FUEL CELL

Description

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

[0002] In the field of fuel cells, it is common practice to sandwich a stack of electrochemical cells between two end plates, positioned on either side of the stack in the same stacking direction, and to protect this assembly within a casing. The end plates both maintain the compressed stack and accommodate the connectors necessary for the fuel cell's operation, such as the gas inlets.

[0003] During operation, the stack of electrochemical cells tends to expand in the stacking direction due to aging and thermal effects. To allow this expansion to occur without damaging the electrochemical cells, it is known to fix a first end plate to the housing and to make a second end plate movable relative to the housing, parallel to the stacking direction. Thus, the second end plate moves according to the stack's expansion, and the stack's compression is not increased beyond a tolerance threshold by the stack's expansion.

[0004] It is known to use a guidance system to allow the moving end plate to move parallel to the stacking direction and to prevent its movement perpendicular to the stacking direction. However, known guidance systems are generally unsatisfactory.

[0005] For example, US-A-2009 / 0004533 describes a fuel cell in which the moving end plate is guided in its movement parallel to the stacking direction by guide shafts extending through openings in the casing, and in which movement of the moving end plate perpendicular to the stacking direction is prevented by direct contact of the end plate against the casing walls. The guidance by the guide shafts is statically indeterminate, which leads to a risk of the moving end plate jamming and complicates the fuel cell assembly. Furthermore, in such a fuel cell, it is necessary to provide operating clearance, i.e., a gap, between the moving end plate and the casing walls, to allow the moving end plate to move parallel to the stacking direction without risk of jamming or butting against the casing walls.However, the presence of such operating play allows the moving end plate and the electrochemical cells to vibrate perpendicular to the stacking direction. Such vibrations are detrimental to the lifespan of the electrochemical cells.

[0006] Another example of movable end plate guidance is given by CN-A-112,993,368. In a first direction perpendicular to the stacking direction, the movable end plate is guided by pads arranged on either side of the end plate and bearing against the housing walls. Rails are also arranged on four sides of the end plate and cooperate with spring-mounted brackets attached to the housing walls to limit the movement of the movable end plate in the first direction as well as in a second direction perpendicular to both the stacking and first directions. This approach, in addition to being complex to implement and having a significant footprint, allows lateral movement of the movable end plate parallel to the second direction, since the brackets are spring-mounted.Thus, such a fuel cell does not prevent vibrations of the moving terminal plate, and therefore of the electrochemical cells, in the second direction, which is detrimental to the lifespan of the electrochemical cells.

[0007] US-A-2018 / 0241050, EP-A-3 018 748 and US-A-2009 / 280388 describe other examples of a fuel cell moving end plate guidance system.

[0008] It is these drawbacks that the invention intends to remedy in particular, by proposing a fuel cell allowing the movement of the mobile terminal plate parallel to the stacking direction, while controlling the position of the terminal plate perpendicular to the stacking direction.

[0009] To this end, the invention relates to a fuel cell comprising: a casing, a stack of electrochemical cells extending along a stacking direction, a fixed terminal plate, disposed at one end of the stack and fixed relative to the casing, a movable terminal plate, disposed at a second end of the stack and movable relative to the casing parallel to the stacking direction, the fixed and movable terminal plates clamping the stack together, and a movable terminal plate guidance system, configured to permit movement of the movable terminal plate parallel to the stacking direction and to limit movement of the movable terminal plate perpendicular to the stacking direction.

[0010] According to the invention, the movable end plate guidance system comprises: at least one compression member exerting a compressive force on the movable end plate, relative to the housing, along a compression direction perpendicular to the stacking direction, two guide members, fixed relative to a first element among the housing and the movable end plate, and two oblique supports, fixed relative to a second element among the housing and the movable end plate different from the first element, extending parallel to the stacking direction, each oblique support being oblique relative to the compression direction and relative to a centering direction perpendicular to the stacking direction and the compression direction.

[0011] Furthermore, under the effect of the compressive force exerted by the compression member, each guide member is supported against one of the two oblique supports and the two guide members center the movable end plate, parallel to the centering direction, relative to the housing.

[0012] Thanks to the invention, the position of the movable end plate perpendicular to the stacking direction is constrained by the guide elements bearing against the oblique supports by the compression element. The oblique supports, being angled relative to the direction in which the compression forces are exerted, both prevent the movable end plate from moving along the compression direction and center the movable end plate along the centering direction.

[0013] According to advantageous, but not mandatory, aspects of the invention, the fuel cell incorporates one or more of the following features, taken individually or in any technically feasible combinations: Under the compressive force exerted by the compression element, a first guide tends to cause the movable end plate to move along the centering direction, and a second guide tends to cause the end plate to move in the opposite direction to the centering direction. Each angled support is formed by a face of a rail extending parallel to the stacking direction. Each angled support is inclined relative to the compression direction at an angle between 30° and 60°, preferably 45°. The guide elements are pads with profiles complementary to the profiles of the angled supports. The compression element is an elastically deformable blade.The elastically deformable blade has two ends and a central portion. The two ends of the elastically deformable blade are connected to the first element, and the central portion of the elastically deformable blade rests against the second element. The elastically deformable blade extends in a direction parallel to the stacking direction. The guiding system comprises two fastening members, and each fastening member connects one end of the elastically deformable blade to the first element, allowing movement of that end parallel to the stacking direction and preventing movement of that end perpendicular to the stacking direction.The support of a first guiding element on a first oblique support generates a first reaction force, the support of the second guiding element on the second oblique support generates a second reaction force, each of the first and second reaction forces has a first component directed parallel to the direction of compression and a second component directed parallel to the direction of centering, the first components of the first and second reaction forces are of equal magnitude and orientation and opposite orientation to the orientation of the compression force, and the second components of the first and second reaction forces are of equal magnitude and opposite orientation.The guidance system further comprises two lateral compression elements: a first lateral compression element exerting a compressive force on the movable end plate, relative to the housing, along the centering direction, and a second lateral compression element exerting a compressive force on the movable end plate, relative to the housing, opposite to the centering direction. The fuel cell further comprises a clamping system exerting a clamping force on the movable end plate, relative to the housing, parallel to the stacking direction, tending to compress the stack of electrochemical cells.

[0014] The invention will be better understood and other advantages thereof will become more apparent in the light of the following description of an embodiment of a fuel cell, in accordance with its principle, given solely by way of example and with reference to the accompanying drawings in which: [ Fig. 1 ] There figure 1 is a perspective view of a fuel cell according to the invention: [ Fig. 2 ] There figure 2 is a view analogous to the figure 1 , on which a fuel cell casing is not shown; [ Fig. 3 ] There figure 3 is a front view of the fuel cell of the figure 1 ; And [ Fig. 4 ] There figure 4 is a cross-section along plane IV of the fuel cell of the figure 3 .

[0015] A fuel cell 10 is visible on the figures 1 à 4 . The fuel cell 10 is, for example, intended to be integrated into an electric motor vehicle in order to produce electrical energy enabling the operation of the motor, possibly in whole or in part via a battery of electrical accumulators.

[0016] The fuel cell 10 comprises a stack 12 of electrochemical cells, which are not individually represented for the sake of simplicity. Each electrochemical cell generally consists of an anode and a cathode separated by a polymer membrane that allows the passage of protons from the anode to the cathode. The anode is supplied with fuel, for example dihydrogen, and the cathode is supplied with an oxidant, for example oxygen or air.

[0017] The electrochemical cells are stacked along a stacking direction X to form the stack 12. The stacking direction X is that of the length of the stack 12, in other words, the longitudinal direction of this stack. Preferably, when the fuel cell 10 is in operation, for example in a vehicle, the stacking direction X is horizontal.

[0018] In this description, the term "direction" is used to refer to the orientation of a line in a plane. In other words, a direction corresponds to an oriented line, and therefore to a direction of travel along that line.

[0019] The fuel cell 10 includes a fixed terminal plate 14 and a movable terminal plate 16, which are arranged on either side of the stack 12, along the stacking direction X. In the example, the stacking direction X is oriented so as to extend from the fixed terminal plate 14 towards the movable terminal plate 16. In practice, the fixed terminal plate 14 and the movable terminal plate 16 extend perpendicularly to the stacking direction X.

[0020] In practice, the fixed end plate 14 is positioned at a first end 12A of the stack 12, and the movable end plate 16 is positioned at a second end 12B of the stack, which corresponds to a free end of the stack. In other words, the movable end plate 16 forms a free end of the assembly formed by the fixed and movable end plates and the stack 12.

[0021] Preferably, the fixed terminal plate 14 includes connectors, not shown, for connection to fluid circulation lines, thus supplying the stack 12 with fuel and oxidizing gas and optionally with coolant. Other elements may be interposed between each of the terminal plates 14, 16 and the stack, as is known per se. These elements include, but are not limited to, a current collector plate and / or an insulation plate.

[0022] The fuel cell 10 includes a casing 18, which surrounds and protects the stack 12 of electrochemical cells. In practice, the casing 18 comprises a base 20 and side walls 22. Here, the base 20 is perpendicular to the stacking direction X and the side walls 22 extend parallel to the stacking direction X.

[0023] The fixed end plate 14 is, in practice, fixed to the housing 18, more precisely to the bottom 20 of the housing, and the movable end plate 16 is movable within the housing parallel to the stacking direction X, between the side walls 22, as detailed below. The bottom 20 of the housing and the fixed end plate 14 thus form a rigid assembly. In the example, the bottom of the housing and the fixed end plate are two separate parts rigidly joined to each other. In an alternative embodiment of the invention, not shown, the bottom of the housing and the fixed end plate are formed as a single piece, the two then being indistinguishable.

[0024] The fuel cell 10 includes a clamping system 24 that exerts a clamping force E24 on the movable end plate 16, relative to the housing 18. This clamping force E24 is parallel to and oriented in the opposite direction to the stacking direction X, which is a longitudinal direction of the stack. The clamping force E24 is therefore a longitudinal compressive force exerted on the movable end plate 16. The longitudinal direction X is thus a clamping direction of the stack 12. The clamping system 24 tends to bring the movable end plate 16 closer to the fixed end plate 14, thereby compressing the stack 12 between the fixed and movable end plates. In other words, the fixed and movable end plates clamp the stack 12 together under the effect of the clamping force E24.The compression of the stack 12 between the fixed terminal plates 14 and mobile terminal plate 16 ensures optimal operation of the electrochemical cells, and therefore of the fuel cell 10.

[0025] In the example, the clamping system 24 comprises 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 exert the clamping force E24 on the movable end plate 16, relative to the clamping flange 26, thus compressing the stack 12. Here, the clamping flange 26 is fixed relative to the housing 18, for example, by being attached to the side walls 22 using fastening means not shown. For the sake of simplicity, the compression springs 28 are shown only at the figure 4 The clamping force E24 is distributed into several elementary forces, each acting on a compression spring, two of which are shown on the figure 4 .

[0026] Other designs are conceivable for the clamping system 24. According to a first variant (not shown), the clamping flange 26 may not be fixed to the side walls 22 of the housing 18, but connected to the bottom 20 of the housing by means of tie rods, allowing the clamping flange to move perpendicularly to the stacking direction X while preventing it from moving parallel to the stacking direction X. Furthermore, in the event of significant thermal stresses applied to the fuel cell 10, the tie rods may also tend to expand along the stacking direction X, causing the clamping flange 26 to move along the stacking direction X.

[0027] According to another variant not shown, the clamping system 24 includes, instead of the clamping flange and compression springs, tension springs which are fixed on one side to the bottom 20 of the housing 18 and on the other side to the movable end plate 16.

[0028] During the lifetime of the fuel cell 10, the stack 12 of electrochemical cells tends to expand and / or contract, parallel to the stacking direction X. This variation in the length of the stack 12 is caused, for example, by the aging of the electrochemical cells, by the pressure increase of the fluids in the channels of the electrochemical cells in the stack 12, or by thermal effects. In practice, the variation in the dimensions of the stack 12 is small compared to the stack length, denoted L12. The maximum variation in the dimensions of the stack 12 is thus, for example, equal to a percentage within the range of 0.5% to 2% of the stack length L12. For example, for a stack length L12 of the order of 400 mm, measured along the stacking direction X, the maximum variation in the stack's dimensions during its lifetime is on the order of a few millimeters, for example 4 mm.

[0029] Since the terminal plate 14 is fixed relative to the housing 18, the variation in length of the stack 12 causes a displacement of the movable terminal plate 16, parallel to the stacking direction X.

[0030] In practice, the compression springs 28 are, for example, dimensioned to absorb the maximum variation in dimension of the stack 12 while maintaining a clamping force whose variation is sufficiently small to remain within a clamping force tolerance range of the stack, regardless of the expansion or contraction of the stack.

[0031] To allow the movement of the movable end plate 16 parallel to the stacking direction X while limiting a movement of the movable end plate perpendicular to the stacking direction, the fuel cell 10 includes a guidance system 30.

[0032] A transverse direction Y of the fuel cell 10 is defined as a direction perpendicular to the stacking direction X, and a centering direction Z of the fuel cell is defined as a direction perpendicular to both the stacking direction X and the transverse direction Y. Preferably, when the fuel cell 10 is operating, for example in a vehicle, with the stacking direction X horizontal, the transverse direction Y is vertical, and advantageously oriented downwards, and the centering direction Z is horizontal. Here, the centering direction Z is arbitrarily defined as oriented, from the point of view of the figure 3 , from left to right and the X, Y and Z directions are those of the axes of an orthogonal coordinate system.

[0033] The guide system 30 includes at least one compression member 32, which exerts a compressive force E32 on the movable end plate 16, relative to the housing 18, in the transverse direction Y. The transverse direction is therefore a compression direction of the movable end plate 16, perpendicular to the compression direction X of the stack 12. In other words, the compressive force E32 is transverse with respect to the stack 12.

[0034] In the example, the guide system 30 comprises two compression members 32, each exerting a compression force E32 on the movable end plate 16. Alternatively, the guide system 30 comprises a different number of compression members 32, for example a single compression member or three compression members.

[0035] A compression member 32 is, for example, made in the form of an elastically deformable blade, one portion of which, for example, one end, is fixed to one of the housing 18 and the movable end plate 16, and one portion of which rests on the other of the housing and the movable end plate. Here, the compression members 32 are elastically deformable blades. In the 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 along a direction A32 globally parallel to the stacking direction X and has a convex profile along the compression direction Y, that is to say, 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 part 32C is not aligned with the first and second ends 32A, 32B.Direction A32 is only shown at the . figure 2 , for one of the two elastically deformable blades 32.

[0036] In the example, the elastically deformable blades 32 are deformable metal blades. Alternatively, the elastically deformable blades are made of another material, for example, a polymer or composite material.

[0037] In the example, the first and second ends 32A, 32B are connected to the housing 18, in practice to one of the side walls 22 of the housing, and the central part 32C is in contact with the movable end plate 16.

[0038] In practice, the guide system 30 comprises, for each metal blade 32, two fixing members 34. Preferably, each fixing member 34 connects one of the two ends 32A, 32B of a metal blade 32 to the housing 18, so as to allow a movement of this end parallel to the stacking direction X while preventing a movement of this end perpendicular to the stacking direction X.

[0039] Here, each fastening member 34 comprises 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 blades are connected, i.e. it extends parallel to the centering direction Z and the stacking direction X, and is fixed to the side wall of the housing by the two retaining elements 34B, which in the 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 blade 32 is arranged, parallel to the compression direction Y, between a side wall 22 of the housing 18 and the retaining plate 34A of a fastener 34, and, parallel to the centering direction Z, between the two screws 34B of this fastener 34.Thus, the displacement of each end of each metal blade parallel to the compression Y and centering Z directions is prevented.

[0040] In addition, the fastening members 34 allow the metal blades 32 to move parallel to the stacking direction X. In practice, the permissible movement of a metal blade 32 parallel to the stacking direction X is of small amplitude, due to the convex shape of the metal blades because, in the event of excessive movement, the metal blade comes into contact with the retaining plate 34A of one of the fastening members 34, which prevents further movement of the metal blade.

[0041] Alternatively, each fastening member 34 fixes one of the two ends 32A, 32B of a metal blade 32 to the housing 18, preventing any movement of this end along the three directions X, Y and Z.

[0042] When the fuel cell 10 is assembled, each metal blade 32 is constrained between the housing 18 and the movable end plate 16; that is, each metal blade is elastically deformed to fit into place between the housing and the end plate. This constraint of the metal blades 32 is facilitated by the possibility for the ends 32A, 32B of the metal blades to move parallel to the stacking direction X. In practice, the constraint of a metal blade 32 generates a reaction force on the housing 18 and on the movable end plate 16, and thus generates a compressive force E32. The metal blades 32 therefore act as compression springs.

[0043] Preferably, all compression forces E32 exerted by the metal blades 32 are identical, within manufacturing and assembly tolerances.

[0044] The use of metal blades 32 to exert the compressive force E32 on the movable end plate 16 is advantageous because the metal blades are elongated in the direction of movement of the movable end plate, i.e., parallel to the stacking direction X. Thus, the metal blades 32, and more particularly their central part 32C, maintain contact with the movable end plate 16 regardless of the position of the movable end plate along the stacking direction X, within the limit of the expansion amplitude of the stack 12. The compressive force E32 is therefore maintained on the movable end plate 16 throughout the life of the fuel cell 10.

[0045] In a non-represented variant of the invention, the metal blades 32 are reversed, i.e. their ends 32A, 32B are fixed to the movable end plate 16 and their central part 32C is in contact with the housing 18. Preferably, in such a variant, the movable end plate 16 includes a skirt extending parallel to the stacking direction X, allowing the two ends of the metal blades to be connected thereto.

[0046] In a non-shown variant of the invention, other compression elements are used instead of metal blades, such as helical springs or spring washers, known as "Belleville washers". The compression elements may also each be formed by a compression element comprising one or more helical springs and / or one or more spring washers in association with a deformable blade, in particular with a deformable blade as described above, or with an articulated blade, one end of which is fixed to one of the housing 18 and the movable end plate 16, one portion of which bears against the other of the housing and the movable end plate, and another portion of which serves as a support for one or more helical springs and / or one or more spring washers.

[0047] The guidance system 30 further includes two guide members 36A, 36B and two oblique supports 38A, 38B extending parallel to the stacking direction X.

[0048] In the example, the guide elements 36A, 36B are fixed to the movable end plate 16, opposite the metal blades 32, along the compression direction Y. In other words, the metal blades 32 and the guide elements 36A, 36B are located at two opposite edges of the end plate 16. Furthermore, the guide elements 36A and 36B are preferably arranged symmetrically with respect to each other, with respect to the cutting plane IV, which is a median plane of the fuel cell parallel to the X and Y directions.

[0049] The oblique supports 38A and 38B are, in the example, fixed to the casing 18, and more precisely to the side wall 22 of the casing opposite the side wall to which the metal blades 32 are connected. Thus, in the example where the stacking direction is horizontal and the compression direction is vertical and downwards, the oblique supports 38A and 38B are located under the movable end plate 16. In practice, the oblique supports 38A and 38B are oblique with respect to the compression direction Y and with respect to the centering direction Z. In other words, a line normal to the oblique supports 38A and 38B intersects the compression direction Y and the centering direction Z. Furthermore, the oblique support 38A is symmetrical to the oblique support 38B with respect to the compression direction Y, so that a line normal to the oblique support 38A is perpendicular to a line normal to the oblique support 38B.

[0050] When the fuel cell 10 is assembled, under the effect of the compressive forces E32 generated by the metal blades 32, which cause a displacement of the end plate 16 in the compression direction Y, the guide member 36A is brought against the oblique support 38A and the guide member 36B is brought against the oblique support 38B. Thus, the oblique support 38A exerts a reaction force F1 on the guide member 36A, directed perpendicularly to the oblique support 38A, and the oblique support 38B exerts a reaction force F2 on the guide member 36B, directed perpendicularly to the oblique support 38A.

[0051] The reaction forces F1 and F2 are oriented perpendicular to the stacking direction X and obliquely to the compression direction Y and centering direction Z. Furthermore, the reaction force F1 is symmetrical to the reaction force F2, with respect to the compression direction Y. In other words, the reaction forces F1 and F2 each have a first component directed parallel to the compression direction Y and a second component directed parallel to the centering direction Z; the first components of the reaction forces F1 and F2 are of equal magnitude and direction, and the second components of the reaction forces F1 and F2 are of equal magnitude and opposite direction.

[0052] It is then understood that the reaction force F1 tends to cause a displacement of the movable end plate 16 along the centering direction Z, and that the reaction force F2 tends to cause a displacement of the movable end plate 16 in the opposite direction to the centering direction Z. These two opposing forces result in the movable end plate 16 being centered with respect to the oblique supports 38A, 38B, parallel to the centering direction Z. Advantageously, the oblique supports 38A and 38B are themselves centered with respect to the fixed end plate 14. The movable end plate 16, under the effect of the reaction forces F1 and F2, is centered with respect to the fixed end plate 14, parallel to the centering direction Z.

[0053] Furthermore, and particularly advantageously, the oblique supports 38A and 38B converge opposite the wall 22 of the housing 18 to which the metal blades 32 are connected; that is, a normal vector to the oblique support 38A and a normal vector to the oblique support 38B converge towards each other. Thus, the second components of the reaction forces F1 and F2 converge. The centering of the movable end plate 16 is thereby improved.

[0054] In a non-represented variant of the invention, the oblique supports 38A and 38B diverge opposite the wall 22 of the housing 18 to which the metal blades 32 are connected, that is to say that a normal vector to the oblique support 38A and a normal vector to the oblique support 38B diverge from each other, and the second components of the reaction forces F1 and F2 diverge.

[0055] Furthermore, the sum of the compressive forces E32 and the reaction forces F1 and F2 is zero, so that, once the guide members 36A, 36B are pressed onto the two oblique supports 38A, 38B by the compression members, these forces do not cause any displacement of the movable end plate 16, relative to the housing 18, perpendicular to the stacking direction X. In other words, the compressive forces E32 and the reaction forces F1 and F2 constrain the position of the movable end plate 16 relative to the housing 18, perpendicular to the stacking direction X.

[0056] Thus, in a particularly advantageous manner, the compression forces E32 and reaction forces F1, F2 constrain the position of the movable end plate 16 parallel to the compression direction Y, so as to press the guide members 36A, 36B against the oblique supports 38A, 38B, i.e. by displacing the movable end plate 16 to the maximum in the compression direction Y. Similarly, the compression forces E32 and reaction forces F1, F2 constrain the position of the movable end plate 16 parallel to the centering direction Z, by centering the movable end plate with respect to the fixed end plate 14, i.e. with respect to the housing 18.

[0057] This support of the movable end plate 16 in the Y direction and this centering of the movable end plate relative to the housing 18, and therefore relative to the fixed end plate 14, parallel to the centering direction Z, are particularly advantageous for preventing deformation of the stack 12 and for preventing vibrations of the stack 12, which could damage the electrochemical cells. The lifespan of the fuel cell 10 is thus increased.

[0058] In practice, the guide system 30 limits any displacement of the movable end plate 16 in the compression direction Y as well as parallel to the centering direction Z, thanks to the support of the guide members 36A, 36B against the oblique supports 38A, 38B. Furthermore, since the compression forces E32 and reaction forces F1, F2 are perpendicular to the stacking direction X, the guide system 30 does not impede the displacement of the movable side plate parallel to the stacking direction X.

[0059] Furthermore, the guide system 30 limits any movement of the movable end plate 16 in the opposite direction to the compressive forces E32, that is to say, in the opposite direction to the compression direction Y, i.e., upwards in the example of the figure 3 This is due to the compressive forces E32 generated by the metal blades 32. Thus, a displacement of the movable end plate 16 in the opposite direction to the compression direction Y is theoretically possible, but such a displacement must be caused by a force on the movable end plate directed in the opposite direction to the compression direction Y, i.e., opposite to the compressive forces E32, and of a greater magnitude than the compressive forces E32. In practice, during normal use of the fuel cell 10, for example in a vehicle, the forces experienced by the movable end plate 16 come primarily from vehicle vibrations, and their magnitude is less than the compressive forces E32.Thus, in normal use of the fuel cell 10, the metal blades 32 are advantageously dimensioned to exert compressive forces E32 on the movable end plate 16 sufficient to prevent the movable end plate 16 from moving along the compression direction Y. For example, a sum of the compressive forces E32 approximately equal to 1000 N prevents any upward vertical movement of the movable end plate 16 under normal operating conditions of the fuel cell 10, that is, as long as the accelerations experienced by the movable end plate parallel to the compression direction Y are less than 15g, with "g" expressing the standard acceleration due to gravity.

[0060] Furthermore, the fact that the compression direction Y is preferentially oriented vertically and that the compression forces E2 are directed downwards along this vertical direction implies that an upward vertical displacement of the movable end plate 16 is also limited by the self-weight of the movable end plate and the stack 12, which adds to the compression forces E32 to limit the upward vertical displacement of the movable end plate.

[0061] It is advantageous that the oblique supports 38A, 38B extend parallel to the stacking direction X because, in this way, the contact between the oblique supports and the guiding elements 36A, 36B is maintained independently of the expansion of the stack 12. In practice, the oblique supports 38A and 38B extend over a length L38 at least equal to the maximum expansion amplitude of the stack 12.

[0062] In practice, the oblique supports 38A and 38B are inclined with respect to the compression direction Y at an angle α between 30° and 60°. Preferably, the oblique supports 38A and 38B are inclined at 45° with respect to the compression direction Y, and therefore also inclined at 45° with respect to the centering direction Z. Thus, for each of the reaction forces F1 and F2, the first component is equal in magnitude to the second component. This configuration is advantageous for balancing the forces acting on the movable end plate 16 parallel to the compression direction Y with the forces acting on the movable end plate 16 parallel to the centering direction Z.

[0063] Thanks to the guide system 30, the position of the movable end plate 16 is rigidly constrained parallel to the compression Y and centering Z directions. Movement of the movable end plate along these directions is thus practically eliminated when the fuel cell is operating, thereby reducing the mechanical stresses exerted on the electrochemical cells of the stack 12 and thus increasing their lifespan. Advantageously, under normal operating conditions of the fuel cell 10, the guide system 30 prevents the movable end plate 16 from moving parallel to the compression Y and centering Z directions. In other words, thanks to the guide system 30, the movable end plate 16 moves parallel to the stacking direction X relative to the housing 18 via a sliding joint, under normal operating conditions of the fuel cell 10.

[0064] An advantage of the guide system 30 is that, thanks to the oblique supports 38A, 38B which are oblique with respect to the compression direction Y and centering direction Z, it is possible to constrain the movement of the movable end plate 16 both parallel to the compression direction Y and parallel to the guidance direction Z, by exerting compressive forces on the movable end plate only in the compression direction Y, using the metal blades 32. The design of the guide system 30 is thus particularly simple, reducing the manufacturing cost of the fuel cell 10.

[0065] Another advantage of the guidance system 30 is that it only exerts forces on the movable end plate 16 and on the housing 18, and does not exert any forces on the stack 12. The stack 12 is thus suspended between the fixed end plates 14 and movable end plates 16 and the mechanical forces exerted on the electrochemical cells are reduced.

[0066] Advantageously, but not necessarily, the fuel cell 10 is integrated into a vehicle by being connected to the vehicle's chassis via a damping device, such as springs and / or elastomer pads, which are advantageously located between the casing 18 and the vehicle chassis. Such a damping device helps to limit the vibrations experienced by the fuel cell. Damping the relative movements of the fuel cell with respect to the vehicle chassis is particularly advantageous in order to reduce the mechanical stresses exerted on the fuel cell 10 in general, and on the electrochemical cells of the stack 12 in particular.Such a damping device is also particularly suitable for use with the guidance system 30 of the invention, since the damping device reduces the mechanical stresses exerted on the fuel cell and the guidance system ensures that the mechanical stresses remaining after damping do not cause displacement of the movable terminal plate 16, relative to the housing 18, which could degrade the electrochemical cells of the stack 12.

[0067] In this example, the two guide elements 36A, 36B are two pads, which are fixed to the movable end plate 16, and the two angled supports 38A, 38B are formed by the faces of two rails 40A, 40B fixed to, or integral with, the housing 18, and more specifically with one of the side walls 22 of the housing. The pads 36A, 36B have profiles that complement the profiles of the angled supports 38A, 38B in order to allow optimal contact between the pads and the angled supports.

[0068] Advantageously but not mandatorily, the 36A, 36B pads may be made or coated with a material with low coefficient of friction properties, such as polytetrafluoroethylene, also known by the trade name "Teflon", or may be made of materials with surface conditions ensuring a low coefficient of friction.

[0069] Here, the two rails 40A, 40B extend parallel to each other and parallel to the stacking direction X, and have a triangular profile. The oblique supports 38A, 38B are therefore flat surfaces. In the example, the oblique supports 38A and 38B are formed by faces of the rails 40A, 40B whose normal to the surface is oriented towards the center of the movable end plate 16, as can be seen in the figure 3 .

[0070] In a non-shown variant of the invention, the oblique supports are formed by faces of the rails 40A, 40B oriented outwards from the movable end plate. Thus, the oblique supports 38A and 38B diverge opposite the wall 22 of the housing 18 to which the metal blades 32 are connected.

[0071] In a non-represented variant of the invention, the two oblique supports 38A, 38B are formed on two distinct faces of the same rail.

[0072] In a non-represented variant of the invention, the rails 40A, 40B have a profile other than a triangular profile, such as for example a trapezoidal profile or in the shape of any quadrilateral having at least one oblique face so as to form an oblique support 38A, 38B.

[0073] In a non-shown variant of the invention, the inclined supports 38A, 38B are not flat, but have a different profile, for example, an arc-shaped or elliptical profile, this profile being viewed perpendicular to the stacking direction X and extending along the stacking direction. In such a variant, the shape of the guide members 36A, 36B is adapted to match the profile of the inclined supports 38A, 38B. For example, the guide members are ball-shaped.

[0074] In a non-represented variant of the invention, the guide members 36A, 36B are fixed on the housing 18 and the rails 40A, 40B forming the oblique supports 38A, 38B are fixed on the movable end plate 16.

[0075] In a non-shown variant of the invention, the positioning of the compression members 32, on the one hand, and of the guide members 36A, 36B and the oblique supports 38A, 38B, on the other hand, are reversed. In such a variant, the compression direction Y is vertical and directed upwards.

[0076] In practice, the fuel cell 10 can also be implemented with other orientations for the stacking direction X, compression direction Y and centering direction Z. For example, the stacking direction can be vertical, or the centering direction Z can be vertical.

[0077] In a non-shown variant of the invention, the guiding system 30 also includes two lateral compression members, arranged on either side of the movable end plate 16, parallel to the centering direction Z, which exert compressive forces on the movable end plate parallel to the centering direction. Thus, one of the two lateral compression members exerts a compressive force on the movable end plate 16, relative to the housing 18, along the centering direction Z, and the second of the two lateral compression members exerts a compressive force on the movable end plate, relative to the housing, opposite to the centering direction. In such a variant, the centering of the movable end plate relative to the fixed end plate 14 is reinforced.

[0078] Any feature described for an embodiment or variant in the foregoing may be implemented for the other embodiments and variants described above, provided that it is technically feasible.

Claims

1. A fuel cell (10) comprising: - a housing (18), - a stack (12) of electrochemical cells extending according to a stacking direction (X), - a fixed end plate (14), arranged at a first end (12A) of the stack and fixed relative to the housing, - a movable end plate (16), arranged at a second end (12B) of the stack and movable relative to the housing, parallel to the stacking direction, the fixed (14) and movable (16) end plates clamping the stack (12) between them, and - a guidance system (30) for the movable end plate, configured to allow the displacement of the movable end plate parallel to the stacking direction (X) and to limit the displacement of the movable end plate perpendicular to the stacking direction, characterized in that the guidance system (30) for the movable end plate (16) comprises: - at least one compression member (32) exerting a compression force (E32) on the movable end plate (16), relative to the housing (18), according to a compression direction (Y) perpendicular to the stacking direction (X), - two guide members (36A, 36B), fixed relative to a first element (16, 18) from among the housing and the movable end plate, and - two oblique abutments (38A, 38B), fixed relative to a second element (16, 18) from among the housing and the movable end plate different from the first element, extending parallel to the stacking direction (X), each oblique abutment being oblique relative to the compression direction (Y) and relative to a centering direction (Z) perpendicular to the stacking direction and to the compression direction, and in that, under the effect of the compression force (E32) exerted by the compression member (32), each guide member (36A, 36B) is bearing against one of the two oblique abutments (38A, 38B) and the two guide members center the movable end plate (16), parallel to the centering direction (Z), relative to the housing (18).

2. The fuel cell (10) according to claim 1, wherein, under the effect of the compression force (E32) exerted by the compression member (32), a first guide member (36A) tends to cause a displacement of the movable end plate (16) according to the centering direction (Z), and the second guide member (36B) tends to cause a displacement of the end plate opposite to the centering direction.

3. The fuel cell (10) according to any one of claims 1 and 2, wherein each oblique abutment (38A, 38B) is formed by a face of a rail (40A, 40B) extending parallel to the stacking direction (X).

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

5. The fuel cell (10) according to any one of claims 1 to 4, wherein the guide members (36A, 36B) are shoes presenting profiles complementary to the profiles of the oblique abutments (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) presents two ends (32A, 32B) and a central part (32C), wherein the two ends of the elastically deformable blade are connected to the first element (16, 18), and wherein the central part of the elastically deformable blade is bearing against the second element (16, 18).

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

9. The fuel cell (10) according to any one of claims 1 to 8, wherein the abutment of a first guide member (36A) on a first oblique abutment (38A) generates a first reaction force (F1), wherein the abutment of the second guide member (36B) on the second oblique abutment (38B) generates a second reaction force (F2), wherein each of the first and second reaction forces has a first component directed parallel to the compression direction (Y) and a second component directed parallel to the centering direction (Z), wherein the first components of the first and second reaction forces are of equal intensity and orientation and of opposite orientation to the orientation of the compression force (E32), and wherein the second components of the first and second reaction forces are of equal intensity and opposite orientation.

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

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