Cryogenic fluid storage unit and method for manufacturing such a storage unit

Abstract

Cryogenic fluid storage unit and method of manufacturing such a storage unit The cryogenic fluid storage unit (1) comprises a suspension (9) fixing the inner tank (3) to the outer tank (7).The suspension (9) includes a linkage (25) comprising: - an intermediate tube (35) having an intermediate proximal end (37) fixed to the internal reservoir (3) and an intermediate distal end (39), - an internal tube (41) arranged inside the intermediate tube (35), having an internal proximal end (43) and an internal distal end (45), - an annular ring (47) connecting the intermediate distal end (39) to the internal distal end (45); - a sliding linkage (113) from the internal proximal end (43) to the external reservoir (7), comprising a sliding tube (115) rigidly fixed to the external reservoir (7) and a low-friction coating (117) covering an internal surface (119) of the sliding tube (115), the internal proximal end (43) being slidably engaged in the sliding tube (115) and sliding on the low-friction coating (117). Figure for the abridged version: 2.

Description

Title of the invention: Cryogenic fluid storage unit and method for manufacturing such a storage unit

[0001] The present invention relates generally to a cryogenic fluid storage unit.

[0002] Such a storage unit may include an internal tank internally delimiting a cryogenic fluid storage volume, an external tank in which the internal tank is housed, and a suspension fixing the internal tank to the external tank.

[0003] The suspension comprises two links, each of which suspends one of the two opposite ends of the inner reservoir from the outer reservoir.

[0004] It is possible to provide that one of the two links is sliding, to allow the contraction or thermal expansion of the internal reservoir relative to the external reservoir.

[0005] These thermal cycles can cause wear on the sliding link.

[0006] In this context, the invention aims to provide a storage unit whose suspension is designed to limit wear due to thermal cycles.

[0007] To this end, the invention relates to a cryogenic fluid storage unit, comprising an internal reservoir internally delimiting a cryogenic fluid storage volume, an external reservoir in which the internal reservoir is housed, and a suspension fixing the internal reservoir to the external reservoir, the suspension comprising a connection including:

[0008] - an intermediate tube having an intermediate proximal end fixed to the internal reservoir and an intermediate distal end,

[0009] - an inner tube arranged inside the intermediate tube, having an end proximal internal end and a distal internal end,

[0010] - an annular ring connecting the intermediate distal end to the end distal internal; - a sliding connection from the inner proximal end to the outer reservoir, comprising a sliding tube rigidly fixed to the outer reservoir and a low coefficient of friction coating covering an inner surface of the sliding tube, the inner proximal end being slidably engaged in the sliding tube and sliding on the low coefficient of friction coating.

[0011] Because the inner proximal end slides on the low coefficient of friction coating, the wear caused by the displacements of the inner proximal end in the sliding tube is extremely limited.

[0012] These displacements occur particularly during the filling of the internal tank with cryogenic fluid when the internal tank is at a temperature much higher than 20 K, for example -40°C, for example during the initial filling, or during refilling after it has been completely emptied. The temperature of the internal tank drops sharply, while the temperature of the external tank remains essentially constant. As a result, the internal tank contracts, causing a displacement of the internal tube relative to the sliding tube. This displacement can reach 9 mm for a vehicle storage unit approximately 2.5 m long.

[0013] The cryogenic fluid storage unit may further represent one or more of the following characteristics, considered individually or according to all technically possible combinations:

[0014] - the low-friction coating comprises a reinforcement, for example a sheet of expanded metal, and a layer of a low-friction material in which the reinforcement is embedded;

[0015] - the low coefficient of friction material is a PTFE or a PEEK;

[0016] - the sliding tube has a central tubular part and two ends opposite on either side of the central tubular part, the internal surface having a central surface along the central part and, at both ends, end surfaces flaring out from the central surface, the low friction coating covering the central surface and the end surfaces;

[0017] - the internal tube has a central axis, the internal proximal end having a external surface having, in section in a radial plane containing the central axis, a convex profile;

[0018] - the connection comprises:

[0019] * an external tube having an external proximal end fixed to the reservoir internal and an external distal end located inside the storage volume;

[0020] * a base plate closing the external distal end;

[0021] the intermediate tube being arranged inside the external tube;

[0022] - the linkage includes a movement limiter, limiting the displacement of the tube internal relative to the internal reservoir in a plane perpendicular to the central axis of the internal tube;

[0023] - the movement limiter is a ring integral with the internal reservoir, arranged around the sliding tube.

[0024] According to a second aspect, the invention relates to a method for manufacturing a storage unit having the above characteristics, the method comprising the following steps:

[0025] - obtaining a sub-assembly comprising the inner reservoir, the intermediate tube attached to the internal reservoir, the internal tube arranged inside the intermediate tube, and the annular ring connecting the intermediate distal end to the internal distal end; - obtaining the low coefficient of friction coating and the sliding tube;

[0026] - fixing the sliding tube to the external reservoir;

[0027] - application of the low-friction coating to the internal surface of the sliding tube;

[0028] - sliding engagement of the internal proximal end in the tube sliding;

[0029] the low friction coefficient coating being obtained by placing a thickness of a raw low friction coefficient material on either side of a reinforcement, and by polymerizing said low friction coefficient material to obtain a layer of low friction coefficient material in which the reinforcement is embedded.

[0030] Preferably, the sliding tube has a central tubular part and two opposite ends on either side of the central tubular part, the internal surface of the sliding tube having a central surface along the central part and, at both ends, end surfaces flaring out from the central surface, the placement of the low coefficient of friction coating on the internal surface of the sliding tube being carried out by introducing the low coefficient of friction coating inside the sliding tube and then flaring out sections of the end of the low coefficient of friction coating to press them against the two end surfaces.

[0031] 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.l] The [Fig.l] is an axial section view of the cryogenic fluid storage unit; - [Fig. 2] [Fig. 2] is an enlarged axial sectional view of a cou smoothing of the suspension of the storage unit of the [Fig.1]; - [Fig.3] The [Fig.3] is an enlarged view of a detail III of the [Fig.2]; - [Fig.4] Fig.4 is a developed plan view of the re-frame garment with low coefficient of friction integrated into the sliding link of figures 2 and 3; - [Fig. 5] [Fig. 5] is a cross-sectional view of the sliding tube and the re garment with a low coefficient of friction, the sliding joint of figures 2 and 3; and - [Fig. 6] [Fig. 6] is a view similar to that of [Fig. 2], illustrating a non-sliding linkage of the suspension of the storage unit of [Fig.l].

[0032] In figures 2, 3 and 6, certain welds joining the parts to each other are not shown.

[0033] The storage unit 1 shown in [Fig.1] is intended to store a cryogenic fluid.

[0034] Cryogenic fluid is understood to mean a fluid at a very low temperature, which may be at least partially in a liquid state inside the storage unit.

[0035] This fluid is typically hydrogen. Alternatively, the fluid is helium, nitrogen, a natural gas such as methane CH4, air, or any other suitable fluid.

[0036] This storage unit is typically intended to be carried on board a vehicle having an electric propulsion engine, for example a motor vehicle, a train, a boat or any other vehicle.

[0037] The motor vehicle is for example a car, a utility vehicle, a truck, etc.

[0038] The storage unit 1 is intended to power a fuel cell. The fuel cell is configured to produce electricity and electrically power the electric propulsion motor of the vehicle.

[0039] The cryogenic fluid storage unit 1 comprises an internal reservoir 3 internally delimiting a cryogenic fluid storage volume 5, an external reservoir 7 inside which the internal reservoir 3 is housed, and a suspension 9 fixing the internal reservoir 3 to the external reservoir 7.

[0040] In the example shown, the internal reservoir 3 has a horizontal central axis C.

[0041] The internal reservoir 3 comprises a ferrule 11, closed at its two axial ends by bottoms 13.

[0042] The ferrule 11 is cylindrical, centered on the central axis C.

[0043] The external reservoir 7 is also horizontally oriented.

[0044] It comprises a ferrule 15, closed at its two axial ends by bottoms 17.

[0045] The ferrule 15 is cylindrical, centered on the central axis C.

[0046] The internal reservoir 3 and the external reservoir 7 delimit between them an inter-space median 19, maintained under a high vacuum.

[0047] This vacuum is typically on the order of 105 mbar, so as to strongly limit the heat transfer by convection from the external reservoir 7 to the internal reservoir 3.

[0048] A thermal insulation 21 is interposed between the inner tank 3 and the outer tank 7. The thermal insulation 21 is typically placed on the outer surface of the inner tank 3. The thermal insulation 21 comprises, for example, a plurality of metal sheets superimposed one on top of the other, with interposed layers of fibers.

[0049] The suspension 9 is arranged so that the entire weight of the internal reservoir 3 is taken up by the external reservoir 7 via the suspension 9.

[0050] The weight of the internal reservoir 3 is understood here to include the weight of the cryogenic fluid stored in the internal reservoir 3.

[0051] The accelerations experienced by the internal reservoir 3 and the cryogenic fluid contained in the internal reservoir 3 are also transmitted to the external reservoir 7 via the suspension 9.

[0052] When the storage unit 1 is mounted in a vehicle, these accelerations result from changes in the direction of the vehicle, braking applied to the vehicle or acceleration of the vehicle, roughness or irregularities of the road, or shocks applied to the vehicle.

[0053] In the example shown, the suspension 9 comprises two links 23, 25.

[0054] The links 23, 25 each suspend one of the two opposite axial ends of the internal reservoir 3 from the external reservoir 7.

[0055] Links 23 and 25 are different from each other.

[0056] The link 23 is a link connecting the internal reservoir 3 to the external reservoir 7 without degrees of freedom.

[0057] The link 23 is intended to allow the passage of cryogenic fluid to, or from, the storage volume 5.

[0058] The link 25, on the contrary, is a sliding link. It is configured to link the internal reservoir 3 to the external reservoir 7 with one degree of freedom, thus allowing the thermal expansion or contraction of the internal reservoir 3 relative to the external reservoir 7.

[0059] Link 25 is not intended for the passage of cryogenic fluid.

[0060] As illustrated in [Fig.2], link 25 comprises:

[0061] - an intermediate tube 35, having an intermediate proximal end 37 fixed to the internal reservoir 3 and an intermediate distal end 39;

[0062] - an inner tube 41 arranged inside the intermediate tube 35, having a an internal proximal end 43 fixed to the external reservoir 7 and an internal distal end 45; and

[0063] - an annular ring 47 connecting the intermediate distal end 39 to the end distal internal 45.

[0064] Link 25 also includes:

[0065] - an external tube 27 having an external proximal end 29 fixed to the reservoir internal 3 and an external distal end 31 located inside the storage volume 5;

[0066] - a base plate 33 closing the external distal end 31;

[0067] The intermediate tube 35 is arranged inside the external tube 27.

[0068] The external tube 27 is substantially cylindrical, and is coaxial with the central axis C.

[0069] It is located inside storage volume 5, typically entirely inside storage volume 5.

[0070] An opening 49 is provided in the bottom 13 of the internal reservoir 3. An internal ring 51 is engaged in the opening 49 and rigidly fixed to the bottom 13. The external peripheral edge of the internal ring 51 is welded in a hermetic manner to the edge of the opening 49.

[0071] On a face turned towards the storage volume 5, the inner ring 51 has an external rib 53 of substantially cylindrical shape ([Fig.3]).

[0072] The external rib 53 is coaxial with the central axis C, and has substantially the same diameter as the external proximal end 29.

[0073] The external proximal end 29 is welded tightly to the external rib 53.

[0074] Similarly, the inner ring 51 has on its face facing the storage volume 5 a second rib 55, of substantially cylindrical shape ([Fig.3]).

[0075] This second rib 55 is coaxial with the central axis C, and has the same diameter as the intermediate proximal end 37.

[0076] The intermediate proximal end 37 is welded tightly to the second rib 55.

[0077] The base plate 33 seals the external distal end 31. It has a base 57 extended by a raised edge 59 welded securely to the external distal end 31.

[0078] The bottom 57 is convex towards the inside of the storage volume 5.

[0079] The annular ring 47 is coaxial with the central axis C.

[0080] It has U-shaped sections in radial planes containing the central axis C. The annular ring 47 thus has an external cylindrical wall 61 and an internal cylindrical wall 63, connected to each other by a bottom 65.

[0081] The outer wall 61 has substantially the same diameter as the intermediate distal end 39, and is welded to this intermediate distal end 39.

[0082] The internal wall 63 has substantially the same diameter as the internal proximal end 45, and is welded to it.

[0083] The intermediate tube 35 has a wall thickness of between 0.5 mm and 2.5 mm, preferably between 0.5 and 1.5 mm, and for example 1 mm.

[0084] It is made of an austenitic stainless steel having, for example, an Rp 0.2 of 270 MPa. Typically, it is made of stainless steel of grade 1.4310 or type 304.

[0085] The intermediate proximal end 37 and the intermediate distal end 39 are for example encircled by sleeves, so as to increase the rigidity respectively of the connection with the rib 55 and of the connection with the external wall 61.

[0086] Alternatively, the intermediate tube 35 is formed with a thicker wall at the intermediate proximal end 37 and at the intermediate distal end 39 than in the central part of the tube. The wall, along the central part of the tube, has the thickness indicated above.

[0087] Similarly, the inner tube 41 has a wall thickness of between 0.5 mm and 2.5 mm, preferably between 0.5 and 1.5 mm, and for example 1 mm.

[0088] It is made of an austenitic stainless steel having, for example, an Rp 0.2 of 270 MPa. Typically, it is made of stainless steel of grade 1.4310 or type 304.

[0089] The internal distal end 45 is for example encircled by a sleeve, so as to increase the rigidity of the connection with the internal wall 63.

[0090] Alternatively, the inner tube 41 is formed with a thicker wall at the distal inner end 45 than in the central part of the tube. The wall, along the central part of the tube, has the thickness indicated above.

[0091] The internal reservoir 3 further includes an orifice 79 through which the internal tube 41 is connected to the external reservoir 7.

[0092] The orifice 79 is provided in the inner ring 51.

[0093] Thus, the space delimited inside the external tube 27 is isolated from the storage volume 5 but communicates with the intermediate space 19 through the orifice 79.

[0094] The link 25 further includes a sliding link 113 linking the internal proximal end 43 to the external reservoir 7.

[0095] The sliding link 113 comprises a sliding tube 115 rigidly fixed to the external reservoir 7 and a low coefficient of friction coating 117 covering an internal surface 119 of the sliding tube 115.

[0096] The inner proximal end 43 is slidably engaged in the sliding tube 115 and slides on the low friction coefficient coating 117.

[0097] The link 25 further includes a cup 121 having a central part 123 and an edge 125 rigidly fixed to the external reservoir 7 ([Fig.1]).

[0098] The central part 123 is placed opposite the bottom 13 of the inner reservoir 3. The edge 125 is rigidly fixed to the inner surface of the outer reservoir 7. This cup 121 is for example of the type described in the application filed under number FR2211366.

[0099] The sliding tube 115 is coaxial with the central axis C.

[0100] It is rigidly fixed to the central part 123, for example by welding.

[0101] More specifically, the sliding tube 115 has a central tubular part 127 and two opposite ends 129, 131 on either side of the central tubular part 127.

[0102] The end 129 is engaged in an orifice 133 provided in the central part 123 and welded to the edge of this orifice 133.

[0103] A rib 135 is formed on the external surface of the sliding tube 115 and also welded to the central part 123.

[0104] The sliding tube 115 is engaged in the orifice 79.

[0105] The low friction coefficient coating 117 comprises a reinforcement 137, and a layer 139 of a low friction coefficient material in which the reinforcement 137 is embedded.

[0106] The frame 137 is preferably an expanded metal sheet.

[0107] The expanded metal sheet is obtained by shearing and drawing out a solid metal plate, for example in a press equipped with knives. As illustrated in [Fig. 4], the sheet has a grid of holes, which are hexagonal in the example shown. Alternatively, the holes are rhombuses, circles, squares, or any other suitable shape.

[0108] The sheet is thus in the form of a mesh, the holes being delimited by interconnected metal branches.

[0109] The metal plate, before the holes are formed, typically has a thickness of approximately 0.1 mm. The expanded metal sheet, after the holes are formed, has a thickness of approximately 0.46 mm.

[0110] As can be seen in [Fig.5], the armature 137 has a tubular shape and extends along the entire length of the sliding tube 115. In [Fig.4], it is shown developed, flat.

[0111] The low coefficient of friction material is preferably a PTFE or polytetrafluoroethylene, commonly known as Teflon ®.

[0112] Alternatively, the low coefficient of friction material is a PEEK or polyetheretherketone.

[0113] The low friction coating 117 comprises two thicknesses 141 of low friction material covering the two opposite sides of the frame 137, these two thicknesses 141 being connected to each other through the holes in the frame 137.

[0114] Typically, the reinforcement 137 is first coated with a thickness of raw, low-friction-coefficient material on each side, and then hot-calendered.

[0115] The use of expanded metal increases the adhesion of the low-friction material to the metal. The metal foil prevents the low-friction material from creeping and allows it to withstand high pressures very well.

[0116] In total, the low friction coefficient coating 117 typically has a thickness of about 1 mm.

[0117] Alternatively, the reinforcement 137 is an unexpanded metal sheet, pierced by holes allowing the attachment of the two thicknesses of low coefficient material friction, or a metal mesh, or is of any other suitable type.

[0118] The internal surface 119 of the sliding tube 115 having a central surface 143 along the central part 123 and, at both ends 129 131, end surfaces 145 flaring out from the central surface 143.

[0119] The central surface 143 is cylindrical, coaxial with the central axis C.

[0120] The end surfaces 145 are frustoconical, coaxial with the central axis C.

[0121] The low-friction coating 117 covers the central surface 143 and the end surfaces 145.

[0122] It thus comprises a cylindrical central section 147 and two flared end sections 149. The flared sections 149 are pressed against the end surfaces 145, which helps to keep the coating in place when the inner tube 41 slides inside the sliding tube 115.

[0123] The reinforcement 137 helps to keep the flared sections 149 in shape, and to ensure that they axially maintain the low friction coating 117 in position relative to the sliding tube 115, without substantial deformation of the low friction coating 117.

[0124] As seen in [Fig.3], the internal proximal end 43 has an external surface 151 having, in section in a radial plane containing the central axis C, a convex profile.

[0125] The wall of the inner tube 41 has, at the level of the inner proximal end 43, a greater thickness than in the central part of the tube.

[0126] This thickness is between 2 and 6 mm, preferably between 3 and 5 mm, and is for example 4 mm. It is taken at the top of the curved profile.

[0127] The external surface 151 thus has a general barrel shape.

[0128] This shape is obtained by varying the thickness of the wall axially along the internal proximal end 43. Starting from the central part of the internal tube 41 and moving axially along the internal proximal end 43, this thickness first increases up to the apex 153 of the curved profile, then decreases.

[0129] The radius of curvature of the curved profile is very large, for example 600 mm for a diameter of 65 mm at the level of the internal proximal end 43.

[0130] The axial length of the curved profile is large enough to distribute the contact force between the internal proximal end 43 and the sliding tube 115 over a large area.

[0131] For example, the axial length of the sliding tube 115 is 35 mm, the amplitude of the sliding of the internal proximal end 43 inside the sliding tube 115 is 9 mm, and the axial length of the curved profile is approximately 70 mm.

[0132] Advantageously, the link 25 includes a motion limiter 81, limiting a movement of the inner tube 41 relative to the inner reservoir 3, in a plane perpendicular to the central axis of the inner tube 41.

[0133] The movement limiter 81 limits the travel of the inner tube 41 to a maximum of less than 3 mm.

[0134] In the example shown, the central axis of the internal tube 41 corresponds to the central axis C. The travel of the internal tube 41 is taken at the level of the internal proximal end 43. It corresponds to the radial displacement of the internal proximal end 43 relative to its rest position.

[0135] The maximum is fixed, as indicated above, at a value less than 3 mm, typically between 1.5 and 2.5 mm, and worth for example 2 mm.

[0136] The motion limiter 81 is fixed to the internal reservoir 3.

[0137] It cooperates with the internal proximal end 43 of the internal tube 4L

[0138] The motion limiter 81 is a ring integral with the internal reservoir 3, arranged around the sliding tube 115.

[0139] For example, a radial clearance of 2 mm is provided between the movement limiter 81 and the sliding tube 115.

[0140] In this embodiment, the motion limiter 81 cooperates with the inner tube 41 to limit the movement of this inner tube, indirectly through the sliding tube 115.

[0141] The motion limiter 81 has an annular shape, centered on the central axis C.

[0142] Advantageously, it is continuous.

[0143] Alternatively, it is formed of several distinct segments, separated from each other, arranged in a ring.

[0144] The motion limiter 81 is fixed to the inner ring 51, typically on a face 111 of the inner ring 51 facing outwards from the inner reservoir 3.

[0145] The motion limiter 81 surrounds the orifice 79 and protrudes radially into the orifice 79.

[0146] The movement limiter 81 has an inner radius equal to the outer radius of the central tubular part 127 of the sliding tube 115, typically increased by 2 mm.

[0147] The motion limiter 81 is welded onto the inner ring 51 once the intermediate tube 35, the inner tube 41 and the bottom 65 are already welded to the inner ring 51.

[0148] The advantage of this solution lies in the fact that the clearance between the movement limiter 81 and the inner tube 41 is adjusted once the suspension 9 is assembled. In other words, the position of the movement limiter 81 is adjusted by knowing the position of the inner proximal end 43 of the inner tube 41 relative to the inner ring 51.

[0149] The link 25 has a thermal insulation layer 155. It is arranged between the inner tube 41 and the intermediate tube 35, typically against the inner tube 41.

[0150] It covers the internal cylindrical wall 63, and most of the internal tube 41. It stops a short distance from the sliding tube 115.

[0151] Typical mechanical stresses such as emergency braking, sharp turns, vibrations, and shocks resulting from poor road surface conditions cause displacements of the inner proximal end 43 that do not exceed 1 mm. These stresses therefore do not result in contact between the movement limiter 81 and the sliding tube 115.

[0152] Conversely, if the storage unit 1 is subjected to exceptional stress, such as in the event of an accidental vehicle impact, the inner proximal end 43 may be subjected to a much greater acceleration, potentially reaching 10 G. In this case, the movement limiter 81 comes into contact with the sliding tube 115. This will limit the deformation of the inner tube 41 and the intermediate tube 35. These tubes 41 and 35 will not undergo irreversible plastic deformation. The movement limiter 81 is sufficiently rigid to avoid deformation during such an impact.

[0153] The manufacturing process of storage unit 1 will now be described.

[0154] The process comprising the following steps: - obtaining a sub-assembly comprising the internal reservoir 3, the intermediate tube 35 fixed to the internal reservoir 3, the internal tube 41 arranged inside the intermediate tube 35, and the annular ring 47 connecting the intermediate distal end 39 to the internal distal end 45;

[0155] - obtaining the low-friction coating 117 and the neck tube lissement 115; - fixing the sliding tube 115 to the external reservoir 7; - application of the low friction coefficient coating 117 on the internal surface 119 of the sliding tube 115; - engagement of the internal proximal end 43 in a sliding manner in the sliding tube 115.

[0156] These steps are carried out successively.

[0157] The low friction coefficient coating 117 is obtained by placing a thickness 141 of raw low friction coefficient material on either side of the reinforcement 137, and by polymerizing said low friction coefficient material to obtain the layer 139 of low friction coefficient material in which the reinforcement 137 is embedded.

[0158] The polymerization of the raw low coefficient of friction material is obtained by hot calendering.

[0159] The placement of the low friction coefficient coating 117 on the internal surface 119 of the sliding tube 115 is carried out by introducing the low friction coefficient coating 117 inside the sliding tube 115 and then flaring the end sections 149 of the low friction coefficient coating 117 to press them against the two end surfaces 145.

[0160] The armature 137 has a cylindrical shape.

[0161] The low friction coefficient coating 117, after deposition of the low friction coefficient material and polymerization, also has a cylindrical shape, with a diameter slightly greater than that of the central surface 143 of the sliding tube 115.

[0162] The introduction of the low friction coefficient coating 117 inside the sliding tube 115 is achieved by splitting this coating along its entire length, tightening it to reduce its diameter, introducing it into the sliding tube 115, and then removing the stress to allow it to press against the central surface 143.

[0163] The two end sections 149 of the low friction coefficient coating 117 are then expanded to flare them out and press them against the two end surfaces 145.

[0164] The movement limiter 81 is fixed to the inner ring 51 once the intermediate tube 35, the inner tube 41 and the bottom 65 are already fixed to the inner ring 51.

[0165] The link 23 will now be described, with reference to [Fig. 6]. Only the points at which this link 23 differs from the link 25 will be detailed below. Elements identical to or performing the same function as in the link 25 will be designated by the same reference numerals.

[0166] The storage unit 1 comprises a distributor block 73 which is fixed to the internal proximal end 43 of the internal tube 41 of the linkage 23.

[0167] The distributor block 73 has at least one internal passage 74 for the cryogenic fluid.

[0168] The storage unit 1 further comprises at least one circulation tube 75 extending inside the inner tube 41 and fluidly connecting at least one internal passage 74 to the storage volume 5.

[0169] Typically, the distributor block 73 has four internal passages 74, connected to four circulation tubes 75.

[0170] In this case, one of the passages 74, and the corresponding tube 75, are provided for filling the storage volume 5. Another passage 74, and the corresponding tube 75, are provided for emptying the storage volume 5.

[0171] The two other passages 74, and the two other corresponding tubes 75, are intended to circulate the cryogenic fluid to a heat exchanger, in a loop.

[0172] The distributor block 73 is placed axially in the extension of the internal tube 41.

[0173] It has, towards the inner tube 41, a substantially cylindrical end part 76.

[0174] The end part 76 is coaxial with the central axis C. It is delimited radially outwards by an external surface 77, and axially towards the internal tube 41 by a connecting surface 78.

[0175] The external surface 77 is substantially cylindrical. It has a cross-section perpendicular to the central axis C substantially identical to that of the internal proximal end 43.

[0176] The link 23 includes another cup 83 with another central part 84 placed opposite the bottom 13 of the inner reservoir 3 and another edge 85 rigidly fixed to the inner surface of the outer reservoir 7. This cup is for example of the type described in the application filed under number FR2211366.

[0177] The other central part 84 of the other cup 83 is oriented substantially perpendicular to the central axis C. It has another central orifice 86, through which the distribution block 73 passes.

[0178] The motion limiter 81 is fixed to the internal reservoir 3, as for the link 25.

[0179] It cooperates with the internal proximal end 43 of the internal tube 4L

[0180] Alternatively, it cooperates with the distributor block 73, or it cooperates with both the internal proximal end 43 and the distributing block 73.

[0181] To do this, the internal proximal end 43 covers the external surface 77 of the distributing block 73. More precisely, it covers the part of the external surface 77 located towards the internal reservoir 3.

[0182] The internal proximal end 43 is rigidly fixed to the distributor block 73, by any suitable means, for example by welding.

[0183] The end portion 76 of the distributing block 73 is engaged in the internal proximal end 43.

[0184] The other central part 84 of the other cup 83 is rigidly fixed directly to the internal proximal end 43.

[0185] The internal proximal end 43 is engaged through the other central orifice 86 of the other cup 83 and is welded to the edge of said orifice 86.

[0186] Each internal passage 74 has, at one end, a counterbore 93 formed in the connecting surface 78. A connecting sleeve 95 is rigidly fixed in this counterbore 93. The corresponding circulation tube 75 is rigidly fixed by one of its ends, in a watertight manner, to the connecting sleeve 95.

[0187] Furthermore, each circulation tube 75 is connected to the bottom plate 33 and communicates with the storage volume 5 through the bottom plate 33.

[0188] To do this, the base plate 33 has orifices 97, into which other connecting sleeves 99 are engaged. Each circulation tube 75 is rigidly fixed, in a watertight manner, to one of the other connecting sleeves 99.

[0189] Each circulation tube 75 has a wall thickness of between 0.1 and 0.6 mm, preferably between 0.2 and 0.4 mm, and for example 0.3 mm. These circulation tubes 75 are typically made of 316L type stainless steel.

[0190] The circulation tubes 75 are straight and parallel to the central axis C.

[0191] The connection 23 further includes an external thermal insulation 107, arranged between the intermediate tube 35 and the external tube 27.

[0192] This external thermal insulation 107 extends from the intermediate distal end 39 over a length less than 75% of the total length of the intermediate tube 35.

[0193] The external thermal insulation 107 is typically of the same type as the thermal insulation 21. It comprises a plurality of metallic or plastic sheets (for example of PET or polyethylene terephthalate, PA or polyamide, PEEK or aluminized polyetheretherketone) superimposed one on the other, with interposed layers of fibers.

[0194] The external thermal insulation 107 is preferably attached to the intermediate tube 35. It covers the weld joining the intermediate distal end 39 to the annular ring 47. It also covers the radially external surface of this annular ring 47. The external thermal insulation 107 extends over approximately 50% of the total length of the intermediate tube 35.

[0195] The connection 23 further includes internal thermal insulation 109, arranged between the intermediate tube 35 and the inner tube 4L

[0196] This internal thermal insulation 109 extends from the internal proximal end 43 over a length less than 75% of the total length of the internal tube 4L

[0197] The internal thermal insulation 109 is of the same type as the thermal insulation 21. It comprises a plurality of metal or plastic (e.g., PET, PA, PEEK) aluminized sheets layered one on top of the other, with interposed layers of fibers. It is pressed against the internal tube 4L

[0198] The internal thermal insulation 109 does not cover the weld connecting the inner proximal end 43 to the distribution block 73 or the movement limiter 81. It begins a short distance from the connecting weld. It typically extends over approximately two-thirds of the total length of the inner tube 4L

[0199] It should be noted that there is an axial overlap between the external thermal insulation 107 and the internal thermal insulation 109, as illustrated in [Fig.2].

[0200] It should be noted that the external thermal insulation 107 only covers the area of ​​the intermediate tube 35 where the temperature difference between the intermediate tube 35 and the tube The external tube 27 is the most important. Indeed, the external tube 27 is at the temperature of the cryogenic fluid, that is, approximately 20 K in the case of liquid hydrogen. The temperature of the intermediate tube 35 varies between 50 K at the proximal end of the intermediate tube 37 and 130 K at the distal end of the intermediate tube 39. The temperature difference is therefore greater near the distal end of the intermediate tube 39. Consequently, the radiation from the intermediate tube 35 onto the external tube 27 is greater at this point. Implementing thermal insulation on this portion of the intermediate tube 35 thus allows for a very effective limitation of heat transfer by radiation, without excessively increasing the cost.

[0201] The internal thermal insulation 109 is also placed in the area where the temperature difference between the inner tube 41 and the intermediate tube 35 is greatest.

[0202] According to an unshown variant, the motion limiter 81 cooperates with the orifice 79 to limit the travel of the inner tube 4L

[0203] In this case, the movement limiter 81 is rigidly fixed to the distributor block 73.

[0204] Alternatively, it is fixed to the inner tube 41, typically to the inner proximal end 43, or it is fixed to both the distributor block 73 and the inner tube 4L.

[0205] In this case, the movement limiter 81 is a sleeve arranged around the inner proximal end 43. The radial distance between the movement limiter 81 and the inner surface of the orifice 79 thus corresponds to the maximum travel of the inner tube 4L.

[0206] The storage unit described above has multiple advantages.

[0207] When the low friction coefficient coating comprises a reinforcement and a layer of a low friction coefficient material in which the reinforcement is embedded, the low friction coefficient material will not flow under the effect of the displacement of the inner tube relative to the sliding tube, and the coating can withstand significant pressures.

[0208] The use of an expanded metal sheet as reinforcement increases the adhesion of the low-friction material to the reinforcement, with a particularly low thickness requirement.

[0209] Using PTFE or PEEK as a low coefficient of friction material is particularly suitable.

[0210] When the sliding tube has a central tubular portion and two opposite ends on either side of the central tubular portion, the internal surface having a central surface along the central portion and, at both ends, end surfaces flaring out from the central surface, the low-friction coating covering the central surface and the end surfaces, then the low-friction coating is well held in position on the tube. sliding.

[0211] When the inner tube has a central axis, and the inner proximal end has an external surface with a convex profile in cross-section in a radial plane containing the central axis, then the inner proximal end can be slightly offset from the sliding tube. This allows for a slight misalignment of the inner tube and the sliding tube.

[0212] When the connection comprises an outer tube having an external proximal end fixed to the inner reservoir and an external distal end located inside the storage volume, and a bottom plate closing the external distal end, with the intermediate tube arranged inside the outer tube, then the intermediate tube and the inner tube are isolated from the cryogenic fluid filling the inner reservoir. Heat losses by conduction along the connection are particularly low.

[0213] When the connection includes a motion limiter, restricting the movement of the inner tube relative to the inner tank in a plane perpendicular to the central axis of the inner tube, then it is possible to choose thin wall thicknesses for the suspension, particularly for the intermediate tube and the inner tube. These wall thicknesses are chosen to allow the tubes to withstand the usual mechanical stresses corresponding to normal use of the storage unit. When the storage unit is installed in a motor vehicle, these stresses result, for example, from emergency braking, a hairpin turn, or vibrations generated by the vehicle rolling on a rough road.Conversely, in the event that the storage unit is subjected to exceptional stress such as an accidental impact, the movement limiter restricts the movement of the inner tube in a plane perpendicular to its central axis. This limits the deformation of the intermediate tube and the inner tube, preventing them from entering their plastic deformation range and thus from undergoing irreversible damage.

[0214] It is particularly convenient and economical to make the motion limiter in the form of a ring attached to the internal reservoir, arranged around the sliding tube.

[0215] The storage unit may have multiple variants.

[0216] The connection may not include an external tube, the intermediate tube then being in direct contact with the cryogenic fluid. In this case, the connection includes a plate sealing the intermediate distal end.

[0217] The link may not include a motion limiter, limiting the movement of the inner tube relative to the inner reservoir.

Claims

Demands

1. Cryogenic fluid storage unit (1), comprising an internal reservoir (3) internally delimiting a cryogenic fluid storage volume (5), an external reservoir (7) in which the internal reservoir (3) is housed and a suspension (9) fixing the internal reservoir (3) to the external reservoir (7), the suspension (9) comprising a link (25) having: - an intermediate tube (35) having an intermediate proximal end (37) fixed to the internal reservoir (3) and an intermediate distal end (39), - an internal tube (41) arranged inside the intermediate tube (35), having an internal proximal end (43) and an internal distal end (45), - an annular ring (47) connecting the intermediate distal end (39) to the internal distal end (45);- a sliding link (113) from the inner proximal end (43) to the outer reservoir (7), comprising a sliding tube (115) rigidly fixed to the outer reservoir (7) and a low coefficient of friction coating (117) covering an inner surface (119) of the sliding tube (115), the inner proximal end (43) being slidably engaged in the sliding tube (115) and sliding on the low coefficient of friction coating (117).

2. Storage unit according to claim 1, in which the low friction coefficient coating (117) comprises a reinforcement (137), for example an expanded metal sheet, and a layer of a low friction coefficient material (139) in which the reinforcement (137) is embedded.

3. Storage unit according to claim 2, wherein the low coefficient of friction material is a PTFE or a PEEK.

4. A storage unit according to any one of claims 1 to 3, wherein the sliding tube (115) has a central tubular portion (127) and two opposing ends (129, 131) on either side of the central tubular portion (127), the inner surface (119) having a central surface (143) along the central portion (127) and, at both ends (129, 131), end surfaces (145) flaring out from the central surface (143), the low-friction coating (117) covering the central surface (143) and the end surfaces (145).

5. Storage unit according to any one of claims 1 to 4, wherein the inner tube (41) has a central axis (C), the inner proximal end (43) having an external surface (151) having, in section in a radial plane containing the central axis (C), a convex profile.

6. Storage unit according to any one of claims 1 to 4, wherein the connection (25) comprises: - an outer tube (27) having an external proximal end (29) fixed to the inner reservoir (3) and an external distal end (31) located inside the storage volume (5); - a bottom plate (33) closing the external distal end (31); the intermediate tube (35) being arranged inside the outer tube (27).

7. Storage unit according to any one of claims 1 to 6, wherein the linkage (25) includes a motion limiter (81), limiting a deflection of the inner tube (41) relative to the inner reservoir (3) in a plane perpendicular to the central axis (C) of the inner tube (41).

8. Storage unit according to claim 7, wherein the motion limiter (81) is a ring integral with the internal reservoir (3), arranged around the sliding tube (115).

9. A method for manufacturing a storage unit according to any one of claims 1 to 8, the method comprising the following steps: - obtaining a subassembly comprising the inner reservoir (3), the intermediate tube (35) fixed to the inner reservoir (3), the inner tube (41) arranged inside the intermediate tube (35), and the annular ring (47) connecting the intermediate distal end (39) to the inner distal end (45); - obtaining the low-friction coating (117) and the sliding tube (115); - fixing the sliding tube (115) to the outer reservoir (7); - applying the low-friction coating (117) to the inner surface (119) of the sliding tube (115); - sliding the inner proximal end (43) into the sliding tube (115);the low friction coating (117) being obtained by placing a thickness (141) of a raw low friction material on either side of a reinforcement (137), and by polymerizing said low friction material to obtain a layer; material with low coefficient of friction (139) in which the reinforcement (137) is embedded.

10. A method according to claim 9, wherein the sliding tube (115) has a central tubular portion (127) and two opposing ends (129, 131) on either side of the central tubular portion (127), the inner surface (119) of the sliding tube (115) having a central surface (143) along the central portion (123) and, at both ends (129, 131), end surfaces (145) flaring out from the central surface (143), the application of the low-friction coating (117) to the inner surface (119) of the sliding tube (115) being achieved by introducing the low-friction coating (117) inside the sliding tube (115) and then flaring out sections of the end surfaces (149) of the low-friction coating (117) to press them against the two end surfaces (145).

Images