The present invention relates to a system for monitoring one or more environmental conditions of a tire, particularly air pressure in an airplane tire.
Known pressure monitoring systems are described in the following patent and publication, which are expressly incorporated by reference herein: U.S. Pat. No. 6,889,543, issued May 10, 2005; and PCT Publication WO 2005/109239, published Nov. 17, 2005. See also the references cited and referred to in these documents.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The present invention provides a system for monitoring an environmental condition of a tire. The system can be particularly adapted to monitor tire pressure for each of several tires of an aircraft landing gear. In one embodiment of the invention, a plurality of pressure sensors are provided in each tire, such sensors being carried by the same stem assembly that has the inflation-deflation valve. A communication microcircuit is provided in the stem. The communication microcircuit is connected to one coil of a stem transformer. The other coil of the stem transformer is electrically connected to a coil (the “rotor” coil) of an axle transformer unit. The other coil of the axle transformer unit (the “stator” coil) is coupled to an axle communication circuit. The axle communication circuit is in communication with an information system which is capable of powering the axle and stem circuits and polling the sensor units to determine tire pressure.
In one aspect of the invention, the axle stator coil is mounted in a socket of the outer portion of the axle, and the rotor coil is positioned concentrically inside the stator coil. In this arrangement, the rotor coil can be carried on the inner end of a stub projecting inward from the hubcap which rotates with the wheel.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
A representative aircraft tire-wheel-axle assembly having a tire monitoring system in accordance with the present invention is shown in axial section in
In general, the TPIS powers the board 34 and energizes the primary stator winding 32. Primary winding 32 is coupled to the secondary rotor winding 26 which, in turn, is electrically connected to the electronics of the pressure-sensing valve stem assembly 20. Such assembly also includes primary and secondary coils, microprocessor, and, preferably, a plurality of temperature and pressure sensors for redundant polling of the pressure and temperature of air within the tire. The TPIS communicates with controls and indicators of the aircraft for monitoring the tire pressure and temperature (or the temperature sensor can be used for temperature compensation). In addition, signals passed through the transformer coils at the stem also alter the adjacent magnetic field in such a way that a hand-held probe can be used to measure the tire pressure when the aircraft is on the ground.
Aspects of the stem assembly 20 are best seen in
The stem assembly 20 includes a transformer secondary winding 54 that is electrically coupled to the stem circuit board or a microprocessor 50. A primary winding 56 is telescoped over the secondary winding to complete the communication couple. The two wire cable 22 connects to the primary winding 56 and extends from the assembled unit to the axle transformer. A simplified diagram of the components is shown in
For an aircraft having 14 wheels, there can be 14 driver circuits in the TPIS, one for each wheel. It may be desirable for the aircraft control systems, such as the TBMU, to have updated tire pressure information every two seconds. The TPIS can be designed to drive, modulate, and demodulate four drivers at a time and multiplex the driving such that all 14 wheels can be communicated with in the allotted two-second time frame. With reference to
More specifically, in a representative system, the stem assembly 20 monitoring the pressure of each tire has three individual microcircuits for monitoring the pressure. Each circuit is capable of its own communication. Thus, during the reading of one stem assembly, the TPIS is actually reading three separate channels in sequence. For example, if it were reading wheel one, channel one, it could also be reading channel one of wheels two, three, and four. Then it would read channel two, followed by channel three of the same wheels. After this was done, the TPIS sequences to read wheels five, six, seven, and eight, all three channels of each; then wheels nine through 12 and their three channels. Finally, the TPIS would read wheels 13 and 14 and their three channels.
The sequence to communicate to the stem assembly on any particular wheel can begin by first turning on the driver, which outputs a continuous sine wave of, for example, 134.2 kHz. This continuous signal is coupled from the TPIS differential driver, down the two-wire shielded cables 38 to the axle circuit 34, through the axle transformer, which allows the secondary 26 of the transformer to rotate relative to the primary 32. The secondary 26 of the axle transformer connects by the cable 22 through the hubcap 24 to the stem assembly transformer primary 56. The stem assembly 20 has the internal coil 54 that forms the secondary of the stem transformer.
ASIC modulation parameters can be used for bit timing information. Design and operation can be totally based on standard electronic transformer coupling, such that there are no antennae radiation characteristics, unlike the RF antenna systems used in the patent and publication referred to above. The TPIS box (which may be part of the TBMU) contains the processors, power supplies, and drivers to drive signals and read data from each of the monitored wheels on the airplane.
In the example described above, redundant pressure information from each wheel is communicated to the TPIS which is part of the control system for the aircraft. The driving and communication signal to and from the stem assembly is by way of the magnetic coupling of the stem assembly transformer consisting of primary and secondary coils 56 and 54. The same driving signal can be applied wirelessly adjacent to the stem assembly by a hand-held remote unit 70 of the type shown in
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
This application claims the benefit of Provisional Application No. 60/953,432, filed Aug. 1, 2007, which is expressly incorporated by reference herein.
Number | Date | Country | |
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60953432 | Aug 2007 | US |