Pressing device for pressing a fuel cell stack and fuel cell device with pressing device

Abstract

Pressing device (3) for pressing a fuel cell stack (2) in a pressing direction (P), comprising at least one spring-elastic pressing device (9) for applying a spring force acting in the pressing direction (P), and comprising at least one preloading device (9a) with which a preload of the pressing device (9) can be changed, wherein the preloading device (9a) has an adjusting element (12) and a support element (13), wherein the adjusting element (12) is rotatable relative to the support element (13) in an adjusting direction (E) extending around the pressing direction (P), and wherein the adjusting element (12) and the support element (13) have contacting contact surfaces (15, 16) that extend parallel to each other and obliquely to the pressing direction (P), characterized in that the contact surface (16) of the support element (13) has at least one locking element (22),and the contact surface (15) of the adjusting element (12) shall have at least one counter-locking element for the locking element (22), wherein the locking element (22) and the counter-locking element are configured to block movement of the adjusting element (12) in and / or against the adjusting direction (E).

Description

[0001] The invention relates to a pressing device for pressing a fuel cell stack in a pressing direction, comprising at least one spring-elastic pressing device for applying a spring force acting in the pressing direction, and at least one preloading device with which the preload of the pressing device can be changed. Furthermore, the invention relates to a fuel cell device comprising a fuel cell stack and a pressing device for pressing the fuel cell stack.

[0002] Pressing devices and fuel cell devices of the type mentioned above are generally known and, for example, from WO 99 / 27602 A1.

[0003] DE 10 2007 002 286 A1 describes a media supply plate for a fuel cell stack, wherein a fuel cell stack tension band encircles the fuel cell stack. A spring-elastic element tensions the fuel cell stack tension band and can be pre-tensioned by means of a pin and a stop, wherein the stop can be screwed in and out of the pin to change the pre-tension.

[0004] German patent application DE 10 2012 219 022 A1 discloses a clamping system for a fuel cell stack. The clamping system comprises a pressure plate resting against the fuel cell stack, an end plate arranged on the side of the pressure plate facing away from the fuel cell stack, and spring elements arranged between the pressure plate and the end plate.

[0005] Fuel cell devices utilize the chemical reaction of a fuel with oxygen to generate electrical energy. As core components, fuel cell devices contain membrane electrode assemblies, each of which can be configured as a composite of an ion-conducting membrane (particularly a proton-conducting membrane) and an electrode (anode and cathode) positioned on either side of the membrane. Additionally, gas diffusion layers can be arranged on both sides of the membrane electrode assembly, on the sides of the electrodes facing away from the membrane. Typically, the fuel cell device comprises a multitude of membrane electrode assemblies stacked together, at least partially forming the fuel cell stack, and the electrical outputs of these assemblies are additive.In the operation of the fuel cell device, the fuel, in particular hydrogen (H₂) or a hydrogen-containing gas mixture, is supplied to the anode, where electrochemical oxidation of the fuel takes place, releasing electrons. Protons are transported from the anode compartment to the cathode compartment via an electrolyte or the membrane, which tightly separates and electrically insulates the reaction spaces. This transport can be either water-bound or anhydrous. The electrons supplied at the anode are then transferred to the cathode via an electrical conductor. Oxygen or an oxygen-containing gas mixture is supplied to the cathode, causing a reduction of the oxygen and the acceptance of electrons. Simultaneously, in the cathode compartment, the oxygen anions react with the protons transported across the membrane to form water.By directly converting chemical energy into electrical energy, fuel cell devices achieve a better efficiency compared to other electricity generators due to the circumvention of the Carnot factor.

[0006] To influence the external dimensions of the fuel cell stack, for example during its manufacture or operation, and / or to ensure uniform compression of the individual fuel cells, a pressing device is provided. The preloading mechanism of the pressing device allows adjustment of the preload of the spring-loaded pressing device, so that the spring-loaded pressing forces acting on the fuel cells can be varied, thus making the fuel cells more or less compressible.

[0007] Conventional pressing devices use screws and nuts to change the preload. However, screws and nuts are cumbersome to operate.

[0008] The invention is therefore based on the objective of providing a pressing device for pressing a fuel cell stack as well as a fuel cell device with a fuel cell stack and with a pressing device pressing the fuel cell stack, wherein the pressing force acting on the fuel cell stack is easily changeable.

[0009] For the aforementioned pressing device, the problem is solved in that the pre-tensioning device comprises an adjusting element and a support element, wherein the adjusting element is rotatable relative to the support element in an adjustment direction extending around the pressing direction, and wherein the adjusting element and the support element have contact surfaces that are parallel to each other and inclined to the pressing direction. For the aforementioned fuel cell device, the problem is solved in that the pressing device is the pressing device according to the invention.

[0010] Because the pre-tensioning device has the adjusting element and the support element, whereby these elements contact each other at the contact surfaces which run at an angle to the pressing direction and can be rotated relative to each other around the pressing direction, the height of the pre-tensioning device along the pressing direction can be easily changed by rotating it, and thus the pre-tension of the spring-elastic pressing device can be changed without further ado.

[0011] The solution according to the invention can be further improved by various embodiments, each advantageous in itself and, unless otherwise stated, arbitrarily combinable with one another. These embodiments and their associated advantages are discussed below.

[0012] The contact surfaces can thus rise or fall monotonically, at least in sections, in the adjustment direction, so that twisting in one direction leads to an increase or decrease in preload. The contact surfaces can therefore be described as oppositely sloping contact ramps. If the contact surfaces are linear, for example, the preload changes uniformly with the twist. If the slope of the contact surfaces changes and increases or decreases, the preload can be changed more easily, especially with high existing spring forces. Alternatively, the preload can be changed more quickly, particularly with low existing spring forces.

[0013] The contact surfaces can be formed, at least in sections, along a helix that circumferentially surrounds the pressing direction, allowing the support and adjustment elements to be rotated relative to each other by a maximum of up to 360° to change the preload. The length of the contact surfaces can therefore correspond to the length of, or a fraction thereof, one turn of the helix. The length or extent of the contact surfaces around the pressing direction can be limited to a maximum of 360°, 270°, 180°, 90°, or values ​​in between. A single rotation of the adjustment element up to the relevant angle can thus change the preload from minimum to maximum or vice versa.

[0014] To ensure that the preload can be permanently adjusted without manually holding the support and adjustment elements in position relative to each other, the invention provides that the contact surface of the support element has at least one locking element and the contact surface of the adjustment element has at least one counter-locking element for the locking element. The locking element and the counter-locking element can be configured to block movement of the adjustment element in or against the adjustment direction. The locking element and the counter-locking element can be complementary to each other. For example, the at least one locking element can be wedge-shaped or sawtooth-shaped, and the counter-locking element can be complementary to the locking element.The mechanical interlocking of the locking element and counter-locking element allows the support element and the adjusting element to lock together in a predefined rotational position, thus preventing unintentional movement from this position in or against the adjustment direction. Furthermore, the locking element and counter-locking element provide tactile feedback to the operator of the preloading device, enabling easy preload adjustment. The contact surface of the support element can feature multiple locking elements, and the contact surface of the adjusting element can feature multiple counter-locking elements. For example, the contact surfaces can be completely covered with locking elements or counter-locking elements, at least along the adjustment direction.

[0015] The support element and the adjustment element can each have at least two contact surfaces that are essentially complementary to each other. In the adjustment direction, the contact surfaces of the support element and the contact surfaces of the adjustment element can be arranged one behind the other, i.e., consecutively in the adjustment direction. Transversely to the adjustment direction, i.e., in the pressing direction, the contact surfaces arranged one behind the other in the adjustment direction may not be arranged one behind the other.

[0016] The at least two contact surfaces of the support element or the adjusting element can be arranged at an angle of less than 180° or parallel to each other in a graphical development of a side view of the support element or the adjusting element. If the at least two contact surfaces are arranged at an angle of less than 180° to each other, rotation in the adjustment direction can initially increase the preload. If the rotational position is further changed in the adjustment direction so that the subsequent contact surfaces of the support element and the adjusting element come into contact with each other, the preload can be reduced. If the developed representations of the at least two contact surfaces of the support element or the adjusting element are parallel to each other, then, especially during large rotations in the adjustment direction of up to 180°, the interacting contact surfaces of the support element and the adjusting element may prevent the support element from tilting relative to the adjusting element, or vice versa. The interacting contact surfaces can flank an axis of rotation of the preloading device to improve the mechanical stability of the preloading device even at rotation angles of up to 180°.

[0017] The pressing device can have a contact wall for transmitting a pressing force generated by the pressing device to the fuel cell stack, and an outer wall. At least the adjusting element, the preloading device, and / or the pressing device can be arranged between the contact wall and the outer wall. The outer wall can have at least one opening through which the adjusting element is accessible. Even when the pressing device is mounted and can even compress the fuel cell stack, the preload, and thus the actual pressing force, can be easily changed due to the easy accessibility of the adjusting element. An adjustment section of the adjusting element can be designed so that it can be rotated using a tool, such as a wrench or socket.

[0018] The adjusting element or the support element can be attached to the contact wall. Preferably, the support element can be attached to the contact wall so that the adjusting element is rotatable relative to the support element and the contact wall. In particular, the support element can be formed integrally with the contact wall, which simplifies the assembly of the pressing device.

[0019] The adjusting element can have at least one retaining element that contacts the pressing device and may project into it. The retaining element can prevent lateral slippage or tilting of the adjusting element perpendicular to the pressing direction, for example, if the pressing device has a counter-retaining element. For example, the pressing device can have a central opening of a spring element, such as a disc spring, a stack of disc springs, or a coil spring, wherein the counter-retaining element is an inner surface of the central opening facing the retaining element. Alternatively or additionally, the spring element can have an outer surface comprising the counter-retaining element, against which the retaining element rests.

[0020] To ensure uniform rotation and prevent slippage or tilting in all directions perpendicular to the pressing direction, the pressing device can provide a rotary bearing for the adjusting element. For example, the counter-holding element can be formed along the outer surface of a circular cylinder whose longitudinal axis runs parallel to the pressing direction. Alternatively, the holding element can be a collar with a circular cross-section and a longitudinal axis running parallel to the pressing direction.

[0021] If the pressing device incorporates the spring element, such as a stack of disc springs, a coil spring, or a spring of a different shape, the length of the collar parallel to its longitudinal axis, i.e., in the pressing direction, can be smaller than the height of the spring element in the pressing direction, thus preventing a mechanical collision of the collar with the outer wall, even if the stack of disc springs is highly compressed.

[0022] The slope of the contact surfaces can be dimensioned such that, even at the maximum possible rotation of the adjusting element, the retaining element remains either spaced from or in contact with the outer wall. This prevents the retaining element from colliding with the outer wall or from being overtightened.

[0023] The pressing device may have a guide element that rests against the adjusting element and the support element. The guide element may be arranged in a cavity that may be present in the adjusting element and / or the support element and may rest against an inner surface of the adjusting element and / or the support element that runs parallel to the pressing direction and along the adjusting direction. The guide element may be designed to guide the relative movement of the adjusting element to the support element and / or the translation resulting from the rotation of the adjusting element along the pressing direction. For example, the guide element may be cylindrical or annular and, for instance, have a circular cross-section.

[0024] Alternatively or additionally, an external guide element can be provided, designed to guide the relative movement of the adjusting element to the support element and / or the translation resulting from the rotation of the adjusting element along the pressing direction. The guide element can bear against the outer surfaces of the adjusting element and / or the support element, which extend parallel to the pressing direction and in the adjustment direction. For example, the guide element may be toroidal or ring-shaped.

[0025] If the guide element is designed in a torus or ring shape, its central longitudinal axis can run parallel to the pressing direction.

[0026] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1 a schematic exploded view of an embodiment of the fuel cell device according to the invention; Fig. 2 a schematic perspective view of a further embodiment of the press device according to the invention; Fig. 3 a schematic sectional view of the embodiment of the Fig. 2; and Fig. 4 a schematic perspective view of a further embodiment of the press device according to the invention with a broken-out section.

[0027] The invention is explained below by way of example with reference to embodiments shown in the drawings. Unless otherwise specified in a particular case, the different features of the embodiments can be combined independently of one another, as has already been explained in the context of the individual advantageous embodiments.

[0028] First, the structure and function of a fuel cell device according to the invention are described with reference to the exemplary embodiment of the Fig. 1 described.

[0029] Fig. Figure 1 shows an embodiment of the fuel cell device 1 according to the invention, comprising a fuel cell stack 2 and an embodiment of the press device 3 according to the invention. The fuel cell device 1 is further shown with a housing cover 4. For clarity, the housing base of the fuel cell device 1 is not shown. The housing cover 4 and the housing base (not shown) of the fuel cell device 1 can connect the press device 3 to a counter-pressing device 5 in a force-transmitting manner. The fuel cell stack 2 is arranged between the press device 3 and the counter-pressing device 5. Furthermore, the fuel cell device 1 is shown in the Fig. 1 shown with several optional shape retention elements 6, which can at least limit or even prevent unwanted deformation of the fuel cell stack 2.

[0030] The pressing device 3 is shown with an outer wall 7 and a contact wall 8, wherein several spring-elastic pressing devices 9 are arranged between the outer wall 7 and the contact wall 8. The pressing devices 9 are designed to exert a pressing force acting in a pressing direction P on the contact wall 8 and from there on the fuel cell stack 2. The optionally provided contact wall 8 distributes the pressing force of the individual pressing devices 9 evenly on the side of the fuel cell stack 2 facing the pressing devices 9.

[0031] It may be sufficient to provide only one pressing device 9 to press the fuel cell stack 2 parallel to the pressing direction P. However, if different sections of the fuel cell stack 2 are to be pressed differently, it may be advantageous to provide several pressing devices 9 and to distribute them transversely to the pressing direction P, possibly evenly along the side of the fuel cell stack 2 facing the pressing devices 9. In particular, the outer wall 7 can be connected to the housing cover 4 and the housing base (not shown) in a force-transmitting manner.

[0032] The pressing device 9 is in the Fig. For the sake of clarity, only one prestressing device 9a is shown, the length of which can be changed along the pressing direction.

[0033] The counter-pressing device 5, which can also be force-transmittingly connected to the housing cover 4 and the housing base, can have a counter-pressing element 10 that transfers the pressing force applied in the pressing direction P by the pressing devices 9 to the housing cover 4 and the housing base. The counter-pressing element 10 can be an outer housing wall of the fuel cell device 1 and / or have media supply openings for the fuel cell stack 2. The outer wall 7 of the pressing device 3 can also form an outer housing wall of the fuel cell device 1.

[0034] Fig. Figure 2 shows a further embodiment of the press device 3 according to the invention schematically in a perspective view. For elements that are similar in function and / or structure to elements of the embodiment of the Fig. The same reference symbols are used for references 1 and 2.

[0035] The pressing device 3 of the exemplary embodiment of the Fig. 2 has two parallel rows of pressing devices 9. These two rows of pressing devices 9 are arranged between the outer wall 7 and the contact wall 8. The outer wall 7 has an opening 11 for each pressing device 9, which can also be referred to as an access opening. The pre-tensioning device 9a and, in particular, an adjusting element 12 of the pre-tensioning device 9a are accessible through the opening 11. In the pressing direction P, a support element 13 is provided behind each of the adjusting elements 12. Furthermore, at least one spring-elastic element 14, for example, a coil spring or a disc spring, can be arranged parallel to the pressing direction P in front of and / or behind the adjusting element 12 and / or the support element 13. In the exemplary embodiment of the Fig. 2 at least one spring-elastic element 14 is provided between the outer wall 7 and the adjusting element 12.

[0036] The adjusting element 12 and the support element 13 have contact surfaces that run obliquely to the pressing direction P and parallel to each other, extending helically around the pressing direction P. The adjusting element 12 can be rotated along an adjustment direction E extending around the pressing direction P, allowing the contact surfaces of the adjusting element 12 and the support element 13 to slide against each other. Since the contact surfaces run obliquely to the pressing direction P along the adjustment direction E, rotating the adjusting element 12 changes its distance to the contact wall 8 on which the support element 13 rests. Therefore, the length of the preloading device 9a changes when the adjusting element 12 is rotated in or against the pressing direction P.In the installed state of the press device 3, a rotation of the adjusting element E in or against the adjustment direction E can change a preload of the spring-elastic element 14, so that a spring force acting on the fuel cell stack 2 can be adjusted.

[0037] Fig. Figure 3 shows an exemplary embodiment of the Fig. 2 schematically in a cutaway side view.

[0038] In the cutaway side view of the Fig. Figure 3 shows the contact surfaces, with the contact surface of the adjusting element 12 pointing in the pressing direction P and designated with reference numeral 15. The contact surface of the support element 13, pointing opposite to the pressing direction P, is designated with reference numeral 16. The contact surfaces 15 and 16 extend around the pressing direction P in the adjusting direction E. Around the pressing direction P, the contact surfaces 15 and 16 extend along a helix, the pitch of which corresponds to the inclination of the contact surfaces 15 and 16 relative to the pressing direction P.

[0039] The adjusting element 12 is accessible through the opening 11. The adjusting element 12 can have an adjusting section 17, which is designed so that a tool, for example a screwdriver or a socket, can be attached to it. The tool can be attached to the adjusting section 17 through the opening 11. Using the tool, the adjusting element 12 can be easily rotated in or against the adjustment direction E to change the preload of the spring-elastic element 14.

[0040] The spring-elastic element 14 is shown by way of example as a stack of disc springs with a central opening. However, the spring-elastic element 14 can also have a different design. Particularly when the central opening is desired, the spring-elastic element 14 can also be designed as a coil spring. The central opening of the spring-elastic element 14 can be arranged such that the adjustment section 17 is located within it. Furthermore, the adjustment element 12 can have a retaining element 18 that prevents the adjustment element 12 from slipping or tilting transversely to the pressing direction P. The retaining element 18 can extend parallel to the pressing direction P and bear against the spring-elastic element 14.

[0041] For example, the retaining element 18 can be designed as a collar with a circular cross-section transverse to the pressing direction P, with a central longitudinal axis of this collar running parallel to the pressing direction P. The retaining element 18 can project into the spring-elastic element 14 and, in particular, into its central opening. However, if the spring-elastic element 14 does not have such a central opening, or if the retaining element 18 is not to be arranged in the central opening for other reasons, such as space constraints, the retaining element 18, which can optionally also be designed as a collar, can at least partially accommodate the spring-elastic element 14 and surround it in the adjustment direction E. This embodiment is shown in the Fig. 3 is formed with reference numeral 18a. It is also possible that the adjusting element has both retaining elements 18 and 18a. The at least one retaining element 18, 18a can bear against a surface of the spring-elastic element 14, with this surface forming a counter-retaining element.

[0042] If the spring-elastic element 14 has a circular cylindrical base shape or a circular cylindrical central opening, and the retaining element 18 and / or 18a is designed as a collar with a circular cylindrical cross-section, then the spring-elastic element 14 and the retaining element 18 and / or 18a can not only prevent the individual element 12 from slipping or tilting, but also allow the adjusting element 12 to rotate. The spring-elastic element 14 can therefore be designed as a pivot bearing for the adjusting element 12.

[0043] A cavity 19 can be formed between the adjusting element 12 and the contact wall 8, which can be bounded parallel to the pressing direction P by the adjusting element 12 and the contact wall 8, and transversely to the pressing direction P by the adjusting element 12 and the support element 13. This cavity 19 enables the pressing device 3 to be formed with the lowest possible weight.

[0044] Optionally, an internal guide element 20 can be provided in the cavity 19, which guides the relative movement of the adjusting element 12 to the support element 13 and / or the translation resulting from the rotation of the adjusting element 12 along the pressing direction P. The guide element 20 can bear against the inner surfaces of the adjusting element 12 and the support element 13, which extend parallel to the pressing direction P. For example, the guide element 20 is cylindrical or ring-shaped and, for instance, has a circular cross-section.

[0045] Alternatively or additionally, an external guide element 21 can be provided, which guides the relative movement of the adjusting element 12 to the support element 13 and / or the translation resulting from the rotation of the adjusting element 12 along the pressing direction P. The guide element 21 can bear against the outer surfaces of the adjusting element 12 and the support element 13, which extend parallel to the pressing direction P. For example, the guide element 21 is shaped like a torus or annulus.

[0046] If the guide element 20, 21 is designed in a torus or ring shape, its central longitudinal axis can run parallel to the pressing direction P.

[0047] Fig. Figure 4 schematically shows a further embodiment of the press device 3 according to the invention in a perspective view, with the adjusting element 12 shown partially broken out. The same reference numerals are used for elements that correspond in function and / or structure to elements of the previous embodiments. For the sake of brevity, only the differences from the previous embodiments are discussed below.

[0048] The contact surface 16 of the support element 13 is as shown in the Fig.4. The adjusting element 12 is identifiable as being equipped with locking elements 22. The locking elements 22 can be stepped, trapezoidal, sawtooth-shaped, or otherwise shaped. The contact surface 15 of the adjusting element 12 can be designed with counter-locking elements shaped complementarily to the locking elements 22. The locking elements 22 and the counter-locking elements prevent unintentional rotation of the adjusting element 12 around the pressing direction P, i.e., in or against the adjustment direction E. This ensures that a preload of the spring-elastic element 14, once set, does not change easily. REFERENCE MARK LIST: 1 Fuel cell device 2 fuel cell stacks 3 Pressing device 4 Housing covers 5 Counter-pressing device 6 retaining element 7 Exterior wall 8 contact wall 9 Pressing device 9a Pre-tensioning device 10 Counter-pressure element 11 Opening 12 Setting element 13 Support element 14 Spring-elastic element 15 Contact surface of the adjusting element 16 Contact surface of the support element 17 Setting section 18, 18a Holding element 19 Cavity 20 internal guide element 21 external guide element 22 Locking element E Direction of adjustment P Pressing direction

Claims

[1] Pressing device (3) for pressing a fuel cell stack (2) in a pressing direction (P), comprising at least one spring-elastic pressing device (9) for applying a spring force acting in the pressing direction (P), and comprising at least one preloading device (9a) with which a preload of the pressing device (9) can be changed, wherein the preloading device (9a) has an adjusting element (12) and a support element (13), wherein the adjusting element (12) is rotatable relative to the support element (13) in an adjusting direction (E) extending around the pressing direction (P), and wherein the adjusting element (12) and the support element (13) have contacting contact surfaces (15, 16) that extend parallel to each other and obliquely to the pressing direction (P), characterized by, that the contact surface (16) of the support element (13) has at least one locking element (22), and the contact surface (15) of the adjusting element (12) has at least one counter-locking element for the locking element (22), wherein the locking element (22) and the counter-locking element are configured to block movement of the adjusting element (12) in and / or against the adjusting direction (E). [2] Pressing device (3) according to claim 1, characterized by , that the contact surfaces (15, 16) rise or fall monotonically at least section by section in the adjustment direction (E). [3] Pressing device (3) according to claim 1 or 2, characterized by , that the contact surfaces (15, 16) are formed at least section by section along a helix circumferential to the pressing direction (P). [4] Pressing device (3) according to one of claims 1 to 3, characterized by, that the adjusting element (12) and the support element (13) each have at least two contact surfaces (15, 16) which are essentially complementary to each other. [5] Pressing device (3) according to any one of claims 1 to 4, characterized by , that the pressing device (3) has a contact wall (8) for transmitting a pressing force generated by the pressing device (3) to the fuel cell stack (2), and an outer wall (7), wherein the adjusting element (12) is arranged between the contact wall (8) and the outer wall (7), and wherein the outer wall (7) has at least one opening (11) through which the adjusting element (12) is accessible. [6] Pressing device (3) according to claim 5, characterized by , that the adjusting element (12) or the support element (13) is attached to the contact wall (8). [7] Pressing device (3) according to any one of claims 1 to 6, characterized by, that the adjusting element (12) has at least one retaining element (18, 18a) that contacts the pressing device (9). [8] Pressing device (3) according to any one of claims 1 to 7, characterized by , that the press device (9) provides a rotary bearing for the adjusting element (12). [9] Pressing device (3) according to any one of claims 1 to 8, characterized by , that the pressing device (9) has a guide element (20, 21) which rests against the adjusting element (12) and the support element (13). [10] Fuel cell device (1) comprising a fuel cell stack (2) and a pressing device (3) for pressing the fuel cell stack (2), characterized by , that the pressing device (3) is the pressing device (3) of one of claims 1 to 9.

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