Fuel cell system with humidity determination

• US 6,524,733 B1
• Filed: 02/23/2000
• Issued: 02/25/2003
• Est. Priority Date: 02/23/1999
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Nonobe, Yasuhiro
• Primary Examiner(s): Kalafut, Stephen
• Assistant Examiner(s): Martin, Angela J
• Application Number:
  US09/511,926
• Time in Patent Office: 1,098 Days
• Field of Search: 429/7, 429/12, 429/17, 429/22, 429/23, 429/30, 429/38
• US Class Current: 429/413
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/0258 characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
• CPC Class Codes: H01M 8/0267 having heating or cooling means, e.g. heaters or coolant flow channels
• CPC Class Codes: H01M 8/04119 with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• CPC Class Codes: H01M 8/04126 Humidifying
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04291 Arrangements for managing water in solid electrolyte fuel cell systems H01M8/04119 takes precedence
• CPC Class Codes: H01M 8/241 with solid or matrix-supported electrolytes
• CPC Class Codes: H01M 8/2457 with both reactants being gaseous or vaporised
• CPC Class Codes: H01M 8/2483 characterised by internal manifolds
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

In a polymer electrolyte fuel cell system, a condition of humidification of electrolyte membranes is precisely determined, and adjustment is performed so that the condition of humidification of the electrolyte membranes substantially remains within a proper range. The system determines a condition of humidification of the electrolyte membranes of the fuel cell based on a differential value of the resistance of the fuel cell detected by a resistance detector when the electric current outputted by the fuel cell equals a predetermined value. The current from the cell is detected by an ammeter. The fuel cell is formed by stacking electrically conductive electrodes and separators, and proton-conductive electrolyte membranes. The electric conductivity of the electrodes and the separators is not affected by the humidification condition thereof, whereas the proton-conductivity of the electrolyte membranes greatly changes depending on the condition of humidification thereof. Therefore, the changing rate of the resistance of the fuel cell directly represents the changing rate of the proton-conductivity of the electrolyte membranes, so that the humidification condition of the electrolyte membranes can be precisely determined.

Claims

1. A fuel cell system comprising:

a polymer electrolyte type fuel cell formed by stacking unit cells, each of which has an electrolyte membrane sandwiched by two electrodes;

a fuel gas supply device connected to the fuel cell;

a fuel gas humidifier;

a fuel cell output electric current detector;

a fuel cell resistance detector; and

a humidification condition determiner that determines a condition of humidification of the electrolyte membranes based on the current detected by the current detector and the resistance detected by the resistance detector, wherein the humidification condition determiner determines a condition of humidification of the electrolyte membranes based on an over-time change in the resistance detected by the resistance detector when the current detected by the current detector is equal to a predetermined value.

2. A fuel cell system according to claim 1, wherein if the over-time change in the resistance is equal to or less than a first predetermined value, the humidification condition determiner determines that the electrolyte membranes are insufficiently humidified, and wherein if the over-time change in the resistance is equal to or greater than a second predetermined value that is greater than the first predetermined value, the humidification condition determiner determines that the electrolyte membranes are excessively humidified.

3. A fuel cell system comprising:

a polymer electrolyte type fuel cell formed by stacking unit cells, each of which has an electrolyte membrane sandwiched by two electrodes;

a fuel gas supply device connected to the fuel cell;

a fuel gas humidifier;

a fuel cell output electric current detector;

a fuel cell resistance detector; and

a humidification condition determiner that determines a condition of humidification of the electrolyte membranes based on the current detected by the current detector and the resistance detected by the resistance detector, further comprising a humidification controller that controls humidification in the fuel gas caused by the fuel gas humidifier, based on determination made by the humidification condition determiner.

4. A fuel cell system according to claim 3, wherein the humidification controller increases the humidification in the fuel gas if the humidification condition determiner determines that the electrolyte membranes are insufficiently humidified.

5. A fuel cell system according to claim 3, wherein the humidification controller increases a pressure of the fuel gas in the fuel cell if the humidification condition determiner determines that the electrolyte membranes are insufficiently humidified.

6. A fuel cell system according to claim 3, wherein the humidification controller decreases an operating temperature of the fuel cell if the humidification condition determiner determines that the electrolyte membranes are insufficiently humidified.

7. A fuel cell system according to claim 3, wherein the humidification controller decreases an amount of the fuel gas supplied by the fuel gas supplier if the humidification condition determiner determines that the electrolyte membranes are insufficiently humidified.

8. A fuel cell system according to claim 3, wherein the humidification controller decreases the humidification in the fuel gas if the humidification condition determiner determines that the electrolyte membranes are excessively humidified.

9. A fuel cell system according to claim 3, wherein the humidification controller decreases a pressure of the fuel gas in the fuel cell if the humidification condition determiner determines that the electrolyte membranes are excessively humidified.

10. A fuel cell system according to claim 3, wherein the humidification controller increases an operating temperature of the fuel cell if the humidification condition determiner determines that the electrolyte membranes are excessively humidified.

11. A fuel cell system according to claim 3, wherein the humidification controller increases an amount of the fuel gas supplied by the fuel gas supplier if the humidification condition determiner determines that the electrolyte membranes are excessively humidified.

12. A fuel cell system according to claim 3, further comprising an abnormality detector that detects an abnormality of the fuel cell system when the determination made by the humidification condition determiner remains unchanged after control by the humidification controller has been performed for a predetermined amount of time.

13. A fuel cell system according to claim 12, further comprising a detected abnormality information outputter.

14. A fuel cell system according to claim 12, further comprising a device that stops an operation of the fuel cell system when the abnormality detector detects the abnormality.