Exhaust gas control apparatus for internal combustion engine and method of controlling same

An exhaust gas control apparatus for an internal combustion engine, comprising:

• an exhaust gas purification catalyst device provided in an exhaust passage of the internal combustion engine;
• an HC adsorption portion, provided in the exhaust passage, which adsorbs hydrocarbon in exhaust gas;
• passage switching means for switching a passage through which the exhaust gas flows between a passage in which the HC absorption portion is provided, and a passage that bypasses the HC absorption portion, using a negative pressure in an intake pipe of the internal combustion engine;
• and
• intake pipe negative pressure control means for controlling the negative pressure in the intake pipe to operate the passage switching means by executing at least one of a timing advance control that advances a valve timing of an intake valve, and a control that reduces an opening amount of a throttle valve, at a time of start of the internal combustion engine,
• wherein when the rotational speed of the internal combustion engine is below a predetermined value, the intake pipe negative pressure control means sets the advance amount, by which the valve timing of the intake valve is advanced, to substantially zero, or a value smaller than a value to which the advance amount is set when the rotational speed of the internal combustion engine is equal to or above the predetermined value, and
• wherein the exhaust gas control apparatus includes means for cutting off fuel supply during a period from when operation of the passage switching means starts, until when the passage switching means completes switching of the passage through which the exhaust gas flows.