Tachometer for an aircraft wheel

Abstract

The invention relates to a tachometer (10) for an aircraft wheel (R) mounted on an axle (E) so as to rotate about an axis (X) of rotation, the tachometer comprising a stator (20) that is intended to be attached to the axle (E) and a rotor (30) that is intended to rotate with the wheel. According to the invention, one of the stator or the rotor comprises at least one contactless sensor (23) having at least two measurement cells (28.1, 28.2) suitable for co-operating with a plurality of targets (37) carried by the other of the stator or the rotor in order to generate two signals (S1, S2) that are representative of a speed of rotation of the wheel, the measurement cells being angularly offset from one another about the axis (X) so as to detect a direction of rotation of the wheel by combining the two signals.

Description

[0001] AIRCRAFT WHEEL TACHOMETER

[0002] The present invention relates to an aircraft wheel tachometer.

[0003] BACKGROUND OF THE INVENTION

[0004] An aircraft landing gear is typically equipped with tachometers to continuously measure the rotation speed of the landing gear wheels. The measured speeds constitute basic data for the anti-skid and anti-lock braking system. Tachometers are therefore measuring devices whose precision and reliability are essential.

[0005] An aircraft wheel is conventionally mounted on an axle to rotate around an axis of rotation. Tachometers comprise a fixed part intended to be secured to the axle and a rotating part intended to be driven in rotation by the wheel. The fixed part comprises a sensor comprising a single Hall effect measuring cell arranged to be placed radially opposite magnetic targets carried by the rotating part to generate information on the rotation speed of the wheel.

[0006] In general, the rotating part is guided in rotation relative to the fixed part by means of bearings and comprises a dog which cooperates with a protective cover secured to the wheel to ensure the rotational drive of the rotating part.

[0007] To overcome the problem of bearing wear, it was envisaged in document FR-A-2888329 to secure the rotating part to the protective cover of the wheel. The centering of the rotating part relative to the fixed part is then ensured without any guide device extending between said fixed part and said rotating part.

[0008] However, the absence of a bearing requires a relatively large air gap between the fixed part and the rotating part to avoid any mechanical interference between said fixed part and said rotating part. However, it turns out that Hall effect measuring cells making it possible to measure the rotational speed of a wheel with the same performance as those of a prior art tachometer do not allow an air gap as large as that necessary to avoid any risk of mechanical interference.

[0009] Moreover, such tachometers do not allow the direction of rotation of the wheels to be determined, which can be very useful during electric taxiing phases.

[0010] SUBJECT OF THE INVENTION

[0011] The invention therefore aims to propose the use of a contactless sensor making it possible to at least partially overcome the aforementioned drawbacks.

[0012] SUMMARY OF THE INVENTION

[0013] To this end, the invention proposes a use of a contactless sensor comprising at least two measuring cells to increase an admissible air gap between a stator and a rotor of a tachometer for an aircraft wheel. The stator is intended to be fixed to an axle and the rotor is intended to be linked in rotation to the wheel mounted on the axle to rotate around an axis of rotation, one of the stator or the rotor carrying the sensor whose measuring cells are adapted to cooperate with a plurality of targets carried by the other of the stator or the rotor to generate two signals representative of a rotation speed of the wheel, and the measuring cells being angularly offset from each other around the axis so as to detect a direction of rotation of the wheel by combining the two signals.

[0014] Using two measuring cells allows the wheel rotation speed to be measured at a higher frequency than with a single measuring cell, and therefore reduces the number of targets while increasing their size. However, the air gap admissible by the measuring cells is, in general, directly linked to the size of the targets. Increasing the size of the targets thus makes it possible to increase the air gap between the stator and the rotor, and therefore to limit mechanical interference between said stator and said rotor.

[0015] According to a particular embodiment, the contactless sensor is carried by the stator, and the targets are carried by the rotor.

[0016] According to a special feature, the non-contact sensor is a Hall effect sensor.

[0017] According to another particular characteristic, the rotor comprises a toothed crown comprising a plurality of teeth distributed angularly in a regular manner around the axis to form the targets.

[0018] In particular, the toothed crown is made of paramagnetic material so that the teeth form magnetic targets.

[0019] According to another particular characteristic, the measuring cells extend, in service, opposite the targets in a radial direction.

[0020] According to another particular feature, the rotor comprises a wheel cover intended to be fixed to the wheel.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be better understood in light of the following description, which is purely illustrative and not limiting, and must be read in conjunction with the appended drawings, among which:

[0023] [Fig. 1] Figure 1 is a simplified representation of an aircraft comprising main landing gears having wheels equipped with a tachometer according to the invention;

[0024] [Fig. 2] Figure 2 is an axial sectional view of one of the wheels of the aircraft illustrated in Figure 1;

[0025] [Fig. 3] Figure 3 is a perspective view of the tachometer of the invention illustrated in Figure 2; [Fig. 4] Figure 4 is an exploded view of the stator of the tachometer illustrated in Figure 3;

[0026] [Fig. 5] Figure 5 is an exploded view of the tachometer rotor shown in Figure 3;

[0027] [Fig. 6] Figure 6 is a view showing the signals delivered by the measuring cells of one of the non-contact sensors equipping the stator illustrated in Figure 5.

[0028] DETAILED DESCRIPTION OF THE INVENTION

[0029] With reference to Figure 1, the invention applies to an aircraft A comprising main landing gear P each comprising a leg J ​​having a first end articulated to a structure of the aircraft A and a second end carrying two wheels R received pivotally on an axle E around an axis X.

[0030] According to Figure 2, each wheel R comprises an annular rim 1 on which a tire 2 is mounted. The rim 1 is connected by a disc 3 to a hub 4 mounted to rotate on the axle E around the axis X by means of tapered roller bearings 5. In a manner known per se, the rim 1 here comprises two half-rims 1a, 1b which are assembled by bolts and which each comprise a bead 6a, 6b trapping the tire 2 on the rim 1.

[0031] According to the invention, the wheel R comprises a tachometer 10 mounted at the end of the axle E to measure the angular speed of rotation of the wheel R around the axis X. The following description relates to a single wheel R, but the invention of course applies in the same way to all or part of the wheels R of the landing gears P.

[0032] The tachometer 10 comprises a stator 20 which is inserted into a free end of the axle E and which is fixed to this free end by means of two bolts (not shown) so that the stator 20 is stationary with respect to said axle E.

[0033] With reference to figures 3 and 4, the stator 20 comprises a body 21 which has a generally tubular shape and which extends along an axis substantially coincident with the axis X of rotation of the wheel R. The body 21 internally comprises two cavities 22 diametrically opposite one another with respect to the axis X. Inside each of the cavities is housed a Hall Effect sensor 23. Two Hall Effect sensors 23 are used to ensure the redundancy necessary for the reliability of the tachometer 10.

[0034] The cavities 22 are identical and each comprise a lateral opening 22.1 facing in a radial direction towards the outside of the body 21, and a front opening 22.2 facing in an axial direction towards one end of the body 21 and through which the Hall effect sensor 23 is inserted. The lateral opening 22.1 is of generally rectangular shape and is closed by a sealed cover 24 fixed to the body 21 by means of four screws 25. The front opening 22.2 is of generally square shape and is closed by a plate 26 of the Hall effect sensor 23 via which said Hall effect sensor 23 is fixed to the body 21 by means of four screws 27.

[0035] The Hall effect sensors 23 are identical and each comprise an electronic card 28 which has two Hall effect measuring cells 28.1, 28.2 facing the X axis in a radial direction. The measuring cells 28.1, 28.2 are here identical and substantially equidistant from the X axis. The electronic card 28 is connected to a connector 29 adapted to the electrical supply of the electronic card 28 and to the transmission of signals delivered by the measuring cells 28.1, 28.2 to an electronic processing unit U. The electronic card 28 and the connector 29 each extend on one side of the plate 26, the electronic card 28 extending inside the cavity 22 and the connector 29 extending outside the cavity 22. The Hall effect sensor 23 is connected, via a cable connected to the connector 29, to the electronic processing unit U which is integrated in a remote computer located in a hold of the landing gear P.The electronic processing unit U here comprises, in a manner known per se, a processor and a memory containing a program executed by the processor.

[0036] As can be seen in Figure 4, the measuring cells 28.1, 28.2 are axially offset from each other in a direction parallel to the X axis. The measuring cells 28.1, 28.2 are also angularly offset from each other around the X axis so as to allow, as will be seen later, the direction of rotation of the wheel R around said X axis to be detected.

[0037] It will be noted that by being enclosed in the cavities 22 of the body 11, the electronic cards 28 and the measuring cells 28.1, 28.2 of the Hall effect sensors 23 are protected from external attacks.

[0038] The tachometer 10 also comprises a rotor 30 which, according to the invention, is fixed to the rim 1 of the wheel R so that the rotor 30 is stationary with respect to said wheel R.

[0039] With reference to Figures 3 and 5, the rotor 30 comprises a wheel cover 31 which is arranged to protect the inside of the free end of the axle E and which forms a portion visible from the outside of the tachometer 10. The wheel cover 31 is attached to the rim 1 and comprises for this purpose a first cylindrical bearing surface 32 which cooperates with a homologous bearing surface of the rim 1 to center the wheel cover 31 with respect to the rim 1 and the axis X of rotation of the wheel R. The wheel cover 31 is fixed and stopped in rotation on the rim 1 by means of a peripheral clamping collar (not shown) enclosing together a conical bearing surface 33 of the wheel cover 31 and a symmetrical conical bearing surface 7 of the rim 1.

[0040] The wheel cover 31 also comprises a second cylindrical bearing surface 34 which is coaxial with the first cylindrical bearing surface 32 and on which is fixed a toothed crown 35 made of paramagnetic steel by means of six screws 36. The toothed crown 35 is thus centered on the axis X and is immobile with respect to the wheel cover 31, and therefore with respect to the rim 1. As can be seen in FIG. 3, the toothed crown 35 extends inside the stator 20 and comprises a straight toothing comprising a plurality of teeth 37 distributed angularly in a regular manner around the axis X. Two neighboring teeth 37 are separated by a space having a width substantially equal to that of said teeth 37. Each of the teeth 37 forms a magnetic target which will pass, in service, opposite each of the measuring cells 28.1, 28.2 of the Hall effect sensors 23 in a radial direction. The angular offset of the measuring cells 28.1, 28.2 around the axis X here corresponds substantially to that of a half-tooth 37. It will be noted that the centering of the wheel cover 31 on the rim 1 makes it possible to center the stator 20 and the rotor 30 on the axis X of rotation of the wheel R without any rotational guidance device extending between said stator 20 and said rotor 30. The stator 20 and the rotor 30 thus constitute two autonomous elements which can be mounted independently of one another on the associated member (axle E or wheel R).

[0041] In operation, a rotation of the wheel R around the axis X causes a rotation of the wheel cover 31, and therefore of the toothed crown 35, around said axis X. The teeth 37 of the toothed crown 35 thus pass in turn in front of the measuring cells 28.1, 28.2 and then each generate a signal Si, Si whose frequency is representative of a rotation speed of the toothed crown 35, and therefore of the wheel R, according to a method known per se.

[0042] The electronic processing unit U is programmed to exploit the signals as explained below.

[0043] Figure 6 illustrates on the same graph the signals Si, Si generated by the two measuring cells 28.1, 28.2 of one of the Hall effect sensors 23, the wheel R rotating around the axis X at a substantially constant speed V. The signal Si generated by the measuring cell 28.1 has substantially the form of a periodic square wave signal whose period Ti is substantially equal to 8 milliseconds and whose low and high values ​​are respectively substantially equal to 7 milliamps and 14 milliamps. The signal Si generated by the measuring cell 28.2 is identical to the signal Si but is temporally shifted by a delay r substantially equal here to 2 milliseconds taking into account the speed V. Thus, the signal Si has the form of a periodic square wave signal whose period Ti is equal to the period Ti of the signal Si and whose low and high values ​​are equal to those of the signal Si.

[0044] In a manner known per se, knowing the number of teeth 37 in the toothing of the crown gear 35 makes it possible to deduce from the signal Si (or from the signal Si) the rotation speed of said crown gear 35, and therefore of the wheel R. Knowing the spacing between the teeth, it is also possible to determine the rotation speed from the time separating two slots, the precision being all the greater as the number of slots used is large.

[0045] Furthermore, the analysis of the delay r between the signal Si and the signal Si makes it possible to determine the direction of rotation of the toothed crown 35, and therefore of the wheel R. For example, we can see in Figure 6 that the signal Si is delayed compared to the signal Si, which means that the toothed crown 35 rotates from the measuring cell 28.1 to the measuring cell 28.2. Conversely, a delay of the signal Si compared to the signal Si means that the toothed crown 35 rotates from the measuring cell 28.2 to the measuring cell 28.1. It is thus possible, for the computer receiving the signals Si, Si, to define the direction of rotation of the wheel R. Furthermore, the exploitation of the rising and falling edges of the signals Si, Si makes it possible to obtain a measurement of the speed V of rotation of the wheel R at a higher frequency than that obtained by the exploitation of the rising and falling edges of the signal Si alone (or of the signal Si alone).For example, we can see in Figure 6 that during a period of time equal to the period Ti (or to the period Ti), two rising edges and two falling edges are observable by exploiting the two signals Si, Si, whereas only one rising edge and one falling edge are observable by exploiting only one of the two signals Si, Si. It is therefore possible, for the computer receiving the two signals Si, Si, to determine the speed V of rotation of the wheel R at a frequency twice as high by combining the exploitation of the signal Si with that of the signal Si.

[0046] If the use of two measuring cells 28.1, 28.2 makes it possible to increase the frequency of determination of the rotation speed V of the wheel R, it can also make it possible to reduce the number of teeth 37 of the toothed crown 35 without degrading the performance of the tachometer 10 for a given resolution frequency.

[0047] For example, by exploiting the rising and falling edges of the signal Si and of the signal Si, it is possible to obtain, with a toothed crown 35 comprising fifty teeth, the same resolution frequency as a tachometer which comprises a toothed crown comprising two hundred teeth and a Hall effect sensor comprising a single measuring cell for which only the rising edges of the delivered signal are exploited.

[0048] For example, by exploiting the rising and falling edges of the signals delivered by a Hall effect sensor provided with four measuring cells, it is possible to obtain, with a toothed crown 35 comprising twenty-five teeth, the same resolution frequency as a tachometer which comprises a toothed crown comprising two hundred teeth and a Hall effect sensor comprising a single measuring cell for which only the rising edges of the delivered signal are exploited.

[0049] Reducing the number of teeth 37 of the toothed crown 35 has the advantage of being able to increase the size of the teeth 37 and therefore of reducing the mechanical manufacturing constraints of said toothed crown 35, but also of allowing a larger air gap between the teeth 37 and the measuring cells 28.1, 28.2 for a given resolution frequency.

[0050] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0051] Although here the stator 20 includes two Hall effect sensors, it can also include only one, the second simply providing redundancy in the event of failure of the first. The number of sensors can also be greater than two.

[0052] Although here the Hall effect sensor 23 comprises two measuring cells 28.1, 28.2, it can also comprise a number greater than two.

[0053] The Hall effect sensors 23 are not necessarily diametrically opposed and can be angularly offset by an angle other than 180 degrees around the X axis.

[0054] Although the sensors 23 here are Hall effect sensors, other non-contact sensors can be used, such as for example eddy current sensors, magnetoresistive sensors (for example of the AMR type from the English “Anisotropic MagnetoResistance”, GMR from the English “Giant MagnetoResistance”, TMR from the English “Tunnel MagnetoResistance”...), optical sensors... The Hall effect sensors can be carried by the rotor 30 and the magnetic targets 37 by the stator 20.

Claims

DEMANDS 1. Use of a non-contact sensor (23) comprising at least two measuring cells (28.1, 28.2) to increase an permissible air gap between a stator and a rotor of an aircraft wheel tachometer (10) (R), the stator (20) being intended to be fixed to an axle (E) and the rotor (30) being intended to be rotationally linked to the wheel mounted on the axle to rotate about an axis (X) of rotation, one of the stator or the rotor carrying the non-contact sensor (23) whose measuring cells are adapted to cooperate with a plurality of targets (37) carried by the other of the stator or the rotor to generate two signals (Si, Si) representative of a rotational speed of the wheel, and the measuring cells being angularly offset from each other about the axis (X) so as to detect a direction of rotation of the wheel by combining the two signals.

2. Use of a non-contact sensor (23) according to claim 1, wherein the non-contact sensor (23) is carried by the stator (20), and the targets (37) are carried by the rotor (30).

3. Use of a non-contact sensor (23) according to any one of the preceding claims, wherein the non-contact sensor (23) is a Hall effect sensor.

4. Use of a non-contact sensor (23) according to any one of the preceding claims, wherein the rotor comprises a toothed ring (35) having a plurality of teeth (37) regularly spaced angularly around the axis (X) for form the targets (37).

5. Use of a non-contact sensor (23) according to claim 4, wherein the toothed ring (35) is made of paramagnetic material so that the teeth form magnetic targets (37).

6. Use of a non-contact sensor (23) according to any one of the preceding claims, wherein the measuring cells (23) extend, in operation, towards the targets (37) in a radial direction.

7. Use of a non-contact sensor (23) according to any one of the preceding claims, wherein the rotor (30) comprises a wheel cover (31) for attachment to the wheel (R).

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