One-way safety valve, gas venting device and motor vehicle.

Abstract

The invention relates to a one-way safety valve comprising a body (8) which defines a chamber (9) and in which are provided an inlet orifice (10) and an outlet orifice (11) which open into the chamber and which are respectively equipped with an inlet valve (12) and an outlet valve (13) configured to prevent the passage of fluid except from the inlet orifice to the outlet orifice when the fluid reaches a determined pressure threshold on the inlet orifice side. According to the invention, the outlet valve is configured to be maintained in a position for closing said chamber by depressurizing the chamber. The invention also relates to an evacuation device equipped with such a valve and a motor vehicle equipped with a battery and such an evacuation device. Figure for abstract: Fig.2

Description

Title of the invention: One-way safety valve, gas evacuation device and motor vehicle. Technical field of the invention

[0001] The present invention generally relates to safety devices intended to equip enclosures and conduits receiving pressurized fluids.

[0002] It relates more particularly to a safety valve and finds a particularly advantageous application in the automotive field, in particular for the evacuation of gases possibly generated by the accumulators of the vehicle battery.

[0003] It also relates to a gas evacuation device equipped with such a valve, and a motor vehicle comprising such a device. State of the art

[0004] Electric or hybrid motor vehicles are equipped with a storage battery intended in particular to power the vehicle's powertrain and electrical network.

[0005] In accidental conditions, it may happen that one of the accumulators (or cells) of the battery heats up abnormally and causes the neighboring accumulators to heat up. Above a certain temperature (typically, around a hundred degrees), exothermic reactions occur in the cells which then generate gas. In order to avoid damage to the structure of the battery by the pressure of the gases, certain cases containing the accumulators are equipped with a membrane-type valve allowing the gases to escape.

[0006] Solutions exist to prevent these gases from entering the passenger compartment, where they could poison passengers or obscure the driver's visibility. Among these solutions, some propose connecting an exhaust duct to the battery box in order to evacuate the gases away from the passenger compartment, for example to the rear of the vehicle. During normal vehicle operation, no gas circulates in this duct and it should be protected from external elements that could penetrate it (water, foreign bodies, small animals, etc.). There are membrane-type closure systems, such as safety valves, which allow the duct to be closed as long as no pressurized gas circulates in it. However, existing systems have many drawbacks.For example, the membrane sealing the conduit is either not sufficiently resistant to external attacks and can easily rupture accidentally, for example under force exerted by a high-pressure cleaning jet, or too resistant so that the pressure in the conduit necessary for the membrane to rupture is too high. Furthermore, the membrane, once opened, may continue to at least partially obstruct the exhaust duct, thus hindering the proper evacuation of gases. Presentation of the invention

[0007] In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a safety valve which allows gases to be evacuated at a low pressure threshold, which is unidirectional (even under high external pressure), and which allows complete or unobstructed opening.

[0008] More particularly, the invention proposes a one-way safety valve comprising a body which defines a chamber and in which are provided an inlet orifice and an outlet orifice which open into the chamber and which are respectively equipped with an inlet valve and an outlet valve configured to prevent the passage of fluid except from the inlet orifice to the outlet orifice when the fluid reaches a determined pressure threshold on the inlet orifice side. The outlet valve is configured to be maintained in a position of closure of said chamber by depressurization of the chamber.

[0009] Maintaining the chamber in the closed position by depressurizing advantageously makes it possible to dispense with the need for mechanically fixing the valve to the body, which would hold the valve in the gas discharge path even if the chamber were opened. Furthermore, closing the chamber by depressurizing allows the use of a valve that is particularly strong and resistant to high external pressures, such as that induced by a high-pressure cleaning jet. It also allows fine adjustment of the determined pressure threshold, including for low values.

[0010] According to another aspect of the invention, there is provided a gas evacuation device for an accumulator battery module, comprising a gas evacuation conduit of which a first end is configured to communicate with the battery module and of which a second end opposite the first end is equipped with a safety valve according to the invention.

[0011] According to another aspect of the invention, there is provided a motor vehicle equipped with a storage battery and a gas evacuation device according to the invention.

[0012] Other advantageous and non-limiting characteristics of the safety valve according to the invention, taken individually or in all technically possible combinations, are the following: - a spring is compressed inside the chamber so as to exert on the inlet valve a first force tending to maintain the inlet valve in a position of closure of said chamber and so as to exert on the outlet valve a second force tending to maintain the outlet valve in an open position of said chamber, the chamber being configured to be depressurized so as to counter the second force but not the first force; - the inlet valve is placed inside the chamber at the inlet orifice so as to have a first surface in communication with the outside of the body, the outlet valve is placed outside the chamber at the outlet orifice and has a second surface in communication with the outside of the body, the value (or intensity) Fl of the first force, the value (or intensity) F2 of the second force, the area SI of the first surface and the area S2 of the second surface S2 being chosen so that API * Sl< Fl and F2 <AP2 * S2 , avec F1=F2, API a pressure differential across the inlet valve and AP2 a pressure differential across the outlet valve. - at least one of the inlet and outlet valves is mechanically independent of the body (i.e. mounted freely against the body); - a seal is placed between at least one of the valves and the body; - the inlet valve includes a depressurization port equipped with a check valve configured to allow depressurization of the chamber; - the chamber has the shape of a truncated cone, the inlet orifice being provided in the small base of the truncated cone and the outlet orifice being provided in the large base of the truncated cone; - the determined pressure threshold is between 0.1 and 0.5 bar and is preferably equal to 0.3 bar.

[0013] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0014] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0015] In the attached drawings:

[0016] [Fig.l] is a schematic view of a motor vehicle according to the invention;

[0017] [Fig.2] is a schematic sectional view of a safety valve according to the invention.

[0018] A motor vehicle according to an embodiment of the invention, such as re shown schematically in [Fig.l] and designated as a whole by the numerical reference 1, is provided with a battery 2 of electric accumulators equipped with a gas evacuation device 3.

[0019] The gas evacuation device 3 comprises an evacuation duct 4. A first end 5 of the duct 3 is in communication with the interior of a housing of the battery 2, here at the level of an orifice provided in the housing of the battery 2, the orifice being for example obstructed by a membrane valve. A second end 6 of the duct 4 is here equipped with a one-way safety valve 7.

[0020] The safety valve 7 is described as unidirectional in that it is configured to prevent the passage of fluid in one direction, regardless of the conditions. It is here configured to allow the passage of fluid in the other direction, here from the conduit 4 to the outside, only when the fluid reaches a determined pressure threshold in the conduit 4. The pressure considered is a relative pressure, so that it is equal to the pressure difference between the inside of the conduit 4 and the outside. The threshold is for example between 0.1 bar and 0.5 bar, here equal to 0.3 bar.

[0021] Thus, the conduit remains obstructed, unless a gas, for example generated by one or more accumulators of the battery 2, increases the pressure in the conduit 4 to the determined pressure threshold.

[0022] As illustrated in [Fig. 2], the safety valve 7 comprises a body 8 defining a chamber 9 in which an inlet orifice 10 and an outlet orifice 11 are provided which open into the chamber 9. Thus, the body 8 itself forms a conduit. The inlet orifice 10 and the outlet orifice 11 are respectively equipped with an inlet valve 12 and an outlet valve 13. The valves 12, 13 are configured to be in the closed position of the chamber 9 during normal operation of the vehicle 1, and to be in the open position of the chamber 9 when the determined pressure threshold is reached in the conduit 4. In the configuration of [Fig.2], the pressure inside the chamber is for example equal to 0.6 bar (i.e. a depression of 0.4 bar compared to the pressure outside the chamber 9), the pressure in the pipe is for example equal to 1 bar and the outside of the vehicle is at atmospheric pressure, which varies according to the altitude at which the vehicle 1 is located and which is here equal to 1 bar). In this configuration, the valves 12, 13 are in the closed position.

[0023] The chamber 9 is configured to be depressurized so as to maintain the outlet valve 13 in the closed position of the chamber 9. In other words, it is a force exerted on the outlet valve 13 and resulting from the pressure difference on either side of the outlet valve 13 which maintains the outlet valve 13 in the closed position of the chamber 9. No other force here tends to maintain the outlet valve 13 in the closed position.

[0024] In this example, the safety valve 7 has a symmetry of revolution around an axis Ax. Thus, the body 8 is here generally in the form of a straight cylinder and has an internal face which defines the chamber 9 and which has a cylinder shape with axis Ax, in particular here a truncated cone shape. The inlet orifice 10 is here formed in the small base of the truncated cone and the outlet orifice is here formed in the large base of the truncated cone. The inlet orifices 12 and outlet orifices 13 are coaxial circular orifices with axis Ax.

[0025] In particular here, the inlet orifices 10 and outlet orifices 11 are arranged at the level of shoulders 14, 15 of the chamber 9 so that the shoulders 14, 15 define contact surfaces for the valves 12, 13, flat and orthogonal to the axis Ax. In particular here, the inlet orifice 10 has a diameter smaller than the small base of the truncated cone. The outlet orifice 11 defines the large base of the truncated cone and is arranged at the bottom of a counterbore 16 arranged in the body 8.

[0026] The body 8 is here extended on the opposite side by an insertion collar 17, the inlet orifice 10 being here located at the junction between the body and this collar. The insertion collar 17 is here configured to ensure the attachment of the body 8 to the evacuation duct 4. Here, the insertion collar 17 is configured to be stamped into the evacuation duct 4.

[0027] The inlet valve 12 is here mechanically independent of the body 8, that is to say that it is mounted freely against a first shoulder 14 of the body 8 (no fixing means are used, neither glue, nor screw, nor snap-fastening, etc.). It has here the shape of a disc whose diameter is greater than the diameter of the inlet orifice 10. It is here rigid so that it does not deform during normal use of the valve.

[0028] Preferably, the diameter of the inlet valve 12 is only very slightly smaller than the diameter of the small base of the truncated cone so that in the closed position of the chamber 9, the inlet valve 12 is adjusted in the chamber 9. In this example, the contact between the inlet valve 12 and the first shoulder 14 is ensured by a first annular seal 18.

[0029] The outlet valve 13 is here mechanically independent of the body 8, that is to say it is mounted freely against a second shoulder 15 of the body 8. It has here the shape of a disc whose diameter is greater than the diameter of the outlet orifice 11. Preferably, the diameter of the outlet valve 13 is only very slightly less than the diameter of the counterbore 16 so that in the closed position of the chamber 9, the outlet valve 13 is adjusted in the counterbore. In this example, the contact between the outlet valve 13 and the second shoulder 15 is ensured by a second annular seal 19.

[0030] A spring 20 is compressed inside the chamber 9 so as to exert on the inlet valve 12 a first force tending to maintain the inlet valve 12 in a position of closure of said chamber 9 (i.e. pressing against the first shoulder 14 via the first seal 18) and so as to exert on the outlet valve 11 a second force tending to maintain the outlet valve 13 in an open position of the chamber 9 (i.e. it tends to move it away from the second shoulder 15). In this example, the spring 20 is a helical spring compressed between the inlet valve 12 and the outlet valve 13. Thus, the first force 7d and the second force 7^2 are in opposite directions (oriented along the axis Ax) and of the same value F12. In this example, at least one of the two ends of the spring is fixed to one of the two valves 12, 13, in order to facilitate the mounting and positioning of the spring relative to the valves. The spring force is sized according to the diameters of the valves and the value of the depression between the chamber 9 and the outside of the valve 7. In this example it is equal to 9.5 kg.

[0031] As mentioned previously, the chamber 9 is configured to be depressurized so as to maintain the outlet valve 13 in the closed position. For this purpose, the safety valve 7 comprises a depressurization orifice 21 equipped with a non-return valve 22 and configured to allow the depressurization of the chamber 9. Here, the depressurization orifice 21 is provided in the inlet valve 12 and is circular. The non-return valve 22 is formed by a simple ball pressed into the depression orifice 21.

[0032] In this example, a first API pressure differential on either side of the inlet valve (difference between the pressure inside the chamber 9 and the pressure in the conduit 4 if the safety valve 7 is fixed to the conduit 4, or between the pressure inside the chamber and atmospheric pressure if the safety valve 7 is not fixed) generates a third force in the opposite direction to the first force Jq and with a value F3 lower than the value Fl of the first force. Thus, the inlet valve 12 remains pressed against the first shoulder 14, here by means of the first seal 19. The pressure in the conduit 4 is approximately 1 bar, and can vary around this value depending on variations in the ambient temperature.

[0033] Furthermore, a second pressure differential AP2 on either side of the outlet valve 13 (difference between the pressure inside the chamber 9 and the atmospheric pressure) generates a third force F4 exerted on the outlet valve 13 which is in the opposite direction to the second force and of value F4 greater than the value F2 of the second force. Thus, the outlet valve 13 remains pressed against the second shoulder 15, here by means of the second seal 19.

[0034] The value F3 of the third force and the value F4 of the fourth force F4 are obtained by appropriate dimensioning of the elements of the safety valve 7.

[0035] In particular, the value F3 of the third force depends on the first API pressure differential, as well as on the area SI of a first surface of the inlet valve 12 on which the external pressure is applied, here the pressure inside the conduit 4. This surface is that which is exposed inside the conduit 4 and which is delimited by the inlet orifice in the absence of a seal between the first shoulder 14 and the inlet valve 12 or, as is the case here, by the first seal 18 (by its internal diameter in the case of a flat seal, by its average diameter in the case of an O-ring).

[0036] Thus, F3 = API * SL

[0037] The value F4 of the fourth force F4 depends on the second pressure differential AP2, as well as on the area S2 of a second surface of the outlet valve 13 on which the external pressure, here the atmospheric pressure, is applied. Here, the area S2 of the second surface is equal to the area of the disc formed by the outlet valve. The surface of the outlet valve 13 exposed inside the chamber 9 is here delimited by the internal diameter of the second seal 19.

[0038] Thus F4 = AP2 * S2

[0039] The value F12 of the forces pi and F2 exerted by the spring depends on the stiffness k of the spring, its compressed length L and its resting length L0. Thus, F12 = k * (L0-L)

[0040] The sizing of the safety valve 7 must therefore respect the following equation:

[0041] API * Sl< k.(LO-L) <AP2 * S2

[0042] In normal operation of the vehicle 1, the equation [Math. 1] is verified and the valves 12, 13 are maintained in the closed position of the chamber 9. As soon as the pressure in the discharge conduit 4 reaches the determined pressure threshold, then the first force is no longer sufficient to counter the third force (API * Sl> k(L0-L)). The inlet valve 12 therefore moves to the open position of the chamber 9 and the pressure in the chamber 9 increases in such a way that the fourth force p4 becomes less than the second force F2 (k(L0-L) >AP2 * S2). The spring 20, the inlet valve 12 and the outlet valve 13 are expelled from the chamber and completely free the passage for the discharge of the gas. Thus, there is no risk of the safety valve 7 re-closing nor any risk of partial obstruction by one of the valves remaining in the chamber. The truncated cone shape of the chamber 9 facilitates the expulsion of the valves and the spring.

[0043] The safety valve as described above is not limited by its manufacturing materials, as long as they are not incompatible with its operation. Preferably, the outlet valve 13 is made of a robust and water-resistant material, so as to withstand external aggressions such as a high-pressure cleaning jet. For example, the outlet valve is made of stainless steel. Preferably, the body and the inlet and outlet valves are made of stainless steel. The body and the valves can also be made of any hard and stable material over time, particularly a polymer material.

[0044] The invention is not limited to the embodiment described above in connection with Figures 1 and 2. Thus, although a valve having a symmetry of revolution has been described, other shapes can be envisaged for the body, the chamber and the valves. In particular, the inlet and outlet valves can have different geometries from each other (beyond their dimensions). For example, one of the valves, preferably the outlet valve, can have a shape other than a disc, for example an octagonal, hexagonal or rectangular shape.

[0045] The truncated cone shape of the chamber allows good evacuation of the valves and the spring. However, the chamber can have other shapes, in particular a straight cylinder shape.

[0046] Valves have been described previously whose contact with the body is made by means of annular seals. The invention is not limited to this type of seal, nor even to the presence of seals. In certain variants, only one of the valves is associated with a sealing seal.

[0047] A helical spring placed in the chamber and configured to exert a force on each of the valves has been previously described. The invention is not limited to a helical spring, but is compatible with any type of spring.

[0048] Finally, the safety valve according to the invention is preferably adapted to be fixed to a battery gas evacuation conduit. However, other applications are conceivable and the safety valve according to the invention can be fixed to other sealed conduits or enclosures, for example a liquefied petroleum gas (LPG) tank for a motor vehicle.

Claims

Claims

1. One-way safety valve comprising a body (8) which defines a chamber (9) and in which are provided an inlet orifice (10) and an outlet orifice (11) which open into the chamber (9) and which are equipped respectively with an inlet valve (12) and an outlet valve (13) configured to prevent the passage of fluid except from the inlet orifice (10) to the outlet orifice (11) when the fluid reaches a determined pressure threshold on the side of the inlet orifice (10), characterized in that the outlet valve (13) is configured to be maintained in a position of closure of said chamber (9) by depressurization of the chamber (9).

2. Safety valve according to claim 1, in which a spring (2) is compressed inside the chamber (9) so as to exert on the inlet valve (12) a first force (fi) tending to maintain the inlet valve 12 in a position of closing said chamber (9) and so as to exert on the outlet valve (13) a second force (f2) tending to maintain the outlet valve (13) in a position of opening said chamber (9), the chamber (9) being configured to be depressurized so as to counter the second force (f5) but not the first force (F4).

3. Valve according to claim 2, in which the inlet valve (12) is placed inside the chamber (9) at the inlet orifice (10) so as to have a first surface in communication with the outside of the body (8), the outlet valve (13) is placed outside the chamber (9) at the outlet orifice (11) and has a second surface in communication with the outside of the body (8), the intensity Fl of the first force (fÎ), the intensity F2 of the second force (F2), Faire SI of the first surface and Faire S2 of the second surface being chosen so that API * Sl < Fl and F2 <AP2 * S2, avec F1=F2, API un différentiel des pressions de part et d’autre de la soupape d’entrée (12) et AP2 un différentiel des pressions de part et d’autre de la soupape de sortie (13).

4. A valve according to any one of claims 1 to 3, wherein at at least one of the inlet (12) and outlet (13) valves is mechanically independent of the body (8).

5. A valve according to any one of claims 1 to 4, wherein a seal (18, 19) is placed between at least one of the valves (12, 13) and the body (8).

6. A valve according to any one of claims 1 to 5, wherein the inlet valve (12) comprises a depressurization orifice (21) equipped with a non-return valve (22) and configured to allow depressurization of the chamber (9).

7. A valve according to any one of claims 1 to 6, wherein the chamber (9) has a truncated cone shape, the inlet orifice (10) being provided in the small base of the truncated cone and the outlet orifice (13) being provided in the large base of the truncated cone.

8. Valve according to any one of claims 1 to 7, in which the determined pressure threshold is between 0.1 and 0.5 bar and is preferably equal to 0.3 bar.

9. Gas evacuation device for an accumulator battery module, comprising a gas evacuation conduit (4) of which a first end (5) is configured to communicate with the battery module (2) and of which a second end (6) opposite the first end (5) is equipped with a safety valve (7) according to any one of claims 1 to 8.

10. Motor vehicle equipped with a storage battery (2) and a gas evacuation device (3) according to claim 9.

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