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Fuel cell system and gas control methodRelated Patent Categories: Chemistry: Electrical Current Producing Apparatus, Product, And Process, Fuel Cell, Subcombination Thereof Or Methods Of Operating, Automatic Control MeansFuel cell system and gas control method description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060210849, Fuel cell system and gas control method. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a fuel cell system that generates electricity through an electrochemical reaction between fuel gas and oxidizing gas and a gas control method of the fuel cell system. [0003] 2. Description of the Related Art [0004] A fuel cell is structured to start power generation upon supply of the fuel gas and the oxidizing gas. The fuel cell generates required electric energy in response to the supply of the fuel gas and the oxidizing gas by quantity each corresponding to a required load. [0005] The operation of the aforementioned fuel cell is interrupted by stopping the supply of the fuel gas and the oxidizing gas. For example, the power generation may be completely stopped by introducing inactive gas into the fuel cell (pressurizing) or sucking the residual fuel gas outside (generating negative pressure) so as to be discharged outside. [0006] Meanwhile in the case where the vehicle equipped with the fuel cell is stopped for a short period of time or operated under low loads, the supply of the fuel gas and the oxidizing gas is stopped while having the fuel gas and the like remained in the fuel cell. [0007] In the fuel cell, the fuel gas is separated from the oxidizing gas with a polymer electrolyte. If such gas is left in the state where the power generation (electrochemical reaction) is interrupted, the gas is likely to permeate through the polymer electrolyte until partial pressure of each gas at both electrodes becomes equal. The above-described permeation of the gas through the polymer electrolyte may interfere with normal power generation, resulting in a temporal deterioration in the performance of the fuel cell (output voltage) upon re-start of the power generation. [0008] Japanese patent application Publication No. JP-A-2002-352837 discloses a fuel cell system that swiftly supplies excessive fuel gas into the fuel cell under pressure applied upon activation such that power output is obtained quickly from the stopped state of the fuel cell. [0009] In the case where the power generation (electrochemical reaction) has been stopped, the fuel gas and the oxidizing gas both separated by the polymer electrolyte in the fuel cell tend to permeate therethrough until the partial pressures at both electrodes become equal. The above-described permeation of such gas may interfere with normal power generation, thus temporarily deteriorating the performance (output voltage) of the fuel cell upon re-start thereof. If the excessive gas under high pressure is swiftly supplied into the fuel cell repeatedly at every re-start of the fuel cell as aforementioned, a very thin solid polymer electrolyte or catalytic electrode may be damaged and the fuel gas is wasted, thus deteriorating the fuel efficiency. SUMMARY OF THE INVENTION [0010] It is an object of the invention to provide a fuel cell that overcomes the problem of the deterioration in its performance upon re-start of power generation while avoiding deterioration in the fuel efficiency. [0011] First aspect of the invention relates to a fuel cell system provided with a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidizing gas, and a load device which is supplied with electric power from the fuel cell, the fuel cell system includes a gas supply unit that supplies each of the fuel gas and the oxidizing gas to an anode and a cathode of the fuel cell, respectively by quantity corresponding to a load; a gas permeation quantity estimation unit that estimates a gas permeation quantity of at least one of the fuel gas and the oxidizing gas between the anode and the cathode after the power generation performed by the fuel cell is stopped; and a correction unit that corrects a supply quantity of at least one of the fuel gas and the oxidizing gas each corresponding to the load in accordance with the estimated gas permeation quantity, which is to be supplied by the gas supply unit upon a subsequent start of power generation. [0012] According to the first aspect of the invention, the above-described structure makes it possible to overcome reduction in the effective catalytic area owing to formation of water drop on the catalytic surface resulting from chemical short-circuit caused by the residual gas in the fuel cell that permeates through the polymer electrolyte between the anode and the cathode after interruption of the fuel cell operation, or the delay in the rise of the fuel cell upon re-start thereof owing to reduction in the gas pressure in the anode and the cathode. [0013] In the first aspect of the invention, the gas permeation quantity may be estimated based on a drop rate of an open circuit voltage after the power generation performed by the fuel cell is stopped. Such estimation may be made using the correlation between the reduction rate in the open circuit voltage and the gas permeation quantity through the polymer electrolyte at a predetermined elapse of time after interruption of the fuel cell operation. [0014] In the aspect related to the first aspect of the invention, the drop rate of the open circuit voltage may be calculated based on an amount of a voltage drop that has occurred between the anode and the cathode due to a leakage of the fuel gas to the cathode and a leakage of the oxidizing gas to the anode after the power generation performed by the fuel cell is stopped, an elapsed time from when the power generation performed by the fuel cell is stopped, and a function which has been obtained through experiment or simulation calculation preliminarily. [0015] In the first aspect of the invention, the gas permeation quantity may be estimated based on a gas pressure decrease rate in the fuel gas after the power generation performed by the fuel cell is stopped. Such estimation may be made using the correlation between the reduction rate in gas pressure within the fuel cell and the gas permeation quantity through the polymer electrolyte at a predetermined elapse of time after interruption of the fuel cell operation. [0016] In the aspect related to the first aspect of the invention, the gas pressure decrease rate may be calculated based on the estimated gas permeation quantity which has been obtained through experiment or simulation calculation preliminarily based on a fuel gas pressure in the anode after the power generation performed by the fuel cell is stopped, a decrease in the fuel gas pressure for an elapsed time from when the power generation performed by the fuel cell is stopped until when the power generation performed by the fuel cell is restarted, and the elapsed time. [0017] In the first aspect of the invention, the correction unit independently may set each of a correction amount of the fuel gas and a correction amount of the oxidizing gas based on the estimated gas permeation quantity. [0018] In the first aspect of the invention, the gas permeation quantity estimation unit independently may estimate each of the gas permeation quantity of the fuel gas and the gas permeation quantity of the oxidizing gas. [0019] According to the first aspect and related aspect of the invention, the fuel cell may be brought into a stopped state in an intermittent operation mode of the fuel cell. The fuel cell provided in the vehicle is structured to supply electricity from a secondary battery in the low load state such as a vehicle stopped state for improving the fuel efficiency such that the fuel cell is briefly stopped until its operation is needed. The fuel cell has to be started quickly as higher electric energy is required to allow the vehicle to take off. According to the aspect of the invention, the deterioration in the start-up characteristic of the fuel cell caused by permeation of the gas may be avoided by correcting the quantity of the supplied gas, thus improving the take-off characteristic of the vehicle. [0020] Second aspect of the invention relates to a gas control method of a fuel cell system including a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidizing gas, and a load device which is supplied with electric power from the fuel cell, the method includes the steps of: supplying each of the fuel gas and the oxidizing gas to an anode and a cathode of the fuel cell, respectively by quantity corresponding to a load; estimating a gas permeation quantity of at least one of the fuel gas and the oxidizing gas between the anode and the cathode after the power generation performed by the fuel cell is stopped; and correcting a supply quantity of at least one of the fuel gas and the oxidizing gas corresponding to the load in accordance with the estimated gas permeation quantity, which is to be supplied upon a subsequent start of power generation. [0021] The invention makes it possible to avoid drop in the output voltage immediately after re-start of the fuel cell. The quantity of the gas supplied upon re-start of the fuel cell is adjusted (corrected) to an appropriate value so as to improve the rise-up characteristic of the output voltage. Accordingly this makes it possible to avoid damage in the solid polymer electrolyte under the excessive pressure or the deterioration in the fuel efficiency upon excessive supply of the fuel gas. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Fuel cell system and gas control method... Full patent description for Fuel cell system and gas control method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Fuel cell system and gas control method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Fuel cell system and gas control method or other areas of interest. ### Previous Patent Application: Reformer fuel cell system with external burner Next Patent Application: Method, system and apparatus for diagnostic testing of an electrochemical cell stack Industry Class: Chemistry: electrical current producing apparatus, product, and process ### FreshPatents.com Support Thank you for viewing the Fuel cell system and gas control method patent info. IP-related news and info Results in 0.12859 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf 174 |
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