Power transmission device for a fuel cell system

Abstract

A power transmission device (38) for a fuel cell unit (1) or a fuel cell system (2), comprising a device housing (39), at least two current conductors (48, 50) for conducting the electrical current generated by a fuel cell stack (3), at least one contact element (79) arranged on each current conductor (48, 50) for mechanically and electrically contacting a respective counter-contact element (81), at least one counter-contact element (81) and one counter-contact element (81) each being mechanically and electrically connected to a respective contact element (79), at least one sensor cable (78) and one sensor cable (78) each being mechanically and electrically connected to a respective counter-contact element (81), at least one sensor for detecting the voltage and / or the current of the electrical current conducted through the at least two current conductors (48, 50) of the electrical current generated by the fuel cell stack (3),wherein the at least one contact element (79) is formed in one piece with the respective current conductor (48, 50).

Description

[0001] The present invention relates to a power transmission device for a fuel cell unit or a fuel cell system according to the preamble of claim 1, a fuel cell unit according to the preamble of claim 14 and a fuel cell system according to the preamble of claim 15. State of the art

[0002] Fuel cell units, as galvanic cells, convert continuously supplied fuel and oxidant into electrical energy and water via redox reactions at an anode and cathode. Fuel cells are used in a wide variety of stationary and mobile applications, for example, in homes without a connection to the power grid, in motor vehicles, rail transport, aviation, space travel, and shipping. Fuel cell units consist of multiple fuel cells arranged in a fuel cell stack.

[0003] Within each fuel cell, there is a gas chamber for the oxidizer, meaning a flow chamber for the passage of an oxidizer, such as ambient air containing oxygen. This gas chamber for the oxidizer is formed by channels on the bipolar plate and a gas diffusion layer for the cathode. The channels are thus formed by a corresponding channel structure on the bipolar plate, and the oxidizer, namely oxygen, reaches the cathodes of the fuel cells through the gas diffusion layer. A similar gas chamber for the fuel is formed at each anode.

[0004] Fuel cell systems consist of various components, such as a fuel supply system, an oxidizer supply system, and the fuel cell stack. The fuel cells contain a proton exchange membrane for conducting protons. Within the fuel cell system, the gas delivery unit of the oxidizer supply system is driven by an electric motor.

[0005] In a fuel cell system or fuel cell unit, a power transmission device is used to transfer the electrical current generated in the fuel cell stack. The power transmission device comprises a housing, and within the housing are two conductors configured as busbars for conducting the current through the device. The power transmission device also includes a sensor for detecting the voltage and / or current flowing through the two busbars. For this purpose, a contact element is provided on each busbar, and a corresponding contact element is provided on a sensor cable. The contact element is electrically and mechanically connected to the corresponding contact element, allowing the electrical current or voltage to be transferred from each busbar to each sensor cable.The contact element is, for example, formed by a bolt attached to the busbar, and the mating contact element is a cable lug. The bolt has an external thread, and it is inserted into an opening in the cable lug. The cable lug is then contacted by a nut between the nut and the busbar, applying pressure. Such contact elements are designed as a separate component in addition to the busbar and require complex attachment. This results in high manufacturing costs for the busbar with the contact elements.

[0006] DE 10 2015 117 333 B4 discloses a fuel cell system comprising: a fuel cell configured to carry out an external power supply; a coolant circulation line through which a coolant circulates for cooling the fuel cell; a cooler mounted on the coolant circulation line; a water pump configured to circulate a coolant in the coolant circulation line; a flow divider valve configured to control the flow rate of the coolant flowing through the cooler; a blower configured to supply air to the cooler; and a controller. Disclosure of the invention Advantages of the invention

[0007] A power transmission device according to the invention for a fuel cell unit or a fuel cell system, comprising a device housing, at least two conductors for transmitting the electric current generated by a fuel cell stack, at least one contact element arranged on each conductor for mechanical and electrical contact with each counter-contact element, at least one counter-contact element and each counter-contact element being mechanically and electrically connected to each contact element, at least one sensor cable and each sensor cable being mechanically and electrically connected to each counter-contact element, preferably at least one sensor for detecting the voltage and / or current of the electric current generated by the fuel cell stack and conducted through the at least two conductors, wherein the at least one contact element is formed integrally with each conductor.Advantageously, the production of the conductor is inexpensive because the contact element does not have to be manufactured as a separate component and then attached to the conductor.

[0008] In another embodiment, the at least one current conductor is designed as a busbar, in particular in a ribbon shape and / or in a rectangular cross-section.

[0009] In a supplementary variant, the width of the busbar is significantly larger than the thickness of the busbar; preferably, the width of the busbar is greater than 2 times, 3 times, 5 times, 7 times or 10 times the thickness of the busbar, particularly at a main section.

[0010] In an additional embodiment, at least one busbar is made up of several layers.

[0011] In a supplementary embodiment, the layers of each busbar are connected to each other by material bonding and / or force bonding and / or form bonding, for example with an aligned bore in the layers and in the aligned bores a fixing element, for example a bolt or a rivet, is arranged for connecting the layers to each other and / or with at least one press-fit connector and / or with at least one rivet and / or with punch compaction.

[0012] Preferably, the layers of each busbar are connected to each other by a welded joint, in particular a resistance welded joint.

[0013] In another embodiment, the at least one contact element is formed by a projection on the at least one layer of the busbar.

[0014] In particular, the number of layers from which each busbar is formed is greater than or identical to the number of layers from which each contact element of each busbar is formed.

[0015] In an additional embodiment, the thickness of each contact element on each busbar is smaller or identical to the thickness of each busbar with this contact element.

[0016] In another embodiment, the at least one contact element is designed as a contact nozzle that is essentially cuboid or band-shaped.

[0017] In a supplementary variant, the width of the contact nozzle is significantly larger than the thickness of the contact nozzle; in particular, the width of the contact nozzle is larger than 2 times, 3 times, 5 times, 7 times or 10 times the thickness of the contact nozzle, especially on a main section.

[0018] In a further embodiment, each contact element of each layer comprises a tapered section with a decreasing thickness and / or width and a main section with a substantially constant thickness and / or width, in particular with a deviation of less than 10%, 5%, 3% or 1%.

[0019] In an additional embodiment, at least one mating contact element is designed as a contact plug, in particular a flat contact plug.

[0020] A fuel cell unit according to the invention for the electrochemical generation of electrical energy, comprising stacked fuel cells and the stacked fuel cells forming a fuel cell stack, a power transmission device, wherein the power transmission device is designed as a power transmission device as described in this patent application.

[0021] A fuel cell system according to the invention for converting chemical energy into electrical energy, comprising at least one fuel cell unit with stacked fuel cells, the stacked fuel cells forming a fuel cell stack, at least one oxidant supply system for oxidant, at least one fuel supply system, at least one cooling system, and a power transmission device, wherein the power transmission device is designed as a power transmission device as described in this patent application.

[0022] In a further embodiment, at least one fixing element, in particular a screw, for fixing the main wall, in particular the top main wall, of the housing of the power transmission device is covered by the locking cover, so that this at least one fixing element for fixing the main wall can only be removed after the locking cover has been removed, and thus the main wall, in particular the top main wall, of the housing of the power transmission device can only be removed after the locking cover has been removed.

[0023] Preferably, the layers of each power rail are loosely stacked.

[0024] In another embodiment, the power transmission device includes a power switch for deactivating and activating the transmission of the electrical current generated by the fuel cell stack to a main consumer.

[0025] In another embodiment, the current transmission device comprises a resistance current switch for deactivating and activating the transmission of electric current from the fuel cell unit through an electrical resistance as an electrical short circuit of the fuel cell stack.

[0026] Preferably, the layers of each busbar are connected to each other using an adhesive bond.

[0027] In an additional embodiment, the layers are stacked in alignment in each power rail.

[0028] In a supplementary embodiment, the layers of the busbar are designed with an identical geometry and / or shape, in particular without taking into account the at least one contact element.

[0029] In a supplementary embodiment, the conductor is at least partially, and in particular completely, made of metal, for example copper.

[0030] In a supplementary variant, the length of a main section of each contact nozzle is significantly greater than the length of a tapered section of each contact nozzle; preferably, the length of a main section of each contact nozzle is greater than 2 times, 3 times, 5 times, 7 times, or 10 times the length of a tapered section of each contact nozzle. In an additional embodiment, the geometry of the contact element, in particular the contact nozzle, is complementary to the geometry of the opposing contact element, preferably the contact plug, in particular the flat contact plug.

[0031] Preferably, an electrical fuse for an electrical component of the fuel cell unit or fuel cell system is arranged within the housing of the power transmission device. This advantageously protects the electrical fuse from mechanical damage due to its placement within the housing.

[0032] In another embodiment, the electrical fuse is covered by a fuse cover.

[0033] In a complementary variant, the electrical fuse is accessible from the outside of the device housing after removing the fuse cover, allowing for replacement, particularly when the power transmission device is located in and / or attached to a fuel cell system. The electrical fuse can thus be easily replaced simply by disassembling or removing the fuse cover.

[0034] In an additional embodiment, the device housing comprises a main wall, in particular a deck main wall, and the safety cover is attached to and / or on the main wall.

[0035] In another embodiment, the length of the main wall is greater than 1.2 times, 1-5 times, 2 times or 3 times the length of the safety cover.

[0036] Preferably, the width of the main wall is greater than 1.2 times, 1-5 times, 2 times or 3 times the width of the safety cover.

[0037] In a further embodiment, the main wall has a safety opening, and this safety opening is, in particular, completely covered by the safety cover. With the safety cover installed, the housing of the power transmission device is thus completely closed and fluid-tight from the environment. As a result, no substances can enter the interior enclosed by the housing from the outside.

[0038] In an additional variant, a seal is arranged between the main wall and the locking cover to seal the locking opening from the environment; in particular, the seal is formed completely around the locking opening. Preferably, the seal is arranged on the rear side of the locking cover and is connected to the locking cover, in particular by a material bond and / or a positive fit and / or a force-fit, so that the seal is always attached to the locking cover during assembly and disassembly from the main deck wall or the main wall.

[0039] In a further embodiment, an electrical mating connector is provided on the outside of the power transmission device for electrical connection with an electrical connector and a power cable. The electrical mating connector serves for electrical connection with the electrical connector, preferably for low voltage and / or data.

[0040] The power transmission device is advantageously designed such that the safety cover can only be removed from the device housing, in particular the main wall, if no electrical connector, preferably with a power cable, is inserted into the electrical mating connector.

[0041] In an additional embodiment, a projection with an opening is formed on the locking cover, in particular formed in one piece with the locking cover, and in the assembled state of the locking cover and the arrangement of the electrical connector with the power cable in the electrical mating connector, the electrical connector and / or the power cable is arranged in the opening of the projection, so that the disassembly of the locking cover from the electrical connector and / or the power cable is mechanically blocked by the electrical connector and / or power cable in the opening.

[0042] In another variant, the extension is shaped like a stirrup.

[0043] In a supplementary embodiment, at least one positioning element is formed on the fuse cover and at least one counter-positioning element is formed on the remaining current transmission device, in particular the device housing of the current transmission device, and each positioning element is arranged in each counter-positioning element, so that the movement, in particular the initial phase of the movement, for disassembling the fuse cover from the current transmission device is essentially only a translational movement of the fuse cover to increase the distance between the fuse cover and the main wall, in particular during contact between each positioning element and each counter-positioning element.Essentially only a translational movement preferably means that the locking cover is aligned essentially parallel to the main wall or deck wall, particularly with a deviation of less than 30°, 20°, or 10°, and / or that the distance between the main wall or deck wall and the locking cover is essentially identical, particularly with a deviation of less than 30%, 20%, or 10%. The respective positioning element and counter-positioning element thus form a sliding bearing and / or a positive guide for the translational movement between the locking cover and the main wall. In a supplementary embodiment, the path of movement during the initial phase of the relative movement between the locking cover and the main wall is less than 20 cm, 10 cm, 5 cm, 3 cm, or 1 cm.

[0044] In another variant, the power transmission device can be cooled using the cooling system of the fuel cell system.

[0045] Preferably, the power transmission device comprises at least one hydraulic coupling device, in particular two hydraulic coupling devices, for passing a coolant, in particular cooling fluid, for temperature control, in particular cooling, of the power transmission device.

[0046] In a supplementary embodiment, the device housing, in particular the main wall and / or the at least one side wall and / or the bottom wall and / or the sub-housing of the device housing, is at least partially, in particular completely, made of plastic, in particular by injection molding.

[0047] In an additional embodiment, the power transmission device comprises at least one pressure equalization device, in particular a diaphragm or a compensating piston, for changing the volume of the interior space bounded by the device housing, preferably for changing the volume by at least 0.5%, 1%, 3%, 5% or 10%.

[0048] In particular, the power transmission device comprises a sub-housing for dividing the interior of the power transmission device into a partial interior containing the fuse and the remaining interior outside the partial interior, and the sub-housing at least partially limits the partial interior.

[0049] It is advantageous for the interior of the power transmission device, which is bounded by the device housing, to be sealed fluid-tight from the environment.

[0050] In a further embodiment, the components of the fuel cell system, for example the fuel cell unit and / or the oxidizer supply system and / or the fuel supply system and / or the cooling system and / or the power transmission device, are attached as a module to a common support device and preferably the fuel supply system of the module does not include a pressure vessel for the fuel and preferably a connection for a fuel line.

[0051] In a further embodiment, the oxidizing agent supply system comprises an oxidizing agent supply line and / or an oxidizing agent discharge line and / or a gas conveying device, in particular with an electric motor, and / or a humidifier.

[0052] In a supplementary variant, the fuel supply system includes a recirculation fuel line and / or a recirculation fuel conveying device and / or a water separator and / or a container, in particular a pressure vessel, for fuel and / or an injector and / or a pressure reducer and / or a heat exchanger for fuel.

[0053] In an additional embodiment, the cooling system for temperature control of the fuel cell stack and preferably the power transmission device comprises at least one coolant line and / or a heat exchanger for conducting heat from the coolant into the ambient air and / or a pump driven by an electric motor for circulating the coolant.

[0054] Preferably, the support structure of the module is designed as a frame and / or a truss and / or a grid and / or a plate.

[0055] In another embodiment, the area of ​​the main wall is larger than 1.2 times, 1-5 times, 2 times or 3 times the area of ​​the safety cover.

[0056] In another embodiment, the electrical fuse within the device housing of the power transmission device is an electrical fuse for an electric motor of a gas conveying device for supplying the fuel cell stack with oxidizer.

[0057] In a supplementary embodiment, the at least one gas conveying device is designed as a blower and / or compressor and / or compressor.

[0058] In a further embodiment, the fuel cells each comprise an ion exchange membrane, in particular a proton exchange membrane and / or anion exchange membrane, an anode, a cathode, at least one gas diffusion layer and a bipolar plate.

[0059] Preferably, the fuel is hydrogen, hydrogen-rich gas, reformate gas or natural gas.

[0060] For practical purposes, the fuel cells and / or components of the fuel cells are essentially flat and / or disc-shaped.

[0061] In another embodiment, the fuel cell unit comprises a housing and / or a connection plate. The fuel cell stack is enclosed by the housing and / or the connection plate. Preferably, the fuel cell unit comprises the fuel cell stack and preferably the housing.

[0062] In a complementary variant, the oxidizing agent is air with oxygen or pure oxygen.

[0063] Preferably, the fuel cell unit is a PEM fuel cell unit with PEM fuel cells, or a SOFC fuel cell unit with SOFC fuel cells, or an alkaline fuel cell (AFC). Brief description of the drawings

[0064] Exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings. These show: Fig. 1 a highly simplified representation of a fuel cell system, Fig. 2 a perspective view of a power transmission device with a fuse cover for a fuse, Fig. 3 a perspective view of the power transmission device according to Fig. 2 without the fuse cover (removed) for the fuse, Fig. 4 a perspective view of the fuse cover for securing the power transmission device according to Fig. 2, Fig. 5 a perspective view of the power transmission device according to Fig. 2 without main wall (disassembled), Fig. 6 a perspective view of a sub-housing for the fuse with fuse, Fig. 7 a perspective view of a busbar in a first embodiment of the power transmission device according to Fig. 2, Fig. 8 a perspective view of layers of a busbar as an exploded view in a second embodiment, Fig. 9 a busbar in a second embodiment made of several stacked layers, Fig. 10 a longitudinal section or a top view of a contact nozzle in a first embodiment, Fig. 11 a further longitudinal section or a side view of the contact nozzle in the first embodiment Fig. 10, Fig. 12 a longitudinal section or a top view of a contact nozzle in a second embodiment, Fig. 13 a further longitudinal section or a side view of the contact nozzle in the second embodiment Fig. 12, Fig. 14 a perspective view of a flat contact connector.

[0065] In Fig. Figure 1 shows a fuel cell unit 1 as a fuel cell stack 3, i.e., as a fuel cell stack 3. The fuel cell unit 1 comprises the fuel cell stack 3, a housing 13, and a connection plate 15. The housing 13 defines an interior space 14. The connection plate 15 also functions as a housing 13 and is fixed to the rest of the housing 13 by fixing elements 16, in particular screws 17. In the fuel cell stack 2, fuel cells 4 are stacked and arranged in a straight line as PEM fuel cells 5. Due to the large number of stacked fuel cells 4, approximately 300 to 400, these are arranged in Fig. 1. Not all components are shown for the sake of simplicity. The principle of fuel cells 4 is that electrical energy, or electric current, is generated by means of an electrochemical reaction. Hydrogen (H2) is fed to an anode (not shown) as a gaseous fuel in recirculation mode, and the anode forms the negative terminal. A gaseous oxidizing agent, namely air with oxygen, is fed to a cathode (not shown); that is, the oxygen in the air provides the necessary gaseous oxidizing agent. Reduction (electron uptake) takes place at the cathode. Oxidation (electron release) occurs at the anode. Fuel cells 4 also include an ion exchange membrane, specifically a proton exchange membrane (PEM), which is positioned between the anode and the cathode.On both sides of the PEM, facing the gas spaces, the electrodes are located as the anode and cathode (not shown). A unit consisting of the PEM and anode and cathode is called a membrane electrode assembly (MEA) (not shown). A gas diffusion layer (GDL) lies on top of the anode and cathode. A bipolar plate (not shown) rests on the GDL. The electrically conductive bipolar plate serves as a current collector, for water drainage, and for conducting the reaction gases.

[0066] In the fuel cell unit 1, the fuel cells 4 are arranged between two clamping elements 18, which act as clamping plates 19. An upper clamping plate 20 rests on the uppermost fuel cell 4, and a lower clamping plate 21 rests on the lowermost fuel cell 4. The clamping elements 18 exert a compressive force on the fuel cells 4; that is, the upper clamping plate 20 exerts a compressive force on the uppermost fuel cell 4, and the lower clamping plate 21 exerts a compressive force on the lowermost fuel cell 4. This clamps the fuel cell stack 3 to ensure a tight seal for the fuel, oxidizer, and coolant, particularly due to elastic seals, and also to minimize the electrical contact resistance within the fuel cell stack 3.To clamp the fuel cells 4 with the clamping elements 18, four connecting devices 22 are designed as bolts 23 on the fuel cell unit 1, which are subjected to tensile stress. The four bolts 23 are rigidly connected to the clamping plates 19.

[0067] The connection plate 15 and the lower clamping plate 21 each have an opening for introducing recirculating fuel into the recirculating fuel channels. They also each have an opening for discharging recirculating fuel from the recirculating fuel channels. The connection plate 15 and the lower clamping plate 21, as clamping elements 18, each have an opening 35 for introducing oxidizer and an opening 36 for discharging oxidizer, as well as openings (not shown) for introducing and discharging coolant. Thus, the connection plate 15 and the lower clamping plate 21 have a total of six openings (only partially shown). Fig. 1 shown).

[0068] A fuel cell system 2 comprises, in addition to the fuel cell unit 1, an oxidant supply system 26 for supplying the fuel cell stack 2 with air as the oxidant. The oxidant supply system 26 includes a gas conveying device 27, for example a blower, a compressor, a turbo compressor, which is driven by an electric motor, i.e., an electric drive motor as an electric unit, and / or a turbine (not shown), and oxidant lines 28 as oxidant supply line 24 and oxidant discharge line 25, as well as a humidifier 37.

[0069] The fuel cell system 2 comprises, in addition to the fuel cell unit 1, a fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel. The fuel supply system 29 preferably comprises a pressure vessel 30, a fuel line 31 as a process fluid line, valves (not shown) for fuel, in particular an injector (not shown) for controlling the volume flow of fuel introduced from the fuel line 31 into the recirculation line 32, a heat exchanger (not shown) for fuel, a pressure reducer (not shown), a recirculation fuel line 32 as a process fluid line, a recirculation fuel conveying device 33, an electric motor (not shown) for driving the recirculation fuel conveying device 33, and a water separator 34 for separating water from the recirculation fuel.A water tank (not shown) for collecting the water collected in the water separator 34, a drain valve (not shown) for draining water from the water tank, and a purge valve (not shown) for releasing recirculated fuel into the environment. In the fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel, the hydrogen stored in the pressure vessel 30 at a high pressure of, for example, 400 bar is fed to the fuel cells 4 via the fuel line 31. After the fuel has passed through the fuel cells 4, the hydrogen is not completely consumed.The hydrogen extracted from the fuel cells 4 is then fed back to the fuel cells 4 in a closed loop via the recirculation fuel line 32. The recirculation fuel conveying device 33 is used to pump the recirculation fuel through the recirculation fuel line 32. After passing through the fuel cells 4, the moisture content of the fuel increases. To prevent excessive water or moisture content in the recirculation fuel, the fuel supply system 29 includes a water separator 34. The water separated in the water separator 34 is collected in the water tank (not shown) and discharged into the environment via the drain valve (not shown). Excess recirculation fuel is discharged into the environment via the purge valve (not shown).

[0070] Fuel cell system 2 comprises, in addition to fuel cell unit 1, a cooling system (not shown) for temperature control of the fuel cell stack 3. This cooling system includes coolant lines (process fluid lines), a heat exchanger, and a pump driven by an electric motor for circulating the coolant. The coolant is routed through coolant channels in the bipolar plates of the fuel cells 4, and the heat is dissipated to the environment via the heat exchanger. Fuel cell system 2 also includes, in addition to fuel cell unit 1, the oxidizer supply system 26, the fuel supply system 29, and the cooling system (not shown) as a coolant supply system.

[0071] The proton exchange membranes of the fuel cells 4 must be sufficiently moistened to conduct protons. For this reason, the fuel cell system 2 has a humidifier 37. The humidifier 37 transfers or conducts moisture and / or water from the oxidant exhaust gas discharged from the fuel cell stack 3 in the oxidant discharge line 25, 28 to the oxidant in the oxidant supply line 24, 28. For this purpose, the humidifier 37 contains corresponding membranes (not shown) for transferring or conducting the moisture and / or water from the oxidant exhaust gas to the oxidant, which is introduced into the fuel cell stack 3.

[0072] The essential components of the fuel cell system 2 are arranged in a compact module requiring little installation space, preferably without a pressure vessel 30. Fig. Figure 1 shows the fuel cell system 2 only to illustrate its operation, without showing the module. The essential components of the fuel cell system 2 are the fuel cell unit 1 with the fuel cell stack 3, the oxidizer supply system 26, the fuel supply system 29, the cooling system, and a power transmission device 38.

[0073] The electrical current generated by the fuel cell stack 3 is transmitted via power lines and through the power transmission device 38 ( Fig. 2 to 14) to a main consumer (not shown), in particular an electric drive system of a motor vehicle. The current transmission device 38 serves to conduct this current from the fuel cell stack 3 to the main consumer and to monitor the current generated by the fuel cell stack 3, in particular with regard to the electrical voltage and the electrical current that is conducted from the fuel cell stack 3 to the main consumer (not shown).

[0074] The power transmission device 38 comprises a device housing 39, preferably made of plastic. The device housing 39 comprises a bottom wall 40, side walls 41, and a top main wall 42. A locking opening 47 is provided in the top main wall 42 ( Fig. 3) for an electrical fuse 52 built into and integrated into the power transmission device 38 ( Fig. 3 and Fig. 6) for an electrical unit of the fuel cell system 2, in particular an electric drive motor for the gas conveying device 27. The bottom wall 40, the side wall 41, and the main top wall 42 are detachably connected to one another by fixing elements 43 in the form of screws 44. Connecting tabs 45, 46 are formed on the side walls 41 and the bottom wall 40. On the bottom wall 40, connecting tabs 45 are formed as extensions, and on the side wall 41, connecting tabs 46 are formed as extensions of the side wall 41, each integrally formed with the bottom wall 40 or the side wall 41. These connecting tabs 45, 46 are connected to one another by the fixing elements 43 in the form of the screws 44, so that the bottom wall 40 is fastened to the side walls 41. Additionally, the main deck wall 42 is fixed to the connecting tabs of the side walls 41 by means of the fixing elements 43 ( Fig. 2 and Fig. 3) The bottom wall 40, the side walls 41, and the main deck wall 42 are each manufactured in one piece from plastic by injection molding. Completely circumferential seals (not shown) are arranged between the bottom wall 40, the side wall 41, and the main deck wall 42, so that the interior space bounded by the device housing 39 is sealed fluid-tight from the environment.

[0075] An opening (not shown) is formed in the base wall 40, and the two power lines (not shown) from the fuel cell stack 3 are inserted through this opening into the interior space bounded by the device housing 39. These two power lines are sealed fluid-tight at the openings with respect to the environment. Inside the device housing 39, these two power lines are connected to a first conductor 48, forming a first busbar 49, and a second conductor 50, forming a second busbar 51. The two busbars 49 and 51 serve to conduct the electrical current generated by the fuel cell stack 3 through the device housing 39 and are then connected to a mating connector 75 on the outer side of a side wall 41 via power lines.The mating connector 75 for the main consumer incorporates two appropriately sized electrical contact elements (not shown). The interior space bounded by the device housing 39 is fluid-tight from the environment. Due to temperature changes, pressure differences can occur within the interior space bounded by the device housing 39. Therefore, two pressure equalization devices 67, acting as diaphragms 68, allow the volume of the interior space of the power transmission device 38 to be adjusted for only a small change in pressure within the power transmission device 38 at fluctuating temperatures. The device housing 39 also features two mounting tabs 69 with bores for fixing the power transmission device 38 to the fuel cell system 2. The power transmission device 38 is temperature-controlled, and in particular cooled, by the coolant of the cooling system of the fuel cell system 2.The coolant is introduced into and discharged from the power transmission device 38 by means of two hydraulic coupling devices 70, in particular for cooling at least one sensor and / or one electrical resistor 74 and / or at least one other electrical and / or electronic component.

[0076] The power transmission device 38 also includes at least one sensor for detecting the electric current and / or voltage carried through the first busbar 49 and the second busbar 51. To detect the electric current and / or voltage at the first busbar 49 and the second busbar 51, the at least one sensor is connected to each busbar by a sensor cable 78. The electrical data relating to the current and / or voltage at the first busbar 49 and the second busbar 51 are transmitted outside the power transmission device via further sensor cables 78 and an electrical connector 65.In addition, the first busbar 49 and the second busbar 51 are electrically connected with two further sensor current cables 78 and these two further sensor current cables 78 are led through the electrical mating connector 65 to outside the power transmission device 48, so that with additional sensors, in particular in a control and / or regulation unit of the motor vehicle, for example the voltage difference between the first busbar 49 and the second busbar 51 can be detected directly by a voltage sensor not shown.

[0077] The current transmission device 38 also incorporates an electrical resistor 74 for handling a large electric current with a high electrical resistance, and a resistance current switch, for example formed by an electrical relay or, among other things, by two power transistors, is also incorporated. In the event of a motor vehicle accident, it is necessary to immediately disconnect the electric current generated by the fuel cell stack 3.For this reason, control current lines (not shown) are routed through the electrical mating connector 65 for low voltage on the device housing 39, and in the event of an accident, these control current lines are supplied with a corresponding control signal as control current by a central control and / or regulation unit of the motor vehicle, so that the electrical current is switched immediately by the relay, for example in a period of less than one second, and is short-circuited by the electrical resistor 74, so that in a short time no electrical current and no electrical voltage is present at the fuel cell stack 3.In addition, the vehicle's control and / or regulation unit naturally shuts down the fuel cell stack 3 by switching off the fuel supply system 29 and the oxidizer supply system 26. However, this shutdown requires some time until the fuel in the fuel cell stack 3 is consumed. The relay in the power transmission device 38 allows the electrical current and voltage in the fuel cell stack 3 to be switched off quickly. A current switch for deactivating and activating the transmission of the electrical current generated by the fuel cell stack to the mating connector 75, and thus to the main consumer, is switched simultaneously with the resistance current switch, so that the electrically conductive connection between the mating connector 75 and the fuel cell stack 3 is closed.the line from the fuel cell stack 3 to the power transmission device 38 is interrupted and therefore there is immediately no electrical voltage at the mating connector 75.

[0078] The electrical mating connector 65 comprises at least 6 electrical contact elements (not shown) in particular for transmitting data from the sensor in the transmission device 38, for transmitting the voltage difference between the first busbar 49 and the second busbar 51 directly to the outside, and for transmitting a control current for the relay for the electrical resistor 74 from the outside to the relay in the power transmission device 38 and to the power switch. An electrical connector with a power cable (not shown) is inserted into the electrical mating connector 65.

[0079] The electrical fuse 52 for the electrical unit of the fuel cell system 2 is integrated into the power transmission device 38. Due to the fluid-tight design of the device housing 39 with respect to the environment, the electrical fuse 52 is advantageously protected from mechanical, pneumatic, and hydraulic environmental influences. An electrical mating connector 66 serves to supply and conduct electrical current to the electrical unit. The two electrical mating contact elements (not shown) in the electrical mating connector 66 are each electrically connected to a power cable 64 ( Fig. 5 and Fig. 6) The two power cables 64 are inserted into a sub-housing 71 for the electrical fuse 52 ( Fig. 6) For this purpose, the following are required in accordance with the description in Fig. Six upwardly open sub-housings 71 have two openings for the passage of a power cable 64 each. The sub-housing 71 is screwed to the bottom wall 40 of the device housing 39 by means of fixing elements 43 in the form of screws 44, i.e., detachably connected. A fuse conductor 62 is arranged as a fuse busbar 63 within the interior enclosed by the sub-housing 71. Bolts are formed on the fuse conductor 62 as the fuse busbar 63, and a power cable 64 is mechanically and electrically connected to the bolt, and thus also to the fuse busbar 63, by means of a cable lug and a nut. The electrical fuse 52 is electrically and mechanically contacted at one end region of the electrical fuse 52 by means of two electrical fuse contact elements 73. As already described, one fuse contact element 73 is connected to the fuse busbar 63 by means of a bolt, a contact lug, and a nut.A second electrical safety contact element 73 is electrically and mechanically connected to the power cable 64 by means of a bolt, a cable lug, and a nut, as already described. The end of the side walls of the sub-housing 71 has no or only a small gap, for example less than 5 mm, 3 mm, or 1 mm, to the underside of the main cover wall 42 of the device housing 39. The distance between the end of the side wall of the sub-housing 71 facing the main cover wall 42 and the underside of the main cover wall 42 is essentially constant, in particular with a deviation of less than 30%, 20%, or 10%. This advantageously prevents objects, or only very small objects, from passing from a partial interior space enclosed by the sub-housing 71 into the remaining interior space bounded by the device housing 39 outside the partial interior space of the sub-housing 71.

[0080] The safety opening 47 ( Fig. 3) on the main wall 42 of the device housing 39 is a safety cover 53 ( Fig. 4) sealed fluid-tight with an extension 54 ( Fig. 2) The extension 54 is formed integrally with the locking cover 53 made of plastic and has the shape of a bracket 55. The locking cover 53 with the extension 54 is manufactured by injection molding. The bracket 55 has an opening 56. When an electrical connector (not shown) with a power cable is arranged in the mating electrical connector 65, the electrical connector and / or the cable is arranged within the opening 56 of the extension 54 of the locking cover 53. A positioning element 57 is formed as a positioning stud 58 on the underside of the locking cover 53, and a positioning opening 59 is also formed as a further positioning element 57 on the locking cover 53. Fig. 4) A counter-positioning element 60, designed as a counter-positioning stud 61, is formed on the bottom wall 40 of the device housing 39. When the fuse cover 53 is installed, the positioning stud 58 is arranged in a complementary counter-positioning bore 89 as a counter-positioning element 60 of the sub-housing 71. Furthermore, the counter-positioning stud 61 is arranged in the positioning opening 59. To replace the electrical fuse 52, the plastic fuse cover 53 must be removed from the main cover wall 42. For this purpose, the corresponding fixing elements 43, which are screws 44, must first be loosened so that the fuse cover 53 can be removed from the main cover wall 42.

[0081] For the removal of the fuse cover 53, it is additionally necessary that the connector (not shown) with the power cable has been disconnected from the electrical mating connector 65 so that the electrical connector (not shown) and the power cable do not block the removal movement of the fuse cover 53 with the extension 54 as the bracket 55. During the movement to remove the fuse cover 53, especially during the initial phase of the movement, for example with a movement length of less than 10 cm, 5 cm or 3 cm, essentially only a translational movement between the fuse cover 53 and the main deck wall 42 is possible, so that during this translational movement the fuse cover 53 is aligned essentially parallel to the main deck wall 42 and / or the distance between the main deck wall 42 and the fuse cover 53 is essentially identical.This ensures that, due to the blockage of the movement for removing the fuse cover 53, the fuse cover 53 cannot be removed by a pivoting or rotating movement when a power cable connector is inserted into the mating electrical connector 65. Pulling or removing the electrical connector from the mating electrical connector 65 automatically and forcibly shuts down the fuel cell system 2, including the control and / or regulation unit. Therefore, replacing the electrical fuse 52 is only possible when the fuel cell system 2 is switched off.Within the interior space enclosed by the sub-housing 71, even accidentally inserted parts, such as a screw 44, cannot cause a short circuit because, on the one hand, the fuel cell system 2 is switched off and, on the other hand, within the interior space limited by the sub-housing 71, only the electrical current of a power cable 64 with the fuse busbar 63 is carried without an electrical potential difference.

[0082] The first busbar 49 and the second busbar 51, with a width 87 and a thickness 88, are electrically and mechanically connected to a sensor power cable 78 each ( Fig. 5 and Fig. 7) For this purpose, an electrical contact element 79 is designed as an electrical contact socket 80 on a busbar 49, 51. A contact plug 82, designed as a flat contact plug 83, is attached to the contact socket 80 by means of a form-fit and / or force-fit connection by means of a sliding and insertion mechanism. The contact plug 82 thus forms a mating contact element 81 for the contact element 79 on the busbar 49, 51, and the contact element 79 and the mating contact element 81 are geometrically complementary for a form-fit and / or force-fit connection between the contact element 79 and the mating contact element 81. The in Fig. The contact nozzle 80 shown in Figure 7, as the contact element 79, is formed as a single unit with the busbar 49. The contact element 79 is formed as a single unit with the busbar 49. Fig. The busbar 49, 51 shown in section 7 consists of only one layer 84 and is manufactured by means of stamping and forming.

[0083] In Fig. 8 and Fig. Figure 9 shows a second embodiment of a busbar 49, 51. The busbar 49, 51 shown in the second embodiment is not installed in the power transmission device 38 described above. The busbar 49, 51 is formed from five layers 84. Fig. In Figure 8, layers 84 are shown in an exploded view, and on two layers 84, the contact element 79 is formed as the contact nozzle 80. In the Fig. In the busbar 49, 51 shown in Figure 9, the five layers 84 are stacked in alignment and connected to each other by positive locking, force locking, and / or material locking, for example, by gluing or resistance welding. The two contact elements 79 are also stacked in alignment on two layers 84, so that with a thickness of 0.6 mm for each contact stud 80 on each layer 84, the contact stud 80, consisting of the two contact studs 80, has a total thickness 76 of 1.2 mm. The entire contact stud 80, with a width 87, is thus formed as a single component of the layers 84 by two extensions on two layers 84. For the manufacture of the busbar 49, 51 according to the second embodiment in Figure 9, the following applies: Fig. 8 and Fig. 9. Further variants or examples are also possible. For example, the busbar 49, 51 has several layers 84, and the contact element 79 is formed as the contact stud 80 on only one layer 84. If the thickness of a contact stud 80 is too large due to the requirements of a contact plug 82 as a flat contact plug 83, the thickness of the contact stud 80 can be reduced after punching by post-processing, for example embossing and / or milling.

[0084] In the Fig. 10 and Fig. Figure 11 shows a first embodiment of the contact nozzle 80. The contact nozzle 80 has a conically tapered tapered section 85 with a length 77 at a front end region, followed by a cuboid main section 86 with a substantially constant width 72 and a substantially constant thickness 76. In the tapered section 85, the thickness 76 and the width 72 decrease towards the front end of the contact nozzle at a constant slope. The thickness 76 is, for example, 1 mm or 1.2 mm. The angle α is the angle α of the taper in the top view or longitudinal section. Fig. 10 is 45°. The angle β is the angle β of the taper in the side view or the further longitudinal section in Fig. 11 is 15°. The contact nozzle is perpendicular to the plane of the drawing in a cross-section not shown. Fig. 10 and Fig. 11 especially in the main section 86, which is rectangular in shape.

[0085] In the Fig. 12 and Fig. Figure 13 shows a second embodiment of the contact nozzle 80. The following discussion focuses primarily on the differences compared to the first embodiment. Fig. 10 and Fig. 11 described. The tapering section 85 is shown in longitudinal section according to Fig. 12 is formed with a curved surface with a constant radius of curvature. The tapered section 85 is shown in the further longitudinal section according to Fig. 13 with a curved surface with a different radius of curvature.

[0086] Overall, the power transmission device 38, the fuel cell unit 1, and the fuel cell system 2 according to the invention offer significant advantages. The contact elements 79 on the busbar 49, 51 are formed integrally with the busbar 49, 51, so that the contact elements 79 can be manufactured at low cost during the production of the busbar 49, 51 by stamping a blank. Busbars 49, 51, consisting of several layers 84 with a thickness 88 of more than 1.2 mm, utilize a smaller number of layers 84 with a contact element 79 than the busbar 49, 51 itself to form the contact element 79 (contact socket 80), so that the number of layers 84 for forming a contact element 79 is smaller than the number of layers 84 for forming the busbar 49, 51. The mating contact elements 81 are commercially available flat contact connectors 83 ( Fig. 14) designed so that they are inexpensive. Commercially available flat contact connectors 83 generally require contact bosses 80 with a thickness 76 of a maximum of 1.2 mm. The geometry of the contact bosses 80 is designed to be such that and / or complementary to the flat contact connectors 83, so that the flat contact connectors 83 can be reliably attached to the contact bosses 80 by means of a form-fit and / or force-fit connection by manually sliding them onto the contact bosses 80. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2015 117 333 B4

[0006]

Claims

[1] Power transmission device (38) for a fuel cell unit (1) or a fuel cell system (2), comprising - a device housing (39), - at least two conductors (48, 50) for conducting the electric current generated by a fuel cell stack (3), - at least one contact element (79) arranged on each current conductor (48, 50) for mechanical and electrical contact with each counter-contact element (81), - at least one counter-contact element (81) and one counter-contact element (81) is mechanically and electrically connected to one contact element (79) each, - at least one sensor cable (78) and one sensor cable (78) each with a counter-contact element (81) is mechanically and electrically connected, - at least one sensor for detecting the voltage and / or current of the electric current conducted through the at least two current conductors (48, 50) of the electric current generated by the fuel cell stack (3), characterized by , that at least one contact element (79) is formed in one piece with each of the current conductors (48, 50). [2] Power transmission device according to claim 1, characterized by , that at least one conductor (48, 50) is designed as a busbar (49, 51). [3] Power transmission device according to claim 2, characterized by , that the width (87) of the busbar (49, 51) is significantly larger than the thickness (76) of the busbar (49, 51). [4] Power transmission device according to one or more of the preceding claims, characterized by , that at least one busbar (49, 51) is formed from several layers (84). [5] Power transmission device according to claim 4, characterized by, that the layers (84) of each busbar (49, 51) are connected to each other by material bonding and / or force bonding and / or form bonding. [6] Power transmission device according to claim 4 or 5, characterized by , that the layers (84) of each busbar (49, 51) are connected to each other by a welded joint, in particular a resistance welded joint. [7] Power transmission device according to one or more of claims 4 to 6, characterized by , that the at least one contact element (79) is formed by a projection on the at least one layer (84) of the busbar (49, 51). [8] Power transmission device according to one or more of claims 4 to 7, characterized by , that the number of layers (84) from which each busbar (49, 51) is formed is greater than or identical to the number of layers (84) from which each contact element (79) of each busbar (49, 51) is formed. [9] Power transmission device according to one or more of claims 4 to 8, characterized by , that the thickness (76) of each contact element on each busbar (49, 51) is smaller or identical to the thickness (88) of each busbar (49, 51) with this contact element (79). [10] Power transmission device according to one or more of the preceding claims, characterized by , that at least one contact element (79) is designed as a contact nozzle (80) that is essentially cuboid or band-shaped. [11] Power transmission device according to claim 10, characterized by , that the width (72) of the contact nozzle (80) is significantly larger than the thickness (76) of the contact nozzle (80). [12] Power transmission device according to one or more of the preceding claims, characterized by, that each contact element (79) of each layer (84) comprises a tapered section (85) with a decreasing thickness (76) and / or width (72) and a main section (86) with a substantially constant thickness (76) and / or width (72). [13] Power transmission device according to one or more of the preceding claims, characterized by , that at least one mating contact element (81) is designed as a contact plug (81), in particular a flat contact plug (82). [14] Fuel cell unit (1) for electrochemical generation of electrical energy, comprising - stacked fuel cells (4) and the stacked fuel cells (4) form a fuel cell stack (3), - a power transmission device (38), characterized by that the power transmission device (38) is designed according to one or more of the preceding claims. [15] Fuel cell system (2) for converting chemical energy into electrical energy, comprising - at least one fuel cell unit (1) with stacked fuel cells (4) and the stacked fuel cells (4) forming a fuel cell stack (3), - at least one oxidizing agent supply system (26) for oxidizing agents, - at least one fuel supply system (29), - at least one cooling system, - a power transmission device (38), characterized by , that the power transmission device (38) is designed according to one or more of claims 1 to 13.

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