# US 9,520,606 B2 · Fuel cell system and control method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,606 B2 - Document ID: US9520606B2 - Status: Granted - Kind: B2 - Application number: 13/477,350 - Filed: 2012-05-22 - Published: 2012-11-29 - Granted: 2016-12-13 - Earliest claimed: 2011-05-24 - Assignees: Honda Motor Co., Ltd. - Applicants: Chihiro Wake; Yuji Matsumoto - Inventors: Chihiro Wake; Yuji Matsumoto - Web page: https://patentgrep.com/patent/US9520606B2 ## CPC - H01M 8/0488: {of fuel cell stacks} - B60L 1/003: {to auxiliary motors, e.g. for pumps, compressors} - B60L 7/14: for vehicles propelled by AC motors - B60L 15/2009: {for braking} - B60L 50/40: using propulsion power supplied by capacitors - B60L 50/51: characterised by AC-motors - B60L 50/72: Constructional details of fuel cells specially adapted for electric vehicles - B60L 58/20: having different nominal voltages - B60L 58/40: for controlling a combination of batteries and fuel cells - H01M 8/04559: {of fuel cell stacks} - H01M 8/04753: {of fuel cell reactants} - H01M 8/0491: {of fuel cell stacks} - H01M 8/04955: Shut-off or shut-down of fuel cells - B60L 2210/10: DC to DC converters - B60L 2240/421: Speed - B60L 2240/423: Torque - B60L 2240/547: Voltage - B60L 2240/549: Current - H01M 2008/1095: {Fuel cells with polymeric electrolytes} - H01M 2250/20: Fuel cells in motive systems, e.g. vehicle, ship, plane - Y02E 60/50: Fuel cells - Y02T 10/64: Electric machine technologies in electromobility - Y02T 10/70: Energy storage systems for electromobility, e.g. batteries - Y02T 10/72: Electric energy management in electromobility - Y02T 90/40: Application of hydrogen technology to transportation, e.g. using fuel cells - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A fuel cell system includes an ECU that sets the fuel cell stack to a state of idling stop by lowering both a revolution speed of an air pump and a discharge current value of the fuel cell stack to less than during idling power generation within a range larger than 0, in response to a predetermined idling stop initiation condition having been satisfied during idling power generation. The ECU decreases the discharge current value further as the lowest cell voltage value CV_low of the fuel cell stack decreases so that the lowest cell voltage value CV_low does not fall below a cancellation threshold B, with an event of the lowest cell voltage CV_low of the fuel cell stack having fallen below the cancellation threshold B as a cancellation condition of idling stop. ## Claims ### Claim 1 A fuel cell system comprising: a fuel cell stack having stacked together a plurality of fuel cells that generate power when supplied fuel gas and oxidant gas; an electrical load that is connected to the fuel cell stack and consumes electric power generated by the fuel cell stack; and a control unit that executes low stoichiometry control to decrease a supplied amount of oxidant gas to the fuel cell stack within a range greater than zero and less than during idling power generation, and decrease a generated electric current produced from the fuel cell stack within a range greater than zero and less than during the idling power generation, wherein the control unit causes generated electric current produced from the fuel stack to change so that the lowest cell voltage value of the fuel cell stack does not fall below a predetermined threshold, and decreases the generated electric current as a lowest cell voltage value of the fuel cell stack decreases, during execution of the low stoichiometry control. ### Claim 2 (depends on 1) The fuel cell system according to claim 1, wherein the control unit acquires a difference between a lowest cell voltage value of the fuel cell stack and the threshold, and decreases the generated electric current produced from the fuel cell stack as the difference decreases, so that the lowest cell voltage value of the fuel cell stack does not fall below the threshold, during execution of the low stoichiometry control. ### Claim 3 (depends on 2) The fuel cell system according to claim 2, wherein the control unit maintains a supplied amount of oxidant gas to the fuel cell stack to be constant, during execution of the low stoichiometry control. ### Claim 4 (depends on 3) The fuel cell system according to claim 3, wherein the control unit executes the low stoichiometry control in response to a predetermined idling stop initiation condition having been satisfied during idling power generation, with an event of the lowest cell voltage value of the fuel cell stack having fallen below the threshold as a cancellation condition for the low stoichiometry control. ### Claim 5 (depends on 1) The fuel cell system according to claim 1, wherein the control unit maintains a supplied amount of oxidant gas to the fuel cell stack to be constant, during execution of the low stoichiometry control. ### Claim 6 (depends on 1) The fuel cell system according to claim 1, wherein the control unit executes the low stoichiometry control in response to a predetermined idling stop initiation condition having been satisfied during idling power generation, with an event of the lowest cell voltage value of the fuel cell stack having fallen below the threshold as a cancellation condition for the low stoichiometry control. ### Claim 7 A method for controlling a fuel cell system including a fuel cell stack having stacked together a plurality of fuel cells that generate power when fuel gas and oxidant gas are supplied thereto, and an electrical load that is connected to the fuel cell stack, and consumes electric power generated by the fuel cell stack, the method comprising: an idling power generation step of producing a predetermined amount of a generated electric current while supplying a predetermined amount of oxidant gas to the fuel cell stack; and a low stoichiometry control step of decreasing a supplied amount of the oxidant gas to the fuel cell stack within a range greater than zero and less than during the idling power generation on step, and decreasing the generated electric current produced from the fuel cell stack within a range greater than zero and less than during the idling power generation step, wherein the generated electric current produced from the fuel cell stack is made to change so that the lowest cell voltage value of the fuel cell stack does not fall below a predetermined threshold, and the generated electric current is lowered as a lowest cell voltage value of the fuel cell stack decreases, in the low stoichiometry control step. ### Claim 8 (depends on 7) The method for controlling a fuel cell system according to claim 7, wherein a difference between a lowest cell voltage value of the fuel cell stack and the threshold is acquired, and the generated electric current produced from the fuel cell stack is decreased as the difference decreases, so that the lowest cell voltage value of the fuel cell stack does not fall below the threshold, in the low stoichiometry control step. ### Claim 9 (depends on 8) The method for controlling a fuel cell system according to claim 8, wherein the supplied amount of the oxidant gas to the fuel cell stack is maintained to be constant in the low stoichiometry control step. ### Claim 10 (depends on 9) The method for controlling a fuel cell system according to claim 9, wherein the low stoichiometry control step is executed in response to a predetermined idling stop initiation condition having been satisfied during the idling power generation step, with an event of the lowest cell voltage value of the fuel cell stack having fallen below the threshold as a cancellation condition for the low stoichiometry control step. ### Claim 11 (depends on 7) The method for controlling a fuel cell system according to claim 7, wherein the supplied amount of the oxidant gas to the fuel cell stack is maintained to be constant in the low stoichiometry control step. ### Claim 12 (depends on 7) The method for controlling a fuel cell system according to claim 7, wherein the low stoichiometry control step is executed in response to a predetermined idling stop initiation condition having been satisfied during the idling power generation step, with an event of the lowest cell voltage value of the fuel cell stack having fallen below the threshold as a cancellation condition for the low stoichiometry control step.