Oliff & Berridge PLC.
Exhaust gas recirculation mechanism for engine and method for controlling exhaust gas recirculation valve
 An exhaust gas recirculation mechanism of an engine. Some of exhaust gas discharged from combustion chambers is recirculated to the combustion chambers through an EGR passage. An EGR valve is located in the EGR passage for adjusting the amount of recirculated exhaust gas. Foreign matter contained in exhaust gas in the EGR passage adheres to a valve shaft of the EGR valve that is exposed in the EGR passage. Normally, the opening amount of the EGR valve is controlled in accordance with the running state of the engine. If the opening amount of the EGR valve, which is determined based on the running state of the engine, is greater than a predetermined value, an ECU judges that the EGR ratio will fall within an acceptable range even if the EGR valve is fully opened from the current position. The ECU therefore forces the EGR valve to open fully. As a result, the foreign matter adhered to the valve shaft is removed without deteriorating the running condition of the engine. 
Toyota Jidosha Kabushiki Kaisha
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inventional additional additional inventional additional
Jun Hiroyuki Hironao
Takahashi Mizuno Kishi