Leak detection method and system

Abstract

The present invention relates to a leak detection system (1) for checking the leak tightness of an object, said system (1) comprising: - means (5) for pressurizing a space; - a first pressure sensor (7) configured to measure a pressure variation in said pressurized space; - a second pressure sensor (9) configured to measure a variation of the ambient pressure, for example of the atmospheric pressure; - an electronic entity (15) configured to determine a leak F', F" depending on said pressure variation ΔP in said pressurized space and on said ambient pressure variation AP ext determined leak F', F" from said pressure variation ΔP in said pressurized space and from said ambient pressure variation AP ext measured by said first sensor (7) and second sensor (9) respectively over a predetermined test time interval W.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of leak detection systems and methods for checking the tightness of an object, more particularly based on the measurement of a physical quantity related to the level of leak.

[0002] Various systems and methods exist for detecting leaks, but in this case, the present invention more particularly relates to leak detection by pressure variation. BACKGROUND

[0003] When it is necessary to detect leaks by pressure variation, the object to be tested, whose tightness level is to be checked, is subjected to a controlled pressure variation, that is to say, a known pressure variation is applied to the internal space of the object (called direct method) or to the closed space surrounding said object (called indirect method). Subsequently, after a certain time, the pressure in the space that has undergone said pressure variation is measured again. If the object has a leak, the measured pressure is different from the initial pressure.

[0004] The pressure variation is generally measured over a given time, to allow the determination of the level of leak related to the object. Indeed, the pressure variation per unit of time can be related to the level of leak by the following mathematical relationship:

[0005]

[0006] where F is the leak, generally expressed in cubic centimeters per minute (or cm 3 / min), ΔΡ is the pressure variation measured in the space (in Pascals (Pa)), Δt is the time interval over which the pressure variation ΔΡ is measured (in seconds), V is the related space to be considered (for example the internal space of the object), generally expressed in cubic centimeters (cm 3 ), and k is a multiplication constant (in Pa -1 ).

[0007] Thus, whatever the object or sub-element of the object, it is possible to check whether the object leaks and to determine its level of tightness.

[0008] The object to be tested can be an electronic device, a package, a container, etc. Thus, the tolerance of the level of tightness can be highly variable with respect to the object to be tested, its space, its shape, its function, etc.

[0009] However, when the level of leak to be determined is relatively small compared to the space of the object to be tested, the environmental parameters can make it difficult to measure the pressure variation and / or its repeatability.

[0010] In practice, the values of the pressure variations related to the leak subsequently have an order of magnitude close to the pressure variations of the environment, generally atmospheric pressure, so it is particularly difficult to obtain reliable leak measurement values and to distinguish the pressure variations related to the leak from the variations related to the environment.

[0011] This problem is even more pronounced when the leak detection is performed in a factory, i.e. in an industrial environment where the temperature and the pressure can vary locally and / or over time, depending on the operations performed on the object to be tested or in the vicinity of the leak detection system. SUMMARY

[0012] The present invention finds advantageous application in the field of leak detection of batteries of electric vehicles of automobiles and in the field of leak detection of any object having similar problems.

[0013] In practice, the batteries of automobiles are therefore generally composed of several modules housed in a casing equipped with a cooling system, an electronic management card, etc.

[0014] A battery of this type can have a large volume, of the order of 100 to 150 liters (or cubic decimeters), and must meet strict sealing standards, since the presence of water in such an object can be catastrophic. The level of leak of the battery must therefore be very small, so as to check this leak at an order of magnitude close to the temperature variations and / or the pressure of the environment of the battery. In addition, the battery is subjected to electrical and mechanical tests before it is installed in the vehicle. The battery is therefore subjected to thermal and mechanical stresses that can affect the subsequent sealing checks.

[0015] The patent holder has therefore carried out research and tests to provide a leak detection method and system having improved sensitivity and capable of achieving better repeatability in leak detection, while increasing the level of detectability of the leak.

[0016] The present invention is therefore a new leak detection system for checking the sealing of an object, the system comprising:

[0017] - means for pressurizing the space;

[0018] - a first pressure sensor configured to measure the pressure variations in the pressurized space; and

[0019] - a second pressure sensor configured to measure the pressure variations of the environment, for example atmospheric pressure; and

[0020] - an electronic entity configured to determine a leak F', F" depending on the pressure variations ΔP and ΔP ext of the pressurized space and of the environment, respectively, measured by the first and second sensors in a predetermined test time interval t ext respectively by the first and second sensors in a predetermined test time interval ttest internal measurement.

[0021] According to a possible feature, the pressure variation AP of the environment is measured by a third pressure sensor. ext correcting the pressure variation AP in the space.

[0022] The correction of the pressure variation of the space makes it possible to obtain a leak value close to the real value of the leak of the object under test.

[0023] According to another possible feature, the first and / or second pressure sensor is a differential pressure sensor.

[0024] The use of a differential pressure sensor has the advantage of being able to measure smaller pressure variations and of eliminating measurement errors related to the mechanical and / or thermal behavior of the object under test.

[0025] According to another possible feature, the electronic entity and the first and second sensors make it possible to generate, during a test time interval t test internally:

[0026] - a curve of the pressure variation AP in the space;

[0027] - a curve of the pressure variation AP of the environment. ext

[0028] According to another possible feature, the electronic entity (15) determines a leak level F' of the object under test based on the corrected pressure variation AP', the corrected pressure variation AP' being calculated as follows:

[0029] F' = C1AP' = C1(AP - k S AP ext )

[0030] where k S is a normalization coefficient specific to the first and second sensors and C1 is a constant depending on the time and space of the object under test.

[0031] According to another possible feature, the normalization coefficient k ext is determined based on the curve of the pressure variation AP in the space and the curve of the pressure variation AP of the environment, or before the measurement of the pressure variation AP in the space and the measurement of the pressure variation AP of the environment ext , the value of the normalization coefficient k S being stored in the memory of the electronic entity. S

[0032] According to another possible feature, the system comprises a third pressure sensor configured to measure the pressure in the pressurized space.

[0033] According to one aspect, the third sensor can for example be an absolute pressure sensor.​​

[0034] According to another possible feature, the electronic entity determines, via at least one sensor, an average temperature variation of the object per unit of time, said average temperature variation also being used to determine the leak depending on the pressure variation in the pressurized space and the pressure variation of the environment.

[0035] Indeed, if the object under test is not in thermal equilibrium with its environment, the fact that it senses or transmits heat modifies the temperature of the space, and thus the pressure in said space.

[0036] According to another possible feature, the electronic entity is configured to determine, via a second or third sensor, an average temperature variation of the pressurized space and / or of the object under test.

[0037] According to another possible feature, the electronic entity determines, via at least one sensor, a pressure variation Δ T P related to the average temperature variation of the object per unit of time, said pressure variation Δ T P also being used to determine the leak F" of the object under test depending on the pressure variation ΔP in the pressurized space and the pressure variation ΔP ext of the environment.

[0038] According to another possible feature, the electronic entity determines the leak level F" of the object under test depending on the following formula:

[0039] F" = C1 ΔP" = C 1( ΔP - k S ΔP ext - Δ T P)

[0040] where ΔP" is the corrected pressure variation of the object under test, Δ T P is the pressure variation depending on the average temperature variation of the object under test during the test time of said object, and C1 is a constant depending on the time and the space of the object under test.

[0041] According to another possible feature, the system comprises a thermally insulated enclosure configured to house the object to be tested.

[0042] According to another possible feature, the thermally insulated enclosure is made of a material having a thermal conductivity coefficient of less than 0.05 W.m -1 .K -1 at 20°C, preferably less than 0.03 W.m -1 .K -1 at 20°C, and even more advantageously less than 0.01 W.m -1 .K -1 at 20°C.

[0043] According to another possible feature, the housing containing the object to be tested includes one or more cavities capable of accommodating the object to be tested and a reference object.

[0044] According to another possible feature, the system includes a ventilation device configured to agitate the gas (preferably inert) or air in the interior space of the housing.

[0045] The ventilation device can in particular prevent hot spots and / or thermal bridges from being generated between the housing and the exterior of the detection device.

[0046] The present invention also relates to a leak detection method for checking the sealing of an object, the method being implemented within a leak detection system (1) and comprising the following steps:

[0047] - Pressurize the space using a pressurization device;

[0048] - The pressure change in the pressurized space is measured using a first pressure sensor;

[0049] -Measure environmental pressure changes using a second sensor;

[0050] Leaks can be identified and detected based on pressure changes in the pressurized space and the ambient pressure. Attached Figure Description

[0051] The invention will be better understood in the following description of specific embodiments of the invention, given by way of illustration only and not limitation, with reference to the accompanying drawings, and other objects, details, features and advantages thereto will become clearer, wherein:

[0052] -referred to as [ Figure 1 ]of Figure 1 This is a highly schematic representation of the leak detection system according to the present invention;

[0053] -referred to as [ Figure 1a ]of Figure 1a yes Figure 1 Schematic diagram and enlarged view of the pressure sensor of the system;

[0054] -referred to as [ Figure 2 ]of Figure 2 This is used to check the sealing of an object when it is used in batteries for electric vehicles. Figure 1 A schematic perspective view of the system;

[0055] -referred to as [ Figure 3 ]of Figure 3 This is a flowchart illustrating the steps of the leakage detection method according to the present invention;

[0056] -referred to as [ Figure 4 ]of Figure 4 Is Figure 3- a graph of the pressure variation in space during the different steps of the method;

[0057] - a graph called [ Figure 5 ] of the pressure variation in space during the different steps of the method; Figure 5 is an example of a graph representing as a curve the pressure variation in space related to the tested object and to the environment during the tightness check of the object;

[0058] - a graph called [ Figure 6 ] of the pressure variation in space during the different steps of the method; Figure 6 is a curve of the pressure variation in space related to the tested object determined from the curve in Figure 5 . DETAILED DESCRIPTION

[0059] Thus, [ Figure 1 ] is a highly schematic representation of a leak detection system for checking the tightness of an object 10, in the example described hereafter the tested object is a battery for a car, but can be any object whose tightness must be checked and whose level of leak to be detected is at the order of magnitude of the disturbances related to the environment of the system.

[0060] Thus, the system comprises:

[0061] - a device 5 for pressurizing the space related to the tested object 10, for example the characteristic space of the battery 10, that is to say, this can be the internal space of the battery (direct method) or the closed space around the battery (indirect method);

[0062] - a first pressure sensor 7 configured to measure the pressure variation of the characteristic space to check the tightness of the battery 10;

[0063] - a second pressure sensor 9 configured to measure the pressure variation of the environment, generally atmospheric pressure;

[0064] - a third pressure sensor 17, which is an optional sensor, said third pressure sensor being configured to measure the pressure applied in the characteristic space by the device 5;

[0065] - an air connection 11 configured to connect the pressurizing device 5 to the object 10 and to the reference 13;

[0066] - an electronic entity 15, for example an electronic circuit, connected to the various pressure sensors 7, 9, 17 and configured to recover the pressure values measured by one or more of the sensors 7, 9 and 17.

[0067] The first pressure sensor 7 and the second pressure sensor 9 are preferably differential pressure sensors. However, the third sensor 17 is advantageously an absolute pressure sensor.

[0068] It should be noted that the differential pressure sensor is, for example, a sensor comprising a diaphragm, each face of which is exposed to the pressure, the displacement of the diaphragm (measured, for example, by a capacitive effect) making it possible to measure the differential pressure of each face of the diaphragm.

[0069] [ Figure 1a ] is a highly diagrammatic view of a second differential pressure sensor 9 configured to measure the pressure variation of an environment, for example atmospheric pressure.

[0070] More particularly, the sensor 9 comprises a diaphragm 201, each face of which is located in a separate cavity 203, 205. Each of the cavities 203, 205 of the sensor 9 is in communication with the outside (in this case, the atmosphere), whereas one of the cavities 205 is configured to filter out rapid pressure variations that can occur in said environment, it is thus possible to define a value P ext and P' ext of the pressure prevailing in each of the cavities 203, 206, the difference of said pressure values providing the pressure variation ΔP ext of the environment.

[0071] Similarly, in the present example, the leak detection is done by means of a reference 13, but the latter can be:

[0072] - a reference piece (that is to say, the same object with the required level of tightness), in which case a measurement of the pressure variation is performed between the test piece and the reference piece;

[0073] - a plug, the pressure variation between the test piece and the reference side plug being measured;

[0074] - another similar object to be tested, thus testing two pieces simultaneously, one on the test side and the other on the reference side.

[0075] More particularly, the device 5 comprises:

[0076] - a compressed air supply 51;

[0077] - an air circuit comprising a plurality of valves 57 and connected on the one hand to the power supply 51 and on the other hand configured to regulate the supply of compressed air to the various parts of the air circuit, that is to say, to at least one of said sensors 7, 17 and / or to at least one characteristic space of the object 10 to be tested and of the reference 13 (via the air connection 11).

[0078] In general, the device 5 and its elements 51, 57, the electronic entity 15 and the various sensors 7, 9 and 17 are arranged inside a housing 20. However, various elements, for example the sensor 9, can be offset and arranged outside the housing 20.

[0079] The electronic entity 15 is also connected to the valve 57 to control the valve 57 during the various steps required for checking the seal of the object 10.

[0080] about[ Figure 2 It is used to check the sealing of battery 10. Figure 1 A schematic perspective view of the system.

[0081] Therefore, the system 1 further includes a housing 30, which includes a base 30a and a cover 30b. The base 30a is configured to house the battery 10 and the cover 30b for covering the battery 10 to limit environmental impact in the event of a leak.

[0082] Therefore, the housing 30 can be made of material with a thermal conductivity of less than 0.05 W / m at 20°C. -1 .K -1 Preferably, the Wm is less than 0.03 Wm at 20°C. -1 .K -1 And even more advantageously, at 20°C, it is less than 0.01 Wm. -1 .K -1 Made of materials.

[0083] In an alternative embodiment not shown, the housing 30 includes one or more cavities capable of accommodating the object to be tested 10 and the reference object 13.

[0084] In another alternative embodiment not shown, system 1 includes a ventilation device configured to agitate the gas (preferably inert) or air within the interior space of housing 30.

[0085] Therefore, as [ Figure 3 As described in the document, when it is necessary to check the sealing of an object 10, such as a battery, the system 1 performs the following method 100:

[0086] -Pressure S1 is applied to the characteristic space of the object 10, such as the internal space of a battery, via the pressurizing device 5;

[0087] - The pressure change S2 of the pressurized space of object 10 is measured by the first pressure sensor 7;

[0088] -Measure the environmental pressure change S3 using the second sensor 9;

[0089] - Depends on the pressure change ΔP in the pressurized space and the pressure change ΔP in the environment (in this case, atmospheric pressure). ext Detect the leak in S4.

[0090] It should be noted that some steps of method 100 are more specific in [ Figure 4This is part of the four-stage air leak detection and management method described in the document:

[0091] - During the stage of filling space I with compressed air, the pressure is increased to the required pressure value P1;

[0092] -Stability Phase II: After pressurizing the space, wait for it to return to thermal and mechanical equilibrium so that the phenomenon does not interfere with the leakage measurement. Note that the filling phase I and stability phase II correspond to pressurization step S1.

[0093] - Test Phase III, during which time, at the scheduled test time t test The pressure changes in the pressurized space and the pressure changes in the environment are measured (therefore, test phase III corresponds to steps S2 and S3 above);

[0094] - Exhaust phase IV, during which the pressurized space returns to atmospheric pressure.

[0095] The various steps and stages described below are controlled by electronic entity 15, which accordingly manages the opening and closing of various valves 57.

[0096] Furthermore, the electronic entity 15 is configured to depend on the pressure change ΔP in the pressurized space and the pressure change ΔP in the environment. ext Determine the leaks F' and F", and the changes ΔP and ΔP ext The first sensor 7 and the second sensor 9 respectively operate at a predetermined time interval t. test Internal measurement.

[0097] [ Figure 5 This serves as an example of a curve illustrating the pressure values ​​measured by the first sensor 7 and the second sensor 9. A curve exists illustrating the change ΔP in the pressurized space and the pressure measured at test time t. test Pressure change ΔP in the internal environment ext Another curve. The curve is generated by an electronic entity and a first sensor 7 and a second sensor 9.

[0098] Therefore, electronic entity 15 is configured to pass through curve ΔP ext The calibration curve ΔP is used to obtain the corrected pressure change ΔP', which is no longer affected by environmental factors (pressure and / or temperature changes from the environment).

[0099] More specifically, the corrected pressure change ΔP' is calculated as follows:

[0100] ΔP'=(ΔP-k S ΔP ext )

[0101] Where k Sare normalization coefficients specific to the sensors 7 and 9, thus allowing to subtract from each other the values of each of the curves.

[0102] In [ Figure 6 ] an example of a corrected pressure curve ΔΡ' based on the curve in [ Figure 5 ] is described.

[0103] The normalization coefficients k S are for example:

[0104] - are determined for example by manufacturing extreme values based on the measured curves ΔΡ, ΔΡ ext ;

[0105] - are predetermined and their values are stored in the memory of the electronic entity 15.

[0106] Thus, the electronic unit 15 determines the leakage level F', also called corrected leakage level, from the corrected pressure variation ΔΡ' according to the following formula:

[0107]

[0108] where C1 is a constant depending on the time (for example the test time t test ) and the space V of the object being tested (that is to say the space of the object whose tightness will be determined.

[0109] Depending on the leakage value F' and according to the required threshold, the electronic entity 15 indicates whether the object being tested is compliant or not.

[0110] In an alternative embodiment, the electronic entity 15 determines the average temperature variation per unit of time of the object being tested via at least one sensor, for example the second sensor 9 or the third sensor 17.

[0111] The average temperature variation is then used to determine a corrected leakage F" depending on the pressure variation ΔΡ measured in the pressurized space and the pressure variation ΔΡ ext of the environment.

[0112] More particularly, in a step prior to the test, the second sensor 9 or the third sensor 17 is configured to measure the pressure variation ΔΡ T P (in Pa / s) depending on the average temperature variation per unit of time of the object.

[0113] This measurement can for example be performed during a step prior to the filling or during a stabilization phase, but it is necessary to isolate the object to be tested and / or the reference from the outside.

[0114] The electronic entity 15 then determines a corrected pressure variation ΔΡ" in the characteristic space of the object being tested depending on the following formula:

[0115] AP" = AP - k S AP ext - A T P

[0116] Subsequently, as previously described, the electronic entity 15 calculates the corrected leakage level F" based on AP" according to the previous equation.

Claims

1. A leak detection system (1) for checking the sealing performance of an object, the system (1) comprising: - A device for pressurizing space (5); - A first pressure sensor (7) is configured to measure pressure changes in the pressurized space; - A second pressure sensor (9) is configured to measure pressure changes at atmospheric pressure; - An electronic entity (15) configured to depend on the pressure change ΔP in the pressurized space and the pressure change ΔP of the atmospheric pressure. ext Determine the leaks F' and F', and the changes ΔP and ΔP'. ext The first sensor (7) and the second sensor (9) respectively test at a predetermined test time interval t test Internal measurement, The electronic entity (15) determines the leakage level F' of the tested object based on the corrected pressure change ΔP', which is calculated as follows: F'=C1ΔP'=C1(ΔP-k S ΔP ext ) Where k S C1 is a normalization coefficient specific to the first sensor (7) and the second sensor (9), and C1 is a constant that depends on the time and space of the object being tested. Determine the normalization coefficient k S : -Based on the curve of the pressure change ΔP in the space and the pressure change ΔP of the atmospheric pressure. ext The curve, or - The measurement of the pressure change ΔP in the space and the pressure change ΔP of the atmospheric pressure. ext Before the aforementioned measurement, The normalization coefficient k S The value is stored in the memory of the electronic entity (15).

2. The system according to claim 1, characterized in that, The pressure change ΔP in the space depends on the pressure change ΔP of the atmospheric pressure. ext Perform corrections.

3. The system according to claim 1, characterized in that, The first pressure sensor (7) and / or the second pressure sensor (9) are differential pressure sensors.

4. The system according to claim 1, wherein the electronic entity (15) and the first sensor (7) and the second sensor (9) enable the testing to be performed during the test time interval t. test Internal generation: - The curve of the pressure change ΔP in the space; - The pressure change ΔP of the atmospheric pressure ext The curve.

5. The system according to claim 1, characterized in that, The system includes a third pressure sensor (17) configured to measure the pressure P in the pressurized space.

6. The system according to claim 5, characterized in that, The electronic entity (15) determines the pressure change Δ in relation to the average temperature change of the object per unit time via at least one sensor. T P, the pressure change Δ T P is also used to determine the pressure change ΔP depending on the pressure change ΔP in the pressurized space and the pressure change ΔP of the atmosphere. ext Determine the leakage F of the tested object.

7. The system according to claim 6, wherein the electronic entity (15) is determined by the following formula to determine the leakage level F” of the tested object: F”=C1ΔP”=C1(ΔP-k S ΔP ext -Δ T P) Where ΔP” is the corrected pressure change of the tested object, Δ T P is the pressure change that depends on the average temperature change of the tested object during the test time, and C1 is a constant that depends on the time and space of the tested object.

8. The system according to claim 1, characterized in that, The system includes a thermally insulated housing configured to house the object to be tested.

9. A leak detection method (100) implemented in a leak detection system (1) according to claim 1, the method comprising the following steps: - Pressurize the space (S1) by pressurizing device (5); - The pressure change (S2) in the pressurized space is measured by the first pressure sensor (7); and - The pressure change of the atmospheric pressure is measured by the second sensor (9) (S3); - Depends on the pressure change ΔP of the pressurized space and the pressure change ΔP of the atmospheric pressure. ext Leakage is detected based on the corrected pressure change ΔP' (S4), and the corrected pressure change ΔP' is calculated as follows: F'=C1ΔP'=C1(ΔP-k S ΔP ext ) Where k S C1 is a normalization coefficient specific to the first sensor (7) and the second sensor (9), and C1 is a constant that depends on the time and space of the object being tested. Determine the normalization coefficient k S : -Based on the curve of the pressure change ΔP in the space and the pressure change ΔP of the atmospheric pressure. ext The curve, or - The measurement of the pressure change ΔP in the space and the pressure change ΔP of the atmospheric pressure. ext Before the aforementioned measurement, The normalization coefficient k S The value is stored in the memory of the electronic entity (15).

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