Fuel cell

Abstract

The invention relates to a fuel cell. The fuel cell (10) comprises a housing, a stack of electrochemical cells, a fixed end plate and a movable end plate (16) clamping the stack therebetween, and a guide system (30) guiding the movable end plate limiting a displacement of the movable end plate perpendicular to the stacking direction (X). In order to control the positioning of the movable end plate, the guide system comprises at least one compression member (32) exerting a compression force (E32) on the movable end plate in a compression direction (Y); two guide members (36A, 36B) fixed to the movable end plate; and two inclined supports (38A, 38B) fixed to the housing, extending parallel to the stacking direction and inclined with respect to the compression direction and the centering direction (Z). Under the action of a compressive force, the guide member is supported against the tilting support and centring the movable end plate relative to the housing parallel to the centring direction.

Description

[0001] The present invention relates to a fuel cell.

[0002] In the field of fuel cells, it is known to sandwich a stack of electrochemical cells between two end plates located on either side of the stack in the stacking direction and to protect the assembly in a housing. The end plates serve both to keep the stack in a compressed state and to accommodate connectors required for the operation of the fuel cell, such as inlets.

[0003] During operation, due to aging and thermal effects, the stack of electrochemical cells tends to expand in the stacking direction. To allow this expansion to occur without damaging the electrochemical cells, it is known to fix the first end plate relative to the housing and to make the second end plate movable relative to the housing parallel to the stacking direction. In this way, the second end plate can move due to the expansion of the stack, and the compression of the stack does not increase due to the expansion of the stack beyond a tolerance threshold.

[0004] It is known to use a guiding system to allow the displacement of the movable end plate parallel to the stacking direction and to prevent its displacement perpendicular to the stacking direction. However, the known guiding systems are generally not satisfactory.

[0005] For example, US-A-2009 / 0004533 describes a fuel cell in which the movable end plate is guided in its movement parallel to the stacking direction by a guiding shaft extending through an opening in the housing, and in which the movement of the movable end plate perpendicular to the stacking direction is prevented by direct contact of the end plate with the housing wall. The guiding of the guiding shaft is hyperstatic, resulting in a risk of jamming of the movable end plate and making the fuel cell assembly more complex. In addition, in such a fuel cell, an operating clearance needs to be provided between the movable end plate and the housing wall, in other words, an empty space between the movable end plate and the housing wall that allows the movable end plate to move parallel to the stacking direction without the risk of jamming or bending against the housing wall. However, the presence of such an operating clearance allows the movable end plate and the electrochemical cells to vibrate freely perpendicular to the stacking direction. Such vibrations are detrimental to the service life of the electrochemical cells.

[0006] CN-A-112993368 gives another example of guiding a movable end plate. In a first direction perpendicular to the stacking direction, the movable end plate is guided by runners arranged on both sides of the movable end plate and bearing against the housing wall. In addition, tracks are arranged on four sides of the end plate and cooperate with spring-mounted jumpers connected to the housing wall to limit the displacement of the movable end plate in the first direction and in a second direction perpendicular to the stacking direction and the first direction. Since the jumpers are spring-mounted, this method, in addition to being complex and bulky to implement, also allows lateral displacement of the movable end plate parallel to the second direction. Therefore, this fuel cell cannot prevent vibration of the movable end plate and thus cannot prevent vibration of the electrochemical cell in the second direction, which is detrimental to the life of the electrochemical cell.

[0007] US-A-2018 / 0241050, EP-A-3018748 and US-A-2009 / 280388 describe further examples of guiding systems for movable end plates of fuel cells.

[0008] The present invention more particularly aims to remedy these drawbacks by proposing a fuel cell that allows displacement of the movable end plate parallel to the stacking direction while controlling the position of the end plate perpendicular to the stacking direction.

[0009] To this end, the present invention relates to a battery comprising:

[0010] - a housing,

[0011] - a stack of electrochemical cells extending in a stacking direction,

[0012] - a fixed end plate arranged at a first end of the stack and fixed relative to the housing,

[0013] - a movable end plate arranged at a second end of the stack and movable relative to the housing parallel to the stacking direction, the fixed end plate and the movable end plate clamping the stack therebetween, and

[0014] - a guiding system for the movable end plate configured to allow displacement of the movable end plate parallel to the stacking direction and to limit displacement of the movable end plate perpendicular to the stacking direction,

[0015] According to the invention, the guiding system for the movable end plate comprises:

[0016] - at least one compression member applying a compression force to the movable end plate relative to the housing in a compression direction perpendicular to the stacking direction,

[0017] - two guiding members fixed relative to a first element among the housing and the movable end plate, and

[0018] - Two tilting supports, which are fixed relative to a second element in a housing and a movable end plate different from the first element, extend parallel to the stacking direction, each tilting support being tilted relative to the compression direction and tilted relative to a centering direction perpendicular to the stacking direction and the compression direction.

[0019] Furthermore, under the action of the compression force applied by the compression member, each guiding member bears against one of the two tilting supports, and the two guiding members center the movable end plate relative to the housing parallel to the centering direction.

[0020] Due to the present invention, the position of the movable end plate perpendicular to the stacking direction is constrained by the guiding member, which introduces a support against the tilting support through the compression member. The tilting support is tilted relative to the direction of the applied compression force, which allows the tilting support to both prevent displacement of the movable end plate in the compression direction and center the movable end plate in the centering direction.

[0021] According to an advantageous but non - mandatory aspect of the present invention, the fuel cell incorporates one or more of the following features, which can be used alone or in any technically allowable combination:

[0022] - Under the action of the compression force applied by the compression member, the first guiding member tends to displace the movable end plate in the centering direction, and the second guiding member tends to displace the end plate in a direction relative to the centering direction.

[0023] - Each tilting support is formed by the surface of a track extending parallel to the stacking direction.

[0024] - Each tilting support is tilted at an angle between 30° and 60° relative to the compression direction, preferably equal to 45°.

[0025] - The guiding members are runners, the profile of which is complementary to the profile of the tilting support.

[0026] - The compression member is an elastically deformable blade.

[0027] - The elastically deformable blade has two ends and a central portion, the two ends of the elastically deformable blade being connected to the first element, and the central portion of the elastically deformable blade bearing against the second element.

[0028] - The elastically deformable blade extends in a direction parallel to the stacking direction, the guiding system includes two fixing members, and each fixing member connects one end of the elastically deformable blade to the first element, allowing displacement of this end parallel to the stacking direction and preventing displacement of this end perpendicular to the stacking direction.

[0029] - The support of the first guiding member generates a first reaction force on the first inclined support, and the support of the second guiding member generates a second reaction force on the second inclined support. The first reaction force and the second reaction force each have a first component oriented parallel to the compression direction and a second component oriented parallel to the centering direction. The first components of the first reaction force and the second reaction force have equal magnitudes and directions, and have a direction opposite to the direction of the compression force. And wherein the second components of the first reaction force and the second reaction force have equal magnitudes and opposite directions.

[0030] - The guiding system further includes two lateral compression members. The first lateral compression member applies a compression force on the movable end plate relative to the housing along the centering direction (Z), and the second lateral compression member applies a compression force on the movable end plate relative to the housing along a direction relative to the centering direction.

[0031] - The fuel cell further includes a clamping system that applies a clamping force on the movable end plate relative to the housing parallel to the stacking direction (X), tending to compress the stack of electrochemical cells.

[0032] According to the following description of a fuel cell embodiment given only by way of example, based on its principle and with reference to the drawings, the present invention will be better understood, and other advantages of the present invention will become more apparent, wherein:

[0033] Figure 1 Figure 1 is a perspective view of a fuel cell according to the present invention;

[0034] Figure 2 Figure 2 is similar to Figure 1 in view, where the housing of the fuel cell is not shown;

[0035] Figure 3 Figure 3 is Figure 1 a front view of the fuel cell; and

[0036] Figure 4 Figure 4 is Figure 3 a cross-section of the fuel cell in

[0037] The fuel cell 10 can be seen in Figures 1 to 4 For example, the fuel cell 10 is intended to be integrated into a vehicle having an electric motor to generate electrical energy that allows the engine to operate, possibly operating entirely or in part through a storage battery.

[0038] ​​​​​​​​The fuel cell 10 includes a stack 12 of electrochemical cells, which is not shown separately for the sake of simplicity. Each electrochemical cell generally consists of an anode and a cathode, which are separated by a polymer membrane that allows protons to pass from the anode to the cathode. The anode supplies fuel, such as dihydrogen, and the cathode supplies an oxidant, such as oxygen or air.

[0039] The electrochemical cells are stacked in a stack direction X to form the stack 12. The stack direction X is the length direction of the stack 12, in other words, the longitudinal direction of the stack. Preferably, the stack direction X is horizontal when the fuel cell 10 is operating (e.g., in a vehicle).

[0040] In the present invention, the term direction is used as the orientation direction of a straight line in a plane. In other words, the direction corresponds to an oriented straight line and thus to the direction of travel along this line.

[0041] The fuel cell 10 includes a fixed end plate 14 and a movable end plate 16, which are arranged on both sides of the stack 12 along the stack direction X. In this example, the stack direction X is oriented to extend from the fixed end plate 14 towards the movable end plate 16. In practice, the fixed end plate 14 and the movable end plate 16 extend perpendicular to the stack direction X.

[0042] In practice, the fixed end plate 14 is arranged at the first end 12A of the stack 12, and the movable end plate 16 is arranged at the second end 12B of the stack, which corresponds to the free end of the stack. In other words, the movable end plate 16 forms the free end of the assembly formed by the fixed end plate, the movable end plate, and the stack 12.

[0043] Preferably, the fixed end plate 14 includes a connector (not shown) that is arranged to connect to a fluid circulation pipe, thereby allowing the supply of fuel and oxidant gas to the stack 12 and possibly the supply of a cooling fluid. In a manner known per se, other elements can be inserted between each of the end plates 14, 16 and the stack. By way of non-limiting example, these elements can include, for example, current collector plates and / or insulating plates.

[0044] The fuel cell 10 includes a housing 18 that surrounds and protects the stack 12 of electrochemical cells. In practice, the housing 18 includes a base 20 and side walls 22. Herein, the base 20 is perpendicular to the stack direction X, and the side walls 22 extend parallel to the stack direction X.

[0045] In practice, the fixed end plate 14 is fixed to the housing 18, more precisely to the base 20 of the housing, and the movable end plate 16 is movable in the housing between the side walls 22 parallel to the stacking direction X, as described below. Thus, the base 20 of the housing and the fixed end plate 14 form a rigid assembly. In this example, the base of the housing and the fixed end plate are two separate parts rigidly connected to each other. In an alternative embodiment (not shown) of the present invention, the base of the housing and the fixed end plate are formed as a single piece, in which case the two are combined.

[0046] The fuel cell 10 includes a clamping system 24 that applies a clamping force E24 to the movable end plate 16 relative to the housing 18. The clamping force E24 is parallel to the stacking direction X and opposite to the stacking direction X, which is the longitudinal direction of the stack. Thus, the clamping force E24 is a longitudinal compressive force applied to the movable end plate 16. Therefore, the longitudinal direction X is the clamping direction of the stack 12. The clamping system 24 tends to move the movable end plate 16 closer to the fixed end plate 14, thereby compressing the stack 12 between the fixed end plate and the movable end plate. In other words, the fixed end plate and the movable end plate clamp the stack 12 between them under the action of the clamping force E24. Compression of the stack 12 between the fixed end plate 14 and the movable end plate 16 ensures optimal operation of the electrochemical cells and thus optimal operation of the fuel cell 10.

[0047] In this example, the clamping system 24 includes a clamping flange 26 and compression springs 28 arranged between the clamping flange 26 and the movable end plate 16, for example four or nine compression springs. The compression springs 28 are compressed so as to apply a clamping force E24 to the movable end plate 16 relative to the clamping flange 26, thereby compressing the stack 12. Here, the clamping flange 26 is fixed relative to the housing 18, for example fixed to the side walls 22 by means of fixing means (not shown). For simplicity, the compression springs 28 are only shown in Figure 4 The clamping force E24 is divided into several elementary forces, each force being applied by a compression spring, two of which are as shown in Figure 4 shown.

[0048] Other designs of the clamping system 24 are possible. According to a first alternative (not shown), the clamping flange 26 may not be fixed to the side walls 22 of the housing 18, but may be connected to the base 20 of the housing by a tie rod, allowing displacement of the clamping flange perpendicular to the stacking direction X while preventing displacement of the clamping flange parallel to the stacking direction X. In addition, in the case of applying high thermal stress to the fuel cell 10, the tie rod may also tend to expand along the stacking direction X, causing displacement of the clamping flange 26 along the stacking direction X.

[0049] According to an alternative not shown, the clamping system 24 includes a tension spring instead of a clamping flange and a compression spring, which is fixed on the one hand to the base 20 of the housing 18 and on the other hand to the movable end plate 16.

[0050] During the life of the fuel cell 10, the stack 12 of electrochemical cells tends to expand and / or contract parallel to the stack direction X. This change in the length of the stack 12 is caused by, for example, the aging of the electrochemical cells, the accumulation of fluid pressure in the channels of the electrochemical cells of the stack 12, or thermal effects. In practice, as shown by L12, the dimensional change of the stack 12 is small relative to the length of the stack. Thus, the maximum dimensional change of the stack 12, for example, is equal to a percentage in the range of 0.5% to 2% of the stack length L12. For example, for a stack 12 having a length L12 of approximately 400 mm measured along the stack direction X, the maximum dimensional change of the stack during its life is approximately a few millimeters, for example 4 mm.

[0051] Since the end plate 14 is fixed relative to the housing 18, any change in the length of the stack 12 will cause a displacement of the movable end plate 16 parallel to the stack direction X.

[0052] For example, in practice, the size of the compression spring 28 is designed to absorb the maximum dimensional change of the stack 12 while maintaining a clamping force that varies sufficiently little, regardless of the expansion or contraction of the stack, to remain within the stack clamping force tolerance.

[0053] To allow displacement of the movable end plate 16 parallel to the stack direction X while restricting displacement of the movable end plate perpendicular to the stack direction, the fuel cell 10 includes a guiding system 30.

[0054] The transverse direction Y of the fuel cell 10 is defined as the direction perpendicular to the stack direction X, and the centering direction Z of the fuel cell is defined as the direction perpendicular to the stack direction X and the transverse direction Y. Preferably, when the fuel cell 10 is operating (e.g., in a vehicle), the stack direction X is horizontal, the transverse direction Y is vertical, and advantageously downwardly oriented, and the centering direction Z is horizontal. Here, from Figure 3 the perspective, the centering direction Z is arbitrarily defined as being oriented from left to right, and the directions X, Y, and Z are the directions of the axes of an orthogonal reference system.

[0055] The guiding system 30 includes at least one compression member 32 that applies a compression force E32 to the movable end plate 16 in the transverse direction Y relative to the housing 18. Thus, the transverse direction is the compression direction of the movable end plate 16, perpendicular to the compression direction X of the stack 12. In other words, the compression force E32 is transverse to the stack 12.

[0056] In the example, the guiding system 30 includes two compression members 32, each compression member applying a compression force E32 on the movable end plate 16. Alternatively, the guiding system 30 includes a different number of compression members 32, such as a single compression member or three compression members.

[0057] For example, the compression member 32 is in the form of an elastically deformable blade, a part of which (e.g., one end) is fixed to one of the housing 18 and the movable end plate 16, and a part of which is supported against the other of the housing and the movable end plate. Herein, the compression member 32 is an elastically deformable blade. In this example, each elastically deformable blade 32 has a first end 32A, a second end 32B, and a central portion 32C. Each elastically deformable blade 32 extends in a direction A32 that is generally parallel to the stacking direction X, and presents a hemispherical profile along the compression direction Y. In other words, along the compression direction Y of the movable end plate 16, the first end 32A is aligned with the second end 32B, but the central portion 32C is not aligned with the first end 32A and the second end 32B. For one of the two elastically deformable blades 32, the direction A32 is only shown in Figure 2 is shown.

[0058] In this example, the elastically deformable blade 32 is a deformable metal blade. Alternatively, the elastically deformable blade can be made of another material, such as made of a polymer or a composite material.

[0059] In this example, the first end 32A and the second end 32B are connected to the housing 18, and in practice, are connected to one of the side walls 22 of the housing, and the central portion 32C is supported against the movable end plate 16.

[0060] In practice, the guiding system 30 includes two fixing members 34 for each metal blade 32. Preferably, each fixing member 34 connects one of the two ends 32A, 32B of the metal blade 32 to the housing 18 to allow the displacement of this end parallel to the stacking direction X, while preventing the displacement of this end perpendicular to the stacking direction X.

[0061] In the present text, each fixing member 34 includes a retaining plate 34A and two retaining elements 34B. The retaining plate 34A extends parallel to the side wall 22 of the housing 18 to which the ends of the metal vanes are connected, in other words, it extends parallel to the centering direction Z and the stacking direction X, and is fixed to the side wall of the housing by two retaining elements 34B which, in this example, are screws. The two screws 34B are aligned along the stacking direction X and offset from each other parallel to the centering direction Z. When the fuel cell 10 is assembled, each end 32A, 32B of each metal vane 32 is arranged between the side wall 22 of the housing 18 and the retaining plate 34A of the fixing member 34 parallel to the compression direction Y, and between the two screws 34B of the fixing member 34 parallel to the centering direction Z. Thus, displacement of each end of each metal vane parallel to the compression direction Y and the centering direction Z is prevented.

[0062] Furthermore, the fixing member 34 allows displacement of the metal vanes 32 parallel to the stacking direction X. In practice, due to the hemispherical shape of the metal vanes, the allowed displacement of the metal vanes 32 parallel to the stacking direction X is small because in the case of too large a displacement, the metal vanes would come into contact with the retaining plate 34A of one of the fixing members 34, thus preventing further displacement of the metal vanes.

[0063] Alternatively, each fixing member 34 fixes one of the two ends 32A, 32B of the metal vane 32 to the housing 18, preventing displacement of this end in any of the three directions X, Y and Z.

[0064] When the fuel cell 10 is assembled, each metal vane 32 is constrained between the housing 18 and the movable end plate 16, in other words, each metal vane is elastically deformed to be positioned between the housing and the end plate. This constraint of the metal vanes 32 is facilitated by the ability of the ends 32A and 32B of the metal vanes to displace parallel to the stacking direction X. In practice, the constraint of the metal vanes 32 generates reaction forces on the housing 18 and the movable end plate 16 and thus generates a compression force E32. Thus, the metal vanes 32 act as compression springs.

[0065] Preferably, within the manufacturing and assembly tolerances, all the compression forces E32 exerted by the metal vanes 32 are the same.

[0066] It is advantageous to apply a compression force E32 to the movable end plate 16 using the metal blades 32 because the metal blades elongate in the direction of movement of the movable end plate (in other words, parallel to the stacking direction X). Thus, within the limits of the expansion amplitude of the stack 12, the metal blades 32, more specifically their central portions 32C, remain in contact with the movable end plate 16, regardless of the position of the movable end plate 16 along the stacking direction X. Thus, throughout the life of the fuel cell 10, the compression force E32 remains on the movable end plate 16.

[0067] In an alternative, not shown, of the present invention, the metal blades 32 are reversed, in other words, their ends 32A, 32B are fixed to the movable end plate 16 and their central portions 32C bear against the housing 18. Preferably, in this alternative, the movable end plate 16 includes a skirt extending parallel to the stacking direction X, which allows the two ends of the metal blades to be connected thereto.

[0068] In an alternative, not shown, of the present invention, other compression members such as coil springs or Belleville washers (referred to as "Belleville washers") are used instead of the metal blades. Each compression member can also be formed by a compression member comprising one or more coil springs and / or one or more Belleville washers, in combination with a deformable blade, in particular with a deformable blade as described above, or in combination with a hinged blade, one end of the blade being fixed to one of the housing 18 and the movable end plate 16, a part of which is supported on the other of the housing and the movable end plate, and the other part serving as a support for one or more coil springs and / or one or more Belleville washers.

[0069] The guiding system 30 also includes two guiding members 36A, 36B and two inclined supports 38A, 38B extending parallel to the stacking direction X.

[0070] In this example, the guiding members 36A, 36B are fixed to the movable end plate 16 opposite the metal blades 32 in the compression direction Y. In other words, the metal blades 32 and the guiding members 36A and 36B are located at two opposite edges of the end plate 16. Furthermore, the guiding members 36A and 36B are preferably arranged symmetrically with respect to each other with respect to the cross-section IV, which is the mid-plane of the fuel cell parallel to the directions X and Y.

[0071] In this example, the tilting supports 38A and 38B are fixed to the housing 18, more precisely to the side wall 22 of the housing opposite the side wall to which the metal blade 32 is connected. Thus, in an example where the stacking direction is horizontal and the compression direction is vertical and downward, the tilting supports 38A and 38B are located below the movable end plate 16. In practice, the tilting supports 38A and 38B are inclined with respect to the compression direction Y and with respect to the centering direction Z. In other words, the straight line orthogonal to the tilting supports 38A and 38B intersects the compression direction Y and the centering direction Z. Moreover, the tilting support 38A is symmetric with respect to the compression direction Y with respect to the tilting support 38B, such that the line orthogonal to the tilting support 38A is perpendicular to the line orthogonal to the tilting support 38B.

[0072] When the fuel cell 10 is assembled, under the action of the compression force E32 generated by the metal blade 32, which causes a displacement of the end plate 16 in the compression direction Y, the guiding member 36A bears against the tilting support 38A and the guiding member 36B bears against the tilting support 38B. Thus, the tilting support 38A exerts a reaction force F1 on the guiding member 36A in a direction perpendicular to the tilting support 38A, and the tilting support 38B exerts a reaction force F2 on the guiding member 36B in a direction perpendicular to the tilting support 38A.

[0073] The reaction forces F1 and F2 are perpendicular to the stacking direction X and inclined with respect to the compression direction Y and the centering direction Z. Moreover, the reaction force F1 is symmetric with respect to the compression direction Y with respect to the reaction force F2. In other words, each of the reaction forces F1 and F2 has a first component with a direction parallel to the compression direction Y and a second component with a direction parallel to the centering direction Z, the first components of the reaction forces F1 and F2 have equal intensities and orientations, and the second components of the reaction forces F1 and F2 have equal intensities and opposite orientations.

[0074] Thus, it can be understood that the reaction force F1 tends to displace the movable end plate 16 in the centering direction Z, and the reaction force F2 tends to displace the movable end plate 16 in the direction opposite to the centering direction Z. These two opposite forces center the movable end plate 16 parallel to the centering direction Z with respect to the tilting supports 38A, 38B. Advantageously, the tilting supports 38A and 38B are themselves centered with respect to the fixed end plate 14. Under the action of the reaction forces F1 and F2, the movable end plate 16 is centered with respect to the fixed end plate 14 parallel to the centering direction Z.

[0075] Moreover, and in a particularly advantageous manner, the tilting supports 38A and 38B converge away from the wall 22 of the housing 18 to which the metal blade 32 is connected, in other words, the normal vectors of the tilting support 38A and the tilting support 38B converge towards each other. Thus, the second components of the reaction forces F1 and F2 converge. Thus, the centering of the movable end plate 16 is improved.

[0076] In an alternative, not shown, of the present invention, the inclined supports 38A and 38B diverge from the wall 22 of the housing 18 to which the metal blade 32 is connected. In other words, the normal vectors of the inclined support 38A and the inclined support 38B diverge from each other, and the second components of the reaction forces F1 and F2 diverge.

[0077] Furthermore, the sum of the compression force E32 and the reaction forces F1 and F2 is zero. Thus, once the guiding members 36A, 36B are pressed by the compression member against the two inclined supports 38A, 38B, these forces do not cause any displacement of the movable end plate 16 perpendicular to the stacking direction X relative to the housing 18. In other words, the compression force E32 and the reaction forces F1 and F2 limit the position of the movable end plate 16 perpendicular to the stacking direction X relative to the housing 18.

[0078] Thus, in a particularly advantageous manner, the compression force E32 and the reaction forces F1, F2 limit the position of the movable end plate 16 parallel to the compression direction Y in order to press the guiding members 36A, 36B against the inclined supports 38A, 38B, in other words, by displacing the movable end plate 16 as much as possible in the compression direction Y. Similarly, the compression force E32 and the reaction forces F1, F2 limit the position of the movable end plate 16 parallel to the centering direction Z, centering the movable end plate relative to the fixed end plate 14, in other words, relative to the housing 18.

[0079] The support of the movable end plate 16 in the direction Y and this centering of the movable end plate relative to the housing 18 and thus relative to the fixed end plate 14 parallel to the centering direction Z are particularly advantageous for avoiding deformation of the stack 12 and vibrations that could damage the electrochemical cells of the stack 12. This increases the service life of the fuel cell 10.

[0080] In practice, due to the guiding members 36A, 36B bearing against the inclined supports 38A, 38B, the guiding system 30 limits any displacement of the movable end plate 16 in the compression direction Y and parallel to the centering direction Z. Furthermore, since the compression force E32 and the reaction forces F1, F2 are perpendicular to the stacking direction X, the guiding system 30 does not impede the displacement of the movable side plate parallel to the stacking direction X.

[0081] Furthermore, due to the compression force E32 generated by the metal blade 32, the guiding system 30 limits the movable end plate 16 in the direction opposite to the compression force E32 (in other words, in the direction opposite to the compression direction Y, in other words, in Figure 3Any displacement in the upward direction (in the example of ) is not possible. Therefore, a displacement of the movable end plate 16 in the direction opposite to the compression direction Y is theoretically possible, but this displacement must be caused by a force acting on the movable end plate in the direction opposite to the compression direction Y, in other words, opposite to the compression force E32, and with an intensity greater than the compression force E32. In practice, during the normal use of the fuel cell 10, for example in a vehicle, the forces to which the movable end plate 16 is subjected essentially come from vehicle vibrations, and their intensity is less than the compression force E32. Therefore, during the normal use of the fuel cell 10, the dimensions of the metal blades 32 are advantageously designed to apply a compression force E32 on the movable end plate 16 sufficient to prevent the movable end plate 16 from displacing in the compression direction Y. For example, under the normal operating conditions of the fuel cell 10, the sum of the compression forces E32 is approximately equal to 1000 N. In other words, any upward vertical displacement of the movable end plate 16 can be avoided as long as the acceleration to which the movable end plate is subjected parallel to the compression direction Y is less than 15g (where "g" represents the standard acceleration due to gravity).

[0082] Furthermore, the fact that the compression direction Y is preferably vertically oriented and the compression force E2 is directed downward along this vertical direction means that the vertical upward displacement of the movable end plate 16 is also limited by the self-weight of the movable end plate and the stack 12, which increases the compression force E32 to limit the vertical upward displacement of the movable end plate.

[0083] Advantageously, the inclined supports 38A, 38B extend parallel to the stack direction X, since the contact between the inclined supports and the guiding members 36A, 36B is thus maintained, independently of the expansion of the stack 12. In practice, the inclined supports 38A and 38B extend over a length L38 that is at least equal to the maximum expansion amplitude of the stack 12.

[0084] In practice, the inclined supports 38A and 38B are inclined at an angle α between 30° and 60° with respect to the compression direction Y. Preferably, the inclined supports 38A and 38B are inclined at 45° with respect to the compression direction Y and thus also at 45° with respect to the centering direction Z. Therefore, for each of the reaction forces F1 and F2, the intensity of the first component is equal to the intensity of the second component. This configuration is advantageous for balancing the forces applied to the movable end plate 16 parallel to the compression direction Y and the forces applied to the movable end plate 16 parallel to the centering direction Z.

[0085] Due to the guiding system 30, the position of the movable end plate 16 is rigidly constrained to be parallel to the compression direction Y and the centering direction Z. Thus, when the fuel cell is operating, the movement of the movable end plate in these directions is virtually eliminated, thereby reducing the mechanical stress on the electrochemical cells of the stack 12 and thus extending their service life. Advantageously, under normal operating conditions of the fuel cell 10, the guiding system 30 prevents displacement of the movable end plate 16 parallel to the compression direction Y and the centering direction Z. In other words, due to the guiding system 30, under normal operating conditions of the fuel cell 10, the movable end plate 16 can move relative to the housing 18 along a sliding connection parallel to the stack direction X.

[0086] One advantage of the guiding system 30 is that, due to the inclined supports 38A, 38B which are inclined with respect to the compression direction Y and the centering direction Z, by applying a compression force to the movable end plate only in the compression direction Y by means of the metal blades 32, it is possible to limit the displacement of the movable end plate 16 parallel to the compression direction Y and parallel to the centering direction Z. Thus, the design of the guiding system 30 is particularly simple, reducing the manufacturing cost of the fuel cell 10.

[0087] Another advantage of the guiding system 30 is that the force is applied only to the movable end plate 16 and the housing 18, and no force is applied to the stack 12. Thus, the stack 12 is suspended between the fixed end plate 14 and the movable end plate 16, and the mechanical force applied to the electrochemical cells is reduced.

[0088] Advantageously, but not mandatorily, the fuel cell 10 is integrated into a vehicle by means of damping means, such as by springs and / or elastic studs, connected to the vehicle chassis, in which case the springs and / or elastic studs are advantageously provided between the housing 18 and the vehicle chassis. In particular, such damping means allows limiting the vibrations to which the fuel cell is subjected. Particularly advantageously, the relative movement of the fuel cell with respect to the vehicle chassis is suppressed to reduce the mechanical constraints which are normally applied to the fuel cell 10 and, in particular, to the electrochemical cells of the stack 12. Since the damping means reduces the mechanical stress applied to the fuel cell and the guiding system allows the mechanical constraints remaining after damping not to cause displacement of the movable end plate 16 relative to the housing 18, which could in turn damage the electrochemical cells of the stack 12, such damping means is also particularly suitable for use in conjunction with the guiding system 30 of the present invention.

[0089] In this example, the two guiding members 36A, 36B are two shoes fixed to the movable end plate 16, and the two inclined supports 38A, 38B are formed by the surfaces of two tracks 40A, 40B fixed to the housing 18 or integral with the housing 18 (more precisely, with one of the side walls 22 of the housing). The shoes 36A, 36B have a profile complementary to the profile of the inclined supports 38A, 38B to allow for optimal contact between the shoes and the inclined supports.

[0090] Advantageously, but not mandatorily, the shoes 36A, 36B can be made of or coated with a material having low friction properties such as polytetrafluoroethylene (also known as "Teflon"), or can be made of a material having surface conditions ensuring a low coefficient of friction.

[0091] Herein, the two tracks 40A and 40B are parallel to each other and extend parallel to the stacking direction X, and exhibit a triangular profile. Thus, the inclined supports 38A, 38B are flat surfaces. In this example, the inclined supports 38A and 38B are formed by the surfaces of the tracks 40A, 40B, and the normal surfaces of the tracks 40A, 40B face the center of the movable end plate 16, as Figure 3 shown.

[0092] In an alternative embodiment (not shown) of the present invention, the inclined supports are formed by the surfaces of the tracks 40A, 40B facing the outside of the movable end plate. Thus, the inclined supports 38A and 38B diverge from the wall 22 of the housing 18 to which the metal blade 32 is connected.

[0093] In an alternative embodiment (not shown) of the present invention, the two inclined supports 38A and 38B are formed on two separate surfaces of the same track.

[0094] In an alternative embodiment (not shown) of the present invention, the tracks 40A, 40B exhibit a profile other than a triangular profile, for example, a trapezoidal profile or a profile of any quadrilateral shape having at least one inclined surface, to form the inclined supports 38A, 38B.

[0095] In an alternative embodiment (not shown) of the present invention, the inclined supports 38A, 38B are not flat, but exhibit another profile, such as an arcuate or elliptical profile, which is perpendicular to the stacking direction X and extends along the stacking direction. In this alternative embodiment, the shape of the guiding members 36A, 36B is adapted to match the profile of the inclined supports 38A, 38B. For example, the guide rails are spherical.

[0096] In an alternative embodiment (not shown) of the present invention, the guiding members 36A, 36B are fixed to the housing 18, and the tracks 40A, 40B forming the inclined supports 38A, 38B are fixed to the movable end plate 16.

[0097] In an alternative of the present invention, on the one hand, the positioning of the compression member 32 is not shown, and on the other hand, the positioning of the guiding members 36A, 36B and the tilting supports 38A, 38B is reversed. In this alternative, the compression direction Y is vertical and points upward.

[0098] In practice, the fuel cell 10 can also be implemented with other orientations of the stacking direction X, the compression direction Y and the centering direction Z. For example, the stacking direction can be vertical, or the centering direction Z can be vertical.

[0099] In an alternative (not shown) of the present invention, the guiding system 30 further includes two lateral compression members arranged parallel to the centering direction Z on one side of the movable end plate 16 to apply a compression force to the movable end plate in parallel with the centering direction. Thus, the first of the two lateral compression members applies a compression force to the movable end plate 16 relative to the housing 18 along the centering direction Z, while the second of the two lateral compression members applies a compression force to the movable end plate relative to the housing in a direction opposite to the centering direction. In this alternative, the centering of the movable end plate relative to the fixed end plate 14 is enhanced.

[0100] As long as technically feasible, any feature described in one of the above embodiments or alternatives can be used in the other above embodiments and alternatives.

Claims

1. A fuel cell (10), which comprises: - a housing (18), - a stack (12) of electrochemical cells, which extends along a stack direction (X), - a fixed end plate (14), which is arranged at a first end (12A) of the stack and is fixed relative to the housing, - a movable end plate (16), which is arranged at a second end (12B) of the stack and is movable relative to the housing parallel to the stack direction, the fixed (14) and movable (16) end plates clamping the stack (12) therebetween, and - a guiding system (30) for the movable end plate, which is configured to allow displacement of the movable end plate parallel to the stack direction (X) and to limit displacement of the movable end plate perpendicular to the stack direction, characterized in that the guiding system (30) for the movable end plate (16) comprises: - at least one compression member (32), which applies a compression force (E32) to the movable end plate (16) relative to the housing (18) along a compression direction (Y) perpendicular to the stack direction (X), - two guiding members (36A, 36B), which are fixed relative to a first element (16, 18) among the housing and the movable end plate, and - two inclined supports (38A, 38B), which are fixed relative to a second element (16, 18) among the housing and the movable end plate different from the first element, extend parallel to the stack direction (X), each inclined support being inclined relative to the compression direction (Y) and being inclined relative to a centering direction (Z) perpendicular to the stack direction and the compression direction, and due to the action of the compression force (E32) applied by the compression member (32), each guiding member (36A, 36B) bears against one of the two inclined supports (38A, 38B), and the two guiding members center the movable end plate (16) relative to the housing (18) parallel to the centering direction (Z).

2. The fuel cell (10) according to claim 1, wherein under the action of the compression force (E32) applied by the compression member (32), the first guiding member (36A) tends to displace the movable end plate (16) along the centering direction (Z), and the second guiding member (36B) tends to displace the end plate in a direction opposite to the centering direction.

3. The fuel cell (10) according to any one of claims 1 and 2, wherein each inclined support (38A, 38B) is formed by a surface of a track (40A, 40B) extending parallel to the stack direction (X).

4. The fuel cell (10) according to any one of claims 1 to 3, wherein each inclined support (38A, 38B) is inclined at an angle (α) between 30° and 60° relative to the compression direction (Y), preferably equal to 45°.

5. The fuel cell (10) according to any one of claims 1 to 4, wherein the guiding members (36A, 36B) are shoes having a profile complementary to the profile of the inclined supports (38A, 38B).

6. The fuel cell (10) according to any one of claims 1 to 5, wherein the compression member (32) is an elastically deformable blade.

7. The fuel cell (10) according to claim 6, wherein the elastically deformable blade (32) has two ends (32A, 32B) and a central portion (32C), wherein the two ends of the elastically deformable blade are connected to the first elements (16, 18), and wherein the central portion of the elastically deformable blade is supported against the second elements (16, 18).

8. The fuel cell (10) according to claim 7, wherein the elastically deformable blade (32) extends in a direction (A32) parallel to the stacking direction (X), wherein the guiding system (30) includes two fixing members (34), and wherein each fixing member connects one end (32A, 32B) of the elastically deformable blade to the first elements (16, 18), allowing displacement of the end parallel to the stacking direction (X) and preventing displacement of the end perpendicular to the stacking direction.

9. The fuel cell (10) according to any one of claims 1 to 8, wherein the support of the first guiding member (36A) generates a first reaction force (F1) on the first inclined support (38A), wherein the support of the second guiding member (36B) generates a second reaction force (F2) on the second inclined support (38B), wherein each of the first reaction force and the second reaction force has a first component oriented parallel to the compression direction (Y) and a second component oriented parallel to the centering direction (Z), wherein the first components of the first reaction force and the second reaction force have equal intensities and orientations and have a direction opposite to the direction of the compression force (E32), and wherein the second components of the first reaction force and the second reaction force have the same intensity and opposite orientations.

10. The fuel cell (10) according to any one of claims 1 to 9, wherein the guiding system (30) further includes two lateral compression members, a first lateral compression member applying a compression force along the centering direction (Z) on the movable end plate (16) relative to the housing (18), and the second lateral compression member applying a compression force along a direction opposite to the centering direction on the movable end plate relative to the housing.

11. The fuel cell (10) according to any one of claims 1 to 9, wherein the fuel cell (11) further includes a clamping system (24), the clamping system applying a clamping force (E24) parallel to the stacking direction (X) on the movable end plate (16) relative to the housing (18), tending to compress the stack (12) of the electrochemical cells.

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