Vehicle with a fuel cell system, and method for the operation thereof

Abstract

The invention relates to a vehicle (1), in particular a utility vehicle, comprising a fuel cell system (3) having a first compressor unit (5) for supplying a fuel cell (13) with pressurised air (L), and a second compressor unit (19) for supplying a pressurised air system (17) of the vehicle (1) with pressurised air (L). According to the invention, the first compressor unit (5) has an outlet (6) which is fluidically connected to an inlet (24) of the second compressor unit (19) by means of a branch line (10), in such a way that a first sub-flow (T1) of the pressurised air (L) output by the first compressor unit (5) is supplied to the fuel cell (13), and a second sub-flow (T2) of the pressurised air (L) output by the first compressor unit (5) is supplied to the second compressor unit (19).

Description

[0001] Vehicle with fuel cell system and method for its operation

[0002] The present invention relates to a vehicle, in particular a commercial vehicle, with a fuel cell system, which has a first compressor unit for supplying a fuel cell with compressed air, and a second compressor unit for supplying a compressed air system of the vehicle with compressed air. Vehicles of the type described above are generally known. According to the invention, a compressed air system is understood to be the compressed air architecture of the vehicle, which supplies all safety-relevant and non-safety-relevant pneumatic consumers of the vehicle with compressed air via one or more line circuits, for example a pneumatic braking system and / or a pneumatic chassis of the vehicle. Due to the special requirements for the control of the fuel cell, fuel cell systems generally have their own dedicated compressor unit for supplying compressed air to the fuel cell.

[0003] While "conventional" compressors for supplying compressed air to compressed air systems are generally designed to generate high system pressures, which can be in the range of above 10 bar, sometimes above 12 bar, or significantly higher, and often rely on piston compressors with speeds in the four-digit range while simultaneously delivering low throughput to achieve these pressures, the compressor units of fuel cell systems typically feature turbo compressors, which deliver much higher throughputs at comparatively low system pressures in the order of 5 bar or less. For this purpose, the compressor units of fuel cell systems are typically operated in the high five-digit speed range. Both the compressed air supply for the vehicle's compressed air systems and the compressed air supply for the fuel cell systems generally function satisfactorily.Compressor units, like other vehicle components, are electrical consumers. As mobility evolves, the energy required to operate the vehicle is increasingly being provided in electrical form within the vehicle and stored in appropriate energy storage systems. The principle of energy efficiency also applies to electrical consumers, including compressor units. The space required for the compressor units represents a design limitation.

[0004] The invention was based on the objective of overcoming the challenge described above as comprehensively as possible. In particular, the objective of the invention was to achieve increased efficiency in a vehicle of the type described above.

[0005] The invention achieves the object underlying it in a vehicle of the type described at the outset in that the first compressor unit has an outlet which is fluidly connected to an inlet of the second compressor unit by means of a branch line in such a way that a first partial flow of the compressed air output by the first compressor unit is fed to the fuel cell, and a second partial flow of the compressed air output by the first compressor unit is fed to the second compressor unit.

[0006] The invention is based on the finding that the second compressor unit, which is responsible for the vehicle's compressed air system beyond the fuel cell, must generate comparatively high pressures but requires only very low flow rates, on the order of <1000 l / min at approximately 12.5 bar at the outlet of the second compressor unit, in particular <500 l / min at approximately 12.5 bar at the outlet of the second compressor unit. This is where the invention comes in, connecting the outlet of the first compressor unit to the inlet of the second compressor unit via the branch line. The first compressor unit thus becomes the pre-compressor for the second compressor unit.The second compressor unit can therefore perform the compression work starting from a higher pressure level, which can lead to a significantly reduced power requirement compared to the second compressor unit, which is all the greater the higher the pressure at the outlet of the first compressor unit. This allows the second compressor unit to be dimensioned significantly smaller overall, which results in both cost advantages and a reduction in installation space. Since the required additional throughput is small relative to the throughput already required by the fuel cell, the first compressor unit does not need to be dimensioned larger - or at least not significantly larger. In addition to the significantly lower power consumption, there are also other efficiency-enhancing factors that result from the series connection of the first compressor unit of the fuel cell system and the second compressor unit of the compressed air system.The cost advantages particularly affect the cost-intensive components of the compressor units, such as the electrical machines and power electronics.

[0007] In an advantageous development, the second compressor unit is fluidly connected to a compressed air reservoir on the outlet side and is configured to further compress the compressed air supplied to it by the first compressor unit and feed it to the compressed air reservoir. Depending on the pressure level on the outlet side of the second compressor unit, it may even be advantageous to pass the compressed air through the second compressor unit without additional compression work until the pressure level of the outlet side of the first compressor unit is reached at least once on the outlet side, in particular the compressed air reservoir, and only then to begin the additional compression work.

[0008] In a preferred embodiment, the first compressor unit has an air filter arranged upstream of the branch line. More preferably, the first compressor unit has a compressor, and the air filter is arranged upstream of the compressor and configured to filter the air supplied to the first compressor unit before it enters the compressor. Depending on the application, multi-stage compressors, i.e. compressors having more than one compressor stage, are also certainly used for compression in the compressor units for the fuel cell system. To understand the invention, however, an explanation based on just a single compressor is sufficient. It should be understood that the invention also applies to compressor units having more than one compressor, whereby it is generally advantageous to position the air filter as far upstream as possible in order to protect the compressor unit from the ingress of dirt.

[0009] In a further preferred embodiment, the fuel cell system, in particular the first compressor unit, is configured to be operated with a variable throughput, and the vehicle has a control unit configured to generate an air request signal for controlling the throughput of the first compressor unit. Given that the additional throughput required in the first compressor unit to feed the branch line is small compared to the throughput required anyway for the fuel cell, namely generally in the single-digit percentage range relative to the throughput for the fuel cell, in preferred embodiments, controlling the rotational speed is sufficient, in particular, to control the throughput in the event of an air request signal being present.

[0010] If, according to the invention, reference is made to the throughput of the compressor units, this is to be understood as meaning that the throughput can be characterized by the mass flow flowing through the compressor unit, or also by the volume flow and pressure flowing through the compressor unit, preferably on the outlet side in each case.

[0011] The air demand signal according to the invention is representative of the additional delivery required by the second partial flow. The second compressor unit is preferably configured to operate at a constant operating point, and thus it is possible to predict with good precision how much throughput, i.e. how much additional delivery requirement, is necessary on the part of the first compressor unit when the second compressor unit needs to start operating in order to supply the vehicle's compressed air system with additional compressed air. The inlet and outlet pressures of the second compressor unit are known, and the throughput through the second compressor unit can be selected so that it can be operated at a favorable operating point.

[0012] All of these variables can be determined in advance in preliminary tests and during system design, so that the air request signal can, in the simplest case, be a digital signal with the states "0" (no air request signal is present) and "1" (air request signal is present). The air request signal can be transmitted as a predetermined current or voltage signal, or as a coded signal, for example, via a vehicle bus system such as a CAN bus.

[0013] In a further preferred embodiment, the first compressor unit is signal-conductingly connected to the control unit and configured to adjust, in particular increase, the flow rate it delivers depending on the air request signal. In other words, when the air request signal is applied to the first compressor unit, the first compressor unit controls its flow rate such that both the fuel cell can be supplied with the first partial flow and the second compressor unit with the second partial flow.

[0014] The first compressor unit is preferably configured to deliver a first throughput in a first operating mode, which is supplied exclusively to the fuel cell when the second compressor unit is inactive, and to deliver a second throughput in a second operating mode that is higher than the first throughput and from which the first partial flow for the fuel cell and the second partial flow for the compressor unit are formed when the second compressor unit is active. In other words, the compressor unit is configured to transition from the first operating mode to the second operating mode as soon as the air request signal is present.

[0015] Preferably, the first compressor unit is configured to compress the air in the second operating mode to the same initial pressure as in the first operating mode. The pressure is preferably in a range below 5 bar, such as from 2 bar to 4 bar. Supplying compressed air to the second compressor unit thus does not compromise the operation of the fuel cell system. At the same time, in the simplest case, such control simply requires adjusting the operation of the first compressor unit to a higher speed level, which can be determined in advance mathematically or experimentally.

[0016] In a further preferred embodiment, the vehicle has a pressure sensor for detecting the air pressure in the compressed air reservoir, and the control unit is connected to the pressure sensor in a signal-conducting manner and configured to generate the air request signal as soon as the air pressure in the compressed air reservoir reaches or falls below a predetermined switch-on pressure. The switch-on pressure is preferably in a range of 10 bar or less. Alternatively or additionally, the compressed air reservoir has a target pressure value, also referred to as the operating pressure, for example in the range of 12.5 bar or more. The control unit preferably generates the air request signal as soon as the air pressure in the compressed air reservoir is 10% or more below the target pressure value.

[0017] In a further preferred embodiment, the control unit is configured to control the second compressor unit to compress the compressed air supplied to it after the air request signal has been generated. In a first preferred variant, the control unit is configured to control the second compressor unit after a predetermined (first) delay period has elapsed, wherein the delay period is in particular in a range of 0.5 - 3.5 seconds. In a second variant, the control unit is preferably alternatively or additionally configured to control the second compressor unit after the first compressor unit has transmitted a confirmation signal to the control unit that the throughput has been adjusted.In a third preferred variant, the vehicle has a sensor for detecting the throughput of the first compressor unit, for example a mass flow sensor or a volume flow sensor (then preferably in conjunction with a pressure sensor). The sensor is connected to the control unit or the second compressor unit in a signal-conducting manner and is configured to send a representative signal for the throughput to the respective unit. These controls ensure that the second compressor unit does not begin compression work too early, which could, in unfavorable cases, result in an insufficient supply of compressed air to the fuel cell. By controlling the first compressor upstream, it is prevented that the second compressor runs at an unfavorable efficiency (or not at all) due to insufficient inlet pressure.

[0018] In a further preferred embodiment, the control unit is configured to put the second compressor unit into the active state as long as the air request signal is present.

[0019] In a further preferred embodiment, the control unit is configured to generate the air request signal until the air pressure in the compressed air reservoir reaches or exceeds a predetermined cut-off pressure. The cut-off pressure is preferably in a range of 12.0 bar or higher. Alternatively or additionally, the cut-in pressure is in a range of 10% - 15% below the cut-off pressure.

[0020] In a further preferred embodiment, the first compressor unit is configured to adapt, in particular reduce, the throughput after a predetermined (second) delay period when the air request signal ceases. The delay period is preferably in a range from 0.5 seconds to 3.5 seconds. This continued delivery of the higher throughput also serves to prevent an undersupply. In a preferred embodiment, the fuel cell system has a control unit, for example a fuel cell controller, which is configured to control the first compressor unit and which is connected to the control unit in a signal-conducting manner. The connection between the control unit of the fuel cell system and the control unit of the compressed air system could be ensured, for example, via a CAN bus or a similar bus connection.In alternative preferred embodiments, the control unit can also be integrated into the fuel cell control system in hardware or software.

[0021] In a further preferred embodiment, the vehicle has an air treatment module downstream of the second compressor unit, with the control unit preferably being integrated into the air treatment module. Here, too, the control unit can alternatively be designed as a dedicated, standalone control unit. The control unit can, for example, alternatively be assigned to the second compressor unit or be integrated into its control system via hardware or software.

[0022] The above-described air processing module, also referred to as APU, and in particular as eAPU (Air Processing Unit), preferably comprises an air dryer and / or a valve arrangement such as a multi-circuit protection valve, and / or a pressure sensor. If the air processing module comprises the control unit, the control unit is preferably further configured to regulate the pressure in the flow process on the outlet side of the second compressor unit, and thus the operation of the compressor, and to generate the air request signal as described above. Depending on the presence of additional logic units in the vehicle, it may also be expedient to integrate the control unit into other logic units not named here.

[0023] In the above embodiments, a series connection of the first compressor unit and the second compressor unit was described, which always also assumed the operation of the first compressor unit for pre-compression for the operation of the second compressor unit. Situations may arise during vehicle operation in which the first compressor unit is not active, for example, in the event of defects or when the fuel cell is shut down when driving down long downhill stretches or during periods of inactivity. If operation of the second compressor unit is nevertheless necessary in such situations, the vehicle, in a preferred embodiment, has a bypass line that bridges the first compressor unit and opens upstream of the second compressor unit.In this way, the inlet for the air to be compressed, which would otherwise bypass the first compressor unit, is connected directly to the second compressor unit, and the second compressor unit can be operated bypassing the first compressor unit, albeit at a lower inlet pressure than would be ideal for its operation.

[0024] In embodiments in which the first compressor unit has at least one compressor, i.e., one compressor stage, and in which the air filter flow is arranged upstream of the compressor, the bypass line preferably extends from an outlet between the air filter and the compressor to the branch line. This means that even if the second compressor unit must be operated without the first compressor unit, only one air filter is required. This filter can be assigned to the central inlet for the compressor units and continues to function even when the first compressor unit is not active.

[0025] The invention has been described above with reference to a first aspect of a vehicle. In a further aspect, the invention further relates to a method for operating a vehicle, in particular a commercial vehicle. The invention achieves the object described above with such a method, in which the method comprises the steps:

[0026] - supplying a fuel cell with compressed air by means of a first compressor unit, and - supplying a compressed air system of the vehicle with compressed air by means of a second compressor unit, wherein a first partial flow of the compressed air output by the first compressor unit is supplied to the fuel cell, and a second partial flow of the compressed air output by the first compressor unit is supplied to the second compressor unit.

[0027] With regard to the second aspect, the invention utilizes the same advantages and considerations as the vehicle according to the first aspect. Preferred embodiments of the vehicle are also preferred embodiments of the method, and vice versa.

[0028] In exemplary preferred embodiments, the method is further developed with one, several or all of the following features:

[0029] - The compressed air supplied to the second compressor unit from the first compressor unit is additionally compressed and fed to the compressed air storage unit; and / or

[0030] - The air supplied to the first compressor unit is filtered upstream of the branch line, in particular upstream of the first compressor unit; and / or

[0031] - the first compressor unit is operated with a variable throughput; an air request signal is generated to control the throughput of the first compressor unit, preferably as soon as an air pressure in the compressed air reservoir reaches or falls below a predetermined switch-on pressure; further preferably until a predetermined switch-off pressure is reached or exceeded; and / or

[0032] - the flow rate delivered by the first compressor unit is adjusted, in particular increased, depending on the air request signal;

[0033] - in a first operating mode, a first throughput is delivered which, when the second compressor unit is inactive, is supplied exclusively to the fuel cell, and in a second operating mode, a second throughput is delivered which is higher than the first throughput and from which, when the second compressor unit is active, the first partial flow for the fuel cell and the second partial flow for the second compressor unit are formed, wherein preferably the air in the second operating mode is compressed to the same output pressure as in the first operating mode and / or the same throughput is delivered as the second partial flow as in the first operating mode as the total throughput; and / or

[0034] - the second compressor unit is activated after the air request signal has been generated; and / or

[0035] - the throughput delivered by the first compressor unit is adjusted, in particular reduced, after a predetermined delay period from the cessation of the air request signal; and / or

[0036] - the first compressor unit is bypassed by means of a bypass line which opens upstream of the second compressor unit.

[0037] The invention is described in more detail below with reference to preferred embodiments in the accompanying figures. Herein:

[0038] Fig. 1 is a schematic representation of a vehicle according to a preferred embodiment, and

[0039] Fig. 2 shows an exemplary procedure for operating the vehicle according to Fig. 1 .

[0040] Fig. 1 shows a schematic representation of a vehicle 1, which can be a commercial vehicle, for example. The vehicle 1 has a fuel cell system 3, which includes a compressor unit 5. The compressor unit 5 has at least one (first) compressor 7, which is driven by an electric machine 9. The compressor 7 can be, for example, a radial compressor, axial compressor or scroll compressor. The compressor unit 5 is designed to suck in air containing oxygen O2 at an inlet 4, compress it to an outlet pressure pn and output it at an outlet 6 with a throughput D controlled according to the operation of the compressor unit 5. Thus, compressed compressed air L is supplied to a fuel cell 13 on the cathode side via a main line 8. Optionally, an air humidifier 11 is arranged in the main line 8.The fuel cell system 3 has a control unit 15, which can be constructed as one or more structural units and can be, for example, the fuel cell controller and / or a compressor control unit. The control unit 15 can be designed as a dedicated control unit or integrated into the fuel cell 13 or the compressor unit 5 in terms of hardware or software.

[0041] In addition to the fuel cell system 3, the vehicle 1 also has a compressed air system 17. The compressed air system 17 serves to supply safety-relevant and non-safety-relevant pneumatic consumers of the vehicle 1 with compressed air L and has a dedicated compressor unit 19. The compressor unit 5 of the fuel cell system 3 is thus a first compressor unit, and the compressor unit 19 of the compressed air system 17 is a separate, dedicated second compressor unit.

[0042] The second compressor unit 19 has an electric machine 21, which is configured to drive a (second) compressor 23 of the second compressor unit 19, but could alternatively be connected, for example, to an internal combustion engine via a clutch. The compressor

[0043] 23 can, for example, be a piston or scroll compressor.

[0044] The second compressor unit 19 can, for example, be designed as a piston compressor, while the first compressor unit 5 of the fuel cell system is preferably designed as a turbo compressor.

[0045] The second compressor unit 19 of the compressed air system 17 is connected via an inlet

[0046] 24 and a branch line 10 are fluidly connected to the outlet 6 of the first compressor unit 5 of the fuel cell system 3. The second compressor unit 19 is configured to further compress the compressed air L supplied to it via the branch line 10 from the outlet pressure pu of the first compressor unit 5 to a second outlet pressure pi_2 > pu , and to discharge this further compressed partial flow T2 via an outlet 26, while compressed air L continues to be conveyed to the fuel cell 13 at pn as the first partial flow Ti via the main line 8. The total throughput D is composed of Ti and T2.

[0047] The compressed air system 17 has an air processing module 27, also referred to as an APU (Air Processing Unit) or eAPU (electronic Air Processing Unit), connected downstream of the second compressor unit 19. The air processing module 27 is configured to condition the air compressed by the second compressor unit 19, for example, to dry it, and to supply it directly or indirectly to a compressed air reservoir 29 fluidly connected to the air processing module 27.

[0048] The compressed air system 17 further comprises a control unit 31, which can be integrated, for example, in software or hardware into the air treatment module 27 or can be a standalone control unit. The control unit 31 of the compressed air system 17 is configured to activate the second compressor unit 19 by means of a compressor control signal Sc.

[0049] The control unit 31 is signal-conductingly connected to a pressure sensor 33, wherein the pressure sensor 33 is configured to detect an air pressure ps = pi_2 of the compressed air reservoir 29. The pressure sensor 33 is preferably structurally associated with the compressed air reservoir 29, but can also be arranged in the fluid line between the air treatment module 27 and the compressed air reservoir 29, or integrated into the air treatment module 27.

[0050] The control unit 31 is configured to send an air request signal SL to the fuel cell system 3 as soon as the pressure ps in the compressed air reservoir 29 reaches or falls below a predetermined cut-in pressure ps. The cut-in pressure ps is preferably 10-15% or more below the actual operating pressure of the compressed air reservoir, as described in detail in the general section. The control unit 31 is configured to transmit the air request signal Si_ and the compressor control signal Sc for as long as necessary to adequately supply the compressed air reservoir 29 with compressed air L. In particular, the control unit 31 is configured to stop the transmission of the air request signal SL and the compressor control signal Sc when the pressure ps of the compressed air reservoir 29 has reached or exceeded a cut-off pressure PA, which is preferably 10-15% above PE.

[0051] The generation and deactivation of the signals SL and Sc can take place simultaneously, but can also take place in staggered time periods, as will be explained in more detail with reference to Fig. 2.

[0052] The fuel cell system 3 is configured to switch the operation of the first compressor unit 5 between a first operating mode Bi and a second operating mode B2 depending on receipt of the air request signal SL. In the first operating mode Bi, the first compressor unit 5 is configured to deliver and compress a first throughput Di that is sufficient for operation of the fuel cell 13, in particular for operation with excess oxygen.

[0053] The first compressor unit 5 is designed to deliver a second throughput D2 in the second operating mode B2, which is so much greater than the first throughput Di that the second partial flow T2 is additionally delivered without the outlet pressure pui dropping.

[0054] The second operating mode B2 is generally activated when the control unit 31 of the compressed air system 17 activates the second compressor unit 19 by transmitting the compressor control signal Sc to increase the pressure in the compressed air reservoir 29. When the second compressor unit 19 is activated, the flow rate D2 present at the outlet 6 of the first compressor unit 5 is divided into the first partial flow Ti and the second partial flow T2, wherein the first partial flow Ti preferably has a flow rate exactly as high as Di in the first operating mode Bi. The additional flow rate (D2 - Di) flows as the second partial flow T2 through the branch line 10 into the first compressor unit 19.

[0055] The vehicle 1 has an air filter 34, which is designed to clean the O2 air sucked in by the fuel cell system 3 before it enters the first compressor unit 5 in a generally known manner. By connecting the first compressor unit of the fuel cell system in series with the second compressor unit 19 of the compressed air system 17, a further specific advantage of the invention arises: Only a single air filter 34 is required for contamination-free operation of both compressor units 5, 19. The air filter 34 can be assigned to the fuel cell system 3, but it can also, as indicated here in Fig. 1, be connected upstream of the fuel cell system 3 as a dedicated unit. The air filter 34 is also active in bridging mode by means of the bypass line 37 and is then used to directly filter the flow of O2 air supplied exclusively to the second compressor unit 19, bypassing the first compressor unit 5.

[0056] The application described above, which is considered the main application, requires simultaneous operation of the first compressor unit 5 and the second compressor unit 19 for at least certain periods of time in the second operating mode B2. However, there may be operating situations in which the first compressor unit 5 cannot be operated, but compressed air is still required to increase the compressed air reservoir 29. For these situations, the vehicle 1 has a bypass line 37 extending from an outlet 35 upstream of the compressor 7 to a connector 41 in the branch line 10. A check element 39 prevents an unwanted backflow of compressed air L toward the outlet 35.

[0057] Fig. 2 illustrates an exemplary process sequence for the operation of the vehicle 1 according to Fig. 1.

[0058] In the following description, several process steps are described and illustrated sequentially. In actual operation of vehicle 1, however, these steps do not necessarily have to be performed in this chronological order, but can at least partially occur simultaneously. The following sequential description serves to facilitate understanding.

[0059] In an initial step 101 of the method 100, the vehicle 1 is driven for driving. As soon as it is decided in a first decision step 103 that operation of the fuel cell system 3 is necessary, in the next method step 105, the fuel cell 13 is driven in the first operating mode Bi to deliver a first throughput Di of compressed air L. As long as the delivery of compressed air L is carried out by means of the first compressor unit 5, a fuel cell is supplied with compressed air by means of a first compressor unit in step 102.

[0060] If the vehicle 1 requires compressed air from the compressed air system 17 for its operation, this is made available from the compressed air reservoir 29. As soon as it is detected in a step 107 that the pressure ps reaches or falls below the switch-on pressure PE, the control unit 31 generates the air request signal SL in step 109, as a result of which the first compressor unit 5 is caused to control the second throughput D2 in the second operating mode B2 in step 111. As soon as the required throughput D2 for the two partial flows Ti, T2 is reached, and / or after the expiration of a predetermined first delay period ti, which is checked in step 113, the second compressor unit 19 is also controlled to begin operation by means of the compressor control signal Sc in step 115.

[0061] As long as the second partial flow T2 is being conveyed by the second compressor unit 19, a method step 116 of supplying the compressed air system 17 of the vehicle 1 with compressed air L by means of the second compressor unit 19 is carried out, wherein the first partial flow Ti of the compressed air L output by the first compressor unit 5 is fed to the fuel cell 13, and the second partial flow T2 of the compressed air L output by the first compressor unit 5 is fed to the second compressor unit 19. The air request signal SL remains present during this time. The simultaneous operation of both compressor units 5, 19 continues as long as the pressure ps in the compressed air reservoir 29 still needs to be increased.

[0062] As soon as it is determined in step 117 that the pressure ps reaches or exceeds the cut-off pressure PA, the operation of the second compressor unit is stopped by switching off the compressor control signal Sc in step 121, preferably after observing a second delay period t2 in step 119.

[0063] After preferably a third delay period t3 has been reached in step 123, the air request signal SL can also be switched off in step 125, and the operation of only the first compressor unit 5 according to step 105 or no compressor unit according to step 101 can be returned to.

[0064] The following discusses an alternative operating situation that may arise. If, during operation according to step 101 of the vehicle 1, the check according to step 103 determines that operation of the fuel cell system 3 is not required, but in a subsequent step 104 it is determined that the pressure ps in the compressed air reservoir 29 falls below the switch-on pressure ps, the compressor control signal Sc is transmitted from the control unit 31 to the second compressor unit 19 without first controlling the first compressor unit 5 (see step 106).

[0065] Consequently, in step 108, the first compressor unit 5 of the fuel cell system 3 is bypassed by means of the bypass line 37. In step 110, the second compressor unit 19 of the compressed air system 17 compresses the air O2 supplied on the inlet side at ambient pressure (or the inlet pressure upstream of the fuel cell system 3) in a third operating mode B3. Preferably, a third throughput D3 is delivered, which may, for example, correspond to the previously described partial flow T2=(D2-DI). As soon as it is determined in step 112 that the pressure ps in the compressed air reservoir 29 is greater than or equal to the shutdown pressure PA, the compressor control signal Sc can be deactivated in step 114, and the vehicle can be operated as in step 101.

[0066] LIST OF REFERENCE SYMBOLS (PART OF THE DESCRIPTION)

[0067] 1 vehicle

[0068] 3 Fuel cell system

[0069] 4 Inlet, fuel cell system

[0070] 5 first compressor unit, fuel cell system

[0071] 6 Outlet, fuel cell system

[0072] 7 (first) compressor, fuel cell system

[0073] 8 Main line

[0074] 9 electric machine, fuel cell system

[0075] 10 Branch management

[0076] 11 humidifiers

[0077] 13 Fuel cell

[0078] 15 Control unit, fuel cell system

[0079] 17 Compressed air system

[0080] 19 second compressor unit, compressed air system

[0081] 21 electric machine, compressed air system

[0082] 23 (second) compressor, compressed air system

[0083] 24 Inlet, second compressor unit

[0084] 29 Compressed air storage, compressed air system

[0085] 31 Control unit, compressed air system

[0086] 34 air filters

[0087] 35 Outlet to bypass line

[0088] 37 Bypass line

[0089] 41 Bypass line connector

[0090] 100 Procedure 101 Initial step

[0091] 102 Supplying the fuel cell

[0092] 103 Decision on fuel cell operation

[0093] 104 Capture p s < PE

[0094] 105 Start operating mode Bi

[0095] 106 Start controlling second compressor unit

[0096] 107 Capture p s < PE

[0097] 108 Bridging first compressor unit

[0098] 109 Generation of air request signal SL

[0099] 110 Start operating mode B3

[0100] 111 Start operating mode B2

[0101] 112 Capture p s PA

[0102] 113 Capture D=Ü2 and / or ti

[0103] 114 End of operating mode B3

[0104] 115 Start controlling second compressor unit

[0105] 116 Supplying the compressed air system

[0106] 117 Capture p s PA

[0107] 119 Capture t2

[0108] 121 End of control of second compressor unit, end B2

[0109] 123 Capture t3

[0110] 125 End generation of air request signal SL

[0111] BI, B2, B3 operating modes

[0112] D, Di, D2, D3 throughput

[0113] L Compressed air

[0114] O2 air ti, t2, t3 delay time Ti, T2 partial flow

[0115] SL air delivery signal

[0116] Sc control signal pn output pressure first compressor unit pi_2 output pressure second compressor unit ps air pressure compressed air storage

[0117] PE switch-on pressure

[0118] PA cut-off pressure

Claims

REQUIREMENTS:

1. Vehicle (1), in particular a commercial vehicle, with a fuel cell system (3) comprising a first compressor unit (5) for supplying a fuel cell (13) with compressed air (L), and a second compressor unit (19) for supplying a compressed air system (17) of the vehicle (1) with compressed air (L), characterized in that the first compressor unit (5) has an outlet (6) which is connected by means of a branch line (10) in such a fluid-conducting manner to an inlet (24) of the second compressor unit (19) such that a first partial flow (Ti) of the compressed air (L) supplied by the first compressor unit (5) is supplied to the fuel cell (13), and a second partial flow (T2) of the compressed air (L) supplied by the first compressor unit (5) is supplied to the second compressor unit (19).

2. Vehicle (1) according to claim 1, wherein the second compressor unit (19) is connected fluid-conductingly to a compressed air reservoir (29) on the outlet side and is configured to further compress the compressed air (L) supplied to it by the first compressor unit (5) and to supply it to the compressed air reservoir (29).

3. Vehicle (1 ) according to claim 1 or 2, wherein the first compressor unit (5) has an air filter (34) which is arranged upstream of the branch line (10).

4. Vehicle (1 ) according to claim 3, wherein the first compressor unit (5) comprises a compressor (7), and the air filter (34) is arranged upstream of the compressor (7) and is configured to filter air (O2) supplied to the first compressor unit (5) before it enters the compressor (7).

5. Vehicle (1) according to any of the preceding claims, wherein the first compressor unit (5) is configured to operate with a variable flow rate (D; Di ; D2) and the vehicle (1 ) has a control unit (31) configured to generate an air request signal (SL) to control the flow rate of the first compressor unit (5).

6. Vehicle (1 ) according to claim 5, wherein the fuel cell system 3, in particular the first compressor unit (5), is connected to the control unit (31) via a signal conductor and is configured to adjust, in particular to increase, the flow rate (D) supplied by it depending on the air request signal (SL).

7. Vehicle (1) according to claim 6, wherein the first compressor unit (5) is configured to deliver a first throughput (Di) in a first operating mode (Bi), which is supplied exclusively to the fuel cell (13) when the second compressor unit (19) is inactive, and to deliver a second throughput (D2) in a second operating mode (B2), which is higher than the first throughput (Di), and from which, when the second compressor unit (19) is active, the first partial flow (Ti) for the fuel cell (13) and the second partial flow (T2) for the second compressor unit (19) are formed.

8. Vehicle (1 ) according to claim 7, wherein the first compressor unit (5) is configured to compress the air to the same output pressure (pu) in the second operating mode (B2) as in the first operating mode (Bi).

9. Vehicle (1) according to one of claims 5 to 8, with a pressure sensor (33) for detecting the air pressure (ps) in the compressed air reservoir (29), wherein the control unit (31) is connected to the pressure sensor (33) via a signal conductor and is configured to generate the air request signal (SL) ZU as soon as the air pressure (ps) in the compressed air reservoir (29) reaches or falls below a predetermined switch-on pressure (ps).

10. Vehicle (1 ) according to one of claims 5 to 9, wherein the control unit (31 ) is configured to control the second compressor unit (19) to compress the compressed air (L) supplied to it, after the air request signal (SL) has been generated, preferably after a predetermined delay period (ti).

11. Vehicle (1) according to one of claims 5 to 10, wherein the control unit (31) is configured to keep the second compressor unit (19) in the active state as long as the air request signal (SL) is present.

12. Vehicle (1) according to one of claims 9 to 11, wherein the control unit (31) is configured to generate the air request signal (SL) until the air pressure (ps) in the compressed air reservoir (29) reaches or exceeds a predetermined cut-off pressure (PA).

13. Vehicle (1 ) according to one of claims 5 to 12, wherein the fuel cell system (3), in particular the first compressor unit (5), is configured to adjust, in particular reduce, the throughput (D) after a predetermined delay period (t2, ts) from the cessation of the air request signal (SL).

14. Vehicle (1 ) according to one of claims 5 to 13, wherein the fuel cell system (3) has a control unit (15) which is configured to control the first compressor unit (5) and which is connected to the control unit (31 ) of the compressed air system (17) via a signal transmission.

15. Vehicle (1 ) according to one of claims 5 to 14, wherein the vehicle (1 ) has an air preparation module (27) downstream of the second compressor unit (19), and wherein the control unit (31 ) is preferably integrated into the air preparation module (27).

16. Vehicle (1 ) according to one of the preceding claims, with a bypass line (37) which bypasses the first compressor unit (5) and opens upstream of the second compressor unit (19).

17. Vehicle (1 ) according to claim 16, wherein the first compressor unit (5) has at least one compressor (7), the air filter (34) is arranged upstream of the compressor (7), and the bypass line (37) extends from a branch (35) between the air filter (34) and the compressor (7) to the branch line (10).

18. Method for operating a vehicle (1), in particular a commercial vehicle, comprising the steps: - Supplying (102) a fuel cell (13) with compressed air (L) by means of a first compressor unit (5), and - Supplying (116) a compressed air system (17) of the vehicle (1 ) with compressed air (L) by means of a second compressor unit (19), wherein a first partial flow (Ti) of the compressed air (L) output by the first compressor unit (5) is supplied to the fuel cell (13), and a second partial flow (T2) of the compressed air (L) output by the first compressor unit (5) is supplied to the second compressor unit (19).

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