Air Fuel Ratio Controle Metod | US007484504B2 12 United States Patent Kato et al. io Patent No. US 7 484 504 B2 45 Date of Patent Feb. 3 2009 54 AIR-FUEL RATIO CONTROL SYSTEM AND METHOD FOR INTERNAL COMBUSTION ENGINE 75 Inventors Naoto Kato Susono JP Shuntaro Okazaki Susono JP 73 Assignee Toyota Jidosha Kabushiki Kaisha Toyota-shi JP Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 . 154 b by 0 days. 21 Appl. No. 11 858 283 22 Filed Sep. 20 2007 65 Prior Publication Data US 2008 0066727 Al Mar. 20 2008 30 Foreign Application Priority Data Sep. 20 2006 JP . 2006-253936 51 Int. Cl. F02D 41 00 B60T7 12 52 . Cl 123 672 123 674 701 103 701 108 60 277 58 Field of Classification Search . 123 434 123 672 703 674 696 701 103 104 108 701 113 60 277 285 289 See application file for complete search history. 56 References Cited . PATENT DOCUMENTS 7 117 665 B2 10 2006 Kamoto et al. 60 277 2002 0007627 Al 1 2002 Hashimoto . 60 277 2003 0154953 Al 8 2003 Yasui . 123 205 2004 0045282 Al 3 2004 Ide et al. 60 285 2005 0217243 Al 10 2005 Kamoto et al. 60 277 2006 0282211 Al 12 2006 Yasui . 701 103 FOREIGN PATENT DOCUMENTS JP 2003-049685 A 2 2003 JP 2005-113729 A 4 2005 cited by examiner Primary Examiner John T Kwon 74 Attorney Agent or Firm Sughrue Mion PLLC 57 ABSTRACT An air-fuel ratio control system includes a catalyst an oxygen concentration sensor an integral value calculation portion that calculates an integral value of a deviation updated by integrating the deviation between an output value from the oxygen concentration sensor and a reference value an airfuel ratio control portion that controls an air-fuel ratio of exhaust gas entering the catalyst to be equal to a target air-fuel ratio a target air-fuel ratio switching portion that sets a rich target air-fuel ratio when the output value has been inverted from rich to lean while sets a lean target air-fuel ratio when the output value has been inverted from lean to rich and an integral value .
