Patent Publication Number: US-2023150315-A1

Title: Device for measuring tyre pressure

Description:
The present invention relates to a device for measuring a pressure of a tyre to be fitted onto an aircraft. 
     BACKGROUND OF THE INVENTION 
     Conventionally, an aircraft wheel comprises a rim and a tyre received on the rim, the rim and the tyre delimiting an inner volume filled with a pressurised gas. Regulations impose to measure the pressure of the gas contained in the tyre at least once a day. In case of under-inflation of the tyre, the aeroplane is not authorised to take off. 
     The pressure measurement of the gas contained in the tyre is generally taken manually using a manometer connected to an inflation valve integral with the rim and in communication with the inner volume. 
     Tyres fitted with a pressure measuring device embedded inside the tyre intended to facilitate maintenance operations of the ground are known. The pressure measuring device collects digital data relating to the pressure of the gas contained in the tyre and transmits these data by radioelectric waves to a reader arranged remotely, without needing to touch the tyre or perform any manual operation. 
     Such a pressure measuring device generally comprises a housing extending around an electronic board provided with a pressure sensor and with electronic components distributed over the same face of the electronic board. The housing includes channels fluidically connecting the pressure sensor to the outside. A portion of the electronic board extending so as to project laterally from the housing includes an antenna wire connected to a radio transceiver. 
     The pressure measuring device is inserted into a rubber patch adhered to an inner surface of the tyre. The patch is preformed to receive and hold the pressure measuring device in position, and serves to absorb the shocks and deformations to which the tyre is subjected when it is rolling, in particular during the take-off and landing stages. 
     Nevertheless, the rolling of the tyre leads to numerous relative movements between the pressure measuring device and the patch, which eventually deteriorates and no longer provide its role of holding the pressure measuring device on the tread of the tyre, thus causing the latter to be destroyed. 
     OBJECT OF THE INVENTION 
     The invention therefore has the object of proposing a pressure measuring device enabling to at least partially prevent the above-mentioned problem. 
     SUMMARY OF THE INVENTION 
     To this end, according to the invention, a measuring device is provided, comprising: 
     an electronic circuit that is distributed on a first face and a second face of an electronic board and that includes a pressure sensor mounted on the first face of the electronic board; 
     at least one antenna connected to the electronic circuit; 
     a first housing part at least partially covering the first face such that together they delimit a first volume, and comprising at least one first channel fluidically connecting the first volume to the outside; and 
     a second housing part at least partially covering the second face such that together they delimit a second volume, and having at least a bottom for resting against an inner surface of the tyre. 
     According to the invention, the second housing part is arranged such that the antenna projects laterally at least with respect to said second housing part and the device has a centre of gravity located in the second volume spaced apart from the electronic board. 
     By having a centre of gravity located below the electronic board, such a pressure measuring device serves to limit the amplitude of the relative movements between said device and the tyre during rolling of the tyre, and therefore to avoid detachment of the pressure measuring device from said tyre. 
     Particularly, the height of the first housing part is less than the height of the second housing part. 
     Particularly, the first volume is less than the second volume. 
     Particularly, the projected surface of the first housing part on the first face of the electronic board along an axis orthogonal to said first face is inscribed in the projected surface of the second housing part on the same first face and along the same direction. 
     Particularly, the antenna comprises a wire extending inside the electronic board. 
     Particularly, the antenna is substantially triangular in shape. 
     Particularly, the second housing part comprises an outer side surface that is at least partially convex in shape. 
     Particularly, the side wall of the second housing part comprises an outer annular groove forming means for fixing the device to the tyre. 
     Particularly, the housing is generally cylindrical in shape. 
     The invention also relates to a tyre including such a pressure measuring device. 
     According to a particular characteristic, the bottom of the second housing part rest against an inner surface of a tread of the tyre. 
     Particularly, the tyre comprises a connection element adhered to the inner surface of the tread of the tyre, the connection element comprising a receptacle in which the second housing part is inserted. 
     The invention also relates to a wheel comprising such a tyre. 
     The invention further relates to an aircraft landing gear comprising at least one such wheel. 
     The invention will be better understood on reading the following description that is given merely by way of non-limiting illustration of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Reference is made to the accompanying drawings, in which: 
         FIG.  1 A  is a perspective view of a pressure measuring device according to a first embodiment of the invention; 
         FIG.  1 B  is a schematic, cross-sectional view of the pressure measuring device illustrated in  FIG.  1   ; 
         FIG.  1 C  is a detailed view of the electronic board of the pressure measuring device illustrated in  FIG.  1   ; 
         FIG.  2    is a fragmentary diagrammatic section view of an aircraft wheel provided with the pressure measuring device shown in  FIGS.  1 A,  1 B,  1 C ; 
         FIG.  3    is a perspective view of a first variant of the pressure measuring device illustrated in  FIGS.  1 A,  1 B,  1 C ; 
         FIG.  4    is a perspective view of a second variant of the pressure measuring device illustrated in  FIGS.  1 A,  1 B,  1 C ; 
         FIG.  5    is a diagrammatic section view of a third variant of the pressure measuring device illustrated in  FIGS.  1 A,  1 B,  1 C ; 
         FIG.  6    is a diagrammatic section view of a fourth variant of the pressure measuring device illustrated in  FIGS.  1 A,  1 B,  1 C ; 
         FIG.  7    is a diagrammatic section view of a fifth variant of the pressure measuring device illustrated in  FIGS.  1 A,  1 B,  1 C ; and 
         FIG.  8    is a diagrammatic section view of a pressure measuring device according to a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS.  1 A and  1 B , a pressure measuring device  1  according to a first embodiment of the invention comprises a phenolic resin housing  10 , here mainly in the shape of a straight cylinder, extending along a vertical axis Z. The housing  10  comprises a first part  10 . 1  and a second part  10 . 2  arranged on either side of an electronic board  20  extending in a horizontal plane XY. 
     The first part  10 . 1  of the housing  10  delimits, with a first face  20 . 1  of the electronic board  20 , a first “dirty” volume V 1  and forms a cover having an upper, flat-shaped surface  11 . The first housing part  10 . 1  comprises first channels  12  fluidically connecting the first volume V 1  to the outside. 
     The second part  10 . 2  of the housing  10  delimits, with a second face  20 . 2  of the electronic board  20 , a second “clean” volume V 2  and forms a cap having a flat-shaped bottom  13 . The second part  10 . 2  of the housing  10  comprises an outer annular groove  14  forming a gripping means of the pressure measuring device  1  and delimiting with the bottom  13  an outer side surface  15  substantially convex in shape. The outer side surface  15  has a profile presenting, in a plane passing through the axis Z, a first plane zone  15 . 1  and a second plane zone  15 . 2  slightly slope relative to each other but also relative to the axis Z. 
     The first part  10 . 1  and the second part  10 . 2  of the housing  10  respectively have, along the axis Z, a height H 1  and a height H 2 . It should be noted that the height H 1  of the first part  10 . 1  is less than the height H 2  of the second part  10 . 2  and that the volume V 1  is less than the volume V 2 . 
     The electronic board  20  comprises second through channels fluidically connecting the first volume V 1  with the second volume V 2 . The second channels  21  have a circular section, the diameter of which is between 100 and 300 micrometres, preferably 200 micrometres. The first channels  12  have a circular section, the diameter of which is here less than that of the second channels  21 , so as to promote the circulation of air between the first volume V 1  and the second volume V 2  and thus obtain better pressure dynamics between said first and second volumes V 1 , V 2 . 
     As shown in  FIGS.  1 C , an electronic circuit is distributed over the first face  20 . 1  and the second face  20 .  2  of the electronic board  20 . The electronic circuit comprises a pressure sensor  30 , a radio transceiver  31 , a microcontroller  32 , an electromagnetic energy recovery unit  33 , and a battery  34 . The pressure sensor  30  and the radio transceiver  31  are mounted on the first face  20 . 1  of the electronic board  20  and extend into the first volume V 1 . The microcontroller  32 , the energy recovery unit  33 , and the battery  34  are mounted on the second face  20 . 2  of the electronic board  20  and extend into the second volume V 2 . 
     The pressure sensor  30  comprises a mechanical protective cap  35  defining a sealed enclosure at a reference pressure. In this example, the pressure sensor  30  is here a piezoelectric sensor comprising a membrane  36  that extends parallel to the first face  20 . 1  of the electronic board  20  and that is provided with a first electrode  37 . 1 . An upper portion of the cap  35  constitutes a second electrode  37 . 2  of a capacitor. A third channel  22  passing through the electronic board  20  fluidically connects the enclosure delimited by the cap  35  to the second volume V 2 . The third channel  22  has a circular section, the diameter of which is substantially equal to that of the second channels  21 . 
     The energy recovery unit  33  comprises a converter that converts the kinetic energy it captures into electrical energy, which it sends to the battery  34 , in order to store it. In this example, the energy recovery unit  33  comprises a ball that is made of ferromagnetic material and that can move freely in the air gap of a coil. The battery  34  powers the microcontroller  32  and the radio transceiver  31 . 
     As can be seen in  FIG.  1 C , the second channels  21  are provided with metal coating  23  that is obtained by metal plating. 
     Each metal coating  23  is connected to a pole of the battery  34 , specifically a positive pole. A ring  24  extends around each metal coating  23  at a non-zero distance therefrom. In this example, each ring  24  is made by depositing copper in a groove  25  machined in the electronic board  20  and is connected to a first pole of the battery  34 , specifically a negative pole. Advantageously, the ring  24  is set back perceptibly from the first face  20 . 1  of the electronic board  20  so as to create a retention zone. 
     The electronic board  20  further comprises a first side portion  26 . 1  and a second portion  26 . 2  projecting laterally on either side of the housing  10  along a horizontal axis X perpendicular to the axis Z. A wire or an antenna track  27 . 1 ,  27 . 2  connected to the radio transceiver  31  extends inside the first portion  26 . 1  and the second portion  26 . 2 . In this example, the first portion  26 . 1  and the second portion  26 . 2  are substantially identical in shape and specifically are here triangular in shape. 
     As illustrated in  FIG.  2   , the pressure measuring device  1  is placed inside a wheel R of an aircraft landing gear. 
     The wheel R comprises a rim J on which a tyre P is mounted, defining with the rim J an inner volume V filled with pressurised nitrogen. A connection element  40  made of elastomer material serves to fix the pressure measuring device  1  on an inner surface of a tread of the tyre P and to absorb the shocks and deformations to which the tyre is subjected when it is rolling. 
     The connection element  40  comprises a base  41  substantially frustoconical in shape, the large base of which is connected adhesively to the inner surface of the tread of the tyre P and the small base of which forms a bottom  42 . 1  of a receptacle  42  mainly cylindrical in shape. 
     The receptacle  42  comprises a side wall  42 . 2  having an inner surface arranged to cooperate with the outer side surface  15  of the second part  10 . 2  of the housing  10 , and an opening  42 . 3  for inserting the second housing part  10 . 2  of the pressure measuring device  1  into the receptacle  42 . The opening  42 . 3  is defined by an annular rim  42 . 4  arranged to be engaged in the outer annular groove  14  so as to immobilize and retain said second housing part  10 . 2  in the receptacle  42 . 
     The aircraft is equipped with a radio transceiver tuned on emission and reception frequencies of the radio transceiver  31  of the pressure measuring device  1 . 
     In operation, the pressurised air contained in the inner volume V defined by the rim J and the tyre P penetrates, by the first channels  12  of the housing  10 , in the first volume V 1 . The first channels  12  perform a first filtering of the particles (dust, filings, grain of sand . . . ) that might be present in the inner volume V. A second filtering of air is performed by the second channels  21  during its passage from the first volume V 1  to the second volume V 2 . The air present in the second volume V 2  then penetrates into the enclosure defined by the cap  35  of the pressure sensor  30  and acts on the membrane  36 . Under the effect of the pressure of the air in the enclosure, the membrane  36  is deformed and the capacity of the condenser associated with said membrane  36  is modified. A analogue-to-digital converter integrated in the microcontroller  32  converts the capacity of the condenser into a pressure value which is then sent to the radio transceiver of the aircraft using the radio transceiver  31  of the pressure measuring device  1 . 
     The battery  34  establishes a voltage between the metal coating  23  of the second channels  21  and the rings  24  that surround it, thereby electrolytically vaporizing any water that might be obstructing the second channels  21 . The diameter of the second channels  21  promotes water retention by capilarity and contributes to preventing moisture in the air contained in the wheel R from penetrating as far as the second volume V 2 . The retention of moisture in the second channels  21  and the water electrolysis device serves to limit the presence of water on the membrane  36  and to protect the pressure measuring device  1  from the harmful consequences of freezing while the aircraft is in flight. Indeed, the presence of frozen water on the membrane  36  generally renders the pressure sensor  30  inoperative and usually causes its destruction. 
     During periods in which the wheel R is rotating, the energy recovery unit  33  converts the kinetic energy to which the device  1  is being subjected into electrical energy that is stored in the battery  34 . 
     The electronic board  20  is connected to the first part  10 . 1  and the second part  10 . 2  of the housing  10  by an adhesive bead having a flexibility allowing a relative movement between said electronic board  20  and the housing  10 , which serves to limit the transmission of the vibrations and shocks to which the wheel R is subjected to the electronic board  20 . The adhesive presents hardness lying in the range of 30 on the Shore 00 scale to 60 on the Shore A scale. 
     The distribution of the electronic components  30 ,  31 ,  32 ,  33 ,  34  over the first face  20 . 1  and the second face  20 . 2  of the electronic board  20 , and the shape and dimensions of the housing  10  (in particular the heights H 1  and H 2 ) enable the pressure measuring device  1  to have a centre of gravity G located in the second volume V 2 , spaced apart from the electronic board  20 . Furthermore, because of the symmetrical arrangement of the first portion  26 . 1  and the second portion  26 . 2  of the electronic board  20  outside the housing  10 , the centre of gravity G is located substantially on the central axis Z of the housing  10 . 
     By having a centre of gravity G located below the electronic board  20 , the pressure measuring device  1  serves to limit the amplitude of the relative movements between the receptacle  42  and said pressure measuring device  1  caused during the rolling of the wheel R, and therefore to limit the deterioration of the connection element  40  of the device  1  adhered to the tread of the tyre P. The angular clearance of the device  1  is also limited, thus limiting the risk of the antenna striking the inner surface of the tyre. 
       FIG.  3    shows a device  100  that is a first variant of the device  1  illustrated in  FIGS.  1 A,  1 B,  1 C . The pressure measuring device  100  differs from the device  1  in that the housing  10  comprises lugs formed by a first projection  16 . 1  and a second projection  16 . 2  which extend laterally projecting from an upper end of the second part  10 . 2  of the housing  10 . The first projection  16 . 1  and the second projection  16 . 2  are substantially identical in shape and cooperate with the second face  20 . 2  of the electronic board  20  at the first portion  26 . 1  and the second portion  26 . 2  so as to limit the bending of said first and second portions  26 . 1 ,  26 . 2  caused by the rotation of the wheel R under the effect of their own weight. 
       FIG.  4    shows a device  200  that is a second variant of the device  1  illustrated in  FIGS.  1 A,  1 B,  1 C . The pressure measuring device  200  differs from the device  1  in that the first part  10 . 1  of the housing forms a cover having an upper surface  11  of outwardly curved shape while retaining a lower surface of plane shape. The length of the first channels  12  is thus increased. The curved upper surface  11  of the first part  10 . 1  of the housing  10  and the increase in the length of the first channels  12  makes it possible to limit the accumulation of pollutants in the immediate vicinity of the inlet orifices of the first channels  12 . 
       FIG.  5    shows a device  300  that is a third variant of the device  1  illustrated in  FIGS.  1 A,  1 B,  1 C . The pressure measuring device  300  differs from the device  1  in that the first part  10 . 1  of the housing comprises an upper portion  11  generally frustoconical in shape having a flat upper wall through which the first channels  12  pass and which is connected to a frustoconical wall. The addition of a slope to the upper portion  11  enables, as for the device  200 , to limit the accumulation of pollutants in the immediate vicinity of the inlet orifices of the first channels  12 . 
       FIG.  6    shows a pressure measuring device  400  that is a fourth variant of the device  1  illustrated in  FIGS.  1 A,  1 B,  1 C . The device  400  differs from the device  300  in that the first channels  12  pass obliquely through the frustoconical wall of the upper portion  11 . The first channels  12  open inside the first volume V 1  through an orifice that is further from the electronic board  20  than the inlet orifice through which they open outside the volume V 1 . The positioning of the first channels  12  serves to limit the accumulation of pollutants in the immediate vicinity of the inlet orifices of the first channels  12 . 
       FIG.  7    shows a pressure measuring device  500  that is a fifth variant of the device  1  illustrated in  FIGS.  1 A,  1 B,  1 C . The device  500  differs from the device  1  in that the first channels  12  extend parallel to the first face  20 . 1  of the electronic board  20 , thereby enabling, as for the devices  200  to  400 , to limit the accumulation of pollutants in the immediate vicinity of the inlet orifices of the first channels  12 . 
       FIGS.  8    shows a pressure measuring device  600  according to a second embodiment of the invention. The device  600  differs from the device  1  in that the outer side surface  15  of the second part  10 . 2  of the housing  10  has an enlarged diameter in the vicinity of the bottom  13 , so that the projected surface of the first part  10 . 1  of the housing  10  on the first face  20 . 1  of the electronic board  20  along the axis Z is inscribed in the projected surface of the second part  10 . 2  of the housing  10  on the same face  20 . 1  and along the same axis Z, the volume V 2  remaining unchanged. As a result, the centre of gravity G is now closer to the bottom  13  of the housing  10  than to the second face  20 . 2  of the electronic board  20 . Furthermore, the second housing part  10 . 2  thus comprises an external bulge in the vicinity of the bottom  13 , which bulge is closely fitted by the wall of the receptacle  42  to ensure the fixing of the second housing part  10 . 2  to the inner surface of the tyre. 
     Naturally, the invention is not limited to the embodiment described, but covers any variant coming within the ambit of the invention as defined by the claims. 
     Although here, the pressure measuring device includes a housing made of phenolic resin, the invention applies equally well to other types of housing, e.g. such as a housing made of metal, of carbon fibre, of epoxy resin, or other. 
     Although here, the housing is cylindrical in shape, the invention applies to housings of other shapes, for example such as a housing that is egg-shaped, or of rectangular box shape, or of any shape. 
     Although here, the antenna is a portion of the electronic board, the antenna could be constituted by one or more metal wires that may be straight or else wound to form a spring or a spiral, or have another shape. 
     Although here, the electronic board is fixed to the housing using silicone-based flexible glue beads, the invention also applies to other types of connection between the housing and the electronic board enabling a relative movement of the housing and of the electronic board, like for example, a synthetic or natural seal of the rubber or EPDM type. 
     Although here, the first channels, the second channels and the third channel have a circular section, the invention also applies to first channels, second and/or a third channel of different section, like for example, a square or other section. 
     Although here, the pressure measuring device comprises a microcontroller, the invention also applies to other signal processing means, like for example an FPGA, logic gates, or a microprocessor. 
     The invention applies to any means for connecting components to the electronic circuit, like for example by wire, welding/soldering, broaching or sintering connections on a PCB-type support. 
     Although here, the pressure measuring device comprises a radio transceiver (for example, of “RFID”-type), the invention applies to any type of wireless emitting techniques, like for example, a “LoRa”, “edge”, “Wi-Fi”, “Bluetooth”, ultrasound or “IoT”-type 2G, 3G, 4G, 5G protocol. 
     Although here, the pressure measuring device includes an electromagnetic energy converter, the invention applies equally well to other types of energy converter, e.g. such as an inductive kinetic energy converter of piezoelectric type or a thermal energy converter. 
     Although here, the measuring device is placed in an aircraft wheel, the invention also applies to other vehicles, like for example, lorries or motor vehicles. 
     Although here, the tyre is filled with pressurised nitrogen, the invention also applies to tyres filled with other types of pressurised fluid, like for example, air or inert gases, other than nitrogen. 
     Although here, the pressure sensor is of piezoelectric type, the invention applies also to other types of pressure sensor, e.g. such as a sensor that is resistive, inductive, piezoresistive, capacitive, or resonant. 
     Although here, the second channels are provided with a metal coating obtained by metal plating, the invention applies equally to other means for applying a metal coating in the second channels, e.g. such as crimping metal sleeves or applying conductive paint. 
     The second channels may have no metal coating. 
     Although here, the copper ring received in a groove in the first surface of the electronic board extends around each second channel, the invention applies equally to other types of conductive element placed in the proximity of the second channel, e.g. such as a ring that is of square or arbitrary shape, metal plating on the surface of the first electronic board, or printing using a conductive ink. 
     Although here, the pressure measuring device includes a rechargeable battery, the invention applies equally to other types of voltage generator, e.g. such as a primary battery or a capacitor. 
     Although here, the conductive element is connected to a negative pole of the voltage generator and the coating of each second channel is connected to the positive pole of the voltage generator, the invention applies equally to the connection polarities being inverted. 
     Although here, the electronic board is connected by glue beads to the housing, the invention also applies to other types of connection between the housing and the electronic board, like for example one or more elastomer pins extending from the first surface of the electronic board, to the first part of the housing and one or more elastomer pins extending from the second surface of the electronic board to the second face of the housing. 
     Although here, the first portion and the second portion of the electronic board extending outside the housing are rigid portions carrying an antenna, the first and second portions could also be flexible and/or contain conductive elements of other types associated with the components that are under the housing. 
     The pressure measuring device can also comprise a temperature sensor for transmitting the temperature and/or performing a temperature compensation of the measurement of the pressure sensor. The measurement of the temperature can be taken by a dedicated sensor or also be measured on a piezoresistive sensor by the measurement of the input resistance of the sensitive element or by any other combination of resistances of a piezoresistive sensor, the result of which would only provide an image of the temperature, that of the pressure being removed in the combination performed (resistances working longitudinally or transversally, respectively giving positive and negative gauge factors). 
     For measurement redundancy reasons, it can be considered to place several pressure measuring devices in one same wheel. 
     Although here, the shape of the first and second portions of the electronic board are triangular in shape, the invention applies equally well to any other shape, such as, for example, portions rectangular in shape. 
     Although here, the bottom of the housing rest indirectly on the inner surface of the tread of the tyre via a connection element, the bottom can also rest directly on said inner surface of the tread. 
     The volume V 1  may be equal to or greater than the volume V 2  provided that the centre of gravity G is located below the electronic board  20 . For example, it could be envisaged that the bottom  13  of the second part  10 . 2  of the housing  10  is thicker so as to lower the centre of gravity G and that the resulting volume V 2  is substantially equal to the volume V 1 . 
     The diameter of the first channels  12  may be greater than that of the second channels  21  so as to improve the filtration of the air passing from the first volume V 1  towards the second volume V 2  to the detriment of its circulation between said first volume V 1  and said second volume V 2 . 
     The diameter of the third channel  22  may be greater than that of the second channels  21  such that none of the particles filtered by the second channels  21  is able to close the third channel  22 . 
     The electronic circuit may comprise other electronic components instead of and/or in addition to the electronic components  31 ,  32 ,  33 ,  34 . Nevertheless, the so-called “critical” components, i.e. those that might be damaged by particles contained in the inner volume V (dust, filings, grain of sand, . . . ), will preferably be distributed over the second face  20 . 2  of the electronic board  20 , in other words in the second volume V 2 , so as to benefit from the double filtration performed by the first channels  12  and the second channels  21 .