Fuel-cell electric vehicle

Abstract

When a fuel-cell electric vehicle is running at idle, and a predetermined period of time has elapsed since the vehicle comes into the idle state, forthcoming stopping of an operation of the vehicle is predicted, and the operation mode of a fuel cell is shifted to a residual water reduction mode in which residual water remaining inside the fuel cell is reduced. In the residual water reduction mode, for example, the amount of humidification for air to be supplied to the fuel cell is reduced, so that the air with reduced humidity passes through the fuel cell, to thereby increase the amount of residual water removed by the air. Accordingly, the residual water inside the fuel cell can be reduced before the actual stopping of the operation of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects, other advantages and further features of the present invention will become more apparent by describing in detail illustrative, non-limiting embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a general schematic diagram of a fuel-cell electric vehicle according to an exemplary embodiment of the present invention;

FIG. 2 is a flowchart of a process to be performed when a vehicle is running at idle;

FIG. 3 is a flowchart of a subordinate process performed in a residual water reducing mode of FIG. 2;

FIG. 4A is a graph showing a relationship between an amount of air humidification and a power output;

FIG. 4B is a graph showing a relationship between an amount of a cooling medium (coolant) and a power output;

FIG. 4C is a graph showing a relationship between a flow rate of air and a power output;

FIG. 4D is a graph showing a relationship between a pressure of air and a power output; and

FIG. 5 is a flowchart of an alternative process to be performed when a vehicle is running at idle.

Claims

1. A fuel-cell electric vehicle comprising: a fuel cell for generating electricity with a reactant gas supplied thereto;a vehicle idling detection unit configured to determine whether the vehicle is running at idle;an operation stopping prediction unit configured to predict forthcoming stopping of operation of the vehicle running at idle; anda residual water amount control unit configured to reduce residual water inside the fuel cell in response to a prediction of the forthcoming stopping of the operation of the vehicle made by the operation stopping prediction unit.

2. A fuel-cell electric vehicle according to claim 1 further comprising a humidifier for humidifying the reactant gas to be supplied to the fuel cell, wherein the residual water amount control unit comprises means for causing at least part of the reactant gas to be detoured around the humidifier in response to the prediction of the forthcoming stopping of the operation of the vehicle made by the operation stopping prediction unit, to lower a humidity of the reactant gas.

3. A fuel-cell electric vehicle according to claim 1 further comprising a cooling system with a coolant circulated to cool the fuel cell, wherein the residual water amount control unit comprises means for regulating a cooling performance of the cooling system, which is configured to reduce the cooling performance in response to the prediction of the forthcoming stopping of the operation of the vehicle made by the operation stopping prediction unit.

4. A fuel-cell electric vehicle according to claim 1 further comprising means for regulating a flow rate of the reactant gas to be supplied to the fuel cell, which is configured to increase the flow rate in response to the prediction of the forthcoming stopping of the operation of the vehicle made by the operation stopping prediction unit.

5. A fuel-cell electric vehicle according to claim 1 further comprising means for regulating a pressure of the reactant gas supplied to the fuel cell, which is configured to reduce the pressure of the reactant gas in response to the prediction of the forthcoming stopping of the operation of the vehicle made by the operation stopping prediction unit.

6. A fuel-cell electric vehicle according to claim 1, wherein the vehicle idling detection unit comprises a throttle sensor configured to output a throttle opening signal, wherein the vehicle idling detection unit determines that the vehicle is in an idle state if the throttle opening signal output from the throttle sensor indicates that a throttle is closed.

7. A fuel-cell electric vehicle according to claim 6, wherein the operation stopping prediction unit comprises a timer configured to measure an elapsed time from a time when the vehicle idling detection unit determines that the vehicle has come into an idle state, wherein the operation stopping prediction unit predicts the forthcoming stopping of the operation of the vehicle if the elapsed time measured by the timer is longer than a predetermined period of time.

8. A fuel-cell electric vehicle according to claim 6, wherein the operation stopping prediction unit comprises means for determining whether the vehicle is in one of neutral and parking gears, wherein the operation stopping prediction unit predicts the forthcoming stopping of the operation of the vehicle if the vehicle is in one of the neutral and parking gears.

9. A fuel-cell electric vehicle according to claim 1, wherein the operation stopping prediction unit comprises means for detecting a position of the vehicle, wherein the operation stopping prediction unit predicts the forthcoming stopping of the operation of the vehicle if the detected position of the vehicle is within an area where the vehicle frequently stops.

10. A fuel-cell electric vehicle according to claim 2, wherein the means for causing at least part of the reactant gas to be detoured around the humidifier comprises: a humidifier bypass line configured to divert the reactant gas from a fuel gas supply line at a joint located upstream thereof relative to the humidifier to conduct the reactant gas to the fuel cell while avoiding the humidifier; anda cross valve provided at the joint and regulated in such a way that the at least part of the reactant gas is detoured through the humidifier bypass if the forthcoming stopping of the operation of the vehicle is predicted by the operation stopping prediction unit.

11. A fuel-cell electric vehicle according to claim 3, wherein the means for regulating the cooling performance of the cooling system comprises: a radiator bypass line configured to divert the coolant from a coolant circulation line at a joint located upstream thereof relative to the radiator to conduct the coolant back to cool the fuel cell while avoiding the radiator; anda switching valve provided at the joint and regulated in such a way that at least part of the coolant is detoured through the radiator bypass if the forthcoming stopping of the operation of the vehicle is predicted by the operation stopping prediction unit.

12. A fuel-cell electric vehicle according to claim 3, wherein the cooling system comprises a circulating pump; and wherein the means for regulating the cooling performance of the cooling system comprises means for regulating the circulating pump, which is configured to reduce a rotation speed or stop rotation of the circulating pump if the forthcoming stopping of the operation of the vehicle is predicted by the operation stopping prediction unit.

13. A fuel-cell electric vehicle according to claim 4 further comprises a reactant gas compressor, wherein the means for regulating the flow rate of the reactant gas comprises means for regulating the reactant gas compressor, which is configured to increase a rotation speed of the reactant gas compressor if the forthcoming stopping of the operation of the vehicle is predicted by the operation stopping prediction unit.

14. A fuel-cell electric vehicle according to claim 5, wherein the means for regulating the pressure of the reactant gas comprises a back-pressure valve, which is configured to increase a throttle opening thereof if the forthcoming stopping of the operation of the vehicle is predicted by the operation stopping prediction unit.

15. A method for reducing residual water in a fuel cell before scavenging the residual water, wherein the fuel cell is installed in a fuel-cell electric vehicle to generate electricity with a reactant gas supplied thereto, the method comprising: determining whether the vehicle is running at idle;predicting forthcoming stopping of operation of the vehicle running at idle; andreducing residual water inside the fuel cell when the forthcoming stopping of the operation of the vehicle is predicted.

16. The method according to claim 15 wherein the reducing residual water inside the fuel cell comprises causing at least part of the reactant gas to be detoured around a humidifier for humidifying the reactant gas, to lower a humidity of the reactant gas to be supplied to the fuel cell.

17. The method according to claim 15 wherein the reducing residual water inside the fuel cell comprises reducing a cooling performance of a cooling system for the fuel cell.

18. The method according to claim 15 wherein the reducing residual water inside the fuel cell comprises increasing a flow rate of the reactant gas to be supplied to the fuel cell.

19. The method according to claim 15 wherein the reducing residual water inside the fuel cell comprises reducing a pressure of the reactant gas supplied to the fuel cell.

20. The method according to claim 15 wherein the determining whether the vehicle is running at idle comprises: receiving a throttle opening signal from a throttle sensor; anddetermining whether the received throttle opening signal indicates that a throttle is closed.

21. The method according to claim 20, wherein the predicting forthcoming stopping of the operation of the vehicle comprises: measuring an elapsed time from a time when it is determined that the throttle is closed, based upon the received throttle opening signal; anddetermining whether the measured elapsed time is longer than a predetermined period of time.

22. The method according to claim 15, wherein the predicting forthcoming stopping of the operation of the vehicle comprises determining whether the vehicle is in one of neutral and parking gears.

23. The method according to claim 15, wherein the predicting forthcoming stopping of the operation of the vehicle comprises: detecting a position of the vehicle; anddetermining whether the detected position of the vehicle is within an area where the vehicle frequently stops.