IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0339832
(2008-12-19)
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등록번호 |
US-8470486
(2013-06-25)
|
우선권정보 |
JP-2007-337249 (2007-12-27) |
발명자
/ 주소 |
- Sato, Masashi
- Maeshima, Susumu
- Saito, Kazuo
- Shimoi, Ryoichi
- Fujii, Takahiro
- Matsuba, Nobuo
- Igarashi, Hitoshi
- Yonekura, Kenji
|
출원인 / 주소 |
|
대리인 / 주소 |
Drinker Biddle & Reath LLP
|
인용정보 |
피인용 횟수 :
0 인용 특허 :
1 |
초록
▼
A fuel cell system has a plurality of fuel cells stacked in one or more groups of fuel cells. Each fuel cell includes a fuel electrode supplied with fuel gas at a fuel gas supply pressure, an oxidizing electrode supplied with oxidizing gas at an oxidizing gas supply pressure, and an electrolyte memb
A fuel cell system has a plurality of fuel cells stacked in one or more groups of fuel cells. Each fuel cell includes a fuel electrode supplied with fuel gas at a fuel gas supply pressure, an oxidizing electrode supplied with oxidizing gas at an oxidizing gas supply pressure, and an electrolyte membrane disposed between the fuel electrode and the oxidizing electrode. A pressure-difference control unit generates a pressure difference across the membrane such that the fuel gas supply pressure is greater than the oxidizing gas supply pressure in each fuel cell, a cell-voltage measuring device measures a cell voltage for each fuel cell or each group of fuel cells in the fuel cell stack, and a leakage determination unit determines the presence or absence of a leaking cell based on the behavior of the cell voltage of each fuel cell while the pressure difference is increased with time.
대표청구항
▼
1. A fuel cell system, comprising: a fuel cell stack in which a plurality of fuel cells are stacked in one or more groups of fuel cells, each fuel cell including a fuel electrode to which fuel gas containing hydrogen is supplied at a fuel gas supply pressure, an oxidizing electrode to which oxidizin
1. A fuel cell system, comprising: a fuel cell stack in which a plurality of fuel cells are stacked in one or more groups of fuel cells, each fuel cell including a fuel electrode to which fuel gas containing hydrogen is supplied at a fuel gas supply pressure, an oxidizing electrode to which oxidizing gas containing oxygen is supplied at an oxidizing gas supply pressure, and an electrolyte membrane disposed between the fuel electrode and the oxidizing electrode, the membrane having a fuel-electrode side and an oxidizing-electrode side;a pressure-difference control unit programmed to generate a pressure difference across the membrane between the fuel electrode and the oxidizing electrode in each fuel cell and for changing the pressure difference, the pressure difference being such that the pressure at the fuel electrode is higher than the pressure at the oxidizing electrode;a cell-voltage measuring device for measuring a cell voltage of each fuel cell or each group of fuel cells in the fuel cell stack; anda leakage determination unit programmed to determine the presence or absence of a leaking cell based on the behavior of the cell voltage of each fuel cell as measured by the cell-voltage measuring device while the pressure-difference control unit gradually increases the pressure difference with time, a leaking cell being a fuel cell in which gas flows through the electrolyte membrane from the fuel-electrode side to the oxidizing-electrode side,wherein the pressure-difference control unit is programmed to adjust one or both of the fuel gas supply pressure and the oxidizing gas supply pressure from a state in which the fuel gas pressure at a fuel electrode inlet is substantially equal to the oxidizing gas supply pressure at an oxidizing gas supply inlet to increase the pressure difference monotonically by reducing the oxidizing gas supply pressure to achieve a predetermined pressure difference, andwherein the leakage determination unit is programmed to monitor the cell voltage during the monotonic increase in pressure difference to determine the presence or absence of a leaking cell. 2. The fuel cell system according to claim 1, wherein the leakage determination unit determines that a leaking cell is present when the voltage of at least one fuel cell or group of fuel cells is less than a predetermined voltage threshold. 3. The fuel cell system according to claim 1, wherein the leakage determination unit determines that a leaking cell is present when a voltage difference of at least one fuel cell or group of fuel cells is greater than or equal to a predetermined voltage difference threshold, the voltage difference being the difference between the cell voltage and an average cell voltage measured by the cell-voltage measuring device while the pressure-difference control unit increases the pressure difference with time. 4. The fuel cell system according to claim 1, wherein the leakage determination unit is programmed to determine that a leaking cell is present when a voltage reduction rate difference of at least one fuel cell or group of fuel cells is equal to or greater than a predetermined voltage reduction rate threshold, the voltage reduction rate difference being the difference between the reduction rate of the cell voltage and the reduction rate of an average cell voltage measured by the cell-voltage measuring device while the pressure-difference control unit increases the pressure difference with time. 5. The fuel cell system according to claim 1, wherein the cell-voltage measuring device measures the cell voltage at a plurality of positions on a cell face of at least one fuel cell. 6. The fuel cell system according to claim 5, wherein each fuel cell includes an oxidizing-gas flow path having an outlet; andwherein the positions at which the cell-voltage measuring device measures the cell voltage include at least a position near the outlet of the oxidizing-gas flow path on the cell face. 7. The fuel cell system according to claim 5, wherein each fuel cell includes an oxidizing-gas flow path having an inlet, an outlet, and a bend forming a U-shape along the cell face, the inlet and the outlet being positioned at a first end of the cell face and the bend positioned at a second end of the cell face;wherein the positions at which the cell-voltage measuring device measures the cell voltage include at least one of a position near the outlet and the inlet of the oxidizing-gas flow path at the first end of the cell face; andwherein the positions at which the cell-voltage measuring device measures the cell voltage further include a position near the bend of the oxidizing-gas flow path at the second end of the cell face. 8. The fuel cell system according to claim 1, wherein the pressure-difference control unit generates the pressure difference and increases the pressure difference with time when the cell voltage measured by the cell-voltage measuring device is in an activation overvoltage region; andwherein the leakage determination unit determines the presence or absence of a leaking cell based on the behavior of the cell voltage in the activation overvoltage region. 9. The fuel cell system according to claim 8, the oxidizing gas being supplied at a normal oxidizing gas supply flow rate determined from a load current and an operating temperature of the fuel cell stack during normal operation of the fuel cell system, wherein the pressure-difference control unit generates the pressure difference and increases the pressure difference with time when the oxidizing gas supply flow rate is reduced to below the normal oxidizing gas supply flow rate. 10. The fuel cell system according to claim 8, the oxidizing gas being supplied at an oxidizing gas supply flow rate, wherein the pressure-difference control unit generates the pressure difference and increases the pressure difference with time when the oxidizing gas supply flow rate is stopped. 11. The fuel cell system according to claim 1, further comprising: an operation control unit for controlling the operation of the fuel cell system in accordance with the result of the determination performed by the leakage determination unit. 12. The fuel cell system according to claim 11, wherein the operation control unit is programmed to stop the operation of the fuel cell system if the leakage determination unit determines that a leaking cell is present. 13. The fuel cell system according to claim 11, wherein the operation control unit is programmed to determine, when the leakage determination unit determines that a leaking cell is present, whether or not the pressure difference is within an allowable pressure difference range permitted in normal operation. 14. The fuel cell system according to claim 13, wherein the operation control unit stops the operation of the fuel cell system if the pressure difference is within the allowable pressure difference range and continues the operation of the fuel cell system if the pressure difference is outside the allowable pressure difference range. 15. The fuel cell system according to claim 13, wherein when the pressure difference is within the allowable pressure difference range, the operation control unit updates the allowable pressure difference range to an updated allowable pressure range smaller than the pressure difference at the time of the determination that the leaking cell is present and continues the operation of the fuel cell system if the pressure difference is outside the updated allowable pressure difference range. 16. The fuel cell system according to claim 1, wherein the fuel gas is supplied at a fuel gas flow rate and the oxidizing gas is supplied at an oxidizing gas flow rate; andwherein the pressure-difference control unit is programmed to maintain for a predetermined time period the pressure difference at which the leaking cell was determined and to vary the fuel gas flow rate within a predetermined range when the leakage determination unit determines the presence of a suspected leaking cell, such that if the cell voltage of the suspected leaking cell varies during the predetermined time period then the suspected leaking cell is determined to be a leaking cell and if the cell voltage of the suspected leaking cell does not vary during the predetermined time period then the suspected leaking cell is determined not to be a leaking cell. 17. A fuel cell system, comprising: a fuel cell stack in which a plurality of fuel cells are stacked in one or more groups of fuel cells, each fuel cell including a fuel electrode to which fuel gas containing hydrogen is supplied at a fuel gas supply pressure, an oxidizing electrode to which oxidizing gas containing oxygen is supplied at an oxidizing gas supply pressure, and an electrolyte membrane disposed between the fuel electrode and the oxidizing electrode, the membrane having a fuel-electrode side and an oxidizing-electrode side;a pressure-difference control unit programmed to generate a pressure difference across the membrane between the fuel electrode and the oxidizing electrode in each fuel cell and for changing the pressure difference, the pressure difference being such that the pressure at the fuel electrode is higher than the pressure at the oxidizing electrode;a cell-voltage measuring device for measuring a cell voltage of each fuel cell or each group of fuel cells in the fuel cell stack; anda leakage determination unit programmed to determine the presence or absence of a leaking cell based on the behavior of the cell voltage of each fuel cell as measured by the cell-voltage measuring device while the pressure-difference control unit increases the pressure difference with time, a leaking cell being a fuel cell in which gas flows through the electrolyte membrane from the fuel-electrode side to the oxidizing-electrode side;wherein the pressure-difference control unit is configured to adjust one or both of the fuel gas supply pressure and the oxidizing gas supply pressure to achieve the pressure difference;wherein when the fuel gas supply pressure before the pressure difference is generated is equal to or greater than a predetermined fuel gas pressure threshold, the pressure-difference control unit generates the pressure difference and increases the pressure difference with time by reducing the oxidizing gas supply pressure; andwherein when the fuel gas supply pressure before the pressure difference is generated is less than the predetermined fuel gas pressure threshold, the pressure-difference control unit generates the pressure difference by increasing the fuel gas supply pressure. 18. A fuel-cell control apparatus, comprising: a fuel cell stack in which a plurality of fuel cells are stacked, each fuel cell including a fuel electrode, an oxidizing electrode, and a electrolyte membrane disposed between the fuel electrode and the oxidizing electrode, the fuel cell stack including fuel-gas supplying means which supplies fuel gas containing hydrogen to the fuel electrode of each fuel cell and oxidizing-gas supplying means which supplies oxidizing gas containing oxygen to the oxidizing electrode of each fuel cell;cell-voltage measuring means for measuring a cell voltage for each fuel cell or one or more groups of fuel cells;pressure-difference control means programmed to generate a pressure difference between the pressure of the fuel gas at the fuel electrode and the pressure of the oxidizing gas at the oxidizing electrode in each fuel cell and increasing the pressure difference with time, the pressure difference being such that a pressure at the fuel electrode is higher than a pressure at the oxidizing electrode; andleakage determination means for determining the presence or absence of a leaking cell in which gas flows through the electrolyte membrane from the fuel-electrode side to the oxidizing-electrode side, the leakage determination means determining the presence of absence of a leaking cell based on the behavior of the cell voltage measured by the cell-voltage measuring means while the pressure difference is gradually increased with time,wherein the pressure-difference control means is programmed to adjust one or both of the pressure of the fuel gas and the pressure of the oxidizing gas to achieve the pressure difference,wherein when the pressure of the fuel gas before the pressure difference is generated is equal to or greater than a predetermined fuel gas pressure threshold, the pressure-difference control means is programmed to generate the pressure difference and to increase the pressure difference with time by reducing the pressure of the oxidizing gas, andwherein when the pressure of the fuel gas before the pressure difference is generated is less than the predetermined fuel gas pressure threshold, the pressure-difference control means is programmed to generate the pressure difference by increasing the pressure of the fuel gas. 19. The fuel-cell control apparatus according to claim 18, wherein the leakage determination means determines that a leaking cell is present if the difference between the cell voltage of a fuel cell or group of fuel cells and an average cell voltage of the fuel cell stack becomes equal to or greater than a predetermined voltage difference threshold while the pressure difference is increased with time and an average cell voltage, or if the cell voltage of a fuel cell or group of fuel cells become less than or equal to a predetermined voltage threshold while the pressure difference is increased with time. 20. The fuel-cell control apparatus according to claim 19, further comprising an operation control means for controlling the operation of the fuel cell system, wherein when the leakage determination means determines that a leaking cell is present, the operation control means determines whether or not the pressure difference at the time of the determination that a leaking cell is present is within an allowable pressure difference range permitted in normal operation; andwherein the operation control means stops the operation of the fuel cell system if the pressure difference at the time of the determination that the leaking cell is present is within the allowable pressure difference range and continues the operation of the fuel cell system if the pressure difference at the time of the determination that the leaking cell is present is outside the allowable pressure difference range.
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