Current transmission device for a fuel cell system

Abstract

The invention relates to a current transmission device (38) for a fuel cell unit (1) or a fuel cell system (2), comprising a device housing (39) with at least one removable cover (42, 53, 76, 77) for opening the device housing (39), at least two current conductors (48, 50) for conducting the electrical current generated by a fuel cell stack (3), and a current switch for activating and deactivating the transmission of the electrical current generated by the fuel cell stack (3) to a main load, said current transmission device (38) comprising a device (72) for detecting the removal of the at least one removable cover (42, 53, 76, 77) from the rest of the device housing (39).

Description

[0001] Description

[0002] title

[0003] Current transmission device for a

[0004] 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.

[0005] State of the art

[0006] Fuel cell units, as galvanic cells, convert continuously supplied fuel and oxidant into electrical energy and water through 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 power grid connection or in motor vehicles, in rail transport, aviation, aerospace, and shipping. In fuel cell units, a large number of fuel cells are arranged in a fuel cell stack.

[0007] Within each fuel cell, there is a gas space for the oxidant, i.e., a flow space for the passage of oxidant, such as ambient air with oxygen. The gas space for the oxidant is formed by channels on the bipolar plate and by a gas diffusion layer for a cathode. The channels are thus formed by a corresponding channel structure of a bipolar plate, and the oxidant, namely oxygen, passes through the gas diffusion layer to reach the cathodes of the fuel cells. Similarly, a gas space for fuel is formed at an anode. Fuel cell systems are made up of various components, such as a fuel supply system, an oxidant supply system, and the fuel cell stack. The fuel cells contain a proton exchange membrane for conducting protons.In the fuel cell system, the gas delivery device of the oxidant supply system is driven by an electric unit, such as an electric motor. The electrical current generated by the fuel cell stack is transmitted through a power transmission device to a main consumer, for example, an electric drive system of a motor vehicle. Within the power transmission device are electrical or electronic components that require maintenance or replacement in the event of a defect. For this purpose, a removable cover is formed on a device housing of the power transmission device.When carrying out maintenance work on the electrical or electronic components, there is therefore a disadvantageous risk after dismantling the cover that a short circuit may be triggered by electrically conductive objects accidentally placed in the power transmission device or that there are health risks if the person carrying out the work comes into contact, for example, with a busbar with an electrical potential.

[0008] DE 10 2015 117 333 B4 discloses a fuel cell system, comprising: a fuel cell configured to perform an external power supply; a coolant circulation line through which a coolant cooling the fuel cell circulates; a radiator mounted on the coolant circulation line; a water pump configured to circulate a coolant in the coolant circulation line; a flow splitting valve configured to control a flow rate of the coolant flowing through the radiator; a fan configured to supply air to the radiator; and a controller.

[0009] Disclosure of the invention

[0010] Advantages of the invention A power transmission device according to the invention for a fuel cell unit or a fuel cell system, comprising a device housing with at least one removable cover for opening the device housing, at least two current conductors for conducting the electrical current generated by a fuel cell stack, preferably a current switch for deactivating and activating the forwarding of the electrical current generated by the fuel cell stack to a main consumer, wherein the power transmission device comprises a device for detecting disassembly of the at least one removable cover from the rest of the device housing. Advantageously, this allows the disassembly of the at least one removable cover to be detected, and security measures can subsequently be initiated.The device for detecting the disassembly of the at least one removable cover detects the actual disassembly of the at least one removable cover and / or an impending disassembly of the at least one removable cover for design reasons, for example, the removal of a plug connector from a mating plug connector on the power transmission device is an indication or feature of the impending later disassembly of the at least one removable cover.

[0011] In a supplementary embodiment, an electrical fuse for an electrical unit of the fuel cell unit or fuel cell system is arranged within the device housing of the power transmission device. The electrical fuse is thus advantageously protected from mechanical damage due to its arrangement within the device housing. The electrical fuse is covered by a fuse cover, and the disassembly of this fuse cover when replacing the electrical fuse can advantageously be detected by the device for detecting the disassembly of the fuse cover.

[0012] In a further embodiment, the device housing comprises a main wall, in particular a cover main wall, and a securing cover is fastened to and / or on the main wall.

[0013] In an additional variant, the at least one removable cover is the main wall of the device housing and / or the fuse cover and / or an additional fuse cover. Preferably, an electrical mating connector is formed on the outside of the power transmission device for electrical connection to an electrical connector with a power cable. The electrical mating connector serves for electrical connection to the electrical connector, preferably for low voltage and / or data.

[0014] In a supplementary embodiment, the device for detecting disassembly of the at least one removable cover is formed by the remaining device housing and / or a control unit and / or the electrical mating connector and / or a sensor, in particular a contact sensor. Preferably, the remaining device housing comprises those components or that part of the device housing whose disassembly cannot be detected.

[0015] In a further embodiment, the power transmission device is designed such that the at least one cover, in particular the main wall and / or the fuse cover, can only be removed from the device housing, in particular the main wall, if no electrical connector, preferably with a power cable, is plugged into the electrical mating connector.

[0016] The current transmission device expediently comprises a resistance current switch for conducting the electrical current generated by the fuel cell stack through an electrical resistor as an electrical short circuit of the fuel cell stack.

[0017] In an additional variant, the power transmission device comprises a control unit for switching the current switch and / or resistance current switch depending on a control signal from the device for detecting the disassembly of the at least one removable cover and / or depending on an external control signal, for example, a central control and / or regulating unit of a motor vehicle. The control unit preferably functions for further functions, for example, for forwarding data regarding the voltage and / or current of the fuel cell stack to an external control and / or regulating unit, in particular a central control and / or regulating unit of a motor vehicle.

[0018] In particular, the control unit can be operated, in particular exclusively, with electrical energy from the fuel cell stack. The control unit can thus continue to be operated with electrical energy from the fuel cell stack even after the electrical connector has been removed from the electrical mating connector, in particular for low voltage, without electrical energy from an external control and / or regulating unit.

[0019] In a further variant, the control unit can be operated indirectly using electrical energy from the fuel cell stack, using a galvanic isolation device integrated into the power transmission device between the fuel cell stack and the control unit. In particular, the galvanic isolation device is structurally integrated into the control unit, so that the control unit is galvanically isolated from the fuel cell stack. The galvanic isolation is necessary for safety reasons.

[0020] In an additional embodiment, the control unit, in particular always, switches the power switch upon disassembly of the at least one removable cover from the remaining device housing based on the control signal of the device for detecting disassembly of the at least one removable cover, so that the forwarding of the electrical current generated by the fuel cell stack to the main consumer is interrupted.The device for detecting disassembly of the at least one removable cover is designed, for example, as the electrical mating connector as an indirect device due to the mechanical and electrical properties for this functionality, because an electrical control signal is constantly passed from the external central control and / or regulating unit of the motor vehicle into the control unit through the electrical mating connector and when the electrical connector is mechanically removed from the electrical mating connector, this control signal is no longer passed to the control unit and this is viewed or interpreted by the control unit as disassembly of the at least one removable cover.After the removal of at least one cover, electrical energy is no longer conducted to the main consumer and is also no longer conducted through the electrically conductive components of the power transmission device that are accessible after the removal of at least one cover.

[0021] In a further variant, the control unit, in particular always, switches the resistance current switch upon disassembly of the at least one removable cover from the remaining device housing based on the control signal of the device for detecting disassembly of the at least one removable cover, such that conduction of the electrical current generated by the fuel cell stack through the electrical resistance can be implemented as an electrical short circuit. Due to the electrical short circuit, the fuel cell stack and / or the accessible electrically conductive components of the power transmission device are de-energized and de-energized within a few seconds, for example, less than 5 seconds, after disassembly of the at least one cover.

[0022] 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 described in this patent application.

[0023] 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 and the stacked fuel cells forming a fuel cell stack, at least one oxidant supply system for oxidants, 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 described in this patent application.

[0024] In a further embodiment, at least one fixing element, in particular a screw, for fixing the main wall, in particular the cover main wall, of the housing of the power transmission device is covered by the fuse cover, so that this at least one fixing element for fixing the main wall can only be removed after the fuse cover has been removed and thus the main wall, in particular the cover main wall, of the housing of the power transmission device can only be removed after the fuse cover has been removed.

[0025] In a further variant, the power transmission device comprises at least one sensor for detecting the voltage and / or the current of the electric current conducted through the at least two current conductors of the electric current generated by the fuel cell stack.

[0026] In a further embodiment, the electrical fuse is covered by the fuse cover.

[0027] In a supplementary variant, the electrical fuse is accessible from the outside for replacement after removing or disassembling the fuse cover from the device housing, particularly when the power transmission device is arranged and / or attached in and / or to a fuel cell system. The electrical fuse can thus be easily replaced simply by disassembling or removing the fuse cover.

[0028] In a further 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 fuse cover.

[0029] Preferably, the width of the main wall is greater than 1, 2, 1-5, 2 or 3 times the width of the fuse cover.

[0030] In a supplementary embodiment, the main wall has a fuse opening, and the fuse opening is covered, in particular completely, by the fuse cover. The device housing of the power transmission device is thus completely closed and fluid-tight with respect to the environment when the fuse cover is installed. As a result, no substances from the outside can penetrate into the interior space defined by the device housing. In an additional variant, a seal is arranged between the main wall and the fuse cover to seal the fuse opening with respect to the environment; in particular, the seal is formed completely circumferentially around the fuse opening.Preferably, the seal is arranged on a rear side of the securing cover and is connected to the securing cover, in particular in a materially bonded and / or positively bonded and / or force-locked manner, so that during assembly and disassembly of the securing cover from the main deck wall or the main wall, the seal is always arranged on the securing cover.

[0031] The power transmission device is expediently designed such that the fuse cover can only be removed from the device housing, in particular the main wall, if no electrical connector, preferably with a power cable, is plugged into the electrical mating connector.

[0032] In an additional embodiment, an extension with an opening is formed on the fuse cover, in particular formed in one piece with the fuse cover, and in the assembled state of the fuse 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 extension, so that the disassembly of the fuse cover from the electrical connector and / or the power cable in the opening is mechanically blocked by the electrical connector and / or power cable.

[0033] In another variant, the extension is designed as a bracket.

[0034] 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 power transmission device, in particular the device housing of the power transmission device, and one positioning element is arranged in each counter-positioning element, so that the movement, in particular the initial phase of the movement, for dismantling the fuse cover from the power transmission device is essentially only a translational movement of the fuse cover for increasing the distance between the fuse cover and the main wall, in particular during contact between one positioning element and one counter-positioning element.Essentially only a translational movement preferably means that the securing cover is aligned essentially parallel to the main wall or deck main wall, in particular with a deviation of less than 30°, 20° or 10°, and / or the distance between the main wall or deck main wall and the securing cover is essentially identical, in particular with a deviation of less than 30%, 20% or 10%. The one positioning element and the one counter-positioning element thus form a sliding bearing and / or a forced guide for the translational movement between the securing cover and the main wall. In a supplementary variant, the movement path of the initial phase of the relative movement between the securing cover and the main wall is less than 20 cm, 10 cm, 5 cm, 3 cm or 1 cm.

[0035] In a further variant, the power transmission device can be cooled with the cooling system of the fuel cell system.

[0036] 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 tempering, in particular cooling, the power transmission device.

[0037] In a supplementary embodiment, the device housing comprises the main wall, in particular the cover main wall, and / or at least one side wall and / or a bottom wall and / or a sub-housing.

[0038] 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 produced by injection molding.

[0039] In an additional embodiment, the power transmission device comprises at least one pressure compensation device, in particular a membrane or a compensating piston, for changing the volume of the interior space delimited by the device housing, preferably for changing the volume by at least 0.5%, 1%, 3%, 5% or 10%.

[0040] In particular, the power transmission device comprises a sub-housing for dividing the interior of the power transmission device into a partial interior with the fuse and the remaining interior outside the partial interior, and the sub-housing at least partially delimits the partial interior.

[0041] The interior of the power transmission device, which is delimited by the device housing, is expediently sealed fluid-tight with respect to the environment.

[0042] In a further embodiment, the components of the fuel cell system, for example the fuel cell unit and / or the oxidant 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 comprise a pressure vessel for the fuel and preferably a connection for a fuel line.

[0043] In a further embodiment, the fuel supply system comprises a fuel line and / or a recirculation fuel line and / or a recirculation fuel conveyor and / or a water separator and / or an injector for fuel and / or a pressure reducer for fuel and / or a heat exchanger for fuel.

[0044] Preferably, the support device of the module is designed as a frame and / or a framework and / or a grid and / or a plate.

[0045] In a further embodiment, the area of ​​the main wall is greater than 1, 2 times, 1-5 times, 2 times or 3 times the area of ​​the fuse cover.

[0046] In a further 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 oxidant.

[0047] In a supplementary embodiment, the at least one gas conveying device is designed as a blower and / or compressor and / or condenser.

[0048] 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.

[0049] Preferably, the fuel is hydrogen, hydrogen-rich gas, reformate gas or natural gas.

[0050] Advantageously, the fuel cells and / or components of the fuel cells are essentially flat and / or disc-shaped.

[0051] In a further variant, the fuel cell unit comprises a housing and / or a connecting plate. The fuel cell stack is enclosed by the housing and / or the connecting plate. The fuel cell unit preferably comprises the fuel cell stack and preferably the housing.

[0052] In a complementary variant, the oxidizing agent is air with oxygen or pure oxygen.

[0053] Preferably, the fuel cell unit is a PEM fuel cell unit with PEM fuel cells or an SOFC fuel cell unit with SOFC fuel cells or an alkaline fuel cell (AFC).

[0054] Short description of the drawings

[0055] In the following, exemplary embodiments of the invention are described in more detail with reference to the accompanying drawings. Fig. 1 shows a highly simplified representation of a fuel cell system,

[0056] Fig. 2 is a perspective view of a power transmission device with a fuse cover for a fuse,

[0057] Fig. 3 is a perspective view of the power transmission device according to Fig. 2 without the fuse cover (disassembled) for the fuse,

[0058] Fig. 4 is a perspective view of the fuse cover for securing the power transmission device according to Fig. 2,

[0059] Fig. 5 is a perspective view of the power transmission device according to Fig. 2 without the main wall (disassembled),

[0060] Fig. 6 is a perspective view from above of a sub-housing for the fuse with fuse,

[0061] Fig. 7 is a perspective view of a busbar in a first embodiment of the power transmission device according to Fig. 2,

[0062] Fig. 8 is a perspective view of layers of a busbar as an exploded view in a second embodiment,

[0063] Fig. 9 a busbar in a second embodiment of several stacked layers,

[0064] Fig. 10 is a perspective view from below of the sub-housing for the fuse with a control unit,

[0065] Fig. 11 a longitudinal section of the sub-housing for the fuse, a fuse cover and an additional cover without control unit.

[0066] Fig. 1 shows a fuel cell unit 1 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 delimits an interior space 14. The connection plate 15 also functions as a housing 13 and is fixed to the remaining housing 13 by fixing elements 16, in particular screws 17. In the fuel cell stack 2, fuel cells 4 are stacked as PEM fuel cells 5 and arranged in alignment. Due to the large number of stacked fuel cells 4, approximately 300 to 400, not all of them are shown in Fig. 1 for the sake of simplicity. The principle of fuel cells 4 is that electrical energy or electrical current is generated by means of an electrochemical reaction.Hydrogen H2 is fed to an anode (not shown) as a gaseous recirculation fuel, and the anode forms the negative pole. A gaseous oxidant, namely air with oxygen, is fed to a cathode (not shown), i.e. the oxygen in the air provides the necessary gaseous oxidant. Reduction (electron absorption) takes place at the cathode. Oxidation (electron release) takes place at the anode. The fuel cells 4 also comprise an ion exchange membrane as a proton exchange membrane (Proton Exchange Membrane, PEM), which is arranged between the anode and the cathode. On the two sides of the PEM, each facing the gas spaces, are the electrodes known as the anode and cathode (not shown). A unit comprising the PEM, anode, and cathode is referred to as a Membrane Electrode Assembly (MEA) (not shown).A gas diffusion layer (GDL) is positioned on the anode and cathode. A bipolar plate (not shown) is positioned on top of the GDL. The electrically conductive bipolar plate serves as a current collector, for water drainage, and for conducting the reaction gases.

[0067] In the fuel cell unit 1, the fuel cells 4 are arranged between two clamping elements 18 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 apply a compressive force to the fuel cells 4, i.e. the upper clamping plate 20 rests with a compressive force on the uppermost fuel cell 4 and the lower clamping plate 21 rests with a compressive force on the lowermost fuel cell 4. The fuel cell stack 3 is thus clamped in order to ensure the tightness for the fuel, the oxidizing agent and the coolant, in particular due to elastic seals, and also to keep the electrical contact resistance within the fuel cell stack 3 as low as possible.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 firmly connected to the clamping plates 19.

[0068] An opening for introducing recirculation fuel into the recirculation fuel channels is formed in the connecting plate 15 and in the lower clamping plate 21. Furthermore, an opening for discharging recirculation fuel from the recirculation fuel channels is formed in the connecting plate 15 and in the lower clamping plate 21. An opening 35 for introducing oxidizing agent and an opening 36 for discharging oxidizing agent are formed in the connecting plate 15 and the lower clamping plate 21 as the clamping element 18, as well as openings (not shown) for introducing coolant and discharging coolant. Thus, a total of six openings are formed in the connecting plate 15 and the lower clamping plate 21 (only partially shown in Fig. 1).

[0069] 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 comprises a gas delivery device 27, for example a blower, a compressor, a turbocompressor driven by an electric motor, i.e., an electric drive motor as an electrical unit, and / or a turbine (not shown), and oxidant lines 28 as the oxidant supply line 24 and the oxidant discharge line 25, as well as a humidifier 37.

[0070] In addition to the fuel cell unit 1, the fuel cell system 2 also comprises 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 feed device 33, an electric motor (not shown) for driving the recirculation fuel feed 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 drain valve as a purge valve (not shown) for discharging recirculation 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 tank 30 at a high pressure of, for example, 400 bar is supplied to the fuel cells 4 through the fuel line 31. After the fuel has been passed through the fuel cells 4, the hydrogen is not completely consumed.so that this hydrogen derived from the fuel cells 4 is fed back to the fuel cells 4 in a circuit via the recirculation fuel line 32. The recirculation fuel conveying device 33 is used to convey the recirculation fuel through the recirculation fuel line 32. After the fuel passes through the fuel cells 4, the moisture content of the fuel increases, so that to prevent an excessive water or moisture content in the recirculation fuel, the fuel supply system 29 includes the water separator 34. The water separated in the water separator 34 is collected in the water tank (not shown) and discharged into the environment through the drain valve (not shown). Excess recirculation fuel is discharged into the environment through the purge valve (not shown).

[0071] In addition to the fuel cell unit 1, the fuel cell system 2 also comprises a cooling system (not shown) for controlling the temperature of the fuel cell stack 3, i.e., for cooling the fuel cell stack 3. The cooling system for controlling the temperature of the fuel cell stack 3 comprises coolant lines as process fluid lines, a heat exchanger, and a pump driven by an electric motor for circulating the coolant. The coolant is conducted through coolant channels in the bipolar plates of the fuel cells 4, and the heat is dissipated to the environment at the heat exchanger. In addition to the fuel cell unit 1, the fuel cell system 2 also comprises the oxidant supply system 26, the fuel supply system 29, and the cooling system (not shown) as a coolant supply system.

[0072] The proton exchange membranes of the fuel cells 4 must be sufficiently humidified 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 into the oxidant in the oxidant supply line 24, 28. For this purpose, corresponding membranes (not shown) are configured in the humidifier 37 to transfer or conduct the moisture and / or water from the oxidant exhaust gas to the oxidant introduced into the fuel cell stack 3.

[0073] The essential components of the fuel cell system 2 are arranged in a compact, space-saving module, preferably without a pressure vessel 30. In Fig. 1, the fuel cell system 2 is shown only to illustrate its functionality, 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 oxidant supply system 26, the fuel supply system 29, the cooling system, and a power transmission device 38.

[0074] The electrical current generated by the fuel cell stack 3 is transmitted via power lines and through the power transmission device 38 (Figs. 2 to 11) to a main consumer (not shown), in particular an electric drive system of a motor vehicle. The power transmission device 38 functions to transmit 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 transmitted from the fuel cell stack 3 to the main consumer (not shown).

[0075] 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 main cover wall 42 as a main wall 42. In the main cover wall 42, there is a fuse opening 47 (Fig. 3) for an electrical fuse 52 (Figs. 3, 6, and 11) built into and integrated in the power transmission device 38 for an electrical unit of the fuel cell system 2, in particular an electric drive motor for the gas delivery device 27. The bottom wall 40, the side wall 41, and the main cover wall 42 are detachably connected to one another with 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.Connecting tabs 45 are formed as extensions on the bottom wall 40, and connecting tabs 46 are formed as extensions of the side wall 41 on 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 with the fixing elements 43 as screws 44, so that the bottom wall 40 is fastened to the side walls 41. In addition, the main deck wall 42 is fixed to connecting tabs of the side walls 41 with the fixing elements 43 (Figs. 2 and 3). The bottom wall 40, the side walls 41, and the main deck wall 42 are each manufactured as a single piece from plastic by injection molding. Between the bottom wall 40, the side wall 41 and the main cover wall 42, seals (not shown) are arranged which are formed completely around the circumference, so that the interior space delimited by the device housing 39 is sealed fluid-tight with respect to the environment.

[0076] An opening (not shown) is formed in the bottom wall 40, and through this opening, the two power lines (not shown) from the fuel cell stack 3 are introduced into the interior space defined by the device housing 39. These two power lines are sealed fluid-tight at the openings with respect to the environment. These two power lines are connected within the device housing 39 to a first power conductor 48 as a first power rail 49 and a second power conductor 50 as a second power rail 51. The two power rails 49, 51 serve to conduct the electrical current generated by the fuel cell stack 3 through the device housing 39 and are then led to a mating connector 75 on an outer side of a side wall 41 with power lines.Two correspondingly large electrical contact elements (not shown) are formed in the mating connector 75 for the main consumer. The interior space defined by the device housing 39 is fluid-tightly sealed from the environment. Due to temperature changes, pressure differences can arise in the interior space defined by the device housing 39, so that with two pressure equalization devices 67 as membranes 68, the volume of the interior of the power transmission device 38 can be changed for only a slight change in the pressure within the power transmission device 38 during fluctuating temperatures. Furthermore, two fastening tabs 69 with bores for fixing the power transmission device 38 to the fuel cell system 2 are formed on the device housing 39. The power transmission device 38 is temperature-controlled, in particular cooled, with the coolant of the cooling system of the fuel cell system 2.The coolant is introduced into the power transmission device 38 and discharged again through two hydraulic coupling devices 70, in particular for cooling at least one sensor and / or an electrical resistor 74 and / or at least one further electrical and / or electronic component.

[0077] At least one sensor for detecting the electrical current and / or voltage conducted through the first busbar 49 and the second busbar 51 is also arranged in the power transmission device 38. To detect the electrical current and / or voltage at the first busbar 49 and the second busbar 51, the at least one sensor is connected to the first busbar 49 and the second busbar 51 by a sensor power cable 78. The electrical data relating to the current and / or voltage at the first busbar 49 and the second busbar 51 are transmitted to the outside of the power transmission device 38 by additional sensor power cables 78 through an electrical mating connector 65.In addition, the first busbar 49 and the second busbar 51 are electrically connected to two additional sensor current cables 78, and these two additional sensor current cables 78 are routed through the electrical mating connector 65 to the outside of the power transmission device 48, so that with additional sensors, in particular in an external central control and / or regulating unit of the motor vehicle, for example, the voltage difference directly between the first busbar 49 and the second busbar 51 can be detected by an external voltage sensor (not shown). Also incorporated into the power transmission device 38 is the electrical resistor 74 for a large electrical current with a high electrical resistance, and a resistive 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 shut off the electrical 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. 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 regulating unit of the motor vehicle. Such that the electrical current is immediately switched by the relay, for example within a period of less than one second, and short-circuited by the electrical resistor 74, so that in a short time, no electrical current and no electrical voltage are applied to the fuel cell stack 3.The switching of the resistance current switch can also be carried out, preferably autonomously, by a control unit 86, optionally indirectly by the central control and / or regulating unit of the motor vehicle with a corresponding control signal as a control current to the control unit 86. In addition, the fuel cell stack 3 is naturally switched off by the control and / or regulating unit of the motor vehicle by switching off the fuel supply system 29 and the oxidant supply system 26. However, this switching off requires some time until the fuel in the fuel cell stack 3 is consumed, and with the relay in the power transmission device 38, the electrical current and the electrical voltage in the fuel cell stack 3 can be switched off in a short time.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 electrical mating connector 75 and the fuel cell stack 3 or the line from the fuel cell stack 3 into the current transmission device 38 is interrupted and thus immediately no electrical voltage is applied to the mating connector 75.The switching of the current switch is carried out analogously to the switching of the resistance current switch, since control current lines (not shown) are routed through the electrical mating connector 65 for low voltage on the device housing 39. In the event of an accident, these control current lines are supplied with a corresponding control signal as a control current from a central control and / or regulating unit of the motor vehicle, so that the current switch is switched. The switching of the current switch can also be carried out, preferably independently, by a control unit 86, optionally indirectly by the central control and / or regulating unit of the motor vehicle with a corresponding control signal as a control current to the control unit 86.

[0078] The electrical mating connector 65 comprises a total of several electrical contact elements (not shown), in particular for conducting the data from the sensor in the transmission device 38, for conducting the voltage difference between the first busbar 49 and the second busbar 51 directly to the outside and for conducting a control current and / or control signal for a control unit 86 built into the power transmission device from the outside, in particular from the central control and / or regulating unit of the motor vehicle, to the control unit 86 in the power transmission device 38. An electrical connector with a power cable with several strands (not shown) is plugged 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 can thus advantageously be protected from mechanical, pneumatic, and hydraulic environmental influences. An electrical mating connector 66 serves to supply and conduct electrical current for 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 (Figs. 5 and 6). The two power cables 64 are inserted into a sub-housing 71 for the electrical fuse 52 (Fig. 6). For this purpose, two openings for each power cable 64 are formed in the sub-housing 71, which is open at the top as shown in Fig. 6.The sub-housing 71 is screwed, i.e., detachably connected, to the bottom wall 40 of the device housing 39 by means of fixing elements 43 in the form of screws 44. A fuse current conductor 62 is arranged as a fuse busbar 63 within the interior space enclosed by the sub-housing 71. Bolts are formed on the fuse current 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 by two electrical fuse contact elements 73 at one end region of the electrical fuse 52. As already described, a fuse contact element 73 is connected to the fuse busbar 63 by means of a bolt, a contact lug, and a nut.A further, second electrical fuse contact element 73 is, as already described, electrically and mechanically connected to the power cable 64 by means of a bolt, a cable lug, and a nut. The end of the side walls of the sub-housing 71 has no or only a small distance, for example, less than 5 mm, 3 mm, or 1 mm, from 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 any objects, or only very small objects, from passing from a partial interior enclosed by the sub-housing 71 into the remaining interior space delimited by the device housing 39 outside the partial interior space of the sub-housing 71.

[0080] The securing opening 47 (Fig. 3) on the main wall 42 of the device housing 39 is closed in a fluid-tight manner by a securing cover 53 (Fig. 4) with an extension 54 (Fig. 2). The extension 54 is formed integrally with the securing cover 53 from plastic and has the shape of a bracket 55. The securing 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 electrical mating connector 65, the electrical connector and / or the cable is arranged within the opening 56 of the extension 54 of the securing cover 53. On the underside of the safety cover 53, a positioning element 57 is formed as a positioning socket 58 and furthermore a positioning opening 59 is formed as a further positioning element 57 on the safety cover 53 (Fig. 4).A counter-positioning element 60 is formed as a counter-positioning stud 61 on the bottom wall 40 of the device housing 39. When the fuse cover 53 is mounted, the positioning stud 58 is arranged in a complementarily formed counter-positioning bore 95 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. To do this, corresponding fixing elements 43, in the form of screws 44, must first be loosened so that the fuse cover 53 can be removed from the main cover wall 42.

[0081] For the disassembly of the fuse cover 53, it is additionally necessary that the plug connector (not shown) with the power cable has been removed from the electrical mating connector 65 so that the electrical plug connector (not shown) and the power cable do not block the disassembly movement of the fuse cover 53 with the extension 54 as the bracket 55. During the movement for disassembling the fuse cover 53, in particular during the initial phase of the movement, for example with a movement length of less than 10 cm, 5 cm or 3 cm, for disassembling the fuse cover 53, essentially only a translational movement can be carried out between the fuse cover 53 and the main deck wall 42, 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 blocking of the movement for disassembling the fuse cover 53, disassembly of the fuse cover 53 by means of a substantially pivoting or rotating movement is not possible when a connector with a power cable is plugged into the electrical mating connector 65. Pulling or removing the electrical connector from the electrical mating connector 65 automatically and forcibly causes a complete shutdown of the fuel cell system 2 with the control and / or regulating unit and / or with the control unit 86. The replacement of the electrical fuse 52 can therefore only be carried out when the fuel cell system 2 is shut down.Within the partial interior space enclosed by the sub-housing 71, even parts that have accidentally fallen in, for example a screw 44, cannot cause a short circuit because, on the one hand, the fuel cell system 2 is switched off and, in addition, within the partial interior space delimited by the sub-housing 71, only the electrical current of a power cable 64 is carried by the fuse busbar 63 without an electrical potential difference.

[0082] The first busbar 49 and the second busbar 51 are each electrically and mechanically connected to a sensor power cable 78 (Figs. 5 and 7). The busbar 49, 51 has a width 87 and a thickness 88. For this purpose, an electrical contact element 79 is formed on a busbar 49, 51 as an electrical contact socket 80. A contact plug 82, a flat contact plug 83, is positively and / or force-fitted to the contact socket 80 by sliding and inserting. 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 positive and / or non-positive connection between the contact element 79 and the mating contact element 81. The contact socket 80 shown in Fig. 7 as the contact element 79 is formed in one piece with the busbar 49. The contact element 79 shown in Fig.The busbar 49, 51 shown in Figure 7 consists of only one layer 84 and is manufactured by punching and forming.

[0083] 8 and 9 show a second exemplary embodiment of a busbar 49, 51. The busbar 49, 51 shown in the second exemplary embodiment is not installed in the power transmission device 38 described above. The busbar 49, 51 is formed from five layers 84. In Fig. 8, the layers 84 are shown in an exploded view, and the contact element 79 is formed as the contact socket 80 on two layers 84. In the busbar 49, 51 shown in Fig. 9, the five layers 84 are stacked in alignment and connected to one another in a form-fitting and / or force-fitting and / or material-fitting manner, for example by means of adhesive bonding or resistance welding. The two contact elements 79 are also stacked flush on top of each other on two layers 84, so that with a thickness of each contact socket 80 of 0.6 mm, the contact socket 80 made up of the two contact sockets 80 on each layer 84 has a total thickness of 1.2 mm.Further variants or examples are also possible for the production of the busbar 49, 51 according to the second embodiment in Fig. 8 and Fig. 9. For example, the busbar 49, 51 has several layers 84, and the contact element 79 is formed as the contact socket 80 on only one layer 84. If the thickness of a contact socket 80 is too large due to the requirements of a contact plug 82 as a flat contact plug 83, the thickness of the contact socket 80 can be reduced after punching by post-processing, for example, embossing and / or milling.

[0084] The sub-housing 71 for the fuse 52 comprises side walls and a bottom wall. Within the space enclosed by the side walls and the bottom wall, the electrical fuse 52 is arranged within the upwardly open sub-housing 71. A circuit board 89 of the control unit 86 is fastened to the bottom wall of the sub-housing 71 with fixing elements 43 as screws 44. Electronic components 92 and a galvanic isolating device 91 are fastened to the circuit board 89, among other things. Additionally, two contacts 90 are formed on the circuit board 89 of the control unit 86. The contacts 90 are formed as holes or slots in the circuit board 89 and are contacted by electrical contact rods. These electrical contact rods are electrically connected to the two power cables to the fuel cell stack 3. Conductor tracks on the circuit board 89 are not shown in Fig. 10.The two contacts 90 supply the control unit 86 with electrical energy from the high voltage of the fuel cell stack 3, i.e., it is operated exclusively with electrical energy from the fuel cell stack 3. The remaining control unit 86 is galvanically separated from the fuel cell stack 3 by the galvanic isolation device 91. The galvanic isolation device 91 comprises an inverter that converts the direct current of the fuel cell stack 3 into alternating current. This alternating current from the inverter is then transformed into alternating current with a lower voltage in a transformer with two coils (not shown). This alternating current from the transformer is then converted back into direct current by a rectifier for the operation of the control unit 86.Also provided on the circuit board 89 are a 2-pin electrical connector 93 and a 12-pin electrical connector 94 for low-voltage electrical current and signals. The contact elements in the connectors 93, 94 are connected to the electrical contact elements of the electrical mating connector 65 on the outside of the device housing 39 via mating connectors (not shown) in the connectors 93, 94. The two electrical contact elements of the 2-pin electrical connector 93 are connected to the two contacts 90 via corresponding conductor tracks on the circuit board 89, and thus also to the fuel cell stack 3.With a connector in the electrical mating connector 65, the voltage difference across the fuel cell stack 3 can be conducted through the 2-pin electrical connector 93 and through the electrical mating connector 65 to, for example, the central control and / or regulating unit of the motor vehicle outside the power transmission device 38 for detecting the voltage difference across the fuel cell stack 3. Through the 12-pin electrical connector 34, signals and / or data can be conducted from the power transmission device 38 through the electrical mating connector 65 to the central control and / or regulating unit of the motor vehicle and vice versa.

[0085] The electrical mating connector 65 forms a device 72 for detecting the disassembly of a cover 76. The cover 76 is formed, for example, by the main wall 42 and / or the fuse cover 53 and / or an additional fuse cover 77. The additional fuse cover 77 is arranged below the fuse cover 53 and must be removed after the fuse cover 53 has been disassembled to access the fuse 52. Three tabs 85 (Fig. 11) are formed on the additional fuse cover 77. The two tabs 85 formed on the top of the additional fuse cover 77 serve as a stop and / or support for the fuse cover 53. A further tab 85, shown on the right in Fig. 11, which rests on an outer side of a side wall of the sub-housing 71 in the assembled state, preferably prevents incorrect assembly of the additional fuse cover 77. Approximately 5 seconds are required for disassembly of the additional fuse cover 77.The disassembly of the fuse cover 53 is detected by the electrical mating connector 65 as the device 72 for detecting the disassembly of a cover 76, because the pulling or removal of an electrical connector from the electrical mating connector 65 is detected by the control unit 86, and subsequently the current switch is deactivated so that no more electrical current is conducted from the fuel cell stack 3 to the mating connector 75, and simultaneously the resistance current switch is activated so that the electrical current is conducted through the electrical resistor 74. The control unit 86 thus also forms a device 72 for detecting disassembly. However, it takes a few seconds until no electrical voltage is applied to the electrical fuse 52 and thus also to the fuse current conductor 62, so that this period of a few seconds is bridged with the additional fuse cover 77.This ensures that when the additional fuse cover 77 is dismantled, no electrical voltage is present after the fuse cover 53 has been dismantled, thus making the electrical fuse 52 and the fuse current conductor 62 accessible, and that no voltage is present anywhere else within the device housing 39. The pulling or removal of the electrical plug connector from the electrical mating connector 65 is detected by the control unit 86, for example, by the central control and / or regulating unit continuously passing a test current or test signal to the control unit 86 through the electrical mating connector 65 and the electrical plug 94. The interruption of this test current or test signal is detected by the control unit 86 as a negative control signal, and this is interpreted as information regarding the dismantling of a cover 76.

[0086] To disassemble the main wall 42, the fixing elements 43, such as the screws 44, must be loosened, and some securing elements 43 are covered by the securing cover 53, so that disassembly of the main wall 42 is structurally only possible after disassembly of the securing cover 53. As a device 72 for detecting the disassembly of at least one cover 76, a separate sensor for detecting the disassembly of at least one cover 76 can also be configured on the power transmission device 38 as a device 72, for example, as a mechanically actuated electrical contact switch or contact sensor (not shown) between the securing cover 53 and the main wall 32, so that the disassembly of the securing cover 53 actuates this electrical contact switch or contact sensor, and the change in an electrical current switched by the electrical contact switch or contact sensor is detected by the control unit 86 as a control signal.

[0087] Overall, significant advantages are associated with the power transmission device 38 according to the invention, the fuel cell unit 1 according to the invention, and the fuel cell system 2 according to the invention. The device 72 detects the disassembly of at least one cover 76, and during the disassembly or simultaneously with the disassembly of the at least one cover 76, the control unit 86 actuates the current switch and the resistance current switch, so that the mating connector 76 is de-energized by the current switch, ieis electrically separated from the fuel cell stack 3, and the resistance current switch short-circuits the electrical current from the fuel cell stack 3 to the electrical resistor 74, so that the residual electrical energy in the fuel cell stack 3 is dissipated until the remaining fuel is consumed, and thus, within a few seconds, no electrical current is present at the accessible points in the power transmission device 38. This ensures that there is no risk of a short circuit or of a person coming into contact with electrical voltage when dismantling a cover 76.The control unit 86 is supplied with electrical energy from the fuel cell stack 3 and is connected via power lines to a central control and / or regulating unit of a motor vehicle, so that the central control and / or regulating unit of the motor vehicle can also issue a command to actuate the current switch and / or the resistance current switch by means of a control signal through the power lines of the control unit 86, for example in the event of an accident involving high acceleration. The actuation of the current switch and / or the resistance current switch can thus also be triggered by the central control and / or regulating unit of the motor vehicle in the event of a motor vehicle accident detected by an acceleration sensor with the deployment of an airbag. This can further increase safety.

Claims

Claims 1 . Power transmission device (38) for a fuel cell unit (1) or a fuel cell system (2), comprising - a device housing (39) with at least one removable cover (42, 53, 76, 77) for opening the device housing (39), - at least two current conductors (48, 50) for conducting the electrical current generated by a fuel cell stack (3), - a power switch for deactivating and activating the transmission of the electrical current generated by the fuel cell stack (3) to a main consumer, characterized in that the power transmission device (38) comprises a device (72) for detecting disassembly of the at least one removable cover (42, 53, 76, 77) from the remaining device housing (39).

2. Power transmission device according to claim 1, characterized in that an electrical fuse (52) for an electrical unit of the fuel cell unit (1) or the fuel cell system (2) is arranged within the device housing (39) of the power transmission device (38).

3. Power transmission device according to one or more of the preceding claims, characterized in that the device housing (39) comprises a main wall (42), in particular a cover main wall (42), and a securing cover (53) is fastened to the main wall (42).

4. Power transmission device according to claim 3, characterized in that the at least one removable cover (42, 53, 76, 77) is the main wall (42) of the device housing (39) and / or the fuse cover (53).

5. Power transmission device according to one or more of the preceding claims, characterized in that an electrical mating connector (65) is formed on the outside of the power transmission device (38) for electrical connection to an electrical connector with a power cable.

6. Power transmission device according to one or more of the preceding claims, characterized in that the device (72) for detecting disassembly of the at least one removable cover (42, 53, 76, 77) is formed by the remaining device housing (39) and / or a control unit (86) and / or by the electrical mating connector (65) and / or a sensor, in particular a contact sensor.

7. Power transmission device according to one or more of claims 3 to 6, characterized in that the power transmission device (38) is designed such that the at least one cover (42, 53, 76, 77), in particular the main wall (42) and / or the securing cover (53), can only be removed from the device housing (39), in particular the main wall (42), if no electrical plug-in connector, preferably with a power cable, is plugged into the electrical mating plug-in connector (65).

8. Power transmission device according to one or more of the preceding claims, characterized in that the power transmission device (38) comprises a resistance current switch for conducting the electrical current generated by the fuel cell stack (3) through an electrical resistor (74) as an electrical short circuit of the fuel cell stack (3).

9. Power transmission device according to claim 8, characterized in that the power transmission device (38) comprises a control unit (86) for switching the current switch and / or resistance current switch in dependence on a control signal of the device (72) for detecting the disassembly of the at least one removable cover (42, 53, 76, 77).

10. Power transmission device according to claim 9, characterized in that the operation of the control unit (86), in particular exclusively, can be carried out with electrical energy of the fuel cell stack (3).

11. Power transmission device according to claim 10, characterized in that the operation of the control unit (86) with electrical energy of the fuel cell stack (3) can be carried out indirectly with a galvanic isolating device (91) integrated into the power transmission device (38) electrically between the fuel cell stack (3) and the control unit (86), in particular the galvanic isolating device (91) is structurally integrated into the control unit (86), so that the control unit (86) is galvanically separated from the fuel cell stack (3).

12. Power transmission device according to claim 10 or 11, characterized in that the control unit (86), in particular always, when the at least one removable cover (42, 53, 76, 77) is dismantled from the remaining device housing (39) due to the control signal of the device (72) for detecting dismantling of the at least one removable cover (42, 53, 76, 77) switches the power switch so that the forwarding of the electrical current generated by the fuel cell stack (3) to the main consumer is interrupted.

13. Power transmission device according to one or more of claims 10 to 12, characterized in that the control unit (38), in particular always, upon dismantling of the at least one removable cover (42, 53, 76, 77) from the remaining device housing (39) due to the control signal of the device (72) for detecting dismantling of the at least one removable cover (42, 53, 76, 77) the resistance current switch switches in such a way that a conduction of the electrical current generated by the fuel cell stack (3) through the electrical resistance can be carried out as an electrical short circuit of the fuel cell stack (3).

14. Fuel cell unit (1) for the 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 in 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 oxidant supply system (26) for oxidants, at least one fuel supply system (29), at least one cooling system, a power transmission device (38), characterized in that the power transmission device (38) is designed according to one or more of claims 1 to 13.

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