CN-122029405-A - Sensor, in particular capacitive sensor for a flying chassis

Abstract

The invention relates to a sensor (1) capable of allowing measurement of the dielectric constant of a medium, in particular fuel in a tank, comprising-a support (3), -an insulating fastening element (17), -a plurality of plates (7) comprising at least a first plate (7 a) and a second plate (7 b) aligned parallel and along a stacking axis (X), -at least one first support column (11) connecting the first plate (7 a) to one of the insulating fastening elements (17), -at least one second support column (13) connecting the second plate (7 b) to one of the insulating fastening elements (17), -at least one supplementary plate (7 c), and-at least one spacer column (15) connecting the supplementary plate to a second proximal plate. The support (3) and the plate (7) are made of the same first metallic material, and the spacer posts (15) are made of a second metallic material.

Inventors

• Sylvan Hauserley
• Gilles Delatrey

Assignees

• 赛峰航空系统公司

Dates

Publication Date

20260512

Application Date

20240819

Priority Date

20230821

Claims (9)

1. 1. Sensor (1), in particular capacitive sensor (1), capable of measuring the dielectric constant (ɛ) of a medium, in particular of a fuel contained in a case of an aircraft, comprising: -a support (3), A plurality of insulating fastening elements (17) fixed to the support (3), A plurality of plates (7), comprising at least a first plate (7 a) and a second plate (7 b), which extend substantially parallel to the support (3) and are aligned along a stacking axis (X) perpendicular to the support (3), At least one first support column (11) having a first length (L 1 ) and connecting the first plate (7 a) to one of the insulating fastening elements (17), At least one second support column (13) having a second length (L 2 ) greater than the first length (L 1 ) and connecting the second plate (7 b) to one of the insulating fastening elements (17), -At least one supplementary plate (7 c, 7d, 7 e), and At least one spacer column (15) having a third length (L 3 ) and connecting the complementary plate (7 c, 7d, 7 e) to a plate of the plurality of plates (7) which is second closest to the complementary plate (7 c, 7d, 7 e) in the direction of the support (3) along the stacking axis (X), Characterized in that the support (3) and the plate (7) are made of the same first metallic material and the spacer posts (15) are made of a second metallic material.
2. 2. Capacitive sensor (1) according to claim 1, characterized in that the second coefficient of thermal expansion (α 2 ) of the second metallic material is substantially equal to twice the first coefficient of thermal expansion (α 1 ) of the first metallic material.
3. 3. Sensor (1) according to any one of the preceding claims, characterized in that the insulating fastening element (17) is made of a polymeric material, in particular polyetheretherketone, in particular comprising glass fibers, in particular at least 25% glass fibers.
4. 4. The sensor (1) according to any one of the preceding claims, characterized in that the first support column (11) is made of a third metallic material and/or the second support column (13) is made of a fourth metallic material.
5. 5. The sensor (1) according to claim 4, characterized in that the plurality of plates (7) comprises an even number of plates (7).
6. 6. Sensor (1) according to claim 5, characterized in that the second and third metallic material, and in particular the fourth metallic material, are identical.
7. 7. The sensor (1) according to any one of claims 1 to 4, characterized in that the plurality of plates (7) comprises an odd number of plates (7), in particular three or five plates (7).
8. 8. The sensor (1) according to any of the preceding claims, characterized in that it comprises the same number of first support columns (11), second support columns (13) and spacer columns (15).
9. 9. Aircraft fuel tank comprising a sensor (1) according to any of the preceding claims.

Description

Sensor, in particular capacitive sensor for a flying chassis Technical Field The present invention relates to a sensor, in particular a capacitive sensor, capable of measuring the dielectric constant of a medium, in particular fuel in an aircraft tank, and an assembly comprising such a capacitive sensor. Background Knowing the amount of fuel contained in an aircraft case is important during flight. Therefore, it is necessary to be able to monitor the quantity and density of fuel in the tank in real time during flight with high accuracy. For this purpose, it is common practice to install suitable sensors, such as fuel gauges, in the tank. These sensors are typically capacitive and measure the change in capacitance between two plates extending into the tank and separated by a gap into which fuel enters. Recall that in the case of a parallel plate capacitor comprising two parallel plates of the same area a, separated by a distance d and immersed in a medium of dielectric constant ɛ, the measured capacitance C is given by the formulaWherein ɛ 0 is the dielectric constant of vacuum. The meter is integrated into a multi-sensor system for measuring the amount of fuel in the tank, providing redundancy and drift correction measurements to improve the accuracy and reliability of the measurements. In particular, one measurement aimed at improving the accuracy of such capacitive sensors is the measurement of the dielectric constant of the fuel, carried out by a self-capacitive sensor placed close to the bottom of the tank, also denoted by the abbreviation "CIC", representing a "capacitance index compensator" ("CAPACITANCE INDEX COMPENSATOR"). Such sensors comprise flat metal plates arranged parallel to each other, fixed to a support and assembled together by spacers of known length to form a precise gap. However, such sensors are prone to expansion over a wide operating temperature range, operating conditions typically between-55 ℃ and 65 ℃, disrupting parallelism of the plates and regularity of the gaps, leading to non-linearities and measurement errors. This expansion is particularly prevalent when the plate and the support are made of materials having very different coefficients of thermal expansion, particularly for supports made of plastic. Disclosure of Invention The present invention aims to overcome these drawbacks by enabling the measurement of the dielectric constant of fuel in an aircraft tank with a predictable and controlled drift over a wide temperature range. To this end, the invention relates to a sensor, in particular a capacitive sensor, capable of measuring the dielectric constant of a medium, in particular a fuel contained in an aircraft tank, comprising: the support element is provided with a support element, A plurality of insulating fastening elements fixed to the support, A plurality of plates including at least a first plate and a second plate extending substantially parallel to the support and aligned along a stacking axis perpendicular to the support, At least one first support column having a first length and connecting the first plate to one of the insulating fastening elements, At least one second support column having a second length greater than the first length and connecting the second plate to one of the insulating fastening elements, At least one supplementary plate, and At least one spacer column having a third length and connecting the supplementary plate to a plate of the plurality of plates which is second closest to the supplementary plate in the direction of the support along the stacking axis, Characterized in that the support and the plate are made of the same first metal material and the spacer posts are made of a second metal material. The first metal material may have a first coefficient of thermal expansion. The second metal material may have a second coefficient of thermal expansion. The coefficient of thermal expansion of the material, denoted α, is a linear coefficient for determining the change in length Δl of the material in each dimension relative to a reference length L 0 at a reference temperature as a function of the temperature change Δt relative to said reference temperature, such that. For isotropic materials, the coefficient is the same in all directions, which is the case for the materials considered here. Thus, in the sensor of the invention, the plates forming the capacitance measuring electrodes as well as the support will be temperature modified in all directions according to the same coefficients. Since the variation value is small, a linear approximation of the variation of the surface area of the opposite plate can be made, which varies with temperature according to the coefficient 2α. The use of the same second material for the spacer columns will ensure that thermal expansion in the direction perpendicular to the plates maintains parallelism of the plates relative to each other. The gap then changes according to the same law of expansion, the coeffi