Tachometer for aircraft wheel

Abstract

The invention relates to a tachometer (10) for an aircraft wheel (R) mounted on a shaft (E) for rotation about an axis of rotation (X), comprising a stator (20) intended to be fixed to the shaft (E) and a rotor (30) intended to be rotatably connected to the wheel. According to the invention, either the stator or the rotor comprises at least one non-contact sensor (23) having at least two measurement units (28.1, 28.2) adapted to interact with a plurality of targets (37) carried by the other of the stator or the rotor to generate two signals (S1, S2) representative of the wheel speed, the measurement units being angularly offset from each other about an axis (X), in this way, the direction of rotation of the wheel is detected by combining the two signals.

Description

[0001] The present invention relates to a tachometer for an aircraft wheel. Background of the Invention

[0003] Aircraft landing gear is usually provided with a tachometer for continuously measuring the rotational speed of the wheels of the landing gear. The measured speed constitutes basic data for the anti-skid and anti-lock braking systems of the wheels. The tachometer is therefore a measuring device, the accuracy and reliability of which are indispensable.

[0004] Aircraft wheels are usually mounted on a shaft so as to rotate about an axis of rotation. These tachometers comprise a fixed part for rigid connection to the shaft, and a movable part for rotation by the wheel. The fixed part comprises a sensor having a single Hall effect measurement cell arranged to be positioned diametrically opposite a magnetic target carried by the rotating part in order to generate information about the rotational speed of the wheel.

[0005] In general, the rotating part is guided in rotation relative to the fixed part by means of a bearing and comprises a catch which interacts with a protective cover rigidly connected to the wheel in order to allow the rotating part to rotate.

[0006] In order to overcome the problem of wear on the bearings, document FR-A-2888329 envisages rigidly connecting the rotating part to the protective cover of the wheel. The rotating part is then centred relative to the fixed part without any guide device extending between said fixed part and said rotating part.

[0007] However, the lack of a bearing means that a relatively large air gap must be present between the fixed part and the rotating part in order to avoid any mechanical interference between said fixed part and said rotating part. However, a Hall Effect measurement cell that allows the rotation speed of the wheel to be measured as effectively as the measurement cells of the tachometers of the prior art is incompatible with the size of the air gap required to avoid any risk of mechanical interference.

[0008] Furthermore, such a tachometer does not allow the direction of rotation of the wheels to be determined, which could be very useful during the electric coasting phases.

[0009] Purpose of the Invention

[0010] It is therefore an object of the present invention to propose a use of a contactless sensor for avoiding at least some of the above-mentioned disadvantages. Summary of the invention

[0011] For this purpose, the invention proposes the use of a contactless sensor comprising at least two measuring units for increasing the acceptable air gap between the stator and the rotor of a tachometer of an aircraft wheel, the stator being intended to be fixed to a shaft and the rotor being intended to be rotatably connected to a wheel mounted on the shaft so as to rotate about an axis of rotation, the stator or the rotor carrying a sensor whose measuring units are suitable for interacting with a plurality of targets carried by the other of the stator or the rotor so as to generate two signals representative of the rotation speed of the wheel, and the measuring units being angularly offset from each other about the axis so as to detect the direction of rotation of the wheel by combining the two signals.

[0012] By using two measuring units, the rotational speed of the wheel can be measured at a higher frequency than when using a single measuring unit, so the number of targets can be reduced while increasing their size. The acceptable air gap of the measuring unit is usually directly related to the size of the target. Therefore, increasing the size of the target makes it possible to increase the air gap between the stator and the rotor and thus limit the mechanical interference between the stator and the rotor.

[0013] According to a particular embodiment, the contactless sensor is carried by the stator and the target is carried by the rotor.

[0014] According to particular characteristics, the contactless sensor is a Hall effect sensor.

[0015] According to another particular feature, the rotor comprises a toothed ring having a plurality of teeth regularly distributed angularly around the axis so as to form a target.

[0016] In particular, the toothed ring is made of a paramagnetic material, so that the teeth form a magnetic target. According to another particular feature, the measuring unit extends during operation in a radial direction opposite to the target.

[0017] According to another particular feature, the rotor comprises a wheel cover intended to be fixed to the wheel.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be better understood from the following description, which is purely illustrative and non-limiting and should be read with reference to the accompanying drawings, in which:

[0020] [ Figure 1 ] Figure 1 is a simplified view of an aircraft comprising a main landing gear having a wheel provided with a tachometer according to the invention;

[0021] [ Figure 2 ] Figure 2 yes Figure 1 An axial cross-sectional view of one of the aircraft wheels shown in;

[0022] [ Figure 3 ] Figure 3 yes Figure 2 A perspective view of a tachometer of the present invention shown in FIG.

[0023] [ Figure 4 ] Figure 4 yes Figure 3 An exploded view of the stator of the tachometer shown in FIG.

[0024] [ Figure 5 ] Figure 5 yes Figure 3 An exploded view of the rotor of the tachometer shown in FIG.

[0025] [ Figure 6 ] Figure 6 is shown by installing to Figure 5 A view of the signal delivered by the measuring unit of one of the contactless sensors of the stator is shown.

[0026] Detailed description of the invention

[0027] See also Figure 1 The invention applies to an aircraft A comprising main landing gear P, each of which comprises a strut J having a first end articulated to the structure of the aircraft A and a second end carrying two wheels R received on a shaft E so as to be pivotable about an axis X.

[0028] according to Figure 2 , each wheel R comprises an annular rim 1 on which is mounted a tyre 2. The rim 1 is connected by a disc 3 to a hub 4 mounted on an axle E so as to rotate about an axis X by means of tapered roller bearings 5. In a manner known per se, the rim 1 comprises in this case two half-rims 1a, 1b assembled together by bolts and each half-rim 1a, 1b comprises a bead 6a, 6b holding the tyre 2 on the rim 1.

[0029] According to the invention, wheel R comprises a tachometer 10 mounted at the end of shaft E for measuring the angular rotation speed of wheel R about axis X. The following description relates to a single wheel R, but the invention is of course equally applicable to all or some wheels R of landing gear P.

[0030] The tachometer 10 comprises a stator 20 inserted into the free end of the shaft E and fixed thereto by two bolts (not shown) so that the stator 20 cannot move relative to said shaft E.

[0031] See also Figure 3 and Figure 4, the stator 20 comprises a body 21 having a generally tubular shape and extending along an axis substantially coinciding with the axis of rotation X of the wheel R. The body 21 comprises inside two cavities 22 diametrically opposite each other with respect to the axis X. A Hall effect sensor 23 is housed in each cavity. The two Hall effect sensors 23 are used to ensure the redundancy required for the reliability of the tachometer 10 .

[0032] The cavities 22 are identical and each comprises a side opening 22.1 facing the outside of the body 21 in the radial direction and a front opening 22.2 facing one end of the body 21 in the axial direction and through which the Hall effect sensor 23 is inserted. The side opening 22.1 is generally rectangular in shape and is closed by a sealing cover 24 fixed to the body 21 by means of four screws 25. The front opening 22.2 is generally square in shape and is closed by a plate 26 of the Hall effect sensor 23 fixed to the body 21 using said plate by means of four screws 27.

[0033] The Hall effect sensors 23 are identical and each comprise an electronic board 28 having two Hall effect measurement units 28.1, 28.2 that rotate in a radial direction towards the X axis. In this case, the measurement units 28.1, 28.2 are identical and are substantially equidistant from the axis X. The electronic board 28 is connected to a connector 29 that is suitable for supplying power to the electronic board 28 and for transmitting the signals transmitted by the measurement units 28.1, 28.2 to an electronic processing unit U. The electronic board 28 and the connector 29 each extend on one side of the board 26, the electronic board 28 extending inside the cavity 22 and the connector 29 extending outside the cavity 22. The Hall effect sensors 23 are connected to the electronic processing unit U via a cable coupled to the connector 29, the electronic processing unit being integrated in a remote computer located in a compartment of the landing gear P. In this case, the electronic processing unit 31 comprises, in a manner known per se, a processor and a memory containing a program executed by the processor.

[0034] like Figure 4 As shown in , the measuring units 28.1, 28.2 are axially offset from each other in a direction parallel to the axis X. The measuring units 28.1, 28.2 are also angularly offset from each other about the axis X so that the direction of rotation of the wheel R about said axis X can be detected, as will be explained later.

[0035] It should be noted that enclosing the electronic board 28 and the measuring units 28 . 1 , 28 . 2 of the Hall Effect sensor 23 in the cavity 22 of the body 11 protects them from external damage.

[0036] The tacho 10 also comprises a rotor 30 which, according to the invention, is fixed to the rim 1 of a wheel R such that the rotor 30 cannot move relative to said wheel R.

[0037] See also Figure 3 and Figure 5 , the rotor 30 comprises a wheel cover 31 which is arranged to protect the inner side of the free end of the shaft E and forms a part visible from the outer side of the tachometer 10. The wheel cover 31 is coupled to the rim 1 and for this purpose comprises a first cylindrical bearing surface 32 which interacts with a corresponding bearing surface of the rim 1 to center the wheel cover 31 relative to the rim 1 and the axis of rotation X of the wheel R. The wheel cover 31 is fixed and prevented from rotating on the rim 1 by means of a peripheral clamping collar (not shown) which clamps together a conical bearing surface 33 of the wheel cover 31 and a symmetrical conical bearing surface 7 of the rim 1.

[0038] The wheel cover 31 also comprises a second cylindrical bearing surface 34 which is coaxial with the first cylindrical bearing surface 32 and to which a toothed ring 35 made of paramagnetic steel is fixed by six screws 36. The toothed ring 35 is therefore centered on the axis X and cannot move relative to the wheel cover 31 and thus relative to the wheel rim 1. As in Figure 3 As can be seen in Figure 1 , the toothed ring 35 extends inside the stator 20 and comprises a straight toothing with a plurality of teeth 37 regularly distributed angularly around the axis X. Two adjacent teeth 37 are separated by a space whose width is substantially the same as the width of said teeth 37. Each tooth 37 forms a magnetic target which, during operation, passes opposite each of the measuring cells 28.1, 28.2 of the Hall effect sensor 23 in the radial direction. In this case, the angular offset of the measuring cells 28.1, 28.2 around the axis X corresponds approximately to the angular offset of the half teeth 37. It should be noted that centering the wheel cover 31 on the rim 1 allows the stator 20 and the rotor 30 to be centered on the axis of rotation X of the wheel R without any rotation guide device extending between said stator 20 and said rotor 30. The stator 20 and the rotor 30 thus constitute two autonomous elements that can be mounted independently of each other on the associated member (shaft E or wheel R).

[0039] During operation, the wheel R rotating about the axis X causes the wheel cover 31 and therefore the toothed ring 35 to also rotate about said axis X. The teeth 37 of the toothed ring 35 thus successively pass in front of the measuring units 28.1, 28.2, each tooth then generating a signal S1, S2, the frequency of which represents the rotation speed of the toothed ring 35 and, according to a method known per se, therefore of the wheel R.

[0040] The electronic processing unit U is programmed to use these signals in the manner described below.

[0041] Figure 6 The graph in shows the signals S1, S2 generated by the two measuring units 28.1, 28.2 of one of the Hall effect sensors 23, the wheel R rotating at a substantially constant speed V about the axis X. The signal S1 generated by the measuring unit 28.1 is substantially in the form of a periodic square wave signal, whose period T1 is substantially equal to 8 milliseconds and whose low and high values ​​are substantially equal to 7 mA and 14 mA, respectively. The signal S2 generated by the measuring unit 28.2 is identical to the signal S1, but offset in time by a time delay r, which in this case is substantially equal to 2 milliseconds, taking into account the speed V. The signal S2 is therefore in the form of a periodic square wave signal, whose period T2 is identical to the period T1 of the signal S1 and whose low and high values ​​are identical to those of the signal S1.

[0042] As is known per se, knowing the number of teeth 37 comprised by the toothing of toothed ring 35 makes it possible to deduce from signal S1 (or signal S2) the rotation speed of said toothed ring 35 and therefore of wheel R. Furthermore, knowing the spacing between these teeth makes it possible to determine the rotation speed from the time between two slots; the more slots used, the greater the precision.

[0043] Furthermore, analysis of the time delay r between the signal S1 and the signal S2 makes it possible to determine the direction of rotation of the ring gear 35 and therefore of the wheel R. For example, Figure 6 As can be seen in FIG. 1 , signal S2 lags behind signal S1, which means that the toothed ring 35 rotates from the measuring unit 28.1 toward the measuring unit 28.2. Conversely, if signal S1 lags behind signal S2, this means that the toothed ring 35 rotates from the measuring unit 28.2 toward the measuring unit 28.1. Therefore, it is possible for the computer to receive signals S1, S2 to define the direction of rotation of the wheel R.

[0044] Furthermore, the use of the rising and falling edges of the signals S1, S2 makes it possible to obtain a measurement of the rotational speed V of the wheel R at a higher frequency than that obtained by using the rising and falling edges of a single signal S1 (or a single signal S2). Figure 6 In the example, during a time period equal to the period T1 (or equal to the period T2), two rising edges and two falling edges can be observed when both signals S1 and S2 are used, while only a single rising edge and a single falling edge can be observed when only one of the two signals S1 and S2 is used. Therefore, it is possible for the computer to receive two signals to determine the rotation speed V of the wheel R at twice the frequency by combining the use of the signal S1 with the use of the signal S2.

[0045] While the use of two measuring units 28.1., 28.2 makes it possible to increase the frequency of determining the rotational speed V of wheel R, it is also possible to reduce the number of teeth 37 of toothed ring 35 without compromising the performance of tachometer 10 at a given resolution frequency.

[0046] For example, for a gear ring 35 having fifty teeth, using the rising and falling edges of signals S1 and S2 it is possible to obtain the same resolution frequency as a tachometer comprising a gear having two hundred teeth and a Hall effect sensor having a single measuring unit which uses only the rising edges of the transmitted signals.

[0047] For example, using the rising and falling edges of the signal transmitted by a Hall effect sensor having four measuring units, for a gear ring 35 comprising twenty-five teeth, the same resolution frequency can be obtained as a tachometer comprising a gear ring having two hundred teeth and a Hall effect sensor having a single measuring unit using only the rising edge of the transmitted signal.

[0048] An advantage of reducing the number of teeth 37 of the toothed ring 35 is that the size of the teeth 37 can be increased, thereby relieving the mechanical manufacturing constraints of the toothed ring 35 and allowing a larger air gap between the teeth 37 and the measuring units 28.1, 28.2 for a given resolution frequency.

[0049] It goes without saying that the invention is not limited to the embodiments described, but covers any variant coming within the ambit of the invention as defined by the claims.

[0050] Although the stator 20 in this case includes two Hall effect sensors, it may also include only one, the second sensor simply providing redundancy in the event of a failure of the first sensor. The number of sensors may also be greater than two.

[0051] Although the Hall effect sensor 23 comprises two measuring units 28 . 1 , 28 . 2 in this case, it may also comprise more than two measuring units.

[0052] The Hall Effect sensors 23 do not necessarily need to be diametrically opposed to each other and may be offset at angles other than 180° about the X-axis.

[0053] Although the sensor 23 is a Hall effect sensor in this case, other non-contact sensors may also be used, such as eddy current sensors, magnetoresistive sensors (e.g., anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), tunnel magnetoresistive (TMR) sensors, etc.), optical sensors, etc.

[0054] The Hall Effect sensor may be carried by the rotor 30 , while the magnetic target 37 may be carried by the stator 20 .

Claims

1. Use of a contactless sensor (23) for increasing the acceptable air gap between the stator and the rotor of a tachometer (10) of an aircraft wheel (R), comprising at least two measuring units (28.1, 28.2), the stator (20) being intended to be fixed to an axle (E) and the rotor (30) being intended to be rotatably connected to a wheel mounted on said axle so as to rotate about an axis of rotation (X), either of the stator or the rotor carrying the contactless sensor (23), the measuring units of the contactless sensor being suitable for interacting with a plurality of targets (37) carried by the other of the stator or the rotor in order to generate two signals (S1, S2), and the measuring units being angularly offset from each other about said axis (X) in order to detect the direction of rotation of the wheel by combining the two signals.

2. Use of the non-contact sensor (23) according to claim 1, characterized in that: The non-contact sensor (23) is carried by the stator (20), and the target (7) is carried by the rotor (30).

3. Use of a contactless sensor (23) according to any one of the preceding claims, characterized in that The non-contact sensor (23) is a Hall effect sensor.

4. Use of a contactless sensor (23) according to any one of the preceding claims, characterized in that The rotor comprises a toothed ring (35) having a plurality of teeth (37) regularly angularly distributed around the axis (X) to form a target (37).

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

6. Use of a contactless sensor (23) according to any one of the preceding claims, characterized in that The measuring unit (23) extends in a radial direction opposite to the target (37) during operation.

7. Use of a contactless sensor (23) according to any one of the preceding claims, characterized in that The rotor (30) comprises a wheel cover (31) intended to be fixed to the wheel (R).

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