Protective box, cryogenic fluid storage unit and vehicle

Abstract

Protective box, cryogenic fluid storage unit and vehicle. The protective box (9) is shaped to internally house at least one cryogenic fluid storage tank (7) and to protect this storage tank (7) against external aggressions such as shocks or fires. It comprises an outer casing (11) having: - a mounting wall (37) intended to be fixed to the vehicle (1); - a protective wall (39) opposite the mounting wall (37); - lower and upper walls (41, 43); - a front wall (45) and a rear wall (47).The protective box (9) further includes a reinforcement structure (65) comprising: - at least one longitudinal beam (67) rigidly fixed to the protective wall (39); - a plurality of oblique beams (69), connecting the at least one longitudinal beam (67) to the upper wall (43) and to the lower wall (41); - stiffening profiles (71) each fixed to the upper wall (43) or to the lower wall (41), near fixing points of the oblique beams (69) to said upper and lower walls (43, 41) Figure for the abbreviation: 2.

Description

Title of the invention: Protective box, cryogenic fluid storage unit and vehicle

[0001] The invention relates generally to vehicles equipped with cryogenic fluid tanks.

[0002] It is possible to equip a heavy vehicle such as a truck with two cryogenic fluid storage tanks.

[0003] This vehicle comprises a chassis, with two longitudinal side members spaced transversely apart from each other.

[0004] The two storage tanks can be fixed to the two longitudinal members, cantilevered transversely with respect to these longitudinal members, towards the outside of the vehicle.

[0005] The cryogenic fluid is, for example, hydrogen. The hydrogen powers an internal combustion engine or a fuel cell producing electricity for the vehicle's propulsion motor.

[0006] The storage tank must be protected from shocks and the risk of fire.

[0007] In the event of a transverse impact, in particular, the integrity of the tank and the secure attachment of the storage tanks to the longitudinal members must be guaranteed. The tank and its equipment must not leak as a result of said impact.

[0008] It is possible to provide, for the storage tanks, very thick walls and to fix the tanks to the stringers by means of straps.

[0009] Such an arrangement has the drawback that the tanks are quite heavy. This makes attaching them to the side members particularly difficult.

[0010] In this context, the invention aims to provide a vehicle that does not have the above defects.

[0011] To this end, the invention relates, in a first aspect, to a rigid protective box intended to be mounted on board a vehicle, the protective box being shaped to internally receive at least one cryogenic fluid storage tank and to protect this storage tank against external aggressions such as shocks or fires, the protective box comprising an outer casing including:

[0012] - a fixing wall intended to be fixed to the vehicle;

[0013] - a protective wall opposite the fixing wall;

[0014] - lower and upper walls facing respectively towards a surface of vehicle rolling and opposite the rolling surface;

[0015] - a front wall and a rear wall facing longitudinally forward and towards the rear of the vehicle;

[0016] the protective box further comprising a reinforcement structure including:

[0017] - at least one longitudinal beam rigidly fixed to the protective wall;

[0018] - a plurality of oblique beams, securing at least one longitudinal beam to the upper wall and the lower wall;

[0019] - stiffening profiles each fixed to the upper wall or to the wall lower, near the fixing points of the oblique beams to said upper and lower walls.

[0020] The protective box provides protection for the storage tank against impacts and flames. This makes it possible to reduce the thickness of the storage tank walls, and therefore their mass.

[0021] The protective box of the invention makes it possible to absorb a shock against a vehicle weighing between 250 kg and 2.5 tonnes, preferably between 1 and 1.5 tonnes, the vehicle traveling up to 60 km / h, preferably between 40 and 50 km / h.

[0022] The fact that the outer casing has six walls arranged in pairs makes it particularly suitable for resisting impacts. Such a structure is very rigid. The forces are transmitted from one wall to the next.

[0023] The reinforcement structure allows for the highly efficient transmission of forces from the protective wall to the upper and lower walls in the event of a transverse impact. These forces are transmitted to several zones distributed across the lower and upper walls, thereby reducing the stress levels in these walls.

[0024] The stiffening profiles help to limit the deformation of the upper and lower walls. Indeed, the forces transmitted by the oblique beams to the upper and lower walls tend to deform these walls, creating outward bulges in the box. The stiffening profiles help to limit these deformations.

[0025] The protective box may also have one or more of the following characteristics, considered individually or in all technically possible combinations: - One or more of the following walls are reinforced with a structured sheet metal reinforcement: the protective wall, the lower wall, the upper wall - the fixing wall, the protective wall, the lower wall, and the front and rear walls are solid; - in which the upper wall has openings connecting an internal volume of the outer envelope with an atmosphere outside the outer envelope.

[0026] According to a second aspect, the invention relates to a cryogenic fluid storage unit, comprising a protective box having the above characteristics, and a cryogenic fluid storage tank rigidly fixed inside the outer casing of the protective box, the storage tank being spaced from the protective wall by at least 40 mm.

[0027] The storage unit may also have one or more of the following characteristics, considered individually or in all technically possible combinations:

[0028] - the storage tank includes an internal tank delimiting a volume of cryogenic fluid storage, and an external tank inside which is housed the internal tank, the protective box comprising internal partitions securing the external casing to the external tank of the storage tank housed in said external casing;

[0029] - the protective box includes a front cradle passing under one end front of the external tank and securing the external tank to the front wall, and a rear cradle passing under a rear end of the external tank and securing the external tank to the rear wall;

[0030] - the storage tank is transversely relatively closer to the wall of fixing only to the protective wall.

[0031] According to a third aspect, the invention relates to a vehicle comprising:

[0032] - a chassis, comprising two longitudinal longitudinal members spaced transversely apart compared to the other;

[0033] - two cryogenic fluid storage units having the above characteristics opposite the two longitudinal members, the outer casing of the protective box of each storage unit comprising an upper part fixed to one of the two longitudinal members, the protective box being arranged in cantilever outwards from the vehicle relative to said longitudinal member in the transverse direction;

[0034] - a spacer structure, connecting the respective lower parts of the two outer envelopes to each other.

[0035] The vehicle may also have the following characteristics:

[0036] - the spacer structure comprises transverse bars connecting one to the other the lower walls of the two outer envelopes.

[0037] Other features and advantages of the invention will become apparent from the detailed description given below, by way of example and not limitation, with reference to the accompanying figures, among which: - [Fig.1] The [Fig.1] is a simplified schematic representation, in top view, of a vehicle conforming to the invention; - [Fig.2] Fig.2 is an exploded view showing the storage tank of cryogenic fluid and the protective box for this tank; - [Fig. 3] Fig. 3 is an elevational view of the tanks and boxes protection, considered longitudinally from the front side, the front walls of the protective boxes not being shown in order to reveal the inside of said protective boxes; - [Fig.4] The [Fig.4] a perspective view of the mounted protective boxes on the vehicle's side members in [Fig.1], the front wall, the upper wall, the protective wall and the storage tank of one of the boxes are not shown; - [Fig. 5] Fig. 5 is an elevational view of one of the protective boxes, viewed longitudinally from the front side of the vehicle, showing the transmission of forces in the event of a side impact, the mounting wall not being shown; and - [Fig. 6] Figure 6 shows the three simulated loading cases digitally to demonstrate the technical advantages offered by the vehicle of the invention.

[0038] Vehicle 1 shown in [Fig. 1] comprises:

[0039] - a chassis 3 comprising two longitudinal longitudinal members 5 spaced transversely one in relation to the other;

[0040] - two cryogenic fluid storage units 6, opposite the two longerons 5.

[0041] Each cryogenic fluid storage unit 6 comprises:

[0042] - a cryogenic fluid storage tank 7;

[0043] - a protective box 9, the protective box 9 comprising an envelope external 11 inside which the storage tank 7 is rigidly fixed.

[0044] The vehicle is a motor vehicle. This vehicle is, for example, a truck, or a bus, or a van, or a car, or even a construction vehicle such as a mechanical shovel.

[0045] Alternatively, this vehicle is a train, a boat or any other suitable type of vehicle.

[0046] A cryogenic fluid is understood to be a fluid at a very low temperature, capable of to be found at least partially in a liquid state inside the storage tank. This fluid is typically hydrogen. Alternatively, the fluid is helium, nitrogen, a natural gas such as methane CH4, air, or any other suitable fluid.

[0047] The cryogenic fluid is typically intended to power a fuel cell or an internal combustion engine. The fuel cell is configured to produce electricity and electrically power the vehicle's electric propulsion motor.

[0048] In this description, the longitudinal direction corresponds to the normal direction of travel of the vehicle. The vertical direction is the direction perpendicular to the vehicle's plane of travel. The lateral direction is perpendicular to both the vertical and longitudinal directions. Front and rear are understood relative to the longitudinal direction. Top and bottom, upper and lower, are understood relative to the vertical direction.

[0049] The chassis 3 is a rigid structure on which various vehicle components are mounted, for example the axles. The chassis 3 longitudinal members 5 extend parallel to each other. They are substantially at the same vertical level with respect to the vehicle's running surface 1.

[0050] The two storage units 6 are mounted, one on one of the longitudinal members 5 and the other on the other longitudinal member 5.

[0051] Typically, the vehicle 1 has only two storage units 6. Alternatively, the vehicle 1 has additional storage units, in addition to said two storage units 6. These additional storage units are of the same type and are mounted in the same way as the storage units 6. The vehicle 1 has, for example, an even number of additional storage units, each pair having one storage unit mounted on one of the side members 5 and another mounted on the other side member 5.

[0052] Each storage tank 7 comprises an internal tank 13 (see [Fig.2]) delimiting a storage volume of the cryogenic fluid, and an external tank 15 inside which the internal tank 13 is housed.

[0053] The storage tank 7 further includes a suspension not shown fixing the inner tank 13 to the outer tank 15.

[0054] The internal reservoir 13 has a substantially longitudinal central axis C.

[0055] The external reservoir 15 has a cylindrical ferrule 17, coaxial with the central axis C. The ferrule 17 is closed at its two axial ends by front and rear ends 19.

[0056] The internal reservoir 13 and the external reservoir 15 delimit between them an intermediate space maintained under a high vacuum.

[0057] Not shown, thermal insulation is interposed between the internal reservoir 13 and the external reservoir 15.

[0058] Each storage tank 7 also includes various conduits 21 opening into the cryogenic fluid storage volume ([Fig. 3]). The conduits 21 connect the storage volume to various auxiliary equipment 23 such as heat exchangers, valves, safety valves, etc.

[0059] Furthermore, the external reservoir 15 is equipped with an orifice not shown, intended to create a vacuum in the space delimited between the internal reservoir 13 and the external reservoir 15. This orifice is closed by a cover not shown.

[0060] The opening is provided in the rear bottom 19.

[0061] The conduits 21, the auxiliary equipment 23 are gathered at a front end of the storage tank 7, and are protected by a hood 31.

[0062] The hood 31 is placed opposite the front bottom 19, the conduits 21 being housed between the hood 31 and the front bottom 19.

[0063] The outer casing 11 has an upper part fixed to one of the two longitudinal members 5.

[0064] The upper part here corresponds to the half of the outer envelope 11 located upwards, that is to say turned away from the rolling surface.

[0065] As can be seen in particular in figures 1, 3 and 4, the mounting box 9 is arranged in cantilever outwards from the vehicle 1 relative to said longitudinal member 5 in the transverse direction.

[0066] This means that each protective box 9 is entirely located outside the chassis 3 longitudinal members 5 relative to the longitudinal member 5 which carries it, and is not located between the two longitudinal members 5.

[0067] Furthermore, the vehicle 1 includes a spacer structure 35, visible in figures 3 and 4, securing the respective lower parts of the two external envelopes 11 to each other.

[0068] The lower part of the outer casing corresponds here to half of the outer casing 11 turned downwards, i.e. towards the rolling surface of the vehicle 1.

[0069] As can be seen in the figures, the outer envelope 11 is preferably parallelepiped-shaped.

[0070] It thus comprises a fixing wall 37 fixed to the corresponding longitudinal member 5, a protective wall 39 opposite the fixing wall 37, lower and upper walls 41 and 43 turned respectively towards the vehicle's running surface and opposite the running surface, a front wall 45 and a rear wall 47 turned longitudinally respectively towards the front and rear of the vehicle 1.

[0071] The fixing wall 37 and the protective wall 39 extend in respective planes substantially perpendicular to the transverse direction.

[0072] The upper wall 43 and the lower wall 41 extend in respective planes substantially perpendicular to the vertical direction.

[0073] The front and rear walls 45, 47 extend in planes substantially perpendicular to the longitudinal direction.

[0074] The fixing wall 37, the protective wall 39, the lower and upper walls 41, 43 and the front and rear walls 45, 47 are rigidly fixed to each other and together define a box with high rigidity. Each wall is perpendicular to the four walls adjoining it.

[0075] The longeron 5 is a C-shaped metal profile, with a central web 51 of substantially longitudinal and vertical orientation, and two flanges 53 arranged above and below the central web 51, perpendicular to them.

[0076] The fixing wall 37 is pressed against the central core 51 and rigidly fixed to it.

[0077] The walls 37, 39, 41, 43, 45, 47 are sheets of steel with very high yield strength.

[0078] They are made of a martensitic or dual phase type steel.

[0079] Each protective box 9 comprises a plurality of internal partitions 55 securing the outer casing 11 to the external reservoir 15 of the storage reservoir 7 housed in said outer casing 11.

[0080] These internal partitions 55 are in planes perpendicular to the longitudinal direction. They are distributed along the ferrule 17.

[0081] Each internal partition 55 has a central orifice in which the ferrule 17 is engaged.

[0082] Each internal partition 55 is welded to the ferrule 17.

[0083] It is also welded by an external edge to the outer casing 11. More Specifically, it is welded to the fixing wall 37, the protective wall 39, the upper wall 43 and the lower wall 4L

[0084] These internal partitions 55 make it possible to stiffen the ferrule 17, which must withstand the vacuum created between the internal reservoir 13 and the external reservoir 15. Adding these internal partitions 55 makes it possible to reduce the wall thickness of the external reservoir 15.

[0085] Advantageously, the mounting wall 37, the protective wall 39, the lower wall 41, the front wall 45 and the rear wall 47 are solid, i.e., without openings. This helps to improve fire resistance. Indeed, in the event of a fire under the vehicle, the flames will not be able to directly reach the storage tank 7.

[0086] On the other hand, the upper wall 43 preferably has openings 57 connecting an internal volume of the outer envelope 11 with an atmosphere outside the outer envelope 11.

[0087] These openings 57 allow air to escape in the event of a fire. Indeed, in the event of a fire under the vehicle, the lower wall 41 is the most exposed to the flames. It will heat the air contained inside the outer casing 11. This hot air will tend to rise and can escape through the openings 57 in the upper wall 43. It will be replaced by cooler air, thus creating a convective movement that helps to cool the storage tank 7.

[0088] Furthermore, in the event of a hydrogen leak, the hydrogen will be able to escape through the openings 57 in the upper wall 43.

[0089] Advantageously, one or more of the following walls are doubled by a structured stiffening sheet 59: the protective wall 39, the lower wall 41, the upper wall 43.

[0090] Preferably, these three walls are doubled by a structured stiffening sheet 59.

[0091] The structured stiffening plate 59 is substantially the same size as the wall to which it is attached. It is rigidly fixed to a large face of the wall, either on the inside or outside of the outer casing.

[0092] The sheet metal is structured in the sense that it has reliefs which contribute to stiffening said sheet metal.

[0093] These reliefs are typically rectilinear hollow shapes, separated by rectilinear protruding shapes.

[0094] For the lower wall 41 and the upper wall 43, the rectilinear recessed shapes and the rectilinear projecting shapes are oriented transversely. For the protective wall 39, the rectilinear recessed shapes and the rectilinear projecting shapes are oriented vertically.

[0095] Typically, each structured stiffening plate 59 is folded into parallel notches. Alternatively, each structured stiffening plate 59 is a corrugated plate. Alternatively, the structured stiffening plate 59 is formed with other types of reliefs.

[0096] The wall 39, 41, 43 and the structured stiffening sheet 59 together form a sandwich exhibiting good resistance to buckling.

[0097] The protective box 9 further includes a front cradle 61 passing under a front end of the external tank 15 and securing the external tank 15 to the front wall 45.

[0098] As can be seen in [Fig. 3], the front cradle 61 is an arched sheet metal, for example in the shape of a half-cylinder. It is rigidly fixed to the ferrule 17 of the external reservoir 15. It is also rigidly fixed to an inner face of the front wall 45.

[0099] The front cradle 61 has an internal radius substantially equal to the external radius of the ferrule 17, the ferrule 17 resting in the front cradle 61.

[0100] The front cradle 61 closes downwards the space separating the front bottom 19 of the external tank 15 from the front wall 45. It is in this space that the auxiliary equipment 23 of the external tank 15 and the conduits 21 are located.

[0101] The cradle 61 helps to protect these components from heat in the event of a fire under the vehicle.

[0102] The protective box 9 further includes a rear cradle 63 passing under a rear end of the external tank 15 and securing the external tank 15 to the rear wall 47.

[0103] The rear cradle 63 is a cylindrical metal plate. It forms a ring around the rear end of the ferrule 17 and is fixed to it. It is also rigidly fixed to the rear wall 47. It has an internal radius substantially equal to the external radius of the ferrule 17.

[0104] Alternatively, the rear cradle 63 does not have a closed contour but extends only over a fraction of a circle, for example over a semicircle closing the bottom of the ferrule 17.

[0105] The protective box 9 further includes a reinforcing structure 65 comprising:

[0106] - at least one longitudinal beam 67 rigidly fixed to the protective wall 39;

[0107] - a plurality of oblique beams 69, securing at least one beam longitudinal 67 to the upper wall 43 and to the lower wall 4L

[0108] For example, the reinforcement structure 65 comprises two longitudinal beams 67 rigidly fixed to the protective wall 39. These beams are, for example, directly fixed to an inner face of the protective wall 39, the structured sheet 59 being fixed to an outer face of the protective wall 39.

[0109] The or each longitudinal beam 67 is a flat metal profile.

[0110] The oblique beams 69 are, for example, metal profiles with a closed rectangular section.

[0111] Typically, one of the longitudinal beams 67 is fixed to the upper part of the protective wall 39. The other longitudinal beam 67 is fixed to the lower part of the protective wall 39.

[0112] A group of oblique beams 69 has one end rigidly fixed to the upper longitudinal beam 67, and another end fixed to the upper wall 43.

[0113] Another group of oblique beams 69 has one end rigidly fixed to the lower longitudinal beam 67, and another end fixed to the lower wall 4L.

[0114] Each oblique beam 69 is arranged in a plane perpendicular to the longitudinal direction. Considered in said plane, it forms an isosceles triangle with the protective wall 39 and with the lower wall 41 or the upper wall 43.

[0115] Advantageously, the structured sheets 59 are fixed to the inner faces of the upper wall 43 and the lower wall 4L. The ends of the oblique beams 69 are placed in rectilinear hollow forms of the structured sheets 59.

[0116] Furthermore, the reinforcement structure 65 also includes stiffening profiles 71 each fixed to the upper wall 43 or to the lower wall 41, near the fixing points of the oblique beams 69 to said upper and lower walls 43, 4L These stiffening profiles 71 make it possible to stiffen the upper wall 43 or the lower wall 41, near the fixing points.

[0117] For example, two stiffening profiles 71 are arranged in the rectilinear hollow forms receiving the ends of the oblique beams 69, on either side of the end of the oblique beam 69.

[0118] The stiffening profiles 71, and the rectilinear hollow shapes, extend transversely. The end of the oblique beam 69 is pinched longitudinally between the two stiffening profiles 71. The two stiffening profiles 71 are parallel and arranged side by side, with a space between them to receive the end of the oblique beam 69.

[0119] It should be noted that the storage tank 7 is offset along the transverse direction towards the chassis 3 inside the protective box 9.

[0120] In other words, the storage tank 7 is located transversely closer to the fixing wall 37 than to the protective wall 39, to allow deformation of the protective wall 39 in the event of a lateral impact.

[0121] The storage tank 7 being spaced from the protective wall 39 by at least 40 mm. The storage tank 7 is located at a distance from the protective wall 39 of between 40 and 100 mm, preferably between 60 and 80 mm, and even more preferably of about 75 mm.

[0122] The storage tank 7 is located at a distance from the fixing wall 37 less than or equal to 10 mm.

[0123] It should also be noted that the storage tank 7 has no direct contact with the lower wall 41 or the structured sheet 59 reinforcing this wall. The storage tank 7 is in thermal contact with the lower wall 41 only through the internal partitions 55. These internal partitions 55 have a small cross-section, so that heat transfer by conduction from the lower wall 41 to the external tank 15 is extremely limited.

[0124] Furthermore, a layer of thermal insulation not shown, for example polyurethane, is applied to the inner side of the lower wall 41, further limiting the heating of the storage tank 7 in the event of a fire.

[0125] The spacer structure 35 includes cross bars 73 connecting the lower walls 41 of the two external envelopes 11 to each other.

[0126] The cross bars 73 and the lower walls 41 of the two external envelopes 11 extend in the same horizontal plane, that is to say in the same plane parallel to the rolling plane.

[0127] Typically, the spacer structure 35 comprises two cross bars 73, one placed longitudinally at the level of the front wall 45 and the other placed longitudinally at the level of the rear wall 47.

[0128] The front-side crossbar 73 has opposite ends connected by links 75 to the two outer sheaths 11. These links 75 are located at the apex to which the fixing wall 37, the front wall 45 and the lower wall 41 are joined. The connections 75 are pivot connections, allowing rotation of the crossbar 73 relative to the outer casing 11 around a longitudinal axis.

[0129] Similarly, the rear crossbar 73 has its two ends connected to the two outer sheaths 11 by joints 75. These joints 75 are located at the vertices where the rear wall 47, the fixing wall 37, and the lower wall 41 meet. They are also of the pivot joint type, about longitudinal axes.

[0130] The spacer structure 35 further presents, for each crossbar 73, two arms 77 connecting the crossbar 73 to the fixing walls 41 of the two external envelopes 11.

[0131] Each arm 77 has one end 79 rigidly fixed to the bar 73 and another end connected to the outer casing 11 by a link 81.

[0132] The joint 81 is located on the edge along which the front wall 45 or the rear wall 47 joins the mounting wall 37. The joint 81 is a pivot joint about a longitudinal axis. In the vertical direction, the joint 81 is positioned towards the center of the mounting wall 37.

[0133] The end 79 of the arm 77 is rigidly fixed near the center of the crossbar 73.

[0134] The arms 77 and the crossbar 73 extend in a plane perpendicular to the longitudinal direction. Each arm 77 forms a triangle with the end of the crossbar 73, of which the fixing wall 37 constitutes one side.

[0135] The vehicle described above offers excellent performance in the event of a crash.

[0136] The behavior of this vehicle was simulated by calculation for the three cases of The loads are shown in [Fig. 6]. In the first load case, a load 83 strikes the storage tank 7 laterally, with an approach angle of 27°. The second load case corresponds to the impact of a load on a corner of the protective box, with an approach angle of 30°, either on the front or rear side. The third load case corresponds to a transverse impact of a linear structure 85, such as a pole (crash pole).

[0137] The numerical parameters selected for these three loading cases are summarized in the table below: Loading case Load mass (kg) Impact speed (km / h) Approach angle (°) Impact angle (°) 1 1368 54 27 90 2 1600 35 30 30 3 1600 15 90 90

[0138] The following table shows the results of the calculations. The second and third columns of the table give the results for a storage tank without a protective box, with an external tank having a wall thickness of 4 mm.

[0139] The second column indicates the maximum indentation of the external reservoir, in millimeters, and the third column the maximum stress experienced by the external reservoir, in MPa.

[0140] The fourth and fifth columns of the table provide the same information, but for a tank according to the invention, equipped with a protective box, with an external tank having a wall thickness of only 2 mm. Without protective box, wall thickness 4 mm With protective box, wall thickness 2 mm Load case m Penetration m Stress (MP Penetration m Stress (MP) ent ax (mm) a) ax (mm) a) 1 217 595 15 100-390 2 81 610 0 0 3 116 628 0 100 (300)

[0141] For loading case 1, this table shows that in the absence of a protective box, the outer tank is severely deformed. The risk of tank destruction is significant. The pressure inside the tank is significantly increased due to the deformation, such that the shut-off valves of the cryogenic fluid lines may no longer be able to perform their functions. The weld lines are subjected to very high tensile stresses, which can lead to rupture. The suspension of the inner tank to the outer tank is also affected.

[0142] On the contrary, with the protective box, the dent at the level of the external tank is minimal, and the internal tank is not deformed. The suspensions are affected by the impact, but the risk of damage to these suspensions is extremely low. Only the areas located at the internal partitions 55 are subjected to high stresses, but at an acceptable level, without risk of rupture of the external tank.

[0143] Loading case 2, for an unprotected tank, is particularly critical when the impact occurs on the cover 31. The indentation into the outer tank is significantly less than in the first loading case, but the mechanical stresses are even higher, especially at the cover. There is a significant risk of leakage due to possible equipment failure. auxiliary tank components under the effect of the impact. The primary tank suspensions are subjected to significant stresses, on the order of 300 MPa.

[0144] On the contrary, for a tank equipped with the protective box of the invention, there is no impact on the external or internal tank. The risk of leakage is negligible.

[0145] Loading case 3, in the absence of a protective box, leads to a significant risk of the tank tearing along the impact line if this impact occurs at the ferrule 17. The dent in the outer tank is approximately 116 mm. This dent results in a significant increase in internal pressure, which further increases the risk of tank damage. The internal suspensions are significantly affected.

[0146] If the impact occurs at the level of the hood 31, the penetration is less, but there is a risk that the auxiliary equipment of the tank will be destroyed, leading to a leak of the cryogenic fluid.

[0147] In the case of a tank equipped with a protective box, the indentation of the external tank is zero. The external tank is subjected to a moderate level of mechanical stress, locally reaching a value of 300 MPa at the internal partitions 55. The level of mechanical stress in the suspensions remains moderate.

[0148] The following table details the effects on the internal tank, the external tank, and the protective box for the three loading cases described above, but only for the vehicle of the invention. It shows that the vehicle's behavior is satisfactory for all the loading cases considered. Load Case Penetration (mm) Stresses (MPa) Tank Damage Suspension Damage Protection Box Damage Internal Tank External Tank Internal Tank External Tank 10 150-50 100 (390) Only the external tank is damaged Low Significant damage distributed over a large area, deformation of the lower and upper walls 200000 No damage. No damage to the front and rear walls. 3000100 (300) Sinking points at the external tank. Subjected to moderate stress (180 MPa). Local sinking.

[0149] These results are partly explained by a good distribution of forces in the protective box 9. As illustrated in [Fig.5], in the event of a lateral impact on the protective wall 39, part of the forces is transmitted directly from the protective wall 39 to the lower and upper walls 41, 43 along the protective wall 39 (arrows Fl).

[0150] Another part of the forces is transmitted by the longitudinal beams 67 and the oblique beams 69 to the upper wall 43 and to the lower wall 41 (arrows F2).

[0151] The forces taken up by the upper wall 43 are directly transmitted to the stringers 5 (arrow F3).

[0152] The forces absorbed by the lower wall 41 are transmitted to the strut structure 35 (arrow F4) and to the protective box located on the opposite side of the vehicle. These forces result in a very limited displacement of said opposite protective box.

[0153] The vehicle described above has multiple advantages.

[0154] Because each protective box includes internal partitions connecting the outer casing to the outer reservoir of the storage tank, the outer reservoir can be of reduced thickness. The presence of the internal partitions stiffens the outer reservoir, which must withstand the vacuum created between the outer and inner reservoirs. The outer reservoir has a geometry that is particularly unfavorable for resistance to collapse under vacuum. It typically has a length close to 2.5 m and a diameter close to 700 mm.

[0155] Due in particular to the presence of internal partitions, it is possible to reduce the wall thickness of the external tank from 4 mm to 2 mm. This makes it possible to significantly reduce the overall weight of the storage tank.

[0156] The fact that the fixing wall, the protective wall, the lower wall and the front and rear walls are solid, makes it possible to protect the storage tank from flames in the event of a fire under the vehicle.

[0157] The fact that the upper wall has openings connecting the internal volume of the outer casing to the outside atmosphere allows, in case The fireproof system vents hot gases outside the outer casing. The vents also allow hydrogen to escape in case of a leak.

[0158] The fact that one or more walls are reinforced with a structured sheet metal reinforcement, in particular the protective wall, the lower wall, and the upper wall, gives these walls good buckling resistance. In the event of an impact, particularly a transverse impact, these walls effectively transmit the forces to the vehicle's side members or to the opposing protective box.

[0159] Because the protective box includes a front cradle passing under one front end of the external tank and securing the external tank to the front wall, and a rear cradle passing under one rear end of the external tank and securing the external tank to the rear wall, the storage tank is held in position inside the protective box. Furthermore, the front and rear cradles protect the ends of the storage tank in the event of a fire. In particular, the front cradle acts as a firebreak under the vehicle for the tank's auxiliary equipment, located between the front end of the external tank and the front wall. Indeed, the auxiliary equipment is particularly vulnerable in the event of a fire. The storage tank itself, because it contains a cryogenic fluid, exhibits significant thermal inertia.This is not the case for auxiliary equipment, which heats up rapidly if exposed to flames or if poorly protected against flames. The consequences of a burst pipe or a damaged valve can be particularly serious.

[0160] If the safety valves become non-functional due to heat, the storage tank may explode as a result of the temperature rise.

[0161] If the cover closing the vacuum port is exposed to excessive temperature, the seals isolating the cover from this vacuum port may melt. Outside air can then enter the space between the inner and outer tanks, significantly degrading the thermal insulation of the inner tank. Immediately after this event, the incoming air will liquefy upon contact with the wall of the inner tank. After a certain time, the liquid air will evaporate again, and the pressure between the inner and outer tanks will increase until it expels the cover from the vacuum port. This will result in the influx of a large flow of external air, at a high temperature due to the fire under the vehicle. The cryogenic fluid contained in the inner tank will therefore rise in pressure rapidly, causing the safety valves to open.The safety valves, and the pipes on which these valves are mounted, must therefore be sized accordingly, which increases the cost of the storage tank.

[0162] Furthermore, in the event of a transverse impact on one side of the vehicle, some of the forces applied to the protective box located on that side are transmitted by the crossmember structure to the protective box located on the other side. The two protective boxes, the crossmember structure, and the side members together constitute a rigid structure, limiting or preventing damage to the tank. The primary objective of the box is to deform as little as possible and to protect the tank. The crossmember structure limits the rotation of the box so that the object causing the impact is always in the direction in which the box best resists the force and to prevent the object striking the box, typically a vehicle, from passing under the tank.

[0163] The spacer structure also helps to balance the stresses from the road. Indeed, with each bump in the road, the gearbox and its tank will experience vertical acceleration, and due to its cantilevered mounting, these stresses will be transformed into micro-deformations that can only be rotations. These deformations will lead to fatigue failures. To withstand these stresses without a spacer structure, the mounting would have to be considerably stiffened, thus increasing the overall mass by adding reinforcements. The spacer structure limits rotational micro-deformations while being much lighter than these reinforcements.

[0164] Because the spacer structure includes cross bars connecting the lower walls of the two external envelopes to each other, the forces are transmitted between the two protective boxes at particularly rigid areas.

Claims

Demands

1. A rigid protective box (9) intended to be mounted on board a vehicle (1), the protective box (9) being shaped to internally receive at least one cryogenic fluid storage tank (7) and to protect this storage tank (7) against external aggressions such as shocks or fires, the protective box (9) comprising an outer casing (11) having: - a mounting wall (37) intended to be fixed to the vehicle (1); - a protective wall (39) opposite the mounting wall (37); - lower and upper walls (41, 43) facing respectively towards a rolling surface of the vehicle (1) and away from the rolling surface; - a front wall (45) and a rear wall (47) facing longitudinally towards the front and rear of the vehicle (1);the protective box (9) further comprising a reinforcement structure (65) including: - at least one longitudinal beam (67) rigidly fixed to the protective wall (39); - a plurality of oblique beams (69), securing the at least one longitudinal beam (67) to the upper wall (43) and to the lower wall (41); - stiffening profiles (71) each fixed to the upper wall (43) or to the lower wall (41), near fixing points of the oblique beams (69) to said upper and lower walls (43, 41).

2. Protective box (9) according to claim 1, in which one or more of the following walls are lined with a structured stiffening sheet (59): the protective wall (39), the lower wall (41), the upper wall (43).

3. Protective box (9) according to claim 1 or 2, wherein the fixing wall (37), the protective wall (39), the bottom wall (41), and the front and rear walls (45, 47) are solid.

4. Protective box (9) according to any one of the preceding claims, in which the upper wall (43) has openings (57) connecting an internal volume of the outer envelope (11) with an atmosphere outside the outer envelope (11).

5. Cryogenic fluid storage unit (6), comprising a protective box (9) according to any one of the preceding claims, and a cryogenic fluid storage tank (7) rigidly fixed inside the outer shell (11) of the protective box (9), the storage tank (7) being spaced from the protective wall (39) by at least 40 mm.

6. Storage unit (6) according to claim 5, in which the storage tank (7) comprises an internal tank (13) delimiting a cryogenic fluid storage volume, and an external tank (15) within which the internal tank (13) is housed, the protective box (9) comprising internal partitions (55) securing the external casing (11) to the external tank (15) of the storage tank (7) housed in said external casing (11).

7. Storage unit (6) according to claim 6, in which the protective box (9) comprises a front cradle (61) passing under a front end of the external tank (15) and securing the external tank (15) to the front wall (45), and a rear cradle (63) passing under a rear end of the external tank (15) and securing the external tank (15) to the rear wall (47).

8. Storage unit (6) according to any one of claims 5 to 7, wherein the storage tank (7) is transversely relatively closer to the fixing wall (37) than to the protective wall (39).

9. Vehicle (1) comprising: - a chassis (3), having two longitudinal side members (5) spaced transversely apart from each other; - two cryogenic fluid storage units (6) according to any one of claims 5 to 8, opposite the two side members (5), the outer casing (11) of the protective box (9) of each storage unit (6) comprising an upper part fixed to one of the two side members (5), the protective box (9) being arranged cantilevered outwards from the vehicle (1) relative to said side member (5) in the transverse direction; - a spacer structure (35), securing the respective lower parts of the two outer casings (11) to each other.

10. Vehicle according to claim 9, wherein the strut structure (35) comprises cross bars (73) connecting to each other the lower walls (41) of the two outer shells (11).

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