Onboard fuel cell

Abstract

The invention relates to a motor vehicle fuel cell comprising: - a stack (14) of a plurality of planar cells held between two opposing flanges (32, 34); - a receptacle (12) adapted to receive said stack (14), said receptacle being adapted to be installed in a motor vehicle. Said receptacle (12) comprises a base (16) and four walls (18, 20) erected on said base in pairs opposite each other, said four walls defining an opening opposite said base; and one (32) of said two flanges is connected, in the vicinity of said opening, to at least two (18, 20) of said four facing walls, while the other of said two flanges (34) is connected, in the vicinity of said bottom (16) of said receptacle, to at least two (18, 20) of said four facing walls, in order to maintain said stack (14) in said motor vehicle so that the stack extends along a vertical component. Figure to be published with the abbreviation: Fig. 4

Description

Title of the invention: On-board fuel cell

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

[0002] Fuel cells known for embedded applications and in particular in motor vehicles, implement an electrolyte membrane of a polymer material forming a proton exchange membrane.

[0003] This type of fuel cell comprises a stack of cells composed of a plurality of bipolar plates and membranes held tightly against each other between two opposing flanges. The four opposite corners of these two flanges are, for example, respectively connected together by means of threaded rods and nuts, thus clamping the cells together.

[0004] Thus, this stack is housed in a receptacle. The latter comprises a base wall and four walls, two facing each other, erected on the base wall. The receptacle is then installed on the motor vehicles so that the base wall extends horizontally, while the stack of cells extends longitudinally, with the edges of the cells resting on the base wall.

[0005] The cells are then supplied with dihydrogen and dioxygen through a wall of the receptacle at the level of one of the flanges, and heat and water are removed, while electric current is produced.

[0006] The cells do indeed release a large amount of heat, so their thickness can increase considerably. In other words, when the fuel cell is operating, the length of the stack varies within the receptacle by several millimeters. The edge of the cells is then driven by friction against the bottom wall.

[0007] Thus, the stack must be mounted inside the receptacle, allowing it a certain degree of freedom. The vehicle's movements, alternating between accelerations and decelerations in various directions, can cause the stack to move relative to the receptacle and damage the cells against the receptacle walls.

[0008] Also, a problem which arises and which the present invention aims to solve is to provide an on-board fuel cell whose stack cells are protected from the movements of the vehicle.

[0009] In order to solve this problem, a motor vehicle fuel cell is proposed comprising:

[0010] - a stack of a plurality of planar cells held between two flanges opposite, the flat cells being stacked according to a stacking direction perpendicular to said flat cells;

[0011] - a receptacle suitable for receiving said stack, said receptacle being adapted to be installed in a motor vehicle.

[0012] Said receptacle comprises a base and four walls erected on said base two by two opposite, said four walls defining an opening opposite said base; and one of said two flanges is connected, in the vicinity of said opening, to at least two of said four opposite walls, while the other of said two flanges is connected, in the vicinity of said base of said receptacle, to at least two of said four opposite walls, in order to maintain said stacking in said motor vehicle so that said stacking direction extends along a vertical component.

[0013] Thus, a feature of the invention lies in the implementation of a vertical stack of cells inside the receptacle and the motor vehicle. In this way, and as will be explained in more detail later in the description, the stack can deform vertically while remaining held in a fixed position inside the receptacle. Indeed, the stack is suspended by one of the flanges near the opening and is held in place on the opposite side by the other flange, which is connected to the walls near the bottom of the receptacle.

[0014] Also, the fuel cell according to the invention comprises a plurality of screwable elements adapted to be engaged through at least two of said four walls and to be screwed respectively into the thickness of said two flanges. In this way, the flanges are securely connected to the receptacle and, consequently, the stack is held in a fixed position inside.

[0015] According to a particularly advantageous embodiment of the invention, said two of said four facing walls have four upper bores formed in the vicinity of said opening, each having a first diameter, while said plurality of screwable elements comprises at least four upper screwable elements, each having a diameter equal to said first diameter. The diameter of the screwable elements is equal to the first diameter of the bores, within functional clearance, in order to allow them to be inserted. Thus, these screwable elements make it possible to hold said one of said two flanges in a fixed position when the upper screwable elements are inserted through the upper bores and screwed into the thickness of said one of said two flanges.

[0016] Preferably, the four upper bores are made in two opposite walls of said four opposite walls, two in one and two others respectively opposite each other in the other.

[0017] Also, said two of said four facing walls preferably have, according to the invention, four lower bores made in the vicinity of said bottom and each having a second diameter, while said plurality of screwable elements comprises at least four lower screwable elements each having a diameter substantially smaller than the second diameter. Thus, and as will be explained in more detail later in the description, thanks to the difference in diameter between the lower screw-in elements and the lower bores, the screw-in elements can be driven into motion within the bores in transverse directions, thereby allowing the movement of the other of the two flanges, located near the bottom of the receptacle. In this way, the variations in the length of the cell stack are controlled by the other of the two flanges. The one of the two flanges, near the opening, remains in a fixed position.

[0018] According to a particularly advantageous embodiment of the invention, said two of said four facing walls have four other lower bores made respectively in the vicinity of said four lower bores opposite said base. Thanks to these four other bores, located respectively near said four lower bores, and forming four pairs of lower bores, the initial position of said other of said two flanges can be adjusted. Indeed, by design, the height of the cell stacks can vary by a substantial amount. This value can, for example, reach 10%.

[0019] Thus, thanks to these two adjustment options and also to the dimensions of the lower bores, the planned cell stack can be installed in the receptacle regardless of its dimensions. Obviously, the range of variation in its dimensions must not exceed a certain limit. This limit is, for example, 10%.

[0020] Furthermore, two of the four opposing walls have four recesses formed respectively between the four other lower bores and the four lower bores. These recesses advantageously have a rectangular cross-section. Their role will be explained later in the description.

[0021] Furthermore, the fuel cell also includes four oblong support washers, each having an opening to receive said at least four lower screw-in elements. These support washers are oblong so as to be able to cover the lower bores of each pair of lower bores, regardless of the position of the screw-in element in either bore of the pair of lower bores.

[0022] Advantageously, each of the oblong support washers has, along its length, two opposite parallel longitudinal edges and two opposite semicircular ends. The opening is then provided equidistant from the two parallel longitudinal edges. It is also provided in the vicinity of half the length of the washer.

[0023] Advantageously, each of the four oblong support washers has a surface adapted to receive an oblong O-ring. The surface has a continuous border along both opposite edges and both semicircular ends. A rib is formed in the continuous border to receive the oblong O-ring.

[0024] Furthermore, each of the four oblong support washers advantageously comprises, according to the invention, a tubular spacer extending from the face of the washer in line with the orifice. In this way, the spacer can pass through the wall of the receptacle and bear against the flange. Consequently, the washer can be press-fitted to the flange through the wall, the spacer bearing axially against the flange, while the face of the washer is pressed against the wall, with the O-ring substantially compressed. In this way, movement of the washer against the wall of the receptacle is permitted while maintaining its seal when the other flange is moved during the expansion of the stack.

[0025] Also, each of the four oblong support washers has a longitudinal centerline intersecting the orifice, and it includes a retaining lug extending from the surface face to the vicinity of the orifice, the retaining lug being intersected by the longitudinal centerline. Preferably, this lug has a rectangular cross-section adapted to engage in the recess located between the two lower bores of each pair of bores. In this way, the washer is prevented from rotating. It is held against the wall of the receptacle so that its two longitudinal edges extend vertically, as will be explained below.

[0026] Also, the oblong washers can be rotated 180° so that the spacer and then the screw-in element can be inserted into a second position depending on the stack length. In this second position, the locking lug remains engaged in the recess, while the oblong washers cover the bore, which is now free, to ensure the receptacle is sealed.

[0027] Other features and advantages of the invention will become apparent from the following description of a particular embodiment of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which:

[0028] [Fig.1] is a schematic front view of a fuel cell according to the invention;

[0029] [Fig.2] is a partial schematic view of the elements illustrated in [Fig.1];

[0030] [Fig.3] is a schematic top perspective view of an element of the object of the [Fig.l];

[0031] [Fig.4] is a schematic right-sectional view of the object in [Fig.1] along the plane IV - IV;

[0032] [Fig.5A] is a schematic perspective view of an element illustrated in [Fig.4]; and,

[0033] [Fig.5B] is a schematic axial cross-sectional view of the element shown in [Fig.5A] along the VB - VB plane.

[0034] Figure 1 shows, from the front, a fuel cell 10 according to the invention. It comprises a parallelepiped-shaped receptacle 12, inside which is installed a stack of cells 14.

[0035] The receptacle 12 has a bottom wall 16, two opposite side walls, a left side wall 18, and a right side wall 20, and two opposite longitudinal walls, a front wall 22 and a rear wall 24.

[0036] Also, the receptacle 12 is closed by a lid 26 having a continuous rim 28. Above the lid 26, there are supply elements 30 of the cell 10 with dioxygen and dihydrogen.

[0037] We will now refer to [Fig.2] showing the object of [Fig.1] without the receptacle 12 in order to describe in more detail the arrangement of the stack of cells 14. The lid 26 and the stack of cells 14 can be seen in [Fig.2].

[0038] Thus, the stack of cells 14 is made of bipolar plates and membranes held forcefully against each other between two opposite flanges, an upper flange 32 and a lower flange 34. In other words, the plates are stacked in the vertical direction V, perpendicular to the two flanges 32, 34 and to the cover 26.

[0039] Also, the stack of cells 14 is held in a vise between the two flanges 32, 34, and the two flanges 32, 34 are themselves held together by a plurality of inextensible straps 36 which loop around the upper flange 32 and a lower platform 38 extending under the face of the lower flange 34. And, compressible spring elements 40 are interposed between the lower platform 38 and the lower flange 34.

[0040] The spring elements 40 have a high degree of stiffness and inextensible straps 36 are sufficiently taut so that the two flanges 32, 34 hold all the cells of the cell stack 14 in a vise.

[0041] On the other hand, when the fuel cell 10 is in operation, it produces heat which tends to expand the stack of cells 14 in the vertical direction V. This expansion can be greater than 1%, for example 2%. Therefore, the height of the stack of cells 14 can vary by a few millimeters.

[0042] In this case, the two flanges 32, 34 move away from each other, and the spring elements 40 are compressed.

[0043] Before describing the dynamic behavior of the stacking of cells 14 inside the receptacle 12, we will first describe the latter in detail.

[0044] Furthermore, by design, the height of the cell stack 14 is not identical from one stack to another. It can vary by about twenty millimeters. Therefore, as will be seen, the receptacle 12 is also designed to accommodate cell stacks 14 of different heights.

[0045] It can thus be seen in [Fig.3] in top perspective. There we see the front wall 22 opposite the rear wall 24 and the left side wall 18 opposite the right side wall 20.

[0046] The walls 18, 20, 22, 24 erected on the bottom wall 16 of the receptacle define a continuous upper edge 39, which delimits an opening 41.

[0047] Thus, the two lateral walls 18, 20 have four upper bores made along the edge 39 of the receptacle 12: an upper left anterior bore 42 made in the left lateral wall 18 and opposite, an upper right anterior bore 44 made in the right lateral wall 20; an upper left posterior bore 46 made in the left lateral wall 18 and opposite, an upper right posterior bore 48 made in the right lateral wall 20. These four bores 42, 44, 46 and 48 receive respectively: an upper left anterior screw 45, an upper right anterior screw 47; an upper left posterior screw 49 and an upper right posterior screw 50.

[0048] The four bores 42, 44, 46, and 48 are respectively concealed by the four upper screws 45, 47, 49, and 50. They have a given initial diameter, while the upper screws 45, 47, 49, and 50 have the same diameter as the given initial diameter, except for functional clearance. In this way, the upper screws 45, 47, 49, and 50 can be inserted through the bores. They can be rotated within them. However, they are blocked transversely.

[0049] In addition, the two side walls 18, 20 have four first lower bores made in the vicinity of said bottom: a first lower front left bore 52 made in the left side wall 18 in line with the upper front left bore 42, and opposite, a first lower front right bore 54 made in the right side wall 20 in line with the upper front right bore 44; a first lower rear left bore 56 made in the left side wall 18, and opposite, a first lower rear right bore 58 made in the right side wall 20.

[0050] In addition, the two side walls 18, 20 have four second lower bores made respectively in the vicinity of said four lower bores opposite the bottom wall 16, namely: a second lower left anterior bore 62 made in the left side wall 18, and opposite it, a second lower right anterior bore 64 made in the right side wall 20; a second lower left posterior bore 66 made in the left side wall 18, and opposite it, a second bore lower posterior right 68 made in the right lateral wall 20. In other words, the second lower bores 62, 64, 66, 68 are respectively located above and opposite the first lower bores 52, 54, 56, 58.

[0051] Thus, the first lower bores 52, 54, 56, 58 are respectively paired with the second lower bores 62, 64, 66, 68. It will be observed that all the lower bores, 52, 62, 54, 64, 56, 66, 58, 68, have a second given diameter.

[0052] In addition, the two side walls 18, 20 have four rectangular recesses 72, 74, 76 and 78 extending transversely respectively between the first and second bores of each of the pairs of lower bores 52, 62; 54, 64; 56, 66 and 58, 68.

[0053] Also, it will be observed that the right side wall 20, towards the inside of the receptacle 12, includes a right oblong anterior boss 80 extending around the first 54 and second 64 right anterior lower bores and the rectangular recess 74. Also, the right side wall 20 has a right anterior rib 82 which extends from the right anterior boss 80 to the right anterior upper bore 44.

[0054] By the same token, the right side wall 20, towards the interior of the receptacle 12, includes a right oblong posterior boss 84 extending around the first 58 and second 68 right posterior lower bores and the rectangular recess 78. Also, the right side wall 20 has a right posterior rib 86 which extends from the right posterior boss 84 to the edge 39, approximately at two-thirds of the distance which extends between the right anterior upper bore 44 and the right posterior upper bore 48.

[0055] Also, the bosses 80, 84 and the corresponding ribs 82, 86 define lateral bearing spans. Their thickness is, for example, between 10 mm and 20 mm.

[0056] Conversely, and inside the receptacle, oblong left-hand bosses, not shown, surround respectively the first and second lower anterior left bores 52, 62 and the first and second lower posterior left bores 56, 66. Their thickness, however, is less than that of the right-hand bosses. For example, it is 10 times less.

[0057] The pairs of lower bores 52, 62; 54, 64; 56, 66 and 58, 68 are adapted to receive four fixing elements respectively, in two distinct positions depending on the height of the stack 14, as will be explained below.

[0058] A fastening element 88 according to the invention will be described in detail and with reference to [Fig.5A] and [Fig.5B].

[0059] Thus, the fixing element 88 comprises a screwable element 90 and an oblong washer 92 through which it is engaged.

[0060] The oblong washer 92 has an application face 94 opposite an external face 96. Also, it has two parallel longitudinal opposite edges 98, 100 and two semicircular opposite ends 102, 104.

[0061] Furthermore, the oblong washer 92 is pierced with an orifice 106 extended by a sleeve 108 projecting from the mounting face 84 and forming a tubular spacer. The sleeve 108 thus defines, at its end, a circular bearing surface 109.

[0062] In addition, the oblong washer 92 has on its application face 94, along the longitudinal edges 98, 100 and the opposite ends 102, 104 a continuous groove 110 in which an O-ring 112 is mounted.

[0063] Also, the oblong washer 92 includes a stop lug 114 located projecting from the application face 94 and along the sleeve 108. The stop lug 114 has a rectangular cross-section and is cut symmetrically by the median plane VB-VB of the oblong washer 92.

[0064] In addition, the screwable element 90 has a rod 116 extending through the orifice 106 and projecting from the sleeve 108, as well as a head 118 bearing against the external face 96 of the oblong washer 92.

[0065] It will be observed that the diameter d of the tubular sleeve 108 is less than the diameter of the lower bores 52, 62; 54, 64; 56, 66 and 58, 68. The advantages of this difference in diameter will be explained below.

[0066] Thus, the object of [Fig.2], made of a single block, is adapted to be installed inside the receptacle 12 illustrated in [Fig.3].

[0067] Before vertically inserting the stack of cells 14 inside the receptacle 12, the upper screws 45, 47, 49 and 50 are removed. The assembly is then slid inside the receptacle 12 and is guided in particular by the straight ribs 82, 86.

[0068] The lid 26 then rests on the edge 39 of the receptacle 12, while its rim 28 comes to rest against the upper and outer edge of the receptacle 12 along the edge 39.

[0069] In this position, the upper flange 32 extends at the level of the upper bores 42, 44, 46 and 48. Also, the lateral edge of the upper flange 32 has a threaded hole opposite each of these upper bores, while the rim 28 of the cover 26 has holes. Therefore, the upper screws 45, 47, 49 and 50 are respectively engaged in the holes in the rim 28 and then in the upper bores 42, 44, 46 and 48 so that they can be screwed into the threaded holes in the upper flange 32, as illustrated in [Fig. 4].

[0070] The section thus presented on [Fig.4] shows the upper front left bore 42 and right bore 44 through which the upper front left screw 45 and upper front right screw 47 are engaged. Also, the screws 45, 47 engage in the threads of the lateral edge of the upper flange 32.

[0071] It will be observed that the upper front right screw 47 is engaged through an upper tubular spacer 120, which is interposed between the right lateral wall 20 and the lateral edge of the upper flange 32. Thus, the upper flange 32 is forcibly immobilized relative to the wall 20, and at a distance from this wall 20.

[0072] On the contrary, the lateral edge of the upper flange 32 is held by force against the left lateral wall 18 and is immobilized there.

[0073] Of course, the upper rear left 49 and right 50 screws cooperate with the lateral edge of the upper flange 32 in the same way.

[0074] Thus, at this stage of assembly, the stack of cells 14 is suspended by the upper flange 32 from the upper part of the side walls 18, 20, near the upper edge 39.

[0075] Accordingly, the lower flange 34 extends to the level of the lower bores, 52, 62, 54, 64, 56, 66, 58, 68.

[0076] As indicated above, by design, the height of the stack of cells 14, for the same capacity, can vary by a few percent and even up to 10% compared to the minimum height.

[0077] Thus, thanks to the possibility of inserting the screwable elements 90 of the fixing elements 88 through the first lower bores 52, 54, 56, 58 or, second lower bores 62, 64, 66, 68 respectively located above the first, and moreover, since the lower bores 52, 62, 54, 64, 56, 66, 58, 68 have diameters not only greater than the stem 116 of the screwable elements 90 but also, than the diameter d of the tubular sleeve 108, then the lower flange 34 is always in a position to be able to be connected to the two lateral walls 18, 20.

[0078] As illustrated in [Fig.4], the lateral edges of the lower flange 34, which have tapped holes, extend substantially opposite the first lower bores 52, 54, 56, 58, of which only the first anterior lower bores 52, 54 appear on the section of [Fig.4].

[0079] The screwable elements 90 of the fixing elements 88 are thus inserted through the first lower bores 52, 54.

[0080] Also, the oblong washers 92 are then adjusted vertically, their application face 94 against the walls 18, 20 and their lug 114 oriented opposite to the bottom wall 16 so as to be able to engage through the recesses 72, 74.

[0081] Thus, the application face 94 of the oblong washers 92 covers the second lower bores 62, 64 in a sealed manner thanks to the O-rings 112 which are applied in compression against the lateral walls 18, 20.

[0082] Furthermore, the circular bearing surface 109 of the sleeve 108 of the oblong washer 92 is pressed against the lateral edges of the lower flange 34 when the screwable element 90 is itself tightened. In this way, the oblong washers 92 are held rigidly away from the lower flange 34 without the application face 94 of the oblong washers 92 coming under force against the side walls 18, 20. Only the O-rings 112 are substantially compressed against the side walls 18, 20.

[0083] The O-rings 112 not only ensure the sealing of the receptacle 12 because they extend around the bores, but also ensure the filtering of vibrations between the receptacle 12 and the stack of cells 14.

[0084] Of course, the first lower rear bores 66, 58, receive in the same way the screwable elements 90 and the oblong washers 92 to secure the two opposite edges of the lower flange 34 to the two lateral walls 18, 20.

[0085] It is then understood that the expansion of the stack of cells 14 along the vertical direction V, will be able to cause the lower flange 34 to move in translation along the same direction, since the diameter of the first lower bores 52, 64, 66, 58 is greater than the diameter d of the tubular sleeve 108.

[0086] In addition, the vertical movement of the screwable elements 90 causes, by the same token, the vertical movement of the oblong washers relative to the lateral walls 18, 20 of the receptacle 12 without compromising the seal, thanks to the O-rings 112.

[0087] Furthermore, and as illustrated in [Fig.4], if the stack of cells 14 had been less high, the lower flange 34 would have extended in the vicinity of the second lower bores 62, 64, 66, 68. Consequently, the screwable elements 90 of the fixing elements 88 would have been inserted through the second lower bores 62, 64.

[0088] Also, the oblong washers 92 would have been adjusted vertically, at 180° with respect to their position as described above, their application face 94 against the walls 18, 20, but their lug 114 oriented towards the bottom wall 16 so as to be able to engage through the recesses 72, 74. The oblong washers 92 would then have played the same role.

[0089] Thus, such characteristics make it possible not only to overcome the manufacturing tolerances of the cell stack, but also their dynamic behavior in operation.

Claims

Demands

1. Motor vehicle fuel cell comprising: - a stack (14) of a plurality of planar cells held between two opposing flanges (32, 34), the planar cells being stacked in a stacking direction perpendicular to said planar cells; - a receptacle (12) adapted to receive said stack (14), said receptacle being adapted to be installed in a motor vehicle; characterized in that said receptacle (12) comprises a base (16) and four walls (18, 20; 22, 24) erected on said base two by two opposite each other, said four walls defining an opening (41) opposite said base;and in that one (32) of the said two flanges is connected, in the vicinity of the said opening, to at least two (18, 20) of the said four facing walls, while the other of the said two flanges (34) is connected, in the vicinity of the said bottom (16) of the said receptacle, to at least two (18, 20) of the said four facing walls, in order to be able to maintain the said stacking (14) in the said motor vehicle in such a way that the said stacking direction extends along a vertical component.;

2. Fuel cell according to claim 1, characterized in that it comprises a plurality of screwable elements (45, 47, 49, 50; 90) adapted to be engaged through said at least two (18, 20) of said four walls and to be screwed respectively into the thickness of said two flanges (32; 34).

3. Fuel cell according to claim 2, characterized in that said two (18, 20) of said four facing walls have four upper bores (42, 44, 46, 48) made in the vicinity of said opening (41) and each having a first diameter, while said plurality of screwable elements comprises at least four upper screwable elements (45, 47, 49, 50) each having a diameter equal to said first diameter.

4. Fuel cell according to claim 2 or 3, characterized in that said two (18, 20) of said four facing walls have four lower bores (52, 54, 56, 58) made in the vicinity of said bottom (16) and each having a second diameter, while said plurality of screwable elements comprises at least four lower screwable elements (90) each having a diameter substantially smaller than said second diameter.

5. Fuel cell according to claim 4, characterized in that said two (18, 20) of said four facing walls have four other lower bores (62, 64, 66, 68) made respectively in the vicinity of said four lower bores (52, 54, 56, 58) opposite said bottom (16).

6. Fuel cell according to claim 5, characterized in that said two (18, 20) of said four facing walls have four recesses (72, 74, 76, 78) arranged respectively between said four other lower bores (62, 64, 66, 68) and said four lower bores (52, 54, 56, 58).

7. Fuel cell according to any one of claims 4 to 6, characterized in that it further comprises four oblong support washers (92) each having an orifice (106) for receiving said at least four lower screwable elements (90) respectively.

8. Fuel cell according to claim 7, characterized in that each of said four oblong support washers (92) has an application face (94) adapted to receive an oblong O-ring (112).

9. Fuel cell according to claim 8, characterized in that each of said four oblong support washers (92) comprises a tubular spacer (108) extending from said application face (94) in the continuation of said orifice (106).

10. Fuel cell according to claim 8 or 9, characterized in that each of said four oblong support washers (92) has a longitudinal median line intersecting said orifice (106), and in that it comprises a stop lug (114) extending from said application face (94) in the vicinity of said orifice (106), said stop lug being intersected by said longitudinal median line.