on a fixed support with respect to the In addition, it can be positioned substantially perpendicular to the toothed wheel 11 (as illustrated) or substantially in the plane of this toothed wheel 11.

  The magnetic flux emanates from the magnetic excitation element 9 closes by the toothing of the toothed wheel 11 and the movement of the teeth causes a variation of the magnetic flux. Thus, when the toothed wheel 11 is rotating, the variations in the magnetic flux corresponding to the passage of the teeth develop at the terminals of each detection element 13 an electromotive force proportional to the variation of the magnetic flux and therefore to the speed of rotation of the wheel toothed 11.

  Then, each detection element 13 collects an electrical signal representative of the speed of rotation of the rotating member 6. The signals collected by the detection elements 13 are conveyed by respective electrical connection cables 10 to the control means 3 which include circuits for processing and exploiting these signals. In particular, the electrical signal collected by a detection element 13 is a substantially sinusoidal signal whose frequency is proportional to the rotational speed of the rotating member 6.

  By way of example, the variable reluctance device 5 measuring the rotational speed of a gas turbine engine low-pressure turbine shaft may comprise three measurement channels intended for a full authority control circuit (FADEC ) of the engine and an additional channel for providing cockpit speed information. Then according to this example, the variable reluctance device 5 can provide four independent ways of measuring rotational speed of the rotating member 6 with only two separate elements. The first element consists of a detection module 7 comprising four detection elements 13 and the second element consists of the magnetic excitation element 9. While providing four channels, this device has a diameter 2891361 8 reluctance reduced compared to an assembly of four speed sensors according to the prior art.

  Figures 2 to 6 illustrate a first embodiment of a variable reluctance device 5.

  Indeed, Figure 2 shows a variable reluctance device 5 comprising a support housing 15 serving as a receptacle for a screen 21 comprising two housings 17a and 17b (see also Figure 3). The magnetic excitation element 9 is fixed integrally, for example, by welding in a first housing 17a while the detection module 7 is housed removably in a second housing 17b. A free end 9a of the magnetic excitation element 9 is positioned facing the periphery of the toothed wheel 11 with a predetermined first air gap 19a. Similarly, a free end 7a of the detection module 7 is positioned facing the periphery of the toothed wheel 11 with a second gap 19b determined. Advantageously and for a better feasibility, the first and second determined gaps 19a and 19b are equal.

  It will be noted that the electromotive force created in each detection element 13 depends on the value of the first and second air gaps 19a and 19b, and decreases rapidly with the increase of this value, which can not generally exceed a few millimeters.

  Figure 3 shows that the first and second housing 17a and 17b of the housing can be formed in a screen 21 of conductive material having longitudinal slots to inhibit eddy current losses. For example, the housing 15 is a hard nonmagnetic steel support (of the Z6NCT25 type or similar) and the screen 21 is made of aluminum which makes it possible to reduce the magnetic leakage fluxes. The housing 15 has two positioning holes 23a and 23b coaxial with the two housings 17a and 17b so as to allow the free ends 9a and 7b of the magnetic excitation element 9 and the detection module 7 to be well positioned in position. view of the toothed wheel 11.

  FIG. 4 is a view illustrating the magnetic excitation element 9. This magnetic excitation element 9 comprises a polar excitation element 25 made of a soft ferromagnetic material (for example an alloy based on 50% nickel), a permanent magnet 27 (for example a cylindrical magnet of the Alnico type) and a transverse yoke 29 made of a soft ferromagnetic material (for example an alloy based on 50% nickel). The polar excitation element 25 and the transverse yoke 29 are fixed for example by welding at the two ends of the permanent magnet 27. In particular, the transverse yoke 29 can be fixed to the permanent magnet 27 via a polar link element 28. Furthermore, the polar excitation element 25 constitutes the free end 9a facing the toothed wheel 11. Advantageously, the magnetic excitation element 9 also comprises a protective tube 31 (FIG. for example stainless-8X9) protecting the permanent magnet 27.

  The magnetic excitation element 9 is integrated for example by welding in the housing 15 which is mounted on a fixed support for example the inner intermediate casing 33 to the motor (see also Figure 6).

  In fact, according to this example, holes 34 formed in the transverse yoke 29 make it possible to fix with fastening means 38 (for example bolts), the casing 15 on the inner casing 33. Moreover, the casing 15, the 21, and the transverse yoke 29 may have respective holes 35a, 35b and 35c for fixing the assembly with a fixing means 36. Thus, the magnetic excitation element 9 and therefore the polar element excitation 25 is positioned facing the toothed wheel 11 with a controlled air gap. The assembly is robustly designed to ensure its reliability throughout the life of the engine 1.

  FIGS. 5A and 5B illustrate the detection module 7. FIG. 5A is a view of a longitudinal section of the detection module 7 while FIG. 5B is an exploded view of this detection module 7. According to this example, the detection module 7 comprises a polar detection element 37 made of a soft ferromagnetic material (for example made of 50% nickel alloy) of length equivalent to the magnetic excitation element 9 and comprising several cells 39. An end 37a of the element polar detection 37 constitutes the free end 7a of the detection module 7 opposite the gear 11 while the other end 37b of the polar detection element 37 is magnetically coupled with the transverse yoke 29 of the element magnetic excitation 9 in order to close the magnetic circuit between the magnetic excitation element 9, the detection module and the toothed wheel 11. Indeed, the transverse yoke 29 can a hole 41 (see Figure 4), an outer portion 43 is of conical shape to facilitate the guiding of the detection module 7 with the transverse yoke 29.

  The cells 39 of the detection module 7 are isolated by a plurality of winding insulators 45 in order to receive a plurality of detection coils 47 to form the plurality of detection elements 13. The assembly constituted by the polar element of FIG. detection 37 and the coils 47 is integrated in a protective tube 49 nonmagnetic (for example stainless steel). Optionally, the protective tube 49 comprises an annular abutment element 51 at the end 37b of the polar detection element 37 to allow the detection module 7 to be supported against the transverse yoke 29. detection 7 may advantageously comprise a magnetic sheath 53 shielding disposed between the protective tube 49 and the polar detection element 37. Thus, the magnetic sheath 53 shielding envelopes the polar detection element 37 and its coils 47 before their integration into the protective tube 49 amagnetic.

  According to the example of FIG. 5A, the detection module 7 comprises four coils 47 or detection elements the output terminals of which provide four independent speed measurement channels. As a variant, the polar detection element 37 may comprise another number of cells 39 of varying dimensions enabling the detection module 7 to provide any number of coupled or independent signals.

  In addition, the detection module 7 comprises pressure and positioning means to hold it firmly on the transverse yoke 29 and to ensure a desired positioning of the free end 37a of the polar detection element 37 facing the periphery of the toothed wheel 11 according to the second gap 19b determined.

  Indeed, the detection module 7 comprises a fixing washer 55 at the free end 37a of the polar detection element 37 and an adapter piece 57 on the other end 37b of this polar detection element 37 The fixing washer 55 and the adapter nozzle 57 are for centering and fixing the polar sensing element 37 in the protective tube 49.

  In addition, the adapter tip 57 allows mounting the detection module 7 on an end 59a of a connecting tube 59. This connecting tube 59 (for example stainless steel) may be several tens of centimeters long, provides guiding and protection of electrical connection cables 10 from the plurality of detection elements 13 between, for example, the intermediate casing 33 and the outer casing 61 of the motor (see FIG. 6). In particular, the polar detection element 37 and the adaptation endpiece 57 may comprise holes or slots 62a, 62b to facilitate the passage of the electrical connection cables 10.

  FIG. 6 illustrates the mounting of the variable reluctance device on the intermediate casing 33 and outer casing 61 of the motor 1. According to this example, the connecting tube 59 is fixed at its end 59b 2891361 12 (opposite to that 59a which is coupled to the detection module 7) by a fastening flange 63 mounted at the outer casing 61 of the motor 1. In addition, the fastening flange 63 comprises a pressure means 65, for example a spring or a screw system exerting on the connecting tube 59 and therefore on the detection module 7, an elastic restoring force to maintain the latter bearing against the transverse yoke 29 of the magnetic excitation element 9. This restoring force also maintains the end 7a of the detection module 7 in the desired position, relative to the toothed wheel 11, that is to say with a controlled air gap similar to that of the magnetic excitation element 9. In addition, the assembly formed p ar the detection module 7 and the connecting tube 59 is easily removable to allow any repair.

  Furthermore, the electrical connection cables 10 protected by an insulating envelope 67 leave the connecting tube 59 at the end 59b to be connected to the control means 3. In a variant, the electrical connection cables 10 are connected to at least one connector 68 (dotted) located at the mounting flange 63.

  FIGS. 7A to 8B illustrate other embodiments of a variable reluctance device 5.

  FIG. 7A or 7B shows that in addition to all the elements represented in the preceding figures, the variable reluctance device 5 comprises another magnetic circuit closure element 71. Thus, the housing 15 of the variable reluctance device 5 comprises a additional housing 17c for accommodating this magnetic circuit closure element 71. The free end 71a of the magnetic circuit closure element 71 is positioned facing the toothed wheel 11 with a third determined air gap which may be equal to the first and second determined gaps 19a and 19b. The other end 71b of the magnetic circuit closure element 71 is coupled with the transverse yoke 2891361 13 29 of the magnetic excitation element 9, for example by fitting into an additional hole 72 formed in this transverse yoke 29 Thus, the magnetic circuit closure element 71 and the magnetic excitation element 9 form an additional closed magnetic circuit as a function of the running frequency of the teeth of the toothed wheel 11. This additional closed magnetic circuit is out of phase by to that formed between the detection module 7 and the magnetic excitation element 9.

  Indeed, FIG. 7C is a schematic view from above (arrows C) of the toothed wheel 11. This figure shows that the toothed wheel 11 has a solid portion 11a facing the free end 71a of the excitation element 71 and a toothed portion 11b positioned facing the free ends of the detection module 7 and the magnetic circuit closure element 71. The spacing between the free end 9a of the detection module 7 and the free end 71a of the magnetic circuit closure element 71 is determined according to the spacing of the toothing. This spacing is chosen so that during the rotation (arrow 73) of the toothed wheel 11, the detection module 7 and the magnetic circuit closure element 71 are alternately subjected to a variable magnetic flux generating at the terminals of each sensing coil 47 has a synchronous frequency alternating voltage of the toothing of the toothing.

  By way of example, the spacing corresponds to the width of a tooth 74 plus one half of the pitch 77 of the toothing so that the closed magnetic circuit 79a or the additional closed magnetic circuit 79b is alternately formed on the one hand between the magnetic circuit closure element 71 and the magnetic excitation element 9 and secondly between the detection module 7 and the magnetic excitation element 9 as shown in dashed lines by the references 79a and 79b.

  Of course, in this case the housing 15 has three positioning holes 23a, 23b and 23c for passing the free ends of the three elements 7, 9 and 71 respectively. The arrangement and spacing between these holes is a function of the configuration of the toothed wheel 11.

  The magnetic circuit closure element 71 may be a polar element made of a soft ferromagnetic material making it possible to increase the sensitivity and measurement accuracy of the speed of rotation of the rotating member 6 of the engine 1.

  In a variant, FIGS. 8A and 8B show that the magnetic circuit closure element may be an additional detection module 7 'making it possible to double the number of speed detectors. Thus, according to this example, the variable reluctance device comprises two detection modules 7 and 7 'comprising the same elements as those of Figures 5A and 5B. The two detection modules 7 and 7 'are alternately active as a function of the rotation of the toothed wheel 11. Indeed, FIG. 8A shows that it is the detection module 7 which is active while FIG. 8B shows after the rotation (arrow 73) of the wheel 11 by about one step, it is the additional detection module 7 'which is active.

2891361 15

Claims (14)

  1.Device with variable reluctance for measuring the speed of rotation of a rotating member (6) coupled to a toothed wheel (11) made of ferromagnetic material characterized in that it comprises at least one detection module (7) comprising a plurality of detection elements (13) and a magnetic excitation element (9) arranged in the vicinity of said detection module (7), the detection module and the magnetic excitation element being associated with the toothed wheel (11) in such a way as to form a closed magnetic circuit with a variable air gap as a function of the running frequency of the teeth of the toothed wheel (11), each detection element (13) of said detection module (7) thus delivering an electrical signal representative of the speed of rotation of the rotating member.   2.Dispositif according to claim 1, characterized in that it comprises a housing (15) comprising at least first and second housing (17a, 17b) and in that the magnetic excitation element (9) is fixed jointly in said first housing (17a), one end of said magnetic excitation element (9) being positioned opposite the periphery of the toothed wheel (11) with a first air gap (19a) determined and in that the detection module (7) ) is removably housed in said second housing (17b), one end of said detection module (7) being positioned facing the periphery of the toothed wheel (11) with a second gap (19b) determined.   3.Dispositif according to claim 2, characterized in that said at least first and second housing (17a, 17b) are formed in a screen (21) of conductive material.   2891361 16 4.Dispositif according to any one of claims 1 to 3, characterized in that the detection module (7) comprises a protective tube (49) nonmagnetic protecting a polar detection element (37) of ferromagnetic material, said polar element of detection comprising a plurality of isolated cells (39) for receiving a plurality of coils (47) forming said plurality of sensing elements.   5.Dispositif according to claim 4, characterized in that the detection module (7) comprises a shielding magnetic sheath (53) disposed between the non-magnetic protective tube (49) and the polar detection element (37).   6.Dispositif according to any one of claims 1 and 2, characterized in that the magnetic excitation element (9) comprises a polar excitation element (25) and a transverse yoke (29) of ferromagnetic material, fixed at both ends of a permanent magnet (27).   7.Dispositif according to any one of claims 5 and 6, characterized in that it further comprises positioning means for supporting the detection module (7) against the transverse yoke (29) of the element magnetic excitation (9) and to ensure the positioning of one end of the polar detection element (37) opposite the periphery of the toothed wheel (11) according to the second determined air gap.   8.Dispositif according to any one of claims 2 to 7, characterized in that the first and second air gaps (19a, 19b) determined are equal.   9. Device according to any one of claims 1 to 8, characterized in that it further comprises a magnetic circuit closure element 2891361 17 (71), one end (71a) is positioned opposite the gear wheel (11) so as to form an additional closed magnetic circuit between this element and the magnetic excitation element (9) as a function of the running frequency of the teeth of the toothed wheel (11), said additional closed magnetic circuit being out of phase relative to that formed between the detection module and the magnetic excitation element.   10.Device according to claim 9, characterized in that said magnetic circuit closure element (71) is an additional detection module.   11.Dispositif according to claim 9, characterized in that said magnetic circuit closure element (71) is a polar element of ferromagnetic material.   12.Dispositif according to any one of claims 1 to 11, characterized in that it further comprises a connecting tube (59) for guiding cables (10) electrical connection of the plurality of detection elements ( 13) to control means (3) of the rotating member.   13.Dispositif according to any one of claims 1 to 12, characterized in that it is fixed on a housing (33, 61) of a motor (1).   14. A system for controlling the operation of an engine, in particular an aircraft engine, characterized in that it comprises a device with variable reluctance (5) according to any one of claims 1 to 13.