FUEL CELL VEHICLE HAVING A PLURALITY OF SELECTABLE OPERATING MODES

Abstract

The invention relates to a fuel cell vehicle (200), in which the driver has more influence on the consumption and the dynamic of the vehicle (200). This is achieved by the fuel cell vehicle (200) comprising at least one sensor for detecting a first driver input and a control unit (60). The control unit (60) is configured to operate the fuel cell vehicle (200) in one of a plurality of operating modes depending on the first driver input, wherein a power consumption P.sub.AC of the air-conditioning system (70), an operating range of the fuel cell stack (10), and a transfer function for determining the power demand P.sub.EM from the second driver input are varied depending on the selected operating mode. It is provided that the driver has at least five different operating modes available, which differ in particular with respect to the available driving dynamic, the fuel consumption, and the adjustable comfort.

Claims

1. A fuel cell vehicle, comprising: a fuel cell system having a fuel cell stack for providing an electrical power P.sub.stack and at least one auxiliary unit for operating the fuel cell stack with an electrical power consumption P.sub.aux; an air-conditioning system for regulating a temperature of a vehicle interior space, the air-conditioning system including an electric auxiliary heater and an air-conditioning compressor with a collective electrical power demand P.sub.AC; an electric motor for driving the fuel cell vehicle with a power demand P.sub.EM; a plurality of sensors for detecting a temperature outside of the fuel cell vehicle, a first driver input, and a second driver input; and a control unit is configured to operate the fuel cell vehicle, based on the first driver input, in one of a plurality of operating modes, each operating mode of the plurality of operating modes provides power consumption P.sub.AC of the air-conditioning system, an operating point of the fuel cell stack, and a transfer function for determining the power demand P.sub.EM from the second driver input.

2. The fuel cell vehicle according to claim 1 wherein the control unit is configured to operate the fuel cell vehicle in a first operating mode that; provides the air-conditioning system in a first manner based on the temperature outside of the fuel cell vehicle; provides the operating point of the fuel cell stack at or near a first efficient operating point; and select the transfer function for determining the power demand P.sub.EM such that the fuel cell stack provides a net power P.sub.net with a first delay based on the second driver input, the first delay being greater than a threshold delay.

3. The fuel cell vehicle according to claim 2, wherein the control unit is configured to operate the fuel cell vehicle in a second operating mode that: provides the air-conditioning system in a second manner independent of the temperature outside of the fuel cell vehicle; provides the operating point of the fuel cell stack at or near a second threshold sound emission operating point; and select the transfer function for determining the power demand P.sub.EM such that the fuel cell stack provides a net power P.sub.net with a second delay based on the second driver input and a threshold power consumption P.sub.aux.sup.max of the at least one auxiliary unit, the second delay being greater than the threshold delay.

4. The fuel cell vehicle according to claim 2 wherein the control unit is further configured to determine the second delay such that a threshold power consumption P.sub.aux.sup.max of the at least one auxiliary unit is reduced.

5. The fuel cell vehicle according to claim 3, wherein the control unit is configured to operate the fuel cell vehicle in a third operating mode; that: provides the air-conditioning system in the first manner based on the temperature outside of the fuel cell vehicle; provides the operating point of the fuel cell stack at a third intermediate operating point; and select the transfer function for determining the power demand P.sub.EM such that the fuel cell stack provides a net power P.sub.net with a third delay based on the second driver input and a threshold power consumption P.sub.aux.sup.max of the at least one auxiliary unit.

6. The fuel cell vehicle according to claim 2 wherein the first manner includes providing the electric auxiliary heater at a temperature below a first predetermined temperature and providing the air-conditioning compressor at a temperature above a second predetermined temperature.

7. The fuel cell vehicle according to claim 5 wherein the control unit is configured to operate the fuel cell vehicle in a fourth operating mode that: provides the air-conditioning system independent of the temperature outside of the fuel cell vehicle in the second manner; determines the operating point of the fuel cell stack based on a driver, a vehicle, or an environmental parameter; selects the transfer function for determining the power demand P.sub.EM based on the driver, the vehicle, or the environmental parameter.

8. The fuel cell vehicle according to claim 7 wherein the control unit is configured to operate the fuel cell vehicle in a fifth operating that: provides the air-conditioning system based on a third driver input; determine the operating point of the fuel cell stack based on a fourth driver input; and determine the transfer function for determining the power demand P.sub.EM based on a fifth driver input.

9. The fuel cell vehicle according to claim 1, wherein the plurality of sensors includes: a first sensor configured to determine the first driver input based on a mechanical, acoustic, or electromechanical input variable; and a second sensor configured to determine the second driver input based on a pedal value.

10. The fuel cell vehicle according to claim 1, further including an automatic transmission, wherein the control unit is configured to vary control of the automatic transmission based on one of the plurality of operating modes.

11. The fuel cell vehicle according to claim 3 wherein the control unit is further configured to determine the second delay such that the threshold power consumption P.sub.aux.sup.max of the at least one auxiliary unit is reduced.

12. A device, comprising: a fuel cell system having a fuel cell stack; an air-conditioning system; an electric motor; a first sensor that detects in operation a temperature; a second sensor that detects in operation a first driver input; a third sensor that detects in operation a second driver input; and a control unit coupled to the fuel cell system, the air-conditioning system, and the electric motor, the control unit selects one of a plurality of operating modes based on the first driver input and the second driver input, each operating mode provides a power consumption of the air-conditioning system, an operating point of the fuel cell stack, and a transfer function that determines a power demand in response to the second driver input.

13. The device according to claim 12 wherein the plurality of operating modes includes a first operating mode that: operates the air-conditioning system in a first manner based on the temperature; provides the operating point of the fuel cell stack is at or near a first efficient operating point; and determines the transfer function to provide the fuel cell stack a net power with a first delay in response to the second driver input, the first delay being greater than a threshold delay.

14. The device according to claim 13 wherein the plurality of operating modes includes a second operating mode that: operates the air-conditioning system in a second manner independent of the temperature; provides the operating point of the fuel cell stack at or near a second threshold sound emission operating point; and determines the transfer function to provide the fuel cell stack a net power with a second delay based on the second driver input and a threshold power consumption of an auxiliary unit that operates the fuel cell stack, the second delay being greater than the threshold delay.

15. The device according to claim 14 wherein the control unit determines in operation the second delay such that the threshold power consumption is reduced.

16. The device according to claim 14 wherein the plurality of operating modes includes a third operating mode that: operates the air-conditioning system in the first manner based on the temperature; provides the operating point of the fuel cell stack at a third intermediate operating point; and determines the transfer function of the power demand such that the fuel cell stack provides a net power with a third delay based on the second driver input and a threshold power consumption of an auxiliary unit that operates the fuel cell stack.

17. The device according to claim 16 wherein the plurality of operating modes includes a fourth operating mode that: operates the air-conditioning system in the second manner independent of the temperature; provides the operating point of the fuel cell stack: and determines the transfer function of the power demand based on a driver, a vehicle, or an environmental parameter.

18. The device according to claim 17 wherein the plurality of operating modes includes a fifth operating mode that: operates the air-conditioning system in response to a third driver input; provides the operating point of the fuel cell stack in response to a fourth driver input; and determines the transfer function of the power demand based on a fifth driver input.

19. The device according to claim 12, further including an automatic transmission, wherein the control unit varies in operation control of the automatic transmission based on one of the plurality of operating modes.

Description

[0052] The invention is explained below in exemplary embodiments on the basis of the respective drawings. They show:

[0053] FIG. 1 a schematic representation of a fuel cell system according to an embodiment;

[0054] FIG. 2 a schematic representation of a vehicle according to an embodiment; and

[0055] FIG. 3 a schematic representation of a power demand P.sub.EM, determined based on a pedal value P.sub.W, of an electric motor and the net power P.sub.net, provided as a result of the power demand, of a fuel cell stack, and the power consumption P.sub.aux, occurring during the provision of the net power, of at least one auxiliary unit.

[0056] FIG. 1 shows a fuel cell system, denoted overall by 100, according to a preferred embodiment of the present invention. The fuel cell system 100 is part of the vehicle 200 shown in FIG. 2, in particular of an electric vehicle, which comprises an electric traction motor 51, which is supplied with electrical energy by the respective fuel cell system 100.

[0057] The fuel cell system 100 comprises as core components a fuel cell stack 10, which comprises a plurality of individual cells 11, which are arranged in the form of a stack and which are formed by alternately stacked membrane electrode assemblies (MEAs) 14 and bipolar plates 15 (see detailed view). Each individual cell 11 thus respectively comprises an MEA 14 with an ion-conductive polymer electrolyte membrane not shown in more detail here and catalytic electrodes arranged thereon on both sides. These electrodes catalyze the respective partial reaction of the fuel conversion. The anode and cathode electrodes are designed as coating on the membrane and comprise a catalytic material, such as platinum, which is provided on an electrically conductive substrate material, with a large specific surface, such as a carbon-based material.

[0058] As shown in the detailed view of FIG. 1, an anode chamber 12 is formed between a bipolar plate 15 and the anode and the cathode chamber 13 is formed between the cathode and the next bipolar plate 15. The bipolar plates 15 serve to supply the operating media in the anode and cathode chambers 12, 13 and further establishes the electrical connection between the individual fuel cells 11. Optionally, gas diffusion layers can be arranged between the membrane electrode arrangements 14 and the bipolar plates 15.

[0059] To supply the fuel cell stack 10 with the operating media, the fuel cell systems 100 comprise an anode supply 20 on the one hand and a cathode supply 30 on the other hand.

[0060] The anode supply 20 of the fuel cell system 100 shown in FIG. 1 comprises an anode supply path 21, which serves to supply an anode operating medium (the fuel), such as hydrogen, to the anode chambers 12 of the fuel cell stack 10. For this purpose, the anode supply paths 21 connect a fuel storage tank 23 to an anode inlet of the fuel cell stack 10. The anode supply 20 also comprises an anode exhaust path 22 which discharges the anode exhaust gas from the anode chambers 12 via an anode outlet of the fuel cell stack 10. The anode operating pressure on the anode sides 12 of the fuel cell stack 10 can be adjusted via an initial adjusting means 24 in the anode supply path 21.

[0061] In addition, the anode supply 20 of the fuel cell system shown in FIG. 1 comprises a recirculation line 25, which connects the anode exhaust path 22 to the anode supply path 21. The recirculation of fuel is usual in order to return the fuel, which is in most cases used overstoichiometrically, to the fuel cell stack 10. In the recirculation line 25, a recirculation conveyor 26 is arranged, preferably a recirculation fan.

[0062] The cathode supply 30 of the fuel cell system 100 shown in FIG. 1 comprises a cathode supply path 31, which supplies an oxygen-containing cathode operating medium, in particular air taken in from the environment, to the cathode chambers 13 of the fuel cell stack 10. The cathode supply 30 also comprises a cathode exhaust path 32, which discharges the cathode exhaust gas (in particular the exhaust air) from the cathode chambers 13 of the fuel cell stack 10 and supplies it, if appropriate, to an exhaust system (not shown). For conveying and compacting the cathode operating medium, a compressor 33 is arranged in the cathode supply path 31. In the exemplary embodiment shown, the compressor 33 is designed as a compressor 33, which is mainly driven by an electric motor 34 equipped with appropriate power electronics 35. The compressor 33 may also be driven by a turbine 36 (optionally with variable turbine geometry) disposed in the cathode exhaust path 32 via a common shaft (not shown).

[0063] The fuel cell system 100 shown in FIG. 1 further comprises a humidifier module 39. The humidifier module 39 is arranged in the cathode supply path 31 on the one hand so that the cathode operating gas can flow through it. On the other hand, the arrangement in the cathode exhaust path 32 allows the cathode exhaust gas to flow through it. A humidifier 39 typically comprises a plurality of water vapor permeable membranes, which are designed to be either flat or in the form of hollow fibers. In this case, the comparatively dry cathode operating gas (air) flows over one side of the membranes and the comparatively moist cathode exhaust gas (exhaust gas) flows over the other side. Driven by the higher partial pressure of the water vapor in the cathode exhaust gas, water vapors pass over the membrane into the cathode operating gas, which is moistened in this way. The cathode supply 30 furthermore comprises a bypass line 37, which connects the cathode supply line 31 to the cathode exhaust gas line 32. An adjusting means 38 arranged in the bypass line 37 serves to control the amount of the cathode operating medium passing by the fuel cell stack 10.

[0064] Various further details of the anode and cathode supply 20, 30 are not shown in the simplified FIG. 1 for reasons of clarity. For example, a water separator can be installed in the anode and/or cathode exhaust path 22, 32 in order to condense and drain product water arising from the fuel cell reaction. Finally, the anode exhaust gas line 22 can merge into the cathode exhaust gas line 32 so that the anode exhaust gas and the cathode exhaust gas are discharged via a common exhaust gas system.

[0065] The fuel cell system 100 furthermore comprises a control unit 60 and at least one consumer in the form of an electric motor 51 with the electrical power demand P.sub.EM and an air-conditioning system 70 with an electric auxiliary heater 71, an air-conditioning compressor 72, and an electrical power demand P.sub.AC. A detailed description of the function of the control unit 60 is given in the description of FIGS. 2 and 3.

[0066] FIG. 2 shows a vehicle, which is denoted with 200 overall and which comprises the fuel cell system 100 from FIG. 1, the electronic control unit 60 contained therein, an electrical power system 40, and a vehicle drive system 50. The at least one consumer 44, 51, 71, and 72 of the fuel cell system is in this case constituted by components of the fuel cell vehicle.

[0067] The electrical power system 40 comprises a voltage sensor 41 for detecting a voltage generated by the fuel cell stack 10, and a current sensor 42 for detecting a current generated by the fuel cell stack 10. The electrical power system 40 furthermore comprises an energy storage unit 44, such as a high-voltage battery or a capacitor. In the power system 40, a converter 45 is furthermore arranged, which is designed in triport topology (triport converter). The battery 44 and the air-conditioning system 70 are connected to a first side of the double DC/DC converter 45. All traction network components of the drive system 50 are connected, with a fixed voltage level, to a second side of the converter 45. In the same or a similar manner, the auxiliary units of the fuel cell system 100 itself, such as the electric motor 34 of the compressor 33 (see FIG. 1), or other electrical consumers of the vehicle can be connected to the power network.

[0068] The drive system 50 comprises an electric motor 51, which serves as traction motor of the vehicle 200. To this end, the electric motor 51 drives a drive axle 52 with drive wheels 53 arranged thereon. The traction motor 51 is connected via an inverter 43 to the electronic power system 40 of the fuel cell system 100 and constitutes the main electrical consumer of the system.

[0069] The electronic control unit 60 controls the operation of the fuel cell system 100, in particular its anode and cathode supply 20, 30, its electrical power system 40 as well as the traction motor 51 and the air-conditioning system 70. For this purpose, the control unit 60 receives different input signals, such as the voltage U, detected using the voltage sensor 41, of the fuel cell stack 10, the current I, detected using the current sensor 42, of the fuel cell stack 10, the power P.sub.stack, resulting from the voltage U and the current I, of the fuel cell stack 10, the pressures p in the anode and/or cathode chamber 12, 13, the charge state SOC of the energy storage unit 44, the rotational speed n of the traction motor 51, and other input variables. Alternatively, some of the aforementioned values, such as P.sub.stack, can also be determined in the control unit 60 itself.

[0070] Received by the control unit 60 are furthermore a selector lever position with respect to a selected operating mode (selected operation mode—SOM) as a first driver input, a driving performance P.sub.W requested by a driver of the vehicle 200 as a second driver input, a current temperature T as well as a temperature T.sub.sel, selected by the driver, of the vehicle interior space, and an outside temperature T.sub.env. The variable P.sub.W is detected via a pedal value sensor from the force used to operate an accelerator pedal not shown here.

[0071] Depending on the first driver input SOM, the control unit 60 determines an operating mode selected by the driver and varies the availability of the air-conditioning system 70 based on the selected operating mode by throttling the possible power consumption of the electric auxiliary heater 71 and the air-conditioning compressor 72 depending on the temperature outside the vehicle T.sub.env and thus indirectly sets an upper limit for the power consumption of the air-conditioning system P.sub.AC. Depending on the selected operating mode, the control unit 60 also determines a transfer function for determining the electrical power demand P.sub.EM of the electric motor 51 from the second driver input P.sub.W. The determined power demands P.sub.EM and P.sub.AC are superposed by the control unit 60 and transmitted to the fuel cell stack 10. The control unit 60 furthermore determines an operating point of the fuel cell stack 10 by specifying the electric voltage U demanded from the fuel cell stack 10 and the electric current 10 demanded from the fuel cell stack 10. The determination of the operating point can also include the superposing of an additional transfer function when the power demands P.sub.EM and P.sub.AC are superposed in order to, for example, delay the resulting power demand. From the resulting total power demand, the control unit 60 determines the required mass flows or operating pressures of the anode and cathode operating medium from calculations or appropriately stored characteristic diagrams and controls the operating medium supply of the fuel cell system, for example, via the electric motor 34 of the compressor 33, as well as the adjusting means 24, 38, etc. of the fuel cell system 100.

[0072] FIG. 3 shows a schematic representation of a power demand P.sub.EM, determined based on a pedal value P.sub.W, of an electric motor and the net power P.sub.net, provided as a result of the power demand, of a fuel cell stack, and the power consumption P.sub.aux, occurring during the provision of the net power, of at least one auxiliary unit.

[0073] As shown in FIG. 3(A), a transfer function for determining the electrical power demand P.sub.EM is selected in the first operating mode as a result of a first driver input in the form of an increase of the detected pedal value P.sub.W such that the fuel cell stack 10 provides a stack net power P.sub.net as a result of this power demand P.sub.EM, which stack net power corresponds to the increased pedal value P.sub.W, in particular to an electrical power required for providing a torque corresponding to the pedal value. The transfer function is also selected such that the power demand P.sub.EM increases slowly and the stack net power is thus provided with a certain, in particular non-minimal, delay. As a result of the delay, the maximum power consumption of the at least one auxiliary unit is reduced when providing this stack net power P.sub.net.

[0074] As shown in FIG. 3(B), a transfer function for determining the electrical power demand P.sub.EM is selected in the second operating mode as a result of a first driver input in the form of an increase of the detected pedal value P.sub.W such that the fuel cell stack 10 provides a stack net power P.sub.net as a result of this power demand P.sub.EM, which stack net power corresponds to the increased pedal value P.sub.W, in particular to an electrical power required for providing a torque corresponding to the pedal value, and a maximum power consumption P.sub.aux.sup.max to be expected of the at least one auxiliary unit. In the example shown in FIG. 3(B), P.sub.aux.sup.max corresponds to the maximum power consumption P.sub.aux to be expected when providing a stack net power P.sup.net, which corresponds to the increased pedal value P.sub.W, with a non-minimal delay as shown in FIG. 3(A).

[0075] Based on the power demand P.sub.EM, which is increased in comparison to the first operating mode, the full acceleration is available to the driver of the fuel cell vehicle in the second operating mode. In particular, a stack net power corresponding to the pedal value P.sub.W is already available at a point in time, when the available stack net power in the first operating mode is still reduced by about the maximum power consumption P.sub.aux.sup.max of the at least one auxiliary unit. The transfer function is also selected such that the power demand P.sub.EM increases slowly and the stack net power is thus provided with a certain, in particular non-minimal, delay. In particular, the power demand P.sub.EM reaches its maximum at the same time as in the first operating mode. As a result of the delay, the maximum power consumption of the at least one auxiliary unit is reduced when providing this stack net power P.sub.net.

[0076] As shown in FIG. 3(C), a transfer function for determining the electrical power demand P.sub.EM is also selected in the third operating mode as a result of a second driver input in the form of an increase of the detected pedal value P.sub.W such that the fuel cell stack 10 provides a stack net power P.sub.net as a result of this power demand P.sub.EM, which stack net power corresponds to the increased pedal value P.sub.W, in particular to an electrical power required for providing a torque corresponding to the pedal value, and a maximum power consumption P.sub.aux.sup.max to be expected of the at least one auxiliary unit. In the example shown in FIG. 3(C), P.sub.aux.sup.max also corresponds to the maximum power consumption P.sub.aux to be expected when providing a stack net power P.sup.net, which corresponds to the increased pedal value P.sub.W, with a non-minimal delay as shown in FIG. 3(A).

[0077] Based on the power demand P.sub.EM, which is increased in comparison to the first operating mode, and the smaller delay in comparison to the first and to the second operating mode when making the power demand P.sub.EM, the full acceleration with the full response behavior or with the full gas acceptance is available to the driver of the fuel cell vehicle in the third operating mode. In particular, a stack net power corresponding to the pedal value P.sub.W is already available at a substantially earlier point in time than in the first operating mode and also earlier than in the second operating mode. As a result of the minimal, exclusively technically required delay in the provision of power, the maximum power consumption P.sub.aux.sup.max of the at least one auxiliary unit is increased.

LIST OF REFERENCE SYMBOLS

[0078] 100 Fuel cell system

[0079] 200 Fuel cell vehicle

[0080] 10 Fuel cell stack

[0081] 11 Single cell

[0082] 12 Anode chamber

[0083] 13 Cathode chamber

[0084] 14 Polymer electrolyte membrane

[0085] 15 Bipolar plate

[0086] 20 Anode supply

[0087] 21 Anode supply path

[0088] 22 Anode exhaust path

[0089] 23 Fuel tank

[0090] 24 Adjusting means

[0091] 25 Fuel recirculation line

[0092] 26 Recirculation delivery device

[0093] 30 Cathode supply

[0094] 31 Cathode supply path

[0095] 32 Cathodxe exhaust path

[0096] 33 Compressor

[0097] 34 Electric motor

[0098] 35 Power electronics

[0099] 36 Turbine

[0100] 37 Wastegate line

[0101] 38 Adjusting means

[0102] 39 Humidifier module

[0103] 40 Electrical power system

[0104] 41 Voltage sensor

[0105] 42 Current sensor

[0106] 43 Inverter

[0107] 44 Energy storage unit

[0108] 45 DC converter

[0109] 50 Drive system

[0110] 51 Traction motor

[0111] 52 Drive axle

[0112] 53 Drive wheels

[0113] 60 Control unit

[0114] 70 Air-conditioning system

[0115] 71 Electric auxiliary heater

[0116] 72 Air-conditioning compressor