Leak detection device comprising a reference structure provided with a heat storage and release material

Abstract

A leak detection device, in particular for controlling the tightness of an electric battery, for example a traction battery, of a motor car, comprising a reference structure (4) provided with a heat storage and release material (21) in the form of elements of the ball and / or foam type.

Description

[0001] Description

[0002] Title: Leak detection device comprising a reference structure provided with a thermal storage and restitution material

[0003] Technical field

[0004] The invention relates to the field of leak detection, or leak testing, of a mechanical and / or electronic object or equipment.

[0005] The invention is of particular, non-limiting interest in controlling the sealing of an object such as an electric traction battery of a motor vehicle.

[0006] State of the prior art

[0007] Leak detection can be carried out by measuring a physical quantity representative of a leak level, in particular by measuring a variation in pressure or a flow rate within a cavity formed by the object to be tested, or constituted by an enclosure receiving the object to be tested.

[0008] Thus, a classic technique consists of comparing the pressure variation in such a cavity with the pressure variation within a reference cavity in which the pressure is assumed to be stable.

[0009] Generally, when the leak level to be detected is low relative to the volume of the object to be tested, environmental parameters such as pressure and / or temperature variations in the test environment are likely to distort the measurement.

[0010] This problem arises in particular when the object to be tested is an electric battery, for example a traction battery, for a motor vehicle, such a battery typically having internal volumes that can exceed one hundred liters.

[0011] Statement of the invention

[0012] The invention aims to provide a device for reliably and precisely checking the leaktightness of an object such as an electric battery, for example a traction battery, for a motor vehicle. A particular aim of the invention is to provide a compact leak detection device.

[0013] To this end, the invention relates to a leak detection device, comprising:

[0014] - a measuring device for a physical quantity representative of a pressure (or a flow rate),

[0015] - a reference structure which comprises at least one enclosure forming a so-called reference cavity,

[0016] - a fluidic system configured to establish fluidic communication on the one hand between the measuring member and said reference cavity and, on the other hand, between the measuring member and a so-called test cavity formed by, or extending around, an element to be tested such as an electric battery, for example a traction battery, for a motor vehicle.

[0017] The device is configured to allow the measuring member to measure a pressure difference, or a physical quantity representative of a pressure or a flow rate, between said reference cavity and said test cavity.

[0018] According to the invention, the reference structure comprises a thermal storage and restitution material arranged in said reference cavity, and / or around said reference cavity in a secondary cavity of said at least one enclosure, in order to increase the thermal inertia of the reference structure.

[0019] This thermal inertia material, which in other words is a material capable of storing and releasing heat, acts as a true temperature regulator within or around the reference cavity.

[0020] The invention thus makes it possible to increase the thermal inertia or the thermal capacity of the reference structure and, consequently, to reduce, during measurement, the temperature variations in said reference cavity despite potential temperature variations in the environment of the leak detection device.

[0021] The invention makes it possible in particular to reduce the size of the reference cavity and therefore the size of the leak detection device. According to one embodiment, a thermal homogenization material is arranged in said reference cavity.

[0022] The reference cavity can therefore comprise both a thermal storage and restitution material and a thermal homogenization material, only a thermal storage and restitution material or only a thermal homogenization material.

[0023] Without limitation, the thermal homogenization material may comprise a foam, for example a metal foam.

[0024] This type of material is porous and contains a large portion of void space, which optimizes thermal homogeneity within the said reference cavity.

[0025] According to a first variant embodiment, said thermal storage and restitution material comprises a plurality of sub-elements.

[0026] The sub-elements forming the thermal storage and restitution material are, for example, distinct, and can be in the form of balls, i.e. have a spherical, or substantially spherical, geometry, making it possible to optimize their surface-volume ratio and / or to easily adapt to different types of situation.

[0027] Of course, these sub-elements can have different geometry, for example ovoid or polygonal or other.

[0028] Without limitation, such sub-elements may be made of steel, metal or a metal alloy.

[0029] For information purposes, the said sub-elements may have a surface-volume ratio less than or equal to 4 cm -1 , preferably less than or equal to 7 cm, preferably less than or equal to 15 cm 4 .

[0030] Alternatively or additionally, the sub-elements forming the thermal storage and restitution material may comprise metal particles. The variants described above may be combined. Thus, in a non-limiting manner, said thermal storage and restitution material may comprise both sub-elements such as beads and metal particles.

[0031] According to one embodiment, said thermal storage and restitution material has a thermal capacity greater than or equal to 50 JK -1 , preferably greater than or equal to 200 JK -1 , preferably greater than or equal to 1000 JK -1 , more preferably greater than or equal to 5000 JK -1 .

[0032] According to one embodiment, said thermal storage and restitution material is advantageously incompressible, in particular in order to prevent a variation in volume of the thermal storage and restitution material from resulting in a change in pressure in the reference cavity, at least when the thermal storage and restitution material is contained entirely or partly in the reference cavity.

[0033] According to one embodiment, said thermal storage and restitution material occupies a volume of between 10% and 100% of said reference cavity and / or of said secondary cavity.

[0034] When said thermal storage and restitution material, or a part thereof, is arranged in said reference cavity, said thermal storage and restitution material may occupy a volume of between 30% and 70%, more preferably between 40% and 60%, for example 50% of said reference cavity.

[0035] When said thermal storage and restitution material, or a portion thereof, is arranged in said secondary cavity, said thermal storage and restitution material may occupy a volume greater than 50%, preferably greater than 70%, more preferably greater than 80% of said secondary cavity.

[0036] According to one embodiment, said at least one enclosure comprises an internal enclosure forming said reference cavity and an external enclosure receiving the internal enclosure such that the internal enclosure and the external enclosure form between them said secondary cavity. According to this embodiment, said thermal storage and restitution material may be contained only in said secondary cavity, or only in said reference cavity, or both in said secondary cavity and in said reference cavity.

[0037] Said internal enclosure may comprise a material such as an aluminum alloy, allowing it not to deform when the reference cavity which it forms is put under pressure.

[0038] According to one embodiment, said at least one enclosure, for example said external enclosure when said at least one enclosure comprises an internal enclosure and an external enclosure, comprises walls delimiting between them one or more chambers containing a gas such as air.

[0039] In other words, said at least one enclosure, or at least one of the enclosures when the reference structure comprises several, perhaps double-walled with an air vacuum.

[0040] According to one embodiment, said at least one enclosure, for example said external enclosure when the at least one enclosure comprises an internal enclosure and an external enclosure, comprises polystyrene.

[0041] Such an enclosure, comprising air and / or polystyrene, makes it possible to improve the thermal properties of the reference structure.

[0042] For information purposes, said at least one enclosure, for example said external enclosure when the at least one enclosure comprises an internal enclosure and an external enclosure, may have a thermal conductivity less than or equal to 0.05 Wm -1 -K -1 , preferably less than or equal to 0.03 Wm -1 -K -1 , preferably less than or equal to 0.02 Wm -1 -K -1 , more preferably less than or equal to 0.01 Wm -1 -K -1 .

[0043] Said at least one enclosure, for example said external enclosure when said at least one enclosure comprises an internal enclosure and an external enclosure, may have a thermal resistance greater than or equal to 1 KW -1 , preferably greater than or equal to 2 KW -1 , preferably greater than or equal to 5 KW -1 , more preferably greater than or equal to 10 KW -1. According to an alternative embodiment, the measuring member comprises a differential pressure sensor.

[0044] According to another embodiment, the measuring device comprises two absolute pressure sensors.

[0045] Of course, the measuring device may comprise one or more differential pressure sensors and / or one or more absolute pressure sensors.

[0046] According to another aspect of the invention, the invention relates to a method for detecting leaks using a leak detection device as defined above.

[0047] The method preferably comprises a step of measuring, using said measuring member, a pressure difference between said reference cavity and a cavity formed by, or extending around, an element to be tested, such as an electric battery, for example a traction battery, for a motor vehicle.

[0048] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

[0049] Brief description of the drawings

[0050] The following detailed description refers to the attached drawings in which:

[0051] - [Fig. 1] is a schematic view of a leak detection device according to the invention;

[0052] - [Fig. 2] is a schematic view of a structure according to a first embodiment of the invention, this structure forming a reference cavity for a leak detection device;

[0053] - [Fig. 3] is a schematic view of a structure according to a second embodiment of the invention, this structure forming a reference cavity for a leak detection device.

[0054] Detailed description of embodiments

[0055] [Fig. 1] schematically represents a device 1 according to the invention, intended to check the tightness of an object 2, also called “element to be tested”. In this example, the element to be tested 2 is an electric battery, for example a traction battery, for a motor vehicle or any other element which may have a volume greater than around ten litres.

[0056] The device 1 of [Fig. 1] comprises a measuring member 3, a reference structure 4, an enclosure 5 and a fluidic system 6.

[0057] The enclosure 5 forms a cavity 11, called a “test cavity”, receiving in this example the element to be tested 2.

[0058] With reference to [Fig. 2], the reference structure 4 comprises in this example an internal enclosure 14 and an external enclosure 15.

[0059] In a non-limiting manner, the enclosures 14 and 15 both have a substantially tubular or cylindrical geometry.

[0060] The internal enclosure 14 comprises a side wall 14A extending around an axis A1 and two end walls 14B and 14C spaced apart from each other along the axis A1.

[0061] The internal enclosure 14 forms a cavity 16, called the “reference cavity”, delimited radially by the wall 14A and axially by the walls 14B and 14C.

[0062] In this example, walls 14A-14C are made of aluminum.

[0063] Concerning the external enclosure 15, this comprises in this example side walls 15A and 15B extending concentrically around the axis A1 and three end walls 15C, 15D and 15E spaced from each other along the axis A1.

[0064] In this example, walls 15A, 15B, 15D and 15E are stainless steel and wall 15C is plastic.

[0065] The walls 15A and 15E together form an inner wall of the enclosure 15. The walls 15B and 15D together form an outer wall of the enclosure 15.

[0066] The inner and outer walls of the external enclosure 15 delimit between them a chamber 17 receiving a gas such as air.

[0067] The internal enclosure 14 is housed in the external enclosure 15 so as to form a cavity 20, called a “secondary cavity”, delimited on the one hand by the internal enclosure 14 and, on the other hand, by the external enclosure 15. Said cavity 20 has, for example, a volume of between 200 and 800 cubic centimeters, and preferably between 400 and 600 cubic centimeters.

[0068] In this example, the cavity 20 extends radially between the side wall 14A of the inner enclosure 14 and the side wall 15A of the outer enclosure 15. The cavity 20 also extends axially between the wall 14B of the inner enclosure 14 and the wall 15C of the outer enclosure 15. The cavity 20 also extends axially between the wall 14C of the inner enclosure 14 and the wall 15E of the outer enclosure 15.

[0069] The gas and in particular air has good thermal insulation properties, so that the external enclosure 15 can thus have a low thermal conductivity, in particular less than or equal to 0.05 Wm -1 -K -1 , preferably less than or equal to 0.03 Wm -1 -K -1 , more preferably less than or equal to 0.02 Wm -1 -K -1 , even more preferably less than or equal to 0.01 Wm _1 -K 1 .

[0070] In this example, the external enclosure 15 can thus have a thermal resistance greater than or equal to 1 KW. -1 , preferably greater than or equal to 2 KW -1 , preferably greater than or equal to 5 KW -1 , more preferably greater than or equal to 10 KW -1 .

[0071] Such thermal properties can be obtained using an enclosure different from that of [Fig. 2]. Thus, in an alternative embodiment, not shown, the external enclosure 15 comprises polystyrene or a thermally similar material. Such a material can typically be enclosed between reinforcing or protective walls, for example made of aluminum.

[0072] With reference to [Fig. 2], the reference structure 4 comprises a material 21 arranged in the cavity 20, so as to increase the thermal inertia of the structure 4. The material 21 is thus a thermal storage and restitution material, otherwise called a thermal restitution material.

[0073] In a non-limiting manner, the material 21 comprises steel balls, which in this example occupy a volume corresponding substantially to the total volume of the cavity 20. Of course, the quantity and / or the geometry and / or the material from which the material 21 is made can be adapted according to the required or desired thermal inertia, taking into account the particular structure of the reference structure 4 and more generally of the device 1, as well as the conditions in which the measurement is carried out.

[0074] Thus, the material 21 can occupy a volume less than the total volume of the cavity 20, for example a volume of approximately 80% of the cavity 20.

[0075] Furthermore, the material 21 may comprise, alternatively or additionally, a metal foam and / or sub-elements such as metal particles.

[0076] Generally, it is preferred that the sub-elements forming the material 21, for example the aforementioned balls, have a surface-volume ratio less than or equal to 4 cm -1 , preferably less than or equal to 7 cm -1 , preferably less than or equal to 15 cm 4 .

[0077] The material 21 is preferably incompressible, at least capable of maintaining a substantially constant volume during the measurement under the action of variations in pressure and / or temperature in the cavity 20.

[0078] In this example, material 21 has a heat capacity greater than or equal to 50 JK -1 , preferably greater than or equal to 200 JK -1 , preferably greater than or equal to 1000 JK -1 , more preferably greater than or equal to 5000 JK -1 .

[0079] In this example, material 21 has a thermal resistance greater than or equal to 0.1 KW -1 , preferably greater than or equal to 0.5 KW -1 , preferably greater than or equal to 1 KW -1 , more preferably greater than or equal to 5 KW -1 .

[0080] In this example, a thermal homogenization material 22 is placed in the internal enclosure 14 forming the reference cavity 16. This material 22 ensures accelerated thermal diffusion and homogeneity within the enclosures 14 and 15 so as to further increase the thermal inertia of the structure 4.

[0081] In a non-limiting manner, this material 22 may also be arranged in the external enclosure 15 in addition to the material 22. In a non-limiting manner, the thermal homogenization material 22 comprises a foam, for example a metal foam. It could be another porous material.

[0082] The thermal homogenization material 22 may additionally comprise metal particles and / or steel balls whose diameter is preferably smaller than the diameter of the steel balls of the material 21. The walls of the internal enclosure 14 may act as a thermal storage (and restitution) material, by varying its thickness and the type of material which constitutes its walls.

[0083] [Fig. 3] schematically shows an alternative embodiment of the reference structure 4, which differs from that of [Fig. 2] in that it does not include an internal enclosure 14. [Fig. 3] is described below only according to its differences from [Fig. 2], the description of which applies by analogy.

[0084] In the embodiment of [Fig. 3], the single enclosure 15 is similar to the external enclosure 15 of the structure 4 of [Fig. 2], The cavity 16 formed by the enclosure 15 of the structure 4 of [Fig. 3] forms said reference cavity.

[0085] Thus, the volume of the reference cavity 16 of the structure 4 of [Fig. 3] corresponds substantially to the addition of the volume of the cavity 20 and of the internal enclosure 14 of the structure 4 of [Fig. 2],

[0086] In the example of [Fig. 3], the thermal storage and restitution material 21 is arranged in the reference cavity 16 so as to occupy a volume of approximately 50% of the cavity 20.

[0087] Of course, the volume occupied by the material 21 may be different from this value and be, for example, located in a range between 40% and 60%, or between 30% and 70%, or even between 10% and 90% of the cavity 20.

[0088] In a non-limiting manner, a thermal homogenization material 22 may be arranged in the reference cavity 16 in addition to the thermal storage and restitution material 21. This material 22 ensures rapid thermal homogeneity within the reference cavity 16 so as to further increase the thermal inertia of the structure 4.

[0089] Without limitation, the thermal homogenization material 22 comprises a foam, for example a metal foam. It could be another porous material.

[0090] The thermal homogenization material 22 may additionally comprise metal particles and / or steel balls whose diameter is preferably smaller than the diameter of the steel balls of the material 21.

[0091] The device 1 of [Fig. 1] may comprise a reference structure similar to any of the embodiments of [Fig. 2] and [Fig. 3] and their variants. As a non-limiting example of a variant, the enclosure(s) of the structure 4 may have a section that is not circular as in the examples of [Fig. 2] and [Fig. 3], but a polygonal section, for example a square section.

[0092] With reference to [Fig. 1], the fluidic system 6 is in this example an aeraulic system comprising, in a non-limiting manner, a compressed air supply member 31, conduits 32-38 and valves 41-43.

[0093] The fluidic system 6 is configured to be able to inject air on the one hand into the reference cavity 16 and, on the other hand, into the test cavity 11 in which the element to be tested 2 is placed. The fluidic system 6 is connected to the measuring member 3, which in this example comprises a differential pressure sensor.

[0094] More precisely, the conduits 33 and 37 form a first branch of the fluidic system 6, configured to be able to inject air into the reference cavity 16 of the reference structure 4. The conduits 34 and 38 form a second branch of the fluidic system 6, configured to be able to inject air into the test cavity 11.

[0095] The conduits 35 and 36, respectively with the conduits 37 and 38, make it possible to establish fluid communication respectively between the sensor 3 and the reference cavity 16 and between the sensor 3 and the test cavity 11. The device 1 of course comprises elements 50 for the sealed connection of the conduits 37 and 38 respectively to the reference structure 4 and to the enclosure 5.

[0096] In a manner known per se, the valves 41, 42 and 43 can be controlled between open and closed positions by any conventional mechanical and / or electronic means. Typically, the injection of air into the cavities 11 and 16 is carried out by opening the valves 41, 42 and 43. When the pressure in the cavities 11 and 16 reaches a predetermined pressure, and possibly after a predetermined duration allowing stabilization of aeraulic parameters such as pressure and / or temperature, the valve 41 can be closed and the valves 42 and 43 kept open in order to carry out the measurement, in this example a measurement of pressure variation between the test cavity 11 and the reference cavity 16 using the sensor 3.

[0097] The device 1 thus makes it possible to check the tightness of the element to be tested 2, thus forming a leak detection device.

[0098] Of course, many variations can be implemented based on the embodiments described above and their variations.

[0099] For example, the test cavity may consist of an internal volume of the element to be tested 2 and not an external volume such as constituted by the cavity 11 of the enclosure 5 in the example of [Fig. 1]. When the test cavity is an internal volume of the element to be tested 2, the latter may nevertheless be arranged in a thermal insulation enclosure (not shown) in order to reduce environmental influences during the measurement, taking into account possible temperature variations which are typically likely to occur in an industrial environment. Such a thermal insulation enclosure, which may also receive the reference structure 4 and / or the measuring member 3 within the same cavity or several separate cavities, is preferably configured to have a relatively low thermal conductivity and a relatively high thermal resistance.For information purposes, the thermal insulation enclosure may have a thermal conductivity less than or equal to 0.05 Wm ^-K', preferably less than or equal to 0.03 Wm. -1 -K -1 , preferably less than or equal to 0.02 Wm -1 -K -1 , more preferably less than or equal to 0.01 Wm -1 -K -1 , and a thermal resistance greater than or equal to 1 KW ~ 1 , preferably greater than or equal to 2 KW -1 , preferably greater than or equal to 5 KW -1 , more preferably greater than or equal to 10 KW -1 .

[0100] When using such a thermal insulation enclosure, the leak detection device may comprise a ventilation system (not shown) configured to circulate a gas such as air in one or more cavities of the enclosure receiving the element to be tested 2 and / or the reference structure 4 and / or the measuring member 3.

[0101] In the embodiment of [Fig. 1], the measuring member 3 is a differential pressure sensor. Alternatively, the measuring member 3 may comprise two absolute pressure sensors which are each configured to measure the pressure of a respective one of the test cavity and the reference cavity.

[0102] Furthermore, the invention can be implemented to check the tightness of an object other than a battery, for example an electronic device, and preferably objects having volumes that can exceed several tens of liters, or even a few hundred liters, and test times greater than 60 minutes. Indeed, the time constant greater than or equal to 3 hours, preferably greater than or equal to 100, preferably greater than or equal to 5 KW -1 , more preferably greater than or equal to 20 hours.

Claims

Claims 1. Leak detection device (1), comprising: - a measuring device (3), - a reference structure (4) which comprises at least one enclosure (14, 15) forming a so-called reference cavity (16), - a fluidic system (6) configured to establish a fluidic communication on the one hand between the measuring member (3) and said reference cavity (16) and, on the other hand, between the measuring member (3) and a so-called test cavity (11) formed by, or extending around, an element to be tested (2) such as an electric battery for a motor vehicle, the leak detection device (1) being configured to allow the measuring member (3) to measure a pressure difference, or a physical quantity representative of a pressure or flow rate, between said reference cavity (16) and said test cavity (11) and being characterized in that the reference structure (4) comprises a thermal storage and restitution material (21) arranged in said reference cavity (16) and / or in a secondary cavity (20) of the at least one enclosure (14, 15), in order to increase the thermal inertia of the reference structure (4).

2. Leak detection device (1) according to claim 1, wherein a thermal homogenizing material is disposed in said reference cavity (16).

3. A leak detection device (1) according to claim 2, wherein the thermal homogenizing material comprises a foam, for example a metal foam.

4. Leak detection device (1) according to any one of claims 1 to 3, wherein said thermal storage and restitution material (21) comprises a plurality of sub-elements, such as beads and / or metal particles, and / or a foam.

5. Leak detection device (1) according to claim 4, wherein said sub-elements have a surface-to-volume ratio less than or equal to 4 cm -1 , of preferably less than or equal to 7 cm, preferably less than or equal to xx cm 4 , more preferably less than or equal to 15 cm4 .

6. Leak detection device (1) according to any one of claims 1 to 5, wherein said thermal storage and restitution material (21) has: - a thermal capacity greater than or equal to 50 JK -1 , preferably greater than or equal to 200 JK 1 , preferably greater than or equal to 1000 JK 1 , more preferably greater than or equal to 5000 JK -1 .

7. Leak detection device (1) according to any one of claims 1 to 6, wherein said thermal storage and restitution material (21) is incompressible.

8. Leak detection device (1) according to any one of claims 1 to 7, wherein said thermal storage and restitution material (21) occupies a volume of between 10% and 100% of said reference cavity (16) and / or of said secondary cavity (20), for example a volume of between 30% and 70%, more preferably between 40% and 60%, for example 50% of said reference cavity (16), for example a volume greater than 50%, preferably greater than 70%, more preferably greater than 80% of said secondary cavity (20).

9. Leak detection device (1) according to any one of claims 1 to 8, wherein the at least one enclosure (14, 15) comprises an internal enclosure (14) forming said reference cavity (16) and an external enclosure (15) receiving the internal enclosure (14) so ​​that the internal enclosure (14) and the external enclosure (15) form between them said secondary cavity (20).

10. Leak detection device (1) according to any one of claims 1 to 9, in which the at least one enclosure (15) comprises walls (15A, 15B, 15D, 15E) delimiting between them one or more chambers (17) containing a gas such as air.

11. Leak detection device (1) according to any one of claims 1 to 10, wherein the at least one enclosure (15) comprises polystyrene.

12. Leak detection device (1) according to any one of claims 1 to 11, wherein the at least one enclosure (15) has: - a thermal conductivity less than or equal to 0.05 Wm -1 -K -1 , preferably less than or equal to 0.03 Wm -1 -K -1 , preferably less than or equal to 0.02 Wm -1 -K -1 , more preferably less than or equal to 0.01 Wm -1 -K -1 , and / or - a thermal resistance greater than or equal to 1 KW-1 , preferably greater than or equal to 2 KW -1 , preferably greater than or equal to 5 KW -1 , more preferably greater than or equal to 10 KW -1 .

13. Leak detection device (1) according to any one of claims 1 to 12, wherein the measuring member (3) comprises a differential pressure sensor and / or two absolute pressure sensors.

14. Method for detecting a leak using a leak detection device (1) according to any one of claims 1 to 12, comprising a step of measuring, using said measuring member (3), a pressure difference between said reference cavity (16) and a cavity (11) formed by, or extending around, an element to be tested (2) such as an electric battery for a motor vehicle.

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