Resonant pressure sensor, measurement assembly and associated aircraft

Abstract

A resonant pressure sensor (5) is proposed. The sensor comprises: - a support (6) having a base (7) surrounded by at least one wall (8, 9), - a deformable membrane (12) having a first face (13) configured to be subjected to the pressure to be measured and a second face (14) opposite the first face, the second face being connected to the support so that the support and the deformable membrane form a hermetically sealed cavity (15), the cavity being filled with a predetermined quantity of gas. The hermetically sealed cavity (15) comprises: - a temperature sensor (17) separate from the deformable membrane and configured to measure the temperature of the gas, and - a first beam (16) separate from the deformable membrane and having a first end (18) embedded in the wall and a second free end (19), the first beam being configured to measure the density of the gas. Figure for the abstract: Fig 2

Description

Title of the invention: Resonant pressure sensor, measuring assembly and associated aircraft. Technical field

[0001] The invention relates to the architecture of pressure sensors, and more particularly to the architecture of a resonant pressure sensor.

[0002] The invention further relates to a measurement system and an aircraft comprising such a sensor. Previous techniques

[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0007] Generally, non-resonant pressure sensors are implemented to measure pressure.

[0008] A non-resonant pressure sensor delivers static or quasi-static signals that are a direct or quasi-direct representation of the pressure applied to a deformable membrane of the sensor. The signal is conditioned and processed by a processing circuit to condition and process the signal delivered by the sensor.

[0009] The processing circuit is arranged close to the sensor to increase the signal-to-noise ratio of the signal delivered by a measurement chain comprising the processing circuit and the sensor.

[0010] In an aircraft, pressure sensors are notably disposed in aircraft propulsion means, for example in turbomachinery.

[0011] In such an environment, the temperature is generally above 175 °C.

[0012] However, the sensor and conditioning circuit are not suitable for continuous and long-term operation in such an environment.

[0013] It is known to relocate the conditioning circuit to a less hot environment and to connect said circuit and the sensor by a wired link.

[0014] It is known that the longer the wired link, the more the signal-to-noise ratio is degraded, so that the determination of the amplitude of the signal representative of the measured pressure is degraded.

[0015] It is further known to dispose of the sensor and the conditioning circuit located near the sensor in a less hot environment compatible with the conditions of proper operation of the sensor and the conditioning circuit, and to convey the measured pressure through a circuit of piping (capillary) passing through compartments of the propulsion means.

[0016] However, it is necessary to plan the routing of the piping and the space to implement said piping in a very constrained environment.

[0017] In addition, the pipes are sensitive to condensation phenomena which can lead to failure of the measurement chain comprising the pipes, the sensor and the conditioning circuit.

[0018] It is known to implement a resonant pressure sensor delivering a frequency modulated signal.

[0019] Such a signal is less sensitive to disturbances, in particular to electromagnetic disturbances, so that the sensor can be disposed in an environment with a high temperature, in particular above 175 °C, and the signal processing circuit can be located in a less hot environment, while still allowing signal processing by said circuit.

[0020] A resonant pressure sensor known in the prior art comprises a mechanical resonator mounted on and in contact with a deformable membrane, the resonator acting as a strain gauge.

[0021] The mechanical resonator generally comprises a beam embedded at each of its ends in a support and connected to the deformable membrane.

[0022] When pressure is exerted on the deformable membrane, mechanical stresses are transferred to the resonator causing a variation in the resonance frequency of the deformable membrane representative of the pressure exerted on the deformable membrane.

[0023] However, since the mechanical resonator is in contact with the deformable membrane, the repetitive mechanical stresses associated with the deformation of the membrane are likely to deteriorate the resonating element.

[0024] In addition, the deformable membrane transmits to the resonator all the disturbance phenomena related in particular to the nature of the flow of a fluid on the deformable membrane, for example when the flow is turbulent.

[0025] In addition, as the beam is embedded at each of its ends in a support linked to the deformable membrane, the resonance frequency of the beam is very sensitive to physical phenomena that may occur on the membrane which can induce drift and long-term instability of the beam and therefore significantly alter the pressure measurement. Description of the invention

[0026] The aim of the invention is to overcome all or part of these drawbacks, in particular by proposing a new architecture of a resonant pressure sensor delivering measurements less sensitive to the phenomena of physical disturbances suffered by the membrane and having an increased lifespan.

[0027] To this end, the invention is the result of technological research aimed at significantly improving the performance of measurement systems, particularly in the aeronautical environment. In this sense, the invention contributes to reducing the environmental impact of aircraft.

[0028] For this purpose, the invention relates to a resonant pressure sensor.

[0029] The sensor comprises:

[0030] - a support comprising a base surrounded by at least one wall, and

[0031] - a deformable membrane having a first face configured to be subjected to the pressure to be measured and a second face opposite to the first face, the second face being connected to the support so that the support and the deformable membrane form a hermetic cavity, the cavity being filled with a predetermined amount of gas.

[0032] The airtight cavity comprises:

[0033] - a temperature sensor separate from the deformable membrane and configured for measure the temperature of the gas, and

[0034] - a first beam separated from the deformable membrane and comprising a first end embedded in the wall and a second end free, the first beam being configured to measure the density of the gas.

[0035] The first beam and the temperature sensor are not in contact with the deformable membrane so that the resonant pressure sensor is less sensitive to disturbance phenomena generated, for example, by the nature of the flow of a fluid on the first face of the deformable membrane, the vibrations of the membrane and the residual mechanical stresses of the membrane, and so that the life of the pressure sensor, the immunity to disturbances and the long-term stability of the pressure sensor are improved compared to a known prior art pressure sensor.

[0036] Since only one end of the first beam is embedded in the wall of the support, the pressure sensor is more stable in frequency than a resonant pressure sensor which generally has a resonant element embedded at each of its ends.

[0037] As the temperature sensor and the first beam are encapsulated in the hermetically sealed cavity, the density and temperature measurements are less sensitive to external disturbance phenomena.

[0038] Furthermore, the sensitivity of the pressure sensor to the pressure exerted by the fluid on the first face of the deformable membrane is easily configurable by modifying only the volume of the cavity and / or the quantity or molar mass of the gas contained in the cavity.

[0039] In addition, the measurement resolution of the pressure sensor is easily configurable by choosing the quantity of gas trapped in the cavity.

[0040] Preferably, the width of the first beam is greater than the length of the first beam.

[0041] Advantageously, the first beam is of rectangular, trapezoidal or triangular geometry.

[0042] Preferably, the first beam is in the shape of a T or an M.

[0043] Advantageously, the pressure sensor includes piezoresistive gauges arranged between the wall and the first end of the first beam to measure a displacement of the first beam. Advantageously, the temperature sensor includes a second beam separate from the deformable membrane and comprising a first end embedded in the wall and a second free end, the second beam being configured to measure the temperature of the gas.

[0044] Preferably, the length of the second beam is greater than the width of the second beam. For example, the length of the second beam is five times greater than the width of the second beam.

[0045] Advantageously, the deformable membrane comprises a branch opening onto the second face, the branch being arranged on the periphery of the deformable membrane in the airtight cavity.

[0046] A pressure measurement system is also proposed comprising:

[0047] - a resonant pressure sensor as defined above,

[0048] - measuring means configured to measure the resonance frequency of the first beam,

[0049] - of the first means of determination configured to determine the value of the density of the gas in the cavity based on the resonance frequency delivered by the measuring means, and

[0050] - second means of determination configured to determine the pressure submitted on the first face of the deformable membrane from the value of the density of the gas and the value of the temperature of the gas delivered by the temperature sensor.

[0051] An aircraft comprising a resonant pressure sensor as defined above is also proposed. Brief description of the drawings

[0052] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0053] - Figure [Fig. 1] schematically illustrates an example of an aircraft according to a example of the invention,

[0054] - Figures [Fig.2] and [Fig.3] schematically illustrate a first example of fabrication of a resonant pressure sensor according to the invention,

[0055] - Figures [Fig.4], [Fig.5], [Fig.6] and [Fig.7] schematically illustrate examples of the realization of a first beam of the resonant pressure sensor according to the invention,

[0056] - Figure [Fig.8] schematically illustrates an example of the embodiment of a unit of treatment according to the invention, and

[0057] - Figure [Fig.9] schematically illustrates a second example of the embodiment of resonant pressure sensor according to the invention. Detailed description

[0058] Reference is made to [Fig.1] which schematically illustrates an example of an aircraft 1 comprising propulsion means 2 including, for example, turbojets or turboprops equipped with turbomachinery 3.

[0059] Aircraft 1 as represented is an airplane.

[0060] Alternatively, aircraft 1 is a helicopter.

[0061] The aircraft 1 further comprises at least one measurement system 4 comprising a resonant pressure sensor 5 and a processing unit UT connected to the pressure sensor 5.

[0062] The pressure sensor 5 is arranged for example in the turbomachine 3 to measure the exhaust gas pressure of the turbomachine 3.

[0063] The exhaust gas temperature is generally above 175 °C.

[0064] Of course, the pressure sensor 5 can measure pressure for another application, for example oil pressure, liquid pressure, pressure in an aircraft cabin 1.

[0065] The UT processing unit is located in a location in the aircraft 1 with environmental conditions ensuring optimal and long-term operation of the UT processing unit, for example in a location in the aircraft 1 with a temperature below 60°C.

[0066] The processing unit UT is for example located in the fuselage of the aircraft 1, and connected to the pressure sensor 5 by a cable.

[0067] Figures 2 and 3 schematically illustrate a longitudinal section and a section along the section line III-III of a first example of an embodiment of the sensor 5.

[0068] The pressure sensor 5 includes a support 6 having a base 7 and walls 8, 9, 10, 11 surrounding the base 7.

[0069] The support 6 as shown is rectangular.

[0070] Of course, the support 6 can have a different shape, for example cylindrical with a single cylindrical wall.

[0071] The pressure sensor 5 further includes a deformable membrane 12 having a first face 13 intended to be subjected to the pressure to be measured and a second face 14 opposite to the first face 13.

[0072] The second face 14 is connected to the walls 8, 9, 10, 11 so that the support 6 and the membrane 12 form a hermetic cavity 15.

[0073] The cavity is filled with a gas of molar mass M, for example dinitrogen N2. The amount of gas in the cavity is predetermined according to the sensitivity and range requirements of the measurement delivered by the pressure sensor 5.

[0074] The pressure sensor 5 further includes a temperature sensor 17 separate from the membrane 12 and suitable for measuring the temperature Te of the gas present in the cavity 15, and a first beam 16 separate from the deformable membrane 12 so that the first beam 16 is not in contact with the membrane 12.

[0075] We denote V the volume of cavity 15.

[0076] The temperature sensor includes, for example, a second beam 17a separated from the membrane 12. The second beam 17a is, for example, rectangular.

[0077] The first beam 16 comprises a first end 18 embedded in a first wall 8 and a second free end 19.

[0078] The length of the first beam 16 is referenced 116 and the width of the first beam 16 is referenced Li6.

[0079] The first beam is suitable for measuring the density ρ of the gas present in cavity 15.

[0080] In order to maximize the sensitivity of the first beam 16 to variations in density p of the gas contained in the cavity 15, the width Li6 of the first beam 16 is greater than the length li6 of the first beam 16.

[0081] The first beam 16 is, for example, rectangular.

[0082] Alternatively, the first beam 16 can be trapezoidal ([Fig.4]), the larger base of the trapezoid being embedded in the wall 8 and the smaller base of the trapezoid being free.

[0083] According to yet another variant, the first beam 16 can be triangular ([Fig.5]), the longest side of the triangle being embedded in the wall 8.

[0084] When piezoresistive gauges (not shown) arranged between the first wall 8 and the first end 18 of the first beam 16 are used to track displacements of the first beam 16, the first beam 16 is preferably T-shaped ([Fig.6]) or M-shaped ([Fig.7]) improving the signal-to-noise ratio of a signal delivered to the piezoresistive gauges and thus the resolution of the density measurement p.

[0085] When the first beam 16 is in the shape of T ([Fig.6]), it comprises a first bar 16a arranged substantially parallel with the first wall 8, and a second bar 16b substantially perpendicular to the first wall 8. The second bar 16b comprises a first end embedded in the first wall 8 and a second end connected to the first bar 16a.

[0086] When the first beam 16 is in the shape of M ([Fig.7]), it comprises a first bar 16c arranged substantially parallel with the first wall 8, and second, third and fourth bars 16b, 16e, 16f substantially perpendicular to the first wall 8. Each bar 16b, 16e, 16f comprises a first end embedded in the first wall 8 and a second end connected to the first bar 16c.

[0087] The third bar 16e is arranged between the first and fourth bars 16d, 16f.

[0088] The second beam 17a comprises a first end 20 embedded in the wall 8 and a second free end 21.

[0089] The length of the second beam 17a is referenced 117 and the width of the first beam 17a is referenced Lp.

[0090] In order to maximize the sensitivity of the second beam 17a to temperature variations T of the gas contained in the cavity 15, the length li7 of the second beam 17 is greater than the width Lp of the second beam 17.

[0091] The length li7 of the second beam 17 is for example five times greater than the width L[7 of the second beam 17.

[0092] Analysis of the resonance frequency of the first beam 16 makes it possible to determine the density ρ of the gas present in the cavity 15.

[0093] Analysis of the resonance frequency of the second beam 17a allows the temperature Te of the gas in the cavity 15 to be determined. Since the resonance frequency of a beam depends mainly on the variations of the Young's modulus generated by the variations of the temperature, the geometry of the second beam 17 is suitable for measuring the temperature.

[0094] Of course, the pressure sensor 5 can include a second temperature sensor comprising, for example, a third beam suitable for measuring the temperature of the gas and a fourth beam suitable for measuring the density of the gas in order to increase the reliability of the pressure sensor 5 by redundantly determining the temperature of the gas in the cavity 15 and determining the density of the gas in the cavity 15.

[0095] The value of the pressure exerted for example by a fluid on the first face 13 of the membrane 12 is determined, for example, by applying the ideal gas law from the value of the density p and the value of the temperature Te delivered respectively by the pressure sensor 5.

[0096] Since the cavity 15 is airtight, the amount of gas in the cavity 15 is constant. The sensitivity of the membrane 12 is equal to the difference in pressures applied to the first and second faces 13 and 14 of the membrane 12.

[0097] When the pressure applied on the first face 13 is greater than the pressure applied on the second face 14, the deformation of the membrane 12 resulting from the difference in pressure applied on the first and second faces 13, 14 causes a variation in the volume of the airtight cavity 15.

[0098] The variation in the volume of the hermetic cavity 15 causes a variation in the density of the gas in the hermetic cavity 15.

[0099] According to the ideal gas law:

[0100] P^pRTe(l)

[0101] R being the ideal gas constant and P the pressure.

[0102] The pressure exerted on the first face 13 of the membrane 12 is determined by the processing unit UT from equation (1), the resonance frequency of the first beam 16 and the resonance frequency of the second beam 17a.

[0103] Alternatively, when the temperature sensor 17 includes another type of resonator replacing the second beam 17a, the resonator including for example a surface acoustic wave sensor, the pressure exerted on the first face 13 of the membrane 12 is determined by the processing unit UT from equation (1), the resonance frequency of the first beam 16 and the temperature measurement delivered by the temperature sensor 17.

[0104] Fig. 8 schematically illustrates an example of an embodiment of the processing unit UT.

[0105] The processing unit UT includes measuring means 30 suitable for measuring the resonance frequency of the first beam 16.

[0106] When the temperature sensor 17 includes the second beam 17a, the frequency measurement means 30 are further able to measure the resonance frequency of the second beam 17a.

[0107] Furthermore, the processing unit UT includes first determination means 31 suitable for determining the value of the density p and the value of the temperature Te of the gas in the cavity 15, from the resonance frequencies of the first beam 16 and the second beam 17a delivered by the measuring means 30. Correlations between the resonance frequencies of the first and second beams 16, 17a and the values ​​of the density p and the temperature Te are made to compensate for the undesirable effects of temperature on the behavior of the first beam 16 and the effects of density on the behavior of the temperature sensor 17.

[0108] When the temperature sensor 17 does not include the second beam 17a and includes another type of resonator, the first means 31 determine the value of the temperature Te of the gas in the cavity 15 from the measurements delivered by the other type of resonator.

[0109] The processing unit UT includes second determination means 32 suitable for determining the pressure P from equation (1).

[0110] Alternatively, the measuring means 30, first means 31 and second means 32 are realized in the form of algorithms implemented by the processing unit UT.

[0111] Unlike a known prior art pressure sensor, the first beam 16 and the temperature sensor 17 are not in contact with the membrane 12 so that the resonant pressure sensor 5 is less sensitive to disturbance phenomena generated for example by the nature of the flow of a fluid (for example a turbulent flow) on the first face 13 of the membrane 12 and so that the life of the pressure sensor 5 is improved in the absence of mechanical stresses related to the deformation of the membrane exerted directly on the first beam 16 and the temperature sensor 17.

[0112] Only one end of the first beam 16 and where applicable of the second beam 17a is embedded in the wall of the support so that the pressure sensor 5 is more stable in frequency than a resonant pressure sensor generally having a resonant element embedded at each of its ends.

[0113] As the temperature sensor 17 and the first beam 16 are encapsulated in the hermetically sealed cavity 15, the density and temperature measurements are less sensitive to external disturbance phenomena, for example to the flow rate and nature of the flow of a fluid in contact with the first face 13 of the membrane 12 so that the determination of the pressure exerted by the fluid on the first face 13 of the membrane 12 is less sensitive to external disturbance phenomena.

[0114] Furthermore, the sensitivity of the pressure sensor 5 to the pressure exerted by the fluid on the first face 13 of the membrane 12 is easily configurable by modifying only the volume V of the cavity 15 and / or by adjusting the amount of gas in the cavity 15, without modifying the first beam 16 and / or the membrane 12 and / or the second beam 17a.

[0115] In addition, the measurement resolution of the pressure sensor 5 is easily configurable by choosing the amount of gas to be trapped in the cavity 15. The lower the amount of gas (low pressure relative to temperature), the better the quality factor of the first beam 16 and, where applicable, of the second beam 17, so that the resolution is improved.

[0116] Fig. 9 schematically illustrates a longitudinal section of a second example of an embodiment of the pressure sensor 5.

[0117] The second embodiment of the pressure sensor 5 differs from the first embodiment of the pressure sensor 5 illustrated in [Fig.2] in that the diaphragm 12 includes a groove 15 opening onto the second face 14 and being disposed around the circumference of the diaphragm 12 in the hermetically sealed cavity 15.

[0118] The thickness of the membrane 12 including the groove 35 is greater in its centre than on its periphery arranged in the cavity 15 so that the displacement of the membrane is greater compared to the membrane 12 having a constant thickness as illustrated in [Fig.2] and this for an identical pressure exerted on the first face 13 of the member 12.

[0119] A thickening of the second face 14 of the membrane 12 and the addition of the groove 35 further allows the reduction of the total volume V of the cavity 15

[0120] The relative variation of the volume (AV / V) of the cavity 15 is amplified, thereby increasing the variation of the gas density in the cavity 15, so that the sensitivity of the pressure sensor 5 is improved.

Claims

Demands

1. Resonant pressure sensor (5) comprising: - a support (6) having a base (7) surrounded by at least one wall (8, 9, 10, 11), - a deformable membrane (12) having a first face (13) configured to be subjected to the pressure to be measured and a second face (14) opposite the first face, the second face being connected to the support so that the support and the deformable membrane form a hermetic cavity (15), the cavity being filled with a predetermined quantity of gas, characterized in that the hermetic cavity (15) comprises: - a temperature sensor (17) separate from the deformable membrane and configured to measure the temperature of the gas, and - a first beam (16) separate from the deformable membrane and having a first end (18) embedded in the wall and a second end (19) free, the first beam being configured to measure the density of the gas.

2. Sensor according to claim 1, wherein the width (Li6) of the first beam (16) is greater than the length (116) of the first beam.

3. Sensor according to claim 2, wherein the first beam (16) is of rectangular, trapezoidal or triangular geometry.

4. Sensor according to claim 2, wherein the first beam is T-shaped or M-shaped.

5. Sensor according to claim 3, comprising piezoresistive gauges arranged between the wall and the first end of the first beam to measure a displacement of the first beam.

6. Sensor according to any one of claims 1 to 5, wherein the temperature sensor (17) comprises a second beam (17a) separated from the deformable membrane (12) and comprising a first end (20) embedded in the wall (8) and a second free end (21), the second beam being configured to measure the temperature of the gas.

7. Sensor according to claim 6, wherein the length (li7) of the second beam (17a) is greater than the width (Lp) of the second beam.

8. Sensor according to any one of claims 1 to 7, wherein the deformable membrane (12) includes a groove (35) opening onto the second face (14), the groove being disposed on the periphery of the deformable membrane in the hermetic cavity (15).

9. Pressure measurement system (4) comprising: - a pressure sensor (5) resonating according to any one of claims 1 to 8, - measuring means (30) configured to measure the resonance frequency of the first beam (16), - first determining means (31) configured to determine the value of the density of the gas in the hermetically sealed cavity (15) from the resonance frequency delivered by the measuring means (30), and - second determining means (32) configured to determine the pressure applied to the first face (13) of the deformable membrane (12) from the value of the density of the gas and the value of the temperature of the gas delivered by the temperature sensor (17).

10. Aircraft (1) comprising a resonant pressure sensor (5) according to any one of claims 1 to 8 or a pressure measuring system (4) according to claim 9.