Fuel cell

Abstract

This fuel cell (10) includes a housing, a stack of electrochemical cells, a fixed end plate and a movable end plate (16) that clamp the stack therebetween, and a guide system (30) for the movable end plate that restricts displacement of the movable end plate perpendicular to the stacking direction (X). To control the position of the movable end plate, the guide system includes at least one compression member (32) that exerts a compressive force (E32) on the movable end plate in accordance with the compression direction (Y), two guide members (36A, 36B) fixed to the movable end plate, and two inclined abutting portions (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 influence of the compressive force, the guide members press against the inclined abutting portions and center the movable end plate parallel to the centering direction with respect to the housing.

Description

Technical Field

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

Background Art

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

[0003] During operation, the stack of electrochemical cells has a tendency to expand in the stacking direction due to aging and thermal effects. To enable this expansion to occur without damaging the electrochemical cells, it is known to fix the first end plate 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 is movable as a function of the expansion of the stack, and the compression of the stack is not increased beyond an acceptable threshold by the expansion of the stack.

[0004] It is known to use a guiding system to enable displacement of the movable end plate parallel to the stacking direction and to prevent its displacement perpendicular to the stacking direction. However, known guiding systems are usually insufficient.

[0005] For example, in US Patent Application Publication No. 2009 / 0004533, a fuel cell is described in which a movable end plate is guided in its movement parallel to the stacking direction by a guide shaft extending through an opening in the housing, and 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 guidance by the guide shaft is excessive, leading to the risk of immobilizing the movable end plate and making the fuel cell assembly more complex. Furthermore, in such a fuel cell, in order to enable the movable end plate to be displaced parallel to the stacking direction without the risk of immobilization or bending with respect to the housing wall, an operating clearance, i.e., an empty space, needs to be provided between the movable end plate and the housing wall. However, the presence of such an operating clearance leaves the possibility of free vibration of the movable end plate and the electrochemical cells perpendicular to the stacking direction. Such vibrations are disadvantageous for the service life of the electrochemical cells.

[0006] Another example of guiding a movable end plate is given by CN-A-112993368. In a first direction, perpendicular to the stacking direction, the movable end plate is guided by runners disposed on either side of the movable end plate and pressing against the housing wall. In addition to displacement of the movable end plate in the first direction, in order to limit displacement of the movable end plate in the stacking direction and in a second direction perpendicular to the first direction, rails are disposed on four sides of the end plate and cooperate with spring-mounted jumpers connected to the housing wall. This approach is complex to implement and presents a considerable volume. In addition, since the jumpers are spring-mounted, lateral displacement of the movable end plate parallel to the second direction is allowed. Therefore, such a fuel cell does not prevent vibration of the movable end plate in the second direction and, consequently, of the electrochemical cells, which is disadvantageous for the life of the electrochemical cells.

[0007] US Patent Application Publication No. 2018 / 0241050, EP-A-3018748, and US Patent Application Publication No. 2009 / 280388 describe further examples of a guiding system for a movable end plate of a fuel cell.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] In view of these drawbacks, the present invention is more particularly intended to improve by proposing a fuel cell that allows displacement of a movable end plate parallel to the stacking direction while controlling the position of the end plate perpendicular to the stacking direction.

Means for Solving the Problems

[0010] For this purpose, the present invention provides - a housing, - a stack of electrochemical cells extending along the stacking direction, - a fixed end plate disposed at a first end of the stack and fixed to the housing, - a movable end plate disposed at a second end of the stack and movable parallel to the stacking direction with respect to the housing, the fixed and movable end plates clamping the stack therebetween, - A guiding system for a movable end plate configured to enable 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, and A fuel cell comprising the same. According to the present invention, the guiding system for the movable end plate is - At least one compression member that applies a compressive force to the movable end plate with respect to the housing along a compression direction perpendicular to the stacking direction, and - Two guide members fixed to a first element from among the housing and the movable end plate, and - Two inclined abutting portions fixed to a second element different from the first element from among the housing and the movable end plate and extending parallel to the stacking direction, each inclined with respect to the compression direction and with respect to an aligning direction perpendicular to the stacking direction and the compression direction. Comprising.

[0011] In addition, under the influence of the compressive force exerted by the compression member, each guide member presses against one of the two inclined abutting portions, and the two guide members align the movable end plate parallel to the aligning direction with respect to the housing.

[0012] According to the present invention, the position of the movable end plate perpendicular to the stacking direction is restricted by the guide member that abuts against the inclined abutting portion by the compression member. The inclined abutting portion is inclined with respect to the direction in which the compressive force is exerted, enabling the inclined abutting portion to prevent displacement of the movable end plate along the compression direction and to align the movable end plate along the aligning direction.

[0013] According to an advantageous but non-obligatory aspect of the present invention, the fuel cell incorporates one or more of the following features, either alone or in any technically acceptable combination. - Under the influence of the compressive force exerted by the compression member, the first guide member tends to cause displacement of the movable end plate in the centering direction, and the second guide member tends to cause displacement of the end plate in the direction opposite to the centering direction. - Each inclined abutting portion is formed by a surface of a rail extending parallel to the stacking direction. - Each inclined abutting portion is inclined at an angle between 30° and 60°, preferably equal to 45°, with respect to the compression direction. - The guide member is a runner presenting a profile complementary to the profile of the inclined abutting portion. - The compression member is an elastically deformable blade. - The elastically deformable blade presents two ends and a central portion. The two ends of the elastically deformable blade are connected to a first element, and the central portion of the elastically deformable blade presses against a second element. - The elastically deformable blade extends along a direction parallel to the stacking direction. The guiding system comprises two fixed members. Each fixed member connects one end of the elastically deformable blade to the first element, enabling displacement of this end parallel to the stacking direction and preventing displacement of this end perpendicular to the stacking direction. - The contact of the first guide member with the first inclined abutting portion generates a first reaction force, and the pressing of the second guide member against the second inclined abutting portion generates a second reaction force. Each of the first and second reaction forces has a first component directed parallel to the compression direction and a second component directed parallel to the centering direction. The first components of the first and second reaction forces are equal in magnitude and direction and are opposite in direction to the compressive force. The second components of the first and second reaction forces are equal in magnitude and opposite in direction. - The guiding system further comprises two lateral compression members. The first lateral compression member exerts a compressive force on the movable end plate with respect to the housing in the centering direction, and the second lateral compression member exerts a compressive force on the movable end plate with respect to the housing in the direction opposite to the centering direction. - The fuel cell further comprises a clamping system that tends to exert a clamping force on the movable end plate parallel to the stacking direction with respect to the housing, compressing the stack of electrochemical cells.

[0014] The following description, given merely by way of example and with reference to the accompanying drawings, will, in light of the principles of one embodiment of a fuel cell, better enable an understanding of the present invention and will more clearly reveal other advantages of the present invention.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] The fuel cell 10 can be seen in FIGS. 1 to 4. The fuel cell 10 is intended to be incorporated, for example, if possible, in whole or in part using a storage battery, into a vehicle with an electric motor in order to generate electrical energy enabling the operation of the motor.

[0017] The fuel cell 10 comprises a stack 12 of electrochemical cells, which are not shown individually for the sake of simplicity. Each electrochemical cell generally consists of an anode and a cathode separated by a polymer membrane that allows protons to move from the anode to the cathode. Fuel, such as dihydrogen, is supplied to the anode and an oxidant, such as oxygen or air, is supplied to the cathode.

[0018] The electrochemical cells are stacked in the 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 operating, for example, in a vehicle, the stacking direction X is horizontal.

[0019] In this description, the term direction is used as the direction of the orientation of a straight line in a plane. In other words, the direction corresponds to an oriented straight line and thus to the direction of progression along this line.

[0020] The fuel cell 10 comprises a fixed end plate 14 and a movable end 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 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 stacking direction X.

[0021] 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 and movable end plates and the stack 12.

[0022] Preferably, the fixed end plate 14 includes connectors, not shown, which are provided to be connected to the fluid circulation ducts, thus enabling the supply of fuel and oxidant gas, and if possible a cooling fluid, to the stack 12. Other elements can be interposed between each of the end plates 14, 16 and the stack in a manner known per se. Non-limitingly, these can include, for example, current collector plates and / or insulating plates.

[0023] The fuel cell 10 comprises a housing 18, which surrounds and protects the electrochemical cell stack 12. In practice, the housing 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.

[0024] The fixed end plate 14 is actually fixed to the housing 18, more precisely to the base 20 of the housing. The movable end plate 16 is movable in the housing, between the side walls 22, parallel to the stacking direction X, as will be described in detail below. The base 20 of the housing and the fixed end plate 14 thus form a rigid assembly. In the example, the base of the housing and the fixed end plate are two separate parts that are rigidly connected to each other. In one alternative, not shown, of the present invention, the base of the housing and the fixed end plate are formed in a single piece, in which case the two are joined.

[0025] The fuel cell 10 comprises a clamping system 24 that exerts a clamping force E24 on the movable end plate 16 with respect to the housing 18. This clamping force E24 is parallel to the stacking direction X, which is the longitudinal direction of the stack, and in the opposite direction. The clamping force E24 is thus a longitudinal compressive force exerted on the movable end plate 16. The longitudinal direction X is thus the 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, and thus compresses the stack 12 between the fixed and movable end plates. In other words, the fixed and movable end plates clamp the stack 12 between them under the influence of the clamping force E24. Compression of the stack 12 between the fixed 14 and movable 16 end plates ensures optimal operation of the electrochemical cells and thus of the fuel cell 10.

[0026] In the example, the clamping system 24 comprises a clamping flange 26 and compression springs 28, for example four or nine compression springs, arranged between the clamping flange 26 and the movable end plate 16. The compression springs 28 are compressed with respect to the clamping flange 26 to exert a clamping force E24 on the movable end plate 16, and thus compress the stack 12. Here, the clamping flange 26 is fixed to the housing 18, for example, by being fixed to the side walls 22 using fixing means, not shown. For the sake of brevity, the compression springs 28 are shown only in FIG. 4. The clamping force E24 is divided into several basic forces, each of which is exerted by a compression spring, two of which are shown in FIG. 4.

[0027] Other designs for the clamping system 24 are also possible. According to a first alternative, although not shown, the clamping flange 26 may be connected to the base 20 of the housing using tie rods instead of being fixed to the side wall 22 of the housing 18, 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. Further, when high thermal stress is applied to the fuel cell 10, the tie rods may also tend to expand along the stacking direction X, causing displacement of the clamping flange 26 along the stacking direction X.

[0028] According to another alternative, although not shown, the clamping system 24 includes a tension spring instead of a clamping flange and a compression spring, and is fixed to the base 20 of the housing 18 on one hand and to the movable end plate 16 on the other hand.

[0029] Over the life of the fuel cell 10, the stack 12 of electrochemical cells tends to expand and / or contract parallel to the stacking direction X. This change in the length of the stack 12 is caused, for example, by the aging of the electrochemical cells, by the accumulation of fluid pressure in the flow channels of the electrochemical cells of the stack 12, or by thermal effects. In practice, the dimensional change of the stack 12 is small relative to the length of the stack, denoted as L12. The maximum dimensional change of the stack 12 is thus, for example, equal to a percentage in the range from 0.5% to 2% of the stack length L12. For example, for a stack 12 with a length L12 of about 400 mm measured in the stacking direction X, the maximum dimensional change of the stack over its lifetime is on the order of a few millimeters, for example 4 mm.

[0030] Since the end plate 14 is fixed to the housing 18, any change in the length of the stack 12 results in displacement of the movable end plate 16 parallel to the stacking direction X.

[0031] In practice, for example, the compression spring 28 is dimensioned to absorb the maximum dimensional changes of the stack 12 while maintaining a clamping force small enough such that, regardless of whether the stack expands or contracts, the change remains within the stack clamping force tolerance range.

[0032] To enable displacement of the movable end plate 16 parallel to the stacking direction X while restricting displacement of the movable end plate perpendicular to the stacking direction, the fuel cell 10 comprises a guiding system 30.

[0033] The transverse direction Y of the fuel cell 10 is defined as the direction perpendicular to the stacking direction X, and the centering direction Z of the fuel cell is defined as the direction perpendicular to the stacking direction X and the transverse direction Y. Preferably, when the fuel cell 10 is operating with the stacking direction X horizontal, for example in a vehicle, the transverse direction Y is vertical, advantageously directed downwards, and the centering direction Z is horizontal. Here, the centering direction Z is arbitrarily defined as being from left to right from the perspective of FIG. 3, and the directions X, Y, and Z are those of the axes of a rectangular reference system.

[0034] The guiding system 30 comprises at least one compression member 32 that exerts a compression force E32 on the movable end plate 16 in the transverse direction Y with respect to the housing 18. The transverse direction is thus 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.

[0035] In the example, the guiding system 30 comprises two compression members 32, each exerting a compression force E32 on the movable end plate 16. Alternatively, the guiding system 30 comprises a different number of compression members 32, for example a single compression member or three compression members.

[0036] The compression member 32 is, for example, in the form of an elastically deformable blade, with a part of it, for example one end, fixed to one of the housing 18 and the movable end plate 16, and a part of it pressing against the other of the housing and the movable end plate. Here, the compression member 32 is an elastically deformable blade. In the example, each elastically deformable blade 32 presents a first end 32A, a second end 32B and a central part 32C. Each elastically deformable blade 32 extends along a direction A32 substantially parallel to the lamination direction X and presents a dome 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, while the central part 32C is not aligned with the first and second ends 32A, 32B. The direction A32 is shown only in FIG. 2 for one of the two elastically deformable blades 32.

[0037] In the example, the elastically deformable blade 32 is a deformable metal blade. Alternatively, the elastically deformable blade can be made of another material, such as a polymer or a composite.

[0038] In the example, the first and second ends 32A, 32B are connected to the housing 18, actually to one of the side walls 22 of the housing, and the central part 32C presses against the movable end plate 16.

[0039] Actually, the guiding system 30 comprises 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 and enables displacement of this end parallel to the lamination direction X while preventing displacement of this end perpendicular to the lamination direction X.

[0040] Here, each fixing member 34 includes a holding plate 34A and two holding elements 34B. The holding plate 34A extends parallel to the side wall 22 of the housing 18 to which the ends of the metal blades 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 holding elements 34B, which are screws in this example. The two screws 34B are aligned along the stacking direction X and are spaced apart 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 disposed between the side wall 22 of the housing 18 and the holding plate 34A of the fixing member 34, parallel to the compression direction Y and parallel to the centering direction Z, between the two screws 34B of this fixing member 34. Therefore, the displacement of each end of each metal blade parallel to the compression direction Y and the centering direction Z is prevented.

[0041] In addition, the fixing member 34 allows displacement of the metal blade 32 parallel to the stacking direction X. In practice, due to the dome shape of the metal blade, in the case of excessive displacement, the metal blade contacts one holding plate 34A of the fixing member 34, thus preventing further displacement of the metal blade. Therefore, the permitted displacement of the metal blade 32 parallel to the stacking direction X is small.

[0042] Alternatively, each fixing member 34 fixes one of the two ends 32A, 32B of the metal blade 32 to the housing 18 and prevents any displacement of this end in the three directions X, Y, and Z.

[0043] When the fuel cell 10 is assembled, each metal blade 32 is restricted between the housing 18 and the movable end plate 16. In other words, each metal blade is elastically deformed and positioned between the housing and the end plate. This restriction of the metal blade 32 is facilitated by the ability of the ends 32A and 32B of the metal blade to displace parallel to the stacking direction X. In practice, the restriction of the metal blade 32 generates reaction forces in the housing 18 and on the movable end plate 16, thus generating a compression force E32. The metal blade 32 thus acts as a compression spring.

[0044] Preferably, all the compressive forces E32 exerted by the metal blades 32 are identical within the manufacturing and assembly tolerances.

[0045] Since the metal blades extend in the direction of movement of the movable end plate, in other words, parallel to the stacking direction X, the use of the metal blades 32 for exerting a compressive force E32 on the movable end plate 16 is advantageous. For this reason, the metal blades 32, and more particularly their central portions 32C, maintain contact with the movable end plate 16 independently of the position of the movable end plate along the stacking direction X within the expansion amplitude limits of the stack 12. The compressive force E32 is thus maintained on the movable end plate 16 throughout the life of the fuel cell 10.

[0046] In one non-represented alternative of the 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 press against the housing 18. Preferably, in such an alternative, the movable end plate 16 comprises a skirt extending parallel to the stacking direction X and enabling the two ends of the metal blade to be connected thereto.

[0047] In one non-represented alternative of the invention, instead of the metal blades, other compression members are used, such as coil springs or spring washers known as "Belleville washers". The compression members can each be formed by a deformable blade in combination with one or more coil springs and / or one or more spring washers, particularly a deformable blade as described above or a joint blade, with one end of the blade fixed to one of the housing 18 and the movable end plate 16, a portion thereof pressing against the other of the housing and the movable end plate, and another portion thereof serving as an abutment for one or more coil springs and / or one or more spring washers.

[0048] The guiding system 30 further includes two guiding members 36A, 36B and two inclined abutting portions 38A, 38B extending parallel to the stacking direction X.

[0049] The guiding members 36A, 36B are fixed to the movable end plate 16, in the example, opposite to the metal blade 32, along the compression direction Y. In other words, the metal blade 32 and the guiding members 36A, 36B are located at two opposite edges of the end plate 16. Additionally, the guiding members 36A and 36B are preferably arranged symmetrically with respect to each other with respect to the transverse plane IV, which is the mid-plane of the fuel cell parallel to the directions X and Y.

[0050] The inclined abutting portions 38A and 38B are fixed, in the example, to the housing 18, more precisely to the side wall 22 of the housing opposite to the side wall to which the metal blade 32 is connected. Therefore, in the example where the stacking direction is horizontal and the compression direction is vertical and directed downward, the inclined abutting portions 38A and 38B are located below the movable end plate 16. In fact, the inclined abutting portions 38A and 38B are inclined with respect to the compression direction Y and with respect to the centering direction Z. In other words, a straight line perpendicular to the inclined abutting portions 38A and 38B intersects the directions of compression Y and centering Z. Furthermore, the inclined abutting portion 38A is symmetric with respect to the compression direction Y with respect to the inclined abutting portion 38B, and as a result, a line perpendicular to the inclined abutting portion 38A is perpendicular to a line perpendicular to the inclined abutting portion 38B.

[0051] When the fuel cell 10 is assembled, under the influence of the compression force E32 generated by the metal blade 32, which causes displacement of the end plate 16 in the compression direction Y, the guiding member 36A is pressed against the inclined abutting portion 38A, and the guiding member 36B is pressed against the inclined abutting portion 38B. Therefore, the inclined abutting portion 38A exerts a reaction force F1 on the guiding member 36A perpendicularly to the inclined abutting portion 38A, and the inclined abutting portion 38B exerts a reaction force F2 on the guiding member 36B perpendicularly to the inclined abutting portion 38B.

[0052] The reaction forces F1 and F2 are directed obliquely to the compression direction Y and the centering direction Z, perpendicular to the lamination direction X. Further, the reaction force F1 is symmetric with respect to the compression direction Y, relative to the reaction force F2. 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, and the first components of the reaction forces F1 and F2 are of equal strength and direction, and the second components of the reaction forces F1 and F2 are of equal strength and opposite directions.

[0053] Therefore, it is understood that the reaction force F1 tends to cause displacement of the movable end plate 16 along the centering direction Z, and the reaction force F2 tends to cause displacement of the movable end plate 16 in the direction opposite to the centering direction Z. These two counter forces cause the movable end plate 16 to be centered parallel to the centering direction Z with respect to the inclined contact portions 38A, 38B. Advantageously, the inclined contact portions 38A and 38B are themselves centered with respect to the fixed end plate 14. Under the influence of the reaction forces F1 and F2, the movable end plate 16 is centered parallel to the centering direction Z with respect to the fixed end plate 14.

[0054] In addition, in a particularly advantageous manner, the inclined contact portions 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 to the inclined contact portion 38A and the inclined contact portion 38B converge towards each other. Therefore, the second components of the reaction forces F1 and F2 converge. The centering of the movable end plate 16 is thus improved.

[0055] In one alternative, not shown, of the present invention, the inclined contact portions 38A and 38B diverge away from the wall 22 of the housing 18 to which the metal blade 32 is connected, in other words, the normal vectors to the inclined contact portion 38A and the inclined contact portion 38B diverge from each other, and the second components of the reaction forces F1 and F2 diverge.

[0056] Furthermore, the sum of the compression force E32 and the reaction forces F1 and F2 is zero. As a result, once the guide members 36A, 36B are pressed against the two inclined contact portions 38A, 38B by the compression member, these forces do not cause any displacement of the movable end plate 16 perpendicular to the stacking direction X with respect to the housing 18. In other words, the compression force E32 and the reaction forces F1 and F2 restrict the position of the movable end plate 16 with respect to the housing 18 perpendicular to the stacking direction X.

[0057] Therefore, in a particularly advantageous manner, the compression force E32 and the reaction forces F1, F2 press the guide members 36A, 36B against the inclined contact portions 38A, 38B. In other words, by displacing the movable end plate 16 as far as possible in the compression direction Y, the position of the movable end plate 16 parallel to the compression direction Y is restricted. Similarly, the compression force E32 and the reaction forces F1, F2 restrict the position of the movable end plate 16 parallel to the centering direction Z and center the movable end plate with respect to the fixed end plate 14, in other words, with respect to the housing 18.

[0058] This contact of the movable end plate 16 in the direction Y and the centering of the movable end plate parallel to the centering direction Z with respect to this housing 18 and thus with respect to the fixed end plate 14 are particularly advantageous for avoiding deformation of the stack 12 and for avoiding vibrations of the stack 12 that could damage the electrochemical cell. This increases the service life of the fuel cell 10.

[0059] In fact, the guiding system 30 restricts any displacement of the movable end plate 16 parallel to the centering direction Z in addition to the compression direction Y by the contact of the guide members 36A, 36B against the inclined contact portions 38A, 38B. 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 interfere with the displacement of the movable side plate parallel to the stacking direction X.

[0060] In addition, the guiding system 30 restricts any displacement of the movable end plate 16 in the direction opposite to the compression force E32 generated by the metal blade 32, that is to say, in the direction opposite to the compression direction Y, that is to say, in the example of FIG. 3, upward. Therefore, although displacement of the movable end plate 16 in the direction opposite to the compression direction Y is theoretically possible, such displacement must be caused by a force on the movable end plate directed opposite to the compression direction Y, that is to say, opposite to the compression force E32, and of greater strength than the compression force 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 essentially come from vehicle vibrations and their strength is less than the compression force E32. Therefore, during normal use of the fuel cell 10, the metal blade 32 is advantageously dimensioned such that it exerts on the movable end plate 16 a compression force E32 sufficient to prevent displacement of the movable end plate 16 following the compression direction Y. As an example, the total compression force E32, approximately equal to 1000 N, enables any upward vertical displacement of the movable end plate 16 to be avoided under normal operating conditions of the fuel cell 10, that is to say, as long as the acceleration received by the movable end plate parallel to the compression direction Y is less than 15g, where "g" represents the standard acceleration of gravity.

[0061] In addition, the fact that the compression direction Y is preferentially oriented vertically and that the compression force E32 is directed downward following this vertical direction means that the upward vertical displacement of the movable end plate 16 is also limited by the self-weight of the movable end plate and of the stack 12, which is added to the compression force E32 that limits the upward vertical displacement of the movable end plate.

[0062] Since the contact between the inclined abutment and the guide members 36A, 36B is maintained independently of the expansion of the stack 12, it is advantageous for the inclined abutments 38A, 38B to extend parallel to the stacking direction X. In practice, the inclined abutments 38A and 38B extend over a length L38 at least equal to the maximum amplitude of the expansion of the stack 12.

[0063] In practice, the inclined contact portions 38A and 38B are inclined with respect to the compression direction Y by an angle α between 30° and 60°. Preferably, the inclined contact portions 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 first component has the same strength as the second component. This configuration is advantageous for balancing the force exerted on the movable end plate 16 parallel to the compression direction Y with the force exerted on the movable end plate 16 parallel to the centering direction Z.

[0064] By means of the guiding system 30, the position of the movable end plate 16 is firmly constrained parallel to the compression direction Y and the centering direction Z. The movement of the movable end plate following these directions is thus virtually eliminated when the fuel cell is in operation, reducing the mechanical stress on the electrochemical cells of the stack 12 and thus increasing their service life. Advantageously, under normal operating conditions of the fuel cell 10, the guiding system 30 prevents the displacement of the movable end plate 16 parallel to the compression direction Y and the centering direction Z. In other words, by means of the guiding system 30, the movable end plate 16 is movable parallel to the stacking direction X with respect to the housing 18 following a sliding connection under normal operating conditions of the fuel cell 10.

[0065] One advantage of the guiding system 30 is that the inclined contact portions 38A, 38B, which are inclined with respect to the compression direction Y and the centering direction Z, with the aid of the metal blades 32, make it possible to restrict the displacement of the movable end plate 16 parallel to both the compression direction Y and the centering direction Z by exerting a compressive force on the movable end plate only in the compression direction Y. The design of the guiding system 30 is thus particularly simple and reduces the manufacturing cost of the fuel cell 10.

[0066] A further advantage of the guiding system 30 is that the force acts only on the movable end plate 16 and on the housing 18, and not on the stack 12. The stack 12 is thus suspended between the fixed end plate 14 and the movable end plate 16, and the mechanical forces exerted on the electrochemical cell are reduced.

[0067] Advantageously but not obligatorily, the fuel cell 10 is incorporated into the vehicle by being connected to the vehicle chassis using a vibration damping device, such as for example using springs and / or elastomeric studs, which is advantageously provided between the housing 18 and the vehicle chassis at that time. In particular, such a vibration damping device makes it possible to limit the vibrations received by the fuel cell. It is particularly advantageous to damp the relative movement of the fuel cell with respect to the vehicle chassis in order to reduce the mechanical constraints exerted on the entire fuel cell 10, in particular on the electrochemical cells of the stack 12. Such a vibration damping device is also particularly suitable for use with the guiding system 30 of the present invention, because the vibration damping device reduces the mechanical stresses exerted on the fuel cell and the guiding system makes it possible that the mechanical constraints remaining after damping do not lead to a displacement of the movable end plate 16 with respect to the housing 18, which could damage the electrochemical cells of the stack 12.

[0068] In the example, the two guide members 36A, 36B are two shoes which are fixed to the movable end plate 16, and the two inclined abutment portions 38A, 38B are fixed to the housing 18, more precisely to one of the side walls 22 of the housing, or are formed by the surfaces of two integral rails 40A, 40B. The shoes 36A, 36B exhibit a profile complementary to the profile of the inclined abutment portions 38A, 38B in order to enable optimal contact between the shoes and the inclined abutment portions.

[0069] Advantageously but not obligatorily, the shoes 36A, 36B can be made of or coated with a low-friction material, such as polytetrafluoroethylene, also known by the trade name "Teflon®", or can be made of a material whose surface conditions guarantee a low coefficient of friction.

[0070] Here, the two rails 40A and 40B extend parallel to each other and parallel to the stacking direction X, presenting a triangular profile. The inclined contact portions 38A, 38B are thus planar. In the example, the inclined contact portions 38A and 38B are formed by the surfaces of the rails 40A, 40B whose normal planes are directed towards the center of the movable end plate 16, as seen in FIG. 3.

[0071] In one alternative example, not shown, of the present invention, the inclined contact portions are formed by the surfaces of the rails 40A, 40B that are directed towards the outside of the movable end plate. Therefore, the inclined contact portions 38A and 38B diverge away from the wall 22 of the housing 18 to which the metal blade 32 is connected.

[0072] In one alternative example, not shown, of the present invention, the two inclined contact portions 38A and 38B are formed on two separate surfaces of the same rail.

[0073] In one alternative example, not shown, of the present invention, the rails 40A, 40B present a profile other than a triangular profile, such as, for example, a trapezoidal profile or any quadrilateral-shaped profile presenting at least one inclined surface so as to form the inclined contact portions 38A, 38B.

[0074] In one alternative example, not shown, of the present invention, the inclined contact portions 38A, 38B are not flat and present another profile, for example an arcuate or elliptical profile, which profile is seen perpendicular to the stacking direction X and extends along the stacking direction. In such an alternative example, the shape of the guide members 36A, 36B is adapted to match the profile of the inclined contact portions 38A, 38B. For example, the guide is ball-shaped.

[0075] In one alternative example, not shown, of the present invention, the guide members 36A, 36B are fixed to the housing 18, and the rails 40A, 40B forming the inclined contact portions 38A, 38B are fixed to the movable end plate 16.

[0076] In one alternative of the present invention, which is not illustrated, on the one hand, the positions of the compression member 32 and, on the other hand, the guide members 36A, 36B and the inclined contact portions 38A, 38B are reversed. In such an alternative, the compression direction Y is vertical and upwardly directed.

[0077] In practice, the fuel cell 10 can be mounted in other orientations with respect to 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.

[0078] In one alternative of the present invention, which is not illustrated, the guiding system 30 also comprises two lateral compression members which are arranged on either side, parallel to the centering direction Z, of the movable end plate 16 which exerts a compression force on the movable end plate parallel to the centering direction. Thus, a first of the two lateral compression members exerts a compression force on the movable end plate 16 with respect to the housing 18 along the centering direction Z, and a second of the two lateral compression members exerts a compression force on the movable end plate with respect to the housing in the direction opposite to the centering direction. In such an alternative, the centering of the movable end plate with respect to the fixed end plate 14 is reinforced.

[0079] Any feature described for one of the above embodiments or alternatives can be implemented for the other embodiments and alternatives described above, as far as technically possible.

Description of the reference numerals

[0080] 10 Fuel cell 12 Stack 12A First end 12B Second end 14 Fixed end plate 16 Movable end plate 18 Housing 20 Base 22 Side wall 24 Clamping system 26 Clamping flange 28 Compression spring 30 Guiding system 32 Compression member 32A First end 32B Second end 32C Central part 34 Fixing member 34A Holding plate 34B Holding element 36A, 36B Guide members 38A, 38B Inclined contact parts 40A, 40B Rails A32 Direction E24 Tightening force E32 Compression force F1, F2 Reaction forces L12 Length L38 Length X Lamination direction Y Compression direction Z Centering direction

Claims

1. - A housing (18), - A stack (12) of electrochemical cells extending along a stacking direction (X), - A fixed end plate (14) disposed at a first end (12A) of the stack and fixed to the housing, - A movable end plate (16) disposed at a second end (12B) of the stack and movable parallel to the stacking direction with respect to the housing, wherein the fixed (14) and movable (16) end plates clamp the stack (12) therebetween, - A guide system (30) for the movable end plate configured to enable displacement of the movable end plate in the stacking direction (X) and to limit displacement of the movable end plate perpendicular to the stacking direction In a fuel cell (10) comprising The guide system (30) for the movable end plate (16) comprises - At least one compression member (32) that exerts a compressive force (E32) on the movable end plate (16) with respect to the housing (18) along a compression direction (Y) perpendicular to the stacking direction (X), - Two guide members (36A, 36B) fixed to a first element (16, 18) from among the housing and the movable end plate, - Two inclined abutment portions (38A, 38B) fixed to a second element (16, 18) different from the first element from among the housing and the movable end plate and extending parallel to the stacking direction (X), each inclined abutment portion being inclined with respect to the compression direction (Y) and with respect to an alignment direction (Z) perpendicular to the stacking direction and the compression direction Comprising Under the influence of the compressive force (E32) exerted by the compression member (32), each guide member (36A, 36B) presses against one of the two inclined abutment portions (38A, 38B), and the two guide members align the movable end plate (16) parallel to the alignment direction (Z) with respect to the housing (18). A fuel cell (10), characterized in that.

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

3. The fuel cell (10) according to claim 1 or 2, wherein each inclined contact portion (38A, 38B) is formed by a surface 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 inclined contact portion (38A, 38B) is inclined by an angle (α) between 30° and 60°, preferably equal to 45°, with respect to the compression direction (Y).

5. The fuel cell (10) according to any one of claims 1 to 4, wherein the guide members (36A, 36B) are shoes presenting a profile complementary to the profile of the inclined contact portions (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 portion (32C), the two ends of the elastically deformable blade being connected to the first element (16, 18), and the central portion of the elastically deformable blade pressing against the second element (16, 18).

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

9. Contact of the first guide member (36A) with the first inclined contact portion (38A) generates a first reaction force (F1), and contact of the second guide member (36B) with the second inclined contact portion (38B) generates a second reaction force (F2). 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). The first components of the first and second reaction forces are equal in strength and direction and are in a direction opposite to the direction of the compression force (E32). The second components of the first and second reaction forces are equal in strength and opposite in direction. The fuel cell (10) according to any one of claims 1 to 8.

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

11. The fuel cell (10) further includes a clamping system (24) that tends to compress the stack (12) of the electrochemical cells by exerting a clamping force (E24) on the movable end plate (16) parallel to the stacking direction (X) with respect to the housing (18). The fuel cell (10) according to any one of claims 1 to 9.

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