Safety device for an electricity storage system for a vehicle

Abstract

The present invention relates to an electricity storage system (1) for a vehicle, comprising a casing (2) and at least one electricity storage cell (3) arranged in the casing (2), and a thermal treatment circuit (4) configured to be flowed through by a cooling fluid, the thermal treatment circuit (4) comprising a circulation-inducing means (5) and a heat exchanger (6), the thermal treatment circuit (4) extending within the casing (2) so that the cooling fluid thermally treats the electricity storage cell (3), characterized in that the electricity storage system (1) comprises a safety device (8) comprising a safety valve (10) and a cyclone separation device (9) centered about an axis, the axis passing through the safety valve (10).

Description

[0001] Title of the invention: Safety device for a vehicle's electricity storage system

[0002] The present invention relates to the field of hybrid or electric vehicles and more particularly concerns a safety device for an electricity storage system arranged within such vehicles.

[0003] Electricity storage systems consist of multiple electricity storage cells. These cells store electrical energy during vehicle charging and then supply it to the vehicle during operation. During operation, particularly during charging, the electricity storage cells generate heat and must be cooled. To achieve this, the electricity storage cells are integrated into a casing, which is fluidically connected to a heat treatment circuit that cools the cells. A cooling fluid circulates within the heat treatment circuit and also within the casing to thermally cool the electricity storage cells through direct contact.

[0004] Occasionally, a malfunction in the electricity storage cells can occur, generating thermal runaway within the electricity storage system. Gas then forms within the thermal processing circuit, creating overpressure within that circuit.

[0005] To prevent overpressure from damaging the heat treatment circuit, it is equipped with a safety valve that opens if a pressure threshold is exceeded. The safety valve is positioned at or near the control box to allow for quick and effective resolution of overpressure problems.

[0006] The problem with such a configuration is that, when the safety valve opens, the gases generated by the thermal runaway are evacuated, but this also results in a loss of coolant which also escapes through the safety valve.

[0007] The present invention falls within this context and, as such, proposes a vehicle electricity storage system comprising at least one housing and at least one electricity storage cell disposed within the housing, and a heat treatment circuit configured to be traversed by a cooling fluid. The heat treatment circuit includes at least one means for circulating the cooling fluid within the circuit and a heat exchanger. The heat treatment circuit extends within the housing so that the cooling fluid thermally treats the electricity storage cell. The distinctive feature of the electricity storage system is that it includes a safety device comprising at least one safety valve and a cyclonic separation device centered around an axis, the axis passing through the safety valve.

[0008] The electricity storage system according to the invention thus makes it possible, in the event of overpressure due to thermal runaway or any other malfunction generating gas, to evacuate said gas from the thermal treatment system without generating any loss of cooling fluid.

[0009] The casing is sealed to prevent any leakage of coolant and can house a large number of electricity storage cells. The electricity storage cells are advantageously grouped into an electricity storage pack, which may contain, for example, 196 electricity storage cells. The casing is integrated into the thermal processing circuit.

[0010] The heat treatment circuit can be circulated by a pump driving the cooling fluid. The heat exchanger allows the cooling fluid to be treated by exchanging heat with a third fluid, which could be, for example, air, nitrogen, or any other refrigerant. Depending on the requirements, the cooling fluid can be cooled or heated according to the needs of the electricity storage cells.

[0011] Thanks to the cyclone separator, the gas generated by a thermal runaway is evacuated without releasing any cooling fluid. The overpressure created by the presence of gas forces the cooling fluid to circulate around the periphery of the cyclone separator. Due to centrifugal force, the cooling fluid, being denser than the gas, is forced to the periphery of the cyclone separator as it rotates around its axis, while the gas, being less dense than the cooling fluid, is forced to the center of the cyclone separator. The safety valve can then open, and only the gas escapes from the electricity storage system. The cooling fluid is thus conserved and prevented from being wasted by an unexpected release through the safety valve. For example, the safety valve opens when the pressure within the electricity storage system exceeds 80 mbar.

[0012] According to one feature of the invention, the safety device comprises a main body defining an internal volume, an inlet located at a first end of the main body, and an outlet located at a second end of the main body opposite the first end. The main body is formed of at least one cylindrical wall centered around its axis, and at least the inlet of the safety device extends tangentially to the cylindrical wall. The inlet and outlet allow the cooling fluid to enter and exit the safety device, respectively. After entering the main body, the cooling fluid flows from the first end to the second end in a circular motion around the axis, along the cylindrical wall. The tangential extension of the inlet initiates the circulation of the cooling fluid around the axis.The pressure increase due to the presence of gas resulting from thermal runaway also contributes to an increase in the circulation speed of the cooling fluid and thus improves the rotation of the cooling fluid around the axis.

[0013] According to one feature of the invention, the safety device comprises an upper wall closing the first end of the main body. The upper wall serves to delimit the first end and contributes to the sealing of the electricity storage system.

[0014] According to one feature of the invention, the safety device comprises a chimney centered on the axis, the chimney passing through the upper wall. The chimney includes a first opening leading into the internal volume of the main body and a second opening through which the safety valve extends. The chimney allows the safety valve to be positioned to ensure gas evacuation when necessary. The chimney's position through the upper wall allows the safety valve to be placed at a distance from the internal volume, thus preventing the coolant from escaping, for example, through splashing. The first opening, however, allows fluid connection between the cyclone separator and the safety valve, enabling gas to escape through the safety valve if it opens.According to one feature of the invention, the chimney and the cylindrical wall radially delimit the internal volume of the main body, the internal volume having a circular profile. The chimney preferably has a circular cross-section and a diameter smaller than the diameter of the circular wall, so that the chimney can be partially integrated within the internal volume.

[0015] The chimney thus forms a space between the latter and the cylindrical wall, and it is within this space that the cooling fluid circulates, ensuring circular circulation.

[0016] According to one feature of the invention, the circular profile is helical. The helical shape allows the cooling fluid to progress along the axial direction while circulating circularly around the axis. This configuration also optimizes the separation between the cooling fluid and the gas that forms during the thermal runaway of the electricity storage cells.

[0017] According to one feature of the invention, the helical profile of the internal volume extends over an angular sector of at least 360°. In other words, within the safety device, the cooling fluid must preferably complete at least one full rotation around the axis to ensure effective separation from the gas. An angular sector of approximately 360° means that at least one point at the inlet and at least one point at the outlet of the safety device can be axially aligned with each other.

[0018] According to one feature of the invention, the internal volume is axially delimited by the upper wall and a lower wall opposite the upper wall. The cooling fluid thus flows between the upper and lower walls, which also contribute to delimiting the internal volume, following a circular, and optionally helical, profile.

[0019] According to one feature of the invention, the safety device is configured so that a first distance between a plane defined by the first chimney opening and the lower wall, measured along the axis, is greater than a second distance between the upper and lower walls. This configuration allows the entire cooling fluid to follow the circular profile for at least 360°, as described above, before reaching the first chimney opening. The gas contained in the cooling fluid is thus separated more efficiently before the first opening, and therefore the chimney and the safety valve, becomes accessible, ensuring the evacuation of said gas.

[0020] According to one feature of the invention, the heat treatment circuit includes a bypass branch for the safety device. Circulation within the safety device results in a pressure drop that can negatively impact the thermal performance of the heat treatment circuit. The bypass branch thus prevents such a pressure drop by bypassing the safety device during normal operation, i.e., without malfunctions, of the electricity storage system. In the event of thermal runaway, access to the bypass branch can be closed so that the cooling fluid circulates only within the safety device.

[0021] According to one feature of the invention, the safety device is fluidly connected to an outlet of the housing. Advantageously, the gas generated following a thermal runaway must be evacuated as quickly as possible to prevent further damage. Since the cause originates from the electricity storage cells, the safety device is advantageously located at the housing outlet to evacuate the gas as quickly and efficiently as possible.

[0022] According to one feature of the invention, the electricity storage system is characterized in that it comprises a cooling fluid, the cooling fluid being dielectric. A dielectric fluid allows the electricity storage cells to be thermally treated by direct contact. Advantageously, the dielectric fluid completely fills the casing so that all the electricity storage cells are fully immersed in the dielectric fluid.

[0023] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0024] [Fig. 1] is a schematic representation of an electricity storage system according to the invention,

[0025] Figure 2 is a schematic representation of a safety device integrated within the electricity storage system. Figure 1 represents an electricity storage system 1 according to the invention. Such an electricity storage system 1 can be integrated into an electric or hybrid vehicle to supply previously stored electrical energy. To this end, the storage system comprises a housing 2 in which at least one electricity storage cell 3 is arranged, advantageously a plurality of electricity storage cells 3. The electricity storage cells 3 are capable of receiving and storing electrical energy when the vehicle is being recharged, and of supplying the stored energy when the vehicle is in use. All the electricity storage cells 3 are housed within the housing 2.

[0026] During operation, for example after rapid charging, the electricity storage cells 3 tend to release heat. To prevent overheating, the electricity storage cells 3 must be regularly thermally treated. For this purpose, the casing 2 is fluidly connected to a thermal treatment circuit 4, which controls the temperature of the electricity storage cells 3, for example, by cooling them when they release heat that could lead to overheating.

[0027] The heat treatment circuit 4 is traversed by a cooling fluid. Advantageously, this cooling fluid is dielectric, so that the electricity storage cells 3 are immersed within the casing 2 in order to cool them by direct contact with the cooling fluid.

[0028] The heat treatment circuit 4 comprises a circulation means 5 and a heat exchanger 6. The circulation means 5 carries the cooling fluid, which then passes through the heat exchanger 6 to be heated or cooled as required by the electricity storage cells 3. The cooling fluid can, for example, be cooled to a low temperature by heat exchange with a third fluid. The circulation means 5 can, for example, be a pump.

[0029] Subsequently, the cooling fluid circulates into the casing 2 and advantageously fills it, thus fully immersing all the electricity storage cells 3 for thermal treatment. The cooling fluid then exits the casing 2 and recirculates again via the circulation means 5 and the heat exchanger 6 to continue the thermal treatment of the electricity storage cells 3. Optionally, the thermal treatment circuit 4 may include a reservoir 7 if it is necessary to increase the quantity of cooling fluid circulating in the thermal treatment circuit 4.

[0030] During the operation of the electricity storage system 1, a malfunction may occur, in particular a thermal runaway of the electricity storage cells 3. Such a thermal runaway leads to the formation of gas within the thermal treatment circuit, which increases the internal pressure of the thermal treatment circuit 4 and risks causing further damage to the thermal runaway.

[0031] To avoid this, the electricity storage system 1 includes a safety device 8 fluidly connected to the thermal treatment circuit 4. The safety device 8 includes a cyclonic separation device 9 and a safety valve 10.

[0032] In the event of thermal runaway, the cooling fluid circulates within the safety device 8. The cyclone separator 9 allows the separation of the gas formed as a result of the thermal runaway of the cooling fluid, as will be described in detail later. The safety valve 10 then opens to ensure the gas escapes from the electricity storage system 1.

[0033] The cyclonic separation device 9 includes an inlet 11 and an outlet 12 through which respectively the cooling fluid circulating within the safety device 8 enters and exits. It is during the circulation between the inlet 11 and the outlet 12 that the separation between the cooling fluid and the gas takes place.

[0034] The safety device 8 as described thus allows the gas formed following a thermal runaway to be evacuated without the coolant escaping through the safety valve 10. The electricity storage system 1 thus guarantees to avoid any overpressure resulting from a thermal runaway, and this without generating any loss of coolant.

[0035] Advantageously, the safety device 8 is located downstream of the housing 2, fluidly connected to an outlet of the housing 2. This allows for the rapid evacuation of the gas generated by the thermal runaway of the electricity storage cells 3, thus preventing the thermal treatment circuit 4 from being maintained for an excessively long period. The gas formed within the housing 2 then flows through the safety device and is directly evacuated via the safety valve 10 without circulating through other components of the thermal treatment circuit 4, which could be damaged by the passage of the gas.

[0036] The heat treatment circuit 4 also includes a bypass branch 13, also fluidically connected to the housing 2 and extending in parallel with the safety device 8. When there is no malfunction, and therefore no gas to be evacuated, the coolant circulates within the bypass branch 13 instead of circulating within the safety device 8. Such a configuration avoids an unnecessary pressure drop due to the circulation of the coolant in the safety device 8 when it is not necessary to circulate it there.

[0037] Figure 2 is a schematic representation of the safety device 8 illustrating in more detail its structural and functional characteristics.

[0038] The safety device 8, more specifically the cyclone separation device 9, comprises a main body 14 delimiting an internal volume 15. The main body 14 is formed by a cylindrical wall 16 centered around an axis 17 and extends between a first end 18 and a second end 19 opposite the first end 18. The inlet 11 is arranged at the first end 18 while the outlet 12 is arranged at the second end 19.

[0039] As illustrated in Figure 1, the inlet 11 extends tangently to the cylindrical wall 16. This initiates circulation along the cylindrical wall 16 with the participation of centrifugal force, which separates the gas resulting from thermal runaway from the cooling fluid. Furthermore, the pressure generated by the gas increases the circulation velocity of the cooling fluid, thus intensifying this centrifugal force.

[0040] To ensure the evacuation of gas from the safety device 8, the latter includes a chimney 20 centered around the axis 17. The chimney 20 includes a first opening 21 opening into the internal volume 15 and a second opening 22 in which the safety valve 10 extends, the latter passing through the axis 17. The first opening 21 ensures access of the gas within the chimney 20, after the latter has been separated from the cooling fluid.

[0041] The safety valve 10 closes the second opening 22 in its initial position and opens it in the event of overpressure within the electricity storage system. The safety valve 10 is, for example, configured to open and vent gas when the pressure in the electricity storage system exceeds a pressure threshold of 80 mbar.

[0042] The first end 18 is closed by an upper wall 23 and the chimney 20 passes through said upper wall 23. Such a configuration allows the safety valve 10 to be positioned away from the circulation of the cooling fluid, thus ensuring that only the gas from the thermal runaway is evacuated from the electricity storage system via the safety valve 10.

[0043] As mentioned, the chimney 20 passes through the upper wall 23 and thus extends partially into the internal volume 15. The latter is therefore radially delimited by the chimney 20 and by the cylindrical wall 16. The internal volume 15 thus has a circular, advantageously helical, profile, which allows the cooling fluid to circulate within the main body 14 rotating around the axis 17. The centrifugal force is then initiated to ensure subsequent optimal evacuation of the gas through the safety valve 10.

[0044] Preferably, the circular profile, and helical if necessary, is configured to extend within the internal volume 15 along an angular sector of at least 360°. In other words, the circular profile is configured so that the cooling fluid circulating in the safety device 8 makes a complete rotation around the axis 17. It has indeed been demonstrated that a complete rotation of the cooling fluid is a minimum to achieve optimal separation and evacuation of the gas from the storage system.

[0045] In order to further ensure that the entire cooling fluid undergoes a rotation of at least 360°, the internal volume 15 is axially defined by the upper wall 23 and a lower wall 24 opposite the upper wall 23.

[0046] The lower wall 24 and a plane 25 defined by the first opening 21 are axially separated by a first distance DI, while the upper wall 23 and the lower wall 24 are separated from each other by a second distance D2. The first distance DI is advantageously greater than the second distance D2 so that the entire cooling fluid rotates at least 360° within the internal volume 15, between the chimney 20 and the cylindrical wall 16. Optionally, the cylindrical wall 16 is divided into a first portion 26 with a circular cross-section, extending parallel to the chimney 20, and a second portion 27 with a conical cross-section, allowing the cooling fluid, free of gas, to accumulate up to the outlet 12.Thus, although the electricity storage cells 3 must be replaced following a thermal runaway, the electricity storage system according to the invention makes it possible to avoid overpressure within the thermal treatment circuit by evacuating the gas generated by said thermal runaway via the safety valve 10 while avoiding a loss of cooling fluid through this same safety valve 10. Of course, the invention is not limited to the examples that have just been described and many modifications can be made to these examples without departing from the scope of the invention.

[0047] The invention, as described above, achieves its intended purpose and provides a thermal treatment system comprising a safety device for the selective venting of gases resulting from a thermal runaway in at least one electricity storage cell. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they include an electricity storage system conforming to the invention.

Claims

DEMANDS 1- Electricity storage system (1) of a vehicle, comprising at least one casing (2) and at least one electricity storage cell (3) disposed in the casing (2), and a heat treatment circuit (4) configured to be traversed by a cooling fluid, the heat treatment circuit (4) comprising at least one means for circulating (5) the cooling fluid within the heat treatment circuit (4) and a heat exchanger (6), the heat treatment circuit (4) extending within the casing (2) so that the cooling fluid thermally treats the electricity storage cell (3), characterized in that the electricity storage system (1) comprises a safety device (8) comprising at least one safety valve (10) and a cyclone separation device (9) centered around an axis (17), the axis (17) passing through the safety valve (10). 2- Electricity storage system (1) according to claim 1, in which the safety device (8) comprises a main body (14) delimiting an internal volume (15), an inlet (11) disposed at a first end (18) of the main body (14) and an outlet (12) disposed at a second end (19) of the main body (14) opposite the first end (18), the main body (14) being formed of at least one cylindrical wall (16) centered around the axis (17), at least the inlet (11) of the safety device (8) extending tangent to the cylindrical wall (16). 3- Electricity storage system (1) according to claim 1 or 2, wherein the safety device (8) comprises an upper wall (23) closing the first end (18) of the main body (14). 4- Electricity storage system (1) according to claim 3, in which the safety device (8) comprises a chimney (20) centred on the axis (17), the chimney (20) being traversing the upper wall (23), the chimney (20) comprising a first opening (21) leading into the internal volume (15) of the main body (14) and a second opening (22) in which the safety valve (10) extends. 5- Electricity storage system (1) according to claim 4, in which the chimney (20) and the cylindrical wall (16) radially delimit the internal volume (15) of the main body (14), the internal volume (15) having a circular profile. 6- Electricity storage system (1) according to claim 5, wherein the circular profile is helical. 7- Electricity storage system (1) according to claim 6, wherein the helical profile of the internal volume (15) extends over an angular sector which is in particular at least 360°. 8- Electricity storage system (1) according to any one of claims 3 to 7, in which the internal volume (15) is axially delimited by the upper wall (23) and a lower wall (24) opposite the upper wall (23). 9- Electricity storage system (1) according to claim 8, in combination with any one of claims 4 to 7, wherein the safety device (8) is configured so that a first distance (D1) between a plane (25) defined by the first opening (21) of the chimney (20) and the lower wall (24) measured along the axis (17) is greater than a second distance (D2) between the upper wall (23) and the lower wall (24). 10- Electricity storage system (1) according to any one of the preceding claims, comprising a bypass branch (13) of the safety device (8). 11- Electricity storage system (1) according to any one of the preceding claims, wherein the safety device (8) is fluidly connected to an output of the housing (2). 12- Electricity storage system (1) according to any one of the preceding claims, characterized in that it comprises the cooling fluid, the cooling fluid being dielectric.

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