Wheel assembly provided with a pressure sensor

A wheel assembly includes a wheel having a rim which is adapted to receive a tire. The wheel carries a sensor for measuring pressure inside the tire. The wheel is mounted so as to rotate around a spindle. In addition a communication device is located between the sensor and a device which is associated with the spindle for using measurements that are performed by the sensor. The communication device comprises a radio transmission device which includes a rotary antenna carried by the wheel and a fixed antenna that is carried by the spindle.

The present invention relates to a wheel assembly of the type comprising:a wheel having a rim adapted to receive a tire, the wheel carrying a sensor for measuring pressure inside the tire;a spindle around which the wheel is mounted to rotate; andcommunication means between the sensor and means associated with the spindle for making use of measurements performed by the sensor.

BACKGROUND OF THE INVENTION

In airplanes, it is useful, from within the cockpit, to be able to determine the pressure of tires on wheels in the landing gear.

For this purpose, it is known to mount a pressure sensor on the wheel rim, which sensor is suitable for measuring the inflation pressure of the tire mounted on the rim. The pressure sensor sends the value of the measurement it performs to an information processor unit placed on the fixed portion of the landing gear or inside the body of the airplane.

This makes it necessary to provide means for transmitting information between the moving and the fixed portions of the landing gear.

In particular, it is known to provide two concentric coils respectively on the hub of the wheel and on the spindle on which the hub is mounted to rotate, the coils together constituting a transformer. The coil carried by the hub is connected to the pressure sensor while the coil carried by the wheel spindle is connected to the information processor unit.

The signal delivered by the sensor to the coil carried by the hub and corresponding to the value of the pressure in the tire induces a signal in the coil carried by the spindle of the landing gear. This signal is analyzed by the information processor unit in order to deduce therefrom the pressure in the tire.

That solution operates in satisfactory manner. Nevertheless, the presence of two concentric coils makes the arrangement relatively bulky. Using a transformer to transmit information between two mutually rotary portions requires precautions to be taken concerning the electromagnetic environment.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the invention is to provide a solution to this problem by proposing a wheel assembly enabling information to be transmitted between the wheel and the fixed portion supporting the wheel by means of an arrangement that is reliable and compact.

To this end, the invention provides a wheel assembly of the above-specified type, wherein said communication means comprise radio transmission means including a rotary antenna carried by the wheel and a fixed antenna carried by the spindle.

In particular embodiments, the wheel assembly further comprises one or more of the following characteristics:the spindle has a free end, and the fixed antenna and the rotary antenna are disposed in the vicinity of the free end of the spindle;the rotary antenna and the fixed antenna are placed facing each other in succession in line with the spindle;the rim includes a hub with a through passage in which the spindle is engaged, and it further includes a cap closing said passage in line with the free end of the spindle, the rotary antenna being carried by the cap on its face looking towards the spindle, the cap, the spindle, and the hub defining an essentially closed space within which the rotary antenna and the fixed antenna are confined;the rotary antenna and the fixed antenna are generally circularly symmetrical, and they are disposed substantially coaxially about the axis of rotation of the wheel;each of the rotary antenna and the fixed antenna comprises a set of metal turns carried by a support, which turns form the transmission and/or reception elements of the antenna; andsaid set of metal turns of the rotary antenna is carried directly by the cap forming a support.

MORE DETAILED DESCRIPTION

The wheel assembly10shown inFIG. 1forms part of the landing gear of an airplane. It includes a landing gear spindle12constituting a fixed portion, and a wheel14mounted to rotate about the axis X—X of the spindle.

The spindle12has a generally tubular body16about the axis X—X. The body16is connected at one end18to the remainder of the structure of the landing gear. At its other end, referenced20, the body16forms a free end of the spindle.

The wheel14is mounted to rotate about the spindle12via two roller bearings22that are spaced apart along the axis of the spindle.

The wheel14comprises a rim23on which a tire (not shown) is mounted. The rim23comprises a hub24with a through passage25along which the spindle12extends together with the two bearings22.

The rim23also has an outer cylindrical wall26for supporting a tire. The hub24and the wall26are interconnected by radial arms28separated from one another by ventilation slots30.

A pressure sensor31is mounted on the wheel. To this end, and in conventional manner, the cylindrical wall26of the wheel is fitted with a housing32in which a pressure probe34of the sensor is mounted for the purpose of measuring the pressure inside the tire on the wheel. The sensor31also includes a signal processing and probe controlling module35, said module being connected to the probe.

An information processor unit36is secured to the fixed portion of the landing gear or to the airplane body.

The sensor31and the information processor unit36are connected to each other by communication means given overall reference40. These communication means are adapted to establish radio communication between the sensor31and the information processor unit36. This transmission is both-way, i.e. each entity can send and receive information.

In addition, the communication means are adapted to use radiowaves to transmit the electrical energy needed to enable the sensor31to operate.

More precisely, the communication means40comprise a signal modulator/demodulator (modem) unit42carried by the wheel14. This signal-shaping unit is connected both to the sensor31and to a rotary antenna44secured to the wheel.

In analogous manner, the communication means40also comprise a signal modem unit46carried by the spindle and connected to the information processor unit36. This unit46is connected to a fixed antenna48carried by the spindle12.

The antennas44and48are adapted to enable signals to be transmitted and received at radio frequencies. Advantageously, these signals are at a frequency lying in the range 125 kilohertz (kHz) to 2.2 gigahertz (GHz).

The antennas44and48are disposed facing each other so as to establish radio communication between the moving and fixed portions of the wheel assembly.

For this purpose, they are disposed in the vicinity of the free end20of the spindle. They extend substantially parallel to each other in planes perpendicular to the axis of rotation X—X of the wheel. These antennas are located at the end of the landing gear spindle12, in its extension.

As shown inFIG. 2, each antenna is of generally circular symmetry. Thus, it comprises a rigid support ring60having a set of conductive metal turns62placed on one face thereof to form a radiating element. By way of example, these turns can be formed by tracks of a printed circuit.

Advantageously, both antennas44and48are of substantially identical dimensions. The radiating elements of the antennas are placed facing one another.

The antennas are thus disposed coaxially about the axis of rotation X—X of the wheel.

As shown inFIG. 1, the antenna48which is essentially identical to the antenna44is fixed at the free end20of the spindle. For this purpose, the support ring60of the antenna has a skirt64enabling it to be fastened to the outside surface of the spindle12. More precisely, the antenna48is secured by the skirt64to a ring66screwed onto the spindle and serving to retain one of the bearings22in an axial direction.

The rotary antenna44placed facing the fixed antenna48is carried by a cap-forming cup70fitted to the rim23on the axis thereof. The cup70has an end wall72having the antenna44secured thereto. It also has a slightly tapering side wall74. The periphery of this wall is fastened to an axial collar76formed on the rim. This fastening is provided by a ring78, for example.

The cap formed by the cup70is located in line with the passage25passing through the hub, beyond the free end of the spindle. It thus serves to closes the passage25.

The cap70co-operates with the end of the hub24and with the end of the spindle12to define a closed space80in which the antennas44and48are confined and in which they are protected from external attack.

In order to measure pressure, the information processor unit36controls the unit46so as to cause it to send a modulated signal from the fixed antenna48to the rotary antenna44. This signal conveys information enabling the sensor31to be controlled. This signal also conveys the energy required for powering the unit42and the sensor31.

The signal received by the rotary antenna4is demodulated and sent to the sensor31. Under the control of the module35, the sensor sends a reply to the modem unit42containing the result of the measurement performed by the probe34. The signal as shaped by the unit42is then transmitted by the rotary antenna44and picked up by the fixed antenna48. This signal as picked up is forwarded to the information processor unit36for further use.

It will be understood that the use of radio communication means reduces the overall bulk of the wheel assembly. Furthermore, the disposition of complementary antennas in line with the free end of the wheel spindle makes it possible to obtain good proximity of the antennas in a compact configuration. Furthermore, since the antennas are located inside the cup70they are protected from mechanical attack and from electromagnetic disturbance from the surroundings.

Finally, since the antennas have circular symmetry and are placed coaxially on the axis of rotation of the wheel, they always face each other and continuously provide each other with the same facing areas. As a result transmission quality is unaffected by wheel rotation.

In a variant embodiment, the rotary antenna44is formed directly on the cup70which is fitted to the wheel rim. Under such circumstances, the radiating elements, e.g. constituted by conductive turns, are made directly on the end wall of the cup70, in which case the end wall itself is made of a material that does not conduct electricity.